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SS521-AG-PRO-010
0910-LP-115-1921

REVISION 7

U.S. Navy Diving Manual

Volume 1:

Diving Principles and
Policies

Volume 2:

Air Diving Operations

Volume 3:

Mixed Gas Surface
Supplied Diving
Operations

Volume 4:

Closed-Circuit and
Semiclosed Circuit
Diving Operations

Volume 5:

Diving Medicine
and Recompression
Chamber Operations

DISTRIBUTION STATEMENT A: THIS DOCUMENT HAS BEEN APPROVED FOR PUBLIC RELEASE AND
SALE; ITS DISTRIBUTION IS UNLIMITED.

SUPERSEDES SS521-AG-PRO-010, REVISION 6 CHANGE A, Dated 15 October 2011.

PUBLISHED BY DIRECTION OF COMMANDER, NAVAL SEA SYSTEMS COMMAND

01 DECEMBER 2016

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For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402

SS521-AG-PRO-010

LIST OF EFFECTIVE PAGES
Date of issue for original is:
Original . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .01 December 2016
TOTAL NUMBER OF PAGES IN THIS PUBLICATION IS 992, CONSISTING OF THE
FOLLOWING:

Page No.

*Change No.

Title Page . . . . . . . . . . . . . . . . . . . . . . . .
List of Effective Pages . . . . . . . . . . . . . .
Certification Sheet . . . . . . . . . . . . . . . . .
Record of Changes. . . . . . . . . . . . . . . . .
Foreword . . . . . . . . . . . . . . . . . . . . . . . .
Prologue . . . . . . . . . . . . . . . . . . . . . . . . .
Chapter 1 . . . . . . . . . . . . . . . . . . . . . . . .
Chapter 2 . . . . . . . . . . . . . . . . . . . . . . . .
Chapter 3 . . . . . . . . . . . . . . . . . . . . . . . .
Chapter 4 . . . . . . . . . . . . . . . . . . . . . . . .
Chapter 5 . . . . . . . . . . . . . . . . . . . . . . . .
Chapter 6 . . . . . . . . . . . . . . . . . . . . . . . .
Chapter 7 . . . . . . . . . . . . . . . . . . . . . . . .
Chapter 8 . . . . . . . . . . . . . . . . . . . . . . . .
Chapter 9 . . . . . . . . . . . . . . . . . . . . . . . .
Chapter 10 . . . . . . . . . . . . . . . . . . . . . . .
Chapter 11 . . . . . . . . . . . . . . . . . . . . . . .
Chapter 12 . . . . . . . . . . . . . . . . . . . . . . .
Chapter 13 . . . . . . . . . . . . . . . . . . . . . . .
Chapter 14 . . . . . . . . . . . . . . . . . . . . . . .
Chapter 15 . . . . . . . . . . . . . . . . . . . . . . .
Chapter 16 . . . . . . . . . . . . . . . . . . . . . . .
Chapter 17 . . . . . . . . . . . . . . . . . . . . . . .
Chapter 18 . . . . . . . . . . . . . . . . . . . . . . .

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U.S. Navy Diving Manual

Safety Summary
STANDARD NAVY SYNTAX

Since this manual will form the technical basis of many subsequent instructions or directives,
it utilizes the standard Navy syntax as pertains to permissive, advisory, and mandatory
language. This is done to facilitate the use of the information provided herein as a reference
for issuing Fleet Directives. The concept of word usage and intended meaning that has been
adhered to in preparing this manual is as follows:
“Shall” has been used only when application of a procedure is mandatory.
“Should” has been used only when application of a procedure is recommended.
“May” and “need not” have been used only when application of a procedure is discretionary.
“Will” has been used only to indicate futurity; never to indicate any decree of requirement for
application of a procedure.
Throughout the manual “appropriate” has been used in regard to recompression chamber
identification, location, and selection. In these situations, “appropriate” means a chamber
meeting the demands and risks associated with a dive or series of dives.
The usage of other words has been checked against other standard nautical and naval
terminology references.
GENERAL SAFETY

This Safety Summary contains all specific WARNINGS and CAUTIONS appearing elsewhere
in this manual and are referenced by page number. Should situations arise that are not covered
by the general and specific safety precautions, the Commanding Officer or other authority will
issue orders, as deemed necessary, to cover the situation.
SAFETY GUIDELINES

Extensive guidance for safety can be found in the OPNAV 5100 series instruction manual,
Navy Safety Precautions.
SAFETY PRECAUTIONS

The WARNINGS, CAUTIONS, and NOTES contained in this manual are defined as follows:
WARNING

Voluntary hyperventilation is dangerous and can lead to unconsciousness
and death during breathhold dives. (Page 3-20)

WARNING

Never do a forceful Valsalva maneuver during descent. A forceful Valsalva
maneuver can result in alternobaric vertigo or barotrauma to the inner
ear (see below). (Page 3-25)

WARNING

If decongestants must be used, check with medical personnel trained
in diving medicine to obtain medication that will not cause drowsiness

Safety Summary

I

and possibly add to symptoms caused by the narcotic effect of nitrogen.
(Page 3-25)
CAUTION

When in doubt, always recompress. (Page 3-30)

WARNING

Reducing the oxygen partial pressure does not instantaneously reverse
the biochemical changes in the central nervous system caused by high
oxygen partial pressures. If one of the early symptoms of oxygen toxicity
occurs, the diver may still convulse up to a minute or two after being
removed from the high oxygen breathing gas. One should not assume
that an oxygen convulsion will not occur unless the diver has been off
oxygen for 2 or 3 minutes. (Page 3-45)

CAUTION

Do not institute active rewarming with severe cases of hypothermia (Page
3-55).

WARNING

CPR should not be initiated on a severely hypothermic diver unless it can
be determined that the heart has stopped or is in ventricular fibrillation.
CPR should not be initiated in a patient that is breathing. (Page 3-55)

NOTE

For OEM technical manuals that are found to be deficient, contact
NAVSEA 00C3 for guidance. (Page 4-2)

NOTE

Only white virgin Teflon tape that is made in accordance with MILSPEC
A-A 58093 is authorized for use on Navy Dive Life Support Systems
(DLSS). (Page 4-3, 4-14)

NOTE

Only use properly mixed Non Ionic Detergent (NID) to clean exterior
DLSS. Do not flood console case or gauges with water and cleaner. (Page
4-3)

NOTE:

A compressor log shall be maintained with the compressor at all times.
It shall record date, start/stop hour-meter readings, corrective/preventive
maintenance accomplished, the component the compressor is charging,
pressures not within parameters. (Page 4-6)

NOTE

The most recent air sample analysis report shall be maintained on file
for each air compressor (by compressor serial number) used to produce
diver’s breathing air. (Page 4-9)

NOTE

Failure to purge the system of air produced from other compressors or
storage flasks will lead to an invalid air sample for the compressor being
sampled. (Page 4-11)

WARNING

NOTE

J

Do not use a malfunctioning compressor to pump diver’s breathing air or
charge diver’s air storage flasks as this may result in contamination of
the diver’s air supply. (Page 4-12)
All valves and electrical switches that directly influence the air supply
shall be labeled: “DIVER’S AIR SUPPLY - DO NOT TOUCH” Banks of
flasks and groups of valves require only one central label at the main
stop valve. (Page 4-14)
U.S. Navy Diving Manual

NOTE

Do not use commercial cleaning products/agents, only utilize properly
mixed Non Ionic Detergent (NID) to clean exterior of Navy Diving Life
Support Systems. Do not flood console case or the gauges with water
and cleaner. (Page 4-14)

NOTE

In the interest of creating and maintaining a learning organization, to
the greatest extent possible, the reporting of safety issues or concerns
shall be handled so that persons reporting or individuals involved in the
reported event are not subject to punishment or censure. (Page 5-5)

NOTE

NOTIFY NAVSEA at 00C3@supsalv.org and 00C3B@supsalv.org or
(202) 781-1731 (available 24hrs) with non-privileged information of any
reportable mishap as soon as possible. Immediate contact may prevent
loss of evidence vital to the evaluation of the equipment or prevent
unnecessary shipment of equipment to NEDU. (Page 5-5)

NOTE

Do not tamper with equipment without first contacting NAVSEA/00C3
forguidance. (Page 5-8)

NOTE

If the type of sonar is unknown, start diving at 600–3,000 yards, depending
on diving equipment (use greater distance if helmeted), and move in to
limits of diver comfort. (Page 1A-3)

NOTE

If range is between two values in the table, use the shorter range.
This will insure that the SPL is not underestimated and that the PEL is
conservative. (Page 1A-5)

NOTE

Use DT1/PEL1 for the first sonar, DT1/PEL2 for the second sonar, up to
the total number of sonars in use. Noise dose may be computed for future
repetitive dives from different SONAR by using the planned dive time of
the repetitive dives (DT2, DT3…). (Page 1A-6)

WARNING

NOTE

Safety Summary

The practice of hyperventilating for the purpose of “blowing off” carbon
dioxide, (as differentiated from taking two or three deep breaths) prior to
a breath-hold dive is a primary cause of unconsciousness and may lead
to death. Breath-hold divers shall terminate the dive and surface at the
first sign of the urge to breathe. See paragraph 3-5.5 for more information
about hyperventilation and unconsciousness from breath-hold diving.
(Page 6-8)
Dynamic Positioning (DP) Capability. Some vessels possess dynamic
positioning (DP) capability. DP uses the ship’s propulsion systems
(thrusters, main propulsion, and rudders) to maintain a fixed position.
Surface-supplied diving and saturation diving, dynamic positioning (DP)
ships shall meet International Maritime Organization (IMO) Class 2 or 3
standards. IMO Equipment Class 2 or 3 will maintain automatic or manual
position and heading control under specified maximum environmental
conditions, during and following any single-point failure of the DP
system. See Appendix 2D, Guidance for U.S. Navy Diving on a Dynamic
Positioning Vessel, for conducting diving operations from a DP vessel.
(Page 6-10)

K

NOTE

WARNING

NOTE

Rescue strops are not appropriate for rescue of unconscious divers.
(Page 6-19)
A towel and razor is not required but highly recommended when using an
Automated External Defibrillator (AED). (Page 6-19)

CAUTION

Prior to use of VVDS as a buoyancy compensator, divers must be
thoroughly familiar with its use. (Page 7-15)

WARNING

When calculating duration of air supply, an adequate safety margin shall
be factored in. The deeper the dive, the more critical it is to ensure divers
have sufficient air to reach the surface in the event of a mishap. Dive
Supervisors shall consider outfitting each diver with an independent
secondary air source to provide a back-up should the diver experience
an equipment malfunction or be forced to ditch the primary apparatus.
Relying solely on a reserve may leave a diver with insufficient air to reach
the surface. (Page 7-21)

NOTE

Paragraph 7-5.4 addresses safety precautions for charging and handling
cylinders. (Page 7-23)

WARNING

Skip-breathing may lead to hypercapnia, unconsciousness, and death.
(Page 7-38)

CAUTION

Do not ditch the apparatus unless absolutely necessary as more air
may be available as the diver ascends due to the decreasing ambient
pressure. (Page 7-47)

NOTE
WARNING

L

Operational necessity is only invoked when mission’s success is
more important to the nation than the lives and/or equipment of those
undertaking it. Operational necessity does not apply to training. (Page
6-14)

Buddy breathing and free ascent may be required as a result of one or
more emergency situation. (Page 7-48)
During a free ascent or buddy breathing, the affected diver, or the diver
without the mouthpiece must exhale continuously to prevent a POIS due
to expanding air in the lungs. (Page 7-49)

NOTE

The standby diver shall remain on deck and be ready for deployment
during salvage operations and as indicated by ORM. (Page 8-5)

NOTE

Planned air usage estimates will vary from actual air usage. Dive
Supervisors must note initial bank pressures and monitor consumption
throughout the dive. If actual consumption exceeds planned consumption,
the Diving Supervisor may be required to curtail the dive in order to ensure
there is adequate air remaining in the primary air supply to complete
decompression. (Page 8-11)

NOTE

An operational risk assessment may indicate EGS use during dives
shallower than 60 fsw. (Page 8-11)
U.S. Navy Diving Manual

WARNING

Due to increased fire hazard risk, the use of oxygen in air diving systems
is restricted to those systems using AMU Purification Systems and
verified as meeting the requirements of Table 4-1. (Page 8-20)

CAUTION

Personnel conducting oxygen DLSS maintenance shall be qualified in
writing as an oxygen worker and DLSS maintenance Technician or O2 /
mixed-gas UBA Technician for the UBA they are conducting maintenance
on. (Page 8-20)

WARNING

If job conditions call for using a steel cable or a chain as a descent line,
the Diving Officer must approve such use. (Page 8-22)

WARNING

When possible, shackle the lift line directly to the stage with a safety
shackle, or screw-pin shackle seized with wire. If a hook is used it shall
be moused or pinned to prevent loss of the stage and injury to divers.
(Page 8-23)

CAUTION

When diving with a Variable Volume Dry Suit, avoid overinflation and
be aware of the possibility of blowup when breaking loose from mud.
If stuck, it is better to call for aid from the standby diver than to risk
blowup. (Page 8-31)

WARNING

If only one diver is in the water and no response is received from the diver.
The possibility of contaminated breathing supply should be considered
and a shift to secondary may be required. (Page 8-35)

WARNING

Due to increased fire hazard risk, the use of oxygen in air diving systems
is restricted to those systems using ANU Purification Systems and
verified as meeting the requirements of Table 4-1. (Page 9-11)

CAUTION

Personnel conducting O2 DLSS maintenance shall be qualified, in writing,
as an oxygen worker and DLSS maintenance Technician or O2/mixed-gas
UBA Technician for the UBA they are conducting maintenance on. (Page
9-11)

WARNING

The interval from leaving 40 fsw in the water to arriving at 50 fsw in the
chamber cannot exceed 5 minutes without incurring a penalty. (See
paragraph 9-12.6). (Page 9-16)

NOTE

The Commanding Officer must have approval to conduct planned
exceptional exposure dives. (Page 9-31)

WARNING

Table 9-4 cannot be used when diving with equipment that maintains a
constant partial pressure of oxygen such as the MK 16 MOD 0 and the MK
16 MOD 1. Consult NAVSEA 00C for specific guidance when diving the
MK 16 at altitudes greater than 1000 feet. (Page 9-49)

WARNING

Altitudes above 10,000 feet can impose serious stress on the body resulting
in significant medical problems while the acclimatization process takes
place. Ascents to these altitudes must be slow to allow acclimatization to
occur and prophylactic drugs may be required to prevent the occurrence

Safety Summary

M

of altitude sickness. These exposures should always be planned in
consultation with a Diving Medical Officer. Commands conducting diving
operations above 10,000 feet may obtain the appropriate decompression
procedures from NAVSEA 00C. (Page 9-50)
NOTE

Refer to paragraph 9-13.3 to correct divers’ depth gauge readings to
actual depths at altitude. (Page 9-52)

NOTE

For surface decompression dives on oxygen, the chamber stops
are not adjusted for altitude. Enter the same depths as at sea level.
Keeping chamber stop depths the same as sea level provides an extra
decompression benefit for the diver on oxygen. (Page 9-53)

NOTE

The Air III is not a substitute for ORM. Proper planning of the diving
evolution is essential. (Page 9-58)

WARNING
NOTE

The water temperature of 37°F was set as a limit as a result of Naval
Experimental Diving Unit’s regulator freeze-up testing. For planning
purposes, the guidance above may also be used for diving where the
water temperature is 38°F and above. (Page 11-2)

CAUTION

The wet suit is only a marginally effective thermal protective measure,
and its use exposes the diver to hypothermia and restricts available
bottom time. The use of alternative thermal protective equipment should
be considered in these circumstances. (Page 11-7)

CAUTION

Prior to the use of variable volume dry suits and hot water suits in cold and
ice-covered waters, divers shall be trained in their use and be thoroughly
familiar with the operation of these suits. (Page 11-8)

WARNING

Use of kerosene or propane heaters not designated for indoor use or
internal combustion engines inside of shelters may lead to carbon
monoxide poisoning and death. (Page 11-10)

WARNING

The NDC variant used must match the rig/diluent/dive method being
performed. Catastrophic decompression sickness could result if the
wrong NDC is selected. (Page 2B-3)

CAUTION

Divers should avoid strenuous exercise during decompression.(Page
2B-6)

NOTE

N

Mixing contaminated or non-oil free air with 100% oxygen can result in a
catastrophic fire and explosion. (Page 10-10)

Shifts in winds or tides may cause wild swings of the mooring and
endanger divers working on the bottom. Diving supervisors must maintain
situational awareness of weather and sea state and monitor changes
that may adversely affect the operation. Diving shall be discontinued if
sudden squalls, electrical storms, heavy seas, unusual tide or any other
condition exists that, in the opinion of the Diving Supervisor, jeopardizes
the safety of the divers or topside personnel. (Page 2C-1)

U.S. Navy Diving Manual

NOTE

The following are the general guidelines for warm water diving. Specific
UBAs may have restrictions greater than the ones listed below; refer to
the appropriate UBA Operations and Maintenance manual. The maximum
warm water dive time exposure limit shall be the lesser of the approved
UBA operational limits, canister duration limits, oxygen bottle duration or
the diver physiological exposure limit. (Page 2C-7)

WARNING

All enclosed space divers shall be outfitted with a KM-37 NS or MK 20 MOD
0/1 that includes a diver-to- diver and diver-to-topside communications
system and an EGS for the diver inside the space. (Page 2C-12)

WARNING

Divers in submarine ballast tanks shall not remove their diving equipment
until the atmosphere has been flushed twice with air from a compressed
air source meeting the requirements of Chapter 4, or the submarine
L.P. blower, and tests confirm that the atmosphere is safe for breathing.
Testing shall be done in accordance with NSTM 074, Volume 3, Gas Free
Engineering (S9086-CH-STM-030/CH-074) for forces afloat, and NAVSEA
S-6470-AA-SAF-010 for shore-based facilities and repeated hourly. (Page
2C-12)

WARNING

If divers smell any unusual odors, or if the diving equipment should fail,
the diver shall immediately switch to the EGS and abort the dive. (Page
2C-12)

CAUTION

GFIs require an established reference ground in order to function properly.
Cascading GFIs could result in loss of reference ground; therefore, GFIs
or equipment containing built-in GFIs should not be plugged into an
existing GFI circuit. (Page 2C-13)

NOTE:

All Navy commands shall contact NAVSEA 00C3 prior to conducting
diving operations from a DP vessel to obtain specific guidance and
authorization. DP diving will be authorized for Surface Supplied Air,
Mixed Gas and Saturation diving only. SCUBA and DP-2 diving are not
authorized from a DP vessel. (Page 2D-1)

NOTE:

While dive operations are in progress, the vessel shall not be moved
without consultation with the Dive Supervisor. All movements will be
at slow speed. Heading changes will not exceed five degrees at a time.
Movements will not exceed 32 feet (10 meters). The center of rotation for
any move will be the dive side/moon-pool unless otherwise agreed. The
divers will be notified and brought back to the stage before any planned
move begins. (Page 2D-5)

WARNING:

The divers and dive supervisor shall clearly communicate when removing
and attaching shackles. (Page 2D-15)

WARNING:

During diving operations at no time shall the open bell, diver’s stage or
clump be allowed to come in contact with the sea floor. The open bell,
divers stage and clump shall be located above all underwater structures

Safety Summary

O

or debris located in the proximity of the diving operations to prevent
fouling in the event of a run-off or black ship event. (Page 2D-15)
WARNING

NOTE

Usage for three divers is computed even though the standby would not
normally be using gas for the entire 15 minutes. (Page 13-13)

NOTE

Discharging UBA gas into the Dive Bell during diving operations may
make it difficult to control the oxygen level. (Page 13-19)

WARNING

Dive Bell can see spikes in CO2 well above .5%sev CO2 for short periods
while divers are dressing out for egress. These levels will drop rapidly
once CO2 scrubbers catch up. (Page 13-19)

CAUTION

During compression ensure an adequate ppO2 (0.16-1.25 ata) is
maintained. Be prepared to don BIBS or slow travel rates as required.
(Page 13-26)

NOTE

P

The interval from leaving 40-fsw in the water to arriving at 50-fsw in the
chamber cannot exceed 5 minutes without incurring a penalty. (See
paragraph 12-5.14). (Page 12-10)

USN dive system design incorporates separate primary, secondary, and
treatment gas supplies and redundancy of key equipment. It is neither the
intent of this section nor a requirement that saturation dive systems be
configured with additional gas stores specifically dedicated to execution
of an emergency abort procedure. Augmentation gas supplies if required
will be gained by returning to port or receiving additional supplies on
site. (Page 13-38)

WARNING

The typical EC-UBA provides no visual warning of excess CO2 problems.
The diver should be aware of CO2 toxicity symptoms. (Page 15-5)

CAUTION

There is an increased risk of CNS oxygen toxicity when diving a 1.3 pO2
EC-UBA compared to diving a 0.75 pO2 EC-UBA, especially during the
descent phase of the dive. Diving supervisors and divers should be aware
that oxygen partial pressures of 1.6 ata or higher may be temporarily
experienced during descent on N2O2 dives deeper than 120 fsw (21%
oxygen diluent) and on HeO2 dives deeper than 200 fsw (12% oxygen
diluent) Refer to Chapter 3 for more information on recognizing and
preventing CNS oxygen toxicity. (Page 15-17)

WARNING

Failure to adhere to these guidelines could result in serious injury or
death. (Page 15-17)

WARNING

The diving supervisor must ensure selection of both the proper ECUBA
set-point table, and proper diluent table for the dive being conducted.
(Page 15-19)

WARNING

These procedures cannot be used to make repetitive dives on air following
EC-UBA helium-oxygen dives. (Page 15-22)

U.S. Navy Diving Manual

WARNING

Hypoxia and hypercapnia may give the diver little or no warning prior to
onset of unconsciousness. (Page 15-28)

WARNING

Most CC-UBAs do not have a carbon dioxide-monitoring capability.
Failure to adhere to canister duration operations planning could lead to
unconsciousness and/or death. (Page 16-14)

CAUTION

Defibrillation is not currently authorized at depth. (Page 17-8)

CAUTION

If the tender is outside of no-decompression limits, take appropriate
steps to manage the tender’s decompression obligation. (Page 17-8)

CAUTION

If tenders are outside of no-decompression limits, take appropriate steps
to manage the tender’s decompression obligation. If the pulseless diver
does not regain a pulse with application of an AED, continue resuscitation
efforts until the diver recovers, the rescuers are unable to continue CPR,
or a physician pronounces the patient dead. Avoid recompressing a
pulseless diver who has failed to regain vital signs after use of an AED.
(Page 17-8)

NOTE

If deterioration or recurrence of symptoms is noted during ascent to 60
feet, treat as a recurrence of symptoms. (Page 17-18)

CAUTION

Inserting an airway device or bite block is not recommended while
the patient is convulsing; it is not only difficult, but may cause harm if
attempted. (Page 17-26)

WARNING

Drug therapy shall be administered only after consultation with a Diving
Medical Officer and only by qualified inside tenders adequately trained
and capable of administering prescribed medications. (Page 17-32)

CAUTION

AED’s are not currently approved for use under pressure (hyperbaric
environment) due to electrical safety concerns. (Page 17-36)

NOTE

Some vendors supply pre-packed ACLS kits with automated replenishment
programs (examples of which can be found on the Naval Expeditionary
Combat Command (NECC) AMAL). (Page 17-41)

NOTE

Stoppered multi-dose vials with large air volumes may need to be vented
with a needle during pressurization and depressurization and then
discarded. (Page 17-41)

WARNING

The gag valve must remain open at all times. Close only if relief valve
fails. (Page 18-20)

WARNING

This procedure is to be performed with an unmanned chamber to avoid
exposing occupants to unnecessary risks. (Page 8-21)

WARNING

Fire/Explosion Hazard. No matches, lighters, electrical appliances, or
flammable materials permitted in chamber. (Page 18-30)

Safety Summary

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U.S. Navy Diving Manual

Table of Contents
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1

HISTORY OF DIVING

1-1

INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1

1-2

1-1.1

Purpose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1

1-1.2

Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1

1-1.3

Role of the U.S. Navy. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1

SURFACE-SUPPLIED AIR DIVING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1
1-2.1

Breathing Tubes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2

1-2.2

Breathing Bags . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-3

1-2.3

Diving Bells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-3

1-2.4

Diving Dress Designs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-3
1-2.4.1
1-2.4.2
1-2.4.3
1-2.4.4

1-2.5

Caissons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5

1-2.6

Physiological Discoveries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-6
1-2.6.1
1-2.6.2
1-2.6.3

1-3

Lethbridge’s Diving Dress . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-3
Deane’s Patented Diving Dress . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-4
Siebe’s Improved Diving Dress . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-4
Salvage of the HMS Royal George . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5

Caisson Disease (Decompression Sickness). . . . . . . . . . . . . . . . . . . . . . . . . 1-6
Inadequate Ventilation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-7
Nitrogen Narcosis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-7

1-2.7

Armored Diving Suits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-7

1-2.8

MK V Deep-Sea Diving Dress . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-8

SCUBA DIVING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-8
1-3.1

Open-Circuit SCUBA. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-9
1-3.1.1
1-3.1.2
1-3.1.3
1-3.1.4

1-3.2

Rouquayrol’s Demand Regulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-9
LePrieur’s Open-Circuit SCUBA Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-9
Cousteau and Gagnan’s Aqua-Lung . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-10
Impact of SCUBA on Diving . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-10

Closed-Circuit SCUBA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-10
1-3.2.1
1-3.2.2

Fleuss’ Closed-Circuit SCUBA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-10
Modern Closed-Circuit Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-11

1-3.3

Hazards of Using Oxygen in SCUBA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-11

1-3.4

Semiclosed-Circuit SCUBA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-12
1-3.4.1
1-3.4.2

1-3.5

SCUBA Use During World War II . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-13
1-3.5.1
1-3.5.2
1-3.5.3

Table of Contents

Lambertsen’s Mixed-Gas Rebreather . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-12
MK 6 UBA. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-12

Diver-Guided Torpedoes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-13
U.S. Combat Swimming . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-14
Underwater Demolition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-15

i

Chap/Para
1-4

Page
MIXED-GAS DIVING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-16
1-4.1

Nonsaturation Diving . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-16
1-4.1.1
1-4.1.2
1-4.1.3
1-4.1.4

1-4.2

Diving Bells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-20

1-4.3

Saturation Diving . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-21
1-4.3.1
1-4.3.2
1-4.3.3
1-4.3.4
1-4.3.5

1-4.4

1-6

ADS-IV . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-25
MK 1 MOD 0. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-25
MK 2 MOD 0. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-25
MK 2 MOD 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-26

SUBMARINE SALVAGE AND RESCUE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-26
1-5.1

USS F-4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-26

1-5.2

USS S-51 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-27

1-5.3

USS S-4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-27

1-5.4

USS Squalus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-28

1-5.5

USS Thresher . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-28

1-5.6

Deep Submergence Systems Project . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-29

SALVAGE DIVING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-29
1-6.1

World War II Era . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-29
1-6.1.1
1-6.1.2
1-6.1.3

1-6.2

Pearl Harbor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-29
USS Lafayette . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-29
Other Diving Missions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-30

Vietnam Era . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-30

1-7

OPEN-SEA DEEP DIVING RECORDS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-30

1-8

SUMMARY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-31

2

UNDERWATER PHYSICS

2-1

INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1

2-2

ii

Advantages of Saturation Diving . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-21
Bond’s Saturation Theory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-22
Genesis Project . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-22
Developmental Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-22
Sealab Program . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-22

Deep Diving Systems (DDS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-24
1-4.4.1
1-4.4.2
1-4.4.3
1-4.4.4

1-5

Helium-Oxygen (HeO2) Diving . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-16
Hydrogen-Oxygen Diving . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-18
Modern Surface-Supplied Mixed-Gas Diving . . . . . . . . . . . . . . . . . . . . . . . . 1-19
MK 1 MOD 0 Diving Outfit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-20

2-1.1

Purpose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1

2-1.2

Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1

PHYSICS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1

U.S. Navy Diving Manual

Chap/Para
2-3

2-4

Page
MATTER . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1
2-3.1

Elements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1

2-3.2

Atoms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1

2-3.3

Molecules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1

2-3.4

The Three States of Matter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2

MEASUREMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2
2-4.1

Measurement Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2

2-4.2

Temperature Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-3
2-4.2.1
2-4.2.2

2-4.3
2-5

2-6

2-7

Gas Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-3

ENERGY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-4
2-5.1

Conservation of Energy. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-5

2-5.2

Classifications of Energy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-5

LIGHT ENERGY IN DIVING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-5
2-6.1

Refraction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-5

2-6.2

Turbidity of Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-6

2-6.3

Diffusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-6

2-6.4

Color Visibility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-6

MECHANICAL ENERGY IN DIVING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-6
2-7.1

Water Temperature and Sound . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-7

2-7.2

Water Depth and Sound . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-7
2-7.2.1
2-7.2.2

2-7.3

2-9

Diver Work and Noise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-7
Pressure Waves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-7

Underwater Explosions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-8
2-7.3.1
2-7.3.2
2-7.3.3
2-7.3.4
2-7.3.5
2-7.3.6
2-7.3.7
2-7.3.8

2-8

Kelvin Scale . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-3
Rankine Scale . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-3

Type of Explosive and Size of the Charge . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-8
Characteristics of the Seabed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-8
Location of the Explosive Charge. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-8
Water Depth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-8
Distance from the Explosion. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-8
Degree of Submersion of the Diver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-9
Estimating Explosion Pressure on a Diver . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-9
Minimizing the Effects of an Explosion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-10

HEAT ENERGY IN DIVING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-10
2-8.1

Conduction, Convection, and Radiation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-10

2-8.2

Heat Transfer Rate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-10

2-8.3

Diver Body Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-11

PRESSURE IN DIVING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-11
2-9.1

Table of Contents

Atmospheric Pressure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-12

iii

Chap/Para

Page
2-9.2

Terms Used to Describe Gas Pressure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-12

2-9.3

Hydrostatic Pressure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-12

2-9.4

Buoyancy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-13
2-9.4.1
2-9.4.2

Archimedes’ Principle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-13
Diver Buoyancy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-13

2-10 GASES IN DIVING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-14

2-11

2-10.1

Atmospheric Air . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-14

2-10.2

Oxygen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-15

2-10.3

Nitrogen. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-15

2-10.4

Helium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-15

2-10.5

Hydrogen. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-15

2-10.6

Neon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-15

2-10.7

Carbon Dioxide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-16

2-10.8

Carbon Monoxide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-16

2-10.9

Kinetic Theory of Gases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-16

GAS LAWS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-17
2-11.1

Boyle’s Law . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-17

2-11.2

Charles’/Gay-Lussac’s Law. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-18

2-11.3

The General Gas Law . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-21

2-12 GAS MIXTURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-24
2-12.1

Dalton’s Law . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-24
2-12.1.1 Calculating Surface Equivalent Value . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-27
2-12.1.2 Expressing Small Quantities of Pressure . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-28
2-12.1.3 Expressing Small Quantities of Volume . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-28

2-12.2

Gas Diffusion. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-28

2-12.3

Humidity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-29

2-12.4

Gases in Liquids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-29

2-12.5

Solubility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-29

2-12.6

Henry’s Law . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-29
2-12.6.1 Gas Tension . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-30
2-12.6.2 Gas Absorption . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-30
2-12.6.3 Gas Solubility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-30

iv

3

UNDERWATER PHYSIOLOGY AND DIVING DISORDERS

3-1

INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1
3-1.1

Purpose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1

3-1.2

Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1

3-1.3

General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1

U.S. Navy Diving Manual

Chap/Para

Page

3-2

THE NERVOUS SYSTEM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1

3-3

THE CIRCULATORY SYSTEM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2
3-3.1

Anatomy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2
3-3.1.1
3-3.1.2

3-4

3-3.2

Circulatory Function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2

3-3.3

Blood Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-3

THE RESPIRATORY SYSTEM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-5
3-4.1

Gas Exchange. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-5

3-4.2

Respiration Phases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-5

3-4.3

Upper and Lower Respiratory Tract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-6

3-4.4

The Respiratory Apparatus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-6
3-4.4.1
3-4.4.2

3-5

The Heart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2
The Pulmonary and Systemic Circuits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2

The Chest Cavity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-6
The Lungs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-6

3-4.5

Respiratory Tract Ventilation Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-8

3-4.6

Alveolar/Capillary Gas Exchange . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-9

3-4.7

Breathing Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-10

3-4.8

Oxygen Consumption . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-11

RESPIRATORY PROBLEMS IN DIVING. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-11
3-5.1

Oxygen Deficiency (Hypoxia) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-12
3-5.1.1
3-5.1.2
3-5.1.3
3-5.1.4

3-5.2

Causes of Hypoxia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-13
Symptoms of Hypoxia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-13
Treatment of Hypoxia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-14
Prevention of Hypoxia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-14

Carbon Dioxide Retention (Hypercapnia) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-15
3-5.2.1
3-5.2.2
3-5.2.3
3-5.2.4

Causes of Hypercapnia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-15
Symptoms of Hypercapnia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-16
Treatment of Hypercapnia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-17
Prevention of Hypercapnia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-18

3-5.3

Asphyxia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-18

3-5.4

Drowning/Near Drowning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-18
3-5.4.1
3-5.4.2
3-5.4.3
3-5.4.4

Causes of Drowning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-18
Symptoms of Drowning/Near Drowning . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-19
Treatment of Near Drowning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-19
Prevention of Near Drowning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-19

3-5.5

Breathholding and Unconsciousness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-20

3-5.6

Involuntary Hyperventilation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-20
3-5.6.1
3-5.6.2
3-5.6.3

3-5.7

Table of Contents

Causes of Involuntary Hyperventilation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-20
Symptoms of Involuntary Hyperventilation . . . . . . . . . . . . . . . . . . . . . . . . . . 3-20
Treatment of Involuntary Hyperventilation . . . . . . . . . . . . . . . . . . . . . . . . . . 3-21

Overbreathing the Rig . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-21

v

Chap/Para

Page
3-5.8

Carbon Monoxide Poisoning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-21
3-5.8.1
3-5.8.2
3-5.8.3
3-5.8.4

3-6

MECHANICAL EFFECTS OF PRESSURE ON THE HUMAN BODY-BAROTRAUMA
DURING DESCENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-23
3-6.1

Prerequisites for Squeeze . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-23

3-6.2

Middle Ear Squeeze . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-24
3-6.2.1
3-6.2.2

3-6.3

3-8

Causes of Sinus Squeeze . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-25
Preventing Sinus Squeeze . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-26

3-6.4

Tooth Squeeze (Barodontalgia). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-26

3-6.5

External Ear Squeeze . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-26

3-6.6

Thoracic (Lung) Squeeze. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-27

3-6.7

Face or Body Squeeze . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-27

3-6.8

Inner Ear Barotrauma . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-27

MECHANICAL EFFECTS OF PRESSURE ON THE HUMAN BODY--BAROTRAUMA
DURING ASCENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-30
3-7.1

Middle Ear Overpressure (Reverse Middle Ear Squeeze) . . . . . . . . . . . . . . . . . . . . . . 3-30

3-7.2

Sinus Overpressure (Reverse Sinus Squeeze) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-31

3-7.3

Gastrointestinal Distention . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-31

PULMONARY OVERINFLATION SYNDROMES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-32
3-8.1

Arterial Gas Embolism (AGE) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-33
3-8.1.1
3-8.1.2
3-8.1.3
3-8.1.4

3-8.2

3-8.3

Causes of AGE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-34
Symptoms of AGE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-34
Treatment of AGE. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-35
Prevention of AGE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-35

Mediastinal and Subcutaneous Emphysema . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-36
3-8.2.1
3-8.2.2
3-8.2.3
3-8.2.4

Causes of Mediastinal and Subcutaneous Emphysema . . . . . . . . . . . . . . . 3-36
Symptoms of Mediastinal and Subcutaneous Emphysema . . . . . . . . . . . . . 3-37
Treatment of Mediastinal and Subcutaneous Emphysema . . . . . . . . . . . . . 3-37
Prevention of Mediastinal and Subcutaneous Emphysema . . . . . . . . . . . . . 3-38

Pneumothorax . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-38
3-8.3.1
3-8.3.2
3-8.3.3
3-8.3.4

vi

Preventing Middle Ear Squeeze . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-24
Treating Middle Ear Squeeze . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-25

Sinus Squeeze . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-25
3-6.3.1
3-6.3.2

3-7

Causes of Carbon Monoxide Poisoning . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-21
Symptoms of Carbon Monoxide Poisoning . . . . . . . . . . . . . . . . . . . . . . . . . 3-22
Treatment of Carbon Monoxide Poisoning . . . . . . . . . . . . . . . . . . . . . . . . . . 3-22
Prevention of Carbon Monoxide Poisoning . . . . . . . . . . . . . . . . . . . . . . . . . 3-22

Causes of Pneumothorax . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-38
Symptoms of Pneumothorax . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-39
Treatment of Pneumothorax . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-40
Prevention of Pneumothorax . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-40

U.S. Navy Diving Manual

Chap/Para
3-9

Page
INDIRECT EFFECTS OF PRESSURE ON THE HUMAN BODY . . . . . . . . . . . . . . . . . . . . . . . . 3-40
3-9.1

Nitrogen Narcosis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-40
3-9.1.1
3-9.1.2
3-9.1.3
3-9.1.4

3-9.2

Oxygen Toxicity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-42
3-9.2.1
3-9.2.2

3-9.3

Causes of Nitrogen Narcosis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-41
Symptoms of Nitrogen Narcosis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-41
Treatment of Nitrogen Narcosis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-41
Prevention of Nitrogen Narcosis. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-41

Pulmonary Oxygen Toxicity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-42
Central Nervous System (CNS) Oxygen Toxicity . . . . . . . . . . . . . . . . . . . . . 3-42

Decompression Sickness (DCS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-46
3-9.3.1
3-9.3.2
3-9.3.3
3-9.3.4
3-9.3.5
3-9.3.6
3-9.3.7

Absorption and Elimination of Inert Gases . . . . . . . . . . . . . . . . . . . . . . . . . . 3-46
Bubble Formation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-50
Direct Bubble Effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-50
Indirect Bubble Effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-51
Symptoms of Decompression Sickness . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-51
Treating Decompression Sickness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-52
Preventing Decompression Sickness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-52

3-10 THERMAL PROBLEMS IN DIVING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-52
3-10.1

Regulating Body Temperature. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-53

3-10.2

Excessive Heat Loss (Hypothermia) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-53
3-10.2.1
3-10.2.2
3-10.2.3
3-10.2.4

3-10.3

Causes of Hypothermia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-53
Symptoms of Hypothermia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-54
Treatment of Hypothermia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-54
Prevention of Hypothermia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-55

Other Physiological Effects of Exposure to Cold Water . . . . . . . . . . . . . . . . . . . . . . . . 3-56
3-10.3.1 Caloric Vertigo . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-56
3-10.3.2 Diving Reflex . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-56
3-10.3.3 Uncontrolled Hyperventilation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-56

3-10.4

Excessive Heat Gain (Hyperthermia) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-56
3-10.4.1
3-10.4.2
3-10.4.3
3-10.4.4

3-11

Causes of Hyperthermia. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-56
Symptoms of Hyperthermia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-57
Treatment of Hyperthermia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-57
Prevention of Hyperthermia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-58

SPECIAL MEDICAL PROBLEMS ASSOCIATED WITH DEEP DIVING . . . . . . . . . . . . . . . . . . 3-58
3-11.1

High Pressure Nervous Syndrome (HPNS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-58

3-11.2

Compression Arthralgia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-58

3-12 OTHER DIVING MEDICAL PROBLEMS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-59
3-12.1

Dehydration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-59
3-12.1.1 Causes of Dehydration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-59
3-12.1.2 Preventing Dehydration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-60

3-12.2

Immersion Pulmonary Edema . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-60

3-12.3

Carotid Sinus Reflex . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-60

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Chap/Para

Page
3-12.4

Middle Ear Oxygen Absorption Syndrome . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-60
3-12.4.1 Symptoms of Middle Ear Oxygen Absorption Syndrome . . . . . . . . . . . . . . . 3-61
3-12.4.2 Treating Middle Ear Oxygen Absorption Syndrome . . . . . . . . . . . . . . . . . . . 3-61

3-12.5

Underwater Trauma . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-61

3-12.6

Blast Injury . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-61

3-12.7

Otitis Externa. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-62

3-12.8

Hypoglycemia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-63

3-12.9

Use of Medications While Diving. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-63

4

DIVE SYSTEMS

4-1

INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1

4-2

4-1.1

Purpose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1

4-1.2

Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1

4-1.3

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1

GENERAL INFORMATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-2
4-2.1

Document Precedence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-2

4-2.2

Equipment Authorized For Military Use (AMU) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-2

4-2.3

System Certification Authority (SCA) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-3

4-2.4

Planned Maintenance System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-3

4-2.5

Alteration of Diving Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-3
4-2.5.1
4-2.5.2

4-2.6

Operating and Emergency Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-3
4-2.6.1
4-2.6.2
4-2.6.3
4-2.6.4
4-2.6.5

4-3

4-4

viii

Technical Program Managers for Shore-Based Systems. . . . . . . . . . . . . . . . 4-3
Technical Program Managers for Other Diving Apparatus . . . . . . . . . . . . . . . 4-3

Standard Dive Systems/Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-4
Non-Standard Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-4
OP/EP Approval Process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-4
Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-4
Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-5

DIVER’S BREATHING GAS PURITY STANDARDS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-5
4-3.1

Diver’s Breathing Air . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-5

4-3.2

Diver’s Breathing Oxygen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-6

4-3.3

Diver’s Breathing Helium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-7

4-3.4

Diver’s Breathing Nitrogen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-8

DIVER’S AIR SAMPLING PROGRAM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-8
4-4.1

Sampling Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-9

4-4.2

NSWC-PC Air Sampling Services . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-9

4-4.3

Local Air Sampling Services . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-10

4-4.4

Portable Air Monitor (PAM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-10

4-4.5

General Air Sampling Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-10

U.S. Navy Diving Manual

Chap/Para
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Page
DIVE SYSTEM COMPONENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-11
4-5.1

Diving Compressors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-11
4-5.1.1
4-5.1.2
4-5.1.3
4-5.1.4
4-5.1.5
4-5.1.6

4-5.2

High-Pressure Air Cylinders and Flasks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-14
4-5.2.1

4-5.3

Lubrication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-12
Maintaining Oil Lubricated Compressors . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-12
Water Vapor Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-13
Volume Tank . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-13
Pressure Regulators. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-13
Air Filtration System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-14

Compressed Gas Handling and Storage . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-15

Diving Gauges. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-15
4-5.3.1
4-5.3.2
4-5.3.3
4-5.3.4

Selecting Diving System Gauges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-15
Calibrating and Maintaining Gauges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-16
Helical Bourdon Tube Gauges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-16
Pneumofathometer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-17

5

DIVE PROGRAM ADMINISTRATION

5-1

INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-1
5-1.1

Purpose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-1

5-1.2

Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-1

5-2

OBJECTIVES OF THE RECORD KEEPING AND REPORTING SYSTEM . . . . . . . . . . . . . . . . . 5-1

5-3

RECORD KEEPING AND REPORTING DOCUMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-1

5-4

COMMAND DIVE LOG . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-2

5-5

RECOMPRESSION CHAMBER LOG . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-2

5-6

U.S. NAVY DIVE/JUMP REPORTING SYSTEM (DJRS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-4

5-7

PERSONAL DIVE LOG . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-4

5-8

EQUIPMENT FAILURE OR DEFICIENCY REPORTING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-4

5-9

DIVE MISHAP/NEAR MISHAP/HAZARD REPORTING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-4
5-9.1

Mishap/Near-Mishap/Hazard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-4

5-9.2

Judge Advocate General (JAG Investigation) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-5

5-9.3

Reporting Criteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-5

5-9.4

HAZREPS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-5

5-10 ACTIONS REQUIRED . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-6
5-10.1

Equipment Mishap Information Sheet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-7

5-10.2

Shipment of Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-8

Table of Contents

ix

Chap/Para
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Page
SAFE DIVING DISTANCES FROM TRANSMITTING SONAR

1A-1 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1A-1
1A-2 BACKGROUND . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1A-1
1A-3 ACTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1A-2
1A-4 SONAR DIVING DISTANCES WORKSHEETS WITH DIRECTIONS FOR USE . . . . . . . . . . . . 1A-2
1A-4.1

General Information/Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1A-2
1A-4.1.1 Effects of Exposure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1A-2
1A-4.1.2 Suit and Hood Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1A-2
1A-4.1.3 In-Water Hearing vs. In-Gas Hearing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1A-2

1A-4.2

Directions for Completing the Sonar Diving Distances Worksheet . . . . . . . . . . . . . . . . 1A-3

1A-5 GUIDANCE FOR DIVER EXPOSURE TO LOW-FREQUENCY SONAR (160–320 HZ) . . . . . 1A-16
1A-6 GUIDANCE FOR DIVER EXPOSURE TO ULTRASONIC SONAR
(250 KHZ AND GREATER) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1A-16

1B

REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1B-1

1C

TELEPHONE NUMBERS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1C-1

1D

LIST OF ACRONYMS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1D-1

6

OPERATIONAL PLANNING AND RISK MANAGEMENT

6-1

INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-1

6-2

6-1.1

Purpose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-1

6-1.2

Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-1

6-1.3

Planning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-2

MISSION ANALYSIS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-2
6-2.1

x

Mission Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-2
6-2.1.1
Underwater Ship Husbandry (UWSH) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-2
6-2.1.2
Search Missions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-3
6-2.1.3
Salvage/Object Recovery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-3
6-2.1.4
Harbor Clearance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-4
6-2.1.5
Security Dives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-5
6-2.1.6
Explosive Ordnance Disposal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-5
6-2.1.7
Underwater Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-6
6-2.1.8
Battle Damage Assessment and Repair (BDA/R) . . . . . . . . . . . . . . . . . . . . . 6-6
6-2.1.9
Combat Diver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-6
6-2.1.10 Dive Training . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-6
6-2.1.11 Free Ascent/Escape Training and Operations . . . . . . . . . . . . . . . . . . . . . . . . 6-6

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Chap/Para

Page
6-2.2

6-2.3
6-3

6-4

Analyze Available Forces and Assets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-7
6-2.2.1

Dive Techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-7

6-2.2.2

Diving Craft and Platforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-9

Commanders Intent and Planning Guidance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-12

COURSE OF ACTION DEVELOPMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-12
6-3.1

Analyze Unit Strengths and Weaknesses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-12

6-3.2

Generate Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-12

6-3.3

Develop Planning Assumptions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-12

COURSE OF ACTION ANALYSIS/RISK ASSESSMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-13
6-4.1

COA Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-13

6-4.2

Risk Assessment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-13
6-4.2.1

6-5

TASK PLANNING AND EMERGENCY ASSISTANCE. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-17
6-5.1

Task Planning and Scheduling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-17
6-5.1.1
6-5.1.2
6-5.1.3

6-6

Levels of ORM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-14

Task Schedule . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-17
Work-up Dives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-17
Emergency Assistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-18

TRANSITION (EXECUTION) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-21
6-6.1

Mission Brief . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-21

6-6.2

Dive Brief. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-22

6-6.3

Responsibilities While Operation is Underway . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-23
6-6.3.1
6-6.3.2
6-6.3.3
6-6.3.4

6-6.4

Situational Awareness (SA) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-24
Decision Making . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-25
Fatigue . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-26
Stress . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-27

Post Dive/Post Mission . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-27
6-6.4.1

Post-dive/Post Mission Debrief . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-28

7

SCUBA AIR DIVING OPERATIONS

7-1

INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-1

7-2

7-1.1

Purpose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-1

7-1.2

Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-1

7-1.3

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-1

OPERATIONAL CONSIDERATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-1
7-2.1

Operational Limits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-1

7-2.2

Manning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-4
7-2.2.1
7-2.2.2

Table of Contents

SCUBA Diving Supervisor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-4
SCUBA Diver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-5

xi

Chap/Para

Page
7-2.2.3
7-2.2.4
7-2.2.5
7-2.2.6

7-3

MINIMUM EQUIPMENT FOR SCUBA OPERATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-7
7-3.1

Open-Circuit SCUBA. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-7
7-3.1.1
7-3.1.2

7-4

Buddy Diver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-5
Standby SCUBA Diver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-6
Tenders. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-6
Other Personnel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-7

Demand Regulator Assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-8
Cylinders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-11

7-3.2

Face Mask. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-13

7-3.3

Life Preserver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-14

7-3.4

Buoyancy Compensator (BC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-14

7-3.5

Weight Belt . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-15

7-3.6

Knife . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-16

7-3.7

Swim Fins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-16

7-3.8

Wrist Watch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-16

7-3.9

Depth Gauge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-16

OPTIONAL EQUIPMENT FOR SCUBA OPERATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-17
7-4.1

Protective Clothing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-17
7-4.1.1

Wet Suits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-17

7-4.1.2

Variable Volume Dry Suits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-18

7-4.1.3

Gloves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-19

7-4.1.4

Writing Slate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-19

7-4.1.5

Signal Flare . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-19

7-4.1.6

Acoustic Beacons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-19

7-4.1.7

Lines and Floats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-19

7-4.1.8

Snorkel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-20

7-4.1.9

Compass . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-20

7-4.1.10 Dive Computers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-20
7-4.1.11
7-5

AIR SUPPLY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-21
7-5.1

Duration of Air Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-21

7-5.2

Methods for Charging SCUBA Cylinders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-23

7-5.3

Operating Procedures for Charging SCUBA Tanks. . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-25
7-5.3.1

7-5.4
7-6

Topping off the SCUBA Cylinder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-25

Safety Precautions for Charging and Handling Cylinders . . . . . . . . . . . . . . . . . . . . . . . 7-26

PREDIVE PROCEDURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-27
7-6.1

Equipment Preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-27
7-6.1.1
7-6.1.2

xii

Independent Secondary Air Source . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-20

Air Cylinders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-27
Harness Straps and Backpack . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-28

U.S. Navy Diving Manual

Chap/Para

Page
7-6.1.3
7-6.1.4
7-6.1.5
7-6.1.6
7-6.1.7
7-6.1.8
7-6.1.9
7-6.1.10
7-6.1.11
7-6.1.12
7-6.1.13

7-7

7-6.2

Dive Brief . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7-30

7-6.3

Donning Gear . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7-30

7-6.4

Predive Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7-31

WATER ENTRY AND DESCENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-32
7-7.1

7-8

7-9

Breathing Hoses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7-28
Regulator. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7-28
Life Preserver/Buoyancy Compensator (BC) . . . . . . . . . . . . . . . . . . . . . . . . .7-28
Face Mask . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7-29
Swim Fins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7-29
Dive Knife . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7-29
Snorkel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7-29
Weight Belt . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7-29
Submersible Wrist Watch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7-29
Depth Gauge and Compass . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7-29
Miscellaneous Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7-30

Water Entry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-32
7-7.1.1

Step-In Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-32

7-7.1.2

Rear Roll Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-36

7-7.1.3

Front Roll Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-36

7-7.1.4

Side Roll Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-36

7-7.1.5

Entering the Water from the Beach . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-36

7-7.2

In-Water Checks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-37

7-7.3

Surface Swimming . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-38

7-7.4

Descent . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-38

UNDERWATER PROCEDURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-39
7-8.1

Breathing Technique . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-39

7-8.2

Mask Clearing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-39

7-8.3

Regulator Clearing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-39

7-8.4

Swimming Technique . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-40

7-8.5

Diver Communications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-40
7-8.5.1

Through-Water Communication Systems . . . . . . . . . . . . . . . . . . . . . . . . . . 7-40

7-8.5.2

Hand and Line-Pull Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-43

7-8.6

Working with Tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-43

7-8.7

Adapting to Underwater Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-44

7-8.8

Emergency Assistance/Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-44
7-8.8.1

Emergency Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-45

7-8.8.2

Emergency Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-45

7-8.8.3

Actions Following an Emergency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-49

ASCENT PROCEDURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-49
7-9.1

Table of Contents

Ascent Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-49

xiii

Chap/Para

Page
7-9.1.1

Buddy Breathing Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-49

7-9.1.2

Emergency Free-Ascent Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-50

7-9.2

Ascent From Under a Vessel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-50

7-9.3

Decompression . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-51

7-9.4

Surfacing and Leaving the Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-52

7-10 POSTDIVE PROCEDURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-52

8

SURFACE SUPPLIED AIR DIVING OPERATIONS

8-1

INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-1

8-2

8-1.1

Purpose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-1

8-1.2

Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-1

8-1.3

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-1

KM-37 NS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-1
8-2.1

Operational Limits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-1

8-2.2

Personnel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-2
8-2.2.1
8-2.2.2
8-2.2.3
8-2.2.4
8-2.2.5
8-2.2.6
8-2.2.7
8-2.2.8
8-2.2.9

8-3

KM-37 NS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-7
8-3.1

Operation and Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-7

8-3.2

Air Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-7
8-3.2.1
8-3.2.2
8-3.2.3

8-4

8-5

Pressure Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-7
Air Available Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-8
Emergency Gas Supply Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-11

MK 20 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-14
8-4.1

Operation and Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-14

8-4.2

Air Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-14
8-4.2.1

Emergency Gas Supply Requirements for MK 20 ESD . . . . . . . . . . . . . . . . 8-14

8-4.2.2

Additional EGS Guidance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-15

PORTABLE SURFACE-SUPPLIED DIVING SYSTEMS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-15
8-5.1

Divator DP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-15
8-5.1.1

8-5.2

xiv

Watchstation Diving Officer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-3
Master Diver Responsibilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-4
Dive Supervisor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-4
Console/Rack Operator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-4
Standby Diver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-5
Divers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-5
Diver Tender . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-6
Log Keeper . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-6
Other Support Personnel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-7

DP Configurations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-16

MK 3 Lightweight Dive System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-18

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8-5.3

Flyaway Dive System (FADS) III . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-19

8-5.4

Oxygen Regulator Console Assembly (ORCA) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-20

8-6

SURFACE-SUPPLIED DIVING ACCESSORY EQUIPMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-21

8-7

DIVER COMMUNICATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-23

8-8

8-9

8-7.1

Diver Intercommunication Systems. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-23

8-7.2

Line-Pull Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-23

PREDIVE PROCEDURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-30
8-8.1

Setting a Moor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-30

8-8.2

Dive Station Preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-30

8-8.3

Air Supply Preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-31

8-8.4

Line Preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-32

8-8.5

Verify Environmental Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-32

8-8.6

Recompression Chamber Inspection and Preparation . . . . . . . . . . . . . . . . . . . . . . . . . 8-32

8-8.7

Predive Inspection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-33

8-8.8

Donning Gear . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-33

8-8.9

Diving Supervisor Predive Checklist . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-33

WATER ENTRY AND DESCENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-26
8-9.1

Predescent Surface Check . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-26

8-9.2

Descent . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-27

8-10 UNDERWATER PROCEDURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-27
8-10.1

Adapting to Underwater Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-27

8-10.2

Movement on the Bottom . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-27

8-10.3

Searching on the Bottom. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-30

8-10.4

Working Around Corners . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-31

8-10.5

Working Inside a Wreck . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-31

8-10.6

Working with or Near Lines or Moorings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-31

8-10.7

Bottom Checks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-32

8-10.8

Working with Tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-32

8-10.9

Safety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-32
8-10.9.1 Fouled Umbilical . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-34
8-10.9.2 Fouled Descent Lines. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-34
8-10.9.3 Loss of Communications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-34
8-10.9.4 Loss of Gas Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-35
8-10.9.5 Falling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-35
8-10.9.6 Damage to Helmet and Diving Dress . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-35

8-10.10 Tending the Diver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-35
8-10.11 Monitoring the Diver’s Movements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-36

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Page
ASCENT PROCEDURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-36

8-12 SURFACE DECOMPRESSION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-38
8-12.1

Surface Decompression Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-38

8-13 POSTDIVE PROCEDURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-38

xvi

8-13.1

Personnel and Reporting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-38

8-13.2

Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-39

9

AIR DECOMPRESSION

9-1

INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-1
9-1.1

Purpose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-1

9-1.2

Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-1

9-2

THEORY OF DECOMPRESSION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-1

9-3

AIR DECOMPRESSION DEFINITIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-2
9-3.1

Descent Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-2

9-3.2

Bottom Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-2

9-3.3

Total Decompression Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-2

9-3.4

Total Time of Dive . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-2

9-3.5

Deepest Depth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-2

9-3.6

Maximum Depth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-2

9-3.7

Stage Depth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-2

9-3.8

Decompression Table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-3

9-3.9

Decompression Schedule . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-3

9-3.10

Decompression Stop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-3

9-3.11

No-Decompression (No “D”) Limit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-3

9-3.12

No-Decompression Dive . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-3

9-3.13

Decompression Dive . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-3

9-3.14

Surface Interval . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-3

9-3.15

Residual Nitrogen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-3

9-3.16

Single Dive . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-3

9-3.17

Repetitive Dive . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-3

9-3.18

Repetitive Group Designator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-3

9-3.19

Residual Nitrogen Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-3

9-3.20

Equivalent Single Dive . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-4

9-3.21

Equivalent Single Dive Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-4

9-3.22

Surface Decompression . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-4

9-3.23

Exceptional Exposure Dive . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-4

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9-4

DIVE CHARTING AND RECORDING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-4

9-5

THE AIR DECOMPRESSION TABLES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-6

9-6

GENERAL RULES FOR THE USE OF AIR DECOMPRESSION TABLES . . . . . . . . . . . . . . . . . 9-7

9-7

9-6.1

Selecting the Decompression Schedule . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-7

9-6.2

Descent Rate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-7

9-6.3

Ascent Rate. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-7

9-6.4

Decompression Stop Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-7

9-6.5

Last Water Stop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-8

9-6.6

Eligibility for Surface Decompression . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-8

NO-DECOMPRESSION LIMITS AND REPETITIVE GROUP DESIGNATION TABLE
FOR NO-DECOMPRESSION AIR DIVES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-8
9-7.1

9-8

Optional Shallow Water No-Decompression Table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-9

THE AIR DECOMPRESSION TABLE. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-9
9-8.1

In-Water Decompression on Air . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-9

9-8.2

In-Water Decompression on Air and Oxygen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-11
9-8.2.1
9-8.2.2

9-8.3

Surface Decompression on Oxygen (SurDO2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-15
9-8.3.1
9-8.3.2

9-8.4
9-9

Procedures for Shifting to 100% Oxygen at 30 or 20 fsw. . . . . . . . . . . . . . . 9-13
Air Breaks at 30 and 20 fsw . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-13

Surface Decompression on Oxygen Procedure . . . . . . . . . . . . . . . . . . . . . . 9-16
Surface Decompression from 30 and 20 fsw . . . . . . . . . . . . . . . . . . . . . . . . 9-19

Selection of the Mode of Decompression . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-21

REPETITIVE DIVES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-21
9-9.1

Repetitive Dive Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-23

9-9.2

RNT Exception Rule . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-29

9-9.3

Repetitive Air to Nitrogen-Oxygen EC-UBA or Nitrogen-Oxygen EC-UBA to Air Dives 9-30

9-9.4

Order of Repetitive Dives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-30

9-10 EXCEPTIONAL EXPOSURE DIVES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-30
9-11

VARIATIONS IN RATE OF ASCENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-31
9-11.1

Travel Rate Exceeded . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-31

9-11.2

Early Arrival at the First Decompression Stop. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-31

9-11.3

Delays in Arriving at the First Decompression Stop . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-31

9.11.4

Delays in Leaving a Stop or Between Decompression Stops . . . . . . . . . . . . . . . . . . . . 9-32

9-12 EMERGENCY PROCEDURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-35
9-12.1

Bottom Time in Excess of the Table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-35

9-12.2

Loss of Oxygen Supply in the Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-36

9-12.3

Contamination of Oxygen Supply with Air . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-37

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9-12.4

CNS Oxygen Toxicity Symptoms (Non-convulsive) at 30 or 20 fsw Water Stop . . . . . . 9-37

9-12.5

Oxygen Convulsion at the 30- or 20-fsw Water Stop . . . . . . . . . . . . . . . . . . . . . . . . . . 9-38

9-12.6

Surface Interval Greater than 5 Minutes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-39

9-12.7

Decompression Sickness During the Surface Interval . . . . . . . . . . . . . . . . . . . . . . . . . 9-40

9-12.8

Loss of Oxygen Supply in the Chamber . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-41

9-12.9

CNS Oxygen Toxicity in the Chamber . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-42

9-12.10 Asymptomatic Omitted Decompression . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-43
9-12.10.1 No-Decompression Stops Required . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-44
9-12.10.2 Omitted Decompression Stops at 30 and 20 fsw . . . . . . . . . . . . . . . . . . . . . 9-44
9-12.10.3 Omitted Decompression Stops Deeper than 30 fsw . . . . . . . . . . . . . . . . . . 9-45
9-12.11 Decompression Sickness in the Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-45
9-12.11.1 Diver Remaining in the Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-45
9-12.11.2 Diver Leaving the Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-46
9-13 DIVING AT ALTITUDE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-46
9-13.1

Altitude Correction Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-47
9-13.1.1 Correction of Dive Depth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-47
9-13.1.2 Correction of Decompression Stop Depth . . . . . . . . . . . . . . . . . . . . . . . . . . 9-47

9-13.2

Need for Correction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-49

9-13.3

Depth Measurement at Altitude . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-49

9-13.4

Equilibration at Altitude . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-49

9-13.5

Diving at Altitude Worksheet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-52
9-13.5.1 Corrections for Depth of Dive at Altitude and In-Water Stops . . . . . . . . . . . 9-52
9-13.5.2 Corrections for Equilibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-52

9-13.6

Repetitive Dives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-53

9-14 ASCENT TO ALTITUDE AFTER DIVING / FLYING AFTER DIVING . . . . . . . . . . . . . . . . . . . . . 9-57
9-15 DIVE COMPUTER. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-58

10

NITROGEN-OXYGEN DIVING OPERATIONS

10-1 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-1
10-1.1

Advantages and Disadvantages of NITROX Diving . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-1

10-2 EQUIVALENT AIR DEPTH . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-1
10-2.1

Equivalent Air Depth Calculation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-2

10-3 OXYGEN TOXICITY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-2
10-3.1

Selecting the Proper NITROX Mixture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-3

10-4 NITROX DIVING PROCEDURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-3

xviii

10-4.1

NITROX Diving Using Equivalent Air Depths . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-3

10-4.2

SCUBA Operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-5

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Chap/Para

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10-4.3

Special Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-5

10-4.4

Omitted Decompression . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-5

10-4.5

Dives Exceeding the Normal Working Limit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-5

10-5 NITROX REPETITIVE DIVING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-5
10-6 NITROX DIVE CHARTING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-5
10-7 FLEET TRAINING FOR NITROX . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-7
10-8 NITROX DIVING EQUIPMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-7
10-8.1

Open-Circuit SCUBA Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-7
10-8.1.1 Regulators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-7
10-8.1.2 Bottles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-8

10-8.2

General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-8

10-8.3

Surface-Supplied NITROX Diving . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-8

10-9 EQUIPMENT CLEANLINESS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-8
10-10 BREATHING GAS PURITY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-9
10-11 NITROX MIXING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-9
10-12 NITROX MIXING, BLENDING, AND STORAGE SYSTEMS . . . . . . . . . . . . . . . . . . . . . . . . . . 10-12

11

ICE AND COLD WATER DIVING OPERATIONS

11-1

INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-1

11-2

11-1.1

Purpose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-1

11-1.2

Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-1

11-1.3

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-1

OPERATIONS PLANNING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-1
11-2.1

Planning Guidelines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-1

11-2.2

Navigational Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-2

11-2.3

SCUBA Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-2

11-2.4

SCUBA Regulators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-3
11-2.4.1
11-2.4.2

Special Precautions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-4
Redundant Air Sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-4

11-2.5

Life Preserver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-5

11-2.6

Face Mask. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-5

11-2.7

SCUBA Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-5

11-2.8

Surface-Supplied Diving System (SSDS) Considerations . . . . . . . . . . . . . . . . . . . . . . 11-5
11-2.8.1 Advantages and Disadvantages of SSDS . . . . . . . . . . . . . . . . . . . . . . . . . . 11-6
11-2.8.2 Effect of Ice Conditions on SSDS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-6

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11-2.9

Suit Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-7
11-2.9.1
11-2.9.2
11-2.9.3

Wet Suits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-7
Variable Volume Dry Suits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-7
Extreme Exposure Suits/Hot Water Suits . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-8

11-2.10 Clothing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-8
11-2.11 Ancillary Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-9
11-2.12 Dive Site Shelter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-9
11-3

11-4

11-5

2A

PREDIVE PROCEDURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-10
11-3.1

Personnel Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-10

11-3.2

Dive Site Selection Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-10

11-3.3

Shelter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-10

11-3.4

Entry Hole . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-10

11-3.5

Escape Holes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-12

11-3.6

Navigation Lines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-12

11-3.7

Lifelines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-12

11-3.8

Equipment Preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-12

OPERATING PRECAUTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-13
11-4.1

General Precautions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-13

11-4.2

Ice Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-13

11-4.3

Dressing Precautions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-14

11-4.4

On-Surface Precautions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-14

11-4.5

In-Water Precautions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-15

11-4.6

Postdive Precautions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-15

EMERGENCY PROCEDURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-15
11-5.1

Lost Diver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-15

11-5.2

Searching for a Lost Diver. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-16

11-5.3

Hypothermia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-16

OPTIONAL SHALLOW WATER DIVING TABLES

2A-1 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2A-1

2B

U.S. NAVY DIVE COMPUTER

2B-1 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2B-1
2B-1.1

Purpose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2B-1

2B-1.2

Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2B-1

2B-2 PRINCIPLES OF OPERATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2B-1

xx

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Chap/Para

Page
2B-2.1

Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2B-2

2B-2.2

Function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2B-2

2B-2.3

Safety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2B-3

2B-2.4

Advantages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2B-3

2B-2.5

Disadvantages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2B-3

2B-2.6

Use . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2B-4

2B-3 DIVING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2B-5
2B-3.1

Pre-Dive . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2B-5

2B-3.2

Dive . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2B-5

2B-3.3

Ascent . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2B-6

2B-3.4

Decompression . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2B-6

2B-3.5

Post-Dive. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2B-6

2B-3.6

Time to Fly/Ascent to Altitude . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2B-7

2B-3.7

Repetitive Diving . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2B-7

2B-4 DIVING ISSUES/EPS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2B-7
2B-4.1

Loss of NDC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2B-7

2B-4.2

Asymptomatic Omitted Decompression . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2B-7
2B-4.2.1 In Water Stops Missed Without Surfacing . . . . . . . . . . . . . . . . . . . . . . . . . . 2B-8
2B-4.2.2 Inadvertent Surfacing with Missed Last or Only Stop. . . . . . . . . . . . . . . . . . 2B-8
2B-4.2.3 Inadvertent Surfacing with Multiple Missed Stops . . . . . . . . . . . . . . . . . . . . 2B-9

2C

2B-4.3

In-Water DCS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2B-9

2B-4.4

Exceeds Limits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2B-9

ENVIRONMENTAL AND OPERATIONAL HAZARDS

2C-1 ENVIRONMENTAL HAZARDS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2C-1
2C-2 OPERATIONAL HAZARDS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2C-11

2D

GUIDANCE FOR U.S. NAVY DIVING ON A DYNAMIC POSITIONING VESSEL

2D-1 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2D-1
2D-2 DYNAMIC POSITIONING (DP) CAPABILITY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2D-1
2D-2.1 DP Advantages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2D-2
2D-2.2 DP Disadvantages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2D-2
2D-2.3 DP Classification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2D-3
2D-2.3.1 Classification Societies. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2D-3
2D-2.4 DP System Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2D-3
2D-2.4.1 Sensors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2D-4

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2D-2.4.2 Thrusters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2D-4
2D-2.4.3 Control Stations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2D-5
2D-2.4.4 Computers and Software . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2D-6
2D-2.4.5 Failure Modes and Effects Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2D-6
2D-2.4.6 DP Trials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2D-6
2D-2.4.7 DP Status Lights and Alarms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2D-6
2D-2.4.8 DP Vessel Communications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2D-7
2D-2.4.9 Operations Plot and Emergency Plans . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2D-7
2D-2.4.10 Authority and Responsibility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2D-7
2D-2.4.11 DP Casualties. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2D-8

2D-3 GUIDELINES TO DETERMINE THE SUITABILITY OF A DP VESSEL . . . . . . . . . . . . . . . . . . . 2D-8
2D-3.1 VOO Selection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2D-8
2D-3.1.1 Vessel Suitability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2D-8
2D-4 GUIDELINES FOR ESTABLISHING AN OPERATIONAL PLAN FOR THE DP VESSEL . . . .2D-10
2D-5 SPECIFIC GUIDELINES FOR SURFACE SUPPLIED DIVING WHILE OPERATING FROM A
VESSEL IN THE DP MODE. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2D-10
2D-5.1 Surface Supplied Diving . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2D-11
2D-5.2 Umbilical Management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2D-11
2D-5.3 Surface Diving Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2D-12
2D-5.3.1 Additional Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2D-15
2D-5.4 Selection of DP Vessels of Opportunity for Diving Operations . . . . . . . . . . . . . . . . . .2D-16

12

SURFACE-SUPPLIED MIXED-GAS DIVING DIVING

12-1 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-1
12-1.1

Purpose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-1

12-1.2

Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-1

12-2 OPERATIONAL CONSIDERATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-1
12-2.1

Limits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-1

12-2.2

Personnel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-2

12-2.3

Additional Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-2
12-2.3.1 Emergency Gas Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-3
12-2.3.2 Water Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-3
12-2.3.3 Diver Training . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-3
12-2.3.4 Diver Fatigue . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-3
12-2.3.5 Ascent to Altitude . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-3

12-3 MIXED GAS DIVING EQUIPMENT/SYSTEMS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-3

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12-3.1

Gas Mixtures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-4

12-3.2

Flyaway Dive System (FADS) III Mixed Gas System (FMGS) . . . . . . . . . . . . . . . . . . . 12-4

12-4 SURFACE-SUPPLIED HELIUM-OXYGEN DESCENT AND ASCENT PROCEDURES . . . . . . 12-4
12-4.1

Selecting the Bottom Mix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-6

12-4.2

Selecting the Decompression Schedule . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-6

12-4.3

Travel Rates and Stop Times . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-7

12-4.4

Decompression Breathing Gases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-7

12-4.5

Special Procedures for Descent with Less than 16 Percent Oxygen . . . . . . . . . . . . . . 12-7

12-4.6

Aborting Dive During Descent . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-8

12-4.7

Procedures for Shifting to 50 Percent Helium/50 Percent Oxygen at 90 fsw . . . . . . . . 12-9

12-4.8

Procedures for Shifting to 100 Percent Oxygen at 30 fsw . . . . . . . . . . . . . . . . . . . . . . 12-9

12-4.9

Air Breaks at 30 and 20 fsw . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-9

12-4.10 Ascent from the 20-fsw Water Stop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-10
12-4.11 Surface Decompression on Oxygen (SurDO2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-10
12-4.12 Variation in Rate of Ascent . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-11
12-4.12.1 Early Arrival at the First Stop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-11
12-4.12.2 Delays in Arriving at the First Stop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-11
12-4.12.3 Delays in Leaving a Stop or Arrival at the Next Stop . . . . . . . . . . . . . . . . . 12-11
12-4.12.4 Delays in Travel from 40 fsw to the Surface for Surface Decompression. . 12-12
12-5 SURFACE-SUPPLIED HELIUM-OXYGEN EMERGENCY PROCEDURES . . . . . . . . . . . . . . 12-12
12-5.1

Bottom Time in Excess of the Table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-12

12-5.2

Loss of Helium-Oxygen Supply on the Bottom . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-13

12-5.3

Loss of 50 Percent Oxygen Supply During In-Water Decompression . . . . . . . . . . . . 12-13

12-5.4

Loss of Oxygen Supply During In-Water Decompression . . . . . . . . . . . . . . . . . . . . . . 12-13

12-5.5

Loss of Oxygen Supply in the Chamber During Surface Decompression. . . . . . . . . . 12-14

12-5.6

Decompression Gas Supply Contamination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-15

12-5.7

CNS Oxygen Toxicity Symptoms (Nonconvulsive) at the 90-60 fsw Water Stops . . . 12-15

12-5.8

Oxygen Convulsion at the 90-60 fsw Water Stop. . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-16

12-5.9

CNS Toxicity Symptoms (Nonconvulsive) at 50-and 40-fsw Water Stops... . . . . . . . . 12-17

12-5.10 Oxygen Convulsion at the 50-40 fsw Water Stop . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-18
12-5.11 CNS Oxygen Toxicity Symptoms (Nonconvulsive) at 30- and 20-fsw Water Stops... . 12-18
12-5.12 Oxygen Convulsion at the 30- and 20-fsw Water Stop . . . . . . . . . . . . . . . . . . . . . . . . 12-19
12-5.13 Oxygen Toxicity Symptoms in the Chamber . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-19
12-5.14 Surface Interval Greater than 5 Minutes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-19
12-5.15 Asymptomatic Omitted Decompression. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-20
12-5.15.1 Omitted Decompression Stop Deeper Than 50 fsw . . . . . . . . . . . . . . . . . . 12-21
12-5.16 Symptomatic Omitted Decompression . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-22
12-5.17 Light Headed or Dizzy Diver on the Bottom . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-22

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12-5.17.1 Initial Management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-22
12-5.17.2 Vertigo . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-22
12-5.18 Unconscious Diver on the Bottom . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-23
12-5.19 Decompression Sickness in the Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-24
12-5.19.1 Decompression Sickness Deeper than 30 fsw . . . . . . . . . . . . . . . . . . . . . . 12-24
12-5.19.2 Decompression Sickness at 30 fsw and Shallower . . . . . . . . . . . . . . . . . . 12-24
12-5.20 Decompression Sickness During the Surface Interval . . . . . . . . . . . . . . . . . . . . . . . . 12-25

12-6 CHARTING SURFACE SUPPLIED HELIUM OXYGEN DIVES . . . . . . . . . . . . . . . . . . . . . . . . 12-25
12-6.1

Charting an HeO2 Dive. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-25

12-7 DIVING AT ALTITUDE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-26

13

SATURATION DIVING

13-1 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-1
13-1.1

Purpose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-1

13-1.2

Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-1

13-2 DEEP DIVING SYSTEMS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-1
13-2.1

Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-1

13-3 BASIC COMPONENTS OF THE U.S. NAVY FLY AWAY SATURATION DIVE SYSTEM . . . . . 13-2
13-3.1

Dive Bell . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-2
13-3.1.1
13-3.1.2
13-3.1.3
13-3.1.4
13-3.1.5
13-3.1.6
13-3.1.7

13-3.2

Deck Decompression Chamber (DDC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-5
13-3.2.1
13-3.2.2
13-3.2.3
13-3.2.4
13-3.2.5

13-3.3

Gas Supplies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-3
Dive Bell Pressurization/Depressurization System . . . . . . . . . . . . . . . . . . . 13-3
Dive Bell Life-Support System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-3
Electrical System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-3
Communications System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-4
Dive Bell Umbilical . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-5
Diver Hot Water System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-5

DDC Life-Support System (LSS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-5
Potable Water/Sanitary System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-5
Fire Suppression System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-5
Control Van (Control) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-5
Gas Supply Mixing and Storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-6

Dive Bell Launch and Recovery System (LARS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-6
13-3.3.1 SAT FADS LARS Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-6

13-3.4

Saturation Mixed-Gas Diving Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-7

13-4 U.S. NAVY SHORE BASED SATURATION FACILITIES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-7
13-4.1

Navy Experimental Diving Unit (NEDU), Panama City, FL . . . . . . . . . . . . . . . . . . . . . . 13-7

13-5 DIVER LIFE-SUPPORT SYSTEMS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-8

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13-5.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-8

13-6 THERMAL PROTECTION SYSTEM. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-10
13-6.1

Diver Heating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-10

13-6.2

Inspired Gas Heating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-10

13-7 SATURATION DIVING UNDERWATER BREATHING APPARATUS . . . . . . . . . . . . . . . . . . . . 13-11
13-7.1

Commercial Off-the-Shelf Closed-Circuit UBA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-11

13-8 UBA GAS USAGE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-12
13-8.1

Specific Dives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-12

13-8.2

Emergency Gas Supply Duration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-13

13-8.3

Gas Composition. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-14

13-9 SATURATION DIVING OPERATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-15
13-9.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-15

13-10 OPERATIONAL CONSIDERATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-15
13-10.1 Dive Team Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-15
13-10.2 Mission Training . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-15
13-11 SELECTION OF STORAGE DEPTH . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-16
13-12 RECORDS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-16
13-12.1 Command Diving Log . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-16
13-12.2 Master Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-17
13-12.2.1 Modifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-17
13-12.2.2 Elements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-17
13-12.3 Chamber Atmosphere Data Sheet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-17
13-12.4 Service Lock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-17
13-12.5 Machinery Log/Gas Status Report . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-17
13-12.6 Operational Procedures (OPs). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-18
13-12.7 Emergency Procedures (EPs). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-18
13-13 LOGISTICS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-18
13-14 DDC AND PTC ATMOSPHERE CONTROL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-18
13-15 GAS SUPPLY REQUIREMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-19
13-15.1 UBA Gas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-19
13-15.2 Emergency Gas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-19
13-15.3 Treatment Gases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-20
13-16 ENVIRONMENTAL CONTROL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-20
13-17 FIRE ZONE CONSIDERATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-21

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13-18 HYGIENE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-22
13-18.1 Personal Hygiene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-22
13-18.2 Prevention of External Ear Infections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-22
13-18.3 Chamber Cleanliness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-22
13-18.4 Food Preparation and Handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-23
13-19 ATMOSPHERE QUALITY CONTROL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-23
13-19.1 Gaseous Contaminants. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-23
13-19.2 Initial Unmanned Screening Procedures. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-23
13-20 COMPRESSION PHASE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-24
13-20.1 Establishing Chamber Oxygen Partial Pressure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-25
13-20.2 Compression to Storage Depth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-26
13-20.3 Precautions During Compression . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-27
13-20.4 Abort Procedures During Compression . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-27
13-21 STORAGE DEPTH . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-27
13-21.1 Excursion Table Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-31
13-21.2 Dive Bell Diving Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-32
13-21.2.1 Dive Bell Deployment Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-32
13-22 DEEP DIVING SYSTEM (DDS) EMERGENCY PROCEDURES . . . . . . . . . . . . . . . . . . . . . . . 13-33
13-22.1 Loss of Chamber Atmosphere Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-34
13-22.1.1
13-22.1.2
13-22.1.3
13-22.1.4
13-22.1.5

Loss of Oxygen Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-34
Loss of Carbon Dioxide Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-34
Atmosphere Contamination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-34
Interpretation of the Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-34
Loss of Temperature Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-35

13-22.2 Loss of Depth Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-35
13-22.3 Fire in the DDC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-35
13-22.4 Dive Bell Emergencies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-36
13-23 SATURATION DECOMPRESSION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-36
13-23.1 Upward Excursion Depth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-36
13-23.2 Travel Rate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-36
13-23.3 Post-Excursion Hold . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-36
13-23.4 Rest Stops. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-36
13-23.5 Saturation Decompression Rates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-36
13-23.6 Atmosphere Control at Shallow Depths . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-37
13-23.7 Saturation Dive Mission Abort . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-38
13-23.7.1 Emergency Cases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-38
13-23.7.2 Emergency Abort Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-39
13-23.8 Decompression Sickness (DCS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-40

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13-23.8.1 Type I Decompression Sickness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-40
13-23.8.2 Type II Decompression Sickness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-40

13-24 POSTDIVE PROCEDURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-41

14

BREATHING GAS MIXING PROCEDURES

14-1 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14-1
14-1.1

Purpose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14-1

14-1.2

Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14-1

14-2 MIXING PROCEDURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14-1
14-2.1

Mixing by Partial Pressure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14-1

14-2.2

Ideal-Gas Method Mixing Procedure. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14-2

14-2.3

Adjustment of Oxygen Percentage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14-5
14-2.3.1 Increasing the Oxygen Percentage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14-5
14-2.3.2 Reducing the Oxygen Percentage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14-6

14-2.4

Continuous-Flow Mixing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14-7

14-2.5

Mixing by Volume . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14-7

14-2.6

Mixing by Weight . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14-8

14-3 GAS ANALYSIS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14-8

15

14-3.1

Instrument Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14-9

14-3.2

Techniques for Analyzing Constituents of a Gas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14-9

ELECTRONICALLY CONTROLLED CLOSED-CIRCUIT UNDERWATER BREATHING
APPARATUS (EC-UBA) DIVING

15-1 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-1
15-1.1

Purpose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-1

15-1.2

Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-1

15-2 PRINCIPLES OF OPERATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-1
15-2.1

Diving Safety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-2

15-2.2

Advantages of EC-UBA. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-3

15-2.3

Recirculation and Carbon Dioxide Removal. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-3
15-2.3.1 Recirculating Gas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-3
15-2.3.2 Full Face Mask . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-3
15-2.3.3 Carbon Dioxide Scrubber . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-3
15-2.3.4 Diaphragm Assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-4
15-2.3.5 Recirculation System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-4
15-2.3.6 Gas Addition, Exhaust, and Monitoring . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-5

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15-3 OPERATIONAL PLANNING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-5
15-3.1

Operational Limitations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-7
15-3.1.1 Oxygen Flask Endurance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-8
15-3.1.2 Effect of Cold Water Immersion on Flask Pressure . . . . . . . . . . . . . . . . . . . 15-8
15-3.1.3 Diluent Flask Endurance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-8
15-3.1.4 Canister Duration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-9
15-3.1.5 Human Physiological Limits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-9

15-3.2

Equipment Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-9
15-3.2.1
15-3.2.2
15-3.2.3
15-3.2.4
15-3.2.5
15-3.2.6
15-3.2.7
15-3.2.8
15-3.2.9
15-3.2.10
15-3.2.11
15-3.2.12

Safety Boat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-9
Buddy Lines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-9
Distance Line . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-9
Standby Diver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-9
Tending Lines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-10
Marking of Lines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-10
Diver Marker Buoy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-10
Depth Gauge/Wrist Watch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-10
NDC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-11
Thermal Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-11
Full Face Mask (FFM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-11
Emergency Breathing System (EBS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-11

15-3.3

Recompression Chamber Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-11

15-3.4

Diving Procedures for EC-UBA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-13
15-3.4.1 Diving Methods. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-13

15-3.5

Diving in Contaminated Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-15

15-3.6

Special Diving Situations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-15

15-4 PREDIVE PROCEDURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-15
15-4.1

Diving Supervisor Brief . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-15

15-4.2

Diving Supervisor Check . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-15

15-5 DESCENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-17
15-6 UNDERWATER PROCEDURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-17
15-6.1

General Guidelines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-17

15-6.2

At Depthf . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-18

15-7 ASCENT PROCEDURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-18
15-8 DECOMPRESSION PROCEDURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-18
15-8.1

Monitoring ppO2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-18

15-8.2

Rules for Using EC-UBA Decompression Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-19

15-8.3

PPO2 Variances. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-22

15-8.4

Emergency Breathing System (EBS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-22
15-8.4.1 EBS Deployment Procedures. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-22
15-8.4.2 EBS Ascent Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-23

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15-9 MULTI-DAY DIVING FOR 1.3 ATA PPO2 EC-UBA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-23
15-10 ALTITUDE DIVING PROCEDURES AND FLYING AFTER DIVING . . . . . . . . . . . . . . . . . . . . 15-23
15-11 POSTDIVE PROCEDURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-24
15-12 MEDICAL ASPECTS OF CLOSED-CIRCUIT MIXED-GAS UBA . . . . . . . . . . . . . . . . . . . . . . 15-24
15-12.1 Central Nervous System (CNS) Oxygen Toxicity . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-24
15-12.1.1 Causes of CNS Oxygen Toxicity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-24
15-12.1.2 Symptoms of CNS Oxygen Toxicity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-25
15-12.1.3 Treatment of Nonconvulsive Symptoms . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-25
15-12.1.4 Treatment of Underwater Convulsion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-25
15-12.1.5 Prevention of CNS Oxygen Toxicity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-26
15-12.1.6 Off-Effect . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-26
15-12.2 Pulmonary Oxygen Toxicity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-26
15-12.3 Oxygen Deficiency (Hypoxia) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-26
15-12.3.1 Causes of Hypoxia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-26
15-12.3.2 Symptoms of Hypoxia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-27
15-12.3.3 Treating Hypoxia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-27
15-12.3.4 Treatment of Hypoxic Divers Requiring Decompression . . . . . . . . . . . . . . 15-27
15-12.4 Carbon Dioxide Toxicity (Hypercapnia) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-27
15-12.4.1 Causes of Hypercapnia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-27
15-12.4.2 Symptoms of Hypercapnia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-27
15-12.4.3 Treating Hypercapnia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-28
15-12.4.4 Prevention of Hypercapnia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-28
15-12.5 Chemical Injury . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-29
15-12.5.1 Causes of Chemical Injury . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-29
15-12.5.2 Symptoms of Chemical Injury. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-29
15-12.5.3 Management of a Chemical Incident . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-29
15-12.5.4 Prevention of Chemical Injury . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-30
15-12.6 Omitted Decompression . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-30
15-12.6.1 At 20 fsw. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-30
15-12.6.2 Deeper than 20 fsw . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-30
15-12.6.3 Deeper than 20 fsw Recompression Chamber not Available Within 60min 15-31
15-12.6.4 Evidence of Decompression Sickness or Arterial Gas Embolismin . . . . . . 15-32
15-12.7 Decompression Sickness in the Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-32
15-12.7.1 Diver Remaining in Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-32
15-12.7.2 Diver Leaving the Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-32
15-13 EC-UBA DIVING EQUIPMENT REFERENCE DATA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-32

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CLOSED-CIRCUIT OXYGEN UBA (CC-UBA) DIVING

16-1 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-1
16-1.1

Purpose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-1

16-1.2

Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-1

16-2 MEDICAL ASPECTS OF CLOSED-CIRCUIT OXYGEN DIVING . . . . . . . . . . . . . . . . . . . . . . . . 16-1
16-2.1

Central Nervous System (CNS) Oxygen Toxicity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-2
16-2.1.1 Symptoms of CNS Oxygen Toxicity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-2
16-2.1.2 Treatment of Nonconvulsive Symptoms . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-2
16-2.1.3 Treatment of Underwater Convulsion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-2
16-2.1.4 Off-Effect . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-3

16-2.2

Pulmonary Oxygen Toxicity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-3

16-2.3

Oxygen Deficiency (Hypoxia) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-3
16-2.3.1
16-2.3.2
16-2.3.3
16-2.3.4
16-2.3.5

16-2.4

Causes of Hypoxia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-3
UBA Purge Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-3
Underwater Purge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-4
Symptoms of Hypoxia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-4
Treatment of Hypoxia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-4

Carbon Dioxide Toxicity (Hypercapnia) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-4
16-2.4.1 Treating Hypercapnia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-4
16-2.4.2 Prevention of Hypercapnia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-5

16-2.5

Chemical Injury . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-5
16-2.5.1 Causes of Chemical Injury . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-5
16-2.5.2 Symptoms of Chemical Injury. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-5
16-2.5.3 Treatment of a Chemical Incident . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-6
16-2.5.4 Prevention of Chemical Injury . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-6

16-2.6

Middle Ear Oxygen Absorption Syndrome . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-6
16-2.6.1 Causes of Middle Ear Oxygen Absorption Syndrome . . . . . . . . . . . . . . . . . 16-6
16-2.6.2 Symptoms of Middle Ear Oxygen Absorption Syndrome . . . . . . . . . . . . . . . 16-6
16-2.6.3 Treating Middle Ear Oxygen Absorption Syndrome . . . . . . . . . . . . . . . . . . . 16-7
16-2.6.4 Prevention of Middle Ear Oxygen Absorption Syndrome . . . . . . . . . . . . . . . 16-7

16-3 CLOSED-CIRCUIT OXYGEN EXPOSURE LIMITS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-7
16-3.1

Transit with Excursion Limits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-7
16-3.1.1 Transit with Excursion Limits Table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-7
16-3.1.2 Transit with Excursion Limits Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-8
16-3.1.3 Transit with Excursion Rules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-9
16-3.1.4 Inadvertent Excursions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-9

16-3.2

Single-Depth Limits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-10
16-3.2.1 Single-Depth Oxygen Exposure Limits Table . . . . . . . . . . . . . . . . . . . . . . . 16-10
16-3.2.2 Single-Depth Limits Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-10

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16-3.2.3 Depth/Time Limits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-10
16-3.3

Lock Out/In from Excursion Depth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-10

16-3.4

Exposure Limits for Successive Oxygen Dives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-11
16-3.4.1 Definitions for Successive Oxygen Dives . . . . . . . . . . . . . . . . . . . . . . . . . . 16-11
16-3.4.2 Off-Oxygen Exposure Limit Adjustments . . . . . . . . . . . . . . . . . . . . . . . . . . 16-11

16-3.5

Exposure Limits for Successive Oxygen Dives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-12
16-3.5.1 Mixed-Gas to Oxygen Rule . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-12
16-3.5.2 Oxygen to Mixed-Gas Rule . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-12

16-3.6

Oxygen Diving at High Elevations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-13

16-3.7

Flying After Oxygen Diving . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-13

16-3.8

Combat Operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-13

16-4 OPERATIONS PLANNING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-13
16-4.1

Operating Limitations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-13

16-4.2

Maximizing Operational Range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-13

16-4.3

Training . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-14

16-4.4

Personnel Requirements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-14

16-4.5

Equipment Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-15

16-4.6

Predive Precautions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-16

16-5 PREDIVE PROCEDURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-17
16-5.1

Equipment Preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-17

16-5.2

Diving Supervisor Brief . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-17

16-5.3

Diving Supervisor Check . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-17
16-5.3.1 First Phase . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-17
16-5.3.2 Second Phase . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-17

16-6 WATER ENTRY AND DESCENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-18
16-6.1

Purge Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-18

16-6.2

Avoiding Purge Procedure Errors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-18

16-7 UNDERWATER PROCEDURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-19
16-7.1

General Guidelines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-19

16-7.2

UBA Malfunction Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-20

16-8 ASCENT PROCEDURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-20
16-9 POSTDIVE PROCEDURES AND DIVE DOCUMENTATION . . . . . . . . . . . . . . . . . . . . . . . . . . 16-20
16-10 MK-25 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-21

17

DIAGNOSIS AND TREATMENT OF DECOMPRESSION SICKNESS AND
ARTERIAL GAS EMBOLISM

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17-1 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-1
17-1.1

Purpose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-1

17-1.2

Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-1

17-2 MANNING REQUIREMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-1
17-2.1

Recompression Chamber Team . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-1

17-2.2

Diving Officer. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-2

17-2.3

Master Diver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-3

17-2.4

Chamber Supervisor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-3

17-2.5

Diving Medical Officer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-3
17-2.5.1 Prescribing and Modifying Treatments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-4

17-2.6

Inside Tender/DMT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-4

17-2.7

Outside Tender . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-5

17-2.8

Emergency Consultation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-5

17-3 ARTERIAL GAS EMBOLISM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-6
17-3.1

Diagnosis of Arterial Gas Embolism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-6
17-3.1.1 Symptoms of AGE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-7

17-3.2

Treating Arterial Gas Embolism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-7

17-3.3

Resuscitation of a Pulseless Diver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-7
17-3.3.1 Evacuation not Feasible . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-8

17-4 DECOMPRESSION SICKNESS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-8
17-4.1

Diagnosis of Decompression Sickness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-9

17-4.2

Symptoms of Type I Decompression Sickness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-9
17-4.2.1 Musculoskeletal Pain-Only Symptoms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-9
17-4.2.2 Cutaneous (Skin) Symptoms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-11
17-4.2.3 Lymphatic Symptoms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-11

17-4.3

Treatment of Type I Decompression Sickness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-11

17-4.4

Symptoms of Type II Decompression Sickness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-11
17-4.4.1
17-4.4.2
17-4.4.3
17-4.4.4

Neurological Symptoms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-11
Inner Ear Symptoms (“Staggers”) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-12
Cardiopulmonary Symptoms (“Chokes”) . . . . . . . . . . . . . . . . . . . . . . . . . . 17-12
Differentiating Between Type II DCS and AGE . . . . . . . . . . . . . . . . . . . . . 17-12

17-4.5

Treatment of Type II Decompression Sickness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-12

17-4.6

Decompression Sickness in the Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-13

17-4.7

Symptomatic Omitted Decompression . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-13

17-4.8

Altitude Decompression Sickness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-13
17-4.8.1 Joint Pain Treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-13
17-4.8.2 Other Symptoms and Persistent Symptoms . . . . . . . . . . . . . . . . . . . . . . . 17-13

17-5 RECOMPRESSION TREATMENT FOR DIVING DISORDERS . . . . . . . . . . . . . . . . . . . . . . . . 17-14

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17-5.1

Primary Objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-14

17-5.2

Guidance on Recompression Treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17-14

17-5.3

Recompression Treatment When Chamber Is Available. . . . . . . . . . . . . . . . . . . . . . . .17-14
17-5.3.1 Recompression Treatment with Oxygen . . . . . . . . . . . . . . . . . . . . . . . . . . 17-14
17-5.3.2 Recompression Treatments When Oxygen Is Not Available . . . . . . . . . . . 17-14

17-5.4

Recompression Treatment When No Recompression Chamber is Available . . . . . . .17-15
17-5.4.1 Transporting the Patient . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-15
17-5.4.2 In-Water Recompression . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-16

17-6 TREATMENT TABLES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-17
17-6.1

Air Treatment Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-17

17-6.2

Treatment Table 5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17-17

17-6.3

Treatment Table 6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17-18

17-6.4

Treatment Table 6A. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17-18

17-6.5

Treatment Table 4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17-18

17-6.6

Treatment Table 7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17-19
17-6.6.1 Decompression . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-19
17-6.6.2 Tenders. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-20
17-6.6.3 Preventing Inadvertent Early Surfacing . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-20
17-6.6.4 Oxygen Breathing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-20
17-6.6.5 Sleeping, Resting, and Eating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-20
17-6.6.6 Ancillary Care . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-20
17-6.6.7 Life Support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-21

17-6.7

Treatment Table 8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17-21

17-6.8

Treatment Table 9. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17-21

17-7 RECOMPRESSION TREATMENT FOR NON-DIVING DISORDERS . . . . . . . . . . . . . . . . . . . 17-21
17-8 RECOMPRESSION CHAMBER LIFE-SUPPORT CONSIDERATIONS . . . . . . . . . . . . . . . . . 17-22
17-8.1

Oxygen Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-23

17-8.2

Carbon Dioxide Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-23
17-8.2.1 Carbon Dioxide Monitoring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-22
17-8.2.2 Carbon Dioxide Scrubbing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-23
17-8.2.3 Carbon Dioxide Absorbent . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-23

17-8.3

Temperature Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-23
17-8.3.1 Patient Hydration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-24

17-8.4

Chamber Ventilation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-25

17-8.5

Access to Chamber Occupants. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-25

17-8.6

Inside Tender Oxygen Breathing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-25

17-8.7

Tending Frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-25

17-8.8

Equalizing During Descent . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-25

17-8.9

Use of High Oxygen Mixes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-25

17-8.10 Oxygen Toxicity During Treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-26
17-8.10.1 Central Nervous System Oxygen Toxicity . . . . . . . . . . . . . . . . . . . . . . . . . 17-26

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17-8.10.2 Pulmonary Oxygen Toxicity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-27
17-8.11 Loss of Oxygen During Treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-27
17-8.11.1 Compensation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-28
17-8.11.2 Switching to Air Treatment Table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-28
17-8.12 Treatment of Altitude . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-28

17-9 POST-TREATMENT CONSIDERATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-28
17-9.1

Post-Treatment Observation Period . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-28

17-9.2

Post-Treatment Transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-29

17-9.3

Flying After Treatments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-29
17-9.3.1 Emergency Air Evacuation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-30

17-9.4

Treatment of Residual Symptoms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-30

17-9.5

Returning to Diving after Recompression Treatment . . . . . . . . . . . . . . . . . . . . . . . . . 17-30

17-10 NON-STANDARD TREATMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-31
17-11 RECOMPRESSION TREATMENT ABORT PROCEDURES . . . . . . . . . . . . . . . . . . . . . . . . . . 17-31
17-11.1 Death During Treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-31
17-11.2 Impending Natural Disasters or Mechanical Failures . . . . . . . . . . . . . . . . . . . . . . . . . 17-32
17-12 ANCILLARY CARE AND ADJUNCTIVE TREATMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-32
17-12.1 Decompression Sickness. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-33
17-12.1.1
17-12.1.2
17-12.1.3
17-12.1.4
17-12.1.5
17-12.1.6
17-12.1.7

Surface Oxygen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-33
Fluids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-33
Anticoagulants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-34
Aspirin and Other Non-Steroidal Anti-Inflammatory Drugs . . . . . . . . . . . . . 17-34
Steroids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-34
Lidocaine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-34
Environmental Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-34

17-12.2 Arterial Gas Embolism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-34
17-12.2.1
17-12.2.2
17-12.2.3
17-12.2.4
17-12.2.5
17-12.2.6
17-12.2.7

Surface Oxygen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-34
Lidocaine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-34
Fluids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-35
Anticoagulants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-35
Aspirin and Other Non-Steroidal Anti-Inflammatory Drugs . . . . . . . . . . . . . 17-35
Steroids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-35
Environmental Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-35

17-12.3 Sleeping and Eating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-35
17-13 EMERGENCY MEDICAL EQUIPMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-36
17-13.1 Primary and Secondary Emergency Kits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-36
17-13.2 Portable Monitor-Defibrillator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-36
17-13.3 Advanced Cardiac Life Support Drugs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-40
17-13.4 Use of Emergency Kits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-41
17-13.4.1 Modification of Emergency Kits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-41

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Page
RECOMPRESSION CHAMBER OPERATION

18-1 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-1
18-1.1

Purpose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-1

18-1.2

Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-1

18-1.3

Chamber Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-1

18-2 DESCRIPTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-2
18-2.1

Basic Chamber Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-2

18-2.2

Fleet Modernized Double-Lock Recompression Chamber . . . . . . . . . . . . . . . . . . . . . . 18-3

18-2.3

Recompression Chamber Facility (RCF) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-3

18-2.4

Standard Navy Double Lock Recompression Chamber System (SNDLRCS) . . . . . . . 18-3

18-2.5

Transportable Recompression Chamber System (TRCS) . . . . . . . . . . . . . . . . . . . . . . 18-3

18-2.6

Fly Away Recompression Chamber (FARCC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-4

18-2.7

Emergency Evacuation Hyperbaric Stretcher (EEHS) . . . . . . . . . . . . . . . . . . . . . . . . . 18-4

18-2.8

Standard Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-4
18-2.8.1
18-2.8.2
18-2.8.3
18-2.8.4
18-2.8.5
18-2.8.6

Labeling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-4
Inlet and Exhaust Ports . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-5
Pressure Gauges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-5
Relief Valves. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-5
Communications System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-5
Lighting Fixtures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-5

18-3 STATE OF READINESS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-15
18-4 GAS SUPPLY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-15
18-4.1

Capacity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-15

18-5 OPERATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-17
18-5.1

Predive Checklist . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-17

18-5.2

Safety Precautions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-17

18-5.3

General Operating Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-17
18-5.3.1
18-5.3.2
18-5.3.3
18-5.3.4

18-5.4

Tender Change-Out . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-20
Lock-In Operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-20
Lock-Out Operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-20
Gag Valves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-20

Ventilation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-20
18-5.4.1 Chamber Ventilation Bill . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-21
18-5.4.2 Notes on Chamber Ventilation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-22

18-6 CHAMBER MAINTENANCE. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-23
18-6.1

Postdive Checklist . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-23

18-6.2

Scheduled Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-23
18-6.2.1 Inspections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-25
18-6.2.2 Corrosion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-25

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18-6.2.3
18-6.2.4
18-6.2.5
18-6.2.6

Painting Steel Chambers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-25
Recompression Chamber Paint Process Instruction . . . . . . . . . . . . . . . . . 18-29
Stainless Steel Chambers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-29
Fire Hazard Prevention . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-29

18-7 DIVER CANDIDATE PRESSURE TEST. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-30
18-7.1

Candidate Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-30
18-7.1.1 Aviation Duty Personnel. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-30

18-7.2

Procedure. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-31
18-7.2.1 References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-31

5A

NEUROLOGICAL EXAMINATION

5A-1 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5A-1
5A-2 INITIAL ASSESSMENT OF DIVING INJURIES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5A-1
5A-3 NEUROLOGICAL ASSESSMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5A-2
5A-3.1

Mental Status . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5A-5

5A-3.2

Coordination (Cerebellar/Inner Ear Function) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5A-5

5A-3.3

Cranial Nerves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5A-6

5A-3.4

Motor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5A-7
5A-3.4.1
5A-3.4.2
5A-3.4.3
5A-3.4.4

5A-3.5

Sensory Function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5A-8
5A-3.5.1
5A-3.5.2
5A-3.5.3
5A-3.5.4
5A-3.5.5
5A-3.5.6
5A-3.5.7

5A-3.6

5B

Extremity Strength . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5A-8
Muscle Size . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5A-8
Muscle Tone . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5A-8
Involuntary Movements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5A-8

Sensory Examination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5A-10
Sensations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5A-10
Instruments. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5A-10
Testing the Trunk . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5A-10
Testing Limbs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5A-10
Testing the Hands. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5A-10
Marking Abnormalities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5A-10

Deep Tendon Reflexes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5A-10

FIRST AID

5B-1 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5B-1
5B-2 CARDIOPULMONARY RESUSCITATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5B-1
5B-3 CONTROL OF MASSIVE BLEEDING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5B-1

xxxvi

5B-3.1

External Arterial Hemorrhage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5B-1

5B-3.2

Direct Pressure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5B-1

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5B-3.3

Pressure Points . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5B-1
5B-3.3.1
5B-3.3.2
5B-3.3.3
5B-3.3.4
5B-3.3.5
5B-3.3.6
5B-3.3.7
5B-3.3.8
5B-3.3.9
5B-3.3.10
5B-3.3.11
5B-3.3.12

5B-3.4

Pressure Point Location on Face . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5B-2
Pressure Point Location for Shoulder or Upper Arm . . . . . . . . . . . . . . . . . . 5B-2
Pressure Point Location for Middle Arm and Hand . . . . . . . . . . . . . . . . . . . 5B-2
Pressure Point Location for Thigh . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5B-2
Pressure Point Location for Foot . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5B-2
Pressure Point Location for Temple or Scalp . . . . . . . . . . . . . . . . . . . . . . . . 5B-2
Pressure Point Location for Neck . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5B-2
Pressure Point Location for Lower Arm . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5B-2
Pressure Point Location of the Upper Thigh . . . . . . . . . . . . . . . . . . . . . . . . 5B-2
Pressure Point Location Between Knee and Foot . . . . . . . . . . . . . . . . . . . . 5B-4
Determining Correct Pressure Point. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5B-4
When to Use Pressure Points . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5B-4

Tourniquet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5B-4
5B-3.4.1
5B-3.4.2
5B-3.4.3
5B-3.4.4

How to Make a Tourniquet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5B-4
Tightness of Tourniquet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5B-5
After Bleeding is Under Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5B-5
Points to Remember. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5B-5

5B-3.5

External Venous Hemorrhage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5B-6

5B-3.6

Internal Bleeding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5B-6
5B-3.6.1 Treatment of Internal Bleeding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5B-6

5B-4 SHOCK . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5B-6

5C

5B-4.1

Signs and Symptoms of Shock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5B-6

5B-4.2

Treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5B-7

HAZARDOUS MARINE CREATURES

5C-1 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5C-1
5C-1.1 Purpose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5C-1
5C-1.2 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5C-1
5C-2 MARINE ANIMALS THAT ATTACK . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5C-1
5C-2.1 Sharks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5C-1
5C-2.1.1 Shark Pre-Attack Behavior . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5C-1
5C-2.1.2 First Aid and Treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5C-1
5C-2.2 Killer Whales . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5C-3
5C-2.2.1 Prevention . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5C-4
5C-2.2.2 First Aid and Treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5C-4
5C-2.3 Barracuda . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5C-4
5C-2.3.1 Prevention . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5C-4
5C-2.3.2 First Aid and Treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5C-4
5C-2.4 Moray Eels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5C-4
5C-2.4.1 Prevention . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5C-5
5C-2.4.2 First Aid and Treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5C-5

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5C-2.5 Sea Lions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5C-5
5C-2.5.1 Prevention . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5C-5
5C-2.5.2 First Aid and Treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5C-5

5C-3 VENOMOUS MARINE ANIMALS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5C-6
5C-3.1 Venomous Fish (Excluding Stonefish, Zebrafish, Scorpionfish) . . . . . . . . . . . . . . . . . . 5C-6
5C-3.1.1 Prevention . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5C-6
5C-3.1.2 First Aid and Treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5C-6
5C-3.2 Highly Toxic Fish (Stonefish, Zebrafish, Scorpionfish) . . . . . . . . . . . . . . . . . . . . . . . . . 5C-7
5C-3.2.1 Prevention. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5C-7
5C-3.2.2 First Aid and Treatment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5C-7
5C-3.3 Stingrays . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5C-8
5C-3.3.1 Prevention . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5C-9
5C-3.3.2 First Aid and Treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5C-9
5C-3.4 Coelenterates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5C-9
5C-3.4.1
5C-3.4.2
5C-3.4.3
5C-3.4.4
5C-3.4.5
5C-3.4.6
5C-3.4.7

Prevention . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5C-10
Avoidance of Tentacles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5C-10
Protection Against Jellyfish. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5C-10
First Aid and Treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5C-11
Symptomatic Treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5C-11
Anaphylaxis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5C-11
Antivenin. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5C-11

5C-3.5 Coral . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5C-11
5C-3.5.1 Prevention . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5C-12
5C-3.5.2 Protection Against Coral . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5C-12
5C-3.5.3 First Aid and Treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5C-12
5C-3.6 Octopuses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5C-12
5C-3.6.1 Prevention . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5C-13
5C-3.6.2 First Aid and Treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5C-13
5C-3.7 Segmented Worms (Annelida) (Examples: Bloodworm, Bristleworm) . . . . . . . . . . . .5C-13
5C-3.7.1 Prevention . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5C-14
5C-3.7.2 First Aid and Treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5C-14
5C-3.8 Sea Urchins. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5C-14
5C-3.8.1 Prevention. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5C-14
5C-3.8.2 First Aid and Treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5C-14
5C-3.9 Cone Snails . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5C-15
5C-3.9.1 Prevention . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5C-15
5C-3.9.2 First Aid and Treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5C-15
5C-3.10 Sea Snakes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5C-16
5C-3.10.1 Sea Snake Bite Effects. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5C-16
5C-3.10.2 Prevention . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5C-16
5C-3.10.3 First Aid and Treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5C-17
5C-3.11 Sponges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5C-17
5C-3.11.1 Prevention . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5C-17
5C-3.11.2 First Aid and Treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5C-18

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5C-4 POISONOUS MARINE ANIMALS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5C-18
5C-4.1 Ciguatera Fish Poisoning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5C-18
5C-4.1.1 Prevention . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5C-18
5C-4.1.2 First Aid and Treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5C-18
5C-4.2 Scombroid Fish Poisoning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5C-19
5C-4.2.1 Prevention . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5C-19
5C-4.2.2 First Aid and Treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5C-19
5C-4.3 Puffer (Fugu) Fish Poisoning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5C-19
5C-4.3.1 Prevention . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5C-19
5C-4.3.2 First Aid and Treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5C-19
5C-4.4 Paralytic Shellfish Poisoning (PSP) (Red Tide). . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5C-20
5C-4.4.1 Symptoms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5C-20
5C-4.4.2 Prevention . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5C-20
5C-4.4.3 First Aid and Treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5C-20
5C-4.5 Bacterial and Viral Diseases from Shellfish . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5C-21
5C-4.5.1 Prevention . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5C-21
5C-4.5.2 First Aid and Treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5C-21
5C-4.6 Sea Cucumbers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5C-21
5C-4.6.1 Prevention . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5C-21
5C-4.6.2 First Aid and Treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5C-21
5C-4.7 Parasitic Infestation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5C-21
5C-4.7.1 Prevention . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5C-21
5C-5 REFERENCES FOR ADDITIONAL INFORMATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5C-22

List of Illustrations

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PAGE LEFT BLANK INTENTIONALLY

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Page
List of Illustrations

Figure

Page

1-1

Early Impractical Breathing Device . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2

1-2

Assyrian Frieze (900 B.C.) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2

1-3

Engraving of Halley’s Diving Bell . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-4

1-4

Lethbridge’s Diving Suit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-4

1-5

Siebe’s First Enclosed Diving Dress and Helmet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5

1-6

French Caisson . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5

1-7

Armored Diving Suit. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-7

1-8

MK 12 and MK V . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-9

1-9

Fleuss Apparatus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-11

1-10

Original Davis Submerged Escape Apparatus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-13

1-11

Lambertsen Amphibious Respiratory Unit (LARU) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-14

1-12

Emerson-Lambertsen Oxygen Rebreather . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-15

1-13

Draeger LAR V UBA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-15

1-14

Helium-Oxygen Diving Manifold . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-17

1-15

MK V MOD 1 Helmet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-18

1-16

MK 1 MOD 0 Diving Outfit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-20

1-17

Sealab II . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-23

1-18

U.S. Navy’s First DDS, SDS-450. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-23

1-19

DDS MK 1 Personnel Transfer Capsule . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-25

1-20

PTC Handling System, Elk River. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-25

1-21

Recovery of the Squalus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-28

2-1

Molecules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2

2-2

The Three States of Matter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2

2-3

Temperature Scales. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-3

2-4

The Six Forms of Energy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-4

2-5

Objects Underwater Appear Closer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-5

2-6

Kinetic Energy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-17

2-7

Depth, Pressure, Atmosphere Graph . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-37

3-1

The Heart’s Components and Blood Flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-3

3-2

Respiration and Blood Circulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-4

3-3

Inspiration Process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-7

3-4

Lungs Viewed from Medical Aspect. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-7

3-5

Lung Volumes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-8

List of Illustrations

xli

Figure

xlii

Page

3-6

Oxygen Consumption and RMV at Different Work Rates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-12

3-7

Gross Anatomy of the Ear in Frontal Section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-23

3-8

Location of the Sinuses in the Human Skull . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-26

3-9

Components of the Middle/Inner Ear . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-28

3-10

Pulmonary Overinflation Syndromes (POIS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-32

3-11

Arterial Gas Embolism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-33

3-12

Mediastinal Emphysema . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-36

3-13

Subcutaneous Emphysema. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-37

3-14

Pneumothorax . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-38

3-15

Tension Pneumothorax . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-39

3-16

Saturation of Tissues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-47

3-17

Desaturation of Tissues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-49

5-1

Equipment Mishap Information Sheet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-9

1A-1

Sonar Safe Diving Distance/Exposure Time Worksheet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1A-4

1A-2

Sonar Safe Diving Distance/Exposure Time Worksheet (Completed Example) . . . . . . . . . . . . . 1A-8

1A-3

Sonar Safe Diving Distance/Exposure Time Worksheet (Completed Example) . . . . . . . . . . . . . 1A-9

1A-4

Sonar Safe Diving Distance/Exposure Time Worksheet (Completed Example) . . . . . . . . . . . . 1A-10

1A-5

Sonar Safe Diving Distance/Exposure Time Worksheet (Completed Example) . . . . . . . . . . . . 1A-11

6-1

Underwater Ship Husbandry Diving . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-3

6-2

Salvage Diving. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-4

6-3

Explosive Ordnance Disposal Diving. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-6

6-4

Underwater Construction Diving . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-8

6-5

Dive Techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-11

6-6

Planning Data Sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-13

6-7

Link Between Time Critical and Deliberate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-17

6-8

Emergency Assistance Checklist. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-29

6-9

Diving Planning ORM Worksheet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-30

6-10

Ship Repair Safety Checklist for Diving . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-33

7-1

Normal and Maximum Limits for SCUBA Diving . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-2

7-2

SCUBA General Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-3

7-3

Minimum Manning Levels for SCUBA Diving . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-4

7-4

Schematic of Demand Regulator. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-9

7-5

Full Face Mask . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-10

7-6

Typical Gas Cylinder Identification Markings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-11

7-7

Life Preserver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-15

U.S. Navy Diving Manual

Figure

Page

7-8

Protective Clothing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-18

7-9

Cascading System for Charging SCUBA Cylinders. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-25

7-10

SCUBA Entry Techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-33

7-11

SCUBA Diving Operations Setup Checklist . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-34

7-12

Dive Supervisor Pre-Dive Checklist. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-37

7-13

Clearing a Face Mask . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-40

7-14

SCUBA Hand Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-41

8-1

Normal and Maximum Limits for Surface Supplied Air Diving . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-2

8-2

Minimum Qualified Divers for Surface Supplied Air Diving Stations . . . . . . . . . . . . . . . . . . . . . . . 8-3

8-3

KM-37 NS SSDS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-6

8-4

KM-37 NS General Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-9

8-5

MK 20 General Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-13

8-6

MK 20 MOD 0 UBA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-15

8-7

Divator DP General Characteristics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-17

8-8

MK 3 Lightweight Dive System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-19

8-9

Flyaway Dive System (FADS) III . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-20

8-10

Oxygen Regulator Control Assembly (ORCA) II . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-21

8-11

Oxygen Regulator Control Assembly (ORCA) II Schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-22

8-12

Communicating with Line-Pull Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-22

8-13

Surface Supplied Diving Station Setup Checklist . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-28

8-14

Surface Decompression . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-37

9-1

Diving Chart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-5

9-2

Graphic View of a Dive with Abbreviations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-6

9-3

Completed Air Diving Chart: No-Decompression Dive . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-10

9-4

Completed Air Diving Chart: In-water Decompression on Air . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-12

9-5

Completed Air Diving Chart: In-water Decompression on Air and Oxygen . . . . . . . . . . . . . . . . . 9-14

9-6

Completed Air Diving Chart: Surface Decompression on Oxygen . . . . . . . . . . . . . . . . . . . . . . . 9-18

9-7

Decompression Mode Selection Flowchart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-20

9-8

Repetitive Dive Flow Chart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-22

9-9

Repetitive Dive Worksheet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-24

9-10

Completed Air Diving Chart: First Dive of Repetitive Dive Profile . . . . . . . . . . . . . . . . . . . . . . . . 9-26

9-11

Completed Repetitive Dive Worksheet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-27

9-12

Completed Air Diving Chart: Second Dive of Repetitive Dive Profile . . . . . . . . . . . . . . . . . . . . . 9-28

9-13

Completed Air Diving Chart: Delay in Ascent deeper than 50 fsw . . . . . . . . . . . . . . . . . . . . . . . . 9-33

9-14

Completed Air Diving Chart: Delay in Ascent Shallower than 50 fsw . . . . . . . . . . . . . . . . . . . . . 9-34

List of Illustrations

xliii

Figure

xliv

Page

9-15

Diving at Altitude Worksheet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-51

9-16

Completed Diving at Altitude Worksheet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-54

9-17

Completed Air Diving Chart: Dive at Altitude . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-55

9-18

Repetitive Dive at Altitude Worksheet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-56

9-19

Completed Repetitive Dive at Altitude Worksheet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-59

9-20

Completed Air Diving Chart: First Dive of Repetitive Dive Profile at Altitude . . . . . . . . . . . . . . . . 9-60

9-21

Completed Air Diving Chart: Second Dive of Repetitive Dive Profile at Altitude . . . . . . . . . . . . . 9-60

10-1

NITROX Diving Chart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-6

10-2

NITROX SCUBA Bottle Markings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-8

10-3

NITROX O2 Injection System. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-10

10-4

LP Air Supply NITROX Membrane Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-12

10-5

HP Air Supply NITROX Membrane Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-13

11-1

Two SCUBA Cylinders Fitted with Two Actual Redundant First Stage Regulators . . . . . . . . . . . 11-3

11-2

Ice Diving with SCUBA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-8

11-3

DRASH Brand 10-man Tent . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-9

11-4

Typical Ice Diving Worksite . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-11

2B-1

Navy Dive Computer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2B-1

2B-2

NDC Ascent Rate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2B-6

2C-1

Water Temperature Protection Chart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2C-8

2C-2

Environmental Assessment Worksheet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2C-10

2C-3

International Code Signal Flags . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2C-16

2D-1

DP Diving Vessel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2D-1

2D-2

DP Component Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2D-5

2D-3

DP Pilot Seat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2D-5

2D-4

Alarm Panel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2D-6

2D-5

Safe Distance Chart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2D-12

2D-6

Illustration of Maximum Umbilical Lengths . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2D-16

2D-7

Illustration of Maximum Umbilical Lengths. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2D-18

2D-8

Vessel Section Checklist for Navy Surface Supplied Diving Operations from a DP Vessel. . . .2D-21

2D-9

Pre Dive Check List for Navy Surface Supplied Diving Operations from a DP Vessel . . . . . . .2D-22

12-1

FADS III Mixed Gas System (FMGS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-5

12-2

FMGS Control Console Assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-5

12-3

Dive Team Brief for Divers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-6

12-4

Diving Chart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-27

12-5

Completed HeO2 Diving Chart: Surface Decompression Dive . . . . . . . . . . . . . . . . . . . . . . . . . 12-28

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Figure

Page

12-6

Completed HeO2 Diving Chart: In-water Decompression Dive . . . . . . . . . . . . . . . . . . . . . . . . . 12-29

12-7

Completed HeO2 Diving Chart: Surface Decompression Dive with Hold
on Descent and Delay on Ascent . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-30

13-1

SAT FADS System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-1

13-2

SAT FADS Dive Bell Exterior . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-2

13-3

SAT FADS DDC Interior . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-3

13-4

SAT FADS Control Van . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-6

13-5

DIVEX SLS MK-4 Helmet with Backpack . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-7

13-6

MK 22 MOD 0 with Hot Water Suit, Hot Water Shroud, and ComeHome Bottle . . . . . . . . . . . . . 13-7

13-7

NEDU’s Ocean Simulation Facility (OSF) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-8

13-8

NEDU’s Ocean Simulation Facility Saturation Diving Chamber Complex . . . . . . . . . . . . . . . . . . 13-9

13-9

NEDU’s Ocean Simulation Facility Control Room . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-9

13-10

Dive Bell and LARS System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-18

13-11

Inside Dive Bell . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-28

13-12

PTC Placement Relative to Excursion Limits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-33

13-13

Saturation Decompression Sickness Treatment Flow Chart . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-41

14-1

Mixing by Cascading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14-3

14-2

Mixing with Gas Transfer System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14-4

15-1

MK 16 MOD 1 Closed-Circuit Mixed-Gas UBA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-1

15-2

Typical EC-UBA Functional Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-2

15-3

UBA Breathing Bag Acts to Maintain the Diver’s Constant Buoyancy
by Responding Counter to Lung Displacement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-4

15-4

EC-UBA Dive Record Sheet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-14

15-5

Typical EC-UBA Emergency Breathing System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-21

15-6

MK 16 MOD 1 UBA General Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-33

15-7

MK 16 MOD 0 General Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-34

15-8

Repetitive Dive Worksheet for 1.3 ata ppO2N202 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-38

15-9

Repetitive Dive Worksheet for 1.3 ata ppO2 HeO2 Dives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-50

15-10

Dive Worksheet for Repetitive 0.75 ata ppO2N202 Dives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-68

16-1

Diver in MK-25 CC-UBA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-1

16-2

Example of Transit with Excursion. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-8

16-3

MK 25 MOD 2 Operational Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-21

17-1

Treatment of Arterial Gas Embolism or Serious Decompression Sickness . . . . . . . . . . . . . . . . 17-39

17-2

Treatment of Type I Decompression Sickness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-40

17-3

Treatment of Symptom Recurrence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-42

17-4

Treatment Table 5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-43

List of Illustrations

xlv

Figure

xlvi

Page

17-5

Treatment Table 6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-44

17-6

Treatment Table 6A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-45

17-7

Treatment Table 4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-46

17-8

Treatment Table 7 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-47

17-9

Treatment Table 8 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-48

17-10

Treatment Table 9 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-49

17-11

Air Treatment Table 1A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-50

17-12

Air Treatment Table 2A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-51

17-13

Air Treatment Table 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-52

18-1

Double-Lock Steel Recompression Chamber . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-6

18-2

Recompression Chamber Facility: RCF 6500 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-7

18-3

Recompression Chamber Facility: RCF 5000 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-8

18-4

Double-Lock Steel Recompression Chamber . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-9

18-5

Fleet Modernized Double-Lock Recompression Chamber . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-10

18-6

Standard Navy Double-Lock Recompression Chamber System . . . . . . . . . . . . . . . . . . . . . . . . 18-11

18-7

Transportable Recompression Chamber System (TRCS). . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-12

18-8

Transportable Recompression Chamber (TRC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-12

18-9

Transfer Lock (TL) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-13

18-10

Fly Away Recompression Chamber (FARCC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-13

18-11

Fly Away Recompression Chamber . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-14

18-12

Fly Away Recompression Chamber Life Support Skid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-14

18-13

Recompression Chamber Predive Checklist . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-18

18-14

Recompression Chamber Postdive Checklist . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-24

18-15

Pressure Test for USN Recompression Chambers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-26

5A-1a

Neurological Examination Checklist . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5A-3

5A-2a

Dermatomal Areas Correlated to Spinal Cord Segment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5A-11

5B-1

Pressure Points . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5B-3

5B-2

Applying a Tourniquet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5B-5

5C-1

Types of Sharks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5C-2

5C-2

Killer Whale . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5C-3

5C-3

Barracuda . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5C-4

5C-4

Moray Eel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5C-5

5C-5

Weeverfish. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5C-6

5C-6

Highly Toxic Fish . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5C-8

5C-7

Stingray . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5C-9

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Table

Page

5C-8

Coelenterates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5C-10

5C-9

Octopus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5C-12

5C-10

Cone Shell . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5C-15

5C-11

Sea Snake . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5C-16

List of Tables

xlvii

Chap/Para

Page

PAGE LEFT BLANK INTENTIONALLY

xlviii

U.S. Navy Diving Manual

Table

Page
List of Tables

Table

Page

2-1

Pressure Chart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-13

2-2

Components of Dry Atmospheric Air . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-14

2-3

Partial Pressure at 1 ata . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-24

2-4

Partial Pressure at 137 ata . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-24

2-5

Symbols and Values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-31

2-6

Buoyancy (In Pounds) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-32

2-7

Formulas for Area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-32

2-8

Formulas for Volumes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-32

2-9

Formulas for Partial Pressure/Equivalent Air Depth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-32

2-10

Pressure Equivalents. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-33

2-11

Volume and Capacity Equivalents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-33

2-12

Length Equivalents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-34

2-13

Area Equivalents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-34

2-14

Velocity Equivalents. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-34

2-15

Mass Equivalents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-35

2-16

Energy or Work Equivalents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-35

2-17

Power Equivalents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-35

2-18

Temperature Equivalents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-36

2-19

Atmospheric Pressure at Altitude . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-36

3-1

Signs and Symptoms of Dropping Core Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-54

3-2

Signs of Heat Stress . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-57

4-1

U.S. Navy Diving Breathing Air Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-5

4-2

Diver’s Compressed Oxygen Breathing Purity Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-6

4-3

Diver’s Compressed Helium Breathing Purity Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-7

4-4

Diver’s Compressed Nitrogen Breathing Purity Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-8

1A-1

PEL Selection Table. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1A-3

1A-2

Depth Reduction Table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1A-5

1A-3

Wet Suit Un-Hooded . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1A-12

1A-4

Wet Suit Hooded . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1A-13

1A-5

Helmeted . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1A-14

1A-6

Permissible Exposure Limit (PEL) Within a 24-hour Period for
Exposure to AN/SQQ-14, -30, -32 Sonars. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1A-15

6-1

Navy Recompression Chamber Support Levels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-20

List of Tables

xlix

Table

l

Page

6-2

Air Diving Recompression Chamber Recommendations (Bottom Time in Minutes) . . . . . . . . . . 6-20

7-1

Sample SCUBA Cylinder Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-12

8-1

KM-37 NS Overbottom Pressure Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-8

8-2

Line-Pull Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-24

9-1

Pneumofathometer Correction Factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-7

9-2

Management of Extended Surface Interval and Type I Decompression
Sickness during the Surface Interval . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-41

9-3

Management of Asymptomatic Omitted Decompression. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-43

9-4

Sea Level Equivalent Depth (fsw) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-48

9-5

Repetitive Groups Associated with Initial Ascent to Altitude . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-50

9-6

Required Surface Interval Before Ascent to Altitude After Diving . . . . . . . . . . . . . . . . . . . . . . . . 9-62

9-7

No-Decompression Limits and Repetitive Group Designators for
No-Decompression Air Dives. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-63

9-8

Residual Nitrogen Time Table for Repetitive Air Dives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-64

9-9

Air Decompression Table. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-65

10-1

Equivalent Air Depth Table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-4

10-2

Oil Free Air. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-11

2A-1

No-Decompression Limits and Repetitive Group Designators for Shallow Water
Air No-Decompression Dives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2A-2

2A-2

Residual Nitrogen Time Table for Repetitive Shallow Water Air Dives . . . . . . . . . . . . . . . . . . . . 2A-3

2B-1

NDC Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2B-4

2B-2

Initial Management of Asymptomatic Omitted Decompression for NDC Dives . . . . . . . . . . . . . . 2B-8

2C-1

Equivalent Wind Chill Temperature Chart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2C-2

2C-2

Sea State Chart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2C-4

2C-3

Bottom Conditions and Effects Chart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2C-6

12-1

Surface Supplied Mixed Gas Dive Team . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-2

12-2

Pneumofathometer Correction Factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-6

12-3

Management of Asymptomatic Omitted Decompression. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-21

12-4

Surface-Supplied Helium-Oxygen Decompression Table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-31

13-1

Guidelines for Minimum Inspired HeO2 Temperatures for Saturation Depths
Between 350 and 1,500 fsw . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-11

13-2

Typical Saturation Diving Watch Stations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-16

13-3

Chamber Oxygen Exposure Time Limits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-19

13-4

Treatment Gases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-20

13-5

Limits for Selected Gaseous Contaminants in Saturation Diving Systems . . . . . . . . . . . . . . . . 13-24

13-6

Saturation Diving Compression Rates. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-26

U.S. Navy Diving Manual

Table

Page

13-7

Unlimited Duration Downward Excursion Limits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-29

13-8

Unlimited Duration Upward Excursion Limits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-30

13-9

Saturation Decompression Rates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-36

13-10

Emergency Abort Decompression Times and Oxygen Partial Pressures . . . . . . . . . . . . . . . . . 13-39

15-1

EC-UBA Operational Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-6

15-2

Personnel Requirements Chart for EC-UBA Diving. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-8

15-3

EC-UBA Diving Equipment Requirements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-10

15-4

MK 16 MOD 1 Recompression Chamber Requirements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-12

15-5

EC-UBA Dive Briefing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-16

15-6

EC-UBA Line-Pull Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-16

15-7

Initial Management of Asymptomatic Omitted Decompression EC-UBA Diver . . . . . . . . . . . . . 15-31

15-8

No Decompression Limits and Repetitive Group Designators for 1.3 ata ppO2N2O2 Dives . . . 15-36

15-9

Residual Nitrogen Timetable for 1.3 ata ppO2N2O2 Dives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-37

15-10

1.3 ata ppO2N2O2 Decompression Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-39

15-11

No Decompression Limits and Repetitive Group Designators for 1.3 ata ppO2 HeO2 Dives . . . 15-48

15-12

Residual Helium Timetable for 1.3 ata ppO2 HeO2 Dives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-49

15-13

1.3 ata ppO2 HeO2 Decompression Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-51

15-14

No Decompression Limits and Repetitive Group Designation Table for 0.75 ata Constant ppO2
N2O2 Dives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-66

15-15

Residual Nitrogen Timetable for Repetitive 0.75 ata Constant ppO2N2O2 Dives . . . . . . . . . . . . 15-67

15-16

Closed-Circuit Mixed-Gas UBA Decompression Table Using 0.75 ata Constant ppO2N2O2 . . 15-69

15-17

Closed-Circuit Mixed-Gas UBA Decompression Table Using 0.75 ata Constant Partial Pressure
Oxygen in Helium. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-77

16-1

Excursion Limits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-8

16-2

Single-Depth Oxygen Exposure Limits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-10

16-3

Adjusted Oxygen Exposure Limits for Successive Oxygen Dives . . . . . . . . . . . . . . . . . . . . . . . 16-12

16-4

CC-UBA Diving Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-16

16-5

Diving Supervisor Brief . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-18

17-1

Minimum Manning Levels for Recompression Treatments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-2

17-2

Rules for Recompression Treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-10

17-3

Decompression . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-20

17-4

Guidelines for Conducting Hyperbaric Oxygen Therapy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-22

17-5

Maximum Permissible Recompression Chamber Exposure Times at Various Temperatures. . 17-24

17-6

High Oxygen Treatment Gas Mixtures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-26

17-7

Tender Oxygen Breathing Requirements. (Note 1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-29

17-8

Primary Emergency Kit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-37

List of Tables

li

Table

lii

Page

17-9

Secondary Emergency Kit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-38

18-1

Navy Recompression Chamber Support Levels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-1

18-2

Recompression Chamber Line Guide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-5

18-3

Recompression Chamber Air Supply Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-16

5A-1

Extremity Strength Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5A-9

5A-2

Reflexes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5A-13

U.S. Navy Diving Manual

VOLUME 1

Diving Principles
and Policy

1

History of Diving

2

Underwater Physics

3

Underwater Physiology
and Diving Disorders

4

Dive Systems

5

Dive Program
Administration

Appendix 1A

Safe Diving Distances from
Transmitting Sonar

Appendix 1B

References

Appendix 1C

Telephone Numbers

Appendix 1D

List of Acronyms

U.S. NAVY DIVING MANUAL

PAGE LEFT BLANK INTENTIONALLY

Volume 1 - Table of Contents
Chap/Para

Page

1

HISTORY OF DIVING

1-1

INTRODUCTION.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-1

1-2

1-1.1

Purpose. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-1

1-1.2

Scope .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-1

1-1.3

Role of the U.S. Navy.. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-1

SURFACE-SUPPLIED AIR DIVING.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-1
1-2.1

Breathing Tubes .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-2

1-2.2

Breathing Bags.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-3

1-2.3

Diving Bells.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-3

1-2.4

Diving Dress Designs.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-3
1-2.4.1
1-2.4.2
1-2.4.3
1-2.4.4

1-2.5

Caissons.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-5

1-2.6

Physiological Discoveries.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-6
1-2.6.1
1-2.6.2
1-2.6.3

1-3

Lethbridge’s Diving Dress .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-3
Deane’s Patented Diving Dress.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-4
Siebe’s Improved Diving Dress .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-4
Salvage of the HMS Royal George .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-5

Caisson Disease (Decompression Sickness). . . . . . . . . . . . . . . . . . . . . . . . . 1-6
Inadequate Ventilation.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-7
Nitrogen Narcosis. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-7

1-2.7

Armored Diving Suits .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-7

1-2.8

MK V Deep-Sea Diving Dress. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-8

SCUBA DIVING .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-8
1-3.1

Open-Circuit SCUBA. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-9
1‑3.1.1
1‑3.1.2
1‑3.1.3
1‑3.1.4

1-3.2

Rouquayrol’s Demand Regulator.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-9
LePrieur’s Open-Circuit SCUBA Design .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-9
Cousteau and Gagnan’s Aqua-Lung .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-10
Impact of SCUBA on Diving.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-10

Closed-Circuit SCUBA .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-10
1‑3.2.1
1‑3.2.2

Fleuss’ Closed-Circuit SCUBA.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-10
Modern Closed-Circuit Systems. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-11

1-3.3

Hazards of Using Oxygen in SCUBA .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-11

1-3.4

Semiclosed-Circuit SCUBA.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-12
1‑3.4.1
1‑3.4.2

1-3.5

Lambertsen’s Mixed-Gas Rebreather .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-12
MK 6 UBA. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-12

SCUBA Use During World War II .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-13
1‑3.5.1
1‑3.5.2
1‑3.5.3

Table of Contents­—Volume 1

Diver-Guided Torpedoes .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-13
U.S. Combat Swimming.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-14
Underwater Demolition. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-15

1–i

Chap/Para
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Page
MIXED-GAS DIVING. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-16
1-4.1

Nonsaturation Diving. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-16
1‑4.1.1
1‑4.1.2
1‑4.1.3
1‑4.1.4

Diving Bells.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-20

1-4.3

Saturation Diving. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-21

1-4.4

1-21
1-22
1-22
1-22
1-22

ADS-IV.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
MK 1 MOD 0. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
MK 2 MOD 0. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
MK 2 MOD 1. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .

1-25
1-25
1-25
1-26

SUBMARINE SALVAGE AND RESCUE .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-26
1-5.1

USS F-4 .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-26

1-5.2

USS S-51 .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-27

1-5.3

USS S-4 .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-27

1-5.4

USS Squalus. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-28

1-5.5

USS Thresher.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-28

1-5.6

Deep Submergence Systems Project.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-29

SALVAGE DIVING .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-29
1-6.1

World War II Era.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-29
1‑6.1.1
1‑6.1.2
1‑6.1.3

1-6.2

Pearl Harbor.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-29
USS Lafayette .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-29
Other Diving Missions .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-30

Vietnam Era .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-30

1-7

OPEN-SEA DEEP DIVING RECORDS. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-30

1-8

SUMMARY .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-31

2

UNDERWATER PHYSICS

2-1

INTRODUCTION.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-1

2-2

1–ii

Advantages of Saturation Diving .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Bond’s Saturation Theory. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Genesis Project .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Developmental Testing.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Sealab Program.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .

Deep Diving Systems (DDS). .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-24
1‑4.4.1
1‑4.4.2
1‑4.4.3
1‑4.4.4

1-6

1-16
1-18
1-19
1-20

1-4.2

1‑4.3.1
1‑4.3.2
1‑4.3.3
1‑4.3.4
1‑4.3.5

1-5

Helium-Oxygen (HeO2) Diving.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Hydrogen-Oxygen Diving.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Modern Surface-Supplied Mixed-Gas Diving.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
MK 1 MOD 0 Diving Outfit .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .

2-1.1

Purpose. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-1

2-1.2

Scope .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-1

PHYSICS .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-1

U.S. Navy Diving Manual—Volume 1

Chap/Para
2-3

2-4

Page
MATTER.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-1
2-3.1

Elements.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-1

2-3.2

Atoms .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-1

2-3.3

Molecules .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-1

2-3.4

The Three States of Matter.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-2

MEASUREMENT .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-2
2-4.1

Measurement Systems.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-2

2-4.2

Temperature Measurements.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-3
2‑4.2.1
2‑4.2.2

2-4.3
2-5

2-6

2-7

Gas Measurements. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-3

ENERGY .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-4
2-5.1

Conservation of Energy. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-5

2-5.2

Classifications of Energy. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-5

LIGHT ENERGY IN DIVING.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-5
2-6.1

Refraction.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-5

2-6.2

Turbidity of Water .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-6

2-6.3

Diffusion .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-6

2-6.4

Color Visibility.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-6

MECHANICAL ENERGY IN DIVING .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-6
2-7.1

Water Temperature and Sound.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-7

2-7.2

Water Depth and Sound.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-7
2‑7.2.1
2‑7.2.2

2-7.3

2-9

Diver Work and Noise .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-7
Pressure Waves.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-7

Underwater Explosions.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-8
2‑7.3.1
2‑7.3.2
2‑7.3.3
2‑7.3.4
2‑7.3.5
2‑7.3.6
2‑7.3.7
2‑7.3.8

2-8

Kelvin Scale.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-3
Rankine Scale .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-3

Type of Explosive and Size of the Charge.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-8
Characteristics of the Seabed .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-8
Location of the Explosive Charge. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-8
Water Depth.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-8
Distance from the Explosion. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-8
Degree of Submersion of the Diver .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-9
Estimating Explosion Pressure on a Diver.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-9
Minimizing the Effects of an Explosion. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-10

HEAT ENERGY IN DIVING. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-10
2-8.1

Conduction, Convection, and Radiation.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-10

2-8.2

Heat Transfer Rate.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-10

2-8.3

Diver Body Temperature.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-11

PRESSURE IN DIVING. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-11
2-9.1

Atmospheric Pressure. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-12

Table of Contents­—Volume 1

1–iii

Chap/Para

Page
2-9.2

Terms Used to Describe Gas Pressure. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-12

2-9.3

Hydrostatic Pressure. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-12

2-9.4

Buoyancy .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-13
2‑9.4.1
2‑9.4.2

Archimedes’ Principle. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-13
Diver Buoyancy .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-13

2-10 GASES IN DIVING .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-14

2-11

2-10.1

Atmospheric Air.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-14

2-10.2

Oxygen.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-15

2-10.3

Nitrogen. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-15

2-10.4

Helium.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-15

2-10.5

Hydrogen. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-15

2-10.6

Neon.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-15

2-10.7

Carbon Dioxide.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-16

2-10.8

Carbon Monoxide.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-16

2-10.9

Kinetic Theory of Gases.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-16

GAS LAWS.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-17
2-11.1

Boyle’s Law.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-17

2-11.2

Charles’/Gay-Lussac’s Law. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-18

2-11.3

The General Gas Law.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-21

2-12 GAS MIXTURES.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-24
2-12.1

Dalton’s Law.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-24
2‑12.1.1 Calculating Surface Equivalent Value .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-27
2‑12.1.2 Expressing Small Quantities of Pressure.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-28
2‑12.1.3 Expressing Small Quantities of Volume.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-28

2-12.2

Gas Diffusion. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-28

2-12.3

Humidity .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-29

2-12.4

Gases in Liquids.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-29

2-12.5

Solubility.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-29

2-12.6

Henry’s Law .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-29
2‑12.6.1 Gas Tension.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-30
2‑12.6.2 Gas Absorption. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-30
2‑12.6.3 Gas Solubility.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-30

1–iv

3

UNDERWATER PHYSIOLOGY AND DIVING DISORDERS

3-1

INTRODUCTION.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-1
3-1.1

Purpose. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-1

3-1.2

Scope .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-1

3-1.3

General.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-1

U.S. Navy Diving Manual—Volume 1

Chap/Para

Page

3-2

THE NERVOUS SYSTEM. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-1

3-3

THE CIRCULATORY SYSTEM. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-2
3-3.1

Anatomy .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-2
3‑3.1.1
3‑3.1.2

3-4

3-3.2

Circulatory Function .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-2

3-3.3

Blood Components.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-3

THE RESPIRATORY SYSTEM.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-5
3-4.1

Gas Exchange. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-5

3-4.2

Respiration Phases.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-5

3-4.3

Upper and Lower Respiratory Tract .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-6

3-4.4

The Respiratory Apparatus.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-6
3‑4.4.1
3‑4.4.2

3-5

The Heart.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-2
The Pulmonary and Systemic Circuits.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-2

The Chest Cavity.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-6
The Lungs .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-6

3-4.5

Respiratory Tract Ventilation Definitions.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-8

3-4.6

Alveolar/Capillary Gas Exchange.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-9

3-4.7

Breathing Control .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-10

3-4.8

Oxygen Consumption.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-11

RESPIRATORY PROBLEMS IN DIVING.. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-11
3-5.1

Oxygen Deficiency (Hypoxia).  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-12
3‑5.1.1
3‑5.1.2
3‑5.1.3
3‑5.1.4

3-5.2

Causes of Hypoxia.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Symptoms of Hypoxia .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Treatment of Hypoxia.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Prevention of Hypoxia .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .

3-13
3-13
3-14
3-14

Carbon Dioxide Retention (Hypercapnia).  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-15
3‑5.2.1
3‑5.2.2
3‑5.2.3
3‑5.2.4

Causes of Hypercapnia .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Symptoms of Hypercapnia.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Treatment of Hypercapnia.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Prevention of Hypercapnia.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .

3-15
3-16
3-17
3-18

3-5.3

Asphyxia.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-18

3-5.4

Drowning/Near Drowning .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-18
3‑5.4.1
3‑5.4.2
3‑5.4.3
3‑5.4.4

Causes of Drowning.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Symptoms of Drowning/Near Drowning.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Treatment of Near Drowning .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Prevention of Near Drowning.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .

3-18
3-19
3-19
3-19

3-5.5

Breathholding and Unconsciousness.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-20

3-5.6

Involuntary Hyperventilation.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-20
3‑5.6.1
3‑5.6.2
3‑5.6.3

3-5.7

Causes of Involuntary Hyperventilation.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-20
Symptoms of Involuntary Hyperventilation.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-20
Treatment of Involuntary Hyperventilation.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-21

Overbreathing the Rig.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-21

Table of Contents­—Volume 1

1–v

Chap/Para

Page
3-5.8

Carbon Monoxide Poisoning.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-21
3‑5.8.1
3‑5.8.2
3‑5.8.3
3‑5.8.4

3-6

3-6.1

Prerequisites for Squeeze. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-23

3-6.2

Middle Ear Squeeze.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-24

3-6.3

Causes of Sinus Squeeze .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-25
Preventing Sinus Squeeze.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-26

3-6.4

Tooth Squeeze (Barodontalgia). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-26

3-6.5

External Ear Squeeze.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-26

3-6.6

Thoracic (Lung) Squeeze.. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-27

3-6.7

Face or Body Squeeze.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-27

3-6.8

Inner Ear Barotrauma.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-27

MECHANICAL EFFECTS OF PRESSURE ON THE HUMAN BODY--BAROTRAUMA
DURING ASCENT. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-30
3-7.1

Middle Ear Overpressure (Reverse Middle Ear Squeeze) .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-30

3-7.2

Sinus Overpressure (Reverse Sinus Squeeze) .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-31

3-7.3

Gastrointestinal Distention .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-31

PULMONARY OVERINFLATION SYNDROMES.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-32
3-8.1

Arterial Gas Embolism (AGE).  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-33
3‑8.1.1
3‑8.1.2
3‑8.1.3
3‑8.1.4

3-8.2

3-8.3

Causes of AGE. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Symptoms of AGE .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Treatment of AGE. . .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Prevention of AGE.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .

3-34
3-34
3-35
3-35

Mediastinal and Subcutaneous Emphysema .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-36
3‑8.2.1
3‑8.2.2
3‑8.2.3
3‑8.2.4

Causes of Mediastinal and Subcutaneous Emphysema .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Symptoms of Mediastinal and Subcutaneous Emphysema.  .  .  .  .  .  .  .  .  .  .  .  .
Treatment of Mediastinal and Subcutaneous Emphysema.  .  .  .  .  .  .  .  .  .  .  .  .
Prevention of Mediastinal and Subcutaneous Emphysema.  .  .  .  .  .  .  .  .  .  .  .  .

3-36
3-37
3-37
3-38

Pneumothorax. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-38
3‑8.3.1
3‑8.3.2
3‑8.3.3
3‑8.3.4

1–vi

Preventing Middle Ear Squeeze. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-24
Treating Middle Ear Squeeze. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-25

Sinus Squeeze .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-25
3‑6.3.1
3‑6.3.2

3-8

3-21
3-22
3-22
3-22

MECHANICAL EFFECTS OF PRESSURE ON THE HUMAN BODY-BAROTRAUMA
DURING DESCENT .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-23

3‑6.2.1
3‑6.2.2

3-7

Causes of Carbon Monoxide Poisoning.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Symptoms of Carbon Monoxide Poisoning .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Treatment of Carbon Monoxide Poisoning. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Prevention of Carbon Monoxide Poisoning .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .

Causes of Pneumothorax. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Symptoms of Pneumothorax .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Treatment of Pneumothorax. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Prevention of Pneumothorax.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .

3-38
3-39
3-40
3-40

U.S. Navy Diving Manual—Volume 1

Chap/Para
3-9

Page
INDIRECT EFFECTS OF PRESSURE ON THE HUMAN BODY.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-40
3-9.1

Nitrogen Narcosis.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-40
3‑9.1.1
3‑9.1.2
3‑9.1.3
3‑9.1.4

3-9.2

Oxygen Toxicity.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-42
3‑9.2.1
3‑9.2.2

3-9.3

Causes of Nitrogen Narcosis.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-41
Symptoms of Nitrogen Narcosis. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-41
Treatment of Nitrogen Narcosis.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-41
Prevention of Nitrogen Narcosis. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-41

Pulmonary Oxygen Toxicity .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-42
Central Nervous System (CNS) Oxygen Toxicity.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-42

Decompression Sickness (DCS). .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-46
3‑9.3.1
3‑9.3.2
3‑9.3.3
3‑9.3.4
3‑9.3.5
3‑9.3.6
3‑9.3.7

Absorption and Elimination of Inert Gases.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Bubble Formation.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Direct Bubble Effects.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Indirect Bubble Effects.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Symptoms of Decompression Sickness.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Treating Decompression Sickness. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Preventing Decompression Sickness. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .

3-46
3-50
3-50
3-51
3-51
3-52
3-52

3-10 THERMAL PROBLEMS IN DIVING.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-52
3-10.1

Regulating Body Temperature. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-53

3-10.2

Excessive Heat Loss (Hypothermia).  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-53
3‑10.2.1
3‑10.2.2
3‑10.2.3
3‑10.2.4

3-10.3

Causes of Hypothermia.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Symptoms of Hypothermia.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Treatment of Hypothermia.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Prevention of Hypothermia. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .

3-53
3-54
3-54
3-55

Other Physiological Effects of Exposure to Cold Water .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-56
3‑10.3.1 Caloric Vertigo .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-56
3‑10.3.2 Diving Reflex .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-56
3‑10.3.3 Uncontrolled Hyperventilation .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-56

3-10.4

Excessive Heat Gain (Hyperthermia).  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-56
3‑10.4.1
3‑10.4.2
3‑10.4.3
3‑10.4.4

3-11

Causes of Hyperthermia. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Symptoms of Hyperthermia.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Treatment of Hyperthermia .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Prevention of Hyperthermia.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .

3-56
3-57
3-57
3-58

SPECIAL MEDICAL PROBLEMS ASSOCIATED WITH DEEP DIVING.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-58
3-11.1

High Pressure Nervous Syndrome (HPNS) .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-58

3-11.2

Compression Arthralgia. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-58

3-12 OTHER DIVING MEDICAL PROBLEMS.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-59
3-12.1

Dehydration. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-59
3‑12.1.1 Causes of Dehydration. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-59
3‑12.1.2 Preventing Dehydration.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-60

3-12.2

Immersion Pulmonary Edema. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-60

3-12.3

Carotid Sinus Reflex.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-60

Table of Contents­—Volume 1

1–vii

Chap/Para

Page
3-12.4

Middle Ear Oxygen Absorption Syndrome .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-60
3‑12.4.1 Symptoms of Middle Ear Oxygen Absorption Syndrome.  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-61
3‑12.4.2 Treating Middle Ear Oxygen Absorption Syndrome.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-61

3-12.5

Underwater Trauma .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-61

3-12.6

Blast Injury .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-61

3-12.7

Otitis Externa. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-62

3-12.8

Hypoglycemia.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-63

3-12.9

Use of Medications While Diving. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-63

4

DIVE SYSTEMS

4-1

INTRODUCTION.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 4-1

4-2

4-1.1

Purpose. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 4-1

4-1.2

Scope .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 4-1

4-1.3

References.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 4-1

GENERAL INFORMATION. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 4-2
4-2.1

Document Precedence.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 4-2

4-2.2

Equipment Authorized For Military Use (AMU).  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 4-2

4-2.3

System Certification Authority (SCA) .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 4-3

4-2.4

Planned Maintenance System .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 4-3

4-2.5

Alteration of Diving Equipment.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 4-3
4‑2.5.1
4‑2.5.2

4-2.6

Operating and Emergency Procedures. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 4-3
4‑2.6.1
4‑2.6.2
4‑2.6.3
4‑2.6.4
4‑2.6.5

4-3

4-4

1–viii

Technical Program Managers for Shore-Based Systems. . . . . . . . . . . . . . . . 4-3
Technical Program Managers for Other Diving Apparatus.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 4-3

Standard Dive Systems/Equipment.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 4-4
Non-Standard Systems .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 4-4
OP/EP Approval Process.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 4-4
Format .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 4-4
Example.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 4-5

DIVER’S BREATHING GAS PURITY STANDARDS.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 4-5
4-3.1

Diver’s Breathing Air.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 4-5

4-3.2

Diver’s Breathing Oxygen .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 4-6

4-3.3

Diver’s Breathing Helium .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 4-7

4-3.4

Diver’s Breathing Nitrogen .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 4-8

DIVER’S AIR SAMPLING PROGRAM .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 4-8
4-4.1

Sampling Requirements.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 4-9

4-4.2

NSWC-PC Air Sampling Services .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 4-9

4-4.3

Local Air Sampling Services.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 4-10

4-4.4

Portable Air Monitor (PAM).  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 4-10

4-4.5

General Air Sampling Procedures. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 4-10

U.S. Navy Diving Manual—Volume 1

Chap/Para
4-5

Page
DIVE SYSTEM COMPONENTS. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 4-11
4-5.1

Diving Compressors.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 4-11
4‑5.1.1
4‑5.1.2
4‑5.1.3
4‑5.1.4
4‑5.1.5
4‑5.1.6

4-5.2

4-12
4-12
4-13
4-13
4-13
4-14

High-Pressure Air Cylinders and Flasks.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 4-14
4‑5.2.1

4-5.3

Lubrication.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Maintaining Oil Lubricated Compressors.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Water Vapor Control.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Volume Tank. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Pressure Regulators. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Air Filtration System.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .

Compressed Gas Handling and Storage.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 4-15

Diving Gauges. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 4-15
4‑5.3.1
4‑5.3.2
4‑5.3.3
4‑5.3.4

Selecting Diving System Gauges.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Calibrating and Maintaining Gauges .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Helical Bourdon Tube Gauges.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Pneumofathometer. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .

4-15
4-16
4-16
4-17

5

DIVE PROGRAM ADMINISTRATION

5-1

INTRODUCTION.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5-1
5-1.1

Purpose. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5-1

5-1.2

Scope .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5-1

5-2

OBJECTIVES OF THE RECORD KEEPING AND REPORTING SYSTEM. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5-1

5-3

RECORD KEEPING AND REPORTING DOCUMENTS .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5-1

5-4

COMMAND DIVE LOG.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5-2

5-5

RECOMPRESSION CHAMBER LOG .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5-2

5-6

U.S. NAVY DIVE/JUMP REPORTING SYSTEM (DJRS) .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5-4

5-7

PERSONAL DIVE LOG .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5-4

5-8

EQUIPMENT FAILURE OR DEFICIENCY REPORTING .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5-4

5-9

DIVE MISHAP/NEAR MISHAP/HAZARD REPORTING .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5-4
5-9.1

Mishap/Near-Mishap/Hazard .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5-4

5-9.2

Judge Advocate General (JAG Investigation).  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5-5

5-9.3

Reporting Criteria .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5-5

5-9.4

HAZREPS.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5-5

5-10 ACTIONS REQUIRED .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5-6
5-10.1

Equipment Mishap Information Sheet.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5-7

5-10.2

Shipment of Equipment. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5-8

Table of Contents­—Volume 1

1–ix

Chap/Para

1A

Page

SAFE DIVING DISTANCES FROM TRANSMITTING SONAR

1A-1 INTRODUCTION.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1A-1
1A-2 BACKGROUND .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1A-1
1A-3 ACTION. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1A-2
1A-4 SONAR DIVING DISTANCES WORKSHEETS WITH DIRECTIONS FOR USE.  .  .  .  .  .  .  .  .  .  .  . 1A-2
1A-4.1

General Information/Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1A-2
1A‑4.1.1 Effects of Exposure .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1A-2
1A‑4.1.2 Suit and Hood Characteristics.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1A-2
1A‑4.1.3 In­-Water Hearing vs. In-Gas Hearing.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1A-2

1A-4.2

Directions for Completing the Sonar Diving Distances Worksheet.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1A-3

1A-5 GUIDANCE FOR DIVER EXPOSURE TO LOW-FREQUENCY SONAR (160–320 HZ).  .  .  .  . 1A-16
1A-6 GUIDANCE FOR DIVER EXPOSURE TO ULTRASONIC SONAR
(250 KHZ AND GREATER). .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1A-16

1–x

1B

REFERENCES .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1B-1

1C

TELEPHONE NUMBERS .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1C-1

1D

LIST OF ACRONYMS .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1D-1

U.S. Navy Diving Manual—Volume 1

Volume 1 - List of Illustrations
Figure

Page

1-1

Early Impractical Breathing Device.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-2

1-2

Assyrian Frieze (900 B.C.) .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-2

1-3

Engraving of Halley’s Diving Bell. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-4

1-4

Lethbridge’s Diving Suit. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-4

1-5

Siebe’s First Enclosed Diving Dress and Helmet .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-5

1-6

French Caisson.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-5

1-7

Armored Diving Suit. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-7

1-8

MK 12 and MK V.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-9

1-9

Fleuss Apparatus. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-11

1-10

Original Davis Submerged Escape Apparatus .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-13

1-11

Lambertsen Amphibious Respiratory Unit (LARU).  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-14

1-12

Emerson-Lambertsen Oxygen Rebreather.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-15

1-13

Draeger LAR V UBA.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-15

1-14

Helium-Oxygen Diving Manifold .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-17

1-15

MK V MOD 1 Helmet.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-18

1-16

MK 1 MOD 0 Diving Outfit.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-20

1-17

Sealab II .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-23

1-18

U.S. Navy’s First DDS, SDS-450. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-23

1-19

DDS MK 1 Personnel Transfer Capsule .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-25

1-20

PTC Handling System, Elk River. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-25

1-21

Recovery of the Squalus.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-28

2-1

Molecules .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-2

2-2

The Three States of Matter.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-2

2-3

Temperature Scales. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-3

2-4

The Six Forms of Energy. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-4

2-5

Objects Underwater Appear Closer.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-5

2‑6

Kinetic Energy.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-17

2‑7

Depth, Pressure, Atmosphere Graph .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-37

3-1

The Heart’s Components and Blood Flow. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-3

3-2

Respiration and Blood Circulation.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-4

3-3

Inspiration Process .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-7

3-4

Lungs Viewed from Medical Aspect. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-7

3-5

Lung Volumes.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-8

List of Illustrations—Volume 1

1–xi

Figure

1–xii

Page

3-6

Oxygen Consumption and RMV at Different Work Rates.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-12

3-7

Gross Anatomy of the Ear in Frontal Section .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-23

3-8

Location of the Sinuses in the Human Skull .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-26

3-9

Components of the Middle/Inner Ear. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-28

3-10

Pulmonary Overinflation Syndromes (POIS).  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-32

3-11

Arterial Gas Embolism. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-33

3-12

Mediastinal Emphysema.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-36

3-13

Subcutaneous Emphysema. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-37

3-14

Pneumothorax.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-38

3-15

Tension Pneumothorax.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-39

3-16

Saturation of Tissues.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-47

3-17

Desaturation of Tissues.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-49

5-1

Equipment Mishap Information Sheet.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5-9

1A-1

Sonar Safe Diving Distance/Exposure Time Worksheet.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1A-4

1A‑2

Sonar Safe Diving Distance/Exposure Time Worksheet (Completed Example).  .  .  .  .  .  .  .  .  .  .  .  . 1A-8

1A-3

Sonar Safe Diving Distance/Exposure Time Worksheet (Completed Example).  .  .  .  .  .  .  .  .  .  .  .  . 1A-9

1A‑4

Sonar Safe Diving Distance/Exposure Time Worksheet (Completed Example).  .  .  .  .  .  .  .  .  .  .  . 1A-10

1A‑5

Sonar Safe Diving Distance/Exposure Time Worksheet (Completed Example).  .  .  .  .  .  .  .  .  .  .  . 1A-11

U.S. Navy Diving Manual—Volume 1

Volume 1 - List of Tables
Table

Page

2‑1

Pressure Chart .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-13

2‑2

Components of Dry Atmospheric Air.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-14

2‑3

Partial Pressure at 1 ata .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-24

2‑4

Partial Pressure at 137 ata .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-24

2‑5

Symbols and Values .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-31

2‑6

Buoyancy (In Pounds).  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-32

2‑7

Formulas for Area .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-32

2‑8

Formulas for Volumes.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-32

2‑9

Formulas for Partial Pressure/Equivalent Air Depth .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-32

2‑10

Pressure Equivalents. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-33

2‑11

Volume and Capacity Equivalents.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-33

2‑12

Length Equivalents .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-34

2‑13

Area Equivalents.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-34

2‑14

Velocity Equivalents. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-34

2‑15

Mass Equivalents .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-35

2‑16

Energy or Work Equivalents .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-35

2‑17

Power Equivalents. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-35

2‑18

Temperature Equivalents. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-36

2-19

Atmospheric Pressure at Altitude .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-36

3‑1

Signs and Symptoms of Dropping Core Temperature.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-54

3‑2

Signs of Heat Stress.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-57

4‑1

U.S. Navy Diving Breathing Air Requirements .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 4-5

4‑2

Diver’s Compressed Oxygen Breathing Purity Requirements. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 4-6

4‑3

Diver’s Compressed Helium Breathing Purity Requirements.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 4-7

4‑4

Diver’s Compressed Nitrogen Breathing Purity Requirements.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 4-8

1A‑1

PEL Selection Table. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1A-3

1A‑2

Depth Reduction Table .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1A-5

1A‑3

Wet Suit Un-Hooded.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1A-12

1A‑4

Wet Suit Hooded.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1A-13

1A‑5

Helmeted.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1A-14

1A‑6

Permissible Exposure Limit (PEL) Within a 24-hour Period for
Exposure to AN/SQQ-14, -30, ‑32 Sonars. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1A-15

List of Tables—Volume 1

1–xiii

Chap/Para

Page

PAGE LEFT BLANK INTENTIONALLY

1–xiv

U.S. Navy Diving Manual—Volume 1

CHAPTER 1

History of Diving
1-1

INTRODUCTION
1-1.1

Purpose. This chapter provides a general history of the development of military

diving operations.
1-1.2

Scope. This chapter outlines the hard work and dedication of a number of

individuals who were pioneers in the development of diving technology. As with
any endeavor, it is important to build on the discoveries of our predecessors and
not repeat mistakes of the past.
1-1.3

1-2

Role of the U.S. Navy. The U.S. Navy is a leader in the development of modern
diving and underwater operations. The general requirements of national defense
and the specific require­ments of underwater reconnaissance, demolition, ordnance
disposal, construction, ship maintenance, search, rescue and salvage operations
repeatedly give impetus to training and development. Navy diving is no longer
limited to tactical combat operations, wartime salvage, and submarine sinkings.
Fleet diving has become increasingly important and diversified since World War
II. A major part of the diving mission is inspecting and repairing naval vessels to
minimize downtime and the need for dry-docking. Other aspects of fleet diving
include recovering practice and research torpedoes, installing and repairing
underwater electronic arrays, underwater construction, and locating and recovering
downed aircraft.

SURFACE-SUPPLIED AIR DIVING

The origins of diving are firmly rooted in man’s need and desire to engage in mari­
time commerce, to conduct salvage and military operations, and to expand the
frontiers of knowledge through exploration, research, and development.
Diving, as a profession, can be traced back more than 5,000 years. Early divers
confined their efforts to waters less than 100 feet deep, performing salvage work
and harvesting food, sponges, coral, and mother-of-pearl. A Greek historian,
Herodotus, recorded the story of a diver named Scyllis, who was employed by the
Persian King Xerxes to recover sunken treasure in the fifth century B.C.
From the earliest times, divers were active in military operations. Their missions
included cutting anchor cables to set enemy ships adrift, boring or punching holes
in the bottoms of ships, and building harbor defenses at home while attempting
to destroy those of the enemy abroad. Alexander the Great sent divers down to
remove obstacles in the harbor of the city of Tyre, in what is now Lebanon, which
he had taken under siege in 332 B.C.
Other early divers developed an active salvage industry centered around the major
shipping ports of the eastern Mediterranean. By the first century B.C., operations
CHAPTER 1 — History of Diving

1-1

in one area had become so well organized that a payment scale for salvage work
was established by law, acknowledging the fact that effort and risk increased with
depth. In 24 feet of water, the divers could claim a one-half share of all goods
recovered. In 12 feet of water, they were allowed a one-third share, and in 3 feet,
only a one-tenth share.
1-2.1

Breathing Tubes. The most obvious and crucial step to broadening a diver’s

capabilities was providing an air supply that would permit him to stay underwater.
Hollow reeds or tubes extending to the surface allowed a diver to remain
submerged for an extended period, but he could accomplish little in the way of
useful work. Breathing tubes were employed in military operations, permitting an
undetected approach to an enemy stronghold (Figure 1-1).
At first glance, it seemed logical that a longer breathing tube was the only require­
ment for extending a diver’s range. In fact, a number of early designs used leather
hoods with long flexible tubes supported at the surface by floats. There is no record,
however, that any of these devices were actually constructed or tested. The result
may well have been the drowning of the diver. At a depth of 3 feet, it is nearly
impossible to breathe through a tube using only the body’s natural respira­tory
ability, as the weight of the water exerts a total force of almost 200 pounds on
the diver’s chest. This force increases steadily with depth and is one of the most
important factors in diving. Successful diving operations require that the pressure
be overcome or eliminated. Throughout history, imaginative devices were designed
to overcome this problem, many by some of the greatest minds of the time. At first,
the problem of pressure underwater was not fully understood and the designs were
impractical.

Figure 1-1. Early Impractical Breathing Device.
This 1511 design shows the diver’s head encased
in a leather bag with a breathing tube extending to
the surface.

1-2

Figure 1-2. Assyrian Frieze (900 B.C.).

U.S. Navy Diving Manual—Volume 1

1-2.2

Breathing Bags. An entire series of designs was based on the idea of a breathing

bag carried by the diver. An Assyrian frieze of the ninth century B.C. shows what
appear to be divers using inflated animal skins as air tanks. However, these men
were probably swim­mers using skins for flotation. It would be impossible to
submerge while holding such an accessory (Figure 1-2).
A workable diving system may have made a brief appearance in the later Middle
Ages. In 1240, Roger Bacon made reference to “instruments whereby men can
walk on sea or river beds without danger to themselves.”
1-2.3

Diving Bells. Between 1500 and 1800 the diving bell was developed, enabling

divers to remain underwater for hours rather than minutes. The diving bell is a
bell-shaped appa­ratus with the bottom open to the sea.
The first diving bells were large, strong tubs weighted to sink in a vertical posi­tion,
trapping enough air to permit a diver to breathe for several hours. Later diving bells
were suspended by a cable from the surface. They had no significant underwater
maneuverability beyond that provided by moving the support ship. The diver could
remain in the bell if positioned directly over his work, or could venture outside for
short periods of time by holding his breath.
The first reference to an actual practical diving bell was made in 1531. For several
hundred years thereafter, rudimentary but effective bells were used with regu­larity.
In the 1680s, a Massachusetts-born adventurer named William Phipps modified the
diving bell technique by supplying his divers with air from a series of weighted,
inverted buckets as they attempted to recover treasure valued at $200,000.
In 1690, the English astronomer Edmund Halley developed a diving bell in which
the atmosphere was replenished by sending weighted barrels of air down from the
surface (Figure 1-3). In an early demonstration of his system, he and four compan­
ions remained at 60 feet in the Thames River for almost 1½ hours. Nearly 26 years
later, Halley spent more than 4 hours at 66 feet using an improved version of his
bell.
1-2.4

Diving Dress Designs. With an increasing number of military and civilian wrecks

littering the shores of Great Britain each year, there was strong incentive to develop
a diving dress that would increase the efficiency of salvage operations.

1-2.4.1

Lethbridge’s Diving Dress. In 1715, Englishman John Lethbridge developed

a one-man, completely enclosed diving dress (Figure 1-4). The Lethbridge
equipment was a reinforced, leather-covered barrel of air, equipped with a glass
porthole for viewing and two arm holes with watertight sleeves. Wearing this gear,
the occupant could accomplish useful work. This apparatus was lowered from a
ship and maneuvered in the same manner as a diving bell.

Lethbridge was quite successful with his invention and participated in salvaging
a number of European wrecks. In a letter to the editor of a popular magazine in
1749, the inventor noted that his normal operating depth was 10 fathoms (60 feet),

CHAPTER 1 — History of Diving

1-3

Figure 1-3. Engraving of Halley’s
Diving Bell.

Figure 1-4. Lethbridge’s Diving Suit.

with about 12 fathoms the maximum, and that he could remain underwater for 34
minutes.
Several designs similar to Lethbridge’s were used in succeeding years. However,
all had the same basic limitation as the diving bell—the diver had little freedom
because there was no practical way to continually supply him with air. A true
tech­nological breakthrough occurred at the turn of the 19th century when a handoperated pump capable of delivering air under pressure was developed.
1-2.4.2

1-2.4.3

Deane’s Patented Diving Dress. Several men produced a successful apparatus at
the same time. In 1823, two salvage operators, John and Charles Deane, patented
the basic design for a smoke apparatus that permitted firemen to move about in
burning buildings. By 1828, the apparatus evolved into Deane’s Patent Diving
Dress, consisting of a heavy suit for protection from the cold, a helmet with viewing
ports, and hose connections for delivering surface-supplied air. The helmet rested
on the diver’s shoulders, held in place by its own weight and straps to a waist belt.
Exhausted or surplus air passed out from under the edge of the helmet and posed
no problem as long as the diver was upright. If he fell, however, the helmet could
quickly fill with water. In 1836, the Deanes issued a diver’s manual, perhaps the
first ever produced.
Siebe’s Improved Diving Dress. Credit for developing the first practical diving

dress has been given to Augustus Siebe. Siebe’s initial contribution to diving was
a modification of the Deane outfit. Siebe sealed the helmet to the dress at the collar
by using a short, waist-length waterproof suit and added an exhaust valve to the
system (Figure 1-5). Known as Siebe’s Improved Diving Dress, this apparatus is
the direct ancestor of the MK V standard deep-sea diving dress.

1-4

U.S. Navy Diving Manual—Volume 1

1-2.4.4

Salvage of the HMS Royal George. By 1840, sev­

eral types of diving dress were being used in actual
diving operations. At that time, a unit of the British
Royal Engineers was engaged in removing the
remains of the sunken warship, HMS Royal George.
The warship was fouling a major fleet anchorage
just outside Portsmouth, England. Colonel William
Pasley, the officer in charge, de­cided that his
operation was an ideal opportunity to formally test
and evaluate the various types of ap­paratus. Wary
of the Deane apparatus because of the possibility of
helmet flooding, he formally rec­ommended that the
Siebe dress be adopted for future operations.
When Pasley’s project was completed, an official
government historian noted that “of the seasoned
divers, not a man escaped the repeated attacks
of rheumatism and cold.” The divers had been
Figure 1-5. Siebe’s First
Enclosed Diving Dress and
working for 6 or 7 hours a day, much of it spent
Helmet.
at depths of 60 to 70 feet. Pasley and his men did
not realize the implications of the observation.
What appeared to be rheumatism was instead a symptom of a far more serious
physiological problem that, within a few years, was to become of great importance
to the diving profession.
1-2.5

Caissons. At the same time that a practical diving dress was being perfected,
inventors were working to improve the diving bell by increasing its size and
adding high-capacity air pumps that could deliver enough pressure to keep water
entirely out of the bell’s interior. The improved pumps soon led to the construction
of chambers large enough to permit several men to engage in dry work on the
bottom. This was particularly advantageous for projects such as excavating bridge
footings or constructing tunnel sections where long periods of work were required.
These dry chambers were known as caissons, a French word meaning “big boxes”
(Figure 1-6).

Figure 1-6. French Caisson.
This caisson could be floated
over the work site and
lowered to the bottom by
flooding the side tanks.

CHAPTER 1 — History of Diving

1-5

Caissons were designed to provide ready access from the surface. By using an
air lock, the pressure inside could be maintained while men or materials could be
passed in and out. The caisson was a major step in engineering technology and its
use grew quickly.
1-2.6

Physiological Discoveries.

1-2.6.1

Caisson Disease (Decompression Sickness). With the increasing use of caissons,

a new and unexplained malady began to affect the caisson workers. Upon returning
to the surface at the end of a shift, the divers frequently would be struck by dizzy
spells, breathing difficulties, or sharp pains in the joints or abdomen. The sufferer
usually recovered, but might never be completely free of some of the symptoms.
Caisson workers often noted that they felt better working on the job, but wrongly
attributed this to being more rested at the beginning of a shift.
As caisson work extended to larger projects and to greater operating pressures, the
physiological problems increased in number and severity. Fatalities occurred with
alarming frequency. The malady was called, logically enough, caisson disease.
However, workers on the Brooklyn Bridge project in New York gave the sickness
a more descriptive name that has remained—the “bends.”
Today the bends is the most well-known danger of diving. Although men had been
diving for thousands of years, few men had spent much time working under great
atmospheric pressure until the time of the caisson. Individuals such as Pasley, who
had experienced some aspect of the disease, were simply not prepared to look for
anything more involved than indigestion, rheumatism, or arthritis.
1-2.6.1.1

Cause of Decompression Sickness. The actual cause of caisson disease was first

clinically described in 1878 by a French physiologist, Paul Bert. In studying the
effect of pressure on human physi­ology, Bert determined that breathing air under
pressure forced quantities of nitrogen into solution in the blood and tissues of
the body. As long as the pressure remained, the gas was held in solution. When
the pressure was quickly released, as it was when a worker left the caisson, the
nitrogen returned to a gaseous state too rapidly to pass out of the body in a natural
manner. Gas bubbles formed throughout the body, causing the wide range of
symptoms associated with the disease. Paralysis or death could occur if the flow of
blood to a vital organ was blocked by the bubbles.

1-2.6.1.2

Prevention and Treatment of Decompression Sickness. Bert recommended

that cais­son workers gradually decompress and divers return to the surface slowly.
His studies led to an immediate improvement for the caisson workers when they
discovered their pain could be relieved by returning to the pressure of the caisson as
soon as the symptom appeared.

Within a few years, specially designed recompression chambers were being placed
at job sites to provide a more controlled situation for handling the bends. The pres­
sure in the chambers could be increased or decreased as needed for an individual
worker. One of the first successful uses of a recompression chamber was in 1879

1-6

U.S. Navy Diving Manual—Volume 1

during the construction of a subway tunnel under the Hudson River between New
York and New Jersey. The recompression chamber markedly reduced the number
of serious cases and fatalities caused by the bends.
Bert’s recommendation that divers ascend gradually and steadily was not a
complete success, however; some divers continued to suffer from the bends. The
general thought at the time was that divers had reached the practical limits of the
art and that 120 feet was about as deep as anyone could work. This was because
of the repeated incidence of the bends and diver inefficiency beyond that depth.
Occasionally, divers would lose consciousness while working at 120 feet.
1-2.6.2

Inadequate Ventilation. J.S. Haldane, an English physiologist, conducted experi­
ments with Royal Navy divers from 1905 to 1907. He determined that part of the
problem was due to the divers not adequately ventilating their helmets, causing
high levels of carbon dioxide to accumulate. To solve the problem, he established
a standard supply rate of flow (1.5 cubic feet of air per minute, measured at the
pressure of the diver). Pumps capable of maintaining the flow and ventilating the
helmet on a continuous basis were used.

Haldane also composed a set of diving tables that established a method of decom­
pression in stages. Though restudied and improved over the years, these tables
remain the basis of the accepted method for bringing a diver to the surface.
As a result of Haldane’s studies, the practical operating depth for air divers was
extended to slightly more than 200 feet. The limit was not imposed by physiolog­
ical factors, but by the capabilities of the hand-pumps available to provide the air
supply.
1-2.6.3

Nitrogen Narcosis. Divers soon were moving into

deeper water and another unexplained malady began
to appear. The diver would appear intoxicated,
sometimes feeling euphoric and frequently losing
judgment to the point of forgetting the dive’s
purpose. In the 1930s this “rapture of the deep”
was linked to nitrogen in the air breathed under
higher pressures. Known as nitrogen narcosis, this
condition occurred because nitrogen has anesthetic
properties that become progressively more severe
with increasing air pres­sure. To avoid the problem,
special breathing mixtures such as helium-oxygen
were developed for deep diving (see section 1‑4,
Mixed-Gas Diving).
1-2.7

Armored Diving Suits. Numerous inventors, many

with little or no under­water experience, worked to
create an armored diving suit that would free the
diver from pressure problems (Figure 1‑7). In an
armored suit, the diver could breathe air at normal
atmospheric pressure and descend to great depths
CHAPTER 1 — History of Diving

Figure 1-7. Armored
Diving Suit.

1-7

without any ill effects. The barrel diving suit, de­signed by John Lethbridge in
1715, had been an armored suit in essence, but one with a limited operating depth.
The utility of most armored suits was questionable. They were too clumsy for the
diver to be able to accomplish much work and too complicated to provide protec­
tion from extreme pressure. The maximum anticipated depth of the various suits
developed in the 1930s was 700 feet, but was never reached in actual diving. More
recent pursuits in the area of armored suits, now called one-atmosphere diving
suits, have demonstrated their capability for specialized underwater tasks to 2,000
feet of saltwater (fsw).
1-2.8

MK V Deep-Sea Diving Dress. By 1905, the Bureau of Construction and Repair

had designed the MK V Diving Helmet which seemed to address many of the
problems encountered in diving. This deep-sea outfit was designed for extensive,
rugged diving work and provided the diver maximum physical protection and
some maneuverability.
The 1905 MK V Diving Helmet had an elbow inlet with a safety valve that
allowed air to enter the helmet, but not to escape back up the umbilical if the air
supply were interrupted. Air was expelled from the helmet through an exhaust
valve on the right side, below the port. The exhaust valve was vented toward the
rear of the helmet to prevent escaping bubbles from interfering with the diver’s
field of vision.
By 1916, several improvements had been made to the helmet, including a rudi­
mentary communications system via a telephone cable and a regulating valve
operated by an interior push button. The regulating valve allowed some control of
the atmospheric pressure. A supplementary relief valve, known as the spitcock, was
added to the left side of the helmet. A safety catch was also incorporated to keep
the helmet attached to the breast plate. The exhaust valve and the communi­cations
system were improved by 1927, and the weight of the helmet was decreased to be
more comfortable for the diver.
After 1927, the MK V changed very little. It remained basically the same helmet
used in salvage operations of the USS S-51 and USS S-4 in the mid-1920s. With
its associated deep-sea dress and umbilical, the MK V was used for all submarine
rescue and salvage work undertaken in peacetime and practically all salvage work
undertaken during World War II. The MK V Diving Helmet was the standard U.S.
Navy diving equipment until succeeded by the MK 12 Surface-Supplied Diving
System (SSDS) in February 1980 (see Figure 1‑8). The MK 12 was replaced by the
MK 21 in December 1993.
1-3

SCUBA DIVING

The diving equipment developed by Charles and John Deane, Augustus Siebe, and
other inventors gave man the ability to remain and work underwater for extended
periods, but movement was greatly limited by the requirement for surface-supplied
air. Inventors searched for methods to increase the diver’s movement without
increasing the hazards. The best solution was to provide the diver with a portable,
1-8

U.S. Navy Diving Manual—Volume 1

Figure 1-8. MK 12 and MK V.

self-contained air supply. For many years the self-contained underwater breathing
apparatus (SCUBA) was only a theoretical possibility. Early attempts to supply
self-contained compressed air to divers were not successful due to the limi­tations
of air pumps and containers to compress and store air at sufficiently high pressure.
SCUBA development took place gradually, however, evolving into three basic
types:
n Open-circuit SCUBA (where the exhaust is vented directly to the surrounding
water),
n Closed-circuit SCUBA (where the oxygen is filtered and recirculated), and
n Semiclosed-circuit SCUBA (which combines features of the open- and closedcircuit types).
1-3.1

1‑3.1.1

1‑3.1.2

Open-Circuit SCUBA. In the open-circuit apparatus, air is inhaled from a supply
cylinder and the exhaust is vented directly to the surrounding water.
Rouquayrol’s Demand Regulator. The first and highly necessary component of
an open-circuit apparatus was a demand regulator. Designed early in 1866 and
patented by Benoist Rouquayrol, the regulator adjusted the flow of air from the
tank to meet the diver’s breathing and pressure requirements. However, because
cylinders strong enough to contain air at high pressure could not be built at the
time, Rouquayrol adapted his regulator to surface-supplied diving equipment
and the technology turned toward closed-circuit designs. The application of
Rouquayrol’s concept of a demand regulator to a successful open-circuit SCUBA
was to wait more than 60 years.
LePrieur’s Open-Circuit SCUBA Design. The thread of open-circuit development
was picked up in 1933. Commander LePrieur, a French naval officer, constructed
an open-circuit SCUBA using a tank of compressed air. However, LePrieur did not
include a demand regulator in his design and, the diver’s main effort was diverted
to the constant manual control of his air supply. The lack of a demand regulator,

CHAPTER 1 — History of Diving

1-9

coupled with extremely short endurance, severely limited the practical use of
LePrieur’s apparatus.
1‑3.1.3

Cousteau and Gagnan’s Aqua-Lung. At the same time that actual combat opera­

tions were being carried out with closed-circuit apparatus, two Frenchmen
achieved a significant breakthrough in open-circuit SCUBA design. Working in
a small Mediterranean village, under the diffi­cult and restrictive conditions of
German-occupied France, Jacques-Yves Cousteau and Emile Gagnan combined
an improved demand regulator with high-pressure air tanks to create the first truly
efficient and safe open-circuit SCUBA, known as the Aqua-Lung. Cousteau and
his companions brought the Aqua-Lung to a high state of development as they
explored and photographed wrecks, devel­oping new diving techniques and testing
their equipment.
The Aqua-Lung was the culmination of hundreds of years of progress, blending
the work of Rouquayol, LePrieur, and Fleuss, a pioneer in closed-circuit SCUBA
development. Cousteau used his gear successfully to 180 fsw without significant
difficulty and with the end of the war the Aqua-Lung quickly became a commer­cial
success. Today the Aqua-Lung is the most widely used diving equipment, opening
the underwater world to anyone with suitable training and the funda­mental physical
abilities.
1‑3.1.4

Impact of SCUBA on Diving. The underwater freedom brought about by the
development of SCUBA led to a rapid growth of interest in diving. Sport diving has
become very popular, but science and commerce have also benefited. Biologists,
geologists and archaeolo­gists have all gone underwater, seeking new clues to
the origins and behavior of the earth, man and civilization as a whole. An entire
industry has grown around commercial diving, with the major portion of activity
in offshore petroleum production.

After World War II, the art and science of diving progressed rapidly, with emphasis
placed on improving existing diving techniques, creating new methods, and
developing the equipment required to serve these methods. A complete gener­ation
of new and sophisticated equipment took form, with substantial improvements
being made in both open and closed-circuit apparatus. However, the most significant
aspect of this technological expansion has been the closely linked development of
saturation diving techniques and deep diving systems.
1-3.2

1‑3.2.1

Closed-Circuit SCUBA. The basic closed-circuit system, or oxygen rebreather,
uses a cylinder of 100 percent oxygen that supplies a breathing bag. The oxygen
used by the diver is recirculated in the apparatus, passing through a chemical
filter that removes carbon dioxide. Oxygen is added from the tank to replace that
consumed in breathing. For special warfare operations, the closed-circuit system
has a major advantage over the open-circuit type: it does not produce a telltale trail
of bubbles on the surface.
Fleuss’ Closed-Circuit SCUBA. Henry A. Fleuss developed the first commercially

practical closed-circuit SCUBA between 1876 and 1878 (Figure 1‑9). The Fleuss
device consisted of a watertight rubber face mask and a breathing bag connected to
1-10

U.S. Navy Diving Manual—Volume 1

a copper tank of 100 percent oxygen charged to 450 psi. By using oxygen instead
of compressed air as the breathing medium, Fleuss eliminated the need for highstrength tanks. In early models of this apparatus, the diver controlled the makeup
feed of fresh oxygen with a hand valve.
Fleuss successfully tested his apparatus in 1879. In the
first test, he remained in a tank of water for about an
hour. In the second test, he walked along a creek bed at
a depth of 18 feet. During the second test, Fleuss turned
off his oxygen feed to see what would happen. He was
soon unconscious, and suffered gas embolism as his
tenders pulled him to the surface. A few weeks after his
recovery, Fleuss made arrangements to put his recircu­
lating design into commercial production.
In 1880, the Fleuss SCUBA figured prominently in a
highly publicized achievement by an English diver,
Alexander Lambert. A tunnel under the Severn River
flooded and Lambert, wearing a Fleuss apparatus,
walked 1,000 feet along the tunnel, in complete dark­
ness, to close several crucial valves.
1‑3.2.2

Modern Closed-Circuit Systems. As development of the

Figure 1-9. Fleuss

closed-circuit design continued, the Fleuss equipment
Apparatus.
was improved by adding a demand regulator and tanks
capable of holding oxygen at more than 2,000 psi. By
World War I, the Fleuss SCUBA (with modifications) was the basis for subma­rine
escape equipment used in the Royal Navy. In World War II, closed-circuit units
were widely used for combat diving operations (see paragraph 1‑3.5.2).
Some modern closed-circuit systems employ a mixed gas for breathing and elec­
tronically senses and controls oxygen concentration. This type of apparatus retains
the bubble-free characteristics of 100-percent oxygen recirculators while signifi­
cantly improving depth capability.
1-3.3

Hazards of Using Oxygen in SCUBA. Fleuss had been unaware of the serious

problem of oxygen toxicity caused by breathing 100 percent oxygen under
pressure. Oxygen toxicity apparently was not encountered when he used his
apparatus in early shallow water experiments. The danger of oxygen poisoning
had actually been discovered prior to 1878 by Paul Bert, the physiologist who
first proposed controlled decompression as a way to avoid the bends. In laboratory
experiments with animals, Bert demonstrated that breathing oxygen under pressure
could lead to convulsions and death (central nervous system oxygen toxicity).
In 1899, J. Lorrain Smith found that breathing oxygen over prolonged periods of
time, even at pressures not sufficient to cause convulsions, could lead to pulmo­nary
oxygen toxicity, a serious lung irritation. The results of these experiments, however,
were not widely publicized. For many years, working divers were unaware of the
dangers of oxygen poisoning.

CHAPTER 1 — History of Diving

1-11

The true seriousness of the problem was not apparent until large numbers of combat
divers were being trained in the early years of World War II. After a number of
oxygen toxicity accidents, the British established an operational depth limit of 33
fsw. Additional research on oxygen toxicity continued in the U.S. Navy after the
war and resulted in the setting of a normal working limit of 25 fsw for 75 minutes
for the Emerson oxygen rebreather. A maximum emergency depth/time limit of 40
fsw for 10 minutes was also allowed.
These limits eventually proved operationally restrictive, and prompted the Navy
Experimental Diving Unit to reexamine the entire problem of oxygen toxicity
in the mid-1980s. As a result of this work, more liberal and flexible limits were
adopted for U.S. Navy use.
1-3.4

1‑3.4.1

Semiclosed-Circuit SCUBA. The semiclosed-circuit SCUBA combines features
of the open and closed-circuit systems. Using a mixture of gases for breathing,
the apparatus recycles the gas through a carbon dioxide removal canister and
continually adds a small amount of oxygen-rich mixed gas to the system from a
supply cylinder. The supply gas flow is preset to satisfy the body’s oxygen demand;
an equal amount of the recirculating mixed-gas stream is continually exhausted to
the water. Because the quantity of makeup gas is constant regardless of depth, the
semiclosed-circuit SCUBA provides significantly greater endurance than opencircuit systems in deep diving.
Lambertsen’s Mixed-Gas Rebreather. In the late 1940s, Dr. C.J. Lambertsen
proposed that mixtures of nitrogen or helium with an elevated oxygen content be
used in SCUBA to expand the depth range beyond that allowed by 100-percent
oxygen rebreathers, while simulta­
neously minimizing the requirement for
decompression.

In the early 1950s, Lambertsen introduced the FLATUS I, a semiclosed-circuit
SCUBA that continually added a small volume of mixed gas, rather than pure
oxygen, to a rebreathing circuit. The small volume of new gas provided the oxygen
necessary for metabolic consumption while exhaled carbon dioxide was absorbed
in an absorbent canister. Because inert gas, as well as oxygen, was added to the rig,
and because the inert gas was not consumed by the diver, a small amount of gas
mixture was continuously exhausted from the rig.
1‑3.4.2

MK 6 UBA. In 1964, after significant development work, the Navy adopted a

semiclosed-circuit, mixed-gas rebreather, the MK 6 UBA, for combat swimming
and EOD operations. Decompression procedures for both nitrogen-oxygen and
helium-oxygen mixtures were developed at the Navy Experimental Diving Unit.
The apparatus had a maximum depth capability of 200 fsw and a maximum
endurance of 3 hours depending on water temperature and diver activity. Because
the appa­ratus was based on a constant mass flow of mixed gas, the endurance was
independent of the diver’s depth.
In the late 1960s, work began on a new type of mixed-gas rebreather technology,
which was later used in the MK 15 and MK 16 UBAs. In this UBA, the oxygen
partial pressure was controlled at a constant value by an oxygen sensing and addi­

1-12

U.S. Navy Diving Manual—Volume 1

tion system. As the diver consumed oxygen, an oxygen sensor detected the fall in
oxygen partial pressure and signaled an oxygen valve to open, allowing a small
amount of pure oxygen to be admitted to the breathing circuit from a cylinder.
Oxygen addition was thus exactly matched to metabolic consumption. Exhaled
carbon dioxide was absorbed in an absorption canister. The system had the endur­
ance and completely closed-circuit characteristics of an oxygen rebreather without
the concerns and limitations associated with oxygen toxicity.
Beginning in 1979, the MK 6 semiclosed-circuit underwater breathing apparatus
(UBA) was phased out by the MK 15 closed-circuit, constant oxygen partial
pres­sure UBA. The Navy Experimental Diving Unit developed decompression
procedures for the MK 15 with nitrogen and helium in the early 1980s. In 1985, an
improved low magnetic signature version of the MK 15, the MK 16, was approved
for Explosive Ordnance Disposal (EOD) team use.
1-3.5

SCUBA Use During World War II. Although closed-circuit equipment was restricted

to shallow-water use and carried with it the potential danger of oxygen toxicity, its
design had reached a suitably high level of efficiency by World War II. During the
war, combat diver breathing units were widely used by navies on both sides of the
conflict. The swimmers used various modes of underwater attack. Many notable
successes were achieved including the sinking of several battleships, cruisers, and
merchant ships.
1‑3.5.1

Diver-Guided Torpedoes. Italian divers,
using closed-circuit gear, rode chariot
torpedoes fitted with seats and manual
controls in repeated attacks against British
ships. In 1936, the Italian Navy tested a
chariot torpedo system in which the divers
used a descendant of the Fleuss SCUBA.
This was the Davis Lung (Figure 1‑10). It
was originally designed as a submarine es­
cape device and was later manufactured in
Italy under a license from the English patent
holders.

British divers, carried to the scene of action in
midget submarines, aided in placing explosive
charges under the keel of the German
Figure 1-10. Original Davis
battleship Tirpitz. The British began their
Submerged Escape Apparatus.
chariot program in 1942 using the Davis Lung
and exposure suits. Swimmers using the MK
1 chariot dress quickly discovered that the steel oxygen bottles adversely affected
the compass of the chariot torpedo. Aluminum oxygen cylin­ders were not readily
available in England, but German aircraft used aluminum oxygen cylinders that
were almost the same size as the steel cylinders aboard the chariot torpedo. Enough
aluminum cylinders were salvaged from downed enemy bombers to supply the
British forces.

CHAPTER 1 — History of Diving

1-13

Changes introduced in the MK 2 and MK 3 diving dress involved improvements in
valving, faceplate design, and arrangement of components. After the war, the MK 3
became the standard Royal Navy shallow water diving dress. The MK 4 dress was
used near the end of the war. Unlike the MK 3, the MK 4 could be supplied with
oxygen from a self-contained bottle or from a larger cylinder carried in the chariot.
This gave the swimmer greater endurance, yet preserved freedom of movement
independent of the chariot torpedo.
In the final stages of the war, the Japanese employed an underwater equivalent of
their kamikaze aerial attack—the kaiten diver-guided torpedo.
1‑3.5.2

U.S. Combat Swimming. There were two groups of U.S. combat divers during

World War II: Naval beach reconnaissance swimmers and U.S. operational
swimmers. Naval beach reconnaissance units did not normally use any breathing
devices, although several models existed.

U.S. operational swimmers, however,
under the Office of Strategic Services,
developed and applied advanced methods
for true self-contained diver-submersible
operations. They employed the Lambertsen
Amphibious Respiratory Unit (LARU), a
rebreather invented by Dr. C.J. Lambertsen
(see Figure 1‑11). The LARU was a closedcircuit oxygen UBA used in special warfare
operations where a complete absence of
exhaust bubbles was required. Following
World War II, the Emerson-Lambertsen
Oxygen Rebreather replaced the LARU
(Figure 1‑12). The Emerson Unit was
used exten­sively by Navy special warfare
divers until 1982, when it was replaced by
the Draeger Lung Automatic Regenerator
(LAR) V. The LAR V is the standard unit
now used by U.S. Navy combat divers (see
Figure 1-13).

Figure 1-11. Lambertsen Amphibious
Respiratory Unit (LARU).

Today Navy combat divers are organized into two separate groups, each with
specialized training and missions. The Explosive Ordnance Disposal (EOD) team
handles, defuses, and disposes of munitions and other explosives. The Sea, Air and
Land (SEAL) special warfare teams make up the second group of Navy combat
divers. SEAL team members are trained to operate in all of these envi­ronments.
They qualify as parachutists, learn to handle a range of weapons, receive intensive
training in hand-to-hand combat, and are expert in SCUBA and other swimming
and diving techniques. In Vietnam, SEALs were deployed in special counterinsurgency and guerrilla warfare operations. The SEALs also participated in the

1-14

U.S. Navy Diving Manual—Volume 1

Figure 1-12. Emerson-Lambertsen
Oxygen Rebreather.

Figure 1-13. Draeger LAR V UBA.

space program by securing flotation collars to returned space capsules and assisting
astronauts during the helicopter pickup.
1‑3.5.3

Underwater Demolition. The Navy’s Underwater Demolition Teams (UDTs) were
created when bomb disposal experts and Seabees (combat engineers) teamed
together in 1943 to devise methods for removing obstacles that the Germans were
placing off the beaches of France. The first UDT combat mission was a daylight
reconnaissance and demolition project off the beaches of Saipan in June 1944. In
March of 1945, preparing for the invasion of Okinawa, one underwater demolition
team achieved the exceptional record of removing 1,200 underwater obstacles in 2
days, under heavy fire, without a single casualty.

Because suitable equipment was not readily available, diving apparatus was not
extensively used by the UDT during the war. UDT experimented with a modified
Momsen lung and other types of breathing apparatus, but not until 1947 did the
Navy’s acquisition of Aqua-Lung equipment give impetus to the diving aspect of
UDT operations. The trail of bubbles from the open-circuit apparatus limited the
type of mission in which it could be employed, but a special SCUBA platoon of
UDT members was formed to test the equipment and determine appropriate uses
for it.
Through the years since, the mission and importance of the UDT has grown. In the
Korean Conflict, during the period of strategic withdrawal, the UDT destroyed an
entire port complex to keep it from the enemy. The UDTs have since been incor­
porated into the Navy Seal Teams.

CHAPTER 1 — History of Diving

1-15

1-4

MIXED-GAS DIVING

Mixed-gas diving operations are conducted using a breathing medium other than
air. This medium may consist of:
 Nitrogen and oxygen in proportions other than those found in the atmosphere
 A mixture of other inert gases, such as helium, with oxygen.
The breathing medium can also be 100 percent oxygen, which is not a mixed gas,
but which requires training for safe use. Air may be used in some phases of a
mixed-gas dive.
Mixed-gas diving is a complex undertaking. A mixed-gas diving operation requires
extensive special training, detailed planning, specialized and advanced equipment
and, in many applications, requires extensive surface-support personnel and
facilities. Because mixed-gas operations are often conducted at great depth or for
extended periods of time, hazards to personnel increase greatly. Divers studying
mixed-gas diving must first be qualified in air diving operations.
In recent years, to match basic operational requirements and capabilities, the U.S.
Navy has divided mixed-gas diving into two categories:
 Nonsaturation diving without a pressurized bell to a maximum depth of 300
fsw, and
 Saturation diving for dives of 150 fsw and greater depth or for extended bottom
time missions.
The 300-foot limit is based primarily on the increased risk of decompression sick­
ness when nonsaturation diving techniques are used deeper than 300 fsw.
1-4.1

Nonsaturation Diving.

1‑4.1.1

Helium-Oxygen (HeO2) Diving. An inventor named Elihu Thomson theorized that

helium might be an appropriate substitute for the nitrogen in a diver’s breathing
supply. He estimated that at least a 50-percent gain in working depth could be
achieved by substituting helium for nitrogen. In 1919, he suggested that the U.S.
Bureau of Mines investigate this possibility. Thomson directed his suggestion to
the Bureau of Mines rather than the Navy Department, since the Bureau of Mines
held a virtual world monopoly on helium marketing and distribution.
1‑4.1.1.1

1-16

Experiments with Helium-Oxygen Mixtures. In 1924, the Navy and the Bureau of
Mines jointly sponsored a series of experi­ments using helium-oxygen mixtures.
The preliminary work was conducted at the Bureau of Mines Experimental Station
in Pittsburgh, Pennsylvania. Figure 1‑14 is a picture of an early Navy heliumoxygen diving manifold.

U.S. Navy Diving Manual—Volume 1

Figure 1-14. Helium-Oxygen Diving Manifold.

The first experiments showed no detrimental effects on test animals or humans
from breathing a helium-oxygen mixture, and decompression time was shortened.
The principal physiological effects noted by divers using helium-oxygen were:
 Increased sensation of cold caused by the high thermal conductivity of helium
 The high-pitched distortion or “Donald Duck” effect on human speech that
resulted from the acoustic properties and reduced density of the gas
These experiments clearly showed that helium-oxygen mixtures offered great
advantages over air for deep dives. They laid the foundation for developing the
reliable decompression tables and specialized apparatus, which are the corner­
stones of modern deep diving technology.
In 1937, at the Experimental Diving Unit research facility, a diver wearing a deepsea diving dress with a helium-oxygen breathing supply was compressed in a
chamber to a simulated depth of 500 feet. The diver was not told the depth and
when asked to make an estimate of the depth, the diver reported that it felt as if he
were at 100 feet. During decompression at the 300-foot mark, the breathing mixture
was switched to air and the diver was troubled immediately by nitrogen narcosis.
The first practical test of helium-oxygen came in 1939, when the submarine USS
Squalus was salvaged from a depth of 243 fsw. In that year, the Navy issued
decompression tables for surface-supplied helium-oxygen diving.

CHAPTER 1 — History of Diving

1-17

1‑4.1.1.2

MK V MOD 1 Helmet. Because helium was

expensive and ship­
board supplies were
limited, the standard MK V MOD 0 opencircuit helmet was not economical for
surface-supplied helium-oxygen diving.
After experi­menting with several different
designs, the U.S. Navy adopted the
semiclosed-circuit MK V MOD 1 (Figure
1‑15).
The MK V MOD 1 helmet was equipped
with a carbon dioxide absorption canister
and venturi-powered recirculator assembly.
Gas in the helmet was continu­
ously
recirculated through the carbon dioxide
scrubber assembly by the venturi. By
removing carbon dioxide by scrubbing
rather than ventilating the helmet, the fresh
gas flow into the helmet was reduced to the
amount required to replenish oxygen. The
gas consumption of the semiclosed-circuit
MK V MOD 1 was approximately 10 percent
of that of the open-circuit MK V MOD 0.

Figure 1-15. MK V MOD 1 Helmet.

The MK V MOD 1, with breastplate and recirculating gas canister, weighed
approximately 103 pounds compared to 56 pounds for the standard air helmet and
breastplate. It was fitted with a lifting ring at the top of the helmet to aid in hatting
the diver and to keep the weight off his shoulders until he was lowered into the
water. The diver was lowered into and raised out of the water by a diving stage
connected to an onboard boom.
1‑4.1.1.3

Civilian Designers. U.S. Navy divers were not alone in working with mixed gases

or helium. In 1937, civilian engineer Max Gene Nohl reached 420 feet in Lake
Michigan while breathing helium-oxygen and using a suit of his own design. In
1946, civilian diver Jack Browne, designer of the lightweight diving mask that
bears his name, made a simulated helium-oxygen dive of 550 feet. In 1948, a
British Navy diver set an open-sea record of 540 fsw while using war-surplus
helium provided by the U.S.

1‑4.1.2

1-18

Hydrogen-Oxygen Diving. In countries where the availability of helium was
more restricted, divers experi­mented with mixtures of other gases. The most
notable example is that of the Swedish engineer Arne Zetterstrom, who worked
with hydrogen-oxygen mixtures. The explosive nature of such mixtures was well
known, but it was also known that hydrogen would not explode when used in a
mixture of less than 4 percent oxygen. At the surface, this percentage of oxygen
would not be sufficient to sustain life; at 100 feet, however, the oxygen partial
pressure would be the equivalent of 16 percent oxygen at the surface.

U.S. Navy Diving Manual—Volume 1

Zetterstrom devised a simple method for making the transition from air to
hydrogen-oxygen without exceeding the 4-percent oxygen limit. At the 100-foot
level, he replaced his breathing air with a mixture of 96 percent nitrogen and 4
percent oxygen. He then replaced that mixture with hydrogen-oxygen in the same
proportions. In 1945, after some successful test dives to 363 feet, Zetterstrom
reached 528 feet. Unfortunately, as a result of a misunderstanding on the part of his
topside support personnel, he was brought to the surface too rapidly. Zetter­strom
did not have time to enrich his breathing mixture or to adequately decompress and
died as a result of the effects of his ascent.
1‑4.1.3

Modern Surface-Supplied Mixed-Gas Diving. The U.S. Navy and the Royal Navy

continued to develop procedures and equip­
ment for surface-supplied heliumoxygen diving in the years following World War II. In 1946, the Admiralty
Experimental Diving Unit was established and, in 1956, during open-sea tests
of helium-oxygen diving, a Royal Navy diver reached a depth of 600 fsw. Both
navies conducted helium-oxygen decompression trials in an attempt to develop
better procedures.
In the early 1960s, a young diving enthusiast from Switzerland, Hannes Keller,
proposed techniques to attain great depths while minimizing decompression
requirements. Using a series of gas mixtures containing varying concentrations
of oxygen, helium, nitrogen, and argon, Keller demonstrated the value of elevated
oxygen pressures and gas sequencing in a series of successful dives in mountain
lakes. In 1962, with partial support from the U.S. Navy, he reached an open-sea
depth of more than 1,000 fsw off the California coast. Unfortunately, this dive was
marred by tragedy. Through a mishap unrelated to the technique itself, Keller lost
consciousness on the bottom and, in the subsequent emergency decompression,
Keller’s companion died of decompression sickness.
By the late 1960s, it was clear that surface-supplied diving deeper than 300 fsw
was better carried out using a deep diving (bell) system where the gas sequencing
techniques pioneered by Hannes Keller could be exploited to full advantage, while
maintaining the diver in a state of comfort and security. The U.S. Navy developed
decompression procedures for bell diving systems in the late 1960s and early
1970s. For surface-supplied diving in the 0-300 fsw range, attention was turned
to developing new equipment to replace the cumbersome MK V MOD 1 helmet.

CHAPTER 1 — History of Diving

1-19

1‑4.1.4

MK 1 MOD 0 Diving Outfit. The new

equipment development proceeded along
two parallel paths, developing open-circuit
demand breathing systems suitable for deep
helium-oxygen diving, and developing an
improved recirculating helmet to replace the
MK V MOD 1. By the late 1960s, engineering
improvements in demand regulators had
tance on deep dives
reduced breathing resis­
to acceptable levels. Masks and helmets
incorporating the new regulators became
commercially avail­able. In 1976, the U.S.
Navy approved the MK 1 MOD 0 Lightweight,
Mixed-Gas Diving Outfit for dives to 300 fsw
on helium-oxygen (Figure 1‑16). The MK 1
MOD 0 Diving Outfit incorporated a full face
mask (bandmask) featuring a demand opencircuit breathing regulator and a backpack for
an emergency gas supply. Surface contact was
maintained through an umbilical that included
Figure 1-16. MK 1 MOD 0
the breathing gas hose, communications
Diving Outfit.
cable, lifeline strength member and pneumo­
fathometer hose. The diver was dressed in a
dry suit or hot water suit depending on water
temperature. The equipment was issued as a lightweight diving outfit in a system
with sufficient equipment to support a diving operation employing two working
divers and a standby diver. The outfit was used in conjunction with an open diving
bell that replaced the traditional diver’s stage and added additional safety. In 1990,
the MK 1 MOD 0 was replaced by the MK 21 MOD 1 (Superlite 17 B/NS) demand
helmet. This is the lightweight rig in use today.
In 1985, after an extensive development period, the direct replacement for the
MK V MOD 1 helmet was approved for Fleet use. The new MK 12 Mixed-Gas
Surface-Supplied Diving System (SSDS) was similar to the MK 12 Air SSDS,
with the addition of a backpack assembly to allow operation in a semiclosed-circuit
mode. The MK 12 system was retired in 1992 after the introduction of the MK 21
MOD 1 demand helmet.
1-4.2

Diving Bells. Although open, pressure-balanced diving bells have been used for
several centu­ries, it was not until 1928 that a bell appeared that was capable of
maintaining internal pressure when raised to the surface. In that year, Sir Robert
H. Davis, the British pioneer in diving equipment, designed the Submersible
Decompression Chamber (SDC). The vessel was conceived to reduce the time a
diver had to remain in the water during a lengthy decompression.

The Davis SDC was a steel cylinder capable of holding two men, with two inwardopening hatches, one on the top and one on the bottom. A surface-supplied diver
was deployed over the side in the normal mode and the bell was lowered to a

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U.S. Navy Diving Manual—Volume 1

depth of 60 fsw with the lower hatch open and a tender inside. Surface-supplied air
ventilated the bell and prevented flooding. The diver’s deep decompression stops
were taken in the water and he was assisted into the bell by the tender upon arrival
at 60 fsw. The diver’s gas supply hose and communications cable were removed
from the helmet and passed out of the bell. The lower door was closed and the bell
was lifted to the deck where the diver and tender were decompressed within the
safety and comfort of the bell.
By 1931, the increased decompression times associated with deep diving and the
need for diver comfort resulted in the design of an improved bell system. Davis
designed a three-compartment deck decompression chamber (DDC) to which the
SDC could be mechanically mated, permitting the transfer of the diver under pres­
sure. The DDC provided additional space, a bunk, food and clothing for the diver’s
comfort during a lengthy decompression. This procedure also freed the SDC for
use by another diving team for continuous diving operations.
The SDC-DDC concept was a major advance in diving safety, but was not applied
to American diving technology until the advent of saturation diving. In 1962, E. A.
Link employed a cylindrical, aluminum SDC in conducting his first open-sea satu­
ration diving experiment. In his experiments, Link used the SDC to transport the
diver to and from the sea floor and a DDC for improved diver comfort. American
diving had entered the era of the Deep Diving System (DDS) and advances
and applications of the concept grew at a phenomenal rate in both military and
commercial diving.
1-4.3

Saturation Diving. As divers dove deeper and attempted more ambitious

underwater tasks, a safe method to extend actual working time at depth became
crucial. Examples of satu­ration missions include submarine rescue and salvage,
sea bed implantments, construction, and scientific testing and observation. These
types of operations are characterized by the need for extensive bottom time and,
consequently, are more efficiently conducted using saturation techniques.
1‑4.3.1

Advantages of Saturation Diving. In deep diving operations, decompression is the

most time-consuming factor. For example, a diver working for an hour at 200 fsw
would be required to spend an additional 3 hours and 20 minutes in the water
undergoing the necessary decompression.
However, once a diver becomes saturated with the gases that make decompression
necessary, the diver does not need additional decompression. When the blood and
tissues have absorbed all the gas they can hold at that depth, the time required for
decompression becomes constant. As long as the depth is not increased, additional
time on the bottom is free of any additional decompression.
If a diver could remain under pressure for the entire period of the required task, the
diver would face a lengthy decompression only when completing the project. For
a 40-hour task at 200 fsw, a saturated diver would spend 5 days at bottom pressure
and 2 days in decompression, as opposed to spending 40 days making 1‑hour dives
with long decompression periods using conventional methods.

CHAPTER 1 — History of Diving

1-21

The U.S. Navy developed and proved saturation diving techniques in its Sealab
series. Advanced saturation diving techniques are being developed in ongoing
programs of research and development at the Navy Experimental Diving Unit
(NEDU), Navy Submarine Medical Research Laboratory (NSMRL), and many
institutional and commercial hyperbaric facilities. In addition, saturation diving
using Deep Diving Systems (DDS) is now a proven capability.
1‑4.3.2

1‑4.3.3

Bond’s Saturation Theory. True scientific impetus was first given to the saturation
concept in 1957 when a Navy diving medical officer, Captain George F. Bond,
theorized that the tissues of the body would eventually become saturated with inert
gas if exposure time was long enough. Bond, then a commander and the director
of the Submarine Medical Center at New London, Connecticut, met with Captain
Jacques-Yves Cousteau and determined that the data required to prove the theory
of saturation diving could be developed at the Medical Center.
Genesis Project. With the support of the U.S. Navy, Bond initiated the Genesis

Project to test the theory of saturation diving. A series of experiments, first with
test animals and then with humans, proved that once a diver was saturated, further
extension of bottom time would require no additional decompression time. Project
Genesis proved that men could be sustained for long periods under pressure, and
what was then needed was a means to put this concept to use on the ocean floor.

1‑4.3.4

Developmental Testing. Several test dives were conducted in the early 1960s:

 The first practical open-sea demonstrations of saturation diving were undertaken
in September 1962 by Edward A. Link and Captain Jacques-Yves Cousteau.
 Link’s Man-in-the-Sea program had one man breathing helium-oxygen at 200
fsw for 24 hours in a specially designed diving system.
 Cousteau placed two men in a gas-filled, pressure-balanced underwater habitat
at 33 fsw where they stayed for 169 hours, moving freely in and out of their
deep-house.
 Cousteau’s Conshelf One supported six men breathing nitrogen-oxygen at 35
fsw for 7 days.
 In 1964, Link and Lambertsen conducted a 2-day exposure of two men at 430
fsw.
 Cousteau’s Conshelf Two experiment maintained a group of seven men for 30
days at 36 fsw and 90 fsw with excursion dives to 330 fsw.
1‑4.3.5

Sealab Program. The best known U.S. Navy experimental effort in saturation

diving was the Sealab program.

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U.S. Navy Diving Manual—Volume 1

1‑4.3.5.1

Sealabs I and II. After completing the Genesis Project, the Office of Naval

Research, the Navy Mine Defense Laboratory and Bond’s small staff of volunteers
gathered in Panama City, Florida, where construction and testing of the Sealab I
habitat began in December 1963.

In 1964, Sealab I placed four men underwater for 10 days at an average depth of
192 fsw. The habitat was eventually raised to 81 fsw, where the divers were trans­
ferred to a decompression chamber that was hoisted aboard a four-legged offshore
support structure.
In 1965, Sealab II put three teams of ten men each in a habitat at 205 fsw. Each
team spent 15 days at depth and one man, Astronaut Scott Carpenter, remained for
30 days (see Figure 1‑17).
1‑4.3.5.2

Sealab III. The follow-on seafloor experiment, Sealab III, was planned for 600 fsw.

This huge undertaking required not only extensive development and testing of
equipment but also assessment of human tolerance to high-pressure environments.
To prepare for Sealab III, 28 helium-oxygen saturation dives were performed at
the Navy Experimental Diving Unit to depths of 825 fsw between 1965 and 1968.
In 1968, a record-breaking excursion dive to 1,025 fsw from a saturation depth of
825 fsw was performed at the Navy Experimental Diving Unit (NEDU). The cul­
mination of this series of dives was a 1,000 fsw, 3-day saturation dive conducted
jointly by the U.S. Navy and Duke University in the hyperbaric chambers at Duke.
This was the first time man had been saturated at 1,000 fsw. The Sealab III prepa­
ration experiments showed that men could readily perform useful work at pressures
up to 31 atmospheres and could be returned to normal pressure without harm.

Figure 1-17. Sealab II.

CHAPTER 1 — History of Diving

Figure 1-18. U.S. Navy’s First DDS, SDS-450.

1-23

Reaching the depth intended for the Sealab III habitat required highly specialized
support, including a diving bell to transfer divers under pressure from the habitat to
a pressurized deck decompression chamber. The experiment, however, was marred
by tragedy. Shortly after being compressed to 600 fsw in February 1969, Aquanaut
Berry Cannon convulsed and drowned. This unfortunate accident ended the Navy’s
involvement with sea­floor habitats.
1‑4.3.5.3

Continuing Research. Research and development continues to extend the depth
limit for saturation diving and to improve the diver’s capability. The deepest
dive attained by the U.S. Navy to date was in 1979 when divers from the NEDU
completed a 37-day, 1,800 fsw dive in its Ocean Simulation Facility. The world
record depth for experimental saturation, attained at Duke University in 1981, is
2,250 fsw, and non-Navy open sea dives have been completed to in excess of 2300
fsw. Experiments with mixtures of hydrogen, helium, and oxygen have begun and
the success of this mixture was demonstrated in 1988 in an open-sea dive to 1,650
fsw.

Advanced saturation diving techniques are being developed in ongoing programs
of research and development at NEDU, Navy Submarine Medical Research Labo­
ratory (NSMRL), and many institutional and commercial hyperbaric facilities. In
addition, saturation diving using Deep Diving Systems (DDS) is now a proven
capability.
1-4.4

Deep Diving Systems (DDS). Experiments in saturation technique required
substantial surface support as well as extensive underwater equipment. DDS are a
substantial improvement over previous methods of accomplishing deep undersea
work. The DDS is readily adaptable to saturation techniques and safely maintains
the saturated diver under pressure in a dry environment. Whether employed for
saturation or nonsaturation diving, the Deep Diving System totally eliminates
long decompression periods in the water where the diver is subjected to extended
environmental stress. The diver only remains in the sea for the time spent on a
given task. Additional benefits derived from use of the DDS include eliminating
the need for underwater habitats and increasing operational flexibility for the
surface-support ship.

The Deep Diving System consists of a Deck Decompression Chamber (DDC)
mounted on a surface-support ship. A Personnel Transfer Capsule (PTC) is mated
to the DDC, and the combination is pressurized to a storage depth. Two or more
divers enter the PTC, which is unmated and lowered to the working depth. The
interior of the capsule is pressurized to equal the pressure at depth, a hatch is
opened, and one or more divers swim out to accomplish their work. The divers
can use a self-contained breathing apparatus with a safety tether to the capsule, or
employ a mask and an umbilical that provides breathing gas and communications.
Upon completing the task, the divers enters the capsule, close the hatch and return
to the support ship with the interior of the PTC still at the working pressure. The
capsule is hoisted aboard and mated to the pressurized DDC. The divers enter the
larger, more comfortable DDC via an entry lock. They remain in the DDC until

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U.S. Navy Diving Manual—Volume 1

they must return to the undersea job site. Decompression is carried out comfort­ably
and safely on the support ship.
The Navy developed four deep diving systems: ADS-IV, MK 1 MOD 0, MK 2
MOD 0, and MK 2 MOD 1.
1‑4.4.1

1‑4.4.2

ADS-IV. Several years prior to the Sealab I experiment, the Navy successfully
deployed the Advanced Diving System IV (ADS-IV) (see Figure 1‑18). The ADSIV was a small deep diving system with a depth capability of 450 fsw. The ADSIV was later called the SDS-450.
MK 1 MOD 0. The MK 1 MOD 0 DDS was a small system intended to be used on

the new ATS-1 class salvage ships, and underwent operational evaluation in 1970.
The DDS consisted of a Personnel Transfer Capsule (PTC) (see Figure 1‑19), a
life-support system, main control console and two deck decompression chambers
to handle two teams of two divers each. This system was also used to operationally
evaluate the MK 11 UBA, a semiclosed-circuit mixed-gas apparatus, for saturation
diving. The MK 1 MOD 0 DDS conducted an open-sea dive to 1,148 fsw in 1975.
The MK 1 DDS was not installed on the ATS ships as originally planned, but
placed on a barge and assigned to Harbor Clearance Unit Two. The system went
out of service in 1977.

Figure 1-19. DDS MK 1 Personnel Transfer
Capsule.

1‑4.4.3

Figure 1-20. PTC Handling System,
Elk River.

MK 2 MOD 0. The Sealab III experiment required a much larger and more capable

deep diving system than the MK 1 MOD 0. The MK 2 MOD 0 was constructed
and installed on the support ship Elk River (IX-501). With this system, divers could
be saturated in the deck chamber under close observation and then transported
to the habitat for the stay at depth, or could cycle back and forth between the
deck chamber and the seafloor while working on the exterior of the habitat. The

CHAPTER 1 — History of Diving

1-25

bell could also be used in a non-pressurized observation mode. The divers would
be transported from the habitat to the deck decompression chamber, where final
decompression could take place under close observation.
1‑4.4.4

1-5

MK 2 MOD 1. Experience gained with the MK 2 MOD 0 DDS on board Elk River
(IX-501) (see Figure 1‑20) led to the development of the MK 2 MOD 1, a larger,
more sophisti­cated DDS. The MK 2 MOD 1 DDS supported two four-man teams
for long term saturation diving with a normal depth capability of 850 fsw. The
diving complex consisted of two complete systems, one at starboard and one at
port. Each system had a DDC with a life-support system, a PTC, a main control
console, a strength-power-communications cable (SPCC) and ship support. The
two systems shared a helium-recovery system. The MK 2 MOD 1 was installed on
the ASR 21 Class submarine rescue vessels.

SUBMARINE SALVAGE AND RESCUE

At the beginning of the 20th century, all major navies turned their attention toward
developing a weapon of immense potential—the military submarine. The highly
effective use of the submarine by the German Navy in World War I heightened this
interest and an emphasis was placed on the submarine that continues today.
The U.S. Navy had operated submarines on a limited basis for several years prior
to 1900. As American technology expanded, the U.S. submarine fleet grew rapidly.
However, throughout the period of 1912 to 1939, the development of the Navy’s F,
H, and S class boats was marred by a series of accidents, collisions, and sinkings.
Several of these submarine disasters resulted in a correspondingly rapid growth in
the Navy diving capability.
Until 1912, U.S. Navy divers rarely went below 60 fsw. In that year, Chief Gunner
George D. Stillson set up a program to test Haldane’s diving tables and methods
of stage decompression. A companion goal of the program was to improve Navy
diving equipment. Throughout a 3-year period, first diving in tanks ashore and then
in open water in Long Island Sound from the USS Walkie, the Navy divers went
progressively deeper, eventually reaching 274 fsw.
1-5.1

USS F-4. The experience gained in Stillson’s program was put to dramatic use

in 1915 when the submarine USS F-4 sank near Honolulu, Hawaii. Twenty-one
men lost their lives in the accident and the Navy lost its first boat in 15 years
of submarine oper­ations. Navy divers salvaged the submarine and recovered the
bodies of the crew. The salvage effort incorporated many new techniques, such as
using lifting pontoons. What was most remarkable, however, was that the divers
completed a major salvage effort working at the extreme depth of 304 fsw, using
air as a breathing mixture. The decompression requirements limited bottom time
for each dive to about 10 minutes. Even for such a limited time, nitrogen narcosis
made it difficult for the divers to concentrate on their work.
The publication of the first U.S. Navy Diving Manual and the establishment of a
Navy Diving School at Newport, Rhode Island, were the direct outgrowth of expe­
rience gained in the test program and the USS F-4 salvage. When the U.S. entered
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U.S. Navy Diving Manual—Volume 1

World War I, the staff and graduates of the school were sent to Europe, where they
conducted various salvage operations along the coast of France.
The physiological problems encountered in the salvage of the USS F-4 clearly
demonstrated the limitations of breathing air during deep dives. Continuing concern
that submarine rescue and salvage would be required at great depth focused Navy
attention on the need for a new diver breathing medium.
1-5.2

USS S-51. In September of 1925, the USS S-51 submarine was rammed by a

passenger liner and sunk in 132 fsw off Block Island, Rhode Island. Public pressure
to raise the submarine and recover the bodies of the crew was intense. Navy diving
was put in sharp focus, realizing it had only 20 divers who were qualified to go
deeper than 90 fsw. Diver training programs had been cut at the end of World War
I and the school had not been reinstituted.
Salvage of the USS S-51 covered a 10-month span of difficult and hazardous
diving, and a special diver training course was made part of the operation. The
submarine was finally raised and towed to the Brooklyn Navy Yard in New York.
Interest in diving was high once again and the Naval School, Diving and Salvage,
was reestablished at the Washington Navy Yard in 1927. At the same time, the
Navy brought together its existing diving technology and experimental work by
shifting the Experimental Diving Unit (EDU), which had been working with the
Bureau of Mines in Pennsylvania, to the Navy Yard as well. In the following years,
EDU developed the U.S. Navy Air Decompression Tables, which have become
the accepted world standard and continued developmental work in helium-oxygen
breathing mixtures for deeper diving.
Losing the USS F-4 and USS S-51 provided the impetus for expanding the Navy’s
diving ability. However, the Navy’s inability to rescue men trapped in a disabled
submarine was not confronted until another major submarine disaster occurred.

1-5.3

USS S-4. In 1927, the Navy lost the submarine USS S-4 in a collision with the

Coast Guard cutter USS Paulding. The first divers to reach the submarine in 102
fsw, 22 hours after the sinking, exchanged signals with the men trapped inside.
The submarine had a hull fitting designed to take an air hose from the surface,
but what had looked feasible in theory proved too difficult in reality. With stormy
seas causing repeated delays, the divers could not make the hose connection until
it was too late. All of the men aboard the USS S-4 had died. Even had the hose
connection been made in time, rescuing the crew would have posed a significant
problem.

The USS S-4 was salvaged after a major effort and the fate of the crew spurred
several efforts toward preventing a similar disaster. LT C.B. Momsen, a subma­
rine officer, developed the escape lung that bears his name. It was given its first
operational test in 1929 when 26 officers and men successfully surfaced from an
intentionally bottomed submarine.

CHAPTER 1 — History of Diving

1-27

1-5.4

USS Squalus. The Navy pushed for development of a rescue chamber that was

essentially a diving bell with special fittings for connection to a submarine deck
hatch. The apparatus, called the McCann-Erickson Rescue Chamber, was proven
in 1939 when the USS Squalus, carrying a crew of 50, sank in 243 fsw. The rescue
chamber made four trips and safely brought 33 men to the surface. (The rest of
the crew, trapped in the flooded after-section of the submarine, had perished in the
sinking.)

The USS Squalus was raised by salvage divers (see Figure 1‑21). This salvage
and rescue operation marked the first operational use of HeO2 in salvage diving.
One of the primary missions of salvage divers was to attach a down-haul cable
for the Submarine Rescue Chamber (SRC). Following renovation, the submarine,
renamed USS Sailfish, compiled a proud record in World War II.

Figure 1-21. Recovery of the Squalus.

1-5.5

USS Thresher. Just as the loss of the USS F-4, USS S-51, USS S-4 and the sinking

of the USS Squalus caused an increased concern in Navy diving in the 1920s and
1930s, a submarine disaster of major proportions had a profound effect on the
development of new diving equipment and techniques in the postwar period. This
was the loss of the nuclear attack submarine USS Thresher and all her crew in
April 1963. The submarine sank in 8,400 fsw, a depth beyond the survival limit of
the hull and far beyond the capability of any existing rescue apparatus.
An extensive search was initiated to locate the submarine and determine the cause
of the sinking. The first signs of the USS Thresher were located and photographed
a month after the disaster. Collection of debris and photographic coverage of the
wreck continued for about a year.
Two special study groups were formed as a result of the sinking. The first was a
Court of Inquiry, which attributed probable cause to a piping system failure. The

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U.S. Navy Diving Manual—Volume 1

second, the Deep Submergence Review Group (DSRG), was formed to assess the
Navy’s undersea capabilities. Four general areas were examined—search, rescue,
recovery of small and large objects, and the Man-in-the-Sea concept. The basic
recommendations of the DSRG called for a vast effort to improve the Navy’s
capabilities in these four areas.
1-5.6

Deep Submergence Systems Project. Direct action on the recommendations of

the DSRG came with the formation of the Deep Submergence Systems Project
(DSSP) in 1964 and an expanded interest regarding diving and undersea activity
throughout the Navy.
Submarine rescue capabilities have been substantially improved with the develop­
ment of the Deep Submergence Rescue Vehicle (DSRV) which became operational
in 1972. This deep-diving craft is air-transportable, highly instru­mented, and
capable of diving to 5,000 fsw and rescues to 2,500 fsw.
Three additional significant areas of achievement for the Deep Submergence
Systems Project have been that of Saturation Diving, the development of Deep
Diving Systems, and progress in advanced diving equipment design.
1-6

SALVAGE DIVING
1-6.1
1‑6.1.1

World War II Era.
Pearl Harbor. Navy divers were plunged into the war with the Japanese raid on
Pearl Harbor. The raid began at 0755 on 7 December 1941; by 0915 that same
morning, the first salvage teams were cutting through the hull of the overturned
battleship USS Oklahoma to rescue trapped sailors. Teams of divers worked to
recover ammuni­tion from the magazines of sunken ships, to be ready in the event
of a second attack.

The immense salvage effort that followed at Pearl Harbor was highly successful.
Most of the 101 ships in the harbor at the time of the attack sustained damage. The
battleships, one of the primary targets of the raid, were hardest hit. Six battleships
were sunk and one was heavily damaged. Four were salvaged and returned to the
fleet for combat duty; the former battleships USS Arizona and USS Utah could not
be salvaged. The USS Oklahoma was righted and refloated but sank en route to a
shipyard in the U.S.
Battleships were not the only ships salvaged. Throughout 1942 and part of
1943, Navy divers worked on destroyers, supply ships, and other badly needed
vessels, often using makeshift shallow water apparatus inside water and gas-filled
compartments. In the Pearl Harbor effort, Navy divers spent 16,000 hours under­
water during 4,000 dives. Contract civilian divers contributed another 4,000 diving
hours.
1‑6.1.2

USS Lafayette. While divers in the Pacific were hard at work at Pearl Harbor,

a major challenge was presented to the divers on the East Coast. The interned
French passenger liner Normandie (rechristened as the USS Lafayette) caught fire

CHAPTER 1 — History of Diving

1-29

alongside New York City’s Pier 88. Losing stability from the tons of water poured
on the fire, the ship capsized at her berth.
The ship had to be salvaged to clear the vitally needed pier. The Navy took advan­tage
of this unique training opportunity by instituting a new diving and salvage school
at the site. The Naval Training School (Salvage) was established in September
1942 and was transferred to Bayonne, New Jersey in 1946.
1‑6.1.3

1-6.2

Other Diving Missions. Salvage operations were not the only missions assigned
to Navy divers during the war. Many dives were made to inspect sunken enemy
ships and to recover mate­rials such as code books or other intelligence items. One
Japanese cruiser yielded not only $500,000 in yen, but also provided valuable
information concerning plans for the defense of Japan against the anticipated
Allied invasion.
Vietnam Era. Harbor Clearance Unit One (HCU 1) was commissioned 1 February

1966 to provide mobile salvage capability in direct support of combat operations
in Vietnam. Homeported at Naval Base Subic Bay, Philippines, HCU 1 was dedi­
cated primarily to restoring seaports and rivers to navigable condition following
their loss or diminished use through combat action.
Beginning as a small cadre of personnel, HCU 1 quickly grew in size to over 260
personnel, as combat operations in littoral environment intensified. At its peak, the
unit consisted of five Harbor Clearance teams of 20 to 22 personnel each and a
varied armada of specialized vessels within the Vietnam combat zone.
As their World War II predecessors before them, the salvors of HCU 1 left an
impressive legacy of combat salvage accomplishments. HCU 1 salvaged hundreds
of small craft, barges, and downed aircraft; refloated many stranded U.S. Military
and merchant vessels; cleared obstructed piers, shipping channels, and bridges;
and performed numerous underwater repairs to ships operating in the combat zone.

Throughout the colorful history of HCU 1 and her East Coast sister HCU 2, the vital
role salvage forces play in littoral combat operations was clearly demon­strated.
Mobile Diving and Salvage Unit One and Two, the modern-day descendants of
the Vietnam era Harbor Clearance Units, have a proud and distin­guished history of
combat salvage operations.
1-7

OPEN-SEA DEEP DIVING RECORDS

Diving records have been set and broken with increasing regularity since the early
1900s:
n 1915. The 300-fsw mark was exceeded. Three U.S. Navy divers, F. Crilley,
W.F. Loughman, and F.C. Nielson, reached 304 fsw using the MK V dress.
n 1972. The MK 2 MOD 0 DDS set the in-water record of 1,010 fsw.
n 1975. Divers using the MK 1 Deep Dive System descended to 1,148 fsw.

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U.S. Navy Diving Manual—Volume 1

n 1977. A French dive team broke the open-sea record with 1,643 fsw.
n 1981. The deepest salvage operation made with divers was 803 fsw when
British divers retrieved 431 gold ingots from the wreck of HMS Edinburgh,
sunk during World War II.
n Present. Commercial open water diving operations to over 1,000 fsw.
1-8

SUMMARY

Throughout the evolution of diving, from the earliest breath-holding sponge diver
to the modern saturation diver, the basic reasons for diving have not changed.
National defense, commerce, and science continue to provide the underlying basis
for the development of diving. What has changed and continues to change radi­cally
is diving technology.
Each person who prepares for a dive has the opportunity and obligation to take
along the knowledge of his or her predecessors that was gained through difficult
and dangerous experience. The modern diver must have a broad understanding of
the physical properties of the undersea environment and a detailed knowledge of
his or her own physiology and how it is affected by the environment. Divers must
learn to adapt to environmental conditions to successfully carry out their missions.
Much of the diver’s practical education will come from experience. However,
before a diver can gain this experience, he or she must build a basic foundation
from certain principles of physics, chemistry and physiology and must understand
the application of these principles to the profession of diving.

CHAPTER 1 — History of Diving

1-31

PAGE LEFT BLANK INTENTIONALLY

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U.S. Navy Diving Manual—Volume 1

CHAPTER 2

Underwater Physics
2-1

INTRODUCTION
2-1.1

Purpose. This chapter describes the laws of physics as they affect humans in the

water.

2-1.2

2-2

Scope. A thorough understanding of the principles outlined in this chapter is
essential to safe and effective diving performance.

PHYSICS

Humans readily function within the narrow atmospheric envelope present at the
earth’s surface and are seldom concerned with survival requirements. Outside the
boundaries of the envelope, the environment is hostile and our existence depends
on our ability to counteract threatening forces. To function safely, divers must
understand the characteristics of the subsea environment and the techniques that
can be used to modify its effects. To accomplish this, a diver must have a basic
knowledge of physics—the science of matter and energy. Of particular importance
to a diver are the behavior of gases, the principles of buoyancy, and the properties
of heat, light, and sound.
2-3

MATTER

Matter is anything that occupies space and has mass, and is the building block of
the physical world. Energy is required to cause matter to change course or speed.
The diver, the diver’s air supply, everything that supports him or her, and the
surrounding environment is composed of matter.
2-3.1

Elements. An element is the simplest form of matter that exhibits distinct physical

and chem­ical properties. An element cannot be broken down by chemical means
into other, more basic forms. Scientists have identified more than 100 elements
in the phys­ical universe. Elements combine to form the more than four million
substances known to man.
2-3.2

Atoms. The atom is the smallest particle of matter that carries the specific properties

of an element. Atoms are made up of electrically charged particles known as
protons, neutrons, and electrons. Protons have a positive charge, neutrons have a
neutral charge, and electrons have a negative charge.

2-3.3

Molecules. Molecules are formed when atoms group together (Figure 2-1).
Molecules usually exhibit properties different from any of the contributing atoms.
For example, when two hydrogen atoms combine with one oxygen atom, a new
substance—water—is formed. Some molecules are active and try to combine with
many of the other molecules that surround them. Other molecules are inert and

CHAPTER 2 — Underwater Physics

2-1

H atom

O2 molecule
(2 oxygen atoms)

O atom

H2O molecule
(2 hydrogen atoms
+ 1 oxygen atom)

Figure 2-1. Molecules. Two similar atoms
combine to form an oxygen molecule
while the atoms of two different elements,
hydrogen and oxygen, combine to form a
water molecule.

Solid

Liquid

Gas

Figure 2-2. The Three States of Matter.

do not naturally combine with other substances. The presence of inert elements
in breathing mixtures is important when calculating a diver’s decompression
obligations.
2-3.4

The Three States of Matter. Matter can exist in one of three natural states: solid,

liquid, or gas (Figure 2-2). A solid has a definite size and shape. A liquid has a
definite volume, but takes the shape of the container. Gas has neither definite shape
nor volume, but will expand to fill a container. Gases and liquids are collectively
referred to as fluids.

The physical state of a substance depends primarily upon temperature and partially
upon pressure. A solid is the coolest of the three states, with its molecules rigidly
aligned in fixed patterns. The molecules move, but their motion is like a constant
vibration. As heat is added the molecules increase their motion, slip apart from
each other and move around; the solid becomes a liquid. A few of the mole­cules
will spontaneously leave the surface of the liquid and become a gas. When the
substance reaches its boiling point, the molecules are moving very rapidly in all
directions and the liquid is quickly transformed into a gas. Lowering the temperature
reverses the sequence. As the gas molecules cool, their motion is reduced and the
gas condenses into a liquid. As the temperature continues to fall, the liquid reaches
the freezing point and transforms to a solid state.
2-4

MEASUREMENT

Physics relies heavily upon standards of comparison of one state of matter or
energy to another. To apply the principles of physics, divers must be able to employ
a variety of units of measurement.
2-4.1

Measurement Systems. Two systems of measurement are widely used throughout

the world. Although the English System is commonly used in the United States,
the most common system of measurement in the world is the International System
of Units. The Interna­tional System of Units, or SI system, is a modernized metric
system designated in 1960 by the General Conference on Weights and Measures.
The SI system is decimal based with all its units related, so that it is not necessary
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U.S. Navy Diving Manual — Volume 1

to use calcula­tions to change from one unit to another. The SI system changes one
of its units of measurement to another by moving the decimal point, rather than by
the lengthy calculations necessary in the English System. Because measurements
are often reported in units of the English system, it is important to be able to
convert them to SI units. Measurements can be converted from one system to
another by using the conversion factors in Table 2-10 through 2-18.
2-4.2

Temperature Measurements. While the English System of weights and measures

uses the Fahrenheit (°F) temperature scale, the Celsius (°C) scale is the one most
commonly used in scien­tific work. Both scales are based upon the freezing and
boiling points of water. The freezing point of water is 32°F or 0°C; the boiling
point of water is 212°F or 100°C. Temperature conversion formulas and charts are
found in Table 2-18.
Absolute temperature values are used
when employing the ideal gas laws.
The absolute temperature scales are
based upon absolute zero. Absolute
zero is the lowest temperature that
could possibly be reached at which all
molecular motion would cease (Figure
2‑3).
2‑4.2.1

212° F

100° C

373 K

672o R

32° F

0° C

273 K

492 R

o

Kelvin Scale. One example of an

absolute tempera­
ture scale is the
Kelvin scale, which has the same
size degrees as the Celsius scale. The
freezing point of water is 273°K and
boiling point of water is 373°K. Use
this formula to convert from Celsius to
absolute temperature (Kelvin):

Figure 2-3. Temperature Scales.
Fahrenheit, Celsius, Kelvin, and Rankine
temperature scales showing the freezing
and boiling points of water.

Kelvin (K) = °C + 273.
2‑4.2.2

Rankine Scale. The Rankine scale is another absolute temperature scale, which

has the same size degrees as the Fahrenheit scale. The freezing point of water is
492°R and the boiling point of water is 672°R. Use this formula to convert from
Fahrenheit to absolute temperature (degrees Rankine, °R):
°R = °F + 460

2-4.3

Gas Measurements. When measuring gas, actual cubic feet (acf) of a gas refers to

the quantity of a gas at ambient conditions. The most common unit of measurement
for gas in the United States is standard cubic feet (scf). Standard cubic feet relates
the quantity measurement of a gas under pressure to a specific condition. The
specific condi­tion is a common basis for comparison. For air, the standard cubic
foot is measured at 60°F and 14.696 psia.

CHAPTER 2 — Underwater Physics

2-3

2-5

ENERGY

Energy is the capacity to do work. The six basic types of energy are mechanical,
heat, light, chemical, electromagnetic, and nuclear, and may appear in a variety
of forms (Figure 2‑4). Energy is a vast and complex aspect of physics beyond the
scope of this manual. Consequently, this chapter only covers a few aspects of light,
heat, and mechanical energy because of their unusual effects underwater and their
impact on diving.

Figure 2-4. The Six Forms of Energy.

2-4

U.S. Navy Diving Manual — Volume 1

2-5.1

2-5.2

Conservation of Energy. The Law of the Conservation of Energy, formulated in
the 1840s, states that energy in the universe can neither be created nor destroyed.
Energy can be changed, however, from one form to another.
Classifications of Energy. The two general classifications of energy are potential

energy and kinetic energy. Potential energy is due to position. An automobile
parked on a hill with its brakes set possesses potential energy. Kinetic energy is
energy of motion. An automobile rolling on a flat road possesses kinetic energy
while it is moving.

2-6

LIGHT ENERGY IN DIVING

Refraction, turbidity of the water, salinity, and pollution all contribute to the
distance, size, shape, and color perception of underwater objects. Divers must
understand the factors affecting underwater visual perception, and must realize
that distance perception is very likely to be inaccurate.
2-6.1

Light passing from an
object bends as it passes through the
diver’s faceplate and the air in his
mask (Figure 2-5). This phenomenon
is called refraction, and occurs because
light travels faster in air than in water.
Although the refraction that occurs
between the water and the air in the
diver’s face mask produces undesir­able
perceptual inaccuracies, air is essential
for vision. When a diver loses his face
mask, his eyes are immersed in water,
which has about the same refrac­
tive
index as the eye. Consequently, the light
is not focused normally and the diver’s
vision is reduced to a level that would be
classified as legally blind on the surface.
Refraction.

Water

Figure 2-5. Objects Underwater
Appear Closer.

Refraction can make objects appear closer
than they really are. A distant object will appear to be approximately three-quarters
of its actual distance. At greater distances, the effects of refraction may be reversed,
making objects appear farther away than they actually are. Reduced brightness and
contrast combine with refrac­tion to affect visual distance relationships.
Refraction can also affect perception of size and shape. Generally, underwater
objects appear to be about 30 percent larger than they actually are. Refraction
effects are greater for objects off to the side in the field of view. This distortion
interferes with hand-eye coordination, and explains why grasping objects under­
water is sometimes difficult for a diver. Experience and training can help a diver
learn to compensate for the misinterpretation of size, distance, and shape caused
by refraction.

CHAPTER 2 — Underwater Physics

2-5

2-6.2

Turbidity of Water. Water turbidity can also profoundly influence underwater

vision and distance perception. The more turbid the water, the shorter the distance
at which the reversal from underestimation to overestimation occurs. For example,
in highly turbid water, the distance of objects at 3 or 4 feet may be overestimated;
in moder­ately turbid water, the change might occur at 20 to 25 feet and in very
clear water, objects as far away as 50 to 70 feet might appear closer than they
actually are. Generally speaking, the closer the object, the more it will appear to be
too close, and the more turbid the water, the greater the tendency to see it as too far
away.
2-6.3

2-6.4

Diffusion. Light scattering is intensified underwater. Light rays are diffused
and scattered by the water molecules and particulate matter. At times diffusion
is helpful because it scatters light into areas that otherwise would be in shadow
or have no illumination. Normally, however, diffusion interferes with vision and
underwater photography because the backscatter reduces the contrast between an
object and its background. The loss of contrast is the major reason why vision
underwater is so much more restricted than it is in air. Similar degrees of scattering
occur in air only in unusual conditions such as heavy fog or smoke.
Color Visibility. Object size and distance are not the only characteristics distorted

underwater. A variety of factors may combine to alter a diver’s color perception.
Painting objects different colors is an obvious means of changing their visibility
by enhancing their contrast with the surroundings, or by camouflaging them to
merge with the back­ground. Determining the most and least visible colors is much
more complicated underwater than in air.
Colors are filtered out of light as it enters the water and travels to depth. Red light
is filtered out at relatively shallow depths. Orange is filtered out next, followed
by yellow, green, and then blue. Water depth is not the only factor affecting the
filtering of colors. Salinity, turbidity, size of the particles suspended in the water,
and pollution all affect the color-filtering properties of water. Color changes vary
from one body of water to another, and become more pronounced as the amount of
water between the observer and the object increases.
The components of any underwater scene, such as weeds, rocks, and encrusting
animals, generally appear to be the same color as the depth or viewing range
increases. Objects become distinguishable only by differences in brightness and
not color. Contrast becomes the most important factor in visibility; even very large
objects may be undetectable if their brightness is similar to that of the background.
2-7

MECHANICAL ENERGY IN DIVING

Mechanical energy mostly affects divers in the form of sound. Sound is a periodic
motion or pressure change transmitted through a gas, a liquid, or a solid. Because
liquid is denser than gas, more energy is required to disturb its equilibrium. Once
this disturbance takes place, sound travels farther and faster in the denser medium.
Several aspects of sound underwater are of interest to the working diver.

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U.S. Navy Diving Manual — Volume 1

2-7.1

Water Temperature and Sound. In any body of water, there may be two or more

distinct contiguous layers of water at different temperatures; these layers are
known as thermoclines. The colder a layer of water, the greater its density. As
the difference in density between layers increases, the sound energy transmitted
between them decreases. This means that a sound heard 50 meters from its source
within one layer may be inaudible a few meters from its source if the diver is in
another layer.

2-7.2

Water Depth and Sound. In shallow water or in enclosed spaces, reflections and

reverberations from the air/water and object/water interfaces produce anomalies
in the sound field, such as echoes, dead spots, and sound nodes. When swimming
in shallow water, among coral heads, or in enclosed spaces, a diver can expect
periodic losses in acoustic communication signals and disruption of acoustic
navigation beacons. The problem becomes more pronounced as the frequency of
the signal increases.
Because sound travels so quickly underwater (4,921 feet per second), human ears
cannot detect the difference in time of arrival of a sound at each ear. Consequently,
a diver cannot always locate the direction of a sound source. This disadvantage can
have serious consequences for a diver or swimmer trying to locate an object or a
source of danger, such as a powerboat.

2‑7.2.1

Diver Work and Noise. Open-circuit SCUBA affects sound reception by producing
high noise levels at the diver’s head and by creating a screen of bubbles that
reduces the effective sound pressure level (SPL). When several divers are working
in the same area, the noise and bubbles affect communication signals more for
some divers than for others, depending on the position of the divers in relation to
the communicator and to each other.

A neoprene wet suit is an effective barrier to sound above 1,000 Hz and it becomes
more of a barrier as frequency increases. This problem can be overcome by exposing
a small area of the head either by cutting holes at the ears of the suit or by folding
a small flap away from the surface.
2‑7.2.2

Pressure Waves. Sound is transmitted through water as a series of pressure waves.

High-intensity sound is transmitted by correspondingly high-intensity pressure
waves. A high-pressure wave transmitted from the water surrounding a diver to
the open spaces within the body (ears, sinuses, lungs) may increase the pressure
within these open spaces, causing injury. Underwater explosions and sonar can
create high-intensity sound or pressure waves. Low intensity sonar, such as depth
finders and fish finders, do not produce pressure waves intense enough to endanger
divers. However, anti-submarine sonar-equipped ships do pulse dangerous, highintensity pressure waves.

Diving operations must be suspended if a high-powered sonar transponder is being
operated in the area. When using a diver-held pinger system, divers are advised
to wear the standard ¼-inch neoprene hood for ear protection. Experi­ments have
shown that such a hood offers adequate protection when the ultrasonic pulses are
of 4-millisecond duration, repeated once per second for acoustic source levels up
CHAPTER 2 — Underwater Physics

2-7

to 100 watts, at head-to-source distances as short as 0.5 feet (Pence and Sparks,
1978).
2-7.3

Underwater Explosions. An underwater explosion creates a series of waves that

are transmitted as hydraulic shock waves in the water, and as seismic waves in the
seabed. The hydraulic shock wave of an underwater explosion consists of an initial
wave followed by further pressure waves of diminishing intensity. The initial
high-intensity shock wave is the result of the violent creation and liberation of a
large volume of gas, in the form of a gas pocket, at high pressure and temperature.
Subsequent pressure waves are caused by rapid gas expansion in a non-compress­
ible environment, causing a sequence of contractions and expansions as the gas
pocket rises to the surface.
The initial high-intensity shock wave is the most dangerous; as it travels outward
from the source of the explosion, it loses its intensity. Less severe pressure waves
closely follow the initial shock wave. Considerable turbulence and movement of
the water in the area of the explosion are evident for an extended time after the
detonation.
2‑7.3.1

Type of Explosive and Size of the Charge. Some explosives have characteristics

of high brisance (shattering power in the immediate vicinity of the explosion) with
less power at long range, while the bri­sance of others is reduced to increase their
power over a greater area. Those with high brisance generally are used for cutting
or shattering purposes, while high-power, low-­brisance explosives are used in
depth charges and sea mines where the target may not be in immediate contact and
the ability to inflict damage over a greater area is an advantage. The high-brisance
explosives create a high-level shock and pressure waves of short duration over
a limited area. Low brisance explosives create a less intense shock and pressure
waves of long duration over a greater area.
2‑7.3.2

Characteristics of the Seabed. Aside from the fact that rock or other bottom debris

may be propelled through the water or into the air with shallow-placed charges,
bottom conditions can affect an explosion’s pressure waves. A soft bottom tends
to dampen reflected shock and pressure waves, while a hard, rock bottom may
amplify the effect. Rock strata, ridges and other topographical features of the
seabed may affect the direction of the shock and pressure waves, and may also
produce secondary reflecting waves.
2‑7.3.3

Location of the Explosive Charge. Research has indicated that the magnitude of

shock and pressure waves generated from charges freely suspended in water is
considerably greater than that from charges placed in drill holes in rock or coral.

2‑7.3.4

2‑7.3.5

Water Depth. At great depth, the shock and pressure waves are drawn out by the
greater water volume and are thus reduced in intensity. An explosion near the
surface is not weakened to the same degree.
Distance from the Explosion. In general, the farther away from the explosion, the

greater the attenuation of the shock and pressure waves and the less the intensity.
This factor must be considered in the context of bottom conditions, depth of

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U.S. Navy Diving Manual — Volume 1

water, and reflection of shock and pressure waves from underwater structures and
topographical features.
2‑7.3.6

Degree of Submersion of the Diver. A fully submerged diver receives the total

effect of the shock and pressure waves passing over the body. A partially submerged
diver whose head and upper body are out of the water, may experience a reduced
effect of the shock and pressure waves on the lungs, ears, and sinuses. However,
air will transmit some portion of the explosive shock and pressure waves. The
head, lungs, and intestines are the parts of the body most vulnerable to the pressure
effects of an explosion. A pres­sure wave of 500 pounds per square inch is sufficient
to cause serious injury to the lungs and intestinal tract, and one greater than 2,000
pounds per square inch will cause certain death. Even a pressure wave of 500
pounds per square inch could cause fatal injury under certain circumstances.
2‑7.3.7

Estimating Explosion Pressure on a Diver. There are various formulas for
estimating the pressure wave resulting from an explosion of TNT. The equations
vary in format and the results illustrate that the technique for estimation is only an
approximation. Moreover, these formulas relate to TNT and are not applicable to
other types of explosives.

The formula below (Greenbaum and Hoff, 1966) is one method of estimating the
pressure on a diver resulting from an explosion of tetryl or TNT.

P=
Where:
P
=
W =
r
=

13, 000 3 W
r
pressure on the diver in pounds per square inch
weight of the explosive (TNT) in pounds
range of the diver from the explosion in feet

Sample Problem. Determine the pressure exerted by a 45-pound charge at a

distance of 80 feet.

1. Substitute the known values.

P=

13, 000 3 45
80

2. Solve for the pressure exerted.

13, 000 3 45
P=
80
13, 000 · 3.56
=
80
= 578.5
Round up to 579 psi.

CHAPTER 2 — Underwater Physics

2-9

A 45-pound charge exerts a pressure of 579 pounds per square inch at a distance
of 80 feet.
2‑7.3.8

Minimizing the Effects of an Explosion. When expecting an underwater blast, the

diver shall get out of the water and out of range of the blast whenever possible.
If the diver must be in the water, it is prudent to limit the pressure he experiences
from the explosion to less than 50 pounds per square inch. To minimize the effects,
the diver can position himself with feet pointing toward and head directly away
from the explosion. The head and upper section of the body should be out of the
water or the diver should float on his back with his head out of the water.

2-8

HEAT ENERGY IN DIVING

Heat is crucial to man’s environmental balance. The human body functions within
only a very narrow range of internal temperature and contains delicate mecha­nisms
to control that temperature.
Heat is a form of energy associated with and proportional to the molecular motion
of a substance. It is closely related to temperature, but must be distinguished from
temperature because different substances do not necessarily contain the same heat
energy even though their temperatures are the same.
Heat is generated in many ways. Burning fuels, chemical reactions, friction, and
electricity all generate heat. Heat is transmitted from one place to another by
conduction, convection, and radiation.
2-8.1

Conduction, Convection, and Radiation. Conduction is the transmission of heat by
direct contact. Because water is an excellent heat conductor, an unprotected diver
can lose a great deal of body heat to the surrounding water by direct conduction.

Convection is the transfer of heat by the movement of heated fluids. Most home
heating systems operate on the principle of convection, setting up a flow of air
currents based on the natural tendency of warm air to rise and cool air to fall. A
diver seated on the bottom of a tank of water in a cold room can lose heat not only
by direct conduction to the water, but also by convection currents in the water. The
warmed water next to his body will rise and be replaced by colder water passing
along the walls of the tank. Upon reaching the surface, the warmed water will lose
heat to the cooler surroundings. Once cooled, the water will sink only to be warmed
again as part of a continuing cycle.
Radiation is heat transmission by electromagnetic waves of energy. Every warm
object gives off waves of electromagnetic energy, which is absorbed by cool
objects. Heat from the sun, electric heaters, and fireplaces is primarily radiant
heat.
2-8.2

2-10

Heat Transfer Rate. To divers, conduction is the most significant means of
transmitting heat. The rate at which heat is transferred by conduction depends on
two basic factors:

U.S. Navy Diving Manual — Volume 1

n The difference in temperature between the warmer and cooler material
n The thermal conductivity of the materials
Not all substances conduct heat at the same rate. Iron, helium, and water are
excel­lent heat conductors while air is a very poor conductor. Placing a poor heat
conductor between a source of heat and another substance insulates the substance
and slows the transfer of heat. Materials such as wool and foam rubber insulate the
human body and are effective because they contain thousands of pockets of trapped
air. The air pockets are too small to be subject to convective currents, but block
conductive transfer of heat.
2-8.3

Diver Body Temperature. A diver will start to become chilled when the water
temperature falls below a seemingly comfortable 70°F (21°C). Below 70°F, a
diver wearing only a swim­ming suit loses heat to the water faster than his body
can replace it. Unless he is provided some protection or insulation, he may quickly
experience difficulties. A chilled diver cannot work efficiently or think clearly, and
is more susceptible to decompression sickness.

Suit compression, increased gas density, thermal conductivity of breathing gases,
and respiratory heat loss are contributory factors in maintaining a diver’s body
temperature. Cellular neoprene wet suits lose a major portion of their insulating
properties as depth increases and the material compresses. As a consequence, it is
often necessary to employ a thicker suit, a dry suit, or a hot water suit for extended
exposures to cold water.
The heat transmission characteristics of an individual gas are directly proportional
to its density. Therefore, the heat lost through gas insulating barriers and respira­
tory heat lost to the surrounding areas increase with depth. The heat loss is further
aggravated when high thermal conductivity gases, such as helium-oxygen, are used
for breathing. The respiratory heat loss alone increases from 10 percent of the body’s
heat generating capacity at one ata (atmosphere absolute), to 28 percent at 7 ata,
to 50 percent at 21 ata when breathing helium-oxygen. Under these circum­stances,
standard insulating materials are insufficient to maintain body temperatures and
supplementary heat must be supplied to the body surface and respiratory gas.
2-9

PRESSURE IN DIVING

Pressure is defined as a force acting upon a particular area of matter. It is typically
measured in pounds per square inch (psi) in the English system and Newton per
square centimeter (N/cm2) in the System International (SI). Underwater pressure is
a result of the weight of the water above the diver and the weight of the atmo­sphere
over the water. There is one concept that must be remembered at all times—any
diver, at any depth, must be in pressure balance with the forces at that depth. The
body can only function normally when the pressure difference between the forces
acting inside of the diver’s body and forces acting outside is very small. Pressure,
whether of the atmosphere, seawater, or the diver’s breathing gases, must always
be thought of in terms of maintaining pressure balance.

CHAPTER 2 — Underwater Physics

2-11

2-9.1

Atmospheric Pressure. Given that one atmosphere is equal to 33 feet of sea

water or 14.7 psi, 14.7 psi divided by 33 feet equals 0.445 psi per foot. Thus, for
every foot of sea water, the total pressure is increased by 0.445 psi. Atmospheric
pressure is constant at sea level; minor fluctuations caused by the weather are
usually ignored. Atmospheric pressure acts on all things in all directions.
Most pressure gauges measure differential pressure between the inside and outside
of the gauge. Thus, the atmospheric pressure does not register on the pressure gauge
of a cylinder of compressed air. The initial air in the cylinder and the gauge are
already under a base pressure of one atmosphere (14.7 psi or 10N/cm2). The gauge
measures the pressure difference between the atmosphere and the increased air
pressure in the tank. This reading is called gauge pressure and for most purposes
it is sufficient.
In diving, however, it is important to include atmospheric pressure in computa­
tions. This total pressure is called absolute pressure and is normally expressed in
units of atmospheres. The distinction is important and pressure must be identified
as either gauge (psig) or absolute (psia). When the type of pressure is identified
only as psi, it refers to gauge pressure. Table 2‑10 contains conversion factors for
pressure measurement units.
2-9.2

Terms Used to Describe Gas Pressure. Four terms are used to describe gas

pressure:

n Atmospheric. Standard atmosphere, usually expressed as 10N/cm2, 14.7 psi, or
one atmosphere absolute (1 ata).
n Barometric. Essentially the same as atmospheric but varying with the weather
and expressed in terms of the height of a column of mercury. Standard pressure
is equal to 29.92 inches of mercury, 760 millimeters of mercury, or 1013
millibars.
n Gauge. Indicates the difference between atmospheric pressure and the pressure
being measured.
n Absolute. The total pressure being exerted, i.e., gauge pressure plus atmospheric
pressure.
2-9.3

Hydrostatic Pressure. The water on the surface pushes down on the water

below and so on down to the bottom where, at the greatest depths of the ocean
(approximately 36,000 fsw), the pressure is more than 8 tons per square inch
(1,100 ata). The pressure due to the weight of a water column is referred to as
hydrostatic pressure.
The pressure of seawater at a depth of 33 feet equals one atmosphere. The absolute
pressure, which is a combination of atmospheric and water pressure for that depth,
is two atmospheres. For every additional 33 feet of depth, another atmosphere of
pressure (14.7 psi) is encountered. Thus, at 99 feet, the absolute pressure is equal

2-12

U.S. Navy Diving Manual — Volume 1

to four atmospheres. Table 2‑1 and Figure 2‑7 shows how pressure increases with
depth.
Table 2‑1. Pressure Chart.
Depth Gauge Pressure

Atmospheric Pressure

Absolute Pressure

0

One Atmosphere

1 ata (14.7 psia)

33 fsw

+ One Atmosphere

2 ata (29.4 psia)

66 fsw

+ One Atmosphere

3 ata (44.1 psia)

99 fsw

+ One Atmosphere

4 ata (58.8 psia)

The change in pressure with depth is so pronounced that the feet of a 6-foot tall
person standing underwater are exposed to pressure that is almost 3 pounds per
square inch greater than that exerted at his head.
2-9.4

Buoyancy. Buoyancy is the force that makes objects float. It was first defined by

the Greek mathematician Archimedes, who established that “Any object wholly or
partly immersed in a fluid is buoyed up by a force equal to the weight of the fluid
displaced by the object.” This is known as Archimedes’ Principle and applies to all
objects and all fluids.

2‑9.4.1

Archimedes’ Principle. According to Archimedes’ Principle, the buoyancy of a

submerged body can be established by subtracting the weight of the submerged
body from the weight of the displaced liquid. If the total displacement (the weight
of the displaced liquid) is greater than the weight of the submerged body, the
buoyancy is positive and the body will float or be buoyed upward. If the weight
of the body is equal to that of the displaced liquid, the buoyancy is neutral and the
body will remain suspended in the liquid. If the weight of the submerged body is
greater than that of the displaced liquid, the buoyancy is negative and the body
will sink.
The buoyant force on an object is dependent upon the density of the substance it
is immersed in (weight per unit volume). Fresh water has a density of 62.4 pounds
per cubic foot. Sea water is heavier, having a density of 64.0 pounds per cubic
foot. Thus an object is buoyed up by a greater force in seawater than in fresh water,
making it easier to float in the ocean than in a fresh water lake.
2‑9.4.2

Diver Buoyancy. Lung capacity has a significant effect on buoyancy of a diver.

A diver with full lungs displaces a greater volume of water and, therefore, is
more buoyant than with deflated lungs. Individual differences that may affect
the buoyancy of a diver include bone structure, bone weight, and body fat. These
differences explain why some individuals float easily while others do not.
A diver can vary his buoyancy in several ways. By adding weight to his gear,
he can cause himself to sink. When wearing a variable volume dry suit, he can
increase or decrease the amount of air in his suit, thus changing his displacement

CHAPTER 2 — Underwater Physics

2-13

and thereby his buoyancy. Divers usually seek a condition of neutral to slightly
negative buoyancy. Negative buoyancy gives a diver in a helmet and dress a better
foothold on the bottom. Neutral buoyancy enhances a SCUBA diver’s ability to
swim easily, change depth, and hover.
2-10

GASES IN DIVING

Knowledge of the properties and behavior of gases, especially those used for
breathing, is vitally important to divers.
2-10.1

Atmospheric Air. The most common gas used in diving is atmospheric air, the
composition of which is shown in Table 2-2. Any gases found in concentrations
different than those in Table 2-2 or that are not listed in Table 2-2 are considered
contaminants. Depending on weather and location, many industrial pollutants may
be found in air. Carbon monoxide is the most commonly encountered and is often
present around air compressor engine exhaust. Care must be taken to exclude the
pollut­ants from the diver’s compressed air by appropriate filtering, inlet location,
and compressor maintenance. Water vapor in varying quantities is present in
compressed air and its concentration is important in certain instances.
Table 2‑2. Components of Dry Atmospheric Air.
Concentration
Component

Percent by Volume

Nitrogen

78.084

Oxygen

20.9476

Carbon Dioxide

0.038

Argon

0.0934

Neon

Parts per Million (ppm)

380

18.18

Helium

5.24

Krypton

1.14

Xenon

0.08

Hydrogen

0.5

Methane

2.0

Nitrous Oxide

0.5

For most purposes and computations, diving air may be assumed to be composed
of 79 percent nitrogen and 21 percent oxygen. Besides air, varying mixtures of
oxygen, nitrogen, and helium are commonly used in diving. While these gases are
discussed separately, the gases themselves are almost always used in some mixture.
Air is a naturally occurring mixture of most of them. In certain types of diving
applications, special mixtures may be blended using one or more of the gases with
oxygen.

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U.S. Navy Diving Manual — Volume 1

2-10.2

Oxygen. Oxygen (O2) is the most important of all gases and is one of the most

abundant elements on earth. Fire cannot burn without oxygen and people cannot
survive without oxygen. Atmospheric air contains approximately 21 percent
oxygen, which exists freely in a diatomic state (two atoms paired off to make one
mole­cule). This colorless, odorless, tasteless, and active gas readily combines
with other elements. From the air we breathe, only oxygen is actually used by the
body. The other 79 percent of the air serves to dilute the oxygen. Pure 100 percent
oxygen is often used for breathing in hospitals, aircraft, and hyperbaric medical
treatment facilities. Sometimes 100 percent oxygen is used in shallow diving oper­
ations and certain phases of mixed-gas diving operations. However, breathing pure
oxygen under pressure may induce the serious problems of oxygen toxicity.
2-10.3

2-10.4

Nitrogen. Like oxygen, nitrogen (N2) is diatomic, colorless, odorless, and tasteless,
and is a component of all living organisms. Unlike oxygen, it will not support life
or aid combustion and it does not combine easily with other elements. Nitrogen
in the air is inert in the free state. For diving, nitrogen may be used to dilute
oxygen. Nitrogen is not the only gas that can be used for this purpose and under
some conditions it has severe disadvantages as compared to other gases. Nitrogen
narcosis, a disorder resulting from the anesthetic properties of nitrogen breathed
under pressure, can result in a loss of orientation and judgment by the diver. For
this reason, compressed air, with its high nitrogen content, is not used below a
specified depth in diving operations.
Helium. Helium (He) is a colorless, odorless, and tasteless gas, but it is monatomic

(exists as a single atom in its free state). It is totally inert. Helium is a rare element,
found in air only as a trace element of about 5 parts per million (ppm). Helium
coexists with natural gas in certain wells in the southwestern United States, Canada,
and Russia. These wells provide the world’s supply. When used in diving to dilute
oxygen in the breathing mixture, helium does not cause the same problems associ­
ated with nitrogen narcosis, but it does have unique disadvantages. Among these
is the distortion of speech which takes place in a helium atmosphere. The “Donald
Duck” effect is caused by the acoustic properties of helium and it impairs voice
communications in deep diving. Another negative characteristic of helium is its
high thermal conductivity which can cause rapid loss of body and respiratory heat.
2-10.5

Hydrogen. Hydrogen (H2) is diatomic, colorless, odorless, and tasteless, and is so

active that it is rarely found in a free state on earth. It is, however, the most abundant
element in the visible universe. The sun and stars are almost pure hydrogen. Pure
hydrogen is violently explosive when mixed with air in proportions that include
a presence of more than 5.3 percent oxygen. Hydrogen has been used in diving
(replacing nitrogen for the same reasons as helium) but the hazards have limited
this to little more than experimentation.
2-10.6

Neon. Neon (Ne) is inert, monatomic, colorless, odorless, and tasteless, and is

found in minute quantities in the atmosphere. It is a heavy gas and does not exhibit
the narcotic properties of nitrogen when used as a breathing medium. Because
it does not cause the speech distortion problem associated with helium and has
superior thermal insulating properties, it has been the subject of some experimental
diving research.

CHAPTER 2 — Underwater Physics

2-15

2-10.7

Carbon Dioxide. Carbon dioxide (CO2) is colorless, odorless, and tasteless when

found in small percentages in the air. In greater concentrations it has an acid taste
and odor. Carbon dioxide is a natural by-product of animal and human respiration,
and is formed by the oxidation of carbon in food to produce energy. For divers,
the two major concerns with carbon dioxide are control of the quantity in the
breathing supply and removal of the exhaust after breathing. Carbon dioxide
can cause unconsciousness when breathed at increased partial pressure. In high
concentra­tions the gas can be extremely toxic. In the case of closed and semiclosed
breathing apparatus, the removal of excess carbon dioxide generated by breathing
is essential to safety.
2-10.8

Carbon Monoxide. Carbon monoxide (CO) is a colorless, odorless, tasteless,

and poisonous gas whose presence is difficult to detect. Carbon monoxide is
formed as a product of incomplete fuel combustion, and is most commonly
found in the exhaust of internal combustion engines. A diver’s air supply can be
contaminated by carbon monoxide when the compressor intake is placed too close
to the compressor’s engine exhaust. The exhaust gases are sucked in with the air
and sent on to the diver, with potentially disastrous results. Carbon monoxide
seriously interferes with the blood’s ability to carry the oxygen required for the
body to function normally. The affinity of carbon monoxide for hemoglobin is
approximately 210 times that of oxygen. Carbon monoxide dissociates from
hemoglobin at a much slower rate than oxygen.

2-10.9

Kinetic Theory of Gases. On the surface of the earth the constancy of the

atmosphere’s pressure and compo­sition tend to be accepted without concern. To the
diver, however, the nature of the high pressure or hyperbaric, gaseous environment
assumes great importance. The basic explanation of the behavior of gases under all
variations of temperature and pressure is known as the kinetic theory of gases.

The kinetic theory of gases states: “The kinetic energy of any gas at a given tem­
perature is the same as the kinetic energy of any other gas at the same tempera­ture.”
Consequently, the measurable pressures of all gases resulting from kinetic activity
are affected by the same factors.
The kinetic energy of a gas is related to the speed at which the molecules are
mov­ing and the mass of the gas. Speed is a function of temperature and mass is a
function of gas type. At a given temperature, molecules of heavier gases move at a
slower speed than those of lighter gases, but their combination of mass and speed
results in the same kinetic energy level and impact force. The measured impact
force, or pressure, is representative of the kinetic energy of the gas. This is illus­
trated in Figure 2‑6.

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U.S. Navy Diving Manual — Volume 1

(a)

(b)

(c)

HEAT

Figure 2‑6. Kinetic Energy. The kinetic energy of the molecules inside the container (a) produces a constant
pressure on the internal surfaces. As the container volume is decreased (b), the molecules per unit volume
(density) increase and so does the pressure. As the energy level of the molecules increases from the addition
of thermal energy (heat), so does the pressure (c).

2-11

GAS LAWS

Gases are subject to three closely interrelated factors - temperature, pressure,
and volume. As the kinetic theory of gases points out, a change in one of these
factors must result in some measurable change in the other factors. Further, the
theory indicates that the kinetic behavior of any one gas is the same for all gases or
mixtures of gases. Consequently, basic laws have been established to help predict
the changes that will be reflected in one factor as the conditions of one or both of
the other factors change. A diver needs to know how changing pressure will effect
the air in his suit and lungs as he moves up and down in the water. He must be able
to determine whether an air compressor can deliver an adequate supply of air to a
proposed operating depth. He also needs to be able to interpret the reading on the
pressure gauge of his tanks under varying conditions of temperature and pressure.
The answers to such questions are calculated using a set of rules called the gas
laws. This section explains the gas laws of direct concern to divers.
2-11.1

Boyle’s Law. Boyle’s law states that at constant temperature, the absolute pressure

and the volume of gas are inversely proportional. As pressure increases the gas
volume is reduced; as the pressure is reduced the gas volume increases. Boyle’s
law is important to divers because it relates to change in the volume of a gas
caused by the change in pressure, due to depth, which defines the relationship of
pressure and volume in breathing gas supplies.

The formula for Boyle’s law is: C = P × V
Where:
C
=
P
=
V
=

a constant
absolute pressure
volume

CHAPTER 2 — Underwater Physics

2-17

Boyle’s law can also be expressed as: P1V1 = P2V2
Where:
P1 =
V1 =
P2 =
V2 =

initial pressure
initial volume
final pressure
final volume

When working with Boyle’s law, pressure may be measured in atmospheres abso­
lute. To calculate pressure using atmospheres absolute:
psig + 14.7 psi
Depth fsw + 33 fsw
Pata =
Pata =
or
14.7 psi
33 fsw
Sample Problem 1. An open diving bell with a volume of 24 cubic feet is to be
lowered into the sea from a support craft. No air is supplied to or lost from the bell.
Calculate the volume of the air in the bell at 99 fsw.
1. Rearrange the formula for Boyle’s law to find the final volume (V2):

V2 =

P1V1
P2

2. Calculate the final pressure (P2) at 99 fsw:

99 fsw + 33 fsw
33 fsw
= 4 ata

P2 =

3. Substitute known values to find the final volume:

1ata × 24 ft 3
4 ata
3
= 6 ft

V2 =

The volume of air in the open bell has been compressed to 6 ft3 at 99 fsw.
2-11.2

Charles’/Gay-Lussac’s Law. When working with Boyle’s law, the temperature

of the gas is a constant value. However, temperature significantly affects the
pressure and volume of a gas. Charles’/Gay-Lussac’s law describes the physical
relationships of temperature upon volume and pressure. Charles’/Gay-Lussac’s
law states that at a constant pressure, the volume of a gas is directly proportional
to the change in the absolute temperature. If the pressure is kept constant and
the absolute temperature is doubled, the volume will double. If the temperature
decreases, volume decreases. If volume instead of pressure is kept constant (i.e.,
heating in a rigid container), then the absolute pressure will change in proportion
to the absolute temperature.
The formulas for expressing Charles’/Gay-Lussac’s law are as follows.

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U.S. Navy Diving Manual — Volume 1

For the relationship between volume and temperature:

V1 V2
=
T1 T2
Where:
T1 =
T2 =
V1 =
V2 =

Pressure is constant
initial temperature (absolute)
final temperature (absolute)
initial volume
final volume

And, for the relationship between pressure and temperature:

P1 P2
=
T1 T2
Where:
P1 =
P2 =
T1 =
T2 =

Volume is constant
initial pressure (absolute)
final pressure (absolute)
initial temperature (absolute)
final temperature (absolute)

Sample Problem 1. An open diving bell of 24 cubic feet capacity is lowered into

the ocean to a depth of 99 fsw. The surface temperature is 80°F, and the temperature
at depth is 45°F. From the sample problem illustrating Boyle’s law, we know that
the volume of the gas was compressed to 6 cubic feet when the bell was lowered
to 99 fsw. Apply Charles’/Gay-Lussac’s law to determine the volume when it is
effected by temperature.
1. Convert Fahrenheit temperatures to absolute temperatures (Rankine):

°R = °F + 460
T1 = 80°F + 460
= 540°R
T2 = 45°F + 460
= 505°R
2. Transpose the formula for Charles’/Gay-Lussac’s law to solve for the final volume

(V2):

V2 =

V1T2
T1

3. Substitute known values to solve for the final volume (V2):

V2 =

6 ft3 · 505
540

The volume of the gas at 99 fsw is 5.61 ft3.

CHAPTER 2 — Underwater Physics

2-19

Sample Problem 2. The pressure in a 6-cubic-foot flask is 3000 psig and the

temperature in the flask room is 72° F. A fire in an adjoining space causes the
temperature in the flask room to reach 170° F. What will happen to the pressure in
the flask?

1. Convert gauge pressure to absolute atmospheric pressure unit:

P1 =
=

3000 psig + 14.7 psi
3014.7 psia

2. Convert Fahrenheit temperatures to absolute temperatures (Rankine):

°R =

°F + 460

T1 =

72°F + 460

=
T2 =
=

532°R
170°F + 460
630°R

3. Transpose the formula for Gay-Lussac’s law to solve for the final pressure (P2):

P2 =

P1T2
T1

4. Substitute known values and solve for the final pressure (P2):

3014.7 × 630
532
1, 899, 261
=
532
= 3570.03 psia

P2 =

5. Convert absolute pressure back to gauge pressure:

=

3570.03 psia - 14.7

=

3555.33 psig

The pressure in the flask increased from 3000 psig to 3555.33 psig. Note that
the pressure increased even though the flask’s volume and the volume of the gas
remained the same.
This example also shows what would happen to a SCUBA cylinder that was filled
to capacity and left unattended in the trunk of an automobile or lying in direct
sunlight on a hot day.

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U.S. Navy Diving Manual — Volume 1

2-11.3

The General Gas Law. Boyle, Charles, and Gay-Lussac demonstrated that

temperature, volume, and pres­sure affect a gas in such a way that a change in one
factor must be balanced by corresponding change in one or both of the others.
Boyle’s law describes the rela­tionship between pressure and volume, Charles’/
Gay-Lussac’s law describes the relationship between temperature and volume and
the relationship between temperature and pressure. The general gas law combines
the laws to predict the behavior of a given quantity of gas when any of the factors
change.
P1V1 P2 V2
The formula for expressing the general gas law is: T = T
1
2
Where:
=
P1
V1 =
T1 =
P2
=
V2 =
T2 =

initial pressure (absolute)
initial volume
initial temperature (absolute)
final pressure (absolute)
final volume
final temperature (absolute)

Two simple rules must be kept in mind when working with the general gas law:
n There can be only one unknown value.
n The equation can be simplified if it is known that a value remains unchanged
(such as the volume of an air cylinder) or that the change in one of the variables
is of little consequence. In either case, cancel the value out of both sides of the
equation to simplify the computations.
Sample Problem 1. Your ship has been assigned to salvage a sunken LCM landing

craft located in 130 fsw. An exploratory dive, using SCUBA, is planned to survey
the wreckage. The SCUBA cylinders are charged to 2,250 psig, which raises the
temperature in the tanks to 140 °F. From experience in these waters, you know
that the temperature at the operating depth will be about 40°F. Apply the general
gas law to find what the gauge reading will be when you first reach the bottom.
(Assume no loss of air due to breathing.)

1. Simplify the equation by eliminating the variables that will not change. The volume

of the tank will not change, so V1 and V2 can be eliminated from the formula in this
problem:

P1 P2
=
T1 T2
2. Calculate the initial pressure by converting gauge pressure to absolute pressure:

P1 =
=

2,250 psig + 14.7
2,264.7 psia

CHAPTER 2 — Underwater Physics

2-21

3. Convert Fahrenheit temperatures to Rankine (absolute) temperatures:

Conversion formula: °R = °F + 460
T1 =
=
T2 =
=

140° F + 460
600° R
40° F + 460
500° R

4. Rearrange the formula to solve for the final pressure (P2):

P2 =

P1T2
T1

5. Fill in known values:

2,264.7 psia × 500°R
600°R
= 1887.25 psia

P2 =

6. Convert final pressure (P2) to gauge pressure:

P2 = 1,887.25 psia − 14.7
= 1, 872.55 psia
The gauge reading when you reach bottom will be 1,872.55 psig.
Sample Problem 2. During the survey dive for the operation outlined in Sample

Problem 1, the divers determined that the damage will require a simple patch.
The Diving Supervisor elects to use surface-supplied KM-37 equipment. The
compressor discharge capacity is 60 cubic feet per minute, and the air temperature
on the deck of the ship is 80°F.

Apply the general gas law to determine whether the compressor can deliver the
proper volume of air to both the working diver and the standby diver at the oper­
ating depth and temperature.
1. Calculate the absolute pressure at depth (P2):

130 fsw + 33 fsw
33 fsw
= 4.93 ata

P2 =

2. Convert Fahrenheit temperatures to Rankine (absolute) temperatures:

Conversion formula:

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U.S. Navy Diving Manual — Volume 1

°R =

°F + 460

T1 =

80°F + 460

=

540°R

T2 =

40°F + 460

=

500°R

3. Rearrange the general gas law formula to solve for the volume of air at depth (V2):

V2 =

P1V1T2
P2 T1

4. Substitute known values and solve:

1 ata × 60 cfm × 500°R
4.93 ata × 540°R
= 11.26 acfm at bottom conditions

V2 =

Based upon an actual volume (displacement) flow requirement of 1.4 acfm for a
deep-sea diver, the compressor capacity is sufficient to support the working and
standby divers at 130 fsw.
Sample Problem 3. Find the actual cubic feet of air contained in a .399-cubic foot

internal volume cylinder pressurized to 3,000 psi.

1. Simplify the equation by eliminating the variables that will not change. The

temperature of the tank will not change so T1 and T2 can be eliminated from the
formula in this problem:

P1V1 = P2V2
2. Rearrange the formula to solve for the initial volume:

V1 =

P2 V2
P1

Where:
P1 =

14.7 psi

P2 =

3,000 psi + 14.7 psi

V2 =

.399 ft3

3. Fill in the known values and solve for V1:

V1 =

3014.7 psia · .399 ft
14.7 psi

= 81.82 scf

CHAPTER 2 — Underwater Physics

2-23

2-12

GAS MIXTURES

If a diver used only one gas for all underwater work, at all depths, then the general
gas law would suffice for most of his necessary calculations. However, to accom­
modate use of a single gas, oxygen would have to be chosen because it is the only
one that provides life support. But 100 percent oxygen can be dangerous to a diver
as depth and breathing time increase. Divers usually breathe gases in a mixture,
either air (21 percent oxygen, 78 percent nitrogen, 1 percent other gases) or oxygen
with one of the inert gases serving as a diluent for the oxygen. The human body has
a wide range of physiological reactions to various gases under different conditions
of pressure and for this reason another gas law is required to predict the effects of
breathing those gases while under pressure.
2-12.1

Dalton’s Law. Dalton’s law states: “The total pressure exerted by a mixture of

gases is equal to the sum of the pressures of each of the different gases making up
the mixture, with each gas acting as if it alone was present and occupied the total
volume.”

In a gas mixture, the portion of the total pressure contributed by a single gas is
called the partial pressure (pp) of that gas. An easily understood example is that
of a container at atmospheric pressure (14.7 psi). If the container were filled with
oxygen alone, the partial pressure of the oxygen would be one atmosphere. If
the same container at 1 atm were filled with dry air, the partial pressures of all
the constituent gases would contribute to the total partial pressure, as shown in
Table 2‑3.
If the same container was filled with air to 2,000 psi (137 ata), the partial pressures of
the various components would reflect the increased pressure in the same proportion
as their percentage of the gas, as illustrated in Table 2‑4.
Table 2‑3. Partial Pressure at 1 ata.
Gas

Percent of Component

Atmospheres Partial Pressure

N2

78.08

0.7808

O2

20.95

0.2095

CO2

.03

0.0003

Other

.94

0.0094

Total

100.00

1.0000

Table 2‑4. Partial Pressure at 137 ata.

2-24

Gas

Percent of Component

Atmospheres Partial Pressure

N2

78.08

106.97

O2

20.95

28.70

U.S. Navy Diving Manual — Volume 1

Gas

Percent of Component

Atmospheres Partial Pressure

CO2

.03

0.04

Other

.94

1.29

Total

100.00

137.00

The formula for expressing Dalton’s law is:

PTotal = pp A + pp B + pp C + …
Where: A, B, and C are gases and

pp A =

PTotal × %VolA
1.00

A simple method to solve problems of Dalton’s law is to arrange the variables in a
“T” formula. To use the T formula there can only be one unknown value; Multiply
the known values if the unknown value is partial pressure or divide if the unknown
is ata or volume of gas.
The T formula is illustrated as:
partial pressure
ata

% of Gas (in decimal form)

Sample Problem 1. Use the T formula to calculate the partial pressure of oxygen
given in air at 190 fsw.
1. Convert feet of salt water to ata:

190 fsw + 33
= 6.75 ata
33
2. Convert the percentage of oxygen in air to decimal:

21%
100

= .21 pp02

3. Substitute known values:

pp
6.75 .21
2. Multiply the pressure by the volume to solve for pp:

6.75 x .21 = 1.41 ppO2
Sample Problem 2. In diving we have the option of using gas mixtures other than

air. However, we must control the level of oxygen in those mixtures to avoid

CHAPTER 2 — Underwater Physics

2-25

exposing divers to harmful side effects of increased ppO2. Use Dalton’s law to
determine the maximum O2 % allowed when diving to 300 fsw given a limit of
1.3ppO2.
1. Convert fsw to ata:

ata =

300 + 33
33

= 10.09

= 10.09 ata
2. Substitute known values:

1.3 ppO2
10.09 ata

% of Gas

3. Divide pp by ata to solve for percent of gas:

1.3 ppO2
= 0.1288 % of Gas
10.09
4. Convert from decimal to percentage:

0.1288 x 100 = 12.88 max % O2 allowed
Sample Problem 3. Determine the maximum safe depth of an 11% mix of HeO2
given a 1.3ppO2 limit:
1. Convert 11% HEO2 to a decimal:

11%
100

= 0.11

2. Substitute known values:

1.3 ppO2
ata
0.11
3. Divide pp by percentage of gas to solve ata:

1.3 ppO2
= 11.81 ata
0.11
4. Convert from ata to fsw:

(11.81 x 33) - 33 = 356.73 fsw
Round down to a max safe depth of 356 fsw

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U.S. Navy Diving Manual — Volume 1

2‑12.1.1

Calculating Surface Equivalent Value (SEV). Dalton’s law explains the potential

consequences of exposure to increased partial pressures of various gasses. For
example, if the surface air were contaminated with 2 percent (0.02 ata) CO2, a
level that could be readily accommodated by a person on the surface, the partial
pressure at an increased depth could be dangerously high. The correlation of a gas
inspired at depth to its equivalent physiological effect if the same concentration
were breathed on the surface is referred to as surface equivalent value (SEV). The
formula for calculating SEV is:
SEV =

Example:

pp
1 ata

When breathing air on the surface 21% (0.21 ppO2) oxygen is being inspired. At

33 fsw (2ata) the pressure doubles to 0.42ppO2, the percentage by volume stays
the same but the number of molecules inspired increased. Move the decimal point
2 places to the right to get a surface equivalent of 42% oxygen. It makes sense that
we are breathing twice the molecules of O2 at 33 fsw since we are at twice the
pressure.
Sample problem 1. Your recompression chamber is on ascent from treatment depth

at 1fpm and is at a depth of 127 fsw. The chamber CO2 monitor reads .23% CO2.
The limit for chamber CO2 levels is 1.5 SEV. Is the chamber within safe limits for
CO2?

1. Calculate ppCO2 at 127 fsw.

SEV = ATA x % of gas (decimal form)
SEV = 4.84 x .023 CO2
= 1.11 SEV
SEV = 1.11 which is lower than 1.5. The chamber is within acceptable limits.
Sample problem 2. What is the maximum permissible CO2 reading on the monitor

for the same scenario in problem 1?

CHAPTER 2 — Underwater Physics

2-27

1. The formula for calculating the surface equivalent value is:

% CO2 = ppCO2
ata
= 1.5 SEV
= .30 CO2
4.84
The maximum monitor reading on the chamber can be .30% and still be within
the limit of 1.5 sev CO2 at 127 fsw.
2‑12.1.2

Expressing Small Quantities of Pressure. Partial pressures of less than 0.1
atmosphere are usually expressed in millimeters of mercury (mmHg). One
atmosphere is equal to 760 mmHg. The formula used to convert pp to mmHg is:
mmHg = pp x 760mmHg
Sample problem 1. Convert the result in sample problem 2 to mmHg.
1. Convert % of gas to

pp =

0.30 CO2
= 0.0030 ppCO2
100

2. 0.0030 ppCO2 x 760mmHg = 2.28mmHg
2.12.1.3

Expressing Small Quantities of Volume. Volume of gas is typically expressed as
a percentage. Where a gas constituent is less than 0.01 percent its volume may be
expressed in parts per million (ppm). 1ppm = 1/1000000, therefore 1ppm = 0.0001
percent. The formula to convert a percentage to ppm is:
ppm = Percent of gas X 10,000.
Conversely, percent of gas = ppm / 10,000

2-12.2

Gas Diffusion. Another physical effect of partial pressures and kinetic activity is

that of gas diffu­sion. Gas diffusion is the process of intermingling or mixing of gas
molecules. If two gases are placed together in a container, they will eventually mix
completely even though one gas may be heavier. The mixing occurs as a result of
constant molecular motion.
An individual gas will move through a permeable membrane (a solid that permits
molecular transmission) depending upon the partial pressure of the gas on each side
of the membrane. If the partial pressure is higher on one side, the gas mole­cules
will diffuse through the membrane from the higher to the lower partial pressure
side until the partial pressure on sides of the membrane are equal. Mole­cules are

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U.S. Navy Diving Manual — Volume 1

actually passing through the membrane at all times in both directions due to kinetic
activity, but more will move from the side of higher concentration to the side of
lower concentration.
Body tissues are permeable membranes. The rate of gas diffusion, which is related
to the difference in partial pressures, is an important consideration in determining
the uptake and elimination of gases in calculating decompression tables.
2-12.3

Humidity. Humidity is the amount of water vapor in gaseous atmospheres. Like
other gases, water vapor behaves in accordance with the gas laws. However,
unlike other gases encountered in diving, water vapor condenses to its liquid state
at temperatures normally encountered by man.

Humidity is related to the vapor pressure of water, and the maximum partial pres­
sure of water vapor in the gas is governed entirely by the temperature of the gas.
As the gas temperature increases, more molecules of water can be maintained in
the gas until a new equilibrium condition and higher maximum partial pressure are
established. As a gas cools, water vapor in the gas condenses until a lower partial
pressure condition exists regardless of the total pressure of the gas. The tempera­
ture at which a gas is saturated with water vapor is called the dewpoint.
In proper concentrations, water vapor in a diver’s breathing gas can be beneficial to
the diver. Water vapor moistens body tissues, thus keeping the diver comfort­able.
As a condensing liquid, however, water vapor can freeze and block air passageways
in hoses and equipment, fog a diver’s faceplate, and corrode his equipment.
2-12.4

2-12.5

Gases in Liquids. When a gas comes in contact with a liquid, a portion of the gas

molecules enters into solution with the liquid. The gas is said to be dissolved in
the liquid. Solubility is vitally important because significant amounts of gases are
dissolved in body tissues at the pressures encountered in diving.
Solubility. Some gases are more soluble (capable of being dissolved) than others,

and some liquids and substances are better solvents (capable of dissolving another
substance) than others. For example, nitrogen is five times more soluble in fat than
it is in water.

Apart from the individual characteristics of the various gases and liquids, tempera­
ture and pressure greatly affect the quantity of gas that will be absorbed. Because a
diver is always operating under unusual conditions of pressure, understanding this
factor is particularly important.
2-12.6

Henry’s Law. Henry’s law states: “The amount of any given gas that will dissolve
in a liquid at a given temperature is directly proportional to the partial pressure of
that gas.” Because a large percentage of the human body is water, the law simply
states that as one dives deeper and deeper, more gas will dissolve in the body
tissues and that upon ascent, the dissolved gas must be released.

CHAPTER 2 — Underwater Physics

2-29

2‑12.6.1

Gas Tension. When a gas-free liquid is first exposed to a gas, quantities of gas

molecules rush to enter the solution, pushed along by the partial pressure of the
gas. As the mole­cules enter the liquid, they add to a state of gas tension. Gas
tension is a way of identifying the partial pressure of that gas in the liquid.

The difference between the gas tension and the partial pressure of the gas outside
the liquid is called the pressure gradient. The pressure gradient indicates the rate at
which the gas enters or leaves the solution.
2‑12.6.2

Gas Absorption. At sea level, the body tissues are equilibrated with dissolved
nitrogen at a partial pressure equal to the partial pressure of nitrogen in the lungs.
Upon exposure to altitude or increased pressure in diving, the partial pressure of
nitrogen in the lungs changes and tissues either lose or gain nitrogen to reach a
new equilibrium with the nitrogen pressure in the lungs. Taking up nitrogen in
tissues is called absorp­tion or uptake. Giving up nitrogen from tissues is termed
elimination or offgassing. In air diving, nitrogen absorption occurs when a diver
is exposed to an increased nitrogen partial pressure. As pressure decreases, the
nitrogen is elimi­nated. This is true for any inert gas breathed.

Absorption consists of several phases, including transfer of inert gas from the lungs
to the blood and then from the blood to the various tissues as it flows through the
body. The gradient for gas transfer is the partial pressure difference of the gas
between the lungs and blood and between the blood and the tissues.
The volume of blood flowing through tissues is small compared to the mass of the
tissue, but over a period of time the gas delivered to the tissue causes it to become
equilibrated with the gas carried in the blood. As the number of gas molecules
in the liquid increases, the tension increases until it reaches a value equal to the
partial pressure. When the tension equals the partial pressure, the liquid is satu­rated
with the gas and the pressure gradient is zero. Unless the temperature or pressure
changes, the only molecules of gas to enter or leave the liquid are those which may,
in random fashion, change places without altering the balance.
The rate of equilibration with the blood gas depends upon the volume of blood
flow and the respective capacities of blood and tissues to absorb dissolved gas. For
example, fatty tissues hold significantly more gas than watery tissues and will thus
take longer to absorb or eliminate excess inert gas.
2‑12.6.3

Gas Solubility. The solubility of gases is affected by temperature - the lower the

temperature, the higher the solubility. As the temperature of a solution increases,
some of the dissolved gas leaves the solution. The bubbles rising in a pan of water
being heated (long before it boils) are bubbles of dissolved gas coming out of
solution.

The gases in a diver’s breathing mixture are dissolved into his body in proportion
to the partial pressure of each gas in the mixture. Because of the varied solubility
of different gases, the quantity of a particular gas that becomes dissolved is also
governed by the length of time the diver is breathing the gas at the increased pres­
sure. If the diver breathes the gas long enough, his body will become saturated.
2-30

U.S. Navy Diving Manual — Volume 1

The dissolved gas in a diver’s body, regardless of quantity, depth, or pressure,
remains in solution as long as the pressure is maintained. However, as the
diver ascends, more and more of the dissolved gas comes out of solution. If his
ascent rate is controlled (i.e., through the use of the decompression tables), the
dissolved gas is carried to the lungs and exhaled before it accumulates to form
significant bubbles in the tissues. If, on the other hand, he ascends suddenly and
the pressure is reduced at a rate higher than the body can accommodate, bubbles
may form, disrupt body tissues and systems, and produce decompression sickness.
Table 2‑5. Symbols and Values.
Symbol
°F

Degrees Fahrenheit

°C

Degrees Celsius

°R

Degrees Rankine

A

Area

C

Circumference

D

Depth of Water

H

Height

L

Length

P

Pressure

r

Radius

T

Temperature

t

Time

V

Volume

W

Width

Dia

Diameter

Dia2

Diameter Squared

Dia3

Diameter Cubed

�

3.1416

ata

Atmospheres Absolute

pp

Partial Pressure

psi

Pounds per Square Inch

psig

Pounds per Square Inch Gauge

psia

Pounds per Square Inch Absolute

fsw

Feet of Sea Water

fpm

Feet per Minute

scf

Standard Cubic Feet

BTU

British Thermal Unit

cm3

Cubic Centimeter

kw hr
mb

CHAPTER 2 — Underwater Physics

Value

Kilowatt Hour
Millibars

2-31

Table 2‑6. Buoyancy (In Pounds).
Fresh Water

(V cu ft x 62.4) - Weight of Unit

Salt Water

(V cu ft x 64) - Weight of Unit

Table 2‑7. Formulas for Area.
Square or Rectangle

A=LxW

Circle

A = 0.7854 x Dia2
or
A = πr2

Table 2‑8. Formulas for Volumes.
Compartment

V=LxWxH

Sphere

= π x 4/3 x r 3
= 0.5236 x Dia3

Cylinder

V=πxr2xL
= π x 1/4 x Dia2 x L
= 0.7854 x Dia2 x L

Table 2‑9. Formulas for Partial Pressure/Equivalent Air Depth.
Partial Pressure Measured in psi

 %V 
pp = (D + 33 fsw) × 0.445 psi × 

 100% 

Partial Pressure Measured in ata

pp =

Partial Pressure Measured in fsw

pp = (D + 33 fsw) ×

T formula for Measuring Partial Pressure

pp
ata  %

Equivalent Air Depth for N2O2 Diving Measured in fsw

Equivalent Air Depth for N2O2 Diving Measured in meters

2-32

D + 33 fsw
%V
×
33 fsw
100%
%V
100%

[(1.0 - O .79%)(D + 33) ] - 33

EAD =

EAD =

2

%)(M + 10)
[ (1.0 − O .79
] − 10
2

U.S. Navy Diving Manual — Volume 1

Table 2‑10. Pressure Equivalents.
Columns of Mercury
at 0°C
Atmospheres

Bars

10 Newton Pounds
Per Square Per Square
Meters
Centimeter Inch

Columns of Water*
at 15°C

Inches

Meters

Inches

Feet
(FW)

Feet
(FSW)

1

1.01325

1.03323

14.696

0.76

29.9212

10.337

406.966

33.9139

33.066

0.986923

1

1.01972

14.5038

0.750062

29.5299

10.2018

401.645

33.4704

32.6336

0.967841

0.980665

1

14.2234

0.735559

28.959

10.0045

393.879

32.8232

32.0026

0.068046

0.068947

0.070307

1.31579

1.33322

1.35951

0.0334211

0.0338639

0.0345316

0.491157

0.0254

1

0.345473

13.6013

1.13344

1.1051

0.09674

0.09798

0.099955

1.42169

0.073523

2.89458

1

39.37

3.28083

3.19881

0.002456

0.002489

0.002538

0.03609

0.001867

0.073523

0.02540

1

0.08333

0.08125

0.029487

0.029877

0.030466

0.43333

0.02241

0.882271

0.304801

12

1

0.975

0.030242

0.030643

0.031247

0.44444

0.022984

0.904884

0.312616

12.3077

1.02564

1

1

0.0517147

19.33369

1

2.03601
39.37

lbs/ft3;

0.703386

27.6923

13.6013

535.482

2.30769

2.25

44.6235

43.5079

lbs/ft3.

1. Fresh Water (FW) = 62.4
Salt Water (fsw) = 64.0
2. The SI unit for pressure is Kilopascal (KPA)—1KG/CM2 = 98.0665 KPA and by definition 1 BAR = 100.00 KPA @ 4ºC.
3. In the metric system, 10 MSW is defined as 1 BAR. Note that pressure conversion from MSW to FSW is different than length
conversion; i.e., 10 MSW = 32.6336 FSW and 10 M = 32.8083 feet.

Table 2‑11. Volume and Capacity Equivalents.
Cubic
Centimeters

Cubic
Inches

Cubic
Feet

Cubic
Yards
10-5

Milliliters

Liters

10-6

1.00000

1x

10-3

Pint

Quart
10-3

Gallon
10-3

2.6417x 10-4

1

.061023

3.531 x

16.3872

1

5.787 x 10-4

2.1434 x 10-5

16.3867

0.0163867

0.034632

0.017316

4.329 x 10-3

28317

1728

1

0.037037

28316.2

28.3162

59.8442

29.9221

7.48052

764559

46656

27

1

764538

764.538

1615.79

10-5

1.00003

0.0610251

3.5315 x

1000.03

61.0251

0.0353154

473.179

28.875

946.359
3785.43

57.75
231

1.3097 x

1.0567 x

807.896
10-3

2.6418 x 10-4

0.001

2.1134 x

1.308 x 10-3

1000

1

2.11342

1.05671

0.264178

0.0167101

6.1889 x 10-4

473.166

0.473166

1

0.5

0.125

0.0334201

10-3

946.332

0.946332

2

1

0.25

3785.33

3.78533

8

4

1

CHAPTER 2 — Underwater Physics

1.2378 x
49511 x

10-3

1.0567 x

201.974
10-3

1

0.133681

1.308 x

10-6

2.113 x

2-33

Table 2‑12. Length Equivalents.
Centimeters

Inches

Feet

Yards

Meters

Fathom

Kilometers

Miles

Int. Nautical
Miles

1

0.3937

0.032808

0.010936

0.01

5.468 x 10-3

0.00001

6.2137 x 10-5

5.3659 x 10-6

2.54001

1

0.08333

0.027778

0.025400

0.013889

2.540 x 10-5

1.5783 x 10-5

1.3706 x 10-5

10-4

1.6447 x 10-4

10-4

30.4801

12

1

0.33333

0.304801

0.166665

3.0480 x

1.8939 x

91.4403

36

3

1

0.914403

0.5

9.144 x 10-4

5.6818 x 10-4

4.9341 x 10-4

100

39.37

3.28083

1.09361

1

0.5468

0.001

6.2137 x 10-4

5.3959 x 10-4

182.882

72

6

2

1.82882

1

1.8288 x 10-3

1.1364 x 10-3

9.8682 x 10-4

100000

39370

3280.83

1093.61

1000

546.8

1

0.62137

0.539593

160935

63360

5280

1760

1609.35

80

1.60935

1

0.868393

185325

72962.4

6080.4

2026.73

1852

1013.36

1.85325

1.15155

1

Table 2‑13. Area Equivalents.
Square
Meters

Square
Centimeters

Square
Inches

Square
Feet

1

10000

1550

10.7639

Square
Yards

2.471 x 10-4

1.19599
10-3

10-4

3.861 x 10-11

1

0.155

1.0764 x

6.4516 x 10-4

6.45163

1

6.944 x 10-3

7.716 x 10-4

1.594 x 10-7

2.491 x 10-10

0.092903

929.034

144

1

0.11111

2.2957 x 10-5

3.578 x 10-8

0.836131

8361.31

9

1

2.0661 x 10-4

3.2283 x 10-7

43560

4840

1

1.5625 x 10-3

2.7878 x 107

3.0976 x 106

640

1

1296

4046.87

4.0469 x

2.59 x 106

2.59 x 1010

6.2726 x

106

4.0145 x 109

2.471 x

3.861 x 10-7

10-8

0.0001

107

1.196 x

Square
Miles

Acres

Table 2‑14. Velocity Equivalents.
Centimeters
Per Second

Meters
Per Second

Meters
Per Minute

Kilometers
Per Hour

Feet
Per Second

Feet
Per Minute

Miles
Per Hour

Knots

1

0.01

0.6

0.036

0.0328083

1.9685

0.0223639

0.0194673

100

1

60

3.6

3.28083

196.85

2.23693

1.9473

1.66667

0.016667

1

0.06

0.0546806

3.28083

0.0372822

0.0324455

27.778

0.27778

16.667

1

0.911343

54.6806

0.62137

0.540758

30.4801

0.304801

18.288

1.09728

1

60

0.681818

0.593365

0.5080

5.080 x 10-3

0.304801

0.018288

0.016667

1

0.0113636

9.8894 x 10-3

44.7041

0.447041

26.8225

1.60935

1.4667

88

1

0.870268

51.3682

0.513682

30.8209

1.84926

1.6853

101.118

1.14907

1

2-34

U.S. Navy Diving Manual — Volume 1

Table 2‑15. Mass Equivalents.
Kilograms

Grams

Grains

Ounces

Pounds

Tons (short)

Tons (long)

10-3

10-4

9.842 x

Tons (metric)
0.001

1

1000

15432.4

35.274

2.20462

1.1023 x

0.001

1

15432.4

0.035274

2.2046 x 10-3

1.1023 x 10-6

9.842 x 10-7

0.000001

6.4799 x 10-5

0.6047989

1

2.2857 x 10-3

1.4286 x 10-4

7.1429 x 10-8

6.3776 x 10-8

6.4799 x 10-8

10-5

2.835 x 10-5

0.0283495

28.3495

437.5

1

0.0625

3.125 x

0.453592

453.592

7000

16

1

0.0005

4.4543 x 10-4

4.5359 x 10-4

907.185

907185

1.4 x 107

32000

2000

1

0.892857

0.907185

1016.05

1.016 x 106

1.568 x 107

35840

2240

1.12

1

1.01605

1000

106

35274

2204.62

1.10231

984206

1

1.5432 x

107

2.790 x

10-5

Table 2‑16. Energy or Work Equivalents.
International
Kilowatt
Hours

Kilo Calories

Ergs

1

107

0.737682

2.778 x

10-7

1

7.3768 x 10-8

2.778 x 10-14

3.726 x 10-14

2.389 x 10-11

9.4799 x 10-11

1

3.766 x 10-7

5.0505 x 10-7

3.238 x 10-4

1.285 x 10-3

1

1.34124

860

3412.76

1.3556 x 107

1.3566
3.6 x

106

2.684 x

Foot Pounds

Horse Power
Hours

International
Joules

106

3.6 x

1013

2.684 x

1013

2.6557 x
1.98 x

106

106

10-7

3.7257

10-7

2.3889 x

BTUs
10-4

9.4799 x 10-4

0.745578

1

641.197

2544.48

4186.04

4.186 x 1010

3087.97

1.163 x 10-3

1.596 x 10-3

1

3.96832

1054.87

1.0549 x 1010

778.155

2.930 x 10-4

3.93 x 10-4

0.251996

1

Kg-M
Second

Foot lbs.
Per Second

IT Calories
Per Second

BTUs
Per Second

Table 2‑17. Power Equivalents.
Horse
Power

International
Kilowatts

International
Joules/
Second

1

0.745578

745.578

76.0404

550

178.11

0.7068

1.34124

1

1000

101.989

737.683

238.889

0.947989

1.3412 x 10-3

0.001

1

0.101988

0.737682

0.238889

9.4799 x 10-4

9.80503

1

7.233

2.34231

9.2951 x 10-3

10-3

0.0131509

9.805 x

1.8182 x 10-3

1.3556 x 10-3

1.3556

0.138255

1

0.323837

1.2851 x 10-3

5.6145 x 10-3

4.1861 x 10-3

4.18605

0.426929

3.08797

1

3.9683 x 10-3

1.41483

1.05486

1054.86

107.584

778.155

251.995

1

CHAPTER 2 — Underwater Physics

2-35

Table 2‑18. Temperature Equivalents.
°C = (°F − 32) ×

Conversion Formulas:

5
9

9
°F = ( × °C) + 32
5

°C

°F

°C

°F

°C

°F

°C

°F

°C

°F

°C

°F

°C

°F

-100
-98
-96
-94
-92

-148.0
-144.4
-140.8
-137.2
-133.6

-60
-58
-56
-54
-52

-76.0
-72.4
-68.8
-65.2
-61.6

-20
-18
-16
-14
-12

-4.0
-0.4
3.2
6.8
10.4

20
22
24
26
28

68.0
71.6
75.2
78.8
82.4

60
62
64
66
68

140.0
143.6
147.2
150.8
154.4

100
102
104
106
108

212.0
215.6
219.2
222.8
226.4

140
142
144
146
148

284.0
287.6
291.2
294.8
298.4

-90
-88
-86
-84
-82

-130.0
-126.4
-122.8
-119.2
-115.6

-50
-48
-46
-44
-42

-58.0
-54.4
-50.8
-47.2
-43.6

-10
-8
-6
-4
-2

14.0
17.6
21.2
24.8
28.4

30
32
34
36
38

86.0
89.6
93.2
96.8
100.4

70
72
74
76
78

158.0
161.6
165.2
168.8
172.4

110
112
114
116
118

230.0
233.6
237.2
240.8
244.4

150
152
154
156
158

302.0
305.6
309.2
312.8
316.4

-80
-78
-76
-74
-72

-112.0
-108.4
-104.8
-101.2
-97.6

-40
-38
-36
-34
-32

-40.0
-36.4
-32.8
-29.2
-25.6

0
2
4
6
8

32
35.6
39.2
42.8
46.4

40
42
44
46
48

104.0
107.6
111.2
114.8
118.4

80
82
84
86
88

176.0
179.6
183.2
186.8
190.4

120
122
124
126
128

248.0
251.6
255.2
258.8
262.4

160
162
164
166
168

320.0
323.6
327.2
330.8
334.4

-70
-68
-66
-64
-62

-94.0
-90.4
-86.8
-83.2
-79.6

-30
-28
-26
-24
-22

-22.0
-18.4
-14.8
-11.2
-7.6

10
12
14
16
18

50.0
53.6
57.2
60.8
64.4

50
52
54
56
58

122.0
125.6
129.2
132.8
136.4

90
92
94
96
98

194.0
197.6
201.2
204.8
208.4

130
132
134
136
138

266.0
269.6
273.2
276.8
280.4

170
172
174
176
178

338.0
341.6
345.2
348.8
352.4

Table 2-19. Atmospheric Pressure at Altitude.
Atmospheric Pressure

2-36

Altitude
in Feet

Atmospheres
absolute

Millimeters
of Mercury

Pounds per
sq. in. absolute

Millibars

Kilopascals

500

0.982

746.4

14.43

995.1

99.51

1000

0.964

732.9

14.17

977.2

97.72

1500

0.947

719.7

13.92

959.5

95.95

2000

0.930

706.7

13.66

942.1

94.21

2500

0.913

693.8

13.42

925.0

92.50

3000

0.896

681.1

13.17

908.1

90.81

3500

0.880

668.7

12.93

891.5

89.15

4000

0.864

656.4

12.69

875.1

87.51

4500

0.848

644.3

12.46

859.0

85.90

5000

0.832

632.4

12.23

843.1

84.31

5500

0.817

620.6

12.00

827.4

82.74

6000

0.801

609.0

11.78

812.0

81.20

6500

0.786

597.7

11.56

796.8

79.68

7000

0.772

586.4

11.34

781.9

78.19

7500

0.757

575.4

11.13

767.1

76.71

8000

0.743

564.5

10.92

752.6

75.26

8500

0.729

553.8

10.71

738.3

73.83

9000

0.715

543.3

10.50

724.3

72.43

9500

0.701

532.9

10.30

710.4

71.04

10000

0.688

522.7

10.11

696.8

69.68

U.S. Navy Diving Manual — Volume 1

Depth, Pressure, Atmosphere
300

10

290
280
270

9

260
250
240

8

230
220
210

7

200
180

DEPTH
FSW

170

6

160
150
140

5

ATMOSPHERE
ABSOLUTE

190

130
120
100

4

90
80
70

3

60
50
40

2

30
20
10

1

0
0

10

20

30

40

50

60

70

80

90

100

110

120

130

PRESSURE PSIG

Figure 2‑7. Depth, Pressure, Atmosphere Graph.

CHAPTER 2 — Underwater Physics

2-37

PAGE LEFT BLANK INTENTIONALLY

2-38

U.S. Navy Diving Manual — Volume 1

CHAPTER 3

Underwater Physiology and Diving
Disorders
3-1

INTRODUCTION
3-1.1

Purpose. This chapter provides basic information on the changes in human anatomy

and physiology that occur while working in the underwater environment. It also
discusses the diving disorders that result when these anatomical or physiological
changes exceed the limits of adaptation.

3-1.2

Scope. Anatomy is the study of the structure of the organs of the body. Physiology

is the study of the processes and functions of the body. This chapter explains
the basic anatomical and physiological changes that occur when diver enters the
water and is subject to increased ambient pressure. A diver’s knowledge of these
changes is as important as his knowledge of diving gear and procedures. When the
changes in normal anatomy or physiology exceed the limits of adaptation, one or
more patho­logical states may emerge. These pathological states are called diving
disorders and are also discussed in this chapter. Safe diving is only possible when
the diver fully understands the fundamental processes at work on the human body
in the underwater environment.
3-1.3

General. A body at work requires coordinated functioning of all organs and systems.
The heart pumps blood to all parts of the body, the tissue fluids exchange dissolved
materials with the blood, and the lungs keep the blood supplied with oxygen and
cleared of excess carbon dioxide. Most of these processes are controlled directly by
the brain, nervous system, and various glands. The individual is generally unaware
that these functions are taking place.

As efficient as it is, the human body lacks effective ways of compensating for
many of the effects of increased pressure at depth and can do little to keep its
internal environment from being upset. Such external effects set definite limits on
what a diver can do and, if not understood, can give rise to serious accidents.
3-2

THE NERVOUS SYSTEM

The nervous system coordinates all body functions and activities. The nervous
system comprises the brain, spinal cord, and a complex network of nerves that
course through the body. The brain and spinal cord are collectively referred to as
the central nervous system (CNS). Nerves originating in the brain and spinal cord
and traveling to peripheral parts of the body form the peripheral nervous system
(PNS). The peripheral nervous system consists of the cranial nerves, the spinal
nerves, and the sympathetic nervous system. The peripheral nervous system is
involved in regulating cardiovascular, respiratory, and other automatic body func­
tions. These nerve trunks also transmit nerve impulses associated with sight,

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3-1

hearing, balance, taste, touch, pain, and temperature between peripheral sensors
and the spinal cord and brain.
3-3

THE CIRCULATORY SYSTEM

The circulatory system consists of the heart, arteries, veins, and capillaries. The
circulatory system carries oxygen, nutrients, and hormones to every cell of the
body, and carries away carbon dioxide, waste chemicals, and heat. Blood circulates
through a closed system of tubes that includes the lung and tissue capillaries, heart,
arteries, and veins.
3-3.1

Anatomy. Every part of the body is completely interwoven with intricate networks

of extremely small blood vessels called capillaries. The very large surface areas
required for ample diffusion of gases in the lungs and tissues are provided by the
thin walls of the capillaries. In the lungs, capillaries surround the tiny air sacs
(alveoli) so that the blood they carry can exchange gases with air.
3‑3.1.1

The Heart. The heart (Figure 3‑1) is the muscular pump that propels the blood

throughout the system. It is about the size of a closed fist, hollow, and made up
almost entirely of muscle tissue that forms its walls and provides the pumping
action. The heart is located in the front and center of the chest cavity between the
lungs, directly behind the breastbone (sternum).
The interior of the heart is divided lengthwise into halves, separated by a wall of
tissue called a septum. The two halves have no direct connection to each other.
Each half is divided into an upper chamber (the atrium), which receives blood from
the veins of its circuit and a lower chamber (the ventricle) which takes blood from
the atrium and pumps it away via the main artery. Because the ventricles do most
of the pumping, they have the thickest, most muscular walls. The arteries carry
blood from the heart to the capillaries; the veins return blood from the capil­laries
to the heart. Arteries and veins branch and rebranch many times, very much like
a tree. Trunks near the heart are approximately the diameter of a human thumb,
while the smallest arterial and venous twigs are microscopic. Capillaries provide
the connections that let blood flow from the smallest branch arteries (arte­rioles)
into the smallest veins (venules).
3‑3.1.2

The Pulmonary and Systemic Circuits. The circulatory system consists of two

circuits with the same blood flowing through the body. The pulmonary circuit
serves the lung capillaries; the systemic circuit serves the tissue capillaries. Each
circuit has its own arteries and veins and its own half of the heart as a pump.
In complete circulation, blood first passes through one circuit and then the other,
going through the heart twice in each complete circuit.

3-3.2

Circulatory Function. Blood follows a continuous circuit through the human

body. Blood leaving a muscle or organ capillary has lost most of its oxygen and
is loaded with carbon dioxide. The blood flows through the body’s veins to the
main veins in the upper chest (the superior and inferior vena cava). The superior
vena cava receives blood from the upper half of the body; the inferior vena cava
receives blood from areas of the body below the diaphragm. The blood flows

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Head and Upper
Extremities
Brachiocephalic Trunk
Superior Vena Cava

Left Common Carotid Artery
Left Subclavian Artery
Arch of Aorta

Right Pulmonary Artery

Left Pulmonary Artery

Right
Lung

Left
Lung
Left Pulmonary Veins

Right Pulmonary Veins

Left Atrium
Right Atrium

Left Ventricle

Right Ventricle
Inferior Vena Cava

Thoracic Aorta

Trunk and Lower
Extremities

Figure 3-1. The Heart’s Components and Blood Flow.

through the main veins into the right atrium and then through the tricuspid valve
into the right ventricle.
The next heart contraction forces the blood through the pulmonic valve into the
pulmonary artery. The blood then passes through the arterial branchings of the
lungs into the pulmonary capillaries, where gas transfer with air takes place. By
diffusion, the blood exchanges inert gas as well as carbon dioxide and oxygen with
the air in the lungs. The blood then returns to the heart via the pulmonary venous
system and enters the left atrium.
The next relaxation finds it going through the mitral valve into the left ventricle
to be pumped through the aortic valve into the main artery (aorta) of the systemic
circuit. The blood then flows through the arteries branching from the aorta,
into successively smaller vessels until reaching the capillaries, where oxygen
is exchanged for carbon dioxide. The blood is now ready for another trip to the
lungs and back again. Figure 3‑2 shows how the pulmonary circulatory system is
arranged.
The larger blood vessels are somewhat elastic and have muscular walls. They
stretch and contract as blood is pumped from the heart, maintaining a slow but
adequate flow (perfusion) through the capillaries.
3-3.3

Blood Components. The average human body contains approximately five liters

of blood. Oxygen is carried mainly in the red corpuscles (red blood cells). There
are approximately 300 million red corpuscles in an average-sized drop of blood.
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3-3

Capillaries

O2

CO2

Terminal
bronchiole
CO2

Alveoli

Artery

O2

Venules Vein

Figure 3-2. Respiration and Blood Circulation. The lung’s gas exchange system is
essentially three pumps. The thorax, a gas pump, moves air through the trachea and
bronchi to the lung’s air sacs. These sacs, the alveoli, are shown with and without their
covering of pulmonary capillaries. The heart’s right ventricle, a fluid pump, moves blood
that is low in oxygen and high in carbon dioxide into the pulmonary capillaries. Oxygen
from the air diffuses into the blood while carbon dioxide diffuses from the blood into the air
in the lungs. The oxygenated blood moves to the left ventricle, another fluid pump, which
sends the blood via the arterial system to the systemic capillaries which deliver oxygen to
and collect carbon dioxide from the body’s cells.

These corpuscles are small, disc-shaped cells that contain hemoglobin to carry
oxygen. Hemoglobin is a complex chemical compound containing iron. It can
form a loose chemical combi­nation with oxygen, soaking it up almost as a sponge
soaks up liquid. Hemoglobin is bright red when it is oxygen-rich; it becomes
increasingly dark as it loses oxygen. Hemoglobin gains or loses oxygen depending
upon the partial pressure of oxygen to which it is exposed. Hemoglobin takes up
about 98 percent of the oxygen it can carry when it is exposed to the normal partial
pressure of oxygen in the lungs. Because the tissue cells are using oxygen, the
partial pressure (tension) in the tissues is much lower and the hemoglobin gives up
much of its oxygen in the tissue capillaries.
Acids form as the carbon dioxide dissolves in the blood. Buffers in the blood
neutralize the acids and permit large amounts of carbon dioxide to be carried away
to prevent excess acidity. Hemoglobin also plays an important part in transporting
carbon dioxide. The uptake or loss of carbon dioxide by blood depends mainly
upon the partial pressure (or tension) of the gas in the area where the blood is
exposed. For example, in the peripheral tissues, carbon dioxide diffuses into the
blood and oxygen diffuses into the tissues.

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Blood also contains infection-fighting white blood cells, and platelets, which are
cells essential in blood coagulation. Plasma is the colorless, watery portion of the
blood. It contains a large amount of dissolved material essential to life. The blood
also contains several substances, such as fibrinogen, associated with blood clot­
ting. Without the clotting ability, even the slightest bodily injury could cause death.
3-4

THE RESPIRATORY SYSTEM

Every cell in the body must obtain energy to maintain its life, growth, and func­
tion. Cells obtain their energy from oxidation, which is a slow, controlled burning
of food materials. Oxidation requires fuel and oxygen. Respiration is the process
of exchanging oxygen and carbon dioxide during oxidation and releasing energy
and water.
3-4.1

Gas Exchange. Few body cells are close enough to the surface to have any chance

of obtaining oxygen and expelling carbon dioxide by direct air diffusion. Instead,
the gas exchange takes place via the circulating blood. The blood is exposed to
air over a large diffusing surface as it passes through the lungs. When the blood
reaches the tissues, the small capillary vessels provide another large surface where
the blood and tissue fluids are in close contact. Gases diffuse readily at both ends
of the circuit and the blood has the remarkable ability to carry both oxygen and
carbon dioxide. This system normally works so well that even the deepest cells of
the body can obtain oxygen and get rid of excess carbon dioxide almost as readily
as if they were completely surrounded by air.
If the membrane surface in the lung, where blood and air come close together,
were just an exposed sheet of tissue like the skin, natural air currents would keep
fresh air in contact with it. Actually, this lung membrane surface is many times
larger than the skin area and is folded and compressed into the small space of the
lungs that are protected inside the bony cage of the chest. This makes it necessary
to continually move air in and out of the space. The processes of breathing and the
exchange of gases in the lungs are referred to as ventilation and pulmonary gas
exchange, respectively.

3-4.2

Respiration Phases. The complete process of respiration includes six important

phases:

1. Ventilation of the lungs with fresh air
2. Exchange of gases between blood and air in lungs
3. Transport of gases by blood
4. Exchange of gases between blood and tissue fluids
5. Exchange of gases between the tissue fluids and cells
6. Use and production of gases by cells

If any one of the processes stops or is seriously hindered, the affected cells cannot
function normally or survive for any length of time. Brain tissue cells, for example,

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3-5

stop working almost immediately and will either die or be permanently injured in
a few minutes if their oxygen supply is completely cut off.
The respiratory system is a complex of organs and structures that performs the
pulmonary ventilation of the body and the exchange of oxygen and carbon dioxide
between the ambient air and the blood circulating through the lungs. It also warms
the air passing into the body and assists in speech production by providing air to
the larynx and the vocal chords. The respiratory tract is divided into upper and
lower tracts.
3-4.3

Upper and Lower Respiratory Tract. The upper respiratory tract consists of the

nose, nasal cavity, frontal sinuses, maxillary sinuses, larynx, and trachea. The
upper respiratory tract carries air to and from the lungs and filters, moistens and
warms air during each inhalation.
The lower respiratory tract consists of the left and right bronchi and the lungs,
where the exchange of oxygen and carbon dioxide occurs during the respiratory
cycle. The bronchi divide into smaller bronchioles in the lungs, the bronchioles
divide into alveolar ducts, the ducts into alveolar sacs, and the sacs into alveoli. The
alveolar sacs and the alveoli present about 850 square feet of surface area for the
exchange of oxygen and carbon dioxide that occurs between the internal alve­olar
surface and the tiny capillaries surrounding the external alveolar wall.
3-4.4

The Respiratory Apparatus. The mechanics of taking fresh air into the lungs

(inspiration or inhalation) and expelling used air from the lungs (expiration or
exhalation) is diagrammed in Figure 3-3. By elevating the ribs and lowering the
diaphragm, the volume of the lung is increased. Thus, according to Boyle’s Law,
a lower pressure is created within the lungs and fresh air rushes in to equalize this
lowered pressure. When the ribs are lowered again and the diaphragm rises to its
original position, a higher pressure is created within the lungs, expelling the used
air.

3‑4.4.1

3‑4.4.2

The Chest Cavity. The chest cavity does not have space between the outer lung
surfaces and the surrounding chest wall and diaphragm. Both surfaces are covered
by membranes; the visceral pleura covers the lung and the parietal pleura lines the
chest wall. These pleurae are separated from each other by a small amount of fluid
that acts as a lubri­cant to allow the membranes to slide freely over themselves as
the lungs expand and contract during respiration.
The Lungs. The lungs are a pair of light, spongy organs in the chest and are the

main component of the respiratory system (see Figure 3‑4). The highly elastic
lungs are the main mechanism in the body for inspiring air from which oxygen is
extracted for the arte­rial blood system and for exhaling carbon dioxide dispersed
from the venous system. The lungs are composed of lobes that are smooth and
shiny on their surface. The lungs contain millions of small expandable air sacs
(alveoli) connected to air passages. These passages branch and rebranch like the

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Spinal Column

First Rib
Vertebrae
Deep Inspiration

Seventh Rib
Ordinary Inspiration

Inspiration

Quiet Inspiration

Expiration

Figure 3-3. Inspiration Process. Inspiration involves both raising the rib cage (left panel) and lowering the
diaphragm (right panel). Both movements enlarge the volume of the thoracic cavity and draw air into the lung.

Apex
Upper Lobes
Pulmonary
Arteries

Horizontal
Fissure

Right Bronchus
Left Bronchus

Root

Costal
Surface
Cardiac
Notch or
Impression

Pulmonary Veins
Middle Lobe

Lower Lobes

Oblique
Fissure

Oblique
Fissure

Base

Right Lung

Left Lung

Figure 3-4. Lungs Viewed from Medical Aspect.

twigs of a tree. Air entering the main airways of the lungs gains access to the
entire surface of these alveoli. Each alveolus is lined with a thin membrane and is
surrounded by a network of very small vessels that make up the capillary bed of
the lungs. Most of the lung membrane has air on one side of it and blood on the
other; diffusion of gases takes place freely in either direction.

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Inspiratory
reserve
volume
Vital
capacity

Expiratory
reserve
volume

Tidal
volume

Total
lung
capacity

Residual volume
Figure 3-5. Lung Volumes. The heavy line is a tracing, derived from a subject breathing
to and from a sealed recording bellows. Following several normal tidal breaths, the subject
inhales maximally, then exhales maximally. The volume of air moved during this maximal
effort is called the vital capacity. During exercise, the tidal volume increases, using part
of the inspiratory and expiratory reserve volumes. The tidal volume, however, can never
exceed the vital capacity. The residual volume is the amount of air remaining in the lung
after the most forceful expiration. The sum of the vital capacity and the residual volume is
the total lung capacity.

3-4.5

Respiratory Tract Ventilation Definitions. Ventilation of the respiratory system
establishes the proper composition of gases in the alveoli for exchange with the
blood. The following definitions help in understanding respiration (Figure 3-5).
Respiratory Cycle. The respiratory cycle is one complete breath consisting of an

inspiration and exhalation, including any pause between the movements.

Respiratory Rate. The number of complete respiratory cycles that take place in

1 minute is the respiratory rate. An adult at rest normally has a respiratory rate of
approximately 12 to 16 breaths per minute.
Total Lung Capacity. The total lung capacity (TLC) is the total volume of air that
the lungs can hold when filled to capacity. TLC is normally between five and six
liters.

Vital Capacity. Vital capacity is the volume of air that can be expelled from the
lungs after a full inspiration. The average vital capacity is between four and five
liters.
Tidal Volume. Tidal volume is the volume of air moved in or out of the lungs during

a single normal respiratory cycle. The tidal volume generally averages about onehalf liter for an adult at rest. Tidal volume increases considerably during physical
exertion, and may be as high as 3 liters during severe work.

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Respiratory Minute Volume. The respiratory minute volume (RMV) is the total

amount of air moved in or out of the lungs in a minute. The respiratory minute
volume is calculated by multiplying the tidal volume by the respiratory rate.
RMV varies greatly with the body’s activity. It is about 6 to 10 liters per minute at
complete rest and may be over 100 liters per minute during severe work.

Maximal Breathing Capacity and Maximum Ventilatory Volume. The maximum

breathing capacity (MBC) and maximum voluntary ventilation (MVV) are the
greatest respiratory minute volumes that a person can produce during a short
period of extremely forceful breathing. In a healthy young man, they may average
as much as 180 liters per minute (the range is 140 to 240 liters per minute).
Maximum Inspiratory Flow Rate and Maximum Expiratory Flow Rate. The maxi-

mum inspiratory flow rate (MIFR) and maximum expiratory flow rate (MEFR) are
the fastest rates at which the body can move gases in and out of the lungs. These
rates are important in designing breathing equipment and computing gas use under
various workloads. Flow rates are usually expressed in liters per second.
Respiratory Quotient. Respiratory quotient (RQ) is the ratio of the amount

of carbon dioxide produced to the amount of oxygen consumed during cellular
processes per unit time. This value ranges from 0.7 to 1.0 depending on diet and
physical exertion and is usually assumed to be 0.9 for calculations. This ratio is
significant when calculating the amount of carbon dioxide produced as oxygen is
used at various workloads while using a closed-circuit breathing apparatus. The
duration of the carbon dioxide absorbent canister can then be compared to the
duration of the oxygen supply.
Respiratory Dead Space. Respiratory dead space refers to the part of the respira­
tory system that has no alveoli, and in which little or no exchange of gas between
air and blood takes place. It normally amounts to less than 0.2 liter. Air occupying
the dead space at the end of expiration is rebreathed in the following inspiration.
Parts of a diver’s breathing apparatus can add to the volume of the dead space and
thus reduce the proportion of the tidal volume that serves the purpose of respira­
tion. To compensate, the diver must increase his tidal volume. The problem can
best be visualized by using a breathing tube as an example. If the tube contains
one liter of air, a normal exhalation of about one liter will leave the tube filled with
used air from the lungs. At inhalation, the used air will be drawn right back into
the lungs. The tidal volume must be increased by more than a liter to draw in the
needed fresh supply, because any fresh air is diluted by the air in the dead space.
Thus, the air that is taken into the lungs (inspired air) is a mixture of fresh and dead
space gases.
3-4.6

Alveolar/Capillary Gas Exchange. Within the alveolar air spaces, the composition

of the air (alveolar air) is changed by the elimination of carbon dioxide from the
blood, the absorption of oxygen by the blood, and the addition of water vapor. The
air that is exhaled is a mixture of alveolar air and the inspired air that remained in
the dead space.

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3-9

The blood in the capillary bed of the lungs is exposed to the gas pressures of alve­
olar air through the thin membranes of the air sacs and the capillary walls. With
this exposure taking place over a vast surface area, the gas pressure of the blood
leaving the lungs is approximately equal to that present in alveolar air.
When arterial blood passes through the capillary network surrounding the cells in
the body tissues it is exposed to and equalizes with the gas pressure of the tissues.
Some of the blood’s oxygen is absorbed by the cells and carbon dioxide is picked
up from these cells. When the blood returns to the pulmonary capillaries and is
exposed to the alveolar air, the partial pressures of gases between the blood and the
alveolar air are again equalized.
Carbon dioxide diffuses from the blood into the alveolar air, lowering its partial
pressure, and oxygen is absorbed by the blood from the alveolar air, increasing its
partial pressure. With each complete round of circulation, the blood is the medium
through which this process of gas exchange occurs. Each cycle normally requires
approximately 20 seconds.
3-4.7

Breathing Control. The amount of oxygen consumed and carbon dioxide produced

increases mark­
edly when a diver is working. The amount of blood pumped
through the tissues and the lungs per minute increases in proportion to the rate at
which these gases must be transported. As a result, more oxygen is taken up from
the alveolar air and more carbon dioxide is delivered to the lungs for disposal. To
maintain proper blood levels, the respiratory minute volume must also change in
proportion to oxygen consumption and carbon dioxide output.
Changes in the partial pressure (concentration) of oxygen and carbon dioxide
(ppO2 and ppCO2) in the arterial circulation activate central and peripheral
chemoreceptors. These chemoreceptors are attached to important arteries. The
most important are the carotid bodies in the neck and aortic bodies near the heart.
The chemoreceptor in the carotid artery is activated by the ppCO2 in the blood and
signals the respiratory center in the brain stem to increase or decrease respiration.
The chemoreceptor in the aorta causes the aortic body reflex. This is a normal
chemical reflex initiated by decreased oxygen concentration and increased carbon
dioxide concentration in the blood. These changes result in nerve impulses that
increase respiratory activity. Low oxygen tension alone does not increase breathing
markedly until dangerous levels are reached. The part played by chemoreceptors is
evident in normal processes such as breathholding.
As a result of the regulatory process and the adjustments they cause, the blood
leaving the lungs usually has about the same oxygen and carbon dioxide levels
during work that it did at rest. The maximum pumping capacity of the heart (blood
circulation) and respiratory system (ventilation) largely determines the amount of
work a person can do.

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3-4.8

Oxygen Consumption. A diver’s oxygen consumption is an important factor

when determining how long breathing gas will last, the ventilation rates required
to maintain proper helmet oxygen level, and the length of time a canister will
absorb carbon dioxide. Oxygen consumption is a measure of energy expenditure
and is closely linked to the respi­ratory processes of ventilation and carbon dioxide
production.
Oxygen consumption is measured in liters per minute (l/min) at Standard Temper­
ature (0°C, 32°F) and Pressure (14.7 psia, 1 ata), Dry Gas (STPD). These rates of
oxygen consumption are not depth dependent. This means that a fully charged MK
16 oxygen bottle containing 360 standard liters (3.96 scf) of usable gas will last
225 minutes at an oxygen consumption rate of 1.6 liters per minute at any depth,
provided no gas leaks from the rig.
Minute ventilation, or respiratory minute volume (RMV), is measured at BTPS
(body temperature 37°C/98.6°F, ambient barometric pressure, saturated with water
vapor at body temperature) and varies depending on a person’s activity level,
as shown in Figure 3‑6. Surface RMV can be approximated by multiplying the
oxygen consumption rate by 25. Although this 25:1 ratio decreases with increasing
gas density and high inhaled oxygen concentrations, it is a good rule-of-thumb
approximation for computing how long the breathing gas will last.
Unlike oxygen consumption, the amount of gas a diver inhales is depth dependent.
At the surface, a diver swimming at 0.5 knot inhales 20 l/min of gas. A SCUBA
cylinder containing 71.2 standard cubic feet (scf) of air (approximately 2,000
stan­dard liters) lasts approximately 100 minutes. At 33 fsw, the diver still inhales
20 l/min at BTPS, but the gas is twice as dense; thus, the inhalation would be
approxi­mately 40 standard l/min and the cylinder would last only half as long, or
50 minutes. At three atmospheres, the same cylinder would last only one-third as
long as at the surface.
Carbon dioxide production depends only on the level of exertion and can be
assumed to be independent of depth. Carbon dioxide production and RQ are used
to compute ventilation rates for chambers and free-flow diving helmets. These
factors may also be used to determine whether the oxygen supply or the duration
of the CO2 absorbent will limit a diver’s time in a closed or semi-closed system.
3-5

RESPIRATORY PROBLEMS IN DIVING.

Physiological problems often occur when divers are exposed to the pressures of
depth. However, some of the difficulties related to respiratory processes can occur
at any time because of an inadequate supply of oxygen or inadequate removal of
carbon dioxide from the tissue cells. Depth may modify these problems for the
diver, but the basic difficulties remain the same. Fortunately, the diver has normal
physiological reserves to adapt to environmental changes and is only marginally
aware of small changes. The extra work of breathing reduces the diver’s ability to
do heavy work at depth, but moderate work can be done with adequate equipment
at the maximum depths currently achieved in diving.

CHAPTER 3 — Underwater Physiology and Diving Disorders

3-11

Figure 3-6. Oxygen Consumption and RMV at Different Work Rates.

3-5.1

Oxygen Deficiency (Hypoxia). Hypoxia, is an abnormal deficiency of oxygen in

the arterial blood. Severe hypoxia will impede the normal function of cells and
eventually kill them. The brain is the most vulnerable organ in the body to the
effects of hypoxia.

The partial pressure of oxygen (ppO2) determines whether the amount of oxygen
in a breathing medium is adequate. Air contains approximately 21 percent oxygen
and provides an ample ppO2 of about 0.21 ata at the surface. A drop in ppO2 below
0.16 ata causes the onset of hypoxic symptoms. Most individuals become hypoxic
to the point of helplessness at a ppO2 of 0.11 ata and unconscious at a ppO2 of 0.10
ata. Below this level, permanent brain damage and eventually death will occur. In

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U.S. Navy Diving Manual — Volume 1

diving, a lower percentage of oxygen will suffice as long as the total pressure is
sufficient to maintain an adequate ppO2. For example, 5 percent oxygen gives a
ppO2 of 0.20 ata for a diver at 100 fsw. On ascent, however, the diver would rapidly
experience hypoxia if the oxygen percentage were not increased.
3‑5.1.1

Causes of Hypoxia. The causes of hypoxia vary, but all interfere with the normal
oxygen supply to the body. For divers, interference of oxygen delivery can be
caused by:

n Improper line up of breathing gases resulting in a low partial pressure of oxygen
in the breathing gas supply.
n Partial or complete blockage of the fresh gas injection orifice in a semiclosedcircuit UBA. Failure of the oxygen addition valve in closed circuit rebreathers
like the MK 16.
n Inadequate purging of breathing bags in closed-circuit oxygen rebreathers like
the MK 25.
n Blockage of all or part of the air passages by vomitus, secretions, water, or
foreign objects.
n Collapse of the lung due to pneumothorax.
n Paralysis of the respiratory muscles from spinal cord injury.
n Accumulation of fluid in the lung tissues (pulmonary edema) due to diving
in cold water while overhydrated, negative pressure breathing, inhalation of
water in a near drowning episode, or excessive accumulation of venous gas
bubbles in the lung during decompression. The latter condition is referred to
as “chokes”. Pulmonary edema causes a mismatch of alveolar ventilation and
pulmonary blood flow and decreases the rate of transfer of oxygen across the
alveolar capillary membrane.
n Carbon monoxide poisoning. Carbon monoxide interferes with the transport of
oxygen by the hemoglobin in red blood cells and blocks oxygen utilization at
the cellular level.
n Breathholding. During a breathhold the partial pressure of oxygen in the lung
falls progressively as the body continues to consume oxygen. If the breathhold
is long enough, hypoxia will occur.
3‑5.1.2

Symptoms of Hypoxia. The symptoms of hypoxia include:

n Loss of judgment
n Lack of concentration
n Lack of muscle control

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3-13

n Inability to perform delicate or skill-requiring tasks
n Drowsiness
n Weakness
n Agitation
n Euphoria
n Loss of consciousness
Brain tissue is by far the most susceptible to the effects of hypoxia. Unconscious­
ness and death can occur from brain hypoxia before the effects on other tissues
become very prominent.
There is no reliable warning of the onset of hypoxia. It can occur unexpectedly,
making it a particularly serious hazard. A diver who loses his air supply is in danger
of hypoxia, but he immediately knows he is in danger and usually has time to do
something about it. He is much more fortunate than a diver who gradually uses up
the oxygen in a closed-circuit rebreathing rig and has no warning of impending
unconsciousness.
When hypoxia develops, pulse rate and blood pressure increase as the body tries
to offset the hypoxia by circulating more blood. A small increase in breathing may
also occur. A general blueness (cyanosis) of the lips, nail beds, and skin may occur
with hypoxia. This may not be noticed by the diver and often is not a reliable indi­
cator of hypoxia, even for the trained observer at the surface. The same signs could
be caused by prolonged exposure to cold water.
If hypoxia develops gradually, symptoms of interference with brain function will
appear. None of these symptoms, however, are sufficient warning and very few
people are able to recognize the mental effects of hypoxia in time to take correc­tive
action.
3‑5.1.3

Treatment of Hypoxia. A diver suffering from severe hypoxia must be rescued

promptly. Treat with basic first aid and 100% oxygen. If a victim of hypoxia is
given gas with adequate oxygen content before his breathing stops, he usually
regains consciousness shortly and recovers completely. For SCUBA divers, this
usually involves bringing the diver to the surface. For surface-supplied mixedgas divers, it involves shifting the gas supply to alternative banks and ventilating
the helmet or chamber with the new gas. Refer to Volume 4 for information on
treatment of hypoxia arising in specific operational environments for dives
involving semi-closed and closed-circuit rebreathers.
3‑5.1.4

Prevention of Hypoxia. Because of its insidious nature and potentially fatal

outcome, preventing hypoxia is essential. In open-circuit SCUBA and helmets,
hypoxia is unlikely unless the supply gas has too low an oxygen content. On
mixed-gas operations, strict atten­tion must be paid to gas analysis, cylinder lineups
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and predive checkout procedures. In closed and semi-closed circuit rebreathers,
a malfunction can cause hypoxia even though the proper gases are being used.
Electronically controlled, fully closed-circuit Underwater Breathing Apparatus
(UBAs), like the MK 16, have oxygen sensors to read out oxygen partial
pressure, but divers must be constantly alert to the possibility of hypoxia from a
UBA malfunction. To prevent hypoxia, oxygen sensors should be monitored
closely throughout the dive. MK 25 UBA breathing bags should be purged
in accordance with Operating Procedures (OPs). Recently surfaced mixed-gas
chambers should not be entered until after they are thoroughly ventilated with air.
3-5.2

Carbon Dioxide Retention (Hypercapnia). Hypercapnia is an abnormally high

level of carbon dioxide in the blood and body tissues.

3‑5.2.1

Causes of Hypercapnia. In diving operations, hypercapnia is generally the result

of a buildup of carbon dioxide in the breathing supply or an inadequate respiratory
minute volume. The principal causes are:
n Excess carbon dioxide levels in compressed air supplies due to improper
placement of the compressor inlet.
n Inadequate ventilation of surface-supplied helmets or UBAs.

n Failure of carbon dioxide absorbent canisters to absorb carbon dioxide or
incorrect installation of breathing hoses in closed or semi-closed circuit UBAs.
n Inadequate lung ventilation in relation to exercise level. The latter may be
caused by skip breathing, increased apparatus dead space, excessive breathing
resistance, or increased oxygen partial pressure.
Excessive breathing resistance is an important cause of hypercapnia and arises
from two sources: flow resistance and static lung load. Flow resistance results from
the flow of dense gas through tubes, hoses, and orifices in the diving equip­ment
and through the diver’s own airways. As gas density increases, a larger driving
pressure must be applied to keep gas flowing at the same rate. The diver has to
exert higher negative pressures to inhale and higher positive pressures to exhale.
As ventilation increases with increasing levels of exercise, the necessary driving
pressures increase. Because the respiratory muscles can only exert so much effort
to inhale and exhale, a point is reached when further increases cannot occur. At this
point, metabolically produced carbon dioxide is not adequately eliminated and in­
creases in the blood and tissues, causing symptoms of hyper­capnia. Symptoms of
hypercapnia usually become apparent when divers attempt heavy work at depths
deeper then 120 FSW on air or deeper than 850 FSW on helium-oxygen. At very
great depths (1,600-2,000 FSW), shortness of breath and other signs of carbon di­
oxide toxicity may occur even at rest.

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3-15

Static lung load is the result of breathing gas being supplied at a different pressure
than the hydrostatic pressure surrounding the lungs. For example, when swimming
horizontally with a single-hose regulator, the regulator diaphragm is lower than the
mouth and the regulator supplies gas at a slight positive pressure once the demand
valve has opened. If the diver flips onto his back, the regulator diaphragm is shal­
lower than his mouth and the regulator supplies gas at a slightly negative pressure.
Inhalation is harder but exhalation is easier because the exhaust ports are above the
mouth and at a slightly lower pressure.
Static lung loading is more apparent in closed and semi-closed circuit underwater
breathing apparatus such as the MK 25 and MK 16. When swimming horizontally
with the MK 16, the diaphragm on the diver’s back is shallower than the lungs and
the diver feels a negative pressure at the mouth. Exhalation is easier than inhala­
tion. If the diver flips onto his back, the diaphragm is below the lungs and the diver
feels a positive pressure at the mouth. Inhalation becomes easier than exhala­tion.
Static lung load is an important contributor to hypercapnia.
Excessive breathing resistance may cause shortness of breath and a sensation of
labored breathing (dyspnea) without any increase in blood carbon dioxide level. In
this case, the sensation of shortness of breath is due to activation of pressure and
stretch receptors in the airways, lungs, and chest wall rather than activation of the
chemoreceptors in the brain stem and carotid and aortic bodies. Usually, both types
of activation are present when breathing resistance is excessive.
3‑5.2.2

Symptoms of Hypercapnia. Hypercapnia affects the brain differently than hypoxia

does. However, it can result in similar symptoms. Symptoms of hypercapnia
include:
n Increased breathing rate
n Shortness of breath, sensation of difficult breathing or suffocation (dyspnea)
n Confusion or feeling of euphoria
n Inability to concentrate
n Increased sweating
n Drowsiness
n Headache
n Loss of consciousness
n Convulsions

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The increasing level of carbon dioxide in the blood stimulates the respiratory center
to increase the breathing rate and volume. The pulse rate also often increases. On
dry land, the increased breathing rate is easily noticed and uncom­fortable enough
to warn the victim before the rise in ppCO2 becomes dangerous. This is usually not
the case in diving. Factors such as water temperature, work rate, increased breath­
ing resistance, and an elevated ppO2 in the breathing mixture may produce changes
in respiratory drive that mask changes caused by excess carbon dioxide. This is es­
pecially true in closed-circuit UBAs, particularly 100-percent oxygen rebreathers.
In cases where the ppO2 is above 0.5 ata, the short­ness of breath usually associated
with excess carbon dioxide may not be prominent and may go unnoticed by the
diver, especially if he is breathing hard because of exertion. In these cases the diver
may become confused and even slightly euphoric before losing consciousness. For
this reason, a diver must be particularly alert for any marked change in his breath­
ing comfort or cycle (such as shortness of breath or hyperventilation) as a warning
of hypercapnia. A similar situation can occur in cold water. Exposure to cold water
often results in an increase in respiratory rate. This increase can make it difficult
for the diver to detect an increase in respiratory rate related to a buildup of carbon
dioxide.
Injury from hypercapnia is usually due to secondary effects such as drowning or
injury caused by decreased mental function or unconsciousness. A diver who loses
consciousness because of excess carbon dioxide in his breathing medium and does
not inhale water generally revives rapidly when given fresh air and usually feels
normal within 15 minutes. The after effects rarely include symptoms more serious
than headache, nausea, and dizziness. Permanent brain damage and death are much
less likely than in the case of hypoxia. If breathing resistance was high, the diver
may note some respiratory muscle soreness post-dive.
Excess carbon dioxide also dilates the arteries of the brain. This may partially
explain the headaches often associated with carbon dioxide intoxication, though
these headaches are more likely to occur following the exposure than during it.
The increase in blood flow through the brain, which results from dilation of the
arteries, is thought to explain why carbon dioxide excess speeds the onset of CNS
oxygen toxicity. Excess carbon dioxide during a dive is also believed to increase
the likelihood of decompression sickness, but the reasons are less clear.
The effects of nitrogen narcosis and hypercapnia are additive. A diver under the
influence of narcosis will probably not notice the warning signs of carbon dioxide
intoxication. Hypercapnia in turn will intensify the symptoms of narcosis.
3‑5.2.3

Treatment of Hypercapnia. Hypercapnia is treated by:

n Decreasing the level of exertion to reduce CO2 production
n Increasing helmet and lung ventilation to wash out excess CO2
n Shifting to an alternate breathing source or aborting the dive if defective
equipment is the cause.

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3-17

Because the first sign of hypercapnia may be unconsciousness and it may not be
readily apparent whether the cause is hypoxia or hypercapnia. It is important to
rule out hypoxia first because of the significant potential for brain damage in hy­
poxia. Hypercapnia may cause unconsciousness, but by itself will not injure the
brain permanently.
3‑5.2.4

Prevention of Hypercapnia. In surface-supplied diving, hypercapnia is prevented

by ensuring that gas supplies do not contain excess carbon dioxide, by maintaining
proper manifold pressure during the dive and by ventilating the helmet frequently
with fresh gas. For dives deeper than 150 fsw, helium-oxygen mixtures should be
used to reduce breathing resistance. In closed or semiclosed-circuit UBAs, hyper­
capnia is prevented by carefully filling the CO2 absorbent canister and limiting
dive duration to estab­lished canister duration limits. For dives deeper than 150 fsw,
helium-oxygen mixtures should be used to reduce breathing resistance.
3-5.3

Asphyxia. Asphyxia is a condition where breathing stops and both hypoxia and

hypercapnia occur simultaneously. Asphyxia will occur when there is no gas to
breathe, when the airway is completely obstructed, when the respiratory muscles
become para­lyzed, or when the respiratory center fails to send out impulses to
breathe. Running out of air is a common cause of asphyxia in SCUBA diving.
Loss of the gas supply may also be due to equipment failure, for example regulator
freeze up. Divers who become unconscious as a result of hypoxia, hypercapnia,
or oxygen toxicity may lose the mouthpiece and suffer asphyxia. Obstruction of
the airway can be caused by injury to the windpipe, the tongue falling back in the
throat during unconsciousness, or the inhalation of water, saliva, vomitus or a for­
eign body. Paralysis of the respiratory muscles may occur with high cervical spinal
cord injury due to trauma or decompression sickness. The respiratory center in the
brain stem may become non-functional during a prolonged episode of hypoxia.
3-5.4

3‑5.4.1

Drowning is fluid induced asphyxia. Near drowning is
the term used when a victim is successfully resuscitated following a drowning epi­
sode.
Drowning/Near Drowning.

Causes of Drowning. A swimmer or diver can fall victim to drowning because of

overexertion, panic, inability to cope with rough water, exhaustion, or the effects
of cold water or heat loss. Drowning in a hard-hat diving rig is rare. It can happen
if the helmet is not properly secured and comes off, or if the diver is trapped in a
head-down position with a water leak in the helmet. Normally, as long as the diver
is in an upright position and has a supply of air, water can be kept out of the helmet
regardless of the condition of the suit. Divers wearing lightweight or SCUBA gear
can drown if they lose or ditch their mask or mouthpiece, run out of air, or inhale
even small quantities of water. This could be the direct result of failure of the air
supply, or panic in a hazardous situation. The SCUBA diver, because of direct
exposure to the environment, can be affected by the same conditions that may
cause a swimmer to drown.

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Symptoms of Near Drowning.

3‑5.4.2

n Unconsciousness
n Pulmonary edema
n Increased respiratory rate.
Treatment of unconscious drowning victims.

3‑5.4.3

n In water rescue requires ventilation alone.
1. Open/Maintain an airway.
2. Check breathing
3. Provide 5 rescue breaths if victim not breathing.
4. DO NOT attempt chest compressions in water.
n The victim should be assumed to be in cardiac arrest if there is no response to
rescue breaths.
n Once on a stable platform, the patient should be placed in the supine position
n It is possible that the patient may only need ventilation.
NOTE:

It is important that we revert back to the ABC method for drowning, rather
than the updated CAB.

A: Airway = Make sure airway is open
B: Breathing = Check for breathing; if victim is not breathing, give 2 rescue
breaths (if not already done in water rescue).
C: Circulation = Check circulation by feeling for pulse; if pulse is absent,
initiate chest compressions.
„„ Patient should be placed on 100% O2 and AED placed on chest – although a

shockable rhythm is unlikely.

„„ Be prepared to turn patient on their side and suction their airway – vomiting is

common.

„„ Even if AGE/DCS cannot be ruled out – immediately transport patient to nearest

hospital for continued treatment of cardiac/respiratory arrest. The mildest cases
of drowning will still require post rescue hospitalization and possibly intensive
care.

3‑5.4.4

Prevention of Near Drowning. Drowning is best prevented by thoroughly training

divers in safe diving practices and carefully selecting diving personnel. A trained

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3-19

diver should not easily fall victim to drowning. However, overconfidence can give
a feeling of false security that might lead a diver to take dangerous risks.
3-5.5

Breathholding and Unconsciousness. Most people can hold their breath approxi­

mately 1 minute, but usually not much longer without training or special prepara­
tion. At some time during a breath­holding attempt, the desire to breathe becomes
uncontrollable. The demand to breathe is signaled by the respiratory center re­
sponding to the increasing levels of carbon dioxide in the arterial blood and pe­
ripheral chemoreceptors responding to the corresponding fall in arterial oxygen
partial pressure. If the breathhold is preceded by a period of voluntary hyperventi­
lation, the breathhold can be much longer. Voluntary hyperventilation lowers body
stores of carbon dioxide below normal (a condition known as hypocapnia), with­
out significantly increasing oxygen stores. During the breathhold, it takes an ap­
preciable time for the body stores of carbon dioxide to return to the normal level
then to rise to the point where breathing is stimulated. During this time the oxy­
gen partial pressure may fall below the level necessary to maintain consciousness.
This is a common cause of breathholding accidents in swimming pools. Extended
breathholding after hyper­ventilation is not a safe procedure.
WARNING

Voluntary hyperventilation is dangerous and can lead to unconsciousness and death during breathhold dives.

Another hazard of breathhold diving is the possible loss of consciousness from
hypoxia during ascent. Air in the lungs is compressed during descent, raising the
oxygen partial pressure. The increased ppO2 readily satisfies the body’s oxygen
demand during descent and while on the bottom, even though a portion is being
consumed by the body. During ascent, the partial pressure of the remaining oxygen
is reduced rapidly as the hydrostatic pressure on the body lessens. If the ppO2
falls below 0.10 ata (10% sev), unconsciousness may result. This danger is further
heightened when hyperventilation has eliminated normal body warning signs of
carbon dioxide accumulation and allowed the diver to remain on the bottom for a
longer period of time. Refer to Chapter 6 for breathhold diving restrictions.
3-5.6

Involuntary Hyperventilation. Hyperventilation is the term applied to breathing

more than is necessary to keep the body’s carbon dioxide tensions at proper level.
Hyperventilation may be volun­tary (for example, to increase breathholding time)
or involuntary. In involuntary hyperventilation, the diver is either unaware that he
is breathing excessively, or is unable to control his breathing.
3‑5.6.1

Causes of Involuntary Hyperventilation. Involuntary hyperventilation can be

triggered by fear experienced during stressful situations. It can also be initiated by
the slight “smothering sensation” that accom­panies an increase in equipment dead
space, an increase in static lung loading, or an increase in breathing resistance. Cold
water exposure can add to the sensation of needing to breathe faster and deeper.
Divers using SCUBA equipment for the first few times are likely to hyperventilate
to some extent because of anxiety.
3‑5.6.2

3-20

Symptoms of Involuntary Hyperventilation. Hyperventilation may lead to a
biochemical imbalance that gives rise to dizziness, tingling of the extremities, and

U.S. Navy Diving Manual — Volume 1

spasm of the small muscles of the hands and feet. Hyperventilating over a long
period, produces additional symptoms such as weak­ness, headaches, numbness,
faintness, and blurring of vision. The diver may experience a sensation of “air
hunger” even though his ventilation is more than enough to eliminate carbon
dioxide. All these symptoms can be easily confused with symptoms of CNS oxygen
toxicity.
3‑5.6.3

3-5.7

Treatment of Involuntary Hyperventilation. Hyperventilation victims should
be encouraged to relax and slow their breathing rates. The body will correct
hyperventilation naturally.
Overbreathing the Rig. “Overbreathing the Rig” is a special term divers apply to
an episode of acute hypercapnia that develops when a diver works at a level greater
than his UBA can support. When a diver starts work, or abruptly increases his
workload, the increase in respiratory minute ventilation lags the increase in oxygen
consumption and carbon dioxide production by several minutes. When the RMV
demand for that workload finally catches up, the UBA may not be able to supply
the gas necessary despite extreme respiratory efforts on the part of the diver. Acute
hyper­capnia with marked respiratory distress ensues. Even if the diver stops work
to lower the production of carbon dioxide, the sensation of shortness of breath may
persist or even increase for a short period of time. When this occurs, the inexperi­
enced diver may panic and begin to hyperventilate. The situation can rapidly
develop into a malicious cycle of severe shortness of breath and uncontrollable
hyperventilation. In this situation, if even a small amount of water is inhaled, it
can cause a spasm of the muscles of the larynx (voice box), called a laryngospasm,
followed by asphyxia and possible drowning.

The U.S. Navy makes every effort to ensure that UBA meet adequate breathing
standards to minimize flow resistance and static lung loading problems. However,
all UBA have their limitations and divers must have sufficient experience to
recognize those limitations and pace their work accordingly. Always increase
workloads gradually to insure that the UBA can match the demand for increased
lung ventilation. If excessive breathing resistance is encountered, slow or stop
the pace of work until a respiratory comfort level is achieved. If respiratory
distress occurs following an abrupt increase in workload, stop work and take even
controlled breaths until the sensation of respiratory distress subsides. If the situa­
tion does not improve, abort the dive.
3-5.8

Carbon Monoxide Poisoning. The body produces carbon monoxide as a part of

the process of normal metabo­lism. Consequently, there is always a small amount
of carbon monoxide present in the blood and tissues. Carbon monoxide poisoning
occurs when levels of carbon monoxide in the blood and tissues rise above these
normal values due to the pres­ence of carbon monoxide in the diver’s gas supply.
Carbon monoxide not only blocks hemoglobin’s ability to delivery oxygen to the
cells, causing cellular hypoxia, but also poisons cellular metabolism directly.
3‑5.8.1

Causes of Carbon Monoxide Poisoning. Carbon monoxide is not found in any

significant quantity in fresh air. Carbon monoxide poisoning is usually caused by

CHAPTER 3 — Underwater Physiology and Diving Disorders

3-21

a compressor’s intake being too close to the exhaust of an internal combustion
engine or malfunction of a oil lubricated compressor. Concentrations as low as
0.002 ata (2,000 ppm, or 0.2%) can prove fatal.
3‑5.8.2

Symptoms of Carbon Monoxide Poisoning. The symptoms of carbon monoxide

poisoning are almost identical to those of hypoxia. When toxicity develops
gradually the symptoms are:
n Headache
n Dizziness
n Confusion
n Nausea
n Vomiting
n Tightness across the forehead
When carbon monoxide concentrations are high enough to cause rapid onset of
poisoning, the victim may not be aware of any symptoms before he becomes
unconscious.
Carbon monoxide poisoning is particularly treacherous because conspicuous
symptoms may be delayed until the diver begins to ascend. While at depth, the
greater partial pressure of oxygen in the breathing supply forces more oxygen into
solution in the blood plasma. Some of this additional oxygen reaches the cells and
helps to offset the hypoxia. In addition, the increased partial pressure of oxygen
forcibly displaces some carbon monoxide from the hemoglobin. During ascent,
however, as the partial pressure of oxygen diminishes, the full effect of carbon
monoxide poisoning is felt.

3‑5.8.3

Treatment of Carbon Monoxide Poisoning. The immediate treatment of carbon

monoxide poisoning consists of getting the diver to fresh air and seeking medical
attention. Oxygen, if available, shall be administered immediately and while
transporting the patient to a hyperbaric or medical treatment facility. Hyperbaric
oxygen therapy is the definitive treatment of choice and transportation for
recompression should not be delayed except to stabilize the serious patient.
Divers with severe symptoms (i.e. severe headache, mental status changes, any
neurological symptoms, rapid heart rate) should be treated using Treatment Table
6.

3‑5.8.4

Prevention of Carbon Monoxide Poisoning. Locating compressor intakes away

from engine exhausts and maintaining air compressors in the best possible
mechanical condition can prevent carbon monoxide poisoning. When carbon
monoxide poisoning is suspected, isolate the suspect breathing gas source, and
forward gas samples for analysis as soon as possible.

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U.S. Navy Diving Manual — Volume 1

Incus

Semicircular
Canals
Vestibular Nerve

Facial Nerve
Cochlear Nerve
Cochlea
Round
Window
Eustachian Tubes

Malleus
Tympanic
Stapes
Membrane
at Oval
Window
External Auditory
Canal

Figure 3-7. Gross Anatomy of the Ear in Frontal Section.

3-6

MECHANICAL EFFECTS OF PRESSURE ON THE HUMAN BODY-BAROTRAUMA
DURING DESCENT

Barotrauma, or damage to body tissues from the mechanical effects of pressure,
results when pressure differentials between body cavities and the hydrostatic pres­
sure surrounding the body, or between the body and the diving equipment, are not
equalized properly. Barotrauma most frequently occurs during descent, but may
also occur during ascent. Barotrauma on descent is called squeeze. Barotrauma on
ascent is called reverse squeeze.
3-6.1

Prerequisites for Squeeze. For squeeze to occur during descent the following five

conditions must be met:

„„ There must be a gas-filled space. Any gas-filled space within the body (such as

a sinus cavity) or next to the body (such as a face mask) can damage the body
tissues when the gas volume changes because of increased pressure.

„„ The gas-filled space must have rigid walls. If the walls are collapsible like a

balloon, no damage will be done by compression.

„„ The gas-filled space must be enclosed. If gas or liquid can freely enter the

space as the gas volume changes, no damage will occur.

„„ The space must have lining membrane with an arterial blood supply and venous

drainage that penetrates the space from the outside. This allows blood to be
forced into the space to compensate for the change in pressure.

CHAPTER 3 — Underwater Physiology and Diving Disorders

3-23

„„ There must be a change in ambient pressure.
3-6.2

Middle Ear Squeeze. Middle ear squeeze is the most common type of barotrauma.

The anatomy of the ear is illustrated in Figure 3-7. The eardrum completely seals off
the outer ear canal from the middle ear space. As a diver descends, water pressure
increases on the external surface of the drum. To counterbalance this pressure, the
air pressure must reach the inner surface of the eardrum. This is accomplished by
the passage of air through the narrow eustachian tube that leads from the nasal
passages to the middle ear space. When the eustachian tube is blocked by mucous,
the middle ear meets four of the requirements for barotrauma to occur (gas filled
space, rigid walls, enclosed space, penetrating blood vessels).
As the diver continues his descent, the fifth requirement (change in ambient pres­
sure) is attained. As the pressure increases, the eardrum bows inward and initially
equalizes the pressure by compressing the middle ear gas. There is a limit to this
stretching capability and soon the middle ear pressure becomes lower than the
external water pressure, creating a relative vacuum in the middle ear space. This
negative pressure causes the blood vessels of the eardrum and lining of the middle
ear to first expand, then leak and finally burst. If descent continues, either the
eardrum ruptures, allowing air or water to enter the middle ear and equalize the
pressure, or blood vessels rupture and cause sufficient bleeding into the middle ear
to equalize the pressure. The latter usually happens.
The hallmark of middle ear squeeze is sharp pain caused by stretching of the
eardrum. The pain produced before rupture of the eardrum often becomes intense
enough to prevent further descent. Simply stopping the descent and ascending a
few feet usually brings about immediate relief.
If descent continues in spite of the pain, the eardrum may rupture. When rupture
occurs, this pain will diminish rapidly. Unless the diver is in hard hat diving dress,
the middle ear cavity may be exposed to water when the ear drum ruptures. This
exposes the diver to a possible middle ear infection and, in any case, prevents
the diver from diving until the damage is healed. If eardrum rupture occurs, the
dive shall be aborted. At the time of the rupture, the diver may experience the
sudden onset of a brief but violent episode of vertigo (a sensation of spinning). This
can completely disorient the diver and cause nausea and vomiting. This vertigo is
caused by violent disturbance of the malleus, incus, and stapes, or by cold water
stimulating the balance mechanism of the inner ear. The latter situation is referred
to as caloric vertigo and may occur from simply having cold or warm water enter
one ear and not the other. The eardrum does not have to rupture for caloric vertigo
to occur. It can occur as the result of having water enter one ear canal when swim­
ming or diving in cold water. Fortunately, these symptoms quickly pass when the
water reaching the middle ear is warmed by the body. Suspected cases of eardrum
rupture shall be referred to medical personnel.
3‑6.2.1

Preventing Middle Ear Squeeze. Diving with a partially blocked eustachian tube

increases the likelihood of middle ear squeeze. Divers who cannot clear their ears
on the surface should not dive. Medical personnel shall examine divers who have

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U.S. Navy Diving Manual — Volume 1

trouble clearing their ears before diving. The possibility of barotrauma can be
virtually eliminated if certain precautions are taken. While descending, stay ahead
of the pressure. To avoid collapse of the eustachian tube and to clear the ears,
frequent adjustments of middle ear pressure must be made by adding gas through
the eustachian tubes from the back of the nose. If too large a pressure difference
develops between the middle ear pressure and the external pressure, the eustachian
tube collapses as it becomes swollen and blocked. For some divers, the eustachian
tube is open all the time so no conscious effort is necessary to clear their ears.
For the majority, however, the eustachian tube is normally closed and some action
must be taken to clear the ears. Many divers can clear by yawning, swallowing, or
moving the jaw around.
Some divers must gently force gas up the eustachian tube by closing their mouth,
pinching their nose and exhaling. This is called a Valsalva maneuver. If too large
a relative vacuum exists in the middle ear, the eustachian tube collapses and no
amount of forceful clearing will open it. If a squeeze is noticed during descent,
the diver shall stop, ascend a few feet and gently perform a Valsalva maneuver. If
clearing cannot be accomplished as described above, abort the dive.
WARNING

Never do a forceful Valsalva maneuver during descent. A forceful Valsalva
maneuver can result in alternobaric vertigo or barotrauma to the inner
ear (see below).

WARNING

If decongestants must be used, check with medical personnel trained in
diving medicine to obtain medication that will not cause drowsiness and
possibly add to symptoms caused by the narcotic effect of nitrogen.

3‑6.2.2

Treating Middle Ear Squeeze. Upon surfacing after a middle ear squeeze, the

diver may complain of pain, full­ness in the ear, hearing loss, or even mild vertigo.
Occasionally, the diver may have a bloody nose, the result of blood being forced
out of the middle ear space and into the nasal cavity through the eustachian tube
by expanding air in the middle ear. The diver shall report symptoms of middle ear
squeeze to the diving supervisor and seek medical attention. Treatment consists
of taking decongestants, pain medication if needed, and cessation of diving until
the damage is healed. If the eardrum has ruptured antibiotics may be prescribed as
well. Never administer medications directly into the external ear canal if a ruptured
eardrum is suspected or confirmed unless done in direct consultation with an ear,
nose, and throat (ENT) medical specialist.
3-6.3

Sinus Squeeze. Sinuses are located within hollow spaces of the skull bones and

are lined with a mucous membrane continuous with that of the nasal cavity (Figure
3-8). The sinuses are small air pockets connected to the nasal cavity by narrow
passages. If pressure is applied to the body and the passages to any of these sinuses
are blocked by mucous or tissue growths, pain will soon be experienced in the
affected area. The situation is very much like that described for the middle ear.
3‑6.3.1

Causes of Sinus Squeeze. When the air pressure in these sinuses is less than the
pressure applied to the tissues surrounding these incompressible spaces, the same
relative effect is produced as if a vacuum were created within the sinuses: the

CHAPTER 3 — Underwater Physiology and Diving Disorders

3-25

Frontal Sinus

Orbit

Ethmoidal Sinus

Nasal Cavity

Maxillary Sinus
Sphenoid Sinus

Nasal Septum

Figure 3-8. Location of the Sinuses in the Human Skull.

lining membranes swell and, if severe enough, hemorrhage into the sinus spaces.
This process repre­sents nature’s effort to balance the relative negative air pressure
by filling the space with swollen tissue, fluid, and blood. The sinus is actually
squeezed. The pain produced may be intense enough to halt the diver’s descent.
Unless damage has already occurred, a return to normal pressure will bring about
immediate relief. If such difficulty has been encountered during a dive, the diver
may often notice a small amount of bloody nasal discharge on reaching the surface.
3‑6.3.2

Preventing Sinus Squeeze. Divers should not dive if any signs of nasal congestion

or a head cold are evident. The effects of squeeze can be limited during a dive by
halting the descent and ascending a few feet to restore the pressure balance. If the
space cannot be equal­ized by swallowing or blowing against a pinched-off nose,
the dive must be aborted.
3-6.4

Tooth Squeeze (Barodontalgia). Tooth squeeze occurs when a small pocket of

gas, generated by decay, is lodged under a poorly fitted or cracked filling. If this
pocket of gas is completely isolated, the pulp of the tooth or the tissues in the tooth
socket can be sucked into the space causing pain. If additional gas enters the tooth
during descent and does not vent during ascent, it can cause the tooth to crack
or the filling to be dislodged. Prior to any dental work, personnel shall identify
themselves as divers to the dentist.

3-6.5

3-26

External Ear Squeeze. A diver who wears ear plugs, has an infected external ear
(external otitis), has a wax-impacted ear canal, or wears a tight-fitting wet suit
hood, can develop an external ear squeeze. The squeeze occurs when gas trapped
in the external ear canal remains at atmospheric pressure while the external water
pressure increases during descent. In this case, the eardrum bows outward (opposite
of middle ear squeeze) in an attempt to equalize the pressure difference and may
rupture. The skin of the canal swells and hemorrhages, causing considerable pain.

U.S. Navy Diving Manual — Volume 1

Ear plugs must never be worn while diving. In addition to creating the squeeze,
they may be forced deep into the ear canal. When a hooded suit must be worn, air
(or water in some types) must be allowed to enter the hood to equalize pressure in
the ear canal.
3-6.6

Thoracic (Lung) Squeeze. When making a breathhold dive, it is possible to reach

a depth at which the air held in the lungs is compressed to a volume somewhat
smaller than the normal residual volume of the lungs. At this volume, the chest
wall becomes stiff and incompressible. If the diver descends further, the additional
pressure is unable to compress the chest walls, force additional blood into the blood
vessels in the chest, or elevate the diaphragm further. The pressure in the lung
becomes negative with respect to the external water pressure. Injury takes the form
of squeeze. Blood and tissue fluids are forced into the lung alveoli and air passages
where the air is under less pressure than the blood in the surrounding vessels. This
amounts to an attempt to relieve the negative pressure within the lungs by partially
filling the air space with swollen tissue, fluid, and blood. Considerable lung damage
results and, if severe enough, may prove fatal. If the diver descends still further,
death will occur as a result of the collapse of the chest. Breathhold diving shall be
limited to controlled, training situations or special operational situations involving
well-trained personnel at shallow depths.
A surface-supplied diver who suffers a loss of gas pressure or hose rupture with
failure of the nonreturn valve may suffer a lung squeeze, if his depth is great
enough, as the surrounding water pressure compresses his chest.
3-6.7

3-6.8

Face or Body Squeeze. SCUBA face masks, goggles, and certain types of exposure
suits may cause squeeze under some conditions. Exhaling through the nose can
usually equalize the pressure in a face mask, but this is not possible with goggles.
Goggles shall only be used for surface swimming. The eye and the eye socket
tissues are the most seriously affected tissues in an instance of face mask or goggle
squeeze. When using exposure suits, air may be trapped in a fold in the garment
and may lead to some discomfort and possibly a minor case of hemorrhage into the
skin from pinching.
Inner Ear Barotrauma. The inner ear contains no gas and therefore cannot be
“squeezed” in the same sense that the middle ear and sinuses can. However,
the inner ear is located next to the middle ear cavity and is affected by the same
conditions that lead to middle ear squeeze. To understand how the inner ear could
be damaged as a result of pressure imbalances in the middle ear, it is first necessary
to understand the anatomy of the middle and inner ear.

The inner ear contains two important organs, the cochlea and the vestibular appa­
ratus. The cochlea is the hearing sense organ; damage to the cochlea will result in
hearing loss and ringing in the ear (tinnitus). The vestibular apparatus is the balance
organ; damage to the vestibular apparatus will result in vertigo and unsteadiness.
There are three bones in the middle ear: the malleus, the incus, and the stapes.
They are also commonly referred to as the hammer, anvil, and stirrup, respectively
(Figure 3‑9). The malleus is connected to the eardrum (tympanic membrane) and
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3-27

Incus
Malleus
Tensor tympani
Tympanic
Membrane

Stapedius
Muscle

Stapes

Oval
Window

Eustachian
Tube

Figure 3-9. Components of the Middle Ear.

transmits sound vibrations to the incus, which in turn transmits these vibrations to
the stapes, which relays them to the inner ear. The stapes transmits these vibrations
to the inner ear fluid through a membrane-covered hole called the oval window.
Another membrane-covered hole called the round window connects the inner ear
with the middle ear and relieves pressure waves in the inner ear caused by move­ment
of the stapes. When the stapes drives the oval window inward, the round window
bulges outward to compensate. The fluid-filled spaces of the inner ear are also
connected to the fluid spaces surrounding the brain by a narrow passage called the
cochlear aqueduct. The cochlear aqueduct can transmit increases in cerebrospinal
fluid pressure to the inner ear. When Valsalva maneuvers are performed to equalize
middle ear and sinus pressure, cerebrospinal fluid pressure increases.
If middle ear pressure is not equalized during descent, the inward bulge of the
eardrum is transmitted to the oval window by the middle ear bones. The stapes
pushes the oval window inward. Because the inner ear fluids are incompressible,
the round window correspondingly bulges outward into the middle ear space. If
this condition continues, the round window may rupture spilling inner ear fluids
into the middle ear and leading to a condition know as inner ear barotrauma with
perilymph fistula. Fistula is a medical term for a hole in a membrane; the fluid
in the inner ear is called perilymph. Rupture of the oval or round windows may
also occur when middle ear pressures are suddenly and forcibly equalized. When
equalization is sudden and forceful, the eardrum moves rapidly from a position of
bulging inward maximally to bulging outward maximally. The positions of the oval
and round windows are suddenly reversed. Inner ear pressure is also increased by
transmission of the Valsalva-induced increase in cerebrospinal fluid pressure. This
puts additional stresses on these two membranes. Either the round or oval window
may rupture. Rupture of the round window is by far the most common. The oval
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window is a tougher membrane and is protected by the foot­plate of the stapes.
Even if rupture of the round or oval window does not occur, the pressure waves
induced in the inner ear during these window movements may lead to disruption
of the delicate cells involved in hearing and balance. This condi­tion is referred to
inner ear barotrauma without perilymph fistula.
The primary symptoms of inner ear barotrauma are persistent vertigo and hearing
loss. Vertigo is the false sensation of motion. The diver feels that he is moving
with respect to his environment or that the environment is moving with respect to
him, when in fact no motion is taking place. The vertigo of inner ear barotrauma is
generally described as whirling, spinning, rotating, tilting, rocking, or undu­lating.
This sensation is quite distinct from the more vague complaints of dizziness or
lightheadedness caused by other conditions. The vertigo of inner ear barotrauma
is often accompanied by symptoms that may or may not be noticed depending
on the severity of the insult. These include nausea, vomiting, loss of balance,
incoordination, and a rapid jerking movement of the eyes, called nystagmus.
Vertigo may be accentuated when the head is placed in certain posi­tions. The
hearing loss of inner ear barotrauma may fluctuate in intensity and sounds may be
distorted. Hearing loss is accompanied by ringing or roaring in the affected ear.
The diver may also complain of a sensation of bubbling in the affected ear.
Symptoms of inner ear barotrauma usually appear abruptly during descent, often
as the diver arrives on the bottom and performs his last equalization maneuver.
However, the damage done by descent may not become apparent until the dive
is over. A common scenario is for the diver to rupture a damaged round window
while lifting heavy weights or having a bowel movement post dive. Both these
activities increase cerebrospinal fluid pressure and this pressure increase is trans­
mitted to the inner ear. The round window membrane, weakened by the trauma
suffered during descent, bulges into the middle ear space under the influence of the
increased cerebrospinal fluid pressure and ruptures.
All cases of suspected inner ear barotrauma should be referred to an ear, nose and
throat (ENT) physician as soon as possible. Treatment of inner ear barotrauma
ranges from bed rest with head elevation to exploratory surgery, depending on
the severity of the symptoms and whether a perilymph fistula is suspected. Any
hearing loss or vertigo occurring within 72 hours of a hyperbaric exposure should
be evaluated as a possible case of inner ear barotrauma.
When either hearing loss or vertigo develop after the diver has surfaced, it may
be impossible to tell whether the symptoms are caused by inner ear barotrauma,
decompression sickness or arterial gas embolism. For the latter two conditions,
recompression treatment is mandatory. Although it might be expected that
recompression treatment would further damage to the inner ear in a case of
barotrauma and should be avoided, experience has shown that recompression is
generally not harmful provided a few simple precautions are followed. The diver
should be placed in a head up position and compressed slowly to allow adequate
time for middle ear equalization. Clearing maneuvers should be gentle. The diver
should not be exposed to excessive positive or negative pressure when breathing

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3-29

oxygen on the built-in breathing system (BIBS) mask. Recompress the diver if
there is doubt about the cause of post-dive hearing loss or vertigo.
CAUTION

When in doubt, always recompress.

Frequent oscillations in middle ear pressure associated with difficult clearing may
lead to a transient vertigo. This condition is called alternobaric vertigo of descent.
Vertigo usually follows a Valsalva maneuver, often with the final clearing episode
just as the diver reaches the bottom. Symptoms typically last less than a minute but
can cause significant disorientation during that period. Descent should be halted
until the vertigo resolves. Once the vertigo resolves, the dive may be continued.
Alternobaric vertigo is a mild form of inner ear barotrauma in which no lasting
damage to the inner ear occurs.
3-7

MECHANICAL EFFECTS OF PRESSURE ON THE HUMAN BODY--BAROTRAUMA
DURING ASCENT

During ascent gases expand according to Boyle’s Law. If the excess gas is not
vented from enclosed spaces, damage to those spaces may result.
3-7.1

Middle Ear Overpressure (Reverse Middle Ear Squeeze). Expanding gas in the
middle ear space during ascent ordinarily vents out through the eustachian tube. If
the tube becomes blocked, pressure in the middle ear rela­tive to the external water
pressure increases. To relieve this pressure, the eardrum bows outward causing
pain. If the overpressure is significant, the eardrum may rupture. If rupture occurs,
the middle ear will equalize pressure with the surrounding water and the pain will
disappear. However, there may be a transient episode of intense vertigo as cold
water enters the middle ear space.

The increased pressure in the middle ear may also affect the inner ear balance
mechanism, leading to a condition called alternobaric vertigo of ascent. Alter­
nobaric vertigo occurs when the middle ear space on one side is overpressurized
while the other side is equalizing normally. The onset of vertigo is usually sudden
and may be preceded by pain in the ear that is not venting excess pressure. Alter­
nobaric vertigo usually lasts for only a few minutes, but may be incapacitating
during that time. Relief is usually abrupt and may be accompanied by a hissing
sound in the affected ear as it equalizes. Alternobaric vertigo during ascent will
disappear immediately if the diver halts his ascent and descends a few feet.
Increased pressure in the middle ear can also produce paralysis of the facial
muscles, a condition known as facial baroparesis. In some individuals, the facial
nerve is exposed to middle ear pressure as it traverses the temporal bone. If the
middle ear fails to vent during ascent, the overpressure can shut off the blood
supply to the nerve causing it to stop transmitting neural impulses to the facial
muscles on the affected side. Generally, a 10 to 30 min period of overpressure is
necessary for symptoms to occur. Full function of the facial muscles returns 5-10
min after the overpressure is relieved.

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Increased pressure in the middle ear can also cause structural damage to the inner
ear, a condition known as inner ear barotrauma of ascent. The bulging ear drum
pulls the oval window outward into the middle ear space through the action of the
middle ear bones. The round window correspondingly bulges inward. This inward
deflection can be enhanced if the diver further increases middle ear pressure by
performing a Valsalva maneuver. The round window may rupture causing inner
ear fluids to spill into the middle ear space. The symptoms of marked hearing loss
and sustained vertigo are identical to the symptoms experienced with inner ear
barotrauma during descent.
A diver who has a cold or is unable to equalize the ears is more likely to develop
reverse middle ear squeeze. There is no uniformly effective way to clear the ears
on ascent. Do not perform a Valsalva maneuver on ascent, as this will increase the
pressure in the middle ear, which is the direct opposite of what is required. The
Valsalva maneuver can also lead to the possibility of an arterial gas embolism.
If pain in the ear or vertigo develops on ascent, the diver should halt the ascent,
descend a few feet to relieve the symptoms and then continue his ascent at a slower
rate. Several such attempts may be necessary as the diver gradually works his way
to the surface. If symptoms of sustained hearing loss or vertigo appear during
ascent, or shortly after ascent, it may be impossible to tell whether the symptoms
are arising from inner ear barotrauma or from decompression sickness or arterial
gas embolism. Recompression therapy is indicated unless there is high confidence
that the condition is inner ear barotrauma.
3-7.2

Sinus Overpressure (Reverse Sinus Squeeze). Overpressure is caused when gas

is trapped within the sinus cavity. A fold in the sinus-lining membrane, a cyst, or
an outgrowth of the sinus membrane (polyp) may act as a check valve and prevent
gas from leaving the sinus during ascent. Sharp pain in the area of the affected
sinus results from the increased pressure. The pain is usually sufficient to stop
the diver from ascending. Pain is immediately relieved by descending a few feet.
From that point, the diver should titrate himself slowly to the surface in a series of
ascents and descents just as with a reverse middle ear squeeze.
When overpressure occurs in the maxillary sinus, the blood supply to the infraor­
bital nerve may be reduced, leading to numbness of the lower eyelid, upper lip,
side of the nose, and cheek on the affected side. This numbness will resolve spon­
taneously when the sinus overpressure is relieved.
3-7.3

Gastrointestinal Distention. Divers may occasionally experience abdominal

pain during ascent because of gas expansion in the stomach or intestines. This
condition is caused by gas being generated in the intestines during a dive, or by
swallowing air (aerophagia). These pockets of gas will usually work their way out
of the system through the mouth or anus. If not, distention will occur.
If the pain begins to pass the stage of mild discomfort, ascent should be halted and
the diver should descend slightly to relieve the pain. The diver should then attempt
to gently burp or release the gas anally. Overzealous attempts to belch should be

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3-31

avoided as they may result in swallowing more air. Abdominal pain following fast
ascents shall be evaluated by a Diving Medical Officer.
To avoid intestinal gas expansion:
„„ Do not dive with an upset stomach or bowel.
„„ Avoid eating foods that are likely to produce intestinal gas.
„„ Avoid a steep, head-down angle during descent to minimize the amount of air

swallowed.

Figure 3-10. Pulmonary Overinflation Syndromes (POIS). Leaking of gas into the pulmo­
nary interstitial tissue causes no symptoms unless further leaking occurs. If gas enters
the arterial circulation, potentially fatal arterial gas embolism may occur. Pneumothorax
occurs if gas accumulates between the lung and chest wall and if accumulation continues
without venting, then tension pneumothorax may result.

3-8

PULMONARY OVERINFLATION SYNDROMES

Pulmonary overinflation syndromes are a group of barotrauma-related diseases
caused by the expansion of gas trapped in the lung during ascent (reverse squeeze)
or overpressurization of the lung with subsequent overexpansion and rupture of
the alveolar air sacs. Excess pressure inside the lung can also occur when a diver
presses the purge button on a single-hose regulator while taking a breath. The two
main causes of alveolar rupture are:
„„ Excessive pressure inside the lung caused by positive pressure
„„ Failure of expanding gas to escape from the lung during ascent

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Figure 3-11. Arterial Gas Embolism.

Pulmonary overinflation from expanding gas failing to escape from the lung during
ascent can occur when a diver voluntarily or involuntarily holds his breath during
ascent. Localized pulmonary obstructions that can cause air trapping, such as
asthma or thick secretions from pneumonia or a severe cold, are other causes. The
conditions that bring about these incidents are different from those that produce lung
squeeze and they most frequently occur during free and buoyant ascent training or
emergency ascent from dives made with lightweight diving equipment or SCUBA.
The clinical manifestations of pulmonary overinflation depend on the location
where the free air collects. In all cases, the first step is rupture of the alveolus with
a collection of air in the lung tissues, a condition known as interstitial emphysema.
Interstitial emphysema causes no symptoms unless further distribution of the air
occurs. Gas may find its way into the chest cavity or arterial circulation. These
conditions are depicted in Figure 3‑10.
3-8.1

Arterial Gas Embolism (AGE). Arterial gas embolism (AGE), sometimes simply

called gas embolism, is an obstruction of blood flow caused by gas bubbles
(emboli) entering the arterial circulation. Obstruction of the arteries of the brain
and heart can lead to death if not promptly relieved (see Figure 3-11).

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3-33

3‑8.1.1

Causes of AGE. AGE is caused by the expansion of gas taken into the lungs while

breathing under pressure and held in the lungs during ascent. The gas might have
been retained in the lungs by choice (voluntary breathholding) or by accident
(blocked air passages), or by over pressurization of breathing gas. The gas could
have become trapped in an obstructed portion of the lung that has been damaged
from some previous disease or accident; or the diver, reacting with panic to a
difficult situation, may breathhold without realizing it. If there is enough gas and
if it expands sufficiently, the pressure will force gas through the alveolar walls
into surrounding tissues and into the bloodstream. If the gas enters the arterial
circulation, it will be dispersed to all organs of the body. The organs that are
especially susceptible to arterial gas embolism and that are respon­sible for the lifethreatening symptoms are the central nervous system (CNS) and the heart. In all
cases of arterial gas embolism, associated pneumothorax is possible and should not
be overlooked. Exhaustion of air supply and the need for an emer­gency ascent is
the most common cause of AGE.
3‑8.1.2

Symptoms of AGE
„„ Unconsciousness
„„ Paralysis
„„ Numbness
„„ Weakness
„„ Extreme fatigue
„„ Large areas of abnormal sensations (Paresthesias)
„„ Difficulty in thinking
„„ Vertigo
„„ Convulsions
„„ Vision abnormalities
„„ Loss of coordination
„„ Nausea and or vomiting
„„ Hearing abnormalities
„„ Sensation similar to that of a blow to the chest during ascent
„„ Bloody sputum
„„ Dizziness

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U.S. Navy Diving Manual — Volume 1

„„ Personality changes
„„ Loss of control of bodily functions
„„ Tremors

Symptoms of subcutaneous/medistinal emphysema, pneumothorax and/or pneu­
mopericardium may also be present (see below). In all cases of arterial gas
embolism, the possible presence of these associated conditions should not be
overlooked.
3‑8.1.3

Treatment of AGE.
„„ Basic first aid (ABC)
„„ 100 percent oxygen
„„ Immediate recompression
„„ See Volume 5 for more specific information regarding treatment.

3‑8.1.4

Prevention of AGE. The risk of arterial gas embolism can be substantially reduced

or eliminated by paying careful attention to the following:

„„ Every diver must receive intensive training in diving physics and physiology,

as well as instruction in the correct use of diving equipment. Particular attention
must be given to the training of SCUBA divers, because SCUBA operations
produce a comparatively high incidence of embolism accidents.

„„ A diver must never interrupt breathing during ascent from a dive in which

compressed gas has been breathed.

„„ A diver must exhale continuously while making an emergency ascent. The rate

of exhalation must match the rate of ascent. For a free ascent, where the diver
uses natural buoyancy to be carried toward the surface, the rate of exhalation
must be great enough to prevent embolism, but not so great that positive
buoyancy is lost. In a uncontrolled or buoyant ascent, where a life preserver,
dry suit or buoyancy compensator assists the diver, the rate of ascent may far
exceed that of a free ascent. The exhalation must begin before the ascent and
must be a strong, steady, and forceful. It is difficult for an untrained diver to
execute an emergency ascent properly. It is also often dangerous to train a diver
in the proper technique.

„„ The diver must not hesitate to report any ill­ness, especially respiratory illness

such as a cold, to the Diving Supervisor or Diving Medical Personnel prior to
diving.

CHAPTER 3 — Underwater Physiology and Diving Disorders

3-35

Figure 3-12. Mediastinal Emphysema.

3-8.2

Mediastinal and Subcutaneous Emphysema. Mediastinal emphysema, also called

pneumomediastinum, occurs when gas is forced through torn lung tissue into the
loose mediastinal tissues in the middle of the chest surrounding the heart, the
trachea, and the major blood vessels (see Figure 3-12). Subcutaneous emphysema
occurs when that gas subsequently migrates into the subcutaneous tissues of the
neck (Figure 3-13). Mediastinal emphysema is a pre-requisite for subcutaneous
emphysema.
3‑8.2.1

Causes of Mediastinal & Subcutaneous Emphysema. Mediastinal/subcutaneous

emphysema is caused by over inflation of the whole lung or parts of the lung due
to:
„„ Breath holding during ascent
„„ Positive pressure breathing such as ditch and don exercises
„„ Drown proofing exercises
„„ Cough during surface swimming

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Figure 3-13. Subcutaneous Emphysema.

3‑8.2.2

Symptoms of Mediastinal & Subcutaneous Emphysema. Mild cases are often

unnoticed by the diver. In more severe cases, the diver may experience mild to
moderate pain under the breastbone, often described as dull ache or feeling of
tightness. The pain may radiate to the shoulder or back and may increase upon
deep inspiration, coughing, or swallowing. The diver may have a feeling of fullness
around the neck and may have difficulty in swallowing. His voice may change in
pitch. An observer may note a swelling or apparent inflation of the diver’s neck.
Movement of the skin near the windpipe or about the collar bone may produce a
cracking or crunching sound (crepitation).
3‑8.2.3

Treatment of Mediastinal & Subcutaneous Emphysema. Suspicion of mediastinal
or subcutaneous emphysema warrants prompt referral to medical personnel to rule
out the coexistence of arterial gas embolism or pneu­mothorax. The latter two con­
ditions require more aggressive treatment. Treatment of mediastinal or subcutane­
ous emphysema with mild symptoms consists of breathing 100 percent oxygen
at the surface. If symptoms are severe, shallow recompression may be beneficial.
Recompression should only be carried out upon the recommendation of a Diving
Medical Officer who has ruled out the occurrence of pneumothorax. Recompres­
sion is performed with the diver breathing 100 percent oxygen and using the shal­
lowest depth of relief (usually 5 or 10 feet). An hour of breathing oxygen should

CHAPTER 3 — Underwater Physiology and Diving Disorders

3-37

Figure 3-14. Pneumothorax.

be sufficient for resolution, but longer stays may be necessary. Decompression
will be dictated by the tender’s decompression obli­gation. The appropriate air ta­
ble should be used, but the ascent rate should not exceed 1 foot per minute. In this
specific case, the delay in ascent should be included in bottom time when choosing
the proper decompression table.
3‑8.2.4

Prevention of Mediastinal & Subcutaneous Emphysema. The strategies for pre-

venting mediastinal/subcutaneous emphysema are identical to the strategies for
preventing arterial gas embolism. Breathe normally during ascent. If emergency
ascent is required, exhale continuously. Mediastinal/subcuta­neous emphysema is
particularly common after ditch and don exercises. Avoid positive pressure breathing
situations during such exercises. The mediastinal/subcutaneous emphysema that is
seen during drown proofing exercises and during surface swimming unfortunately
is largely unavoidable.
3-8.3

3‑8.3.1

3-38

Pneumothorax. A pneumothorax is air trapped in the pleural space between the
lung and the chest wall (Figure 3-14).
Causes of Pneumothorax. A pneumothorax occurs when the lung surface ruptures
and air spills into the space between the lung and chest wall. Lung rupture can
result from a severe blow to the chest or from overpressurization of the lung. In
its usual manifesta­tion, called a simple pneumothorax, a one-time leakage of air
from the lung into the chest partially collapses the lung, causing varying degrees

U.S. Navy Diving Manual — Volume 1

Organ
Shift
Heart

Figure 3-15. Tension Pneumothorax.

of respiratory distress. This condition normally improves with time as the air is
reabsorbed. In severe cases of collapse, the air must be removed with the aid of a
tube or catheter.
In certain instances, the damaged lung may allow air to enter but not exit the
pleural space. Successive breathing gradually enlarges the air pocket. This
is called a tension pneumothorax (Figure 3‑15) because of the progressively
increasing tension or pressure exerted on the lung and heart by the expanding gas.
If uncorrected, this force presses on the involved lung, causing it to completely
collapse. The lung, and then the heart, are pushed toward the opposite side of the
chest, which impairs both respiration and circulation.
A simple pneumothorax that occurs while the diver is at depth can be converted to
a tension pneumothorax by expansion of the gas pocket during ascent. Although a
ball valve like mechanism that allows air to enter the pleural cavity but not escape
is not present, the result is the same. The mounting tension collapses the lung on
the affected side and pushes the heart and lung to the opposite side of the chest.
3‑8.3.2

Symptoms of Pneumothorax. The onset of a simple pneumothorax is accompanied
by a sudden, sharp chest pain, followed by shortness of breath, labored breathing,
rapid heart rate, a weak pulse, and anxiety. The normal chest movements associated
with respiration may be reduced on the affected side and breath sounds may be
difficult to hear with a stethoscope.

CHAPTER 3 — Underwater Physiology and Diving Disorders

3-39

The symptoms of tension pneumothorax are similar to simple pneumothorax, but
become progressively more intense over time. As the heart and lungs are displaced
to the opposite side of the chest, blood pressure falls along with the arterial oxygen
partial pressure. Cyanosis (a bluish discoloration) of the skin appears. If left
untreated, shock and death will ensue. Tension pneumothorax is a true medical
emergency.
3‑8.3.3

Treatment of Pneumothorax. A diver believed to be suffering from pneumothorax

must be thoroughly examined for the possible co-existence of arterial gas embolism.
This is covered more fully in Volume 5.
A small pneumothorax (less than 15%) normally will improve with time as the
air in the pleural space is reabsorbed spontaneously. A larger pneumothorax
may require active treatment. Mild pneumothorax can be treated by breathing
100 percent oxygen. Cases of pneumothorax that demonstrate cardio-respiratory
compromise may require the insertion of a chest tube, largebore intravenous (IV)
catheter, or other device designed to remove intrathoracic gas (gas around the
lung). Only personnel trained in the use of these and the other accessory devices
(one-way valves, underwater suction, etc.) necessary to safety decompress the
thoracic cavity should insert them. Divers recompressed for treatment of arterial
gas embolism or decompression sickness, who also have a pneumothorax, will
experience relief upon recompression. A chest tube or other device with a oneway relief valve may need to be inserted at depth to prevent expansion of the
trapped gas during subsequent ascent. A tension pneumothorax should always be
suspected if the diver’s condition deteriorates rapidly during ascent, especially if
the symptoms are respiratory. If a tension pneumothorax is found, recompress to
depth of relief until the thoracic cavity can be properly vented. Pneumothorax,
if present in combination with arterial gas embolism or decompression sickness,
should not prevent immediate recompression therapy. However, a pneumothorax
may need to be vented as described before ascent from treatment depth. In cases of
tension pneumothorax, this procedure may be lifesaving.
3‑8.3.4

Prevention of Pneumothorax. The strategies for avoiding pneumothorax are the

same as those for avoiding arte­rial gas embolism. Breathe normally during ascent.
If forced to perform an emergency ascent, exhale continuously.
3-9

INDIRECT EFFECTS OF PRESSURE ON THE HUMAN BODY

The conditions previously described occur because of differences in pressure that
damage body structures in a direct, mechanical manner. The indirect or secondary
effects of pressure are the result of changes in the partial pressure of individual
gases in the diver’s breathing medium. The mechanisms of these effects include
saturation and desaturation of body tissues with dissolved gas and the modifica­tion
of body functions by abnormal gas partial pressures.
3-9.1

3-40

Nitrogen Narcosis. Nitrogen narcosis is the state of euphoria and exhilaration that
occurs when a diver breathes a gas mixture with a nitrogen partial pressure greater
than approximately 4 ata.

U.S. Navy Diving Manual — Volume 1

3‑9.1.1

Causes of Nitrogen Narcosis. Breathing nitrogen at high partial pressures has

a narcotic effect on the central nervous system that causes euphoria and impairs
the diver’s ability to think clearly. The narcotic effect begins at a nitrogen partial
pressure of approximately 4 ata and increases in severity as the partial pressure
is increased beyond that point. A nitrogen partial pressure of 8 ata causes very
marked impairment; partial pres­sures in excess of 10 ata may lead to hallucinations
and unconsciousness. For a dive on air, narcosis usually appears at a depth of
approximately 130 fsw, is very prominent at a depth of 200 fsw, and becomes
disabling at deeper depths.
There is a wide range of individual susceptibility to narcosis. There is also some
evidence that adaptation occurs on repeated exposures. Some divers, particularly
those experienced in deep operations with air, can often work as deep as 200 fsw
without serious difficulty. Others cannot.
3‑9.1.2

Symptoms of Nitrogen Narcosis. The symptoms of nitrogen narcosis include:
„„ Loss of judgment or skill
„„ A false feeling of well-being
„„ Lack of concern for job or safety
„„ Apparent stupidity
„„ Inappropriate laughter
„„ Tingling and vague numbness of the lips, gums, and legs

Disregard for personal safety is the greatest hazard of nitrogen narcosis. Divers
may display abnormal behavior such as removing the regulator mouthpiece or
swimming to unsafe depths without regard to decompression sickness or air supply.
3‑9.1.3

3‑9.1.4

Treatment of Nitrogen Narcosis. The treatment for nitrogen narcosis is to bring
the diver to a shallower depth where the effects are not felt. The narcotic effects
will rapidly dissipate during the ascent. There is no hangover associated with
nitrogen narcosis.
Prevention of Nitrogen Narcosis. Experienced and stable divers may be reasonably

productive and safe at depths where others fail. They are familiar with the extent to
which nitrogen narcosis impairs performance. They know that a strong conscious
effort to continue the dive requires unusual care, time, and effort to make even
the simplest observations and decisions. Any relaxation of conscious effort can
lead to failure or a fatal blunder. Experience, frequent exposure to deep diving,
and training may enable divers to perform air dives as deep as 180-200 fsw, but
novices and susceptible individuals should remain at shallower depths or dive with
helium-oxygen mixtures.

CHAPTER 3 — Underwater Physiology and Diving Disorders

3-41

Helium is widely used in mixed-gas diving as a substitute for nitrogen to prevent
narcosis. Helium has not demonstrated narcotic effects at any depth tested by
the U.S. Navy. Diving with helium-oxygen mixtures is the only way to prevent
nitrogen narcosis. Helium-oxygen mixtures should be considered for any dive in
excess of 150 fsw.
3-9.2

Oxygen Toxicity. Exposure to a partial pressure of oxygen above that encountered

in normal daily living may be toxic to the body. The extent of the toxicity is
dependent upon both the oxygen partial pressure and the exposure time. The higher
the partial pressure and the longer the exposure, the more severe the toxicity. The
two types of oxygen toxicity experienced by divers are pulmonary oxygen toxicity
and central nervous system (CNS) oxygen toxicity.

3‑9.2.1

Pulmonary Oxygen Toxicity. Pulmonary oxygen toxicity, sometimes called low

pressure oxygen poisoning, can occur whenever the oxygen partial pressure
exceeds 0.5 ata. A 12 hour exposure to a partial pressure of 1 ata will produce mild
symptoms and measurable decreases in lung function. The same effect will occur
with a 4 hour exposure at a partial pressure of 2 ata.
Long exposures to higher levels of oxygen, such as administered during Recom­
pression Treatment Tables 4, 7, and 8, may produce pulmonary oxygen toxicity.
The symptoms of pulmonary oxygen toxicity may begin with a burning sensation
on inspiration and progress to pain on inspiration. During recompression treat­
ments, pulmonary oxygen toxicity may have to be tolerated in patients with severe
neurological symptoms to effect adequate treatment. In conscious patients, the
pain and coughing experienced with inspiration eventually limit further exposure
to oxygen. Unconscious patients who receive oxygen treatments do not feel pain
and it is possible to subject them to exposures resulting in permanent lung damage
or pneumonia. For this reason, care must be taken when administering 100 percent
oxygen to unconscious patients even at surface pressure.
Return to normal pulmonary function gradually occurs after the exposure is termi­
nated. There is no specific treatment for pulmonary oxygen toxicity.

The only way to avoid pulmonary oxygen toxicity completely is to avoid the
long exposures to moderately elevated oxygen partial pressures that produce it.
However, there is a way of extending tolerance. If the oxygen exposure is period­
ically interrupted by a short period of time at low oxygen partial pressure, the total
exposure time needed to produce a given level of toxicity can be increased signifi­
cantly.
3‑9.2.2

3-42

Central Nervous System (CNS) Oxygen Toxicity. Central nervous system (CNS)
oxygen toxicity, sometimes called high pressure oxygen poisoning, can occur
whenever the oxygen partial pressure exceeds 1.3 ata in a wet diver or 2.4 ata in a
dry diver. The reason for the marked increase in susceptibility in a wet diver is not
completely understood. At partial pressures above the respective 1.3 ata wet and
2.4 ata dry thresholds, the risk of CNS toxicity is dependent on the oxygen partial
pressure and the exposure time. The higher the partial pressure and the longer the

U.S. Navy Diving Manual — Volume 1

exposure time, the more likely CNS symptoms will occur. This gives rise to partial
pressure of oxygen-exposure time limits for various types of diving.
3‑9.2.2.1

Factors Affecting the Risk of CNS Oxygen Toxicity. A number of factors are

known to influence the risk of CNS oxygen toxicity:

Individual Susceptibility. Susceptibility to CNS oxygen toxicity varies markedly
from person to person. Individual susceptibility also varies markedly from time to
time and for this reason divers may experience CNS oxygen toxicity at exposure
times and pressures previously tolerated. Individual variability makes it difficult to
set oxygen exposure limits that are both safe and practical.
CO2 Retention. Hypercapnia greatly increases the risk of CNS toxicity probably
through its effect on increasing brain blood flow and consequently brain oxygen
levels. Hypercapnia may result from an accumulation of CO2 in the inspired gas
or from inadequate ventilation of the lungs. The latter is usually due to increased
breathing resistance or a suppression of respiratory drive by high inspired ppO2.
Hypercapnia is most likely to occur on deep dives and in divers using closed and
semi-closed circuit rebreathers.
Exercise. Exercise greatly increases the risk of CNS toxicity, probably by increasing
the degree of CO2 retention. Exposure limits must be much more conservative for
exercising divers than for resting divers.
Immersion in Water. Immersion in water greatly increases the risk of CNS toxicity.
The precise mechanism for the big increase in risk over comparable dry chamber
exposures is unknown, but may involve a greater tendency for diver CO2 retention
during immersion. Exposure limits must be much more conservative for immersed
divers than for dry divers.
Depth. Increasing depth is associated with an increased risk of CNS toxicity even
though ppO2 may remain unchanged. This is the situation with UBAs that control
the oxygen partial pressure at a constant value, like the MK 16. The precise mech­
anism for this effect is unknown, but is probably more than just the increase in gas
density and concomitant CO2 retention. There is some evidence that the inert gas
component of the gas mixture accelerates the formation of damaging oxygen free
radicals. Exposure limits for mixed gas diving must be more conservative than for
pure oxygen diving.
Intermittent Exposure. Periodic interruption of high ppO2 exposure with a 5-15
min exposure to low ppO2 will reduce the risk of CNS toxicity and extend the total
allowable exposure time to high ppO2. This technique is most often employed in
hyperbaric treatments and surface decompression.
Because of these modifying influences, allowable oxygen exposure times vary
from situation to situation and from diving system to diving system. In general,
closed and semi-closed circuit rebreathing systems require the lowest partial pres­
sure limits, whereas surface-supplied open-circuit systems permit slightly higher

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limits. Allowable oxygen exposure limits for each system are discussed in later
chapters.
3‑9.2.2.2

Symptoms of CNS Oxygen Toxicity. The most serious direct consequence of

oxygen toxicity is convulsions. Some­times recognition of early symptoms may
provide sufficient warning to permit reduction in oxygen partial pressure and
prevent the onset of more serious symp­toms. The warning symptoms most often
encountered also may be remembered by the mnemonic VENTIDC:
V:

Visual symptoms. Tunnel vision, a decrease in diver’s peripheral vision, and
other symptoms, such as blurred vision, may occur.

E:

Ear symptoms. Tinnitus, any sound perceived by the ears but not resulting
from an external stimulus, may resemble bells ringing, roaring, or a
machinery-like pulsing sound.

N:

Nausea or spasmodic vomiting. These symptoms may be intermittent.

T:

Twitching and tingling symptoms. Any of the small facial muscles, lips, or
muscles of the extremities may be affected. These are the most frequent and
clearest symptoms.

I:

Irritability. Any change in the diver’s mental status including confusion,
agitation, and anxiety.

D:

Dizziness. Symptoms include clumsiness, incoordination, and unusual
fatigue.

C:

Convulsions. The first sign of CNS oxygen toxicity may be convulsions that
occur with little or no warning.

Warning symptoms may not always appear and most are not exclusively symp­toms
of oxygen toxicity. Muscle twitching is perhaps the clearest warning, but it may
occur late, if at all. If any of these warning symptoms occur, the diver should take
immediate action to lower the oxygen partial pressure.
A convulsion, the most serious direct consequence of CNS oxygen toxicity, may
occur suddenly without being preceded by any other symptom. During a convul­
sion, the individual loses consciousness and his brain sends out uncontrolled nerve
impulses to his muscles. At the height of the seizure, all of the muscles are stimu­
lated at once and lock the body into a state of rigidity. This is referred to as the
tonic phase of the convulsion. The brain soon fatigues and the number of impulses
slows. This is the clonic phase and the random impulses to various muscles may
cause violent thrashing and jerking for a minute or so.
After the convulsive phase, brain activity is depressed and a postconvulsive
(postictal) depression follows. During this phase, the patient is usually uncon­
scious and quiet for a while, then semiconscious and very restless. He will then
usually sleep on and off, waking up occasionally though still not fully rational. The

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U.S. Navy Diving Manual — Volume 1

depression phase sometimes lasts as little as 15 minutes, but an hour or more is not
uncommon. At the end of this phase, the patient often becomes suddenly alert and
complains of no more than fatigue, muscular soreness, and possibly a headache.
After an oxygen-toxicity convulsion, the diver usually remembers clearly the
events up to the moment when consciousness was lost, but remembers nothing of
the convulsion itself and little of the postictal phase.
3‑9.2.2.3

Treatment of CNS Oxygen Toxicity. A diver who experiences the warning
symptoms of oxygen toxicity shall inform the Diving Supervisor immediately. The
following actions can be taken to lower the oxygen partial pressure:
„„ Ascend
„„ Shift to a breathing mixture with a lower oxygen percentage
„„ In a recompression chamber, remove the mask.

WARNING

Reducing the oxygen partial pressure does not instantaneously reverse
the biochemical changes in the central nervous system caused by high
oxygen partial pressures. If one of the early symptoms of oxygen toxicity
occurs, the diver may still convulse up to a minute or two after being
removed from the high oxygen breathing gas. One should not assume
that an oxygen convulsion will not occur unless the diver has been off
oxygen for 2 or 3 minutes.

Despite its rather alarming appearance, the convulsion itself is usually not much
more than a strenuous muscular workout for the victim. The possible danger of
hypoxia during breathholding in the tonic phase is greatly reduced because of
the high partial pressure of oxygen in the tissues and brain. If a diver convulses,
the UBA should be ventilated immediately with a gas of lower oxygen content,
if possible. If depth control is possible and the gas supply is secure (helmet or
full face mask), the diver should be kept at depth until the convulsion subsides
and normal breathing resumes. If an ascent must take place, it should be done as
slowly as possible to reduce the risk of an arterial gas embolism. AGE should be
considered in any diver surfacing unconscious due to an oxygen convulsion.
If the convulsion occurs in a recompression chamber, it is important to keep the
individual from thrashing against hard objects and being injured. Complete restraint
of the individual’s movements is neither necessary nor desirable. The oxygen mask
shall be removed immediately. It is not necessary to force the mouth open to insert
a bite block while a convulsion is taking place. After the convulsion subsides and
the mouth relaxes, keep the jaw up and forward to maintain a clear airway until the
diver regains consciousness. Breathing almost invariably resumes spontaneously.
Management of CNS oxygen toxicity during recompression therapy is discussed
fully in Volume 5.
If a convulsing diver is prevented from drowning or causing other injury to himself,
full recovery with no lasting effects can be expected within 24 hours. Susceptibility
to oxygen toxicity does not increase as a result of a convulsion, although divers

CHAPTER 3 — Underwater Physiology and Diving Disorders

3-45

may be more inclined to notice warning symptoms during subse­quent exposures
to oxygen.
3‑9.2.2.4

Prevention of CNS Oxygen Toxicity. The actual mechanism of CNS oxygen

toxicity remains unknown in spite of many theories and much research. Preventing
oxygen toxicity is important to divers. When use of high pressures of oxygen is
advantageous or necessary, divers should take sensible precautions, such as being
sure the breathing apparatus is in good order, observing depth-time limits, avoiding
excessive exertion, and heeding abnormal symptoms that may appear. Interruption
of oxygen breathing with peri­odic “air” breaks can extend the exposure time to
high oxygen partial pressures significantly. Air breaks are routinely incorporated
into recompression treatment tables and some decompression tables.
3-9.3

3‑9.3.1

Decompression Sickness (DCS). A diver’s blood and tissues absorb additional
nitrogen (or helium) from the lungs when at depth. If a diver ascends too fast this
excess gas will separate from solu­tion and form bubbles. These bubbles produce
mechanical and biochemical effects that lead to a condition known as decompression sickness.
Absorption and Elimination of Inert Gases. The average human body at sea level

contains about 1 liter of nitrogen. All of the body tissues are saturated with nitro­
gen at a partial pressure equal to the partial pressure in the alveoli, about 0.79 ata.
If the partial pressure of nitrogen changes because of a change in the pressure or
composition of the breathing mixture, the pressure of the nitrogen dissolved in
the body gradually attains a matching level. Additional quantities of nitrogen are
absorbed or eliminated, depending on the partial pressure gradient, until the partial
pressure of the gas in the lungs and in the tissues is equal. If a diver breathes he­
lium, a similar process occurs.
As described by Henry’s Law, the amount of gas that dissolves in a liquid is almost
directly proportional to the partial pressure of the gas. If one liter of inert gas is
absorbed at a pressure of one atmosphere, then two liters are absorbed at two atmo­
spheres and three liters at three atmospheres, etc.
The process of taking up more inert gas is called absorption or saturation. The pro­
cess of giving up inert gas is called elimination or desaturation. The chain of events
is essentially the same in both processes even though the direction of exchange is
opposite.

Shading in diagram (Figure 3‑16) indicates saturation with nitrogen or helium un­
der increased pressure. Blood becomes saturated on passing through lungs, and
tissues are saturated in turn via blood. Those with a large supply (as in A above) are
saturated much more rapidly than those with poor blood supply (C) or an unusually
large capacity for gas, as fatty tissues have for nitrogen. In very abrupt ascent from
depth, bubbles may form in arterial blood or in “fast” tissue (A) even through the

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U.S. Navy Diving Manual — Volume 1

SATURATION OF TISSUES
Lung
Capillary
Bed

Venous Return
Right
Heart
Pump

A

B

C

Arterial Supply

Left
Heart
Pump

Lung
Capillary
Bed

Venous Return
Right
Heart
Pump

Left
Heart
Pump

A

B

C

Arterial Supply

Figure 3-16. Saturation of Tissues. Shading in diagram indicates saturation with nitrogen
or helium under increased pressure. Blood becomes saturated on passing through lungs,
and tissues are saturated in turn via blood. Those with a large supply (as in A above) are
saturated much more rapidly than those with poor blood supply (C) or an unusually large
capacity for gas, as fatty tissues have for nitrogen. In very abrupt ascent from depth,
bubbles may form in arterial blood or in “fast” tissue (A) even through the body as a whole
is far from saturation. If enough time elapses at depth, all tissues will become equally
saturated, as shown in lower diagram.

body as a whole is far from saturation. If enough time elapses at depth, all tissues
will become equally saturated, as shown in lower diagram.
3‑9.3.1.1

Saturation of Tissues. The sequence of events in the process of saturation can be

illustrated by consid­ering what happens in the body of a diver taken rapidly from
the surface to a depth of 100 fsw (Figure 3‑16). To simplify matters, we can say
that the partial pressure of nitrogen in his blood and tissues on leaving the surface
is roughly 0.8 ata. When the diver reaches 100 fsw, the alveolar nitrogen pressure
in his lungs will be about 0.8 × 4 ata = 3.2 ata, while the blood and tissues remain
temporarily at 0.8 ata. The partial pressure difference or gradient between the al­
veolar air and the blood and tissues is thus 3.2 minus 0.8, or 2.4 ata. This gradient
is the driving force that makes the molecules of nitrogen move by diffusion from
one place to another. Consider the following 10 events and factors in the diver at
100 fsw:
1. As blood passes through the alveolar capillaries, nitrogen molecules move from

the alveolar air into the blood. By the time the blood leaves the lungs, it has reached
equilibrium with the new alveolar nitrogen pressure. It now has a nitrogen tension

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3-47

(partial pressure) of 3.2 ata and contains about four times as much nitrogen as
before. When this blood reaches the tissues, there is a similar gradient and nitrogen
molecules move from the blood into the tissues until equilibrium is reached.
2. The volume of blood in a tissue is relatively small compared to the volume of the

tissue and the blood can carry only a limited amount of nitrogen. Because of this,
the volume of blood that reaches a tissue over a short period of time loses its excess
nitrogen to the tissue without greatly increasing the tissue nitrogen pressure.

3. When the blood leaves the tissue, the venous blood nitrogen pressure is equal to

the new tissue nitrogen pressure. When this blood goes through the lungs, it again
reaches equilibrium at 3.2 ata.

4. When the blood returns to the tissue, it again loses nitrogen until a new equilibrium

is reached.

5. As the tissue nitrogen pressure rises, the blood-tissue gradient decreases, slowing

the rate of nitrogen exchange. The rate at which the tissue nitrogen partial pres­
sure increases, therefore, slows as the process proceeds. However, each volume
of blood that reaches the tissue gives up some nitrogen which increases the tissue
partial pressure until complete saturation, in this case at 3.2 ata of nitrogen, is
reached.

6. Tissues that have a large blood supply in proportion to their own volume have

more nitrogen delivered to them in a certain amount of time and therefore approach
complete saturation more rapidly than tissues that have a poor blood supply.

7. All body tissues are composed of lean and fatty components. If a tissue has an

unusually large capacity for nitrogen, it takes the blood longer to deliver enough
nitrogen to saturate it completely. Nitrogen is about five times as soluble (capable
of being dissolved) in fat as in water. Therefore, fatty tissues require much more
nitrogen and much more time to saturate them completely than lean (watery)
tissues do, even if the blood supply is ample. Adipose tissue (fat) has a poor blood
supply and therefore saturates very slowly.

8. At 100 fsw, the diver’s blood continues to take up more nitrogen in the lungs and

to deliver more nitrogen to tissues, until all tissues have reached saturation at a
pressure of 3.2 ata of nitrogen. A few watery tissues that have an excellent blood
supply will be almost completely saturated in a few minutes. Others, like fat with
a poor blood supply, may not be completely saturated unless the diver is kept at
100 fsw for 72 hours or longer.

9. If kept at a depth of 100 fsw until saturation is complete, the diver’s body contains

about four times as much nitrogen as it did at the surface. Divers of average size
and fatness have about one liter of dissolved nitrogen at the surface and about
four liters at 100 fsw. Because fat holds about five times as much nitrogen as lean
tissues, much of a diver’s nitrogen content is in his fatty tissue.

10. An important fact about nitrogen saturation is that the process requires the same

length of time regardless of the nitrogen pressure involved. For example, if the

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DESATURATION OF TISSUES
Lung
Capillary
Bed

Venous Return
Right
Heart
Pump

A

B

C

Arterial Supply

Left
Heart
Pump

Lung
Capillary
Bed

Venous Return
Right
Heart
Pump

Left
Heart
Pump

A

B

C

Arterial Supply

Figure 3-17. Desaturation of Tissues. The desaturation process is essentially the reverse
of saturation. When pressure of inert gas is lowered, blood is cleared of excess gas as
it goes through the lungs. Blood then removes gas from the tissues at rates depending
on amount of blood that flows through them each minute. Tissues with poor blood supply
(as in C in upper sketch) or large gas capacity will lag behind and may remain partially
saturated after others have cleared (see lower diagram).

diver had been taken to 33 fsw instead of 100, it would have taken just as long to
saturate him completely and to bring his nitrogen pressures to equilibrium. In this
case, the original gradient between alveolar air and the tissues would have been
only 0.8 ata instead of 2.4 ata. Because of this, the amount of nitrogen delivered
to tissues by each round of blood circulation would have been smaller from the
beginning. Less nitrogen would have to be delivered to saturate him at 33 fsw, but
the slower rate of delivery would cause the total time required to be the same.

When any other inert gas, such as helium, is used in the breathing mixture, the
body tissues become saturated with that gas in the same process as for nitrogen.
However, the time required to reach saturation is different for each gas. This is
because the blood and tissue solubilities are different for the different inert gases.
Helium, for example, is much less soluble in fat than nitrogen is.
3‑9.3.1.2

Desaturation of Tissues. The process of desaturation is the reverse of saturation

(Figure 3‑17). If the partial pressure of the inert gas in the lungs is reduced, either
through a reduction in the diver’s depth or a change in the breathing medium, the
new pressure gradient induces the nitrogen to diffuse from the tissues to the blood,
from the blood to the gas in the lungs, and then out of the body with the expired
breath. Some parts of the body desaturate more slowly than others for the same

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reason that they saturate more slowly: poor blood supply or a greater capacity
to store inert gas. Washout of excess inert gas from these “slow” tissues will lag
behind washout from the faster tissues.
3‑9.3.2

Bubble Formation. Inert gas may separate from physical solution and form bub­

bles if the partial pres­sure of the inert gas in blood and tissues exceeds the ambient
pressure by more than a critical amount. During descent and while the diver is on
the bottom, blood and tissue inert gas partial pressures increase significantly as
tissue saturation takes place, but the inert gas pressure always remains less than
the ambient pres­sure surrounding the diver. Bubbles cannot form in this situation.
During ascent the converse is true. Blood and tissue inert gas pressures fall as the
tissues desatu­rate, but blood and tissue inert gas pressures can exceed the ambient
pressure if the rate of ascent is faster than the rate at which tissues can equilibrate.
Consider an air diver fully saturated with nitrogen at a depth of 100 fsw. All body
tissues have a nitrogen partial pressure of 3.2 ata. If the diver were to quickly as­
cend to the surface, the ambient pressure surrounding his tissues would be reduced
to 1 ata. Assuming that ascent was fast enough not to allow for any tissue desatura­
tion, the nitrogen pressure in all the tissues would be 2.2 ata greater than the ambi­
ent pres­sure (3.2 ata - 1 ata). Under this circumstance bubbles can form.
Bubble formation can be avoided if the ascent is controlled in such a way that the
tissue inert gas pressure never exceeds the ambient pressure by more than the crit­
ical amount. This critical amount, called the allowable supersaturation, varies from
tissue to tissue and from one inert gas to another. A decompression table shows the
time that must be spent at various decompression stops on the way to the surface
to allow each tissue to desaturate to the point where its allowable supersaturation
is not exceeded.
3‑9.3.3

Direct Bubble Effects. Bubbles forming in the tissues (autochthonous bubbles)

and in the bloodstream (circulating bubbles) may exert their effects directly in
several ways:

„„ Autochthonous bubbles can put pressure on nerve endings, stretch and tear

tissue leading to hemorrhage, and increase pressure in the tissue leading to
slowing or cessation of incoming blood flow. These are thought to be the
primary mechanisms for injury in Spinal Cord, Musculoskeletal, and Inner Ear
DCS.

„„ Venous bubbles can partially or completely block the veins draining various

organs leading to reduced organ blood flow (venous obstruction). Venous
obstruction in turn leads to tissue hypoxia, cell injury and death. This is one of
the secondary mechanisms of injury in Spinal Cord DCS.

„„ Venous bubbles carried to the lung as emboli (called venous gas emboli or

VGE) can partially block the flow of blood through the lung leading to fluid
build up (pulmonary edema) and decreased gas exchange. The result is systemic
hypoxia and hypercarbia. This is the mechanism of damage in Pulmonary DCS.

„„ Arterial bubbles can act as emboli blocking the blood supply of almost any

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tissue leading to hypoxia, cell injury and death. Arterial gas embolism and
autochotonous bubble formation are thought be the primary mechanisms of
injury in Cerebral (brain) DCS.
The damage done by the direct bubble effect occurs within a relatively short
period of time (a few minutes to hours). The primary treatment for these effects
is recompression. Recompression will compress the bubble to a smaller diameter,
restore blood flow, decrease venous congestion, and improve gas exchange in
the lungs and tissues. It also increases the speed at which the bubbles outgas and
collapse.
3‑9.3.4

Indirect Bubble Effects. Bubbles may also exert their effects indirectly because a

bubble acts like a foreign body. The body reacts as it would if there were a cinder
in the eye or a splinter in the hand. The body’s defense mechanisms become alerted
and try to eliminate the foreign body. Typical reactions include:

„„ Blood vessels become “leaky” due to damage to the endothelial lining cells and

chemical release. Blood plasma leaks out while blood cells remain inside. The
blood becomes thick and more difficult to pump. Organ blood flow is reduced.

„„ The platelet system becomes active and the platelets gather at the site of the

bubble causing a clot to form.

„„ The injured tissue releases fats that clump together in the bloodstream. These

fat clumps act as emboli, causing tissue hypoxia.

„„ Injured tissues release histamine and histamine-like substances, causing edema,

which leads to allergic-type problems of shock and respiratory distress.

Indirect bubble effects take place over a longer period of time than the direct
bubble effects. Because the non-compressible clot replaces a compressible bubble,
recompression alone is not enough. To restore blood flow and relieve hypoxia,
hyperbaric treatment and other therapies are often required.
3‑9.3.5

Symptoms of Decompression Sickness. Decompression sickness is generally

divided into two categories. Type I decom­
pression sickness involves the
skin, lymphatic system, muscles and joints and is not life threatening. Type II
decompression sickness (also called serious decom­pression sickness) involves the
nervous system, respiratory system, or circulatory system. Type II decompression
sickness may become life threatening. Because the treatment of Type I and Type
II decompression sickness may be different, it is important to distinguish between
these two types. Symptoms of Type I and Type II decompression sickness may be
present at the same time.
When the skin is involved, the symptoms are itching or burning usually accompa­
nied by a rash. Involvement of the lymphatic system produces swelling of regional
lymph nodes or an extremity. Involvement of the musculoskeletal system produces
pain, which in some cases can be excruciating. Bubble formation in the brain can
produce blindness, dizziness, paralysis and even unconsciousness and convulsion.

CHAPTER 3 — Underwater Physiology and Diving Disorders

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When the spinal cord is involved, paralysis and/or loss of feeling occur. Bubbles
in the inner ear produce hearing loss and vertigo. Bubbles in the lungs can cause
coughing, shortness of breath, and hypoxia, a condition referred to as “the chokes.”
This condition may prove fatal. A large number of bubbles in the circula­tion can
lead to cardiovascular collapse and death. Unusual fatigue or exhaustion after a
dive is probably due to bubbles in unusual locations and the biochemical changes
they have induced. While not attributable to a specific organ system, unusual
fatigue is a definite symptom of decompression sickness.
3‑9.3.5.1

Time Course of Symptoms. Decompression sickness usually occurs after surfacing.

If the dive is particularly arduous or decompression has been omitted, however, the
diver may experience decompression sickness before reaching the surface.

After surfacing, there is a latency period before symptoms appear. This may be as
short as several minutes to as long as several days. Long, shallow dives are gener­
ally associated with longer latencies than deep, short dives. For most dives, the
onset of decompression sickness can be expected within several hours of surfacing.
3‑9.3.6

3‑9.3.7

Treating Decompression Sickness. Treatment of decompression sickness is
accomplished by recompression. This involves putting the victim back under
pressure to reduce the size of the bubbles to cause them to go back into solution and
to supply extra oxygen to the hypoxic tissues. Treatment is done in a recompression
chamber, but can sometimes be accomplished in the water if a chamber cannot
be reached in a reasonable period of time. Recompression in the water is not
recommended, but if undertaken, must be done following specified procedures.
Further discussion of the symptoms of decompression sickness and a complete
discussion of treatment are presented in Volume 5.
Preventing Decompression Sickness. Prevention of decompression sickness

is generally accomplished by following the decompression tables. However,
individual susceptibility or unusual conditions, either in the diver or in connection
with the dive, produces a small percentage of cases even when proper dive
procedures are followed meticulously. To be abso­lutely free of decompression
sickness under all possible circumstances, the decompression time specified would
have to be far in excess of that normally needed. On the other hand, under ideal
circumstances, some individuals can ascend safely in less time than the tables
specify. This must not be taken to mean that the tables contain an unnecessarily
large safety factor. The tables represent the minimum workable decompression
time that permits average divers to surface safely from normal working dives
without an unacceptable incidence of decom­pression sickness.
3-10

THERMAL PROBLEMS IN DIVING

The human body functions effectively within a relatively narrow range of internal
temperature. The average, or normal, core temperature of 98.6°F (37°C) is main­
tained by natural mechanisms of the body, aided by artificial measures such as the
use of protective clothing or environmental conditioning when external conditions
tend toward cold or hot extremes.

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U.S. Navy Diving Manual — Volume 1

Thermal problems, arising from exposure to various temperatures of water, pose
a major consideration when planning operational dives and selecting equipment.
Bottom time may be limited more by a diver’s intolerance to heat or cold than his
exposure to increased oxygen partial pressures or the amount of decompression
required.
The diver’s thermal status affects the rate of inert gas uptake and elimination.
Divers who are warm on the bottom will absorb more inert gas than divers who
are cold. No-decompression dives in warm water, therefore, may carry a greater
risk of DCS than comparable dives in cold water. Given identical exposures on the
bottom, divers who are warm during decompression stops will lose more inert gas
and have a lower risk of DCS than divers who are cold.
3-10.1

Regulating Body Temperature. The metabolic processes of the body constantly

generate heat. If heat is allowed to build up inside the body, damage to the cells can
occur. To maintain internal temperature at the proper level, the body must lose heat
equal to the amount it produces.
Heat transfer is accomplished in several ways. The blood, while circulating through
the body, picks up excess heat and carries it to the lungs, where some of it is lost
with the exhaled breath. Heat is also transferred to the surface of the skin, where
much of it is dissipated through a combination of conduction, convection, and
radiation. Moisture released by the sweat glands cools the surface of the body as it
evaporates and speeds the transfer of heat from the blood to the surrounding air. If
the body is working hard and generating greater than normal quantities of heat, the
blood vessels nearest the skin dilate to permit more of the heated blood to reach the
body surfaces, and the sweat glands increase their activity.

Maintaining proper body temperature is particularly difficult for a diver working
underwater. The principal temperature control problem encountered by divers is
keeping the body warm. The high thermal conductivity of water, coupled with
the normally cool-to-cold waters in which divers operate, can result in rapid and
excessive heat loss.
3-10.2

Excessive Heat Loss (Hypothermia). Hypothermia is a lowering of the core

temperature of the body. Immersion hypoth­ermia is a potential hazard whenever
diving operations take place in cool to cold waters. A diver’s response to
immersion in cold water depends on the degree of thermal protection worn and
water temperature. A water temperature of approxi­mately 91°F (33°C) is required
to keep an unprotected, resting man at a stable temperature. The unprotected diver
will be affected by excessive heat loss and become chilled within a short period of
time in water temperatures below 72°F (23°C).
3‑10.2.1

Causes of Hypothermia. Hypothermia in diving occurs when the difference

between the water and body temperature is large enough for the body to lose
more heat than it produces. Exer­cise normally increases heat production and body
temperature in dry conditions. Paradoxically, exercise in cold water may cause
the body temperature to fall more rapidly. Any movement that stirs the water in
contact with the skin creates turbu­lence that carries off heat (convection). Heat loss
CHAPTER 3 — Underwater Physiology and Diving Disorders

3-53

is caused not only by convection at the limbs, but also by increased blood flow into
the limbs during exercise. Continual movement causes the limbs to resemble the
internal body core rather than the insulating superficial layer. These two conflicting
effects result in the core temperature being maintained or increased in warm water
and decreased in cold water.
3‑10.2.2

Symptoms of Hypothermia. In mild cases, the victim will experience uncontrolled

shivering, slurred speech, imbalance, and/or poor judgment. Severe cases of
hypothermia are characterized by loss of shivering, impaired mental status,
irregular heartbeat, and/or very shallow pulse or respirations. This is a medical
emergency. The signs and symp­toms of falling core temperature are given in Table
3‑1, though individual responses to falling core temperature will vary. At extremely
low temperatures or with prolonged immersion, body heat loss reaches a point at
which death occurs.
Table 3‑1. Signs and Symptoms of Dropping Core Temperature.
Core Temperature
°F
°C

3‑10.2.3

Symptoms

98

37

Cold sensations, skin vasoconstriction, increased muscle tension,
increased oxygen consumption

97

36

Sporadic shivering suppressed by voluntary movements, gross
shivering in bouts, further increase in oxygen consumption,
uncontrollable shivering

95

35

Voluntary tolerance limit in laboratory experiments, mental
confusion, impairment of rational thought, possible drowning,
decreased will to struggle

93

34

Loss of memory, speech impairment, sensory function impairment,
motor performance impairment

91

33

Hallucinations, delusions, partial loss of consciousness, shivering
impaired

90

32

Heart rhythm irregularities, motor performance grossly impaired

88

31

Shivering stopped, failure to recognize familiar people

86

30

Muscles rigid, no response to pain

84

29

Loss of consciousness

80

27

Ventricular fibrillation (ineffective heartbeat), muscles flaccid

79

26

Death

Treatment of Hypothermia. To treat mild hypothermia, passive and active
rewarming measures may be used and should be continued until the victim is
sweating. Rewarming techniques include:

Passive:
„„ Remove all wet clothing.

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„„ Wrap victim in a blanket (preferably wool).
„„ Place in an area protected from wind.
„„ If possible, place in a warm area (i.e. galley).

Active:
„„ Warm shower or bath.
„„ Place in a very warm space (i.e., engine room).

To treat severe hypothermia avoid any exercise, keep the victim lying down,
initiate only passive rewarming, and immediately transport to the nearest medical
treatment facility.
CAUTION

Do not institute active rewarming with severe cases of hypothermia.

WARNING

CPR should not be initiated on a severely hypothermic diver unless it can
be determined that the heart has stopped or is in ventricular fibrillation.
CPR should not be initiated in a patient that is breathing.

3‑10.2.4

Prevention of Hypothermia. The body’s ability to tolerate cold environments is

due to natural insulation and a built-in means of heat regulation. Temperature is
not uniform throughout the body. It is more accurate to consider the body in terms
of an inner core where a constant or uniform temperature prevails and a superficial
region through which a tempera­ture gradient exists from the core to the body
surface. Over the trunk of the body, the thickness of the superficial layer may be
1 inch (2.5 cm). The extremities become a superficial insulating layer when their
blood flow is reduced to protect the core.
Once in the water, heat loss through the superficial layer is lessened by the reduc­tion
of blood flow to the skin. The automatic, cold-induced vasoconstriction (narrowing
of the blood vessels) lowers the heat conductance of the superficial layer and acts
to maintain the heat of the body core. Unfortunately, vasoconstric­tive regulation of
heat loss has only a narrow range of protection. When the extremities are initially
put into very cold water, vasoconstriction occurs and the blood flow is reduced to
preserve body heat. After a short time, the blood flow increases and fluctuates up
and down for as long as the extremities are in cold water. As circulation and heat
loss increase, the body temperature falls and may continue falling, even though
heat production is increased by shivering.
Much of the heat loss in the trunk area is transferred over the short distance from
the deep organs to the body surface by physical conduction, which is not under any
physiological control. Most of the heat lost from the body in moderately cold water
is from the trunk and not the limbs.
Hypothermia can be insidious and cause problems without the diver being aware
of it. The diver should wear appropriate thermal protection based upon the water
temperature and expected bottom time (See Chapter 6). Appropriate dress can

CHAPTER 3 — Underwater Physiology and Diving Disorders

3-55

greatly reduce the effects of heat loss and a diver with proper dress can work in
very cold water for reasonable periods of time. Acclimatization, adequate hydra­
tion, experience, and common sense all play a role in preventing hypothermia.
Provide the diver and topside personnel adequate shelter from the elements.
Adequate predive hydration is essential.
Heat loss through the respiratory tract becomes an increasingly significant factor
in deeper diving. Inhaled gases are heated in the upper respiratory tract and more
energy is required to heat the denser gases encountered at depth. In fact, a severe
respiratory insult can develop if a diver breathes unheated gas while making a deep
saturation dive in cold water. Respiratory gas heating is required in such situations.
3-10.3

Other Physiological Effects of Exposure to Cold Water. In addition to hypothermia,

other responses to exposure to cold water create poten­tial hazards for the diver.
3‑10.3.1

3‑10.3.2

3‑10.3.3

Caloric Vertigo. The eardrum does not have to rupture for caloric vertigo to occur.
Caloric vertigo can occur simply as the result of having water enter the external ear
canal on one side but not the other. The usual cause is a tight fitting wet suit hood
that allows cold water access to one ear, but not the other. It can also occur when
one external canal is obstructed by wax. Caloric vertigo may occur suddenly upon
entering cold water or when passing through thermoclines. The effect is usually
short lived, but while present may cause significant disorientation and nausea.
Diving Reflex. Sudden exposure of the face to cold water or immersion of the whole
body in cold water may cause an immediate slowing of the heart rate (bradycardia)
and intense constriction of the peripheral blood vessels. Sometimes abnormal
heart rhythms accompany the bradycardia. This response is known as the diving
reflex. Removing or losing a facemask in cold water can trigger the diving reflex.
It is still not known whether cardiac arrhythmias associated with the diving reflex
contribute to diving casualties. Until this issue is resolved, it is prudent for divers
to closely monitor each other when changing rigs underwater or buddy breathing.
Uncontrolled Hyperventilation. If a diver with little or no thermal protection is

suddenly plunged into very cold water, the effects are immediate and disabling.
The diver gasps and his respiratory rate and tidal volume increase. His breathing
becomes so rapid and uncontrolled that he cannot coordinate his breathing and
swimming movements. The lack of breathing control makes survival in rough
water very unlikely.

3-10.4

3‑10.4.1

Excessive Heat Gain (Hyperthermia). Hyperthermia is a raising of the core
temperature of the body. Hyperthermia should be considered a potential risk
any time air temperature exceeds 90°F or water temperature is above 82°F. An
individual is considered to have developed hyperthermia when core temperature
rises 1.8°F (1°C) above normal (98.6°F, 37°C). The body core temperature should
not exceed 102.2°F (39°C). By the time the diver’s core temperature approaches
102°F noticeable mental confusion may be present.
Causes of Hyperthermia. Divers are susceptible to hyperthermia when they are

unable to dissipate their body heat. This may result from high water temperatures,
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protective garments, rate of work, and the duration of the dive. Predive heat
exposure may lead to signifi­cant dehydration and put the diver at greater risk of
hyperthermia.
3‑10.4.2

Symptoms of Hyperthermia. Signs and symptoms of hyperthermia can vary among
individuals. Since a diver might have been in water that may not be considered
hot, support personnel must not rely solely on classical signs and symptoms of
heat stress for land exposures. Table 3‑2 lists commonly encountered signs and
symptoms of heat stress in diving. In severe cases of hyperthermia (severe heat
exhaustion or heat stroke), the victim will experience disorientation, tremors, loss
of consciousness and/or seizures.
Table 3‑2. Signs of Heat Stress.
Least Severe

High breathing rate
Feeling of being hot, uncomfortable
Low urine output
Inability to think clearly
Fatigue
Light-headedness or headache
Nausea
Muscle cramps
Sudden rapid increase in pulse rate
Disorientation, confusion
Exhaustion
Collapse

Most Severe

3‑10.4.3

Death

Treatment of Hyperthermia. The treatment of all cases of hyperthermia shall

include cooling of the victim to reduce the core temperature. In mild to moderate
hyperthermia cooling should be started immediately by removing the victim’s
clothing, spraying him with a fine mist of lukewarm-to-cool water, and then fanning.
This causes a large increase in evaporative cooling. Avoid whole body immersion
in cold water or packing the body in ice as this will cause vasoconstriction which
will decrease skin blood flow and may slow the loss of heat. Ice packs to the neck,
armpit or groin may be used. Oral fluid replacement should begin as soon as the
victim can drink and continue until he has urinated pale to clear urine several
times. If the symptoms do not improve, the victim shall be transported to a medical
treatment facility.

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3-57

Severe hyperthermia is a medical emergency. Cooling measures shall be started
and the victim shall be transported immediately to a medical treatment facility.
Intravenous fluids should be administered during transport.
3‑10.4.4

Prevention of Hyperthermia. Acclimatization, adequate hydration, experience, and

common sense all play a role in preventing hyperthermia. Shelter personnel from
the sun and keep the amount of clothing worn to a minimum. Adequate predive
hydration is essential. Alcohol or caffeine beverages should be avoided since they
can produce dehydra­tion. Medications containing antihistamines or aspirin should
not be used in warm water diving. Physically fit individuals and those with lower
levels of body fat are less likely to develop hyperthermia. Guidelines for diving in
warm water are contained in Chapter 6.
Acclimatization is the process where repeated exposures to heat will reduce
(but not eliminate) the rise in core temperature. At least 5 consecutive days of
acclima­tization to warm water diving are needed to see an increased tolerance
to heat. Exercise training is essential for acclimation to heat. Where possible,
acclimatiza­tion should be completed before attempting long duration working
dives. Acclimatization should begin with short exposures and light workloads. All
support personnel should also be heat acclimatized. Fully acclimatized divers can
still develop hyperthermia, however. Benefits of acclimatization begin to disap­pear
in 3 to 5 days after stopping exposure to warm water.
3-11

SPECIAL MEDICAL PROBLEMS ASSOCIATED WITH DEEP DIVING
3-11.1

High Pressure Nervous Syndrome (HPNS). High Pressure Nervous Syndrome

(HPNS) is a derangement of central nervous system function that occurs during
deep helium-oxygen dives, particularly satura­tion dives. The cause is unknown. The
clinical manifestations include nausea, fine tremor, imbalance, incoordination, loss
of manual dexterity, and loss of alertness. Abdominal cramps and diarrhea develop
occasionally. In severe cases a diver may develop vertigo, extreme indifference
to his surroundings and marked confusion such as inability to tell the right hand
from the left hand. HPNS is first noted between 400 and 500 fsw and the severity
appears to be both depth and compres­sion rate dependent. With slow compression,
depth of 1000 fsw may be achieved with relative freedom from HPNS. Beyond
1000 fsw, some HPNS may be present regardless of the compression rate. Attempts
to block the appearance of the syndrome have included the addition of nitrogen
or hydrogen to the breathing mixture and the use of various drugs. No method
appears to be entirely satisfactory.
3-11.2

3-58

Compression Arthralgia. Most divers will experience pain in the joints during

compression on deep dives. This condition is called compression arthralgia.
The shoulders, knees, writs, and hips are the joints most commonly affected.
The fingers, lower back, neck, and ribs may also be involved. The pain may be a
constant deep ache similar to Type I decompression sickness, or a sudden, sharp,
and intense but short-lived pain brought on my movement of the joint. These pains
may be accompanied by “popping” or “cracking” of joints or a dry “gritty” feeling
within the joint.

U.S. Navy Diving Manual — Volume 1

The incidence and intensity of compression arthralgia symptoms are dependent on
the depth of the dive, the rate of compression, and individual susceptibility. While
primarily a problem of deep saturation diving, mild symptoms may occur with
rapid compression on air or helium-oxygen dives as shallow as 100 fsw. In deep
helium saturation dives with slower compression rates, symptoms of compression
arthralgia usually begins between 200 and 300 fsw, and increase in intensity as
deeper depths are attained. Deeper than 600 fsw, compression pain may occur even
with extremely slow rates of compression.
Compression joint pain may be severe enough to limit diver activity, travel rate, and
depths attainable during downward excursion dives from saturation. Improve­ment
is generally noted during the days spent at the saturation depth but, on occasion,
these pains may last well into the decompression phase of the dive until shallower
depths are reached. Compression pain can be distinguished from decompression
sickness pain because it was present before decompression was started and does
not increase in intensity with decreasing depth.
The mechanism of compression pain is unknown, but is thought to result from the
sudden increase in inert gas tension surrounding the joints causing fluid shifts that
interfere with joint lubrication.
3-12

OTHER DIVING MEDICAL PROBLEMS
3-12.1

Dehydration. Dehydration is a concern to divers, particularly in tropical zones. It is

defined as an excessive loss of water from the body tissues and is accompanied by a
distur­bance in the balance of essential electrolytes, particularly sodium, potassium,
and chloride.
3‑12.1.1

Causes of Dehydration. Dehydration usually results from inadequate fluid intake

and/or excessive perspi­ration in hot climates. Unless adequate attention is paid
to hydration, there is a significant chance the diver in a hot climate will enter the
water in a dehydrated state.
Immersion in water creates a special situation that can lead to dehydration in its
own right. The water pressure almost exactly counterbalances the hydrostatic pres­
sure gradient that exists from head to toe in the circulatory system. As a result,
blood which is normally pooled in the leg veins is translocated to the chest, causing
an increase central blood volume. The body mistakenly interprets the increase
in central blood as a fluid excess. A reflex is triggered leading to an increase in
urination, a condition called immersion diuresis. The increased urine flow leads to
steady loss of water from the body and a concomitant reduction in blood volume
during the dive. The effects of immersion diuresis are felt when the diver leaves
the water. Blood pools once again in the leg veins. Because total blood volume is
reduced, central blood volume falls dramatically. The heart may have difficulty
getting enough blood to pump. The diver may experience light­headness or faint
while attempting to climb out of the water on a ladder or while standing on the
stage. This is the result of a drop in blood pressure as the blood volume shifts to the
legs. More commonly the diver will feel fatigued, less alert, and less able to think
clearly than normal. His exercise tolerance will be reduced.
CHAPTER 3 — Underwater Physiology and Diving Disorders

3-59

3‑12.1.2

Preventing Dehydration. Dehydration is felt to increase the risk of decompression

sickness. Divers should monitor their fluid intake and urine output during diving
operations to insure that they keep themselves well hydrated. During the dive
itself, there is nothing one can do to block the effects of immersion diuresis. Upon
surfacing they should rehydrate themselves as soon as the opportunity presents
itself.
3-12.2

Immersion Pulmonary Edema. Immersion in water can cause fluid to leak out of

the circulation system and accu­mulate first in the interstitial tissues of the lungs
then in the alveoli themselves. This condition is called immersion pulmonary
edema. The exact mechanism of injury is not know, but the condition is probably
related to the increase in central blood volume that occurs during immersion (see
description above). Contributing factors include immersion in cold water, negative
pressure breathing, and overhy­dration pre-dive, all of which enhance the increase
in central blood volume with immersion. Heavy exercise is also a contributor.
Symptoms may begin on the bottom, during ascent, or shortly after surfacing and
consist primarily of cough and shortness of breath. The diver may cough up blood
tinged mucus. Chest pain is notably absent. A chest x-ray shows the classic pattern
of pulmonary edema seen in heart failure.

A diver with immersion pulmonary edema should be placed on surface oxygen and
transported immediately to a medical treatment facility. Signs and symptoms will
usually resolve spontaneously over 24 hours with just bed rest and 100% oxygen.
Immersion pulmonary edema is a relatively rare condition, but the incidence
appears to be increasing perhaps because of an over-emphasis on the need to
hydrate before a dive. Adequate pre-dive hydration is essential, but overhydration
is to be avoided. Beyond avoiding overhydration and negative pressure breathing
situations, there is nothing the diver can do to prevent immersion pulmonary
edema.
3-12.3

Carotid Sinus Reflex. External pressure on the carotid artery from a tight fitting

neck dam, wet suit, or dry suit can activate receptors in the arterial wall, causing
a decrease in heart rate with possible loss of consciousness. Using an extra-tightfitting dry or wet suit or tight neck dams to decrease water leaks increase the
chances of activation of the carotid reflex and the potential for problems.
3-12.4

Middle Ear Oxygen Absorption Syndrome. Middle ear oxygen absorption

syndrome refers to the negative pressure that may develop in the middle ear
following a long oxygen dive. Gas with a very high percentage of oxygen enters
the middle ear cavity during an oxygen dive. Following the dive, the tissues of
the middle ear slowly absorb the oxygen. If the eustachian tube does not open
spontaneously, a negative pressure relative to ambient may result in the middle ear
cavity. Symptoms are often noted the morning after a long oxygen dive. Middle
ear oxygen absorption syndrome is difficult to avoid but usually does not pose a
significant problem because symp­toms are generally minor and easily eliminated.
There may also be fluid (serous otitis media) present in the middle ear as a result of
the differential pressure.
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3‑12.4.1

Symptoms of Middle Ear Oxygen Absorption Syndrome. The diver may notice

mild discomfort and hearing loss in one or both ears. There may also be a sense of
pressure and a moist, cracking sensation as a result of fluid in the middle ear.

3‑12.4.2

Treating Middle Ear Oxygen Absorption Syndrome. Equalizing the pressure in the

middle ear using a normal Valsalva maneuver or the diver’s procedure of choice,
such as swallowing or yawning, will usually relieve the symptoms. Discomfort
and hearing loss resolve quickly, but the middle ear fluid is absorbed more slowly.
If symptoms persist, a Diving Medical Technician or Diving Medical Officer shall
be consulted.

3-12.5

3-12.6

Underwater Trauma. Underwater trauma is different from trauma that occurs at
the surface because it may be complicated by the loss of the diver’s gas supply
and by the diver’s decompression obligation. If possible, injured divers should be
surfaced immedi­ately and treated appropriately. If an injured diver is trapped, the
first priority is to ensure sufficient breathing gas is available, then to stabilize the
injury. At that point, a decision must be made as to whether surfacing is possible.
If the decom­pression obligation is great, the injury will have to be stabilized until
sufficient decompression can be accomplished. If an injured diver must be surfaced
with missed decompression, the diver must be treated as soon as possible, realizing
that the possible injury from decompression sickness may be as severe or more
severe than that from the other injuries.
Blast Injury. Divers frequently work with explosive material or are involved in

combat swim­ming and therefore may be subject to the hazards of underwater
explosions. An explosion is the violent expansion of a substance caused by the
gases released during rapid combustion. One effect of an explosion is a shock wave
that travels outward from the center, somewhat like the spread of ripples produced
by drop­ping a stone into a pool of water. This shock wave moving through the
surrounding medium (whether air or water) passes along some of the force of the
blast.
A shock wave moves more quickly and is more pronounced in water than in air
because of the relative incompressibility of liquids. Because the human body is
mostly water and incompressible, an underwater shock wave passes through the
body with little or no damage to the solid tissues. However, the air spaces of the
body, even though they may be in pressure balance with the ambient pressure, do
not readily transmit the overpressure of the shock wave. As a result, the tissues
that line the air spaces are subject to a violent fragmenting force at the interface
between the tissues and the gas.
The amount of damage to the body is influenced by a number of factors. These
include the size of the explosion, the distance from the site, and the type of explo­
sive (because of the difference in the way the expansion progresses in different
types of explosives). In general, larger, closer, and slower-developing explosions
are more hazardous. The depth of water and the type of bottom (which can reflect
and amplify the shock wave) may also have an effect. Under average conditions, a
shock wave of 500 psi or greater will cause injury to the lungs and intestinal tract.

CHAPTER 3 — Underwater Physiology and Diving Disorders

3-61

The extent of injury is also determined in part by the degree to which the diver’s
body is submerged. For an underwater blast, any part of the body that is out of
the water is not affected. Conversely, for an air blast, greater depth provides more
protection. The maximum shock pressure to which a diver should be exposed is 50
psi. The safest and recommended procedure is to have all divers leave the water if
an underwater explosion is planned or anticipated. A diver who anticipates a nearby
underwater explosion should try to get all or as much of his body as possible out
of the water. If in the water, the diver’s best course of action is to float face up,
presenting the thicker tissues of the back to the explosion.
3-12.7

Otitis Externa. Otitis externa (swimmer’s ear) is an infection of the ear canal caused
by repeated immersion. The water in which the dive is being performed does not
have to be contaminated with bacteria for otitis externa to occur. The first symptom
of otitis externa is an itching and/or wet feeling in the affected ear. This feeling
will progress to local pain as the external ear canal becomes swollen and inflamed.
Local lymph nodes (glands) may enlarge, making jaw movement painful. Fever
may occur in severe cases. Once otitis externa develops, the diver should discon­
tinue diving and be examined and treated by Diving Medical Personnel.

Unless preventive measures are taken, otitis externa is very likely to occur during
diving operations, causing unnecessary discomfort and restriction from diving.
External ear prophylaxis, a technique to prevent swimmer’s ear, should be done
each morning, after each wet dive, and each evening during diving operations.
External ear prophylaxis is accomplished using a 2 percent acetic acid in aluminum
acetate (e.g., Otic Domboro) solution. The head is tilted to one side and the
external ear canal gently filled with the solution, which must remain in the canal
for 5 minutes. The head is then tilted to the other side, the solution allowed to run
out and the procedure repeated for the other ear. The 5-minute duration shall be
timed with a watch. If the solution does not remain in the ear a full 5 minutes, the
effectiveness of the procedure is greatly reduced.
During prolonged diving operations, the external ear canal may become occluded
with wax (cerumen). When this happens, external ear prophylaxis is ineffective and
the occurrence of otitis externa will become more likely. The external ear canal can
be examined periodically with an otoscope to detect the presence of ear wax. If the
eardrum cannot be seen during examination, the ear canal should be flushed gently
with water, dilute hydrogen peroxide, or sodium bicarbonate solu­tions to remove
the excess cerumen. Never use swabs or other instruments to remove cerumen;
this is to be done only by trained medical personnel. Otitis externa is a particular
problem in saturation diving if divers do not adhere to prophylactic measures.

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3-12.8

Hypoglycemia. Hypoglycemia is an abnormally low blood sugar (glucose) level.

Episodes of hypoglycemia are common in diabetics and pre-diabetics, but may
also occur in normal individuals. Simply missing a meal tends to reduce blood
sugar levels. A few individuals who are otherwise in good health will develop
some degree of hypoglycemia if they do not eat frequently. Severe exercise on an
empty stomach will occasionally bring on symptoms even in an individual who
ordinarily has no abnormality in this respect.
Symptoms of hypoglycemia include unusual hunger, excessive sweating, numb­
ness, chills, headache, trembling, dizziness, confusion, incoordination, anxiety,
and in severe cases, loss of consciousness.

If hypoglycemia is present, giving sugar by mouth relieves the symptoms promptly
and proves the diagnosis. If the victim is unconscious, glucose should be given
intravenously.
The possibility of hypoglycemia increases during long, drawn out diving opera­
tions. Personnel have a tendency to skip meals or eat haphazardly during the
operation. For this reason, attention to proper nutrition is required. Prior to long,
cold, arduous dives, divers should be encouraged to load up on carbohydrates. For
more information, see Naval Medical Research Institute (NMRI) Report 89-94.
3-12.9

Use of Medications while Diving. There are no hard and fast rules for deciding

when a medication would preclude a diver from diving. In general, topical
medications, antibiotics, birth control medication, and decongestants that do not
cause drowsiness would not restrict diving. Diving medical personnel should be
consulted to determine if any drugs preclude diving.

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PAGE LEFT BLANK INTENTIONALLY

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U.S. Navy Diving Manual — Volume 1

CHAPTER 4

Dive Systems
4-1

INTRODUCTION
4-1.1

Purpose. The purpose of this chapter is to promulgate general policy for

maintaining diving equipment and systems.

4-1.2

Scope. This chapter provides general guidance applicable to maintaining all

diving equipment and diving systems. Detailed procedures for maintaining diving
equipment and systems are found in applicable military and manufacturer’s
operating and maintenance (O&M) manuals and Planned Maintenance System
(PMS) Maintenance Requirement Cards (MRC).

4-1.3

References.

Authorized for Military Use Program. NAVSEAINST 10560.2 (series).
U.S. Navy Diving and Manned Hyperbaric System Safety Certification Manual.
SS52-­AA-MAN-010.
Compressed Air, Breathing. FED SPEC BB­A­1034 Grade A.
Oxygen, Aviators Breathing. MIL-PRF-27210H.
Respirable Helium, Type I Gaseous Grade B. MIL-PRF-27407D.
Nitrogen, High Purity, Special Purpose. MIL-PRF-27401 Grade B Type 1.
Navy Diving Program. OPNAVINST 3150.27 (series).
Shipboard Gauge Calibration Program. NAVSEAINST 4734.1 (series).
Industrial Gases, Generating, Handling and Storage, NAVSEA Technical Manual
S9086­SX­STM­000/CH­550.
American and Canadian Standard Compressed-Gas Cylinder Valve Outlet and
Inlet Connections (ANSI­B57.1 and CSA­B96).
American National Standard Method of Marking Portable Compressed-Gas
Containers to Identify the Material Contained (Z48.1).
Guide to the Preparation of Precautionary Labeling and Marking of Compressed
Gas Cylinders (CGA Pamphlet C­7).
OPNAV 4790 (series) Ship’s Maintenance and Material Management (3-M)

CHAPTER 4 — Dive Systems

4-1

4-2

GENERAL INFORMATION
4-2.1

Document Precedence. If a conflict arises between documents containing diving

equipment and systems maintenance procedures:

1. PMS/MRC and supporting system drawings take precedence.
2. If PMS/MRC is inadequate or incorrect, the applicable military O&M manual

takes precedence. Report inadequate or incorrect PMS via a PMS feedback report
in accordance with current PMS instructions.

3. If PMS/MRC and applicable military O&M manual are inadequate or incorrect,

the manufacturer’s technical manual takes precedence. Report inadequate or
incorrect military technical manual information in accordance with procedures in
the affected technical manual.

NOTE

For OEM technical manuals that are found to be deficient, contact
NAVSEA 00C3 for guidance.

Contact the applicable certification authority prior to disregarding any required
maintenance procedures on certified diving equipment. Failure to do so may
compromise certification.
4-2.2

Authorization For Navy Use (ANU). Equipment used to conduct diving operations
shall be authorized for use by NAVSEA/00C in accordance with NAVSEAINST
10560.2 (series) or hold a current NAVSEA or NAVFAC system safety
certification. ANU diving equipment shall be used in the as tested configuration
(e.g., SCUBA first and second stage regulator of different manufacturers shall not
be interchanged).

Diving and related equipment authorized for military use is listed on NAVSEA/
00C ANU list and may be found on http://www.supsalv.org website. Director of
Diving Programs (Code 00C3) is the cognizant authority for the NAVSEA/00C
ANU list. Refer to the common access card (CAC) enabled secure SUPSALV
website (https://secure.supsalv.org) to provide feedback to the ANU program
manager. For a complete description of the ANU program refer to NAVSEAINST
10560.2 (series):
The ANU list addresses two categories of equipment.
n Category I. Life support diving equipment that provides a safe, controlled
environment for a diver by satisfying life support requirements of the intended
diving operation.
n Category II. Non-life support equipment which enhances the mission capability
and is not essential for diver life support.
Surface supplied diving systems, hyperbaric chamber systems, and select underwater
breathing apparatus (e.g., MK-16, MK-25) shall be certified in accordance with

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U.S. Navy Diving and Manned Hyperbaric System Safety Certification Manual
(SS521-AA-MAN-010).
4-2.3

System Certification Authority (SCA). NAVSEA 00C Code 00C4 is SCA for all

afloat and portable diving and hyperbaric systems. Naval Facilities Engineering
Command Code OFP-­
SCA is SCA for all shore­
based diving and hyperbaric
systems. Naval Sea Systems Command Code 07Q is SCA for deep submergence
systems.
4-2.4

Planned Maintenance System. Diving equipment shall be maintained in

accordance with the applicable PMS package. Failure to maintain equipment in
accordance with current PMS guidance reduces the equipment reliability and may
void the system safety certification for certified systems.

NOTE

Only white virgin Teflon tape that is made in accordance with MILSPEC
A-A 58093 is authorized for use on Navy Dive Life Support Systems
(DLSS).

NOTE

Only use properly mixed Non Ionic Detergent (NID) to clean exterior
DLSS. Do not flood console case or gauges with water and cleaner.

4-2.5

Alteration of Diving Equipment. Diving equipment shall not be modified or altered

from approved configuration unless prior approval has been granted in accordance
with OPNAVINST 3150.27 (series).

4‑2.5.1

Diving Equipment and Systems Program Managers. Program managers are

responsible for the development, acquisition, and fielding of diving equipment and
systems. The following offices manage the systems and equipment listed:
n All fixed shore based systems - NAVFAC (OFP-SCA)
n All portable and afloat diving equipment and systems (except as noted below)
- NAVSEASYSCOM (SEA 00C3)
n MK 16 MOD 1 and the Fly Away Recompression Chamber (FARCC) NAVSEASYSCOM (PMS-408)
n MK 25 - NAVSEASYSCOM (PMS 340)

4-2.6

Operating and Emergency Procedures. Operating procedures (OPs) are detailed
check sheets for operating the diving system. All diving and recompression
chamber systems shall be operated in accordance with NAVSEA or NAVFAC
approved operating procedures and Emergency Procedures (EPs).

Dive systems are aligned, secured, or modified in a step by step fashion IAW the
OP and two person integrity. One person reads the steps and the other performs the
action.

CHAPTER 4 — Dive Systems

4-3

The operator executing the procedure shall perform the required action, and the
second operator shall initial that it was performed. Any material condition issue
(loose handwheels, missing tags, or labels, etc.) shall be indicated in the remarks
section at the end of the OP, and a check placed in the “note” column for the step
to which it applies, indicating that a remark has been made.
Emergency procedures are memorized and immediate actions are executed when
required. The emergency procedure is then verified from the written procedures
after the immediate action to resolve the emergency is complete.
4‑2.6.1

Standard Dive Systems/Equipment. Standard diving equipment such as the MK

3 Light Weight Diving System (LWDS), Transportable Recompression Chamber
System (TRCS), and the MK 16 and MK 25 Underwater Breathing Apparatus
shall be operated per a single set of standard OP/EPs that are included as part of
the system O&M Manual or on the 00C website.
Proposed changes/updates to OP/EPs for standardized diving equipment shall be
submitted as a formal change proposal to the respective technical program manager.
4‑2.6.2

Non-Standard Systems. Non-standard dive systems and recompression chambers
shall be operated in accordance with a single set of standard OPs/EPs that are
developed at the command level and approved for use after validation by
NAVSEA 00C3 or NAVFAC OFP-SCA. Proposed changes/updates to OPs/EPs
shall be submitted to the applicable approval authority. The following addresses
are provided to assist in submitting proposed OP/EP changes and updates:

COMNAVSEASYSCOM (Code 00C3)
1333 Isaac Hull Ave., SE
Washington Navy Yard, DC 20376-1070
COMNAVFACENGCOM (OFP-SCA)
1322 Patterson Ave., SE
Suite 1000
Washington Navy Yard, DC 20374-5065
4‑2.6.3

OP/EP Approval Process. Submission of OPs/EPs for approval (if required)

must precede the requested on-site survey date by 90 calendar days. Follow these
procedures when submitting OPs/EPs for approval:

n The command shall validate in the forwarding letter that the OPs/EPs are
complete and accurate.
n The command must verify that drawings are accurate. Accurate drawings are
used as a guide for evaluating OPs/EPs. Fully verified system schematics/
drawings with components, gas consoles, manifolds, and valves clearly labeled
shall be forwarded with the OPs/EPs.
n Approved OPs/EPs shall have the revision date listed on each page and not
have any changes without written NAVSEA/NAVFAC approval.
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n The command shall retain system documentation pertaining to DLSS approval,
i.e., PSOBs, supporting manufacturing documentation, and OPs/EPs.
4‑2.6.4

Format. The format for OPs/EPs is as follows:

n System: (Name or description, consistent with drawings)
n Step, Component, Description, Procedure, Location, Initials, Note (read in
seven columns)
4‑2.6.5

Example. System: High Pressure Air
Step

Component

Description

Procedure

Location

1

ALP-15

Reducer
Outlet

Open

Salvage Hold

2

ALP-GA-7

Reducer
Outlet

Record
Pressiure

Salvage Hold

Initials

Note

Once NAVSEA or NAVFAC has approved the system OPs/EPs, they shall not be
changed without specific written approval from NAVSEA or NAVFAC.
4-3

DIVER’S BREATHING GAS PURITY STANDARDS
4-3.1

Diver’s Breathing Air. Diver’s air shall meet the U.S. Navy’s Diving Breathing Air

Standards contained in Table 4-1.

Table 4‑1. U.S. Navy Diving Breathing Air Requirements.
Constituent

Specification

Percent Oxygen, Balance Predominately Nitrogen

20–22%

Carbon Dioxide (ppm)

1,000 ppm (max)

Carbon Monoxide (ppm)

10 ppm (max)

Odor and taste

Not objectionable

Water (Notes 1,2)
by dew point (degrees F at 1 ATM ABS) or
by moisture content (ppm or mg/L)

-65°F
24 ppm or .019 mg/L (max)

Total Volatile Organic Compounds (in methane
equivalents), ppm (Notes 3, 4, 5)

25 ppm (max)

Condensed Oil and other Particulates, mg/L

0.005 mg/L or 5 mg/m3 (max)

CHAPTER 4 — Dive Systems

4-5

Constituent

Specification

Notes:
1.	The water content of compressed air can vary with the intended use from saturated to very
dry. For breathing air used in conjunction with a U.S. Navy Diving Life Support System
(DLSS) in a cold environment (<50°F), where moisture can condense and freeze causing
system malfunction, the verification of the dew point is paramount and shall not exceed
-65°F or 10°F lower than the coldest temperature expected in the area, whichever is lower.
2.	Dew points of -40°F are acceptable for submarine diver life support systems, including
the Dry Deck Shelter (DDS), the VA Class Lockout Trunk (LOT), and the SSGN Lockout
Compartment (LOC).
3.	Specification is 25 ppm in methane equivalents when measured by a laboratory-based
flame ionization detector (FID) calibrated with methane and methane excluded.
4.	Specification is 5 ppm in n-hexane equivalents when measured by a laboratory-based (FID)
calibrated with n-hexane and methane excluded.
5.	Specification is 10 ppm as measured by other portable photoionization detector (PID)
containing a 10.6 electron volt lamp and calibrated with isobutylene (includes GEOTECH
Dive Air 2 Portable Air Monitor).

Diver’s breathing air may be produced by a certified air compressor, ANU approved
air compressor or procured from a commercial or foreign military source. Diver’s
air procured from a commercial or foreign military source shall be certified in
writing by the vendor as meeting the purity standards listed in Table 4-1.
U.S. Military air compressors used to produce diver’s breathing air shall be listed
on the ANU list or be part of a certified system. In addition, they shall be maintained
in accordance with the PMS card(s) applicable to the compressor and air samples
shall be in accordance with paragraph 4-4.
NOTE:

A compressor log shall be maintained with the compressor at all times.
It shall record date, start/stop hour-meter readings, corrective/preventive
maintenance accomplished, the component the compressor is charging,
pressures not within parameters.

Air generated by non-U.S. Navy owned compressors (commercially supplied air)
may be utilized for all diving operations with the Commanding Officer’s permission
when the commercial air supplier provides documentation that the air meets the
requirements of Table 4-1.
When a commercial air supplier is unable to provide documentation that air meets
the air purity standards of Table 4-1 the Commanding Officer may authorize use
of the commercial air for an individual mission, not to exceed 30 days, utilizing
DP surface augmented diving apparatus or SCUBA in water 38 degrees F and
above. The air source shall be evaluated against the requirements of the Non-Navy
Compressors Check Sheet. The compressor check sheet is available on the secure
SUPSALV website at 00C3/diving publications.
4-3.2

Diver’s Breathing Oxygen. Oxygen used for breathing at 100-percent concentra­

tions and for mixing of diver’s breathing gases shall meet Military Specification
MIL-PRF-27210G, Oxygen, Aviators Breathing, Liquid and Gaseous. The purity
standards are contained in Table 4-2.

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Table 4‑2. Diver’s Compressed Oxygen Breathing Purity Requirements.
Specification

Constituent

General Note: Gaseous and liquid oxygen shall contain not less than 99.5% by volume. The
remain­der, except for moisture and minor constituents specified below, shall be Argon and Ni­
trogen.
Type I Gaseous
Oxygen (percent by volume)

99.5%

Carbon dioxide (by volume)

10 ppm (max)

Methane (CH4 by volume)

50 ppm (max)

Acetylene (C2H2)

0.1 ppm (max)

Ethylene (C2H4)

0.4 ppm (max)

Ethane (C2H6 and other hydrocarbons)

6.0 ppm (max)

Nitrous Oxide (N2O by volume)

4.0 ppm (max)

Halogenated Compounds (by volume):
Refrigerants

2.0 ppm (max)

Solvents

0.2 ppm (max)

Moisture (water vapor measured by ppm or
measured by dew point)

7 ppm (max)
<-82°F

Odor

Odor free

Type II Liquid
Oxygen (percent by volume)

99.5%

Carbon dioxide (by volume)

5 ppm (max)

Methane (CH4 by volume)

25 ppm (max)

Acetylene (C2H2)

0.05 ppm (max)

Ethylene (C2H4)

0.2 ppm (max)

Ethane (C2H6 and other hydrocarbons)

3.0 ppm (max)

Nitrous Oxide (N2O by volume)

2.0 ppm (max)

Halogenated Compounds (by volume):
Refrigerants

1.0 ppm (max)

Solvents

0.10 ppm (max)

Moisture (water vapor measured by ppm or
measured by dew point)

7 ppm (max)
<-82°F

Odor

Odor free

Reference: Military Specification MIL-PRF-27210G

4-3.3

Diver’s Breathing Helium. Helium used for diver’s breathing gas shall meet
Military Specification, MIL-PRF-27407D Propellant Pressurizing Agent Helium,
Type I Gaseous Grade B, Respirable Helium. The purity standards are contained
in Table 4-3.

CHAPTER 4 — Dive Systems

4-7

Table 4‑3. Diver’s Compressed Helium Breathing Purity Requirements.
Constituent

Specification

Helium (percent by volume)

99.997%

Moisture (water vapor)

9 ppm (max)

Dew Point (not greater than)

-78°F

Hydrocarbons (as Methane)

1 ppm (max)

Oxygen

3 ppm (max)

Nitrogen + Argon

5 ppm (max)

Neon

23 ppm (max)

Hydrogen

1 ppm (max)

Reference: Military Specification MIL-PRF-27407D

4-3.4

Diver’s Breathing Nitrogen. Nitrogen used for divers breathing gas shall meet
Federal Specification A-A-59155 Nitrogen, High Purity, Special Purpose. The
purity standards are contained in Table 4-4.
Table 4‑4. Diver’s Compressed Nitrogen Breathing Purity Requirements.
Class I Oil Free, Type I Gaseous & Type II Liquid
Specification/Grade
Constituent

A

B

Nitrogen

99.95%

99.50%

Oxygen

0.05%

0.50%

Moisture (water vapor)

.02 mg/l

.02 mg/l

Total Hydrocarbons
(as meth­ane by volume)

50 ppm

50 ppm

Oil

Oil Free

Oil Free

None

None

Odor

Note: Type I Nitrogen shall not contain any solid particles whose dimensions are greater than
50 microns. A 10 micron or better nominal filter at or close to the cylinder charging manifold will
be used.
Reference: Federal Specification A-A-59155

4-4

DIVER’S AIR SAMPLING PROGRAM

NAVSEA Code 00C3 manages, but does not fund, the diver’s breathing air sampling
program in accor­dance with OPNAVINST 3150.27 (series). The purpose of the air
sampling program is to:
n Provide technical support for the operation and maintenance of diver’s breathing
air compressors and diving air storage systems.

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n Provide general guidance concerning use of the Defense Compressed Air
Sampling (DCAT) program that establishes standards for testing facilities.
n Provide guidance and assistance for qualifying local commercial air analysis
facilities, including the evaluation of air sampling capabilities and equipment.
n Perform program management for centrally funded air sampling services as
directed by CNO Code N97 and coordinate support at the echelon II or III level
for diving commands use of the DCAT program.
n Collaborate with other government agencies and commercial industry on gas
purity standards and sampling procedures related to diver’s breathing gases.
4-4.1

Sampling Requirements. Periodic air samples are required in accordance with
PMS applicable to the compressor producing diver’s breathing air. Each diver
breathing­air source in service must be sampled approximately every 6 months
(within the interval between 4 and 8 months following the last accomplishment),
when contamination is suspected, and after system overhaul.

Do not use a compressor that is suspected of producing contaminated air or that
has failed an air sample analysis until the cause of the problem has been corrected
and a satisfactory air sample analysis has been obtained validating the production
of acceptable air.
Air drawn from submarine or submarine tender HP air storage banks for use as diver’s
breathing air shall be sampled in accordance with the PMS maintenance requirement
card applicable to the system, i.e., dry deck shelter system, submarine escape trunk,
SCUBA charging station. See paragraph 4-4.5 for additional information on system
line­up for sampling compressors where a sampling connection cannot be made
immediately downstream from the last air filtration device.
NOTE

4-4.2

The most recent air sample analysis report shall be maintained on file
for each air compressor (by compressor serial number) used to produce
diver’s breathing air.
NSWC-PC Air Sampling Services. NSWC-PC coordinates air sampling services
with a commercial gas analysis laboratory, under the Defense Compressed Air
Testing Program. Commands are not authorized to communicate directly with
the laboratory and are directed to the Defense Compressed Air Testing (DCAT)
website (https://military.airtesting.com/login.php) to request air sampling services
and retrieve results. NSWC-PC telephone number is listed in Appendix 1C.

Commands will be notified by quickest means possible if any samples do not meet
minimum purity requirements. The user will discontinue use of the air source
until cause of contamination is corrected. Corrective action must be taken prior to
laboratory retest.

CHAPTER 4 — Dive Systems

4-9

4-4.3

Local Air Sampling Services. Commands may use local government air analysis

facilities (e.g., shipyards, ship repair facilities, government research laboratories)
to analyze diver’s air samples.
Units may use local commercial air analysis facilities to analyze diver’s air samples
only after the facility has been certified by NAVSEA Code 00C. Commands
interested in using local commercial facilities must contact NAVSEA 00C3 to
arrange a quality survey at the facility. Commands may be required to bear the cost
of certifying the commercial air analysis facility.
4-4.4

Portable Air Monitor (PAM). The ANU approved PAM is a compact air monitor

capable of field testing diver’s air for oxygen, carbon monoxide, carbon dioxide,
and volatile organic compounds. The PAM cannot test for water vapor, oil mist,
or particulates. For this reason, the PAM is not a substitute for periodic sampling
under the Diver’s Air Sampling Program.
The PAM may be used to perform continuous on-line sampling or periodic
verification of an ANU compressor’s output and to sample non-U.S. Navy owned
air sources IAW paragraph 4-3.1 and the Non-Navy Compressors Checklist. The
Portable Air Monitor must be calibrated prior to use and safeguarded from rough
handling.

4-4.5

General Air Sampling Procedures. The following general guidance is provided to

obtain air samples:

n Follow the procedures on applicable air sample MRC card and those included
with the air sampling kit.
n Prior to taking air samples ensure all applicable PMS has been completed on
the compressor and associated filtration system.
n Ensure that the compressor being sampled has reached full operating condition
(proper operating temperature, oil pressure, and air pressure) and is properly
lined up to deliver air to the sample kit.
n Ensure that the compressor’s intake is clear of any potential sources of
contamination (including consideration of ambient smog levels in areas where
smog is a problem).
n Take separate samples from each compressor supplying the system. Samples
from the compressors should be taken as close to the compressor as possible
but down stream of the last compressor-mounted air treatment device (moisture
separator, filter, etc.).
1. Some HP systems do not have fittings that allow samples to be taken from the

system at a location other than the charging connection. In this case, the storage
flasks should be isolated from the system, the system purged with air from the
compressor to be sampled and the sample taken at the charging connection.

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2. Some LP systems do not have fittings that allow samples to be taken at

connections other than the diver’s manifold. In this case, isolate any HP
source(s) from the LP system and purge the system with air from the LP
compressor. Obtain the sample from the diver’s manifold.

NOTE

4-5

Failure to purge the system of air produced from other compressors or
storage flasks will lead to an invalid air sample for the compressor being
sampled.

DIVE SYSTEM COMPONENTS
4-5.1

Diving Compressors. Many air systems used in Navy diving operations include at
least one air compressor as a source of air. It is essential that the operators of these
compressors have an understanding of compressor components and principles
of gas compression as described in this section. Compressors used to supply air
for diving or as drive air to transfer oxygen or mixed gases shall be listed in the
NAVSEA/00C Authorized for Navy Use (ANU) list or be included in the scope of
certification a certified diving system (except as noted in paragraph 4-3.1).

There are many different designs of air compressors. Reciprocating air compressors
are the only compressors authorized for use in Navy air diving operations. Low
pressure (LP) compressors can provide rates of flow sufficient to support surfacesupplied air diving or recompression chamber operations. High-pressure (HP)
models can charge high- pressure air banks and SCUBA cylinders.
Normally, Reciprocating compressors have their rating (capacity in cubic feet per
minute and delivery pressure in psig) stamped on the manufacturer’s identification
plate. If not provided directly, capacity will be provided and may be determined by
conducting a compressor output test (see Topside Tech Notes).
The compressor rating is usually based on inlet conditions of 70°F (21.1°C), 14.7
psia barometric pressure, and 36 percent relative humidity (an air density of 0.075
pound per cubic foot). If inlet conditions vary, the actual capacity either increases
or decreases from rated values. Since the capacity is the volume of air at defined
atmospheric conditions, compressed per unit of time, it is affected only by the first
stage, as all other stages only increase the pressure and reduce temperature.
All compressors are stamped with a code, consisting of at least two, but usually
four to five, numbers that specify the bore and stroke of the pistons. The bore
(piston diameter) and stroke (length the piston moves through a cycle) determines
the displacement and therefore the capacity.
The actual capacity of the compressor will always be less than the displacement
because of the clearance volume of the cylinders. This is the volume above the
piston that does not get displaced by the piston during compression.
Any diving air compressor not permanently installed must be firmly secured in
place. Most portable compressors are provided with lashing rings for this purpose.

CHAPTER 4 — Dive Systems

4-11

4-5.1.1

Lubrication. Compressors used to produce military diver’s breathing air are

normally of oil-lubricated, two-to-five-stage reciprocating type. Oil lubrication:
n Prevents wear between friction surfaces
n Seals close clearances
n Protects against corrosion
n Transfers heat away from heat-producing surfaces

n Transfers minute particles generated from normal system wear to the oil sump
or oil filter if so equipped
A malfunctioning oil-lubricated compressor poses a contamination risk to the
diver’s air supply. Contamination may occur due to excess oil mist being passed
out of the compressor due to excess clearances, broken parts, or overfilling the oil
sump.
Gaseous hydrocarbons and carbon monoxide may also be produced should a
compressor overheat to the point of causing combustion of the lubricating oil and/
or gaskets and other soft goods found in the compressor. Compressor overheating
may be caused by a number of events including, but not limited to: loss of cooling
water or air flow, low lube oil level, malfunction of stage unloader or relief valves,
friction from broken or excessively worn parts, and/or compressor operation at an
RPM above its rated capacity.
Diver’s air filtration systems are designed to work with compressors operating
under normal conditions, and cannot be relied on to filter or purify air from a
malfunctioning compressor.
WARNING		

4-5.1.1.1

4-5.1.2

Do not use a malfunctioning compressor to pump diver’s breathing air or
charge diver’s air storage flasks as this may result in contamination of
the diver’s air supply.
Lubrication Specifications. Compressor oil shall be changed IAW PMS.
Lubricants used in diver’s air compressors shall conform to MIL-PRF-17331
(2190 TEP) for normal operations, or MIL-PRF-17672 (2135TH) for cold weather
operations. Where the compressor manufacturer specifically recommends the
use of a synthetic base oil in their compressor for production of breathing air,
that manufacturer recommended synthetic base oil may be used in lieu of MILPRF-17331 or MIL-PRF-17672 oil.
Maintaining an Oil‑Lubricated Compressor. Proper maintenance is vital when

using an oil-lubricated compressor to limit the amount of oil introduced into the
diver’s air (see Topside Tech Notes). When using any oil lubricated compressor
for diving, the air must be checked for oil contamination. Diving operations shall
be aborted at the first indication that oil is in the air being delivered to the diver.
An immediate air analysis must be conducted to determine whether the amount of

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oil present exceeds the maximum permissible level in accordance with table Table
4-1.
It should be noted that air in the higher stages of a compressor has a greater amount
of lubricant injected into it than in the lower stages. Compressors selected for a
diving operation should provide as close to the required pressure for that operation
as possible. A system that provides excessive pressure contributes to the buildup of
lubricant in the air supply.
4-5.1.3

Water Vapor Control. A properly operated air supply system should never permit

the air supplied to the diver to reach its dewpoint. Dewpoint is the temperature that
water condenses out of air. The lower the dewpoint, the lower amount of water
vapor present in the air. Controlling the amount of water vapor in the supplied air
is normally accomplished by one or both of the following methods:
n Compression/Expansion. As high-pressure air expands across a pressure
reducing valve, the partial pressure of the water vapor in the air is decreased.
Since the expansion takes place at essentially a constant temperature
(isothermal), the partial pressure of water vapor required to saturate the air
remains unchanged. Therefore, the relative humidity of the air is reduced.
n Cooling. Cooling the air prior to expanding it raises its relative humidity,
permitting some of the water to condense. The condensed liquid may then be
drained from the system.
Cooling of the air occurs in intercoolers. Intercoolers are heat exchangers that
are placed between the stages of a compressor to control the air temperature.
Water, flowing through the heat exchanger counter to the air flow, serves both to
remove heat from the air and to cool the cylinder walls. Intercoolers are frequently
air cooled. During the cooling process, water vapor is condensed out of the air
into condensate collectors. The condensate must be drained periodically during
operation of the compressor, either manually or automatically.

4-5.1.4

4-5.1.5

Volume Tank. A volume tank is required when operating directly from a low
pressure air compressor. The volume tank maintains the air supply should the
primary supply source fail, providing time to actuate a secondary air supply. It also
absorbs pressure pulsations resulting from the compressor operation. A volume
tank may also be required when the volume tank is an integral part of the system
design such as a Lightweight Dive System. When operating from a high-pressure
air source, a volume tank is not required if the pressure reducer has been proven to
withstand significant pressure cycling caused by use of UBA demand regulators.
Pressure Regulators. A back-pressure regulator will be installed downstream
of the compressor discharge. A compressor only compresses air to meet the
supply pressure demand. If no demand exists, air is simply pumped through the
compressor at atmospheric pressure. Systems within the compressor, such as
the intercoolers, are designed to perform with maximum efficiency at the rated
pressure of the compressor. Operating at any pressure below this rating reduces
the efficiency of the unit. Additionally, compression reduces water vapor from the

CHAPTER 4 — Dive Systems

4-13

air. Reducing the amount of compression increases the amount of water vapor in
the air supplied to the diver.
The air supplied from the compressor expands across the pressure regulator and
enters the air banks or volume tank. As the pressure builds up in the air banks or
volume tank, it eventually reaches the relief pressure of the compressor, at which
time the excess air is simply discharged to the atmosphere. Some electricallydriven compressors are controlled by pressure switches installed in the volume
tank or HP flask. When the pressure reaches the upper limit, the electric motor is
shut off. When sufficient air has been drawn from the volume tank or HP flask to
lower its pressure to some lower limit, the electric motor is restarted.
4-5.1.6

Air Filtration System. Military diving compressors shall be equipped with an air

filtration system that is listed in the NAVSEA/00C ANU list or be an element of
a certified diving system. The term air filtration system as used here is inclusive,
referring collectively to compressed gas system filters, moisture separators, air
purification, air cooling, and dehydration equipment.
NOTE

Only white virgin Teflon tape that is made in accordance with MILSPEC
A-A 58093 is authorized for use on Navy Diving Life Support Systems
(DLSS).

NOTE

Do not use commercial cleaning products/agents, only utilize properly
mixed Non Ionic Detergent (NID) to clean exterior of Navy Diving Life
Support Systems.  Do not flood console case or the gauges with water
and cleaner.

4-5.2

High-Pressure Air Cylinders and Flasks. HP air cylinders and flasks are vessels

designed to hold air at pressures over 600 psi. Any HP vessel to be used as
a diving air supply unit must bear appropriate Department of Transportation
(DOT), American Society of Mechanical Engineers (ASME), or military symbols
certifying that the cylinders or flasks meet high-pressure requirements.

A complete air supply system includes the necessary piping and manifolds, HP
filter, pressure reducing valve, and a volume tank. An HP gauge must be located
ahead of the reducing valve and an LP gauge must be connected to the pressure
reducing valve and a volume tank (when required).
NOTE

All valves and electrical switches that directly influence the air supply
shall be labeled: “DIVER’S AIR SUPPLY - DO NOT TOUCH” Banks of
flasks and groups of valves require only one central label at the main
stop valve.

In using this type of system, one section must be kept in reserve. The divers take air
from the HP air flask or volume tank and is regulated to conform to the air supply
requirements of the dive.
As in SCUBA operations, the quantity of air that can be supplied by a system using
cylinders or flasks is determined by the initial capacity of the cylinders or flasks

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U.S. Navy Diving Manual­— Volume 1

and the depth of the dive. The duration of the air supply must be calculated in
advance and must include a provision for decompression. Sample calculations for
dive duration, based on bank air supply, are presented in Chapter 8.
The secondary air system must be able to provide air in the event of a failure
of the primary system. The secondary air supply must be sized to be able to
support recovery of all divers (including standby) should the failure occur at the
worst possible time (per General Specification for the Design, Construction, and
Repair of Diving and Hyperbaric Equipment, NAVSEA TS500-AU-SPN-010). An
additional requirement must be considered if the same air system is to support
a recompression chamber. Refer to Chapter 18 for information on the additional
capacity required to support a recompression chamber.
4-5.2.1

Compressed Gas Handling and Storage. Compressed gas shall be transported in
cylinders meeting Department of Transportation (DOT) regulations applicable to
the compressed gas being handled. DOT approved cylinders bear a serial number,
DOT inspection stamp, a pressure rating, the date of last hydrostatic test, are
equipped with applicable cylinder valve, and are appropriately color coded.

Refer to the following references for more detailed information on compressed gas
handling and storage:
n Industrial Gases, Generating, Handling and Storage, NAVSEA Technical
Manual S9086­SX­STM­000/CH­550.
n American and Canadian Standard Compressed-Gas Cylinder Valve Outlet and
Inlet Connections (ANSI-B57.1 and CSA-B96).
n American National Standard Method of Marking Portable Compressed-Gas
Containers to Identify the Material Contained (Z48.1).
n Guide to the Preparation of Precautionary Labeling and Marking of Compressed
Gas Cylinders (CGA Pamphlet C­7).
4-5.3

Diving Gauges.

4-5.3.1

Selecting Diving System Gauges. Select a gauge whose full scale reading

approximates 130 percent to 160 percent of the maximum operating pressure of
the system. Following this guideline, a gauge with a full scale reading of 4,000
or 5,000 psi would be satisfactory for installation in a system with a maximum
operating pressure of 3,000 psi.
Selecting gauge accuracy and precision should be based on the type of system and
how the gauge will be used. For example, a high level of precision is not required
on air bank pressure gauges where only relative values are necessary to determine
how much air is left in the bank or when to shut down the charging compressor.
However, considerable accuracy (¼ of 1 percent of full scale for saturation diving
operations and 1 percent of full scale for surface supplied operations) is required
for gauges that read diver depth (pneumofathometers and chamber depth gauges).

CHAPTER 4 — Dive Systems

4-15

Depth gauge accuracy is critical to selecting the proper decompression or treatment
table.
Many gauges are provided with a case blowout plug on the rear surface. The
blowout plug protects the operator in the event of Bourdon tube failure, when case
overpressurization could otherwise result in explosion of the gauge lens. The plug
must not be obstructed by brackets or other hardware.
All diving system gauges should be provided with gauge isolation valves and
calibration fittings. If a gauge fails during an operation, the isolation valve closes
to prevent loss of system pressure.
4-5.3.2

Calibrating and Maintaining Gauges. All installed gauges and portable gauges

(tank pressure gauges, submersible tank pressure gauges, and gauges in small
portable test sets) in use must be calibrated or compared in accordance with PMS
by a certified METCAL facility unless a malfunction requires repair and calibration
sooner. Programs such as the Shipboard Gauge Calibration Program as outlined
in the NAVSEA Instruction 4734.1 (series) provide authority for a command to
calibrate its own gauges. Calibrated gauges not in use should be kept in a clean,
dry, vibration­free environment.
Calibration and comparison data must include the date of the last satisfactory check,
the date the next calibration is due, and the activity accomplishing the calibration.
Gauges are delicate instruments and can be damaged by vibration, shock, or impact.
They should be mounted in locations that minimize these factors and should always
be mounted to gauge boards, panels, or brackets. The piping connection should
not be the sole support for the gauge. A gauge can be severely damaged by rapid
pulsations of the system when the fluid pressure is being measured. When this
condition exists, a gauge snubber should be installed between the isolation valve
and the gauge to protect the instrument. Most gauges are not waterproof and are
not designed for use in a marine environment. Enclosures of transparent acrylic
plastic, such as lucite, can be used to protect the gauges from water and salt spray.
However, the enclosure must have vent passages to allow the atmospheric pressure
to act on the gauge sensing element.
4-5.3.3

Helical Bourdon Tube Gauges. Manufacturers make two basic types of helical

Bourdon tube gauges for use on recompression chambers and for surface-supplied
diving systems. One is a caisson gauge with two ports on the back. The reference
port, which is capped, is sealed with ambient air pressure or is piped to the exterior
of the pressure chamber. The sensing port is left open to interior pressure. The
other gauge is the standard exterior gauge.
Both are direct-drive instruments employing a helical Bourdon tube as the sensing
element. The gauges are accurate to ¼ of 1 percent of full scale pressure at all
dial points. With no gears or linkages, the movement is unaffected by wear, and
accuracy and initial calibration remains permanent.

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U.S. Navy Diving Manual­— Volume 1

A comparative check in lieu of recalibration should be made in accordance with
the Planned Maintenance System. A dial adjustment screw on the front face of the
gauge provides for zero-­point adjustment and special set pressure. Dial readout
units of measure can be in pounds per square inch (psi) and/or feet of seawater
(fsw).
4-5.3.4

Pneumofathometer. A pneumofathometer is a remote depth sensing system used

in surface supplied diving to monitor the divers depth from the surface. The
pneumofathometer consists of: a valve that allows air from the diver’s manifold
into the system, a gauge mounted in the divers control console after the valve, and
a hose that is connected to the gauge married to the diver’s umbilical.
The diver’s end of the hose is secured to the diver at chest height. As the diver
descends in the water column (and while on the bottom) the console operator uses
the valve to force water out of the hose until a generally constant reading over the
expected maximum depth is noted on the gauge (taking care not to over pressurize
the gauge). The valve is then secured and the diver’s depth (equal to the height of
the water column displaced by the air) is read on the gauge.
The pneumofathometer is given a final purge just before leaving bottom and not
purged while on ascent.

CHAPTER 4 — Dive Systems

4-17

PAGE LEFT BLANK INTENTIONALLY

4-18

U.S. Navy Diving Manual­— Volume 1

CHAPTER 5

Dive Program Administration
5-1

INTRODUCTION
5-1.1

5-1.2

Purpose. This chapter promulgates general policy pertaining to command dive
logs, personal dive logs, diving mishap reports, HAZREPS, and failure analysis
reports within U.S. Navy diving activities.
Scope. The record keeping and reporting instructions outlined in this chapter

pertain to command diving logs, individual diving logs, personal diving records,
diving mishap and near-mishap reports, and failure analysis reports.

5-2

OBJECTIVES OF THE RECORD KEEPING AND REPORTING SYSTEM

There are five objectives in the diving record keeping and reporting system.
1. Establish a comprehensive record of diving activity for each command engaged in

diving. The Command chamber and DJRS Logs are a collection of standardized
diving records that establishes the dive history for each diving command and
constitutes the minimum documentation required for all uneventful dives.

2. Gather data for safety and trend analysis. Information about current Navy diving

operations (including manned use of recompression chambers) is provided to the
Naval Safety Center (NAVSAFCEN) through the Dive/Jump Reporting System
(DJRS). Hyperbaric Treatments and diving mishaps are reported via the Web
Enabled Safety System (WESS) per OPNAVINST 5102.1 (series). This information
enables the Safety Center to identify safety related problems associated with
operating procedures and training.

3. Prevent mishaps. Information about diving hazards and mishaps is disseminated to

the Fleet (in redacted form) by Naval Safety Center to provide timely, complete,
and accurate information that enables commands to take appropriate action to
prevent similar mishaps.

4. Report information about equipment deficiencies to the responsible technical

agencies via NAVSEA 00C through the Failure Analysis Reporting (FAR) system.

5. Provide records for a personal log.
5-3

RECORD KEEPING AND REPORTING DOCUMENTS

The documents established to meet the objectives of the record keeping and
reporting system are:
n Command Dive Log
n Recompression Chamber Log

CHAPTER 5 — Dive Program Administration

5-1

n Dive/Jump Reporting System (DJRS)
n Personal Dive Log (electronic or hard copy)
n Failure Analysis Report (FAR) for ANU diving systems and equipment and
certified Diver’s Life Support Systems (DLSS)
n Diving Mishaps/Hyperbaric Treatments reports (WESS)
n Diving Hazard (near mishap) reports (WESS)
n Equipment Mishap Information Sheet (Figure 5‑1)
5-4

COMMAND DIVE LOG

The Command Dive Log is a chronological collection of all dive records conducted
at a diving activity. It contains information on dives by personnel permanently and
temporarily attached to the activity.
Dives conducted while temporarily assigned to another diving command shall be
recorded in DJRS under the host command Unit Identification Code (UIC), and in
the Command Dive Log of the host command.
OPNAVINST 3150.27 (series) requires retention of the Command Dive Log for 3
years. DJRS is an acceptable method of maintaining a Command Dive Log. The
minimum data items in the Command Diving Log include:
n Date of dive
n Purpose of the dive
n Identification of divers and standby divers
n Times left and reached surface, bottom time
n Depth
n Decompression time
n Air and water temperature
n Signatures of Diving Supervisor or Diving Officer/Master Diver
5-5

RECOMPRESSION CHAMBER LOG

The Recompression Chamber Log is a legal record of procedures and events for
an entire dive. All U.S. Navy activities operating recompression chamber systems
shall maintain a recompression chamber log.
Recompression chamber logs shall be kept in real time and maintained in a legible
narrative. The Diving Supervisor, Master Diver and/or Diving Officer shall

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U.S. Navy Diving Manual — Volume 1

review and sign the log daily or at the end of their watches. Upon conclusion of
any treatments the attending Diving Medical Officer (DMO) or senior medical
representative should place an entry at the end of the log prior to closeout signatures
with a summary of the patient’s condition prior to treatment, response during
treatment, and condition after treatment.
Recompression Chamber Logs shall not be loose leaf. Logs may be printed and
bound commercially, through Defense Printing Service, or blank bound log books
may be adapted for use. Adherence to standard Navy practice for making entries
and corrections to entries (one line errors and initial, late entries…) ensures clarity
while preserving a legal record of treatment. Logs shall be retained for 3 years after
the date of the dive.
The minimum data items in the Recompression Chamber Log include:
n Date of dive
n Purpose of the dive
n Identification of diver(s)/patients(s)
n Identification of tender(s)
n Time left surface
n Time reached treatment depth
n Time reached stop
n Time left stop
n Depth/time of relief
n Time on oxygen and time off oxygen
n Change in symptoms, including time of complete relief of symptom(s)
n Recompression chamber inside air temperature
n Medicine administered
n Fluid administered
n Fluid void
n Signatures of Diving Officer, Master Diver, or Diving Supervisor

CHAPTER 5 — Dive Program Administration

5-3

5-6

U.S. NAVY DIVE/JUMP REPORTING SYSTEM (DJRS)

DJRS is a computer based method of recording and reporting dives as required
by the OPNAVINST 3150.27 (series). The computer software provides diving
commands with a computerized record of dives.
DJRS enables commands to submit diving data to the Naval Safety Center. The
computer software allows users to enter dive data, transfer data to the Naval Safety
Center, and to generate individual diver and command reports. The DJRS was
designed for all branches of the U.S. Armed Services and can be obtained through:
Commander, Naval Safety Center
Attention: Code 37
375 A Street
Norfolk, VA 23511-­4399
5-7

PERSONAL DIVE LOG

Each Navy trained diver shall maintain a record of dives in accordance with
OPNAVINST 3150.27 (series). One way for each diver to accomplish this is
to keep a copy of each Diving Log Form in a binder or folder. The Diving Log
Form is generated by the DJRS software. These forms, when signed by the Diving
Supervisor and Diving Officer, are an acceptable record of dives that may be
required to justify special payments and may help substantiate claims made for
diving related illness or injury. If an individual desires a hard copy of the dives, the
diver’s command can generate a report using DJRS. If a complete individual dive
history is desired, the diving activity must submit a written request to the Naval
Safety Center.
5-8

EQUIPMENT FAILURE OR DEFICIENCY REPORTING

The Failure Analysis Reporting system provides the means for reporting, tracking
and resolving material failures or deficiencies in ANU/DLSS equipment and
systems. The FAR provides a rapid method to communicate failures or deficiencies
to the configuration manager, engineers, and technicians who are qualified to
resolve the deficiency. The system can be accessed at https://secure.supsalv.org
00C3 Diving, or through PMS-EOD and SPECWAR quick links at http://supsalv.
org for Naval Special Warfare/EOD managed systems. Anyone that discovers an
equipment failure or deficiency shall notify the Master Diver, Diving Supervisor,
work center supervisor, or other responsible person who shall ensure that a FAR is
properly submitted.
5-9

DIVE MISHAP/NEAR MISHAP/HAZARD REPORTING
5-9.1

Mishap/Near-mishap/Hazard. A mishap is an unplanned or unexpected event that

causes death, injury, occupational illness (including days away from work, job
transfer or work restriction), or loss of, or serious damage to equipment. A nearmishap is an act or event where injury or equipment damage was avoided by mere
chance. A hazard is an unsafe act or condition that degrades safety and increases

5-4

U.S. Navy Diving Manual — Volume 1

the probability of a mishap. Dive mishaps, near mishaps, and hazards shall be
reported IAW OPNAVINST 5102.1 (series) and the 3150.27(series). Activities
without reliable internet access may obtain an offline version of WESS through
NAVSAFECEN for uploading via email when a connection becomes available.
NOTE

5-9.2

In the interest of creating and maintaining a learning organization, to
the greatest extent possible, the reporting of safety issues or concerns
shall be handled so that persons reporting or individuals involved in the
reported event are not subject to punishment or censure.
Judge Advocate General (JAG Investigation). JAG Manual provides instructions

for investigation and reporting procedures required in instances when the mishap
may have occurred as a result of procedural or personnel error. Per OPNAVINST
5202.1, a JAG investigation must remain separate from any Naval Safety
Investigation, and the Safety Investigation Board (SIB) shall be granted access to
all evidence collected by the JAGMAN.

5-9.3

Reporting Criteria. Reportable diving mishaps include all class A, B, C, and D

mishaps involving diving or support of diving missions. All on-duty diving cases
involving the following specific conditions shall be reported to NAVSAFECEN:
n All recompression treatments,
n Any incidence of Type I or II DCS
n All cases of pulmonary over-inflation syndromes

n Any case of loss of consciousness
n CNS or pulmonary oxygen toxicity
NOTE

5-9.4

NOTIFY NAVSEA at 00C3@supsalv.org and 00C3B@supsalv.org or
(202) 781-1731 (available 24hrs) with non-privileged information of any
reportable mishap as soon as possible. Immediate contact may prevent
loss of evidence vital to the evaluation of the equipment or prevent
unnecessary shipment of equipment to NEDU.
HAZREPS. Hazards and near-mishaps that do not warrant submission of a Safety

Investigation Report (SIREP) are reported as HAZREPS IAW OPNAVINST
5102.1 (series). Submission of HAZREPS ensures safety information is collected
and analyzed for trends to identify training, qualification, procedural, or equipment
issues that may lead to mishaps. Self-evaluation and self-reporting of near mishaps
is a key measure of professionalism and demonstrates concern for the greater
diving community.
The following are examples of diving hazards and near-mishaps:
1. Execution of an emergency procedure, examples include, but are not limited to:

n Unplanned shift to secondary air.
CHAPTER 5 — Dive Program Administration

5-5

n Aborted dive due to unexpected issue/event.
n Trapped/Fouled diver where standby or buddy diver was required.
n Lost diver where stand-by diver was required.
2. Exceeding prescribed limits, including, but not limited to:

n Maximum depth.
n Bottom time.
n Omitted decompression.
n Oxygen exposures above allowed pulmonary oxygen limits.
3. Any abnormal condition discovered after equipment and systems are prepared for

use that could result in an injury, examples include, but are not limited to:

n CO2 canister installed or filled improperly.
n CO2 canister not installed.
n Exhaust valves installed improperly.
n Dive system aligned improperly.
4. Any external (Port Operations, tended or adjacent units…) systems, equipment, or

conditions that may adversely affect or impair diver safety, examples include,
but are not limited to:

n Ship’s equipment operated or tags cleared without proper authorization
before, during, or after divers enter the water.
n Unauthorized cranes operated overhead of divers.
n Small boat/craft operations conducted over/in the vicinity of divers.
n Unauthorized discharges/SONAR while divers are in the water.
5-10

ACTIONS REQUIRED

U.S. Navy diving units shall perform the following procedure for all reportable
diving mishaps in accordance with Section 5-9.
1. Immediately secure and safeguard from tampering all diver­-worn and ancillary/

support equipment that may have contributed to the mishap. This equipment
should also include, but is not limited to, the compressor, regulator, depth gauge,
submersible pressure gauge, diver dress, buoyancy compensator/life preserver,
weight belt, and gas supply (SCUBA, emergency gas supply, etc.).

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U.S. Navy Diving Manual — Volume 1

2. Expeditiously report circumstances of the mishap via WESS. Commands without

WESS access should report by message (see OPNAVINST 5102.1 (series) for
format requirements) to:

n NAVSAFECEN NORFOLK VA//JJJ// with information copies to CNO
WASHINGTON DC//N773// COMNAVSEASYSCOM WASHINGTON
DC//00C// and NAVXDIVINGU PANAMA CITY FL//JJJ//.
n If the mishap is MK 16 MOD 1 related, also send information
copies
to
PEO
LMW
WASHINGTON
DC//PMS-­EOD//
NAVSURFWARCENIHEODTECHDIV INDIAN HEAD MD, and
NAVSURFWARCENIHEODTECHDIV TECHSUPP DET INDIAN
HEAD MD.
n If the mishap is MK 16 MOD 0 related, also send information copies to
COMNAVSEASYSCOM WASHINGTON DC//NSW//
n If the mishap occurs at a shore­based facility, contact NAVFAC SCA, also
send information copies to NFESC EAST COAST DET WASHINGTON
DC//55//.
3. Equipment may need to be shipped to NEDU for further investigation. Contact

NAVSEA 00C3 for determination.

4. Expeditiously prepare a separate, written report of the mishap. The report shall

include:

n A completed Equipment Mishap Information Sheet (Figure 5­-1)
n A sequential narrative of the mishap including relevant details that might
not be apparent in the data sheets
5. The data sheets and the written narrative shall be mailed by traceable registered

mail to:

Commanding Officer
Navy Experimental Diving Unit
321 Bullfinch Road
Panama City, Florida 32407-7015
Attn: Code 03, Test & Evaluation
6. Package a certified copy of all pertinent 3M records and deliver to NAVSEA/00C3

on­-scene representative.

5-10.1

Equipment Mishap Information Sheet. The equipment mishap sheet is submitted

with reports of all diving mishaps when malfunction or inadequate equipment
performance, or unsound equipment operating and maintenance procedures may
be a factor. A copy of the form shall be submitted with any equipment sent to Navy
Experimental Diving Unit (NEDU) for testing related to a mishap.

CHAPTER 5 — Dive Program Administration

5-7

The primary purpose of this requirement is to identify any material deficiency that
may have contributed to the mishap. Any suspected malfunction or deficiency of
life support equipment will be thoroughly investigated by controlled testing at
NEDU. NEDU has the capability to perform engineering investigations and full
unmanned testing of all Navy diving equipment under all types of pressure and
environmental conditions. Depth, water turbidity, and temperature can be duplicated
for all conceivable U.S. Navy dive scenarios. In many instances submission of a
FAR may also be required.
Contact NAVSEA/00C3 to assist diving units with investigations and data collection
following a diving mishap. 00C3 will assign a representative to inspect the initial
condition of equipment and to pick up or ship all pertinent records and equipment
to NEDU for full unmanned testing. Upon receipt of the equipment, NEDU will
conduct unmanned tests as rapidly as possible and will then return the equipment
to the appropriate activity.
NOTE:

5-10.2

Do not tamper with equipment without first contacting NAVSEA/00C3 for
guidance.
Shipment of Equipment. To expedite delivery, SCUBA, MK 16 and EGS bottles

shall be shipped separately in accordance with current DOT directives and
command procedures for shipment of compressed gas cylinders. Cylinders shall
be forwarded in their exact condition of recovery (e.g., empty, partially filled,
fully charged). If the equipment that is believed to be contributory to the accident/
incident is too large to ship economically, contact NEDU to determine alternate
procedures.

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U.S. Navy Diving Manual — Volume 1

EQUIPMENT MISHAP INFORMATION SHEET
GENERAL
Unit point of contact_________________________________ Position__________________________
Command UIC__________________ Date_______________ Time of occurrence_________________
__________________________________________________________________________________
EQUIPMENT (indicate type of all equipment worn/used)
UBA:

Contributing factor________________________

SCUBA_________________ MK21__________________ MK20__________________
MK 16_________________ MK 25 MOD 2_______________ KM37______________
Other (specify)________________________________________________________

Suit type:

Dry________________ Wet________________ Hot water______________________

Other dress:

Gloves_____________ Booties______________ Fins__________________________
Mask______________ Snorkel_____________ Knife__________________________
Weight belt (indicate weight)_____________________________________________
Navy Dive Computer _____________ Files from NDC Downloaded ______________
Depth gauge___________________ Last calibration date_______________________

Buoyancy compensator/life preserver:_________________________________________________
Inflated at scene:______________ Partially______________ Operational ____________________
Inflation mode: Oral____________ CO2 __________________ Independent supply______________
Cylinders:

Number worn_________ Size (cu ft)__________ Valve type_____________________
Gas mix______________ Aluminum__________ Steel_________________________
Surface pressure:

Before____________________ After______________________

Regulator:__________________ Last PMS date____________ Functional at scene?_______________
Submersible pressure gauge:___________________________ Functional at scene?_______________
CONDITIONS

Location_____________________________________________________________

__________________________________________________________________________________
Depth__________fsw Visibility__________ft. Current__________Knots
Air temp______________°F

sea state____________(0-9)

Water temp: at surface_______________°F at depth______________°F

Bottom type (mud, sand, coral, etc.)______________________________________________________
DIVE TIME
Bottom________________ Decompression_________________ Total dive time_________________
Was equipment operating and maintenance procedure a contributing factor?
(Explain):________________________________________________________________________
Is there contributory error in O&M Manual or 3M System?
(Explain):________________________________________________________________________
OTHER CONTRIBUTING FACTORS________________________________________________________

Figure 5-1. Equipment Accident/Incident Information Sheet. (sheet 1 of 2).

CHAPTER 5 — Dive Program Administration

5-9

EQUIPMENT MISHAP INFORMATION SHEET
Pertaining to UBA involved, fill in blanks with data required by items 1 through 9.
KM 37 NS


MK 20


SCUBA


MK 16


MK 25


OTHER


1. Number of turns to secure topside gas umbilical supply:
N/A

N/A

N/A

2. Number of turns to secure valve on emergency gas supply (EGS):
Reserve
Up/Down

N/A

N/A

N/A

Mouthpiece
Valve: Surface
________
Dive
________

Mouthpiece
Valve: Surface
________
Dive
_________

N/A

Air
Bottle
________

O2
________
Diluent
________

O2
Bottle
________

EGS
_____ psig

_____ psig

O2
_____ psig
Diluent
_____ psig

_____ psig

N/A

Diluent

N/A

3. Number of turns to secure gas supply at mask/helmet:

4. Number of turns to secure gas bottle:
N/A

5. Bottle Pressure:
EGS
_____ psig

6. Gas Mixture:
Primary
% ______
EGS

N2O2 _____

% ______

HeO2 _____

7. Data/color of electronic display:
N/A

N/A

N/A

Primary

N/A

________
Secondary
________
________
8. Battery voltage level:
N/A

N/A

N/A

Primary

N/A

________
Secondary
________
9. Condition of canister:
N/A

N/A

N/A

Note: If UBA involved is not listed above, provide information on separate sheet.

Figure 5‑1. Equipment Accident/Incident Information Sheet. (sheet 2 of 2).

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U.S. Navy Diving Manual — Volume 1

APPENDIX 1A

Safe Diving Distances from
Transmitting Sonar
1A-1

INTRODUCTION

The purpose of this appendix is to provide guidance regarding safe diving distances
and exposure times for divers operating in the vicinity of ships transmit­ting with
sonar. Table 1A‑1 provides guidance for selecting Permissible Exposure Limits
Tables; Table 1A‑2 provides additional guidance for helmeted divers. Tables 1A‑3
through 1A‑5 provide specific procedures for diving operations involving AN/
SQS-23, -26, -53, -56; AN/BSY-1, -2; and AN/BQQ-5 sonars. Table 1A‑6 provides
procedures for diving operations involving AN/SQQ-14, -30, and -32. Section 1A‑5
provides guidance and precautions concerning diver exposure to low-frequency
sonar (160-320Hz). Contact NAVSEA Supervisor of Diving (00C3B) for guidance
on other sonars. This appendix has been substantially revised from Safe Diving
Distances from Transmitting Sonar (NAVSEAINST 3150.2 Series) and should be
read in its entirety.
1A-2

BACKGROUND

Chapter 18 of OPNAVINST 5100.23 Series is the basic instruction governing
hearing conservation and noise abatement, but it does not address exposure to
waterborne sound. Tables 1A‑3 through 1A‑6 are derived from experimental and
theoretical research conducted at the Naval Submarine Medical Research Labora­
tory (NSMRL) and Naval Experimental Diving Unit (NEDU). This instruction
provides field guidance for determining safe diving distances from transmitting
sonar. This instruction supplements OPNAVINST 5100.23 Series, and should be
implemented in conjunction with OPNAVINST 5100.23 Series by commands that
employ divers.
The Sound Pressure Level (SPL), not distance, is the determining factor for estab­
lishing a Permissible Exposure Limit (PEL). The exposure SPLs in Tables 1A‑3
through 1A‑6 are based upon the sonar equation and assume omni-directional sonar
and inverse square law spreading. Any established means may be used to estimate
the SPL at a dive site, and that SPL may be used to determine a PEL. When the
exposure level is overestimated, little damage, except to working sched­ules, will
result. Any complaints of excessive loudness or ear pain for divers require that
corrective action be taken. Section 1A‑5 provides guidance for diver exposure to
low-frequency active sonar (LFA), which should be consulted if expo­sure to LFA
is either suspected or anticipated.
This appendix does not preclude the operation of any sonar in conjunction with
diving operations, especially under operationally compelling conditions. It is based
upon occupational safety and health considerations that should be imple­mented for

APPENDIX 1A — Safe Diving Distances from Transmitting Sonar

1A-1

routine diving operations. It should be applied judiciously under special operational
circumstances. The guidance in Tables 1A‑3 through 1A‑6 is intended to facilitate
the successful integration of operations.
1A-3

ACTION

Commanding Officers or Senior Officers Present Afloat are to ensure that diving
and sonar operations are integrated using the guidance given by this appendix.
Appropriate procedures are to be established within each command to effect coor­
dination among units, implement safety considerations, and provide efficient
operations using the guidance in Tables 1A‑3 though 1A‑6.
1A-4

SONAR DIVING DISTANCES WORKSHEETS WITH DIRECTIONS FOR USE
1A-4.1

General Information/Introduction. Permissible Exposure Limits (PEL) in minutes

for exposure of divers to sonar transmissions are given in Tables 1A-3 through
1A-6.
1A‑4.1.1

1A‑4.1.2

Effects of Exposure. Tables 1A‑3 through 1A‑5 are divided by horizontal double
lines. Exposure conditions above the double lines should be avoided for routine
operations. As Sound Pressure Level (SPL) increases above 215 dB for hooded
divers, slight visual-field shifts (probably due to direct stimulation of the semi­
circular canals), fogging of the face plate, spraying of any water within the mask,
and other effects may occur. In the presence of long sonar pulses (one second
or longer), depth gauges may become erratic and regulators may tend to freeflow. Divers at Naval Submarine Medical Research Laboratory experienc­ing
these phenomena during controlled research report that while these effects are
unpleasant, they are tolerable. Similar data are not available for un-hooded divers
but visual-field shifts may occur for these divers at lower levels. If divers need
to be exposed to such conditions, they must be carefully briefed and, if feasible,
given short training exposures under carefully controlled conditions. Because
the probability of physiological damage increases markedly as sound pressures
increase beyond 200 dB at any frequency, exposure of divers above 200 dB is
prohibited unless full wet suits and hoods are worn. Fully protected divers (full
wet suits and hoods) must not be exposed to SPLs in excess of 215 dB at any
frequency for any reason.
Suit and Hood Characteristics. There is some variation in nomenclature and

characteristics of suits and hoods used by divers. The subjects who partici­pated
in the Naval Submarine Medical Research Laboratory experiments used 3/8-inch
nylon-lined neoprene wet suits and hoods. Subsequent research has shown that
3/16-inch wet suit hoods provide about the same attenuation as 3/8-inch hoods.
Hoods should be well fitted and cover the skull completely includ­ing cheek and
chin areas. The use of wet-suit hoods as underwater ear protec­tion is strongly
recommended.
1A‑4.1.3

In­-Water Hearing vs. In-Gas Hearing. A distinction is made between in-water

hearing and in-gas hearing. In-water hearing occurs when the skull is directly in
contact with the water, as when the head is bare or covered with a wet-suit hood.

1A-2

U.S. Navy Diving Manual — Volume 1

In-gas hearing occurs when the skull is surrounded by gas as in the KM 37 diving
helmet. In-water hearing occurs by bone conduction—sound incident anywhere
on the skull is transmitted to the inner ear, bypassing the external and middle ear.
In-gas hearing occurs in the normal way—sound enters the external ear canal and
stimulates the inner ear through the middle ear.
1A-4.2

Directions for Completing the Sonar Diving Distances Worksheet. Follow the

steps listed below to determine Permissible Exposure Limits (PELs) for the case
when the actual dB Sound Pressure Level (SPL) at the dive site is unknown. Figure
1A-1 is a worksheet for computing the safe diving distance/exposure time. Figures
1A-2 through 1A-5 are completed worksheets using example problems. Work
through these example problems before applying the work­sheet to your particular
situation.
Step 1.

Diver Dress. Identify the type of diving equipment—wet-suit un-hooded; wet-suit
hooded; helmeted. Check the appropriate entry on step 1 of the worksheet.

Step 2.

Sonar Type(s). Identify from the ship’s Commanding Officer or representative the

Step 3.

PEL Table Selection. Use the Table 1A‑1 to determine which PEL table you will

type(s) of sonar that will be transmitting during the period of time the diver is
planned to be in the water. Enter the sonar type(s) in step 2 of the worksheet.

use for your calculations. For swimsuit diving use wet suit un-hooded tables.
Check the table used in step 3 of the worksheet.
Table 1A‑1. PEL Selection Table.
SONAR

DIVER DRESS:

All except
AN/SQQ
-14, - 30, -32

AN/SQQ
-14, -30, -32

Unknown
Sonar

Wet suit - Un-hooded

Table 1A‑3

Table 1A‑6

Start at 1000 yards and move in to
diver comfort

Wet suit - Hooded

Table 1A‑4

Table 1A‑6

Start at 600 yards and move in to
diver comfort

Helmeted

Table 1A‑5

No restriction

Start at 3000 yards and move in to
diver comfort

For guidance for sonars not addressed by this instruction, contact NAVSEA
(00C32).
NOTE

If the type of sonar is unknown, start diving at 600–3,000 yards, depending
on diving equipment (use greater distance if helmeted), and move in to
limits of diver comfort.

Step 4.

Distance to Sonar. Determine the distance (yards) to the transmitting sonar from

place of diver’s work. Enter the range in yards in step 4 of the worksheet.

APPENDIX 1A — Safe Diving Distances from Transmitting Sonar

1A-3

SONAR SAFE DIVING DISTANCE/EXPOSURE TIME WORKSHEET
1. Diver dress:		 Wet Suit - Un-hooded
			 Wet Suit - Hooded
			 Helmeted
2. Type(s) of sonar:
3. PEL Table 1A-3

; 1A-4

; 1A-5

; 1A-6

4. Range(s) to sonar (yards):
5. Estimated SPL at range(s) in step 3 (from table/column in step 3):
Reminder: If range is between two values in the table, use the shorter range.
If the SPL is measured at the dive site, use the measured value.
6. Depth Reduction

dB

Reminder: 0 if not helmeted, see table in instructions if helmeted.
7. Corrected SPL (Step 5 minus Step 6)
8. Estimated PEL at SPL (from table/column in step 3 of the appendix):
9. Duty Cycle Known: Yes

(do step 9); No

(stop)

		 Adjusted PEL for actual duty cycle
Actual DC % = 100 ×
sec. (pulse length /
sec. (pulse repetition period)
Actual DC % =
Adjusted PEL = PEL (from step 8)
min. × 20 / actual duty cycle (%)
=
			 PEL1 =

minutes; PEL2 =

min.

minutes

Reminder: Do not adjust the PEL if duty cycle is unknown.
10. Multiple Sonars: Yes
Sonar 1:

(do step 10); No

DT1 =

		PEL1 =
		DT1/PEL1 =
Sonar 2:

DT1 =

		PEL1 =
		DT1/PEL1 =
ND =

+

=

(stop)

(Desired dive duration)
(from Step 8 or 9, as applicable)
.
(Desired dive duration)
(from Step 8 or 9, as applicable)
.
(This is less than 1.0, so dive is acceptable and may proceed.)

Reminder: The Noise Dose must not exceed a value of 1.0.

Figure 1A-1. Sonar Safe Diving Distance/Exposure Time Worksheet.
1A-4

U.S. Navy Diving Manual — Volume 1

NOTE

If range is between two values in the table, use the shorter range.
This will insure that the SPL is not underestimated and that the PEL is
conservative.

Step 5.

Estimated SPL. In the PEL selection table (Table 1A‑1) determined in step 3 of

Step 6.

Helmeted Dive Depth Reduction.

the worksheet (Figure 1A‑1), locate the diving distance (range) in the appropriate
sonar equipment column. Read across to the leftmost column to find the SPL in
dB. For ranges intermediate to those shown use the shorter range. Enter this SPL
value in step 5 of the worksheet. If the SPL value in dB can be determined at the
dive site, enter the measured SPL value in step 5.

If the diver dress is not helmeted, enter 0 in step 6 of the worksheet and go to step
7 of these instructions.
Helmeted divers experience reduced sensitivity to sound pressure as depth
increases. The reductions listed in Table 1A‑2 may be subtracted from the SPLs for
helmeted divers in Table 1A‑5. Enter the reduction in step 6 of the worksheet. If the
depth is between two values in the table, use the lesser reduction since that value
will produce a conservative PEL.
Table 1A‑2. Depth Reduction Table.
Depth (FSW)

Reduction (dB)

Depth (FSW)

Reduction (dB)

9

1

98

6

19

2

132

7

33

3

175

8

50

4

229

9

71

5

297

10

Step 7.

Corrected SPL. The corrected SPL equals the Estimated SPL from step 5 minus

Step 8.

PEL Determination. Go to the SPL in the appropriate table and read one column

Step 9.

Duty Cycle/Adjusted PEL Calculation. Tables 1A‑3 through 1A‑6 assume

the reduction in dB from step 6. Enter the corrected SPL in step 7 of the worksheet.

right to find the PEL for the SPL shown in step 7 of the worksheet. Enter in step 8
of the worksheet.

a transmit duty cycle of 20 percent. Duty cycle (DC) is the percentage of time
in a given period that the water is being insonified (sonar transmitting). Sonar
operators may use various means of computing DC that are valid for the purpose
of this instruction. If the actual duty cycle is different from 20 percent, PELs may
be extended or shortened proportionally. Use step 9 of the worksheet to calculate
and enter the corrected PEL.

APPENDIX 1A — Safe Diving Distances from Transmitting Sonar

1A-5

The formula for duty cycle is:
DC = 100 × Pulse length (sec.) / Pulse Repetition Period (sec.)
The formula for the adjusted PEL is:
Adjusted PEL = PEL × 20 / actual duty cycle; Equation 1
Example Problem. An un-hooded wet suited diver is 16 yards from an AN/SQQ-14

sonar transmitting a 500 msec pulse (.5 seconds) every 10 seconds.
Solution. The actual duty cycle (DC) % is:

Actual DC % = 100 × .5 / 10 = 5 percent.
Locate the PEL from the table (which is for a 20% duty cycle). Compute the
adjusted PEL as:
Using worksheet step 9, Adjusted PEL = PEL (from step 8) 170 × 20/5=680 minutes.
If variable duty cycles are to be used, select the greatest percent value.
Step 10.

Multiple Sonar/Noise Dose Calculation. When two or more sonars are operating

simultaneously, or two or more periods of noise exposure from different SONARs
occur, the combined effects must be considered.
The formula to calculate Noise Dose (ND) from multiple SONARS is:
Pr = DT/PEL
ND = Pr1 + Pr2…
Where:
Pr is the PEL ratio of the desired or actual dive times
DT is the dive (exposure) time(s) (left surface to reach surface).
PEL is the Permissible Exposure Limit for each SONAR in use.
ND is the daily noise dose and must not exceed a value of 1.0.

NOTE

1A-6

Use DT1/PEL1 for the first sonar, DT1/PEL2 for the second sonar, up to
the total number of sonars in use. Noise dose may be computed for future
repetitive dives from different SONAR by using the planned dive time of
the repetitive dives (DT2, DT3…)

U.S. Navy Diving Manual — Volume 1

Example Problem. A hooded wet suited diver is 100 yards from a transmitting AN/

SQS-53A sonar and a transmitting AN/SQS-23 sonar for fifteen minutes.
Solution.

DT1 = 15 minutes
PEL1 (for SQS-53A) = 50 minutes
DT1/PEL1 = 15/50 = .3
DT2 = 15 minutes
PEL2 (for SQS-23) = 285 minutes
DT2/PEL2 = 15/285 = .05
ND = .3 + .05 = .35
This is less than 1.0 and therefore is acceptable.

APPENDIX 1A — Safe Diving Distances from Transmitting Sonar

1A-7

Example 1: You are planning a routine dive for 160 minutes using wet-suited divers without hoods at a
dive site 17 yards from an AN/SQQ-14 sonar. The duty cycle for the AN/SQQ-14 sonar is unknown. Is
this dive permitted? Provide justification for your decision.

SONAR SAFE DIVING DISTANCE/EXPOSURE TIME WORKSHEET
1. Diver dress:		
Wet Suit - Un-hooded
			Wet Suit - Hooded
			Helmeted ______

X

2. Type(s) of sonar: AN/SQQ-14
3. PEL Table 1A-3 __; 1A-4

; 1A-5 __; 1A-6 X

4. Range(s) to sonar (yards): 17
5. Estimated SPL at range(s) in step 3 (from table/column in step 3): SPL = 198 dB
Reminder: If range is between two values in the table, use the shorter range.
If the SPL is measured at the dive site, use the measured value.
6. Depth Reduction

0

dB

Reminder: 0 if not helmeted, see table in instructions if helmeted.
7. Corrected SPL (Step 5 minus Step 6)

SPL1 198 – 0 = 198 dB

8. Estimated PEL at SPL (from table/column in step 3 of the appendix): PEL1 = 170 minutes
9. Duty Cycle Known: Yes ______ (do step 9); No
X
(stop)
Adjusted PEL for actual duty cycle
		
Actual DC % = 100 × _____ sec. (pulse length / _____ sec. (pulse repetition period)
		
Actual DC % = ______
		
Adjusted PEL = PEL (from step 8) ___ min. × 20 / actual duty cycle (%) ___ = ___ min.
Reminder: Do not adjust the PEL if duty cycle is unknown.
10. Multiple Sonars: Yes _____ (do step 10); No

X

(stop)

Sonar 1:
DT1 =
(Desired dive duration)
		PEL1 =
(from Step 8 or 9, as applicable)
		DT1/PEL1 =
.
Sonar 2:
DT1 =
(Desired dive duration)
		PEL1 =
(from Step 8 or 9, as applicable)
		DT1/PEL1 =
.
ND = ____ + _____ = ____ (This is less than 1.0, so dive is acceptable and may proceed.)
Reminder: The Noise Dose must not exceed a value of 1.0.
The dive time of 160 minutes is permitted because the PEL is 171 minutes.

Figure 1A‑2. Sonar Safe Diving Distance/Exposure Time Worksheet (Completed Example).

1A-8

U.S. Navy Diving Manual — Volume 1

Example 2: You are planning a routine dive for 75 minutes using wet-suited divers without hoods at a
dive site which is 1000 yards from an AN/SQQ-23 sonar. The SPL was measures at 185 dB. The duty
cycle for the AN/SQS-23 sonar is unknown. Is this dive permitted? Provide justification for your decision.

SONAR SAFE DIVING DISTANCE/EXPOSURE TIME WORKSHEET
1. Diver dress:		
			
			

Wet Suit - Un-hooded
Wet Suit - Hooded
Helmeted ______

X

2. Type(s) of sonar: AN/SQS-23
3. PEL Table 1A-3

X ; 1A-4

; 1A-5 __; 1A-6

4. Range(s) to sonar (yards): 1000
5. Estimated SPL at range(s) in step 3 (from table/column in step 3): SPL = 185 dB
Reminder: If range is between two values in the table, use the shorter range.
If the SPL is measured at the dive site, use the measured value.
6. Depth Reduction

0

dB

Reminder: 0 if not helmeted, see table in instructions if helmeted.
7. Corrected SPL (Step 5 minus Step 6)

SPL1 185 – 0 = 185 dB

8. Estimated PEL at SPL (from table/column in step 3 of the appendix): PEL1 = 170 minutes
9. Duty Cycle Known: Yes ______ (do step 9); No
X
(stop)
Adjusted PEL for actual duty cycle
		
Actual DC % = 100 × _____ sec. (pulse length / _____ sec. (pulse repetition period)
		
Actual DC % = ______
		
Adjusted PEL = PEL (from step 8) ___ min. × 20 / actual duty cycle (%) ___ = ___ min.
Reminder: Do not adjust the PEL if duty cycle is unknown.
10. Multiple Sonars: Yes _____ (do step 10); No

X

(stop)

Sonar 1:
DT1 =
(Desired dive duration)
		PEL1 =
(from Step 8 or 9, as applicable)
		DT1/PEL1 =
.
Sonar 2:
DT1 =
(Desired dive duration)
		PEL1 =
(from Step 8 or 9, as applicable)
		DT1/PEL1 =
.
ND = ____ + _____ = ____ (This is less than 1.0, so dive is acceptable and may proceed.)
Reminder: The Noise Dose must not exceed a value of 1.0..
The dive time of 75 minutes is permitted because the PEL is 170 minutes.

Figure 1A-3. Sonar Safe Diving Distance/Exposure Time Worksheet (Completed Example).

APPENDIX 1A — Safe Diving Distances from Transmitting Sonar

1A-9

Example 3: You are planning a 98 fsw dive for 35 minutes using the KM 37 at a dive site which is 3000

yards from an AN/SQS-53C sonar. The duty cycle for the AN/SQS-53C sonar is unknown. Is this dive
permitted? Provide justification for your decision.

SONAR SAFE DIVING DISTANCE/EXPOSURE TIME WORKSHEET
1. Diver dress:		
			
			

Wet Suit - Un-hooded
Wet Suit - Hooded
Helmeted
X

2. Type(s) of sonar: AN/SQS-53C
3. PEL Table 1A-3

; 1A-4

; 1A-5 X ; 1A-6

4. Range(s) to sonar (yards): 3000
5. Estimated SPL at range(s) in step 3 (from table/column in step 3): SPL1 = 181 dB
Reminder: If range is between two values in the table, use the shorter range.
If the SPL is measured at the dive site, use the measured value.
6. Depth Reduction

6

dB

Reminder: 0 if not helmeted, see table in instructions if helmeted.
7. Corrected SPL (Step 5 minus Step 6)

SPL1 181 – 6 = 175 dB

8. Estimated PEL at SPL (from table/column in step 3 of the appendix): PEL1 = 50 minutes
9. Duty Cycle Known: Yes ______ (do step 9); No
X
(stop)
		 Adjusted PEL for actual duty cycle
			
Actual DC % = 100 × _____ sec. (pulse length / _____ sec. (pulse repetition period)
			
Actual DC % = ______
			
Adjusted PEL = PEL (from step 8) ___ min. × 20 / actual duty cycle (%) ___ = ___ min.
Reminder: Do not adjust the PEL if duty cycle is unknown.
10. Multiple Sonars: Yes _____ (do step 10); No

X

(stop)

Sonar 1: 		
DT1 =
(Desired dive duration)
			PEL1 =
(from Step 8 or 9, as applicable)
			DT1/PEL1 =
.
Sonar 2:
DT1 =
(Desired dive duration)
			PEL1 =
(from Step 8 or 9, as applicable)
			DT1/PEL1 =
.
ND = ____ + _____ = ____ (This is less than 1.0, so dive is acceptable and may proceed.)
Reminder: The Noise Dose must not exceed a value of 1.0.
The dive time of 35 minutes is permitted because the PEL is 50 minutes.

Figure 1A‑4. Sonar Safe Diving Distance/Exposure Time Worksheet (Completed Example).
1A-10

U.S. Navy Diving Manual — Volume 1

Example 4: You are planning a routine dive for 120 minutes using wet-suited divers with hoods at a dive
site which is 200 yards from an AN/SQS-53A sonar and 120 yards from an AN/SQS-23 sonar. The AN/
SQS-53A sonar is transmitting an 800 msec pulse (0.8 sec) every 20 seconds. The duty cycle for the
AN/SQS-23 sonar is unknown. Is this dive permitted? Provide justification for your decision.

SONAR SAFE DIVING DISTANCE/EXPOSURE TIME WORKSHEET
1. Diver dress:		
				
				

Wet Suit - Un-hooded
Wet Suit - Hooded
X
Helmeted

2. Type(s) of sonar: AN/SQS-53A and AN/SQS-23
3. PEL Table 1A-3

; 1A-4 X ; 1A-5

; 1A-6

4. Range(s) to sonar (yards): 200 (from SQS-53A); 120 (from SQS-23)
5. Estimated SPL at range(s) in step 3 (from table/column in step 3): SPL1 = 201; SPL2 = 196
(per reminder, use SPL for 112 yard range)
Reminder: If range is between two values in the table, use the shorter range.
If the SPL is measured at the dive site, use the measured value.
6. Depth Reduction

0

dB

Reminder: 0 if not helmeted, see table in instructions if helmeted.
7. Corrected SPL (Step 5 minus Step 6)

SPL1 201 – 0 = 201 dB; SPL2 196 – 0 = 196 dB;

8. Estimated PEL at SPL (from table/column in step 3 of the appendix): PEL1 = 143 min; PEL 2 = 339 min
9. Duty Cycle Known: Yes
X
(do step 9); No
(stop)
		
Adjusted PEL for actual duty cycle
			
Actual DC % = 100 × 0.8 sec. (pulse length / 20 sec. (pulse repetition period)
			
Actual DC % = 4
			
Adjusted PEL = PEL (from step 8) 143 min. × 20 / actual duty cycle (%) 4 = 715 min.
			
PEL1 = 715 minutes; PEL2 = 339 minutes
Reminder: Do not adjust the PEL if duty cycle is unknown.
10. Multiple Sonars: Yes

X

(do step 10); No

(stop)

Sonar 1: 		
DT1 = 120 (Desired dive duration)
			PEL1 = 715 (from Step 8 or 9, as applicable)
			DT1/PEL1 = 120/715 = 0.17 .
Sonar 2:
DT1 = 120 (Desired dive duration)
			PEL1 = 339 (from Step 8 or 9, as applicable)
			DT1/PEL1 = 120/339 = .35 .
ND = 0.17 + 0.35 = 0.52 (This is less than 1.0, so dive is acceptable and may proceed.)
Reminder: The Noise Dose must not exceed a value of 1.0.
The dive time of 120 minutes is permitted because the ND is less than 1.0.

Figure 1A‑5. Sonar Safe Diving Distance/Exposure Time Worksheet (Completed Example).
APPENDIX 1A — Safe Diving Distances from Transmitting Sonar

1A-11

Table 1A‑3. Wet Suit Un-Hooded.

Permissible Exposure Limit (PEL) within a 24-hour period for exposure to AN/SQS-23, -26, -53, -56,
AN/BSY-1, -2 and AN/BQQ-5 sonars, including versions and upgrades. Exposure conditions shown
above the double line should be avoided except in cases of compelling operational necessity.
Estimated Ranges in yards for given SPL and PEL for sonar.

BSY-1
SQS-53C

BQQ-5
BSY-2
SQS-26CX(U)
SQS-53A, SQS-53B
SQS-56(U)

316
355
398
447
501
562
631
708
794
891

224
251
282
316
355
398
447
501
562
631

71
79
89
100
112
126
141
158
178
200

200
199
198
197
196
195
194
193
192
191

13
15
18
21
25
30
36
42
50
60

1,000
1,122
1,259
1,413
1,585
1,778
1,995
2,239
2,512
2,818
3,162
3,548
3,981
4,467
5,012
5,623

708
794
891
1,000
1,122
1,259
1,413
1,585
1,778
1,995
2,239
2,512
2,818
3,162
3,548
3,981

224
251
282
316
355
398
447
501
562
631
708
794
891
1,000
1,122
1,259

190
189
188
187
186
185
184
183
182
181
180
179
178
177
176
175

71
85
101
120
143
170
202
240
285
339
404
480
571
679
807
960

SQS-23
SQS-26AX
SQS-26BX, SQS-26CX
SQS-56

SPL

PEL

(dB)

(MIN)
A
V E
O X
I P
D O
		 S
T U
H R
I E
S

All ranges and SPLs are nominal.
*SPL is measured in dB/1 µPA at the dive site. To convert SPL for sound levels referenced to mbar,
subtract 100 dB from tabled levels.
(U) = upgrade

1A-12

U.S. Navy Diving Manual — Volume 1

Table 1A‑4. Wet Suit Hooded.

Permissible Exposure Limit (PEL) within a 24-hour period for exposure to AN/SQS-23, -26, -53, -56,
AN/BSY-1, -2, and AN/BQQ-5 sonar, including versions and upgrades. Exposure conditions shown
above the double line should be avoided except in cases of compelling operational necessity.
Estimated Ranges in yards for given SPL and PEL for sonar.

BSY-1
SQS-53C

BQQ-5
BSY-2
SQS-26CX(U)
SQS-53A, SQS-53B
SQS-56(U)

SQS-23
SQS-26AX
SQS-26BX, SQS26CX SQS-56

SPL

PEL

(dB)

(MIN)

56
63
71
79
89
100
112
126
141
158

40
45
50
56
63
71
79
89
100
112

13
14
16
18
20
22
25
28
32
35

215
214
213
212
211
210
209
208
207
206

13
15
18
21
25
30
36
42
50
60

178
200
224
251
282
316
355
398
447
501
562
631
708
794
891
1,000

126
141
158
178
200
224
251
282
316
355
398
447
501
562
631
708

40
45
50
56
63
71
79
89
100
112
126
141
158
178
200
224

205
204
203
202
201
200
199
198
197
196
195
194
193
192
191
190

71
85
101
120
143
170
202
240
285
339
404
480
571
679
807
960

A
V E
O X
I P
D O
		 S
T U
H R
I E
S

All ranges and SPLs are nominal.
*SPL is measured in dB/1 µPA at the dive site. To convert SPL for sound levels referenced to mbar,
subtract 100 dB from tabled levels.
(U) = upgrade

APPENDIX 1A — Safe Diving Distances from Transmitting Sonar

1A-13

Table 1A‑5. Helmeted.

Permissible Exposure Limit (PEL) within a 24-hour period for exposure to AN/SQS-23, -26, -53, -56,
AN/BSY-1, -2, and AN/BQQ-5 sonar, including versions and upgrades. Exposure conditions shown
above the double line should be avoided except in cases of compelling operational necessity.
Estimated Ranges in yards for given SPL and PEL for sonar.

BSY-1
SQS-53C

BQQ-5
BSY-2
SQS-26CX(U)
SQS-53A, SQS-53B
SQS-56(U)

SQS-23
SQS-26AX
SQS-26BX, SQS26CX SQS-56

SPL

PEL

(dB)

(MIN)

2,239
2,512
2,818
3,162
3,548
3,981
4,467
5,012
5,623
6,310

1,585
1,778
1,995
2,239
2,512
2,818
3,162
3,548
3,981
4,467

501
562
631
708
794
891
1,000
1,122
1,259
1,413

183
182
181
180
179
178
177
176
175
174

13
15
18
21
25
30
36
42
50
60

7,079
7,943
8,913
10,000
11,220
12,589
14,125
15,849
17,783
19,953
22,387
25,119
28,184
31,623
35,481
39,811

5,012
5,623
6,310
7,079
7,943
8,913
10,000
11,220
12,589
14,125
15,849
17,783
19,953
22,387
25,119
28,184

1,585
1,778
1,995
2,239
2,512
2,818
3,162
3,548
3,981
4,467
5,012
5,623
6,310
7,079
7,943
8,913

173
172
171
170
169
168
167
166
165
164
163
162
161
160
159
158

71
85
101
120
143
170
202
240
285
339
404
480
571
679
807
960

A
V E
O X
I P
D O
		 S
T U
H R
I E
S

All ranges and SPLs are nominal.
*SPL is measured in dB/1 µPA at the dive site. To convert SPL for sound levels referenced to mbar,
subtract 100 dB from tabled levels.
(U) = upgrade

1A-14

U.S. Navy Diving Manual — Volume 1

Table 1A‑6. Permissible Exposure Limit (PEL) Within a 24-hour Period for Exposure to AN/SQQ-14, -30,
‑32 Sonars.

Estimated Ranges in yards for given SPL and PEL for sonar.

WET SUIT UN-HOODED
SPL
(dB)

PEL
(MIN)

Range
(yards)

200
199
198
197
196
195
194
193
192
191
190
189
188

120
143
170
202
240
285
339
404
480
571
679
807
960

13
14
16
18
20
22
25
28
32
35
40
45
50

WET SUIT HOODED
SPL
(dB)

PEL
(MIN)

Range
(yards)

215
214
213
212
211
210
209
208
207
206
205
204
203

120
143
170
202
240
285
339
404
480
571
679
807
960

2
3
3
3
4
4
4
5
6
6
7
8
9

Dry suit helmeted divers: no restriction for these sonars. All ranges and SPLs are nominal.
*SPL is measured in dB/1 µPA at the dive site. To convert SPL for sound levels referenced to mbar,
subtract 100 dB from tabled levels.

APPENDIX 1A — Safe Diving Distances from Transmitting Sonar

1A-15

1A-5

GUIDANCE FOR DIVER EXPOSURE TO LOW-FREQUENCY SONAR (160–320 Hz)

If possible, you should avoid diving in the vicinity of low-frequency sonar (LFS).
LFS generates a dense, high-energy pulse of sound that can be harmful at higher
power levels. Because a variety of sensations may result from exposure to LFS, it
is necessary to inform divers when exposure is likely and to brief them regarding
possible effects; specifically, that they can expect to hear and feel it. Sensations
may include mild dizziness or vertigo, skin tingling, vibratory sensations in the
throat and abdominal fullness. Divers should also be briefed that voice communi­
cations are likely to be affected by the underwater sound to the extent that line pulls
or other forms of communication may become necessary. Annoyance and effects
on communication are less likely when divers are wearing a hard helmet (KM
37) diving rig. For safe distance guidance, contact NAVSEA (00C3). Tele­phone
numbers are listed in Volume 1, Appendix C.
1A-6

GUIDANCE FOR DIVER EXPOSURE TO ULTRASONIC SONAR (250 KHz AND
GREATER)

The frequencies used in ultrasonic sonars are above the human hearing threshold.
The primary effect of ultrasonic sonar is heating. Because the power of ultrasonic
sonar rapidly falls off with distance, a safe operating distance is 10 yards or greater.
Dive operations may be conducted around this type of sonar provided that the
diver does not stay within the sonar’s focus beam. The diver may finger touch
the transducer’s head momentarily to verify its operation as long as the sonar is
approached from the side.

1A-16

U.S. Navy Diving Manual — Volume 1

APPENDIX 1B

References
References

Subject

BUMEDINST 6200.15

Suspension of Diving During Pregnancy

BUMEDINST 6320.38

Hyperbaric Oxygen Treatment in Navy Recompression
Chambers

Manual of the Medical Department, Article 15-66

Medical Examinations

MILPERSMAN Article 1220

Military Personnel Manual

NAVEDTRA 10669-C

Hospital Corpsman 3 & 2

NAVFAC P-992

UCT Arctic Operations Manual

NAVMED P-5010

Manual of Naval Preventive Medicine

NAVSEA 10560 ltr

UBA Canister Duration

NAVSEA/00C ANU
http://www.supsalv.org/00c3_anu.asp

Authorization for Navy Use

NAVSEA (SS521-AA-MAN-010)

U.S. Navy Diving and Manned Hyperbaric System Safety
Certification Manual

NAVSEA Technical Manual (S0600-AA-PRO-010)

Underwater Ship Husbandry Manual

NAVSEA Technical Manual (SS500-HK-MMO-010)

MK 3 MOD 0 Light Weight Diving System Operating and
Maintenance

NAVSEA Technical Manual (SS500-AW-MMM-010)

MK 6 MOD 0 Transportable Recompression Chamber System
Operating and Maintenance

NAVSEA Technical Manual (SS600-AA-MMA-010)

MK 16 MOD 0 Operating and Maintenance

NAVSEA Technical Manual (SS600-AQ-MMO-010)

MK 16 MOD 1 Operating and Maintenance

NAVSEA Technical Manual (SS-600-A3-MMO-010)

MK 25 MOD 2 UBA Operating and Maintenance

NAVSEA Technical Manual (S9592-B1-MMO-010)

Fly Away Dive System (FADS) III Air System Operating and
Maintenance

NAVSEA Technical Manual (SS9592-B2-MMO-010)

Fly Away Dive System (FADS) III Mixed Gas System (FMGS)
Operating and Maintenance

NAVSEA Technical Manual (S9592-AN-MMO-010)

Emergency Breathing System Type I Operating and Maintenance

NAVSEA Technical Manual (0938-LP-011-4010)

Nuclear Powered Submarine Atmosphere Control Manual

NAVSEA Technical Manual (S9592-AY-MMO-020)

MK 5 MOD 0 Flyaway Recompression Chamber (FARCC)

NAVSEA Technical Manual (SS500-B1-MMO-010)

Standard Navy Double-Lock Recompression Chamber System

NAVSEA Technical Manual (SH700-A2-MMC-010)

Emergency Hyperbaric Stretcher Operations and Maintenance

NAVSEA Technical Manual (SS521-AJ-PRO-010)

Guidance for Diving in Contaminated Waters

Naval Ships Technical Manual, Chapter 74, Vol. 1
(S9086-CH-STM-010)

Welding and Allied Processes

APPENDIX 1B — References

Change A 1B-1

Naval Ships Technical Manual, Chapter 74, Vol. 3
(S9086-CH-STM-030)

Gas Free Engineering

Naval Ships Technical Manual, Chapter 262
(S9086-H7-STM-010)

Lubricating Oils, Greases, Specialty Lubricants, and Lubrication
Systems

Naval Ships Technical Manual, Chapter 550
(S9086-SX-STM-010)

Industrial Gases, Generating, Handling, and Storage

NAVSEA Operation & Maintenance Instruction
(0910-LP-001-6300)

Fly Away Diving System Filter/Console

NAVSEA Operation & Maintenance Instruction
(0910-LP-001-1500)

Fly Away Diving System Diesel Driven Compressor Unit EX 32
MOD 0, PN 5020559

Naval Safety Center Technical Manual

Guide to Extreme Cold Weather

NAVSEA Technical Manual (S0300-A5-MAN-010)

Polar Operations Manual

Office of Naval Research Technical Manual

Guide to Polar Diving

ASTM G-88-90

Standard Guide for Designing Systems for Oxygen Service

ASTM G-63-92

Standard Guide for Evaluating Nonmetallic Materials for Oxygen
Service

ASTM G-94-92

Standard Guide for Evaluating Metals for Oxygen Service

FED SPEC BB-A-1034 B

Diver’s Compressed Air Breathing Standard

FED SPEC A-A-59503

Compressed Nitrogen Standard

MIL-D -16791

Detergents, General Purpose (Liquid, Nonionic)

MIL-PRF-27210G

Oxygen, Aviators Breathing, Liquid and Gaseous

MIL-PRF-27407D

Propellant Pressurizing Agent Helium, Type I Gaseous Grade B

MIL-STD-438

Schedule of Piping, Valves and Fittings, and Associated Piping
Components for Submarine Service

MIL-STD-777

Schedule of Piping, Valves and Fittings, and Associated Piping
Components for Naval Surface Ships

MIL-STD-1330

Cleaning and Testing of Shipboard Oxygen, and Nitrogen
Systems Helium, Helium - Oxygen

MIL-STD-882

U.S. Department of Defense Standard Practice for System
Safety

OPNAVINST 3120.32C CH-1

Equipment Tag-Out Bill

OPNAVINST 3150.27 Series

Navy Diving Program

OPNAVINST 5100.19C, Appendix A-6

Navy Occupational Safety and Health (NAVOSH) Program
Manual for Forces Afloat

OPNAVINST 5100.23

Navy Occupational Safety and Health (NAVOSH) Afloat Program
Manual

OPNAVINST 5102.1C CH-1

Mishap Investigation and Reporting

OPNAVINST 8023.2C CH-1

U.S. Navy Explosives Safety Policies, Requirements, and
Procedures (Department of the Navy Explosives Safety Policy
Manual)

OSHA 29 CFR Part 1910

Commercial Diving Operations

MIL-PRF-17331

Lubricant (2190 TEP)

MIL-PRF-17672

Lubricant (2135 TH)

1B-2

U.S. Navy Diving Manual — Volume 1

ANSI-B57.1 and CSA-B96

American and Canadian Standard Compressed-Gas Cylinder
Valve Outlet and Inlet Connections

Z48.1

American National Standard Method of Marking Portable
Compressed-Gas Containers to Identify the Material Contained

CGA Pamphlet C-7

Guide to the Preparation of Precautionary Labeling and Marking
of Compressed Gas Cylinders

APPENDIX 1B — References

1B-3

PAGE LEFT BLANK INTENTIONALLY

1B-4

U.S. Navy Diving Manual — Volume 1

APPENDIX 1C

Telephone Numbers
Command

Department

Telephone

Fax

Naval Surface Warfare

Diver Life Support (Fleet Support

(850) 234-4482

(850) 234-4775

& Air Sampling

DSN: 436-4482

Center -Panama City, Florida
(NSWC-PC)
BUMED M95

(202) 762-3444

(202) 762-0931

(206) 526-6317

(206) 526-6329

Naval Sea Systems Command

(202) 781-XXXX

(202) 781-4588

(COMNAVSEASYSCOM)

DSN: 326-XXXX

National Oceanic and Atmospheric

HAZMAT

Administration (NOAA)

00C

Director

(202) 781-0731

00C1

Finance

(202) 781-0648

00C2

Salvage

(202) 781-2736

00C3

Diving

(202) 781-0934

00C4

Certification

(202) 781-0927

00C5

Husbandry

(202) 781-3453

Deep Submergence Systems

(202) 781-1467

Certification

(202) 781-1336

(Code OFP)

(202) 433-5596

Naval Sea Systems Command Code
07Q
NAVFAC Ocean Facilities Program

(202) 433-2280

DSN 288-5596

APPENDIX 1C — Telephone Numbers

Change A 1C-1

PAGE LEFT BLANK INTENTIONALLY

1C-2

U.S. Navy Diving Manual — Volume 1

APPENDIX 1D

List of Acronyms
ABS

Acrylonitrile Butadiene Styrene

ACF

Actual Cubic Feet

ACFM

Actual Cubic Feet per Minute

ACGIH

American Conference of Governmental Industrial Hygienists

ACLS

Advanced Cardiac Life Support

ADS

Advance Diving System

AGE

Arterial Gas Embolism

ALSS

Auxiliary Life-Support System

AM

Amplitude Modulated

ANU

Authorization for Navy Use/Authorized for Navy Use

AQD

Additional Qualification Designator

ARD

Audible Recall Device

AS

Submarine Tender

ASDS

Advanced SEAL Delivery System

ASRA

Air Supply Rack Assembly

ASME

American Society of Mechanical Engineers

ATA

Atmosphere Absolute

ATP

Ambient Temperature and Pressure

ATS

Active Thermal System

BC

Buoyancy Compensator

BCLS

Basic Cardiac Life Support

BIBS

Built-In Breathing System

BPM

Breaths per Minute

APPENDIX 1D — List of Acronyms

Change A 1D-1

1D-2

BTPS

Body Temperature, Ambient Pressure

BTU

British Thermal Unit

CDO

Command Duty Officer

CCTV

Closed-Circuit Television

CGA

Compressed Gas Association

CNO

Chief of Naval Operations

CNS

Central Nervous System

CONUS

Continental United States

COSAL

Coordinated Shipboard Allowance List

CPR

Cardiopulmonary Resuscitation

CRS

Chamber Reducing Station

CSMD

Combat Swimmer Multilevel Dive

CUMA

Canadian Underwater Minecountermeasures Apparatus

CWDS

Contaminated Water Diving System

DATPS

Divers Active Thermal Protection System

DC

Duty Cycle

DCS

Decompression Sickness

DDC

Deck Decompression Chamber

DDS

Deep Diving System

DDS

Dry Deck Shelter

DHMLS

Divers Helmet Mounted Lighting System

DLSE

Diving Life-Support Equipment

DLSS

Divers Life Support System

DMO

Dive Medical Officer

DMS

Dive Monitoring System

DMT

Diving Medical Technician
U.S. Navy Diving Manual — Volume 1

DOT

Department of Transportation

DRS

Dive Reporting System

DSI

Diving Systems International

DSM

Diving System Module

DSRG

Deep Submergence Review Group

DSRV

Deep Submergence Rescue Vehicle

DSSP

Deep Submergence System Project

DT

Dive Time or Descent Time

DT/DG

Dive Timer/Depth Gauge

DUCTS

Divers Underwater Color Television System

DV

Diver

DPV

Diver Propulsion Vehicle

EAD

Equivalent Air Depth

EBA

Emergency Breathing Apparatus

EBS I

Emergency Breathing System I

EDWS

Enhanced Diver Warning System

EEHS

Emergency Evacuation Hyperbaric Stretcher

EGS

Emergency Gas Supply

ENT

Ear, Nose, and Throat

EOD

Explosive Ordnance Disposal

EPs

Emergency Procedures

ESDS

Enclosed Space Diving System

ESDT

Equivalent Single Dive Time

ESSM

Emergency Ship Salvage Material

FADS III

Flyaway Air Dive System III

FAR

Failure Analysis Report

APPENDIX 1D — List of Acronyms

1D-3

1D-4

FARCC

Flyaway Recompression Chamber

FED SPEC

Federal Specifications

FFM

Full Face Mask

FFW

Feet of Fresh Water

FMGS

Flyaway Mixed-Gas System

FPM

Feet per Minute

FSW

Feet of Sea Water

FV

Floodable Volume

GFI

Ground Fault Interrupter

GPM

Gallons per Minute

HBO2

Hyperbaric Oxygen

HOSRA

Helium-Oxygen Supply Rack Assembly

HP

High Pressure

HPNS

High Pressure Nervous Syndrome

HSU

Helium Speech Unscrambler

ICCP

Impressed-Current Cathodic Protection

IDV

Integrated Divers Vest

IL

Inner Lock

ILS

Integrated Logistics Support

ISIC

Immediate Senior in Command

JAG

Judge Advocate General

J/L

Joules per Liter, Unit of Measure for Work of Breathing

KwHr

Kilowatt Hour

LB

Left Bottom

LCM

Landing Craft, Medium

LFA

Low Frequency Acoustic
U.S. Navy Diving Manual — Volume 1

LFS

Low Frequency Sonar

LP

Low Pressure

LPM

Liters per Minute

LS

Left Surface

LSS

Life Support System or Life Support Skid

LWDS

Light Weight Diving System

MBC

Maximal Breathing Capacity

MCC

Main Control Console

MD

Maximum Depth

MDSU

Mobile Diving and Salvage Unit

MDV

Master Diver

MEFR

Maximum Expiratory Flow Rate

MEV

Manual Exhaust Valve

MFP

Minimum Flask Pressure

MGCCA

Mixed-Gas Control Console Assembly

MIFR

Maximum Inspiratory Flow Rate

MIL-STD

Military Standard

MMP

Minimum Manifold Pressure

MP

Medium Pressure

MRC

Maintenance Requirement Card

MSW

Meters of Sea Water

MVV

Maximum Ventilatory Volume

NAVEDTRA

Naval Education Training

NAVFAC

Naval Facilities Engineering Command

NAVMED

Naval Medical Command

NAVSEA

Naval Sea Systems Command

APPENDIX 1D — List of Acronyms

1D-5

1D-6

ND

Noise Dose

NDSTC

Naval Diving and Salvage Training Center

NEC

Navy Enlisted Classification

NEDU

Navy Experimental Diving Unit

NEURO

Neurological Examination

NID

Non-Ionic Detergent

NITROX

Nitrogen-Oxygen

NMRI

Navy Medical Research Institute

NOAA

National Oceanic and Atmospheric Administration

NO-D

No Decompression

NPC

Naval Personnel Command

NRV

Non Return Valve

NSMRL

Navy Submarine Medical Research Laboratory

NSN

National Stock Number

NSTM

Naval Ships Technical Manual or NAVSEA Technical Manual

NSWC-PC

Naval Surface Warfare Center - Panama City

O&M

Operating and Maintenance

OBP

Over Bottom Pressure

OCEI

Ocean Construction Equipment Inventory

OIC

Officer in Charge

OJT

On the Job Training

OL

Outer Lock

OOD

Officer of the Deck

OPs

Operating Procedures

OSF

Ocean Simulation Facility

OSHA

Occupational Safety and Health Administration
U.S. Navy Diving Manual — Volume 1

PEL

Permissible Exposure Limit

PMS

Planned Maintenance System

PNS

Peripheral Nervous System

PP

Partial Pressure

PPCO2

Partial Pressure Carbon Dioxide

PPM

Parts per Million

PPO2

Partial Pressure Oxygen

PSI

Pounds per Square Inch

PSIA

Pounds per Square Inch Absolute

PSIG

Pounds per Square Inch Gauge

PSOB

Pre-Survey Outline Booklet

PTC

Personnel Transfer Capsule

PTS

Passive Thermal System

QA

Quality Assurance

RB

Reached Bottom

RCC

Recompression Chamber

REC

Re-Entry Control

RMV

Respiratory Minute Ventilation

RNT

Residual Nitrogen Time

ROV

Remotely Operated Vehicle

RQ

Respiratory Quotient

RS

Reached Surface

RSP

Render Safe Procedure

SAD

Safe Ascent Depth

SCA

System Certification Authority

SCF

Standard Cubic Feet

APPENDIX 1D — List of Acronyms

1D-7

1D-8

SCFM

Standard Cubic Feet per Minute

SCFR

Standard Cubic Feet Required

SCSCs

System Certification Survey Cards

SCUBA

Self Contained Underwater Breathing Apparatus

SDRW

Sonar Dome Rubber Window

SDS

Saturation Diving System

SDV

SEAL Delivery Vehicle

SEAL

Sea, Air, and Land

SET

Surface Equivalent Table

SEV

Surface Equivalent (percent or pressure)

SI

Surface Interval or System International

SLED

Sea Level Equivalent Depth

SLM

Standard Liters per Minute (short version used in formulas)

SLPM

Standard Liters per Minute

SNDB

Standard Navy Dive Boat

SOC

Scope of Certifications

SPL

Sound Pressure Level

SRDRS

Submarine Rescue and Diver Recompression System

SSB

Single Side Band

SSDS

Surface Supplied Diving System

STEL

Safe Thermal Exposure Limits

STP

Standard Temperature and Pressure

STPD

Standard Temperature and Pressure, Dry Gas

SUR D

Surface Decompression

SUR D AIR

Surface Decompression Using Air

SUR D O2

Surface Decompression Using Oxygen
U.S. Navy Diving Manual — Volume 1

T-ARS

Auxiliary Rescue/Salvage Ship

T-ATF

Fleet Ocean Tug

TBT

Total Bottom Time

TDCS

Tethered Diver Communication System

TDT

Total Decompression Time

TL

Transfer Lock

TLC

Total Lung Capacity

TLD

Thermal Luminescence Dosimeter

TLV

Threshold Limit Values

TM

Technical Manual

TMDER

Technical Manual Deficiency Evaluation Report

TRC

Transportable Recompression Chamber

TRCS

Transportable Recompression Chamber System

TTD

Total Time of Dive

UBA

Underwater Breathing Apparatus

UCT

Underwater Construction Team

UDM

Underwater Decompression Monitor

UQC

Underwater Sound Communications

UWSH

Underwater Ship Husbandry

VENTIDC

Vision Ear Nausea Twitching Irritability Dizziness
Convulsions

VTA

Volume Tank Assembly

VVDS

Variable Volume Dry Suit

WOB

Work of Breathing

YDT

Diving Tender

APPENDIX 1D — List of Acronyms

1D-9

PAGE LEFT BLANK INTENTIONALLY

1D-10

U.S. Navy Diving Manual — Volume 1

VOLUME 2

Air Diving
Operations
6

Operational Planning
and Risk Management

7

SCUBA Air Diving
Operations

8

Surface Supplied Air
Diving Operations

9

Air Decompression

10

Nitrogen-Oxygen
Diving Operations

11

Ice and Cold Water
Diving Operations

Appendix 2A

Optional Shallow Water
Diving Tables

Appendix 2B

U.S. Navy Dive Computer

Appendix 2C

Environmental and
Operational Hazards

Appendix 2D

Guidance for U.S. Navy
Diving on a Dynamic
Positioning Vessel

U.S. NAVY DIVING MANUAL

PAGE LEFT BLANK INTENTIONALLY

Volume 2 - Table of Contents
Chap/Para

Page

6

OPERATIONAL PLANNING AND RISK MANAGEMENT

6-1

INTRODUCTION.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 6-1

6-2

6-1.1

Purpose. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 6-1

6-1.2

Scope .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 6-1

6-1.3

Planning .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 6-2

MISSION ANALYSIS. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 6-2
6-2.1

Mission Analysis.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 6-2
6‑2.1.1
Underwater Ship Husbandry (UWSH).  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 6-2
6‑2.1.2
Search Missions.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 6-3
6‑2.1.3
Salvage/Object Recovery. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 6-3
6‑2.1.4
Harbor Clearance.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 6-4
6-2.1.5
Security Dives .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 6-5
6-2.1.6
Explosive Ordnance Disposal .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 6-5
6-2.1.7
Underwater Construction.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 6-6
6-2.1.8
Battle Damage Assessment and Repair (BDA/R) .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 6-6
6-2.1.9
Combat Diver.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 6-6
6-2.1.10 Dive Training .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 6-6
6-2.1.11 Free Ascent/Escape Training and Operations.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 6-6

6-2.2

Analyze Available Forces and Assets.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 6-7

6-2.3
6-3

6-4

6‑2.2.1

Dive Techniques.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 6-7

6‑2.2.2

Diving Craft and Platforms.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 6-9

Commanders Intent and Planning Guidance .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 6-12

COURSE OF ACTION DEVELOPMENT .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 6-12
6-3.1

Analyze Unit Strengths and Weaknesses.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 6-12

6-3.2

Generate Options.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 6-12

6-3.3

Develop Planning Assumptions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-12

COURSE OF ACTION ANALYSIS/RISK ASSESSMENT .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 6-13
6-4.1

COA Analysis .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 6-13

6-4.2

Risk Assessment. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 6-13
6‑4.2.1

6-5

Levels of ORM.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 6-14

TASK PLANNING AND EMERGENCY ASSISTANCE. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 6-17
6-5.1

Task Planning and Scheduling .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 6-17
6‑5.1.1
6‑5.1.2
6‑5.1.3

Table of Contents­—Volume 2

Task Schedule .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 6-17
Work-up Dives.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 6-17
Emergency Assistance.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 6-18

2–i

Chap/Para
6-6

Page
TRANSITION (EXECUTION) .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 6-21
6-6.1

Mission Brief.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 6-21

6-6.2

Dive Brief. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 6-22

6-6.3

Responsibilities While Operation is Underway.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 6-23
6‑6.3.1
6‑6.3.2
6‑6.3.3
6‑6.3.4

6-6.4

6-24
6-25
6-26
6-27

Post Dive/Post Mission.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 6-27
6‑6.4.1

Post-dive/Post Mission Debrief .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 6-28

7

SCUBA AIR DIVING OPERATIONS

7-1

INTRODUCTION.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-1

7-2

7-1.1

Purpose. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-1

7-1.2

Scope .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-1

7-1.3

References.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-1

OPERATIONAL CONSIDERATIONS.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-1
7-2.1

Operational Limits.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-1

7-2.2

Manning .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-4
7‑2.2.1
7‑2.2.2
7‑2.2.3
7‑2.2.4
7‑2.2.5
7‑2.2.6

7-3

Open-Circuit SCUBA. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-7
7‑3.1.1
7‑3.1.2

7-4

SCUBA Diving Supervisor .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-4
SCUBA Diver.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-5
Buddy Diver.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-5
Standby SCUBA Diver.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-6
Tenders. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-6
Other Personnel.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-7

MINIMUM EQUIPMENT FOR SCUBA OPERATIONS .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-7
7-3.1

Demand Regulator Assembly. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-8
Cylinders .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-11

7-3.2

Face Mask. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-13

7-3.3

Life Preserver.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-14

7-3.4

Buoyancy Compensator (BC).  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-14

7-3.5

Weight Belt.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-15

7-3.6

Knife .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-16

7-3.7

Swim Fins.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-16

7-3.8

Wrist Watch.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-16

7-3.9

Depth Gauge. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-16

OPTIONAL EQUIPMENT FOR SCUBA OPERATIONS. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-17
7-4.1

Protective Clothing .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-17
7‑4.1.1

2–ii

Situational Awareness (SA).  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Decision Making.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Fatigue.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Stress.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .

Wet Suits .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-17

U.S. Navy Diving Manual—Volume 2

Chap/Para

Page
7‑4.1.2

Variable Volume Dry Suits.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-18

7‑4.1.3

Gloves .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-19

7‑4.1.4

Writing Slate.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-19

7‑4.1.5

Signal Flare .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-19

7‑4.1.6

Acoustic Beacons. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-19

7‑4.1.7

Lines and Floats.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-19

7‑4.1.8

Snorkel.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-20

7‑4.1.9

Compass .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-20

7‑4.1.10 Dive Computers.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-20
7‑4.1.11
7-5

AIR SUPPLY.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-21
7-5.1

Duration of Air Supply.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-21

7-5.2

Methods for Charging SCUBA Cylinders .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-23

7-5.3

Operating Procedures for Charging SCUBA Tanks. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-25
7‑5.3.1

7-5.4
7-6

Topping off the SCUBA Cylinder .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-25

Safety Precautions for Charging and Handling Cylinders.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-26

PREDIVE PROCEDURES .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-27
7-6.1

Equipment Preparation.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-27
7‑6.1.1
7‑6.1.2
7‑6.1.3
7‑6.1.4
7‑6.1.5
7‑6.1.6
7‑6.1.7
7‑6.1.8
7‑6.1.9
7‑6.1.10
7‑6.1.11
7‑6.1.12
7‑6.1.13

7-7

Independent Secondary Air Source.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-20

Air Cylinders.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-27
Harness Straps and Backpack.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-28
Breathing Hoses.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-28
Regulator. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7-28
Life Preserver/Buoyancy Compensator (BC).  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-28
Face Mask .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-29
Swim Fins.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-29
Dive Knife.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-29
Snorkel .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-29
Weight Belt.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-29
Submersible Wrist Watch.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-29
Depth Gauge and Compass.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-29
Miscellaneous Equipment. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-30

7-6.2

Dive Brief.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-30

7-6.3

Donning Gear. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-30

7-6.4

Predive Inspection.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-31

WATER ENTRY AND DESCENT .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-32
7-7.1

Water Entry.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-32
7‑7.1.1

Step-In Method. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-32

7‑7.1.2

Rear Roll Method.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-36

7‑7.1.3

Front Roll Method. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-36

7‑7.1.4

Side Roll Method .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-36

7‑7.1.5

Entering the Water from the Beach .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-36

Table of Contents­—Volume 2

2–iii

Chap/Para

7-8

7-9

Page
7-7.2

In-Water Checks.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-37

7-7.3

Surface Swimming .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-38

7-7.4

Descent.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-38

UNDERWATER PROCEDURES .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-39
7-8.1

Breathing Technique.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-39

7-8.2

Mask Clearing.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-39

7-8.3

Regulator Clearing .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-39

7-8.4

Swimming Technique .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-40

7-8.5

Diver Communications .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-40
7‑8.5.1

Through-Water Communication Systems .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-40

7‑8.5.2

Hand and Line-Pull Signals .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-43

7-8.6

Working with Tools .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-43

7-8.7

Adapting to Underwater Conditions .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-44

7-8.8

Emergency Assistance/Procedures .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-44
7‑8.8.1

Emergency Equipment.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-45

7‑8.8.2

Emergency Procedures.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-45

7‑8.8.3

Actions Following an Emergency.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-49

ASCENT PROCEDURES .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-49
7-9.1

Ascent Procedures.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-49
7‑9.1.1

Buddy Breathing Procedure.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-49

7‑9.1.2

Emergency Free-Ascent Procedures.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-50

7-9.2

Ascent From Under a Vessel .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-50

7-9.3

Decompression.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-51

7-9.4

Surfacing and Leaving the Water.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-52

7-10 POSTDIVE PROCEDURES .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-52

8

SURFACE SUPPLIED AIR DIVING OPERATIONS

8-1

INTRODUCTION.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-1

8-2

8-1.1

Purpose. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-1

8-1.2

Scope .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-1

8-1.3

References.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-1

KM-37 NS.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-1
8-2.1

Operational Limits.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-1

8-2.2

Personnel .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-2
8‑2.2.1
8‑2.2.2
8‑2.2.3

2–iv

Watchstation Diving Officer .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-3
Master Diver Responsibilities.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-4
Dive Supervisor .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-4

U.S. Navy Diving Manual—Volume 2

Chap/Para

Page
8‑2.2.4
8‑2.2.5
8‑2.2.6
8‑2.2.7
8‑2.2.8
8‑2.2.9

8-3

KM-37 NS.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-7
8-3.1

Operation and Maintenance.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-7

8-3.2

Air Supply.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-7
8‑3.2.1
8‑3.2.2
8‑3.2.3

8-4

8-5

Console/Rack Operator.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-4
Standby Diver. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-5
Divers.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-5
Diver Tender.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-6
Log Keeper. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-6
Other Support Personnel.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-7

Pressure Requirements.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-7
Air Available Requirements .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-8
Emergency Gas Supply Requirements .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-11

MK 20 .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-14
8-4.1

Operation and Maintenance.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-14

8-4.2

Air Supply.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-14
8‑4.2.1

Emergency Gas Supply Requirements for MK 20 ESD.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-14

8‑4.2.2

Additional EGS Guidance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-15

PORTABLE SURFACE-SUPPLIED DIVING SYSTEMS .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-15
8-5.1

Divator DP. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-15
8‑5.1.1

DP Configurations .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-16

8-5.2

MK 3 Lightweight Dive System.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-18

8-5.3

Flyaway Dive System (FADS) III.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-19

8-5.4

Oxygen Regulator Console Assembly (ORCA). .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-20

8-6

SURFACE-SUPPLIED DIVING ACCESSORY EQUIPMENT. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-21

8-7

DIVER COMMUNICATIONS.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-23

8-8

8-7.1

Diver Intercommunication Systems. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-23

8-7.2

Line-Pull Signals.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-23

PREDIVE PROCEDURES .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-25
8-8.1

Setting a Moor. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-25

8-8.2

Dive Station Preparation.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-25

8-8.3

Air Supply Preparation .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-25

8-8.4

Line Preparation.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-26

8-8.5

Verify Environmental Conditions.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-26

8-8.6

Recompression Chamber Inspection and Preparation.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-26

8-8.7

Predive Inspection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-26

8-8.8

Donning Gear.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-26

8-8.9

Diving Supervisor Predive Checklist.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-26

Table of Contents­—Volume 2

2–v

Chap/Para
8-9

Page
WATER ENTRY AND DESCENT .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-26
8-9.1

Predescent Surface Check.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-26

8-9.2

Descent.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-27

8-10 UNDERWATER PROCEDURES. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-30
8-10.1

Adapting to Underwater Conditions .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-30

8-10.2

Movement on the Bottom .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-30

8-10.3

Searching on the Bottom. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-31

8-10.4

Working Around Corners. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-32

8-10.5

Working Inside a Wreck .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-32

8-10.6

Working with or Near Lines or Moorings.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-32

8-10.7

Bottom Checks.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-33

8-10.8

Working with Tools .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-33

8-10.9

Safety .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-33
8‑10.9.1 Fouled Umbilical. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-34
8‑10.9.2 Fouled Descent Lines. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-34
8‑10.9.3 Loss of Communications .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-34
8‑10.9.4 Loss of Gas Supply .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-35
8‑10.9.5 Falling. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-35
8‑10.9.6 Damage to Helmet and Diving Dress.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-35

8-10.10 Tending the Diver .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-35
8-10.11 Monitoring the Diver’s Movements.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-36
8-11

ASCENT PROCEDURES.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-36

8-12 SURFACE DECOMPRESSION .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-38
8-12.1

Surface Decompression Considerations. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-38

8-13 POSTDIVE PROCEDURES .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-38
8-13.1

Personnel and Reporting .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-38

8-13.2

Equipment.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-39

9

AIR DECOMPRESSION

9-1

INTRODUCTION.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-1
9-1.1

Purpose. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-1

9-1.2

Scope .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-1

9-2

THEORY OF DECOMPRESSION. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-1

9-3

AIR DECOMPRESSION DEFINITIONS.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-2
9-3.1

2–vi

Descent Time .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-2

U.S. Navy Diving Manual—Volume 2

Chap/Para

Page
9-3.2

Bottom Time .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-2

9-3.3

Total Decompression Time.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-2

9-3.4

Total Time of Dive.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-2

9-3.5

Deepest Depth .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-2

9-3.6

Maximum Depth .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-2

9-3.7

Stage Depth .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-2

9-3.8

Decompression Table.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-3

9-3.9

Decompression Schedule.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-3

9-3.10

Decompression Stop. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-3

9-3.11

No-Decompression (No “D”) Limit. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-3

9-3.12

No-Decompression Dive.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-3

9-3.13

Decompression Dive.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-3

9-3.14

Surface Interval.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-3

9-3.15

Residual Nitrogen.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-3

9-3.16

Single Dive .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-3

9-3.17

Repetitive Dive .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-3

9-3.18

Repetitive Group Designator. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-3

9-3.19

Residual Nitrogen Time. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-3

9-3.20

Equivalent Single Dive .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-4

9-3.21

Equivalent Single Dive Time.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-4

9-3.22

Surface Decompression.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-4

9-3.23

Exceptional Exposure Dive .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-4

9-4

DIVE CHARTING AND RECORDING .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-4

9-5

THE AIR DECOMPRESSION TABLES .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-6

9-6

GENERAL RULES FOR THE USE OF AIR DECOMPRESSION TABLES.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-7

9-7

9-6.1

Selecting the Decompression Schedule.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-7

9-6.2

Descent Rate .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-7

9-6.3

Ascent Rate. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-7

9-6.4

Decompression Stop Time .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-7

9-6.5

Last Water Stop .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-8

9-6.6

Eligibility for Surface Decompression.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-8

NO-DECOMPRESSION LIMITS AND REPETITIVE GROUP DESIGNATION TABLE
FOR NO-DECOMPRESSION AIR DIVES .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-8
9-7.1

9-8

Optional Shallow Water No-Decompression Table.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-9

THE AIR DECOMPRESSION TABLE. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-9
9-8.1

In-Water Decompression on Air .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-9

9-8.2

In-Water Decompression on Air and Oxygen.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-11

Table of Contents­—Volume 2

2–vii

Chap/Para

Page
9-8.2.1
9-8.2.2
9-8.3

Surface Decompression on Oxygen (SurDO2).  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-15
9-8.3.1
9-8.3.2

9-8.4
9-9

Procedures for Shifting to 100% Oxygen at 30 or 20 fsw. . . . . . . . . . . . . . . 9-13
Air Breaks at 30 and 20 fsw.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-13

Surface Decompression on Oxygen Procedure.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-16
Surface Decompression from 30 and 20 fsw.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-19

Selection of the Mode of Decompression.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-21

REPETITIVE DIVES.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-21
9-9.1

Repetitive Dive Procedure .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-23

9-9.2

RNT Exception Rule.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-29

9-9.3

Repetitive Air to Nitrogen-Oxygen EC-UBA or Nitrogen-Oxygen EC-UBA to Air Dives. 9-30

9-9.4

Order of Repetitive Dives .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-30

9-10 EXCEPTIONAL EXPOSURE DIVES .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-30
9-11

VARIATIONS IN RATE OF ASCENT .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-31
9-11.1

Travel Rate Exceeded. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-31

9-11.2

Early Arrival at the First Decompression Stop. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-31

9-11.3

Delays in Arriving at the First Decompression Stop .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-31

9.11.4

Delays in Leaving a Stop or Between Decompression Stops.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-32

9-12 EMERGENCY PROCEDURES.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-35
9-12.1

Bottom Time in Excess of the Table .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-35

9-12.2

Loss of Oxygen Supply in the Water. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-36

9-12.3

Contamination of Oxygen Supply with Air.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-37

9-12.4

CNS Oxygen Toxicity Symptoms (Non-convulsive) at 30 or 20 fsw Water Stop.  .  .  .  .  . 9-37

9-12.5

Oxygen Convulsion at the 30- or 20-fsw Water Stop .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-38

9-12.6

Surface Interval Greater than 5 Minutes.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-39

9-12.7

Decompression Sickness During the Surface Interval .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-40

9-12.8

Loss of Oxygen Supply in the Chamber.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-41

9-12.9

CNS Oxygen Toxicity in the Chamber. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-42

9-12.10 Asymptomatic Omitted Decompression .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
9-12.10.1 No-Decompression Stops Required. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
9-12.10.2 Omitted Decompression Stops at 30 and 20 fsw.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
9-12.10.3 Omitted Decompression Stops Deeper than 30 fsw .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .

9-43
9-44
9-44
9-45

9-12.11 Decompression Sickness in the Water.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-45
9-12.11.1 Diver Remaining in the Water .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-45
9-12.11.2 Diver Leaving the Water. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-46
9-13 DIVING AT ALTITUDE .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-46
9-13.1

Altitude Correction Procedure.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-47
9-13.1.1 Correction of Dive Depth .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-47
9-13.1.2 Correction of Decompression Stop Depth.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-47

9-13.2

2–viii

Need for Correction. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-49

U.S. Navy Diving Manual—Volume 2

Chap/Para

Page
9-13.3

Depth Measurement at Altitude. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-49

9-13.4

Equilibration at Altitude.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-49

9-13.5

Diving at Altitude Worksheet.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-52
9-13.5.1 Corrections for Depth of Dive at Altitude and In-Water Stops .  .  .  .  .  .  .  .  .  .  . 9-52
9-13.5.2 Corrections for Equilibration.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-52

9-13.6

Repetitive Dives .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-53

9-14 ASCENT TO ALTITUDE AFTER DIVING / FLYING AFTER DIVING.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-57
9-15 DIVE COMPUTER. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-58

10

NITROGEN-OXYGEN DIVING OPERATIONS

10-1 INTRODUCTION.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 10-1
10-1.1

Advantages and Disadvantages of NITROX Diving.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 10-1

10-2 EQUIVALENT AIR DEPTH.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 10-1
10-2.1

Equivalent Air Depth Calculation. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 10-2

10-3 OXYGEN TOXICITY.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 10-2
10-3.1

Selecting the Proper NITROX Mixture .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 10-3

10-4 NITROX DIVING PROCEDURES.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 10-3
10-4.1

NITROX Diving Using Equivalent Air Depths .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 10-3

10-4.2

SCUBA Operations.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 10-5

10-4.3

Special Procedures.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 10-5

10-4.4

Omitted Decompression.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 10-5

10-4.5

Dives Exceeding the Normal Working Limit .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 10-5

10-5 NITROX REPETITIVE DIVING.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 10-5
10-6 NITROX DIVE CHARTING.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 10-5
10-7 FLEET TRAINING FOR NITROX.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 10-7
10-8 NITROX DIVING EQUIPMENT.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 10-7
10-8.1

Open-Circuit SCUBA Systems .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 10-7
10‑8.1.1 Regulators .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 10-7
10‑8.1.2 Bottles .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 10-8

10-8.2

General.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 10-8

10-8.3

Surface-Supplied NITROX Diving.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 10-8

10-9 EQUIPMENT CLEANLINESS. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 10-8

Table of Contents­—Volume 2

2–ix

Chap/Para

Page

10-10 BREATHING GAS PURITY .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 10-9
10-11 NITROX MIXING.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 10-9
10-12 NITROX MIXING, BLENDING, AND STORAGE SYSTEMS.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 10-12

11

ICE AND COLD WATER DIVING OPERATIONS

11-1

INTRODUCTION.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 11-1

11-2

11-1.1

Purpose. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 11-1

11-1.2

Scope .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 11-1

11-1.3

References.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 11-1

OPERATIONS PLANNING.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 11-1
11-2.1

Planning Guidelines .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 11-1

11-2.2

Navigational Considerations.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 11-2

11-2.3

SCUBA Considerations.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 11-2

11-2.4

SCUBA Regulators.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 11-3
11‑2.4.1
11‑2.4.2

Special Precautions.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 11-4
Redundant Air Sources .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 11-4

11-2.5

Life Preserver.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 11-5

11-2.6

Face Mask. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 11-5

11-2.7

SCUBA Equipment.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 11-5

11-2.8

Surface-Supplied Diving System (SSDS) Considerations .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 11-5
11‑2.8.1 Advantages and Disadvantages of SSDS.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 11-6
11‑2.8.2 Effect of Ice Conditions on SSDS. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 11-6

11-2.9

Suit Selection .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 11-7
11‑2.9.1
11‑2.9.2
11‑2.9.3

Wet Suits .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 11-7
Variable Volume Dry Suits.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 11-7
Extreme Exposure Suits/Hot Water Suits. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 11-8

11-2.10 Clothing.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 11-8
11-2.11 Ancillary Equipment .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 11-9
11-2.12 Dive Site Shelter.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 11-9
11-3

2–x

PREDIVE PROCEDURES .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 11-10
11-3.1

Personnel Considerations.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 11-10

11-3.2

Dive Site Selection Considerations.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 11-10

11-3.3

Shelter. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 11-10

11-3.4

Entry Hole.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 11-10

11-3.5

Escape Holes .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 11-12

11-3.6

Navigation Lines.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 11-12

11-3.7

Lifelines.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 11-12

11-3.8

Equipment Preparation.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 11-12

U.S. Navy Diving Manual—Volume 2

Chap/Para
11-4

11-5

2A

Page
OPERATING PRECAUTIONS .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 11-13
11-4.1

General Precautions.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 11-13

11-4.2

Ice Conditions.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 11-13

11-4.3

Dressing Precautions .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 11-14

11-4.4

On-Surface Precautions.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 11-14

11-4.5

In-Water Precautions .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 11-15

11-4.6

Postdive Precautions .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 11-15

EMERGENCY PROCEDURES.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 11-15
11-5.1

Lost Diver .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 11-15

11-5.2

Searching for a Lost Diver. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-16

11-5.3

Hypothermia.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 11-16

OPTIONAL SHALLOW WATER DIVING TABLES

2A-1 INTRODUCTION.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2A-1

2B

U.S. NAVY DIVE COMPUTER

2B-1 INTRODUCTION.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2B-1
2B-1.1

Purpose. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2B-1

2B-1.2

Scope .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2B-1

2B-2 PRINCIPLES OF OPERATION. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2B-1
2B-2.1

Definitions.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2B-2

2B-2.2

Function .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2B-2

2B-2.3

Safety .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2B-3

2B-2.4

Advantages.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2B-3

2B-2.5

Disadvantages .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2B-3

2B-2.6

Use.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2B-4

2B-3 DIVING .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2B-5
2B-3.1

Pre-Dive .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2B-5

2B-3.2

Dive.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2B-5

2B-3.3

Ascent.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2B-6

2B-3.4

Decompression.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2B-6

2B-3.5

Post-Dive. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2B-6

2B-3.6

Time to Fly/Ascent to Altitude.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2B-7

2B-3.7

Repetitive Diving.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2B-7

2B-4 DIVING ISSUES/EPS.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2B-7
2B-4.1

Loss of NDC.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2B-7

Table of Contents­—Volume 2

2–xi

Chap/Para

Page
2B-4.2

Asymptomatic Omitted Decompression .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2B-7
2B‑4.2.1 In Water Stops Missed Without Surfacing.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2B-8
2B‑4.2.2 Inadvertent Surfacing with Missed Last or Only Stop. . . . . . . . . . . . . . . . . . 2B-8
2B‑4.2.3 Inadvertent Surfacing with Multiple Missed Stops.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2B-9

2C

2B-4.3

In-Water DCS.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2B-9

2B-4.4

Exceeds Limits .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2B-9

ENVIRONMENTAL AND OPERATIONAL HAZARDS

2C-1 ENVIRONMENTAL HAZARDS. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2C-1
2C-2 OPERATIONAL HAZARDS .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2C-11

2D

GUIDANCE FOR U.S. NAVY DIVING ON A DYNAMIC POSITIONING VESSEL

2D-1 INTRODUCTION.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2D-1
2D-2 DYNAMIC POSITIONING (DP) CAPABILITY .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2D-1
2D-2.1 DP Advantages.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2D-2
2D-2.2 DP Disadvantages .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2D-2
2D-2.3 DP Classification.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2D-3
2D-2.3.1 Classification Societies. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2D-3
2D-2.4 DP System Components. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2D-3
2D-2.4.1 Sensors .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2D-4
2D-2.4.2 Thrusters .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2D-4
2D-2.4.3 Control Stations.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2D-5
2D-2.4.4 Computers and Software.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2D-6
2D-2.4.5 Failure Modes and Effects Analysis.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2D-6
2D-2.4.6 DP Trials. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2D-6
2D-2.4.7 DP Status Lights and Alarms.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2D-6
2D-2.4.8 DP Vessel Communications.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2D-7
2D-2.4.9 Operations Plot and Emergency Plans .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2D-7
2D-2.4.10 Authority and Responsibility.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2D-7
2D-2.4.11 DP Casualties..  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2D-8
2D-3 GUIDELINES TO DETERMINE THE SUITABILITY OF A DP VESSEL. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2D-8
2D-3.1 VOO Selection..  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2D-8
2D-3.1.1 Vessel Suitability .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2D-8
2D-4 GUIDELINES FOR ESTABLISHING AN OPERATIONAL PLAN FOR THE DP VESSEL. .  .  . 2D-10
2D-5 SPECIFIC GUIDELINES FOR SURFACE SUPPLIED DIVING WHILE OPERATING FROM A
VESSEL IN THE DP MODE.. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2D-10

2–xii

U.S. Navy Diving Manual—Volume 2

Figure

Page
2D-5.1 Surface Supplied Diving.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2D-11
2D-5.2 Umbilical Management.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2D-11
2D-5.3 Surface Diving Requirements.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2D-12
2D-5.3.1 Additional Requirements .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2D-15
2D-5.4 Selection of DP Vessels of Opportunity for Diving Operations.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2D-16

List of Illustrations—Volume 2

2–xiii

Chap/Para

Page

PAGE LEFT BLANK INTENTIONALLY

2–xiv

U.S. Navy Diving Manual—Volume 2

Volume 2 - List of Illustrations
Figure

Page

6-1

Underwater Ship Husbandry Diving .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 6-3

6-2

Salvage Diving. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-4

6-3

Explosive Ordnance Disposal Diving. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-6

6-4

Underwater Construction Diving.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 6-8

6‑5

Dive Techniques .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 6-11

6‑6

Planning Data Sources.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 6-13

6-7

Link Between Time Critical and Deliberate.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 6-17

6‑8

Emergency Assistance Checklist. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-29

6‑9

Diving Planning ORM Worksheet .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 6-30

6‑10

Ship Repair Safety Checklist for Diving. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 6-33

7-1

Normal and Maximum Limits for SCUBA Diving.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-2

7-2

SCUBA General Characteristics . .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-3

7-3

Minimum Manning Levels for SCUBA Diving .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-4

7-4

Schematic of Demand Regulator. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-9

7-5

Full Face Mask .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-10

7-6

Typical Gas Cylinder Identification Markings. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-11

7-7

Life Preserver .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-15

7-8

Protective Clothing .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-18

7-9

Cascading System for Charging SCUBA Cylinders. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-25

7-10

SCUBA Entry Techniques.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-33

7-11

SCUBA Diving Operations Setup Checklist .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-34

7-12

Dive Supervisor Pre-Dive Checklist. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-37

7-13

Clearing a Face Mask.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-40

7-14

SCUBA Hand Signals .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-41

8-1

Normal and Maximum Limits for Surface Supplied Air Diving.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-2

8-2

Minimum Qualified Divers for Surface Supplied Air Diving Stations.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-3

8-3

KM-37 NS SSDS.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-6

8-4

KM-37 NS General Characteristics.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-9

8-5

MK 20 General Characteristics.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-13

8-6

MK 20 MOD 0 UBA.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-15

8-7

Divator DP General Characteristics. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-17

8‑8

MK 3 Lightweight Dive System.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-19

8-9

Flyaway Dive System (FADS) III.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-20

List of Illustrations—Volume 2

2–xv

Figure

2–xvi

Page

8-10

Oxygen Regulator Control Assembly (ORCA) II.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-21

8-11

Oxygen Regulator Control Assembly (ORCA) II Schematic .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-22

8-12

Communicating with Line-Pull Signals .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-22

8-13

Surface Supplied Diving Station Setup Checklist .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-28

8-14

Surface Decompression .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-37

9-1

Diving Chart. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-5

9‑2

Graphic View of a Dive with Abbreviations .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-6

9‑3

Completed Air Diving Chart: No-Decompression Dive .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-10

9‑4

Completed Air Diving Chart: In-water Decompression on Air .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-12

9‑5

Completed Air Diving Chart: In-water Decompression on Air and Oxygen.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-14

9‑6

Completed Air Diving Chart: Surface Decompression on Oxygen .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-18

9‑7

Decompression Mode Selection Flowchart.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-20

9‑8

Repetitive Dive Flow Chart .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-22

9‑9

Repetitive Dive Worksheet .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-24

9‑10

Completed Air Diving Chart: First Dive of Repetitive Dive Profile.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-26

9‑11

Completed Repetitive Dive Worksheet.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-27

9‑12

Completed Air Diving Chart: Second Dive of Repetitive Dive Profile .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-28

9‑13

Completed Air Diving Chart: Delay in Ascent deeper than 50 fsw. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-33

9‑14

Completed Air Diving Chart: Delay in Ascent Shallower than 50 fsw .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-34

9‑15

Diving at Altitude Worksheet.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-51

9‑16

Completed Diving at Altitude Worksheet.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-54

9‑17

Completed Air Diving Chart: Dive at Altitude.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-55

9‑18

Repetitive Dive at Altitude Worksheet.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-56

9‑19

Completed Repetitive Dive at Altitude Worksheet.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-59

9‑20

Completed Air Diving Chart: First Dive of Repetitive Dive Profile at Altitude. .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-60

9‑21

Completed Air Diving Chart: Second Dive of Repetitive Dive Profile at Altitude.  .  .  .  .  .  .  .  .  .  .  .  . 9-60

10‑1

NITROX Diving Chart .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 10-6

10‑2

NITROX SCUBA Bottle Markings .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 10-8

10‑3

NITROX O2 Injection System. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 10-10

10‑4

LP Air Supply NITROX Membrane Configuration.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 10-12

10‑5

HP Air Supply NITROX Membrane Configuration.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 10-13

11‑1

Two SCUBA Cylinders Fitted with Two Actual Redundant First Stage Regulators. .  .  .  .  .  .  .  .  .  .  . 11-3

11-2

Ice Diving with SCUBA .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 11-8

11-3

DRASH Brand 10-man Tent .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 11-9

11-4

Typical Ice Diving Worksite.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 11-11

U.S. Navy Diving Manual—Volume 2

Figure

Page

2B-1

Navy Dive Computer.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2B-1

2B-2

NDC Ascent Rate .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2B-6

2C‑1

Water Temperature Protection Chart.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2C-8

2C‑2

Environmental Assessment Worksheet.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2C-10

2C‑3

International Code Signal Flags .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2C-16

2D‑1

DP Diving Vessel.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2D-1

2D‑2

DP Component Terminology.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2D-5

2D‑3

DP Pilot Seat.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2D-5

2D‑4

Alarm Panel.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2D-6

2D‑5

Safe Distance Chart .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2D-12

2D‑6

Illustration of Maximum Umbilical Lengths .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2D-16

2D‑7

Illustration of Maximum Umbilical Lengths..  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2D-18

2D‑8

Vessel Section Checklist for Navy Surface Supplied Diving Operations from a DP Vessel..  .  . 2D-21

2D‑9

Pre Dive Check List for Navy Surface Supplied Diving Operations from a DP Vessel.  .  .  .  .  .  . 2D-22

List of Illustrations—Volume 2

2–xvii

Chap/Para

Page

PAGE LEFT BLANK INTENTIONALLY

2–xviii

U.S. Navy Diving Manual—Volume 2

Volume 2 - List of Tables
Table

Page

6‑1

Navy Recompression Chamber Support Levels.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 6-20

6‑2

Air Diving Recompression Chamber Recommendations (Bottom Time in Minutes).  .  .  .  .  .  .  .  .  . 6-20

7‑1

Sample SCUBA Cylinder Data .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-12

8‑1

KM-37 NS Overbottom Pressure Requirements.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-8

8‑2

Line-Pull Signals.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-24

9‑1

Pneumofathometer Correction Factors.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-7

9‑2

Management of Extended Surface Interval and Type I Decompression
Sickness during the Surface Interval.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-41

9‑3

Management of Asymptomatic Omitted Decompression. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-43

9‑4

Sea Level Equivalent Depth (fsw).  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-48

9‑5

Repetitive Groups Associated with Initial Ascent to Altitude .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-50

9‑6

Required Surface Interval Before Ascent to Altitude After Diving .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-62

9‑7

No-Decompression Limits and Repetitive Group Designators for
No-Decompression Air Dives.. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-63

9‑8

Residual Nitrogen Time Table for Repetitive Air Dives .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-64

9‑9

Air Decompression Table. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-65

10‑1

Equivalent Air Depth Table .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 10-4

10‑2

Oil Free Air. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 10-11

2A‑1

No-Decompression Limits and Repetitive Group Designators for Shallow Water
Air No-Decompression Dives .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2A-2

2A‑2

Residual Nitrogen Time Table for Repetitive Shallow Water Air Dives .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2A-3

2B‑1

NDC Characteristics .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2B-4

2B‑2

Initial Management of Asymptomatic Omitted Decompression for NDC Dives.  .  .  .  .  .  .  .  .  .  .  .  .  . 2B-8

2C-1

Equivalent Wind Chill Temperature Chart.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2C-2

2C-2

Sea State Chart.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2C-4

2C-3

Bottom Conditions and Effects Chart .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2C-6

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2–xix

Chap/Para

Page

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2–xx

U.S. Navy Diving Manual—Volume 2

CHAPTER 6

Operational Planning
and Risk Management
6-1

INTRODUCTION
6-1.1

Purpose. This chapter outlines a process to plan and execute diving operations that

integrates Operational Risk Management (ORM) and the Navy Planning Process
(NPP).

6-1.2

Scope. Navy diving units plan dive missions IAW the Navy Planning Process

(NWP 5-01) or ISIC guidance. ORM shall be applied to dive operations and training in accordance with OPNAV INSTRUCTION 3500.39 (series). This chapter is
focused on planning at the unit level and ORM at the point of execution.
The worksheets and checklists contained in this chapter are examples of U.S. Navy
material. They may be used as provided or modified locally to suit specific needs.
References cited in this chapter:
n Navy Planning Process. NWP 5-01.
n Operational Risk Management. OPNAVINST 3500.39(series).
n NAVSEA Underwater Ship Husbandry Manual. S0600-­AA­-PRO-­010.
n U.S. Navy Salvage Manual. S0300-A6-MAN-010 (010 – 040).
n Emergency Ships Salvage Material Catalog. NAVSEA S0300-BV-CAT (Vol
I - II)

n Conventional Underwater Construction and Repair Techniques NTRP
4-04.2.8
n Expedient Underwater Repair Techniques. NTRP 4-04.2.9
n UCT Arctic Operations Manual. NAVFAC P-992.
n Multi Service Tactics, Techniques, and Procedures for Military Diving
Operations. NTTP 3-07.7.
n Navy Diving Program. OPNAVINST 3150.27 (series).
n Navy Mission Essential Task List.
n Guidance for Diving in Contaminated Waters. SS521-AJ-PRO-010.
n Radiological Control Manual for Ships. S9123-33-MMA-000-V.

CHAPTER 6 — Operational Planning and Risk Management

6-1

n Shipyard Radiological Control Manual. NAVSEA 389-0288.
n A Navy Diving Supervisor’s Guide to the Non-technical Skills Required for
Safe and Productive Diving. NEDU TR 05-09.
6-1.3

Planning. The Navy Planning Process consists of six steps:

n Mission Analysis
n Course of Action Development
n COA Analysis/Risk Assessment
n COA Comparison and Decision (not discussed - see NWP 5-01)
n Task Planning/Emergency Assistance (Modified from NPP’s Plans and
Orders Development)
n Transition (Execution)
When tasked with a dive mission, leaders must resist the urge to jump ahead to a
presumed course of action (COA) without the benefits of deliberate planning.
6-2

MISSION ANALYSIS
6-2.1

Mission Analysis. Mission analysis drives the planning process and is tailored to

the situation, time available, and the commander’s guidance. It gives an overall
assessment of the situation and takes into account the area of operations and the
operating environment.
A common failure when planning an operation is to place excessive emphasis on the
actual diving phases, while not fully considering pre-dive and post-dive activities
(transit to and from operating area, habitability issues, resupply...).

All dive planning must take into account that bottom time is at a premium. Planning
efforts that reduce the required bottom time and increase diver effectiveness are
critical (e.g., use of tools to limit underwater searching by divers such as underwater
imaging systems and sidescan SONAR).
Diving tasks/missions involve the following:
6-2.1.1

Underwater Ship Husbandry (UWSH). UWSH is the inspection, maintenance, and
repair of ship and submarine hulls and appendages while the vessel is waterborne
(Figure 6-1). The objective of UWSH is to produce a permanent repair without
drydocking the vessel.

NAVSEA 00C is the technical warrant holder for UWSH procedures and equipment.
Divers performing UWSH tasks shall be trained and qualified for the work they
are performing IAW NAVSEA Underwater Ship Husbandry Manual (S0600-AAPRO-010) and Personnel Qualification Standards (PQS). Divers shall follow strict
Quality Assurance (QA) procedures IAW the Joint Fleet Maintenance Manual
6-2

U.S. Navy Diving Manual — Volume 2

and NAVSEA Underwater Ship Husbandry Manual and work closely with the
maintenance activity QA department and planners to ensure repairs comply with
ship design specifications.
If divers do not have a NAVSEA 00C approved procedure with which to accomplish
a repair, they shall contact NAVSEA 00C to obtain technical approval prior to
commencement of the repair. Dive Units shall not permit use of equipment in the
water unless it is included on the ANU list or listed in the NAVSEA UWSH manual.
NAVSEA 00C5 provides maintenance activities with onsite technical representatives
to assist in complex repairs or new procedures. NAVSEA 00C5 can be reached at
the contact information listed on SUPSALV’s website (http://www.supsalv.org/).

Figure 6-1. Underwater Ship Husbandry Diving.

6-2.1.2

6-2.1.3

Search Missions. Underwater searches are conducted to locate underwater objects
or subsurface geological formations. Searches can be performed by various
methods depending on the undersea terrain and purpose of the mission. Because
using divers for an unaided visual search over a large area is time consuming
and labor intensive, this type of search operation should incorporate the use of
sidescan sonar and other search equipment whenever possible. Remotely Operated
Vehicles (ROVs) may be used to extend searches into deep waters and areas that
are particularly dangerous for a diver.
Salvage/Object Recovery. Divers work to recover sunken or wrecked naval
craft, submersibles, downed aircraft, and human remains (Figure 6-2). Salvaged
items may include classified or sensitive materials. Although they share common

CHAPTER 6 — Operational Planning and Risk Management

6-3

aspects, no two salvage efforts are alike and the hazards from these operations
must never be taken for granted.

Figure 6-2. Salvage Diving. Surface-supplied divers on an aircraft recovery mission.

Operations involving the recovery of an object from the bottom require knowledge
of the dimensions and weight of the object. Other useful information includes
floodable volume, established lifting points, construction material, length of time
on the bottom, probable degree of embedment in mud or silt, and the nature and
extent of damage. This data helps determine the type of lift to be used (e.g., boom,
floating crane, lifting bags, pontoons), indicates whether mud suction may be
an issue (high-pressure hoses may be needed to jet away mud or silt) and helps
determine the disposition of the object after it is brought to the surface. Preliminary
planning may find the object too heavy to be placed on the deck of the support ship,
indicating the need for a barge and heavy lifting equipment. Planning resources
include the U.S. Navy Salvage manuals, Emergency Ships Salvage Material
(ESSM) catalog and the salvage experts at NAVSEA 00C2.
6-2.1.4

Harbor Clearance. Harbor clearance involves port/harbor facilities opening,
construction, clearance, and rehabilitation. Port facilities are fundamental to the
movement of personnel and material for any military operation. Port facilities
can either be improved for friendly forces or modified to deny use by the enemy.
Harbor clearance may involve:
1. Planning and Inspection. Divers assist in the planning of any port operation

to help determine priorities of work or prepare work estimates. A completed
inspection can provide the terminal commander with a report of existing
conditions of underwater port facility structures.

2. Hydrographic/Bathymetric Survey. Hydrographic surveys of the proposed area

are conducted to determine water depths, sea-bottom contours, and the location

6-4

U.S. Navy Diving Manual — Volume 2

of shipping channels and underwater obstacles. Divers conduct surveys to
depict water depths and obstruction locations to determine the size of ship the
port can support.
3. Clearance. Clearance operations are undertaken to neutralize or reduce

obstacles blocking the shipping channels in ports, loading facilities, mooring
sites, marine railways, dry-dock facilities, lock and dam structures, and other
navigable waterways.

4. Repair. Repairing port facilities is more desirable than initial construction

because it requires far less time and fewer resources. The repair may involve
both underwater and surface operations and will depend on the close integration
of both divers and general engineer assets. The inspection and repair of these
structures may require specialized equipment.

6-2.1.5

Security Dives. Security dives are conducted to search for underwater explosives

or other devices that may have been attached to ships or piers. All qualified divers
may conduct security dives. If an explosive device is found, the area shall be
quarantined. Only EOD personnel may attempt to handle or dispose of underwater
explosives devices.

6-2.1.6

Explosive Ordnance Disposal. Explosive Ordnance Disposal divers perform tasks

including recovering, identifying, disarming, and disposing of explosive devices
from harbors, ships, and sea-lanes (Figure 6-3). Diving in the vicinity of ordnance
combines the hazards of diving and ordnance. EOD divers shall accomplish diving
to investigate, render safe, or dispose of explosive ordnance found underwater,
regardless of type or fusing.

Figure 6-3. Explosive Ordnance Disposal Diving. An EOD diver using handheld sonar to
locate objects underwater.

CHAPTER 6 — Operational Planning and Risk Management

6-5

6-2.1.7

Underwater Construction. Underwater construction is the construction, inspection,

repair, and removal of in-water facilities in support of military operations. An inwater facility can be defined as a structure, system, device, or utility adjacent to,
floating upon, or submerged in a freshwater or marine environment to include in
shore rivers and lakes. Pipelines, cables, sensor systems, and fixed/advanced­base
structures are examples of in-water facilities (Figure 6-4). More information on
ocean construction may be obtained from NAVFAC Ocean Facilities Program
managers. Underwater construction planning resources can be found in:
n UCT Conventional Inspection and Repair Techniques Manual NTRP
4-04.2.8
n Expedient Underwater Repair Techniques NTRP 4-04.2.9
n UCT Arctic Operations Manual NAVFAC P-992
6-2.1.8

Battle Damage Assessment and Repair (BDA/R). BDA/R involves UWSH in a

remote, semi-permissive/permissive operating environment, which may require
UWSH units to be prepared for immediate worldwide deployment.
6-2.1.9

Combat Diver. Combat divers conduct reconnaissance and neutralization of

enemy ships, shore-based installations, and personnel. Some missions may require
an underwater approach to reach coastal
installations undetected. Reconnaissance
missions and raids may expose the combat
divers to additional risk but may be necessary
to advance broader warfare objectives.

6-2.1.10

Dive Training. Initial dive training occurs

at Naval Diving Salvage Training Center
(NDSTC), Panama City Florida and Basic
Underwater Demolition School (BUDS),
Coronado California. Advanced dive
training occurs throughout the Fleet in
various locations and by Type Commander
(TYCOM) specific training units. Training
is also conducted by unit level personnel and
with foreign divers during Theater Security
Cooperation exercises (TSCs). Planning for
training conducted outside of formal venues
is vital since it represents a high degree of
risk. OPNAVINST 1500.75(series) governs
the conduct of high risk training.

6-2.1.11

Free
Ascent/Escape
Training
and
Operations. Free ascent operations are

conducted by trained and qualified divers.
Free ascent/escape training is conducted by

6-6

Figure 6-4. Underwater
Construction Diving.

U.S. Navy Diving Manual — Volume 2

qualified high risk instructors under approved training plans IAW OPNAVINST
1500.75 (series).
No ascent training may be conducted unless fully qualified instructors are present, a
recompression chamber is available within 5 minutes, a Diving Medical Technician
is on station, and a Diving Medical Officer is able to provide immediate response
to a mishap.
6-2.2

Analyze Available Forces and Assets. An initial analysis of forces available

to complete the identified tasks is conducted and any modifications to the task
organization and support relationships are considered. This step should also
identify any critical shortfalls in subject matter expertise.

Some examples of available forces and assets (in addition to organic forces and
assets) include an underwater hydrographic survey team, pollution response
team, light weight diving system, deep diving saturation system, EOD team,
Mobile Diving and Salvage Company (MDS CO), or a port security team. The
Multi Service Tactics, Techniques, and Procedures for Military Diving Operations
(MDO) (NTTP 3-07.7) is a valuable resource in determining what resources may
be available from other services and their capabilities.
6-2.2.1

Dive Techniques. (Figure 6-5) A dive mission may be accomplished with one or

more dive techniques. Selection of diving technique may depend upon:
n Timeliness of the mission
n Availability of equipment
n Availability of trained personnel

Techniques may have more than one mode of operation (ex. Surface Supplied
Diving conducted with air or helium/oxygen mix). Planners should be familiar
with the equipment and modes being considered and may refer to the applicable
chapters in this manual for detailed manning requirements, operational limits,
and additional information. Depth limits shall not be exceeded without specific
approval in accordance with the OPNAVINST 3150.27 (series). Diving techniques
include self contained apparatus, surface supplied diving, saturation diving, and
breath-hold diving.
1. Self-Contained Apparatus. Free swimming self-contained apparatus available

to diving units encompass open and closed circuit underwater breathing
apparatus. Self-contained apparatus are best suited for short no-decompression
dives, in relatively warm water, and in depths shallower than 100fsw where
light work or inspection is anticipated. Each condition outside of these norms
increases risk. Self-contained apparatus may employ air, NITROX, 100 percent
oxygen, or mixed gas (HEO2) modes of operation.

The portability and ease in which Self-Contained Apparatus can be employed are
distinct advantages. Self-contained equipment can be transported easily and put
into operation with minimum delay. Self-contained apparatus offers flexible and

CHAPTER 6 — Operational Planning and Risk Management

6-7

economical methods for accomplishing a range of tasks. However, bottom time
may be limited by the fixed breathing gas supply or absorbent canister duration,
which is depleted more rapidly when diving deep or working hard.
2. Surface Supplied Diving. Surface supplied diving involves a full face or

helmeted diving apparatus, an air or gas supply system, and an umbilical that
allows for communications and carries the breathing medium from the supply
system to the diver.

Surface-supplied diving systems can be divided into two major categories:
lightweight gear (MK 20 with DP or MK III LWDS), and deepsea gear (KM-37
NS with FADS III or FMGS).
The primary use for surface supplied gear is bottom work in depths up to 190fsw,
UWSH on ships and submarines, and bottom work in depths up to 300fsw.
Deep sea gear should be used for jobs involving underwater rigging, heavy work,
during use of pneumatic or hydraulic powered underwater tools, diving in areas
with strong currents, and any situations where more physical protection is desired.
3. Saturation Diving. Saturation diving is employed in deep salvage and submarine

rescue/recovery and is designed to support diving up to 1000fsw for extended
periods of time. Saturation diving offers a high return on bottom time verses
decompression. However, saturation diving requires substantial resources,
planning, and coordination. Saturation Diving may be a better choice over SSD
even at shallower depths for long duration missions or operations requiring
extended bottom times.

4. Breath-hold Diving. Breath-hold diving is a dangerous practice that may lead

to unconsciousness and death and shall be limited to operations and training
that cannot be effectively accomplished with UBA such as, free ascent and
escape training, SCUBA confidence training, shallow water inspections or
object recovery, and obstacle/ordnance clearance.

WARNING.		

The practice of hyperventilating for the purpose of “blowing off” carbon
dioxide, (as differentiated from taking two or three deep breaths) prior to
a breath-hold dive is a primary cause of unconsciousness and may lead
to death. Breath-hold divers shall terminate the dive and surface at the
first sign of the urge to breathe. See paragraph 3-5.5 for more information
about hyperventilation and unconsciousness from breath-hold diving.

Breath-hold diving shall be supervised by a qualified Diving Supervisor and the
breath-hold diver(s) shall be tended where practical. ORM, dive briefs, emergency
action plans, and notifications relevant to Navy dives apply to breath-hold diving.
Breath-hold mishaps and near-misses during authorized operations, involving
personnel qualified as Navy Divers in any capability, are deemed diving incidents
and shall be reported as such.
6-2.2.2

Diving Craft and Platforms. Support craft are often required to support diving

operations. Typical diving platforms / Vessels of Opportunity (VOO):

6-8

U.S. Navy Diving Manual — Volume 2

1. Auxiliary Rescue/Salvage Ship (T-ARS) (Safeguard Class). T-ARSs are

operated by the Military Sealift Command. The mission of the T-ARS ship is
to assist disabled ships, debeach stranded vessels, fight fires alongside other
ships, lift heavy objects, recover submerged objects, tow other vessels, and are
outfitted with a recompression chamber and diving system to support manned
diving operations. The T-ARS class ships may carry a complement of divers
to perform underwater ship husbandry tasks and salvage operations as well as
underwater search and recovery.

2. Ocean Tugs. Ocean tugs make excellent diving platforms due to their large

open deck space but do not have many of the capabilities of the T-ARS vessels
such as the lifting capabilities to retrieve heavy wreckage onto their decks.
Fleet ocean tugs (T-ATF) operated by the Military Sealift Command have
civilian crews and are augmented with military communications detachments
but do not have any organic diving capability. In addition to towing, these large
ocean-going tugs can also rig debeaching gear.

3. Diving Tender (YDT). YDTs are used to support shallow-water diving

operations. Additionally, a wide variety of Standard Navy Dive Boats (SNDB),
LCM-8, LCM-6, 50-foot work boats, and other yard craft have been fitted with
surface-supplied dive systems.

4. Submarine Tender (AS). Submarine tenders are designed specifically for

servicing nuclear-powered submarines. Submarine tenders support underwater
ship husbandry and are equipped with a recompression chamber.

5. Small Craft. Open and closed circuit free swimming diving operations are

typically conducted from small craft. Small craft can range from an inflatable
rubber raft with an outboard engine to a small landing craft. Small boat operators
(coxswains) must understand diving procedures and be aware of the location of
divers/swimmers at all times.

Diving Supervisors must understand the limitations of their craft and avoid
underestimating the vulnerabilities of operating small craft in open seas. The
difficulties of launching and recovering divers and transiting in increased sea states
can hamper the ability to operate safely.
6. Other Support Craft. Support craft, including barges, tugs, floating cranes, or

vessels and aircraft for area search may be needed, depending on the scope of
the operation. The need for additional equipment should be anticipated as far
in advance as possible to allow time for leases/contracts and scheduling.

Regardless of the ownership or size, all craft used for diving operations shall:
n Be seaworthy
n Include Coast Guard required lifesaving and other safety gear
n Have a reliable engine (unless it is a moored platform or barge)
n Provide ample room for the divers to dress
n Be able to carry all diving safety equipment required for the operation

CHAPTER 6 — Operational Planning and Risk Management

6-9

n Have a well-trained crew
n Carry other safety equipage as required by the unit SOP. (Binoculars, water,
charts, etc.)
NOTE:

6-10

Dynamic Positioning (DP) Capability. Some vessels possess dynamic
positioning (DP) capability. DP uses the ship’s propulsion systems
(thrusters, main propulsion, and rudders) to maintain a fixed position.
Surface-supplied diving and saturation diving, dynamic positioning (DP)
ships shall meet International Maritime Organization (IMO) Class 2 or 3
standards. IMO Equipment Class 2 or 3 will maintain automatic or manual
position and heading control under specified maximum environmental
conditions, during and following any single-point failure of the DP
system. See Appendix 2D, Guidance for U.S. Navy Diving on a Dynamic
Positioning Vessel, for conducting diving operations from a DP vessel.

U.S. Navy Diving Manual — Volume 2

Figure 6‑5. Dive Techniques

CHAPTER 6 — Operational Planning and Risk Management

6-11

6-2.3

Commanders Intent and Planning Guidance. The Commander’s Intent is a broad

expression of:

n Purpose of the mission.
n Methods of the operation.
n Desired end state.
The Commander’s Intent is important because the commander may require a quick
removal of a vessel blocking a valuable pier with little concern for preservation
of the vessel, or the priority may be protection of the marine environment. The
Commander’s Intent focuses leaders on a common goal and allows flexibility and
freedom of action.
The Commander’s intent frames planning guidance. Planning guidance focuses
COA development.
6-3

COURSE OF ACTION DEVELOMENT

A COA is any concept of operation that accomplishes the mission. When possible,
the entire team should be involved in COA development.
6-3.1

Analyze Unit Strengths and Weaknesses. Planners gain insight into capabilities

relative to the operation by analyzing unit strengths and weaknesses and identify
what additional resources may be required to execute the mission. To determine
capability planners evaluate:
n Personnel levels.
n Training and proficiency.
n Equipment readiness.
n Human factors.
6-3.2

Generate Options. The goal of COA development is to develop several

appropriate COAs. COAs must look at possibilities created by attachments, such
as a hydrographic survey team or an area search detachment (Figure 6-6). Planners
should avoid the pitfall of presenting one good COA among several throwaway
COAs. Brainstorming requires time and imagination but produces the greatest
range of options. Remaining open minded in generating options avoids bias.
6-3.3

6-12

Develop Planning Assumptions. Assumptions are made in areas over which there
is no control. Assumptions should be validated prior to the mission execution.
Unvaildated assumptions become part of the inherent risk of the operation and the
dive supervisor must have a plan to deal with them.

U.S. Navy Diving Manual — Volume 2

PLANNING DATA SOURCES


Aircraft Drawings



Light Lists



Ship’s Personnel



Cargo Manifest



Local Yachtsmen/Fishermen





Coastal Pilot Publications



LORAN Readings

Ships Drawings (including docking
plan)



Cognizant Command



Magnetometer Plots



Side-Scan Sonar Plots



Communications Logs



Navigation Text
(Dutton's/Bowditch)



SINS Records



SITREP



Construction Drawings



Current Tables



Navigational Charts



Sonar Readings and/or Charts



Diving Advisory Messages



NAVOCEANO Data



TACAN Readings



DRT Tracks



Notices to Mariners



Technical Reference Books



DSV/DSRV Observations



OPORDERS



Test Records



Electronic Analysis



Photographs



Tide Tables



Equipment Operating Procedures
(OPs)



Radar Range and Bearings



Underwater Work Techniques



RDF Bearings



USN Diving Manual Reference List



Equipment Operation and Maintenance Manuals



ROV Video and Pictures



USN Instructions



Sailing Directions



USN Ship Salvage Manual



Eyewitnesses



Salvage Computer Data



Visual Bearings



Flight or Ship Records



Ship’s Curves of Forms



Weather Reports



Flight Plan



Ship’s Equipment



Hydrographic Publications



Ship’s Logs and Records

Figure 6‑6. Planning Data Sources.

6-4

COURSE OF ACTION ANALYSIS/RISK ASSESSMENT
6-4.1

COA Analysis. COA analysis:

n Anticipates the operational environment.
n Determines conditions and resources required for success.
n Assesses the degree of flexibility for each COA.
6-4.2

Risk Assessment. A risk assessment shall be conducted and documented for each

diving mission. The Planning and ORM worksheet (Figure 6-9) may be used to
document efforts. Additional resources are available on the Naval Safety Center
website.
Four principles of ORM:
n Accept risk when you KNOW the facts, and the benefits outweigh the cost.
n Accept no unnecessary risk.

n Anticipate and manage risk by planning. Risk is best managed in the planning
stage of an operation.

CHAPTER 6 — Operational Planning and Risk Management

6-13

n Make risk decisions at the right level. The greater the risk, the higher the
authority required to approve taking the risk.
NOTE

Operational necessity is only invoked when mission’s success is
more important to the nation than the lives and/or equipment of those
undertaking it. Operational necessity does not apply to training.

6-4.2.1

Levels of ORM.

ORM levels include: in-depth, deliberate, and time critical.
6-4.2.1.1

In-depth ORM. In-depth risk management is used before a project is implemented,

when there is plenty of time to plan and prepare. Examples of in-depth methods
include training and drafting instructions. In-depth ORM is typically conducted by
Fleet commanders and Type commands.
6-4.2.1.2

Deliberate ORM. Deliberate risk management is used at routine periods through the

implementation of a project or process. Examples include quality assurance, onthe-job training, safety briefs, performance reviews, and safety checks. Deliberate
ORM is typically conducted at the Group or squadron level.
The five steps of deliberate ORM are:

1. Identify hazards. A common mistake is to list an effect as a hazard. For example,

listing DCS as a hazard when the real hazard is diving deep in warm water
and working hard. DCS is the effect of a failure to manage the hazard. It is
important to distinguish a hazard from the effects it causes to be able to apply
proper controls. See Appendix 2C, Environmental and Operational Hazards,
for hazards in diving.

2. Assess Hazards. Determine the associated degree of risk in terms of probability

and severity for the hazards identified for the mission. The risk assessment
produces a prioritized list of hazards.

3. Make Risk Decisions. Two actions ultimately lead to making informed risk

decisions:

n Identifying control options. Options include rejecting the risk, avoiding the
risk, delaying an action, transferring the risk and compensating for the risk.
Types of controls are: administrative, engineering, and physical controls.
n Determine Control Effects. With controls identified, the hazard should be
re-assessed, taking into consideration the effect the control will have on
the severity and or probability. This refined risk assessment determines
the residual risk for the hazard, assuming the implementation of selected
controls. At this point, it is also appropriate to consider the cost (personnel,
equipment, money, time, etc.) of the control and the possible interaction
between controls. Do they work together?
4. Implement Controls. Implementing controls relies on communicating to all

involved personnel, establishing accountability, and providing necessary
support.

6-14

U.S. Navy Diving Manual — Volume 2

5. Supervise. Supervision is focused on determining effectiveness of controls.

Supervisors determine the need for further assessment and capture lessons
learned.

6-4.2.1.3

Time Critical Risk Management (TCRM). Time critical risk management requires

a high degree of situational awareness by supervisors. TRCM is the effective use
of all available resources by individuals, crews, and teams to safely and effectively
accomplish the mission or task using risk management concepts when time and
resources are limited.
The U.S. Navy summarizes the time critical risk management process in a fourstep A-B-C-D model (Figure 6-7).
1. Assess the situation.

The three conditions to Assess:
n Task loading - the negative effect on performance of basic tasks due to
additional tasking.
n Human factors - the limitations of the ability of the human body and mind
to adapt to the work environment (e.g. stress, fatigue, impairment, lapses of
attention, confusion, and willful violations of regulations).
n Additive factors - the cumulative effect of variables.
Task loading represents an elevated risk when a new activity is undertaken
by an inexperienced diver. A diver learning how to use a dry suit will need to
dedicate considerably more attention to the proper functioning of the new and
unfamiliar piece of equipment which leads to the elevated risk of neglect of other
responsibilities. Those risks will normally diminish with experience.
Examples:
n Underwater photography or videography
n Diving in environments requiring use of lights or guide reels (such as night
diving, wreck diving and cave diving) or other additional equipment
n Driving a diver propulsion vehicle (DPV)
Common examples of routine functions that can be overlooked as a result of task
loading are:
n Monitoring air supply properly
n Monitoring depth and time
n Monitoring oxygen partial pressure in a rebreather

CHAPTER 6 — Operational Planning and Risk Management

6-15

Task loading is often identified as a key component in diving accidents, although
statistically it is difficult to monitor because divers of differing levels of experience
can cope with a more complex array of tasks and equipment. While simply getting
used to using a drysuit can call for great levels of attention in an inexperienced
diver, it might be a routine piece of equipment for an experienced cold water diver.
2. Balance resources.

Resources are balanced in three different ways:
n Resources and options available.
n Resources verses hazards.
n Individual verses team effort. This means observing individual risk warning
signs. It also means observing how well the team is communicating, knows
the roles that each member is supposed to play, and the stress level and
participation level of each team member.
3. Communicate risks and intentions.

n Communicate hazards and intentions to mitigate.
n Communicate to the right people.
n Use the right communication style; Asking questions is a technique to open
lines of communication, whereas a direct and forceful style of communication
gets a specific result from a specific situation.
4. Do and debrief. (Take action and monitor for change.)

Supervisors shall be specifically wary of “optimism bias” or unrealistic optimism.
Optimism bias causes a person to believe that they are less at risk of experiencing
a mishap compared to others. There are four factors that cause a person to be
optimistically biased:
n Their desired end state
n Their cognitive mechanisms
n The information they have about themselves versus others,
n Overall mood.
Optimism bias is avoided through legitimate mission analysis, planning and ORM.

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U.S. Navy Diving Manual — Volume 2

The Link Between Time Critical and Deliberate
Time Critical Process
and Mnemonic:

5 Step Deliberate Process

A Assess the situation
(your potential for error)

1. Identify Hazards

B Balance your resources
(to prevent and trap
errors)

2. Assess Hazards

C Communicate
(risks and intentions)
D Do and Debrief
(take action and monitor
for change)

3. Make Risk Decisions
4. Implement Controls
5. Supervise
(watch for changes)

Figure 6‑7. The Link Between Time Critical and Deliberate.

6-5

TASK PLANNING AND EMERGENCY ASSISTANCE
6-5.1

Task Planning and Scheduling. Dive plans and schedules should organize

personnel and work objectives so that experienced personnel will always be
available on site.

6-5.1.1

Task Schedule. The following points should be considered when developing

detailed task-by-task schedules for an operation:

n Allow sufficient time for preparation, transit to the site, rendezvous with
other vessels or units, establishing a secure mooring, or setting up and testing
a Dynamic Positioning system.
n The number and profile of repetitive dives in a given time period are limited.
n Plans may include the option to work night and day; however, this may pose
an increased risk.
n The level of personnel support depends on the diving techniques selected.
n Any schedule must be flexible to accommodate unexpected complications,
delays, and changing conditions.
6-5.1.2

Work-up dives. Work up dives shall be conducted if divers have been inactive,
will be working with unfamiliar equipment (dredges, dry suits, MK-16, etc), or

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6-17

diving deep. Work up dives are performed with the goal of acclimating the divers
to the environment and their equipment. Adequate work up dives result in divers
who are focused on the mission and the tasks at hand and not on their gear or the
environment.
Work up dives in a recompression chamber may be conducted to expose divers to
the effects of nitrogen narcosis in a safe environment. However, chamber work up
dives are not an adequate substitute for actual dives in the water with the equipment
that will be used for the mission.
6-5.1.3

Emergency Assistance. It is critical to coordinate emergency assistance before

an operation begins. Three types of assistance may be required in any diving
operation:
n Additional equipment, personnel, supplies, or services.
n Clarification, authorization, or decisions from higher command.
n Emergency assistance in the event of a diving related illness or a physical
illness/injury.
The location of the nearest recompression chamber shall be identified and the
chamber operators notified before the operation begins. The location of the nearest
Diving Medical Officer and medical facility shall be located and notified. Sources
of emergency transportation, military or civilian, shall be established and verified.
If emergency transportation is required by civilian Emergency Medical Services
(EMS) sources, such as air evacuation or ambulance, a Memorandum of Agreement
or Diving Protocol should be established in advance and those casualty response
agreements incorporated into the Command Diving Bill if of a reoccuring nature.
1. Emergency Equipment. The following minimum emergency equipment shall

be available on every dive station and be maintained in the highest state of
readiness:

n Communications equipment capable of reaching help in the event of an
emergency
n A fully stocked first aid kit
n Automated External Defibrillator (AED)
n Portable oxygen supply with sufficient capacity to reach either the
recompression chamber or the planned evacuation location listed in the
Emergency Assistance Checklist (Figure 6-8)
n Bag-valve mask with a means to connect 100% oxygen.
n Means of immobilizing an injured diver (e.g., litter, stretcher, mesh stretcher,
backboard)

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U.S. Navy Diving Manual — Volume 2

n A means of extracting a stricken/unconscious diver from the water.
Supervisors should consider an extraction line (and harnesses for SCUBA
divers) where significant freeboard or pier height would prevent expeditious
recovery of a casualty.
If unable to comply due to operational restrictions (limited space, DDS operations,
saturation diving), this equipment will be as close as practical to the diving
operations and ready for immediate use.
NOTE

WARNING		

A towel and razor is not required but highly recommended when using an
Automated External Defibrillator (AED).
Rescue strops are not appropriate for rescue of unconscious divers.

If space restrictions limit equipment from being available on the dive station, this
equipment shall be as close as practical.
2. Recompression Chamber. The level of risk of a dive mission determines the

need to have a chamber at the dive side or if a nearby chamber will suffice.
The closest available recompression chamber and a backup must always be
identified during dive planning.

Use of a U.S. Navy certified chamber should be planned whenever possible.
U.S. Navy chambers are engineered to provide the maximum degree of safety
and reliability to ensure that the chamber is capable of delivering the full range
of treatments. A non-U.S. Navy chamber may be used as specified in Table 6-1
provided it is inspected, deemed to offer comparable treatment capability, safety,
and accessibility, and authorized by the Commanding Officer or first Flag Officer.
A check sheet for evaluating a non-Navy Level III recompression chamber is
provided on the secure supsalv.org website under 00C3 publications.
A recompression chamber:
n Decreases the severity of DCS and POIS by allowing rapid treatment of post
dive symptoms.
n May mitigate the probability of DCS/POIS when used to conduct surface
decompression.
n Enables resolution of omitted decompression in a safe and controlled
environment.
Table 6-1 defines three Navy recompression support levels. These levels are
arranged according to the recommended proximity of the recompression chamber
to the dive side according to the planned depth and bottom time of the dives. ORM
may indicate the need to have a chamber closer than the recommended levels and
operational requirements may require the chamber to be farther away. However,
operational necessity does not exist in training dives. Dives conducted for training
may carry more risk. Table 6-2 provides further recommendations to support ORM.

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6-19

Definition

RCC Support Level
Level I

A U.S. Navy certified recompression chamber close enough to the dive
site to support surface decompression with a surface interval of 5 minutes.
(Note 1, 2)

Level II

A U.S. Navy certified recompression chamber accessible within one hour of
the casualty. (Note 2)

Level III

A U.S. Navy certified recompression chamber accessible within six hours of
the casualty. (Note 3, 4)

Note 1: The Commanding Officer may authorize an extension of the surface interval to a maximum of 7
minutes (requirements of paragraph 9-12.6 and 12-5.14 apply)
Note 2: A non-Navy chamber may be used if if authorized in accordance with the OPNAVINST 3150.27C.
Note 3: A non-Navy chamber may be used if it is evaluated utilizing the NAVSEA non-Navy recompression
chamber check sheet, and authorized in writing by the Commanding Officer.
Note 4: During extreme circumstances when a chamber cannot be reached within 6 hours the Commanding
Officer (or designated individual) can give authorization to use the nearest recompression facility.
Table 6‑1. Navy Recompression Chamber Support levels.

Depth
(fsw)

Level I Chamber

Level II Chamber

20

Level III Chamber
0 - unlimited

25

372 - 720

0 - 371

30

270 - 720

0 - 269

35

207 - 720

0 - 206

40

>540

191 - 540

0 - 190

45

>360

171 - 360

0 - 170

50

>300

161 - 300

0 - 160

55

>240

141 - 240

0 - 140

60

>220

131 - 220

0 - 130

70

>160

111 - 160

0 - 110

80

>120

91 - 120

0 - 90

90

>90

61 - 90

0 - 60

100

>70

56 - 70

0 - 55

110

>70

51 - 70

0 - 50

120

>55

46 - 55

0 - 45

130

>50

41 - 50

0 - 40

140

>45

31 - 45

0 - 30

150

>40

31 - 40

0 - 30

160

>40

26 - 40

0 - 25

170

>35

26 - 35

0 - 25

180

>35

21 - 35

0 - 20

190

>30

21 - 30

0 - 20

Table 6-2. Air Diving Recompression Chamber Recommendations (Bottom Time in Minutes)

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3. Medical/Critical Care Facility. It is important for planners to determine the

location of the closest medical facility and its capabilities. Not all medical
facilities may be capable of dealing with the most serious emergencies. If
the nearest medical facility is inadequate, the location of the facility with a
necessary capability must also be determined.

In rare instances, the severity of a medical casualty while diving may dictate
bypassing recompression therapy in the designated recompression chamber for
medical care in a critical care facility. Examples include:
n Near-drowning (even with possible POIS or DCS).
n Major/severe trauma (even with possible POIS or DCS).
n Rapid onset of paralysis with inability to breathe.
In the event of one of the situations above, the Dive Supervisor, with consultation
with the DMT or DMO if available, must make an early and definitive decision
about whether to bypass recompression therapy and evacuate a casualty to a
facility capable of providing the needed care. This decision should be based on
the likelihood that an affected diver will die or suffer permanent total disability if
treatment in a critical care facility is delayed due to recompression therapy.
6-6

TRANSITION (EXECUTION)

The transition from planning to execution begins with briefing the entire team
involved in the operation. Two briefs are delivered; the mission brief, and the dive
brief.
6-6.1

Mission Brief. The mission brief provides an overview of the mission, the

Commander’s Intent, and task organization. The briefing ensures that all actions
necessary to accomplish the mission are known and understood. The mission brief
may be conducted well ahead of the commencement of diving and includes:
n Commander’s Critical Information Requirements.
n Decision points.
n Time factors.
n An overview of hazards and controls.

n Premishap plan. The mission brief shall inform the team of actions in the
event of the following:
n Emergency extraction of injured diver.
n Treatment, and transportation of injured/affected divers or team members.
n Lost diver.
n Fouled/Trapped diver.

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n Loss of air.
n Loss of communications.
n Dive station norms and standards.
An emergency assistance checklist shall be completed and posted at the diving
station to provide emergency contact information. Team members shall be notified
of the location of the emergency assistance checklist and how to make notifications
or request assistance (Figure 6-8 is a suggested format).
Mission briefs shall be repeated in as much detail as required at the beginning of
each diving day. All personnel involved in the execution of the mission should be
present, including topside support personnel (eg., boat coxswains, boom operators).
The Diving Planning and ORM Worksheet (Figure 6-9) and the Ship Repair Safety
Checklist for Diving (Figure 6-10) support control of diving operations and may be
useful in conducting the mission brief. These checklists may be tailored to specific
missions and local requirements.
6-6.2

Dive brief. The dive brief ensures that the dive plan is understood by all personnel

in the operation and any questions or doubts are addressed. Any information,
situations, or conditions that have changed since the mission brief must be relayed
to the dive team prior to each dive. Each dive brief shall address the following:

n Dive objective/tasks. Brief the dive objective, considerations, and current
state of conditions (including results or issues from previous dives). Diving
and work procedures for the immediate tasks shall be reviewed during the
briefing. Example: Objective - Recover flight data recorder. Tasks - Cut
away aircraft fuselage, remove black box, place recorder in recovery basket.
n Hazards. Specific hazards of the dive shall be briefed to the divers. Ensure the
divers and the dive team understand the hazards and mitigations necessary
for safe diving.
n Limits and restraints. (ex., Max depth/bottom time, search no farther than..,
do not enter wreckage...)
n Station Assignments. Review and verify assignments to ensure personnel
understand their roles and responsibilities. Ensure a chamber/evacutation
team is assigned. The primary (and possibly secondary) diver and standby
diver assigned to a significantly hazardous dive, or the first dive of the day,
should be experienced divers. No changes to dive station positions should be
made without the permission of the Diving Supervisor and then only after a
thorough turnover.
The Diving Supervisor shall assess the fitness of each diver and inside tender
immediately before a dive (with assistance from medical personnel if available).
Any symptom or condition such as cough, nasal congestion, apparent fatigue,
pregnancy, emotional stress, skin or ear infection is sufficient reason to be removed

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U.S. Navy Diving Manual — Volume 2

from diving rotation and be referred to medical personnel (BUMEDINST 6200.15
(series) provides guidance regarding pregnancy and diving).
The Diving Supervisor shall determine if any divers or inside tenders are taking
any medications that may preclude diving. There are no hard and fast rules for
deciding when a medication would preclude a diver from diving. In general, topical
medications, antibiotics, birth control medication, and decongestants that do not
cause drowsiness would not restrict diving. A DMT or DMO shall be consulted to
determine if the use of specific drugs or the condition requiring their use preclude
diving.
The Diving Supervisor shall verify the diver’s willingness and ability to complete
assigned tasks. No diver shall be forced to make a dive. A diver who regularly
declines diving assignments shall be disqualified as a diver.
n Assistance and Emergencies. Review assistance and actions in case of an
emergency for the first dive of the day according to the mission brief.
Emergencies may be accompanied by confusion. In the event of a diving casualty
or mishap on dive station, calm must be maintained. Maintain silence on the side,
follow the mishap plan, and take orders from the Diving Supervisor.
6-6.3

Responsibilities While Operation is Underway. The Diving Supervisor monitors

progress, debriefs divers, updates instructions to subsequent divers, and ensures
the chain of command is kept apprised of progress of the operation and of any
changes to the original plan. The Diving Supervisor should not hesitate to call
upon the Master Diver for technical advice and expertise during the conduct of the
mission.
Divers shall maintain situational awareness and keep topside personnel informed
of conditions on the bottom, progress of the task, and of any developing problems
that may indicate the need for changes to the plan. The diver shall always obey a
signal from the surface and repeat all commands from the surface.
Additionally, Dive Supervisors maintain situational awareness, exercise good
decision making, and manage the fatigue and stress of the team to conduct
safe diving. The Diving Supervisor must be aware of the cumulative effects of
these factors on his, and the team’s, ability to operate safely and mitigate them
accordingly. NEDU Report TR-05-09 details these skills and they are summarized
in this section.

6-6.3.1

Situational Awareness (SA). Maintaining good SA is critical. Loss of SA is the

greatest of all the causes of mishaps. Situational awareness involves:

n The detection of elements in the environment within a volume of space and
time.
n The comprehension of their meaning.
n The projection of their status in the near future.
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6-23

Failures in acquiring good SA undermine the quality of decisions and performance.
Complacency stems from a lack of SA.
Situational awareness progresses through three levels:
n Basic. An awareness of key elements of the situation (e.g., depth of the
divers, bottom time, stage of the dive, weather, repet group of available
divers).
n Intermediate. A comprehension and integration of the elements in light of
current goals (e.g, understanding that divers are having difficulty completing
their task, and that there are insufficient clean divers available to continue
diving).
n Advanced. The ability to use the current information to predict what will
happen in the future (e.g., the schedule will slip, and upcoming spring tides
will produce greater currents that will increase risk to divers).
6-6.3.1.1.

One misconception about SA is the Dive Supervisor needs to know everything
that is going on. However, overloading the Dive Supervisor can contribute to loss

of SA. For this reason divers shall be thoroughly trained in all aspects of diving to
aid understanding and comprehension of complex factors to avoid giving irrelevant
or untimely information to the dive supervisor, especially in an emergency.
Maintaining good SA:
n Monitor progression of the dive.

n Make extra efforts to get relevant information during decent, ascent, and
abnormal situations.
n After an interruption or distraction, back up several steps, or double check
all steps if possible.
n Be aware of environmental and cumulative effects on the divers and the
team.
n Stand back and look at the problem and double check assumptions with the
rest of the team.
n Stay focused on the goal but avoid tunnel vision.
n Verbalize decisions to the team.
6-6.3.2

Decision Making. The most appropriate decision making strategy for a given

situation is determined by the amount of time available, the level of risk involved,
and the expertise of the decision maker.
To optimize decision making during operations:
n Voice concerns early.

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U.S. Navy Diving Manual — Volume 2

n Avoid unnecessarily rushed decisions.
n Use the most appropriate decision making strategy for the problem based on
time and risk.
n Communicate with the team and be aware of overloading individual team
members.
n Avoid complacency by keeping a questioning attitude.
6-6.3.2.1

A misconception about decision making is that there is always a rule or
procedure that can be followed in nearly every situation. Although there are

procedures for most emergency situations, it is impossible to plan for every
possible situation. This is why divers must conduct detailed planning, be
thoroughly trained and technically competent, and conduct challenging emergency
drills. There are three decision making techniques used in high risk environments:
analytical, rule-based, and recognition-primed.

1. Analytical decision making. Used in the planning stage of a mission when there

is sufficient time available to determine the best solution or strategy through
analysis of courses of action. This method generally produces the best solution
and is especially valuable in solving new problems.

2. Rule-based decision making. Used to solve familiar problems where there are

written rules or procedures. Once a problem is known and the rule that governs
it is identified, a diver simply follows the rule or procedure.

One risk of rule-based decision making is that familiarity can cause complacency
and steps in written procedures can be missed (e.g., missing the step to install
absorbent in a CO2 scrubber canister, or not installing the canister).
3. Recognition-primed decision making (experienced based). This technique is

used by experts to make decisions in high-workload, time limited situations.

This is how leaders make decisions rapidly. One negative aspect of this method
is that a person applying this method may only look for evidence to support their
assumptions (confirmation bias), another is that requisite experience may be
lacking within the decision maker or on the team. This method is characterized by:
n Actions and reactions based on past experience.
n Emphasis on an experienced reading of a situation, rather than gathering
complete information and generating different courses of action.
n Generating a workable solution even though it may not necessarily be the
best.
6-6.3.3

Fatigue. Divers are often required to work long days, carry out tasks outside

normal working hours, or work continuously for a period of days without a break.
In NEDU TR 05-09, Navy divers identified fatigue as the second most common
cause of diving mishaps. Furthermore, when compared to aviation personnel,

CHAPTER 6 — Operational Planning and Risk Management

6-25

Navy divers are less aware of the effects of fatigue on their performance. The
causes of fatigue include long hours of work as well as a lack of sleep. Factors
such as stress, temperature extremes, noise (>80 dB), hyperbaric pressure, and
physical work vibration also induce fatigue. Thus, a combination of cold or hot
water, greater depth, and long work hours combine to create a fatigue-inducing
environment.
The effects of fatigue can be compared to the effects of alcohol consumption. Even
a loss of two hours sleep produces a performance decrement equivalent to two or
three alcoholic beverages. Effects of fatigue may include:
1. Degradation in ability to think:

n Inflexible decision making and loss of innovative thinking.
n Reduced ability to cope with unforeseen rapid changes.
n Inability to adjust plans when new information becomes available.
n Tendency to adopt more ridgid thinking.
2. Reduced coordination in motor skills and timing.
3. Inhibited ability to communicate.
4. Social degradations:

n Irritable or withdrawn.
n Less tolerant of others and more acceptance of own errors.
n Neglect of smaller tasks (inattention to detail).
n Increasingly distracted by discomfort.
5. Increase in risk of decompression sickness.

The Dive Supervisor must maintain an awareness of the effects of fatigue on the
dive team and mitigate the condition to avoid mishaps. All team members should
have a minimum of four to five hours of continuous sleep prior to diving. Divers
performing particularly hazardous dives, or dives that expose them to higher risk
of DCS, should obtain more sleep if possible. Rotating dive station positions,
obtaining short 10-minute intervals of sleep, and performing short bouts of exercise
may improve functioning if obtaining adequate sleep is not possible. The Dive
Supervisor may need to halt diving operations during sustained missions to rest,
recuperate, and restore individual and team functioning.
6-6.3.4

Stress. A certain amount of stress is normal and even beneficial to motivation

and performance. The Dive Supervisor’s concern is when stress adversely affects
performance that may lead to mishaps.

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U.S. Navy Diving Manual — Volume 2

6-6.3.4.1

Chronic and Acute Stress. Stress is important to Navy Divers because both

chronic and acute stresses are potential problems to divers. Chronic stress may
result from any long periods of work such as ship’s husbandry, in which there
are continual deadlines and constant pressure to complete tasks over time. Acute
stress, by contrast, may occur during an emergency in the water or on the dive
side, or during shorter periods of high workload and production pressure.
Indicators of chronic stress include:
n Apathy			

n

Irritability

n Reduced productivity

n

Health complaints

n Absenteeism			

n

Decline in physical appearance

n Alcohol/Drug Abuse		

n

Impaired decision making

n Hostility			

n

Lack of concentration

n Fight or flight response

n

Jumpiness

n Fear, anxiety, or panic

n

Memory impairment

n Surge of energy		

n

Reduced concentration

n Loss of control		

n

Difficulty making a decision

n Anxiety
Indicators of acute stress include:

Once symptoms of stress are present, they can adversely affect the health and
performance of the individual and the team. Acute stress can result in a failure to
manage a situation effectively and can end in equipment damage, injury, or loss of
life. Chronic stress left untreated, may predispose a team member to mistakes, or
affect the rest of the team, and lead to mishaps.
6-6.4

Post Dive/Post Mission. A dive mission is completed when the objective has been
met, the diving team demobilized, and records and reports are filed. Time shall be
allocated to:

n Debrief the dive team
n Analyze the operation, compared the plan to how it was actually carried out
for lessons learned.
n Recover, clean, inspect, maintain, repair, and stow all equipment
n Dispose of materials brought up during the operation
n Prepare records and reports
n Restock expended materials
CHAPTER 6 — Operational Planning and Risk Management

6-27

n Ensure the readiness of the team to respond to the next assignment
6-6.4.1

Post-dive/Post Mission Debrief. Prompt debriefing of divers returning to the

surface provides the Diving Supervisor with information that may influence or alter
the next phase of the operation. Divers should be questioned about the progress of
the work, bottom conditions, anticipated problems, and asked for suggestions for
immediate changes.
After the diving day is complete (or after a shift has finished work, if the operation
is being carried on around the clock), all members of the diving team should be
brought together for a short debriefing of the day’s activities. This offers the team
a chance to provide feedback to the Diving Supervisor and other members of the
team. This group interaction can help clarify any confusion that may have arisen
because of faulty communications, lack of information, or misunderstandings from
the initial briefing.
When the mission is complete, the Diving Supervisor gathers appropriate
data, analyzes the results of the mission, and ensures that required records
are completed. These records may include a Failure Analysis Report
(FAR) if any equipment malfunctions were experienced, mishap or near mishap
report (HAZREP), smooth logs, equipment operating logs, and after action reports.
See Chapter 5 for information or diving records and reports). Capturing lessons
learned and best practices in post dive post mission reports is vital to assist in
planning the next similar operation.

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Figure 6-8. Emergency Assistance Checklist

CHAPTER 6 — Operational Planning and Risk Management

6-29

DIVING PLANNING ORM WORKSHEET
(Sheet 1 of 3)

A. CONDUCT RISK ASSESSMENT: Operational Mission or Training?
Note: There is no such thing as operational necessity in a training environment.
1.

Identify and Assess Hazards
Insert a Severity and Probability code for each applicable hazard and the resulting RAC:

Environmental Hazards:
1. Weather:			____+____=____		2. Sea State:		____+____=____
3. Surface Visibility:		
____+____=____		
4. Underwater Visibility:
____+____=____
5. Depth:			____+____=____		6. Bottom Type:		____+____=____
7. Tides/Currents:		____+____=____		8. Water Temp:		____+____=____
9. Contaminated Water:
____+____=____		
10. Altitude:		
____+____=____
11. Dangerous Marine Life:
____+____=____		
12. Other:		
____+____=____

1. Fouling/Entrapment:
3. Electric Shock:		
5. SONAR:			
7. Surface Traffic:		
9. Loss of Depth Control:

Operational Hazards:
____+____=____		
2. Enclosed Space Diving:
____+____=____		
4. Explosions:		
____+____=____		
6. Nuclear Radiation:
____+____=____		
8. Equipment Failure:
____+____=____		
10 Other: (i.e. fatigue, experience)

____+____=____
____+____=____
____+____=____
____+____=____
____+____=____

Severity:
Category

Description

I

Loss of the ability to accomplish the mission. Death or permanent total disability. Loss of
Mission-critical system or equipment. Major facility damage. Sever environmental damage.
Loss of a Mission-critical security failure. Unacceptable collateral damage.

II

Significantly degraded mission capability or unit readiness. Permanenet partial disability or
severe injury or illness. Extensive damage to equipment or systems. Significant damage to
property or environment. Security failure. Significant collateral damage.

III

Degraded mission capability or unit readiness. Minor damage to equipment, systems, property,
or the environment. Minor injury or illness.

IV

Little or no adverse impact on the mission capability or unit readiness. Minimal threat to
personnel, safety, or health. Slight equipment or systems damage, but fully functional and
serviceable. Little or no property or environmental damage.

Probability:
Category

Description

A

Likely to occur, immediately or within a short period of time. Expected to occur frequently to an
individual item or person; or continuously over a service life for an inventory of items or group.

B

Probably will occur in time. Expected to occur several times to an individual item or person; or
frequently over a service life for an inventory of items or group.

C

May occur in time. Can reasonably be expected to occur some time to an individual item or
person; or several times over a service life for an inventory of items or group.

D

Unlikely to occur, but not impossible.

Figure 6-9. Diving Planning ORM Worksheet (sheet 1 of 3).

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DIVING PLANNING ORM WORKSHEET
(Sheet 2 of 3)

2.

Identify Control Options
Environmental Hazards:
1. Weather:			______________		2. Sea State:		______________
3. Surface Visibility:		
______________		
4. Underwater Visibility:
______________
5. Depth:			______________		6. Bottom Type:		______________
7. Tides/Currents:		______________		8. Water Temp:		______________
9. Contaminated Water:
______________		
10. Altitude:		
______________
7. Dangerous Marine Life:
______________		
8. Other:			
______________

1. Fouling/Entrapment:
3. Electric Shock:		
5. SONAR:			
7. Surface Traffic:		

Operational Hazards:
______________		
2. Enclosed Space Diving:
______________		
4. Explosions:		
______________		
6. Nuclear Radiation:
______________		
8. Equipment Failure:

______________
______________
______________
______________

9. Loss of Depth Control:

______________		

______________

10: Other:		

Probability

Effect of Hazard

SEVERITY

Risk Assessment Matrix

Frequency of Occurrence Over Time

A
Likely

B
Probable

C
May

D
Unlikely

I

Loss of Mission Capability, Unit Readiness
or Asset; Death

1

1

2

3

II

Significantly Degraded Mission Capability or
Unit Readiness; Severe Injury or Damage

1

2

3

4

III

Degraded Mission Capability or Unit
Readiness; Minor Injury or Damage

2

3

4

5

IV

Little or No Impact to Mission Capability or
Unit Readiness; Minimal Injury or Damage

3

4

5

5

Risk Assessment Codes
1 - Critical   2 - Serious   3 - Moderate   4 - Minor   5 - Negligible

Note: It is important to remember that severity is independent of probability and reducing probability
does not change mishap severity.

Figure 6-9. Diving Planning ORM Worksheet (sheet 2 of 3).

CHAPTER 6 — Operational Planning and Risk Management

6-31

DIVING PLANNING ORM WORKSHEET
(Sheet 3 of 3)

3.

Determine Control Effects:
Insert a mitigated probability code for each applicable hazard and the revised RAC.
Note: It is important to remember that hazard severity is independent of mishap probability.
Mitigations only reduce probability and do not change the severity should a mishap occur.

Environmental:
1. Weather:			____+____=____		2. Sea State:		____+____=____
3. Surface Visibility:		
____+____=____		
4. Underwater Visibility:
____+____=____
5. Depth:			____+____=____		6. Bottom Type:		____+____=____
7. Tides/Currents:		____+____=____		8. Water Temp:		____+____=____
9. Contaminated Water:
____+____=____		
10. Altitude:		
____+____=____
7. Dangerous Marine Life:
____+____=____		
8. Other:			
____+____=____

1. Fouling/Entrapment:
3. Electric Shock:		
5. SONAR:			
7. Surface Traffic:		
9. Loss of Depth Control:

Operational:
____+____=____		
2. Enclosed Space Diving:
____+____=____		
4. Explosions:		
____+____=____		
6. Nuclear Radiation:
____+____=____		
8. Equipment Failure:
____+____=____		
10: Other:		

____+____=____
____+____=____
____+____=____
____+____=____
____+____=____

Residual Risk by COA.: List hazards with moderate and above residual risk for each COA:
COA 1: _____________________ _____________________ _____________________
COA 2: _____________________ _____________________ _____________________
COA 3: _____________________ _____________________ _____________________
Risk of each COA: Critical (1), Serious(2), Moderate(3), Minor(4), or Negligible(5):
COA 1:
_____________
COA 2:
_____________
COA 3:
_____________
COA Decision:

Diving Supervisor (Print)_____________________________ Sign:____________________________
Higher Approval (as Required):__________________________/______________________________
Higher Approval (as Required):__________________________/______________________________
Higher Approval (as Required):__________________________/______________________________

Figure 6-9. Diving Planning ORM Worksheet (sheet 3 of 3).

6-32

U.S. Navy Diving Manual — Volume 2

SHIP REPAIR SAFETY CHECKLIST FOR DIVING
(Sheet 1 of 2)

When diving operations will involve underwater ship repairs, the following procedures and safety mea­sures
are required in addition to the Diving Safety Checklist.
SAFETY OVERVIEW
A.

The Diving Supervisor shall advise key personnel of the ship undergoing repair:
1. OOD
4. OODs of ships alongside
2. Engineering Officer
5. Squadron Operations (when required)
3. CDO
6. Combat Systems Officer (when required)

B.

The Diving Supervisor shall request that OOD/Duty Officer of ship being repaired ensure that
appropriate equipment is secured and tagged out.

C.

The Diving Supervisor shall request that OOD/Duty Officer advise him when action has been
completed and when diving operations may commence.

D.

When ready, the diving Supervisor shall request that the ship display appropriate diving signals
and pass a diving activity advisory over the 1MC every 30 minutes. For example, “There are
divers working over the side. Do not operate any equipment, rotate screws, cycle rudder, planes
or torpedo shutters, take suction from or discharge to sea, blow or vent any tanks, activate sonar
or underwater electrical equipment, open or close any valves, or cycle trash disposal unit before
checking with the Diving Supervisor.”

E.

The Diving Supervisor shall advise the OOD/Duty Officer when diving operations commence and
when they are concluded. At conclusion, the ship will be requested to pass the word on the 1MC,
“Diving operations are complete. Carry out normal work routine.”

F.

Diving within 50 feet of an active sea suction (located on the same side of the keel) that is
maintaining a suc­tion of 50 gpm or more, is not authorized unless considered as an emergency
repair and is authorized by the Commanding Officers of both the repair activity and tended vessel.
When it is determined that the sea suction is maintaining a suction of less than 50 gpm and is
less than 50 feet, or maintaining a suction of more than 50 gpm and is less than 50 feet but on the
opposite side of the keel, the Diving Supervisor shall determine if the sea suction is a safety hazard
to the divers prior to conducting any diving operation. In all cases the Diving Supervisor shall be
aware of the tend of the diver’s umbilical to ensure that it will not cross over or become entrapped
by an active sea suction. Diving on 688 and 774 class submarines does not present a hazard
to divers when ASW and MSW pumps are operating in slow or super slow modes. Diver tag-out
procedures must be completed in accordance with the TUMS and SORM to ensure ASW and MSW
pumps are not operated in fast mode. Divers must be properly briefed on location of suctions and
current status of equipment.

NOTIFY KEY PERSONNEL.
1.

OOD

___________________________________________ (signature)

2.

Engineering Officer

___________________________________________ (signature)

3.

CDO

USS_______________________________________ (signature)

4.

OOD

USS_______________________________________

OOD

USS_______________________________________

OOD

USS_______________________________________

OOD

USS_______________________________________

5.

Squadron Operations

6. Port Services Officer
		

_______________________________________
_______________________________________
(Diving Supervisor (Signature)

Figure 6-10. Ship Repair Safety Checklist for Diving (sheet 1 of 2).

CHAPTER 6 — Operational Planning and Risk Management

6-33

SHIP REPAIR SAFETY CHECKLIST FOR DIVING
(Sheet 2 of 2)

TAG OUT EQUIPMENT
TAG OUT

SIGNATURE AND RATE

Rudder

____________________________________________

Anchors

____________________________________________

Planes

____________________________________________

Torpedo tube shutters

____________________________________________

Trash disposal unit

____________________________________________

Tank blows

____________________________________________

Tank vents

____________________________________________

Shaft(s) locked

____________________________________________

Sea suctions

____________________________________________

Sea discharges

____________________________________________

U/W electrical equipment

____________________________________________

Sonars

____________________________________________

Other U/W equipment

____________________________________________

		

USS________________________________________

		

		

(name of ship)

CDO________________________________________

		

(signature of CDO)

Figure 6‑10. Ship Repair Safety Checklist for Diving (sheet 2 of 2).

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U.S. Navy Diving Manual — Volume 2

CHAPTER 7

SCUBA Air Diving Operations
7-1

INTRODUCTION
7-1.1

Purpose. The purpose of this chapter is to familiarize divers with standard and

emergency procedures when diving with SCUBA equipment.

7-1.2

Scope. This chapter covers the use of open-circuit SCUBA in operations 380 F and

above. Operations 370 F and colder are discussed in Chapter 11 (Ice Diving).

7-1.3

References:

n NAVSEA 00C Authorized for Navy Use (ANU) List
n U.S. Government Occupational Safety and Health Administration (OSHA)
Diving Standards. 29 CFR Part 1910 Subpart T.
n Department of Transportation (DOT) specifications (DOT 3AA, DOT 3AL,
DOT SP6498, and DOT E6498)
n Compressed Gas Association (CGA) pamphlets C-1 and C-6
n Compressed Gas Handling. Naval Ships Technical Manual, Chapter 550.
NAVSEA 0901-LP-230-0002.
n Procedures for the Requisitioning, Handling, Storage, and Disposal of Items
Which Contain Radioactive By-Product Material. NAVSUPINST 5101.6
(series)
n U.S. Navy Underwater Ship Husbandry Manual. (NAVSEA S0600- AAPRO-010)
7-2

OPERATIONAL CONSIDERATIONS

7-2.1

Operational Limits. Figure 7-1 lists operational limits for SCUBA. These limits

are based on a practical consideration of working time versus decompression
time and oxygen-tolerance limits and may not be exceeded except by specific
authorization in accordance with OPNAVINST 3150.27 (series).

Exceptional exposure dives have a significantly higher probability of DCS and
CNS oxygen toxicity. Planned exceptional exposure dives shall not be conducted
except by specific authorization in accordance with OPNAVINST 3150.27 (series).
Increased air consumption at deeper depths, hazards of nitrogen narcosis, and the
exposure to the environment are significant limiting factors in SCUBA. Diving

CHAPTER 7 — SCUBA Air Diving Operations

7-1

supervisors shall consider employing an independent back-up air source for all
SCUBA dives.

NORMAL AND MAXIMUM LIMITS FOR OPEN CIRCUIT SCUBA DIVING
Depth fsw
(meters)

Operational Limit

60 (18)

Maximum depth for standby SCUBA diver using a fully charged single cylinder with less
than 100 SCF air available.

130 (40)

Normal working limit. Dives deeper than 130fsw may be made with approval of the
Commanding Officer or Officer-in-Charge.

190 (58)

Maximum working limit.

Notes:
1.

Do not exceed No‑Decompression limits during routine dives. Decompression dives may be made with
approval of the Commanding Officer or Officer-in-Charge. See paragraph 7-9.3 for guidance. Closedcircuit underwater breathing apparatus is preferred over SCUBA for dives requiring decompression
where a free swimming dive method is required.

2.

Officers-in-Charge exercising command authority to include exceptions to above limits must be
designated in writing.

3.

29 CFR Part 1910 and OSHA Directive CPL 02-00-151 provides additional OSHA restrictions for
civilian DOD SCUBA diving. DOD civilian divers are identified as all permanent DOD employees who
have been formally trained at an approved U.S. Navy diving school. Commercial divers contracted by
DOD who are not permanent government employees are subject to these provisions. The following are
some examples of OSHA restrictions for DOD divers:
• The maximum depth for SCUBA diving is 130 fsw. A decompression chamber is required (i.e.,
available within 5 minutes from the dive location) when diving deeper than 100 fsw, or when diving
outside of the no-decompression limits.
• A manual reserve (J valve), or an independent reserve cylinder gas supply with a separate
regulator is required.
• Submersible pressure gauge must be worn by each diver.
• DOD Civilian divers shall remain at the location of the recompression chamber for 1 hour after
surfacing for all dives that require a recompression chamber to be available within 5 minutes of
the dive location.

4.

DOD civilian divers are exempt from regulation by OSHA when conducting uniquely military operations.
Commanding Officer shall issue a letter designating military centric diving operations.

Figure 7‑1. Normal and Maximum Limits for SCUBA Diving.

7-2

U.S. Navy Diving Manual — Volume 2

SCUBA General Characteristics

Restrictions:
Work limits:
1.
2.
3.
4.

Principle of Operation:
Self contained, open-circuit demand system

5.
6.

Minimum Equipment:
1.
2.
3.
4.
5.
6.
7.
8.

Open-circuit SCUBA with submersible
pressure gauge
Life preserver/buoyancy compensator
Weight (if required)
Dive knife
Face mask
Swim fins
Submersible wrist watch
Depth gauge

Principal Applications:
1.
2.
3.

Shallow water search
Inspection
Light repair and recovery

Normal 130 fsw
Maximum 190 fsw with approval of the
Commanding Officer or Officer-in-Charge.
Deeper than 130 fsw for operationally
necessary dives.
Standby diver with a minimum of 100
SCF of air available for dives deeper than
60 fsw
Within no-decompression limits
Current - 1 knot maximum. Current greater
than 1 knot, requires ORM analysis. At a
minimum the divers(s) must be tended or
have a witness float.

Operational Considerations:
1.
2.

3.
4.

Standby diver required.
Small craft is mandatory for diver recovery
during open-ocean diving, when diving
off of a large platform or when the diver
is untended and may be displaced from
dive site, e.g., during a bottom search in a
strong current or a long duration swim.
Moderate to good visibility preferred.
Dive supervisors shall consider employing
an independent back-up air source for all
SCUBA dives.

Advantages:
1.
2.
3.
4.
5.

Rapid deployment
Portability
Minimum support requirements
Excellent horizontal and vertical mobility
Minimum bottom disturbances

Disadvantages:
1.
2.
3.
4.

Limited endurance (depth and duration)
Limited physical protection
Influenced by current
Lack of voice communication (unless
equipped with a through-water
communications system or full face mask)

Figure 7‑2. SCUBA General Characteristics.

CHAPTER 7 — SCUBA Air Diving Operations

7-3

Manning. The minimum number of qualified divers required on station is provided

7-2.2

in Figure 7-3.

The minimum SCUBA dive team includes the Diving Supervisor, divers, and
standby diver. Additional members support in roles such as tender, boat crew,
special systems, and equipment operators as required by the nature of the operation.
Personnel levels may need to be increased as necessary to meet the operational
situation.
MINIMUM MANNING LEVELS FOR OPEN CIRCUIT SCUBA DIVING
Single Diver

Buddy Pair

1

1

Logs

(a)

(a)

Diver

1

2

1(b)

(b)

1

1

(c)

(c)

4(d)

4

Diving Supervisor

Diver Tender
Standby Diver
Standby Diver Tender
Total

WARNING
These are the minimum personnel levels allowed.
The Dive Supervisor shall conduct effective mission analysis, mission planning, and
ORM to ensure personnel levels are adequate for safe diving.
NOTES:
(a) The Diving Supervisor may keep logs.
(b) May be a non-diver tender. The Dive Supervisor shall ensure non-diver tenders are thoroughly instructed in the required
duties.
(c) The Diving Supervisor shall tend the standby diver if the standby diver is deployed.
(d) The Diving Supervisor may utilize three qualified divers and one non-diver tender based on operational necessity.

Figure 7-3. Minimum Manning Levels for SCUBA Diving.

7-2.2.1

SCUBA Diving Supervisor. Dive Supervisors are selected based on leadership,

maturity, supervisory ability, and technical expertise and may be any formally
trained U.S. military diver, PQS qualified, and designated in writing by the
Commanding Officer.

The Diving Supervisor is in charge of the diving operation regardless of rank. The
Dive Supervisor shall execute dives in a safe and effective manner and discontinue
diving operations in the event of unsafe diving conditions. The Dive Supervisor
is responsible for knowing and complying with rules, limits, procedures, and
7-4

U.S. Navy Diving Manual — Volume 2

for understanding the extent of their authority as delegated by the Commanding
Officer. The Dive Supervisor shall be included in operational planning and shall
conduct and document an adequate ORM assessment for each diving day. Diving
operations shall not be conducted without the presence of the Diving Supervisor.
7-2.2.2

SCUBA Diver. The diver is responsible for:

n Reporting any conditions that may interfere with safe diving.
n Preparation, maintenance, and safe operation of diving equipment.
n Maintaining a high level of health and fitness.
n Maintaining proficiency on systems, equipment, and procedures.
n Obeying a signal from the surface.
n Keeping track of depth and time of the dive.
n Keeping situational awareness (changing bottom conditions, keeping the
tending line/buddy line from becoming snagged or entangled).
n Keeping within depth/time limits as prescribed by the Dive Supervisor.
n Knowing the meaning of all hand and line-pull signals.
n Knowing the symptoms of diving ailments.
n Knowing the emergency procedures for SCUBA diving.
n Monitoring the actions and apparent condition of the dive partner. If at any
time the dive partner appears to be in distress or is acting in an abnormal
manner, determine the cause immediately and take appropriate action.
7-2.2.3

Buddy Diver. The single greatest safety practice in Navy SCUBA operations is the
use of the buddy system. Dive partners operating in pairs are jointly responsible
for the assigned task and each other’s safety. Each diver keeps track of depth and
time during the dive. The basic rules for buddy diving are:

n Always maintain contact with the dive partner.
n Never leave a partner unless the partner has become trapped or entangled
and cannot be freed without additional assistance.
n If partner contact is broken, follow the established lost-diver plan.
n If one member of a dive team aborts a dive, for whatever reason, both divers
must surface.
n Know the proper method of buddy breathing.

CHAPTER 7 — SCUBA Air Diving Operations

7-5

7-2.2.4

Standby SCUBA Diver. Standby diver is a fully qualified and experienced diver

assigned to provide emergency assistance. A standby diver and tender is required
for all SCUBA dives.
Standby SCUBA diver shall:
n Be fully prepared to respond if called upon for assistance.
n Be equipped with an octopus rig.
n Receive the same briefings and instructions as the working divers.
n Avoid distractions and remain fully aware of the progress of the dive.
n Stay informed of any changes in conditions or the dive plan.
n Be outfitted with the equivalent or greater diving dress (wetsuit, drysuit) as
the primary divers.
Standby diver shall don all equipment and tending line, and be checked by the
Diving Supervisor. Standby diver may then remove mask and fins and have them
ready to don immediately. The standby diver may remove the tank at the discretion
of the Diving Supervisor if the hazards of remaining dressed outweigh the need to
have standby immediately ready to deploy. The standby diver need not be equipped
with the same equipment as the primary diver, but shall have equivalent depth and
operational capabilities.

7-2.2.5

Tenders. The Dive Supervisor may elect to use a non-diver tender. The Dive

Supervisor shall ensure any non-diver tenders are thoroughly instructed in the
required duties. The tenders are responsible for:

n Assisting the diver in donning/doffing dive gear, and in getting in and out of
the water.
n Tracking the location of the diver by observing the bubble trail, dive float,
or locating device (such as a pinger or strobe light). When tending with
a surface float, the tender shall continually monitor the float line for pull
signals.
n Exchanging line-pull signals with the diver in accordance with the procedures
given in Table 8-2.
n Keeping full situational awareness of the dive side and any hazards in
the vicinity or changing topside conditions. Tenders shall notify the Dive
Supervisor of any conditions, which may adversely affect diving operations.
n Knowing CPR, first aid procedures, and providing emergency assistance as
directed by the diving Supervisor.
When tending the diver on a line from the surface:

7-6

U.S. Navy Diving Manual — Volume 2

n Remain alert for any signs of an emergency (increase/decrease in bubbles on
the surface).
n Keep lines free of slack.
n Signal the diver with a single pull every 2 or 3 minutes to determine if the
diver is all right. If the diver fails to respond to line-pull signals, the standby
diver must investigate immediately.
7-2.2.6

7-3

Other Personnel. Other personnel may include small boat operators, winch
operators, crane operators, or special equipment operators. All personnel involved
in the diving operation shall be under the control of the Diving Supervisor.

MINIMUM EQUIPMENT FOR SCUBA OPERATIONS

Diving equipment used in a Navy dive shall be certified or ANU listed. At a
minimum, each diver must be equipped with the following items (Figure 7-2):
n Open-circuit SCUBA.
n Face mask.
n Life preserver/buoyancy compensator.*
n Weights as required.
n Knife.**
n Swim fins.
n Submersible pressure gauge. **
n Submersible wrist watch. One per pair with a buddy line.**
n Depth gauge. **
n Octopus. ***
*

During the problem-solving pool phase of SCUBA training, CO2 cartridges
may be removed and replaced with plugs or expended cartridges that are clearly
marked and identified with international orange.

**

These items are not required for the pool phase of SCUBA training.

*** At Commanding Officer’s discretion based on ORM.
7-3.1

Open-Circuit SCUBA. All open-circuit SCUBA employ a demand system

that supplies air each time the diver inhales. The basic open-circuit SCUBA
components are:
n Demand regulator assembly

CHAPTER 7 — SCUBA Air Diving Operations

7-7

n One or more air cylinders
n Cylinder valve and manifold assembly
n Backpack or harness
7‑3.1.1

Demand Regulator Assembly. The demand regulator assembly delivers breathing

7‑3.1.1.1

First Stage. The first stage regulator reduces high-pressure air from the cylinder to

gas at a usable pressure to the diver and is the central component of the opencircuit system. There are two stages in a typical system (Figure 7-4). The first
stage regulator is mounted to the cylinder valve assembly and the second-stage
regulator is held in the divers mouth by a soft mouthpiece. The two stages are
connected by a length of low-pressure hose (also called the intermediate hose)
which passes over the diver’s right shoulder.

an intermediate pressure (also called overbottom pressure) that is a predetermined
level over ambient pressure. Refer to the regulator technical manual for the specific
over bottom pressure setting.
The first stage contains a valve, spring, and diaphragm that allows air from the high
pressure cylinder to enter the intermediate chamber based on the spring pressure
and ambient pressure. On the surface, the intermediate pressure will be equal to the
spring pressure on the diaphragm. As ambient pressure is increased (as when the
diver descends) it pushes against the diaphragm which pushes a pin that opens the
valve which allows just enough additional high pressure air to enter the intermediate
chamber to achieve a balance in pressure.
When the diver inhales and causes the intermediate pressure to fall, the external
water pressure pushes the diaphragm inward, opens the valve, and restores pressure
to the intermediate chamber.

7‑3.1.1.2

Second Stage. The second stage regulator reduces the intermediate pressure

from the first stage regulator. The second stage houses a movable diaphragm
that is linked by a lever to a low-pressure valve, which leads to a low-pressure
chamber. Similar to the first stage regulator, when the air pressure in the lowpressure chamber equals the ambient water pressure, the diaphragm is in the
neutral position and the low-pressure valve is closed. When the diver inhales, the
pressure in the low-pressure chamber is reduced, causing the diaphragm to be
pushed inward by the higher ambient water pressure. The diaphragm actuates the
low-pressure valve, which opens and permits air to flow to the diver. The greater
the demand, the wider the low-pressure valve is opened, thus allowing more air
flow to the diver. When the diver stops inhaling, the pressure on either side of
the diaphragm is again balanced and the low-pressure valve closes. As the diver
exhales, the exhausted air passes through at least one check valve and vents to the
surrounding water.
The second stage has a purge button, which allows manual operation of the lowpressure valve which can be used to force out any water which may have entered
the regulator. The principal disadvantages of the single-hose unit are an increased

7-8

U.S. Navy Diving Manual — Volume 2

First Stage. High pressure air flows through the orifice of the first stage into the intermediate chamber. When the pressure
in the intermediate chamber reaches ambient plus diaphragm balance spring set pressure, the first stage assembly closes.

Second Stage. Upon inhalation the second stage diaphragm moves inward and the horseshoe lever opens the second stage
valve assembly. Intermediate pressure air from the hoses is throttled across the orifice and fills the low pressure chamber to
ambient pressure and flow is provided to the diver. Upon exhalation the diaphragm is pushed outward and the second stage
is closed. Expired air is dumped from the low pressure chamber to the surrounding water through the exhaust valve.

Figure 7-4. Schematic of Demand Regulator.

CHAPTER 7 — SCUBA Air Diving Operations

7-9

tendency to freeze up in cold water and the exhaust of air in front of the diver’s
mask.
The Navy PMS system and the manufacturer’s service manual provides guidance
for repairing and maintaining SCUBA regulators.
7‑3.1.1.4

Full Face Mask. An ANU approved full

7‑3.1.1.5

Mouthpiece. The size and design of

7‑3.1.1.6

Octopus. An octopus is an additional

face mask may be used with an approved
single-hose first-stage regulator with
an octopus, to the maximum approved
depth of the regulator, as indicated in the
NAVSEA/00C ANU list (Figure 7-5).

SCUBA mouthpieces differ between
manufacturers, but each mouthpiece
provides
relatively
watertight
passageways for delivering breathing air
into the diver’s mouth. The mouthpiece
should fit comfortably with slight
pressure from the lips.

single hose second stage regulator
connected to the diver’s first stage
regulator and may be used in case the
diver’s primary second stage regulator Figure 7-5. MK 20 FFM SCUBA.
fails or for buddy breathing. Hose length
and designation markings are at the discretion of the diving unit. An octopus
is mandatory for standby diver. Use of an octopus is the preferred method to
accomplish buddy breathing (see paragraph 7-9.1).
The octopus shall be secured on or near the diver’s chest to provide easy access
in an emergency and to allow the diver to immediately observe if the octopus free
flows during the dive. During predive inspection, the diver shall breathe the octopus
to ensure it is working properly.

7‑3.1.1.7

Submersible Cylinder Pressure Gauge. The SCUBA regulator assembly shall be

equipped with a submersible pressure gauge to indicate pressure content of the
cylinder.
The submersible cylinder pressure gauge provides the diver with a continuous
read-out of the air remaining in the cylinder(s). Various submersible pressure
gauges suitable for Navy use are commercially available. Most are equipped with
a 2 to 3 foot length of high-pressure rubber hose with standard fittings, and are
secured directly into the first stage regulator. When turning on the cylinder, the
diver should turn the face of the gauge towards the deck to prevent injury in the
event of a blowout. The gauge and hose should be tucked under a shoulder strap or

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U.S. Navy Diving Manual — Volume 2

otherwise secured to avoid its entanglement with bottom debris or other equipment.
Submersible pressure gauges must be calibrated in accordance with PMS.
When diving without a reserve, the dive shall be terminated when the cylinder
pressure reaches 500 psi for a single cylinder or 250 psi for twin manifold cylinders.
7‑3.1.2

Cylinders. SCUBA cylinders (tanks or bottles) are designed to hold high pressure
compressed air. Because of the extreme stresses imposed on a cylinder at these
pressures, all cylinders used in SCUBA diving must be inspected and tested
periodically. Seamless steel or aluminum cylinders which meet Department of
Transportation (DOT) specifications (DOT 3AA, DOT 3AL, DOT SP6498, and
DOT E6498) are approved for Navy use. Cylinders used in Navy operations have
identification symbols stamped into the shoulder (Figure 7-6).

DOT3AA2250
Z45015
PST
AB
7-90 +
1. DOT material specification, DOT3AA service
working pressure 2,250 PSIG.
2. Serial number assigned by manufacturer,
Z45015.

DOTSP6498/3000
OR DOT3AL/3000
Z45015
AB
7-90
1. DOT material specification, DOTSP6498 or
DOT3AL service working pressure 3,000
PSIG.
2. Serial number assigned by manufacturer,
Z45015.

3. Identification mark of manufacturer or owner,
PST.

3. Inspector’s stamp, AB.

4. Inspector’s stamp, AB.

4. Month and year of initial qualification test, 7-90.

5. Month and year of qualification test, 7-90.
6. Plus sign (+) indicates air allowable 10% over
service pressure.

STEEL CYLINDERS

ALUMINUM CYLINDERS

Figure 7-6. Typical Gas Cylinder Identification Markings.

CHAPTER 7 — SCUBA Air Diving Operations

7-11

7‑3.1.2.1

7‑3.1.2.2

Size, Volume, and Capacity. Approved SCUBA cylinders are available in several

sizes. One or two cylinders may be worn to provide the required quantity of air for
the dive. The volume of a cylinder, expressed in actual cubic feet or cubic inches,
is a measurement of the internal volume of the cylinder. The capacity of a cylinder,
expressed in standard cubic feet or liters, is the amount of gas (measured at surface
conditions) that the cylinder holds when charged to its rated pressure. Table 7-1
lists the sizes of some standard SCUBA cylinders.
Inspection Requirements. Open-circuit SCUBA cylinders shall:

n Be visually inspected at least once every 12 months and every time water or
particulate matter is suspected in the cylinder. Cylinders containing visible
accumulation of corrosion must be cleaned before being placed into service.
n Be hydrostatically tested at least every five years in accordance with DOT
regulations and Compressed Gas Association (CGA) pamphlets C-1 and
C-6.
Table 7‑1. Sample SCUBA Cylinder Data.
Open-Circuit Cylinder
Description (Note 1)

Rated Working Pressure
(PSIG)

Floodable Volume
(Cu.Ft.)

Steel 72

2,250

0.420

Steel 100

3,500

0.445

Steel 120

3,500

0.526

Aluminum 50

3,000

0.281

Aluminum 63

3,000

0.319

Aluminum 80

3,000

0.399

Aluminum 100

3,300

0.470

Note 1: Fifty cubic feet is the minimum size SCUBA cylinder authorized as a primary air
source.

7‑3.1.2.3

Guidelines for Handling Cylinders. Because SCUBA cylinders are subject to

7‑3.1.2.4

Cylinder Valves and Manifold Assemblies. Cylinder valves and manifolds make
up the system that passes the high-pressure air from the cylinders to the first-stage
regulator.

continuous handling and the hazards posed by a damaged cylinder are significant,
close adherence to the rules in Section 7-5 and NAVSEA 0901-LP-230-0002,
NSTM Chapter 550, “Compressed Gas Handling.” is mandatory.

The cylinder valve and manifold assembly includes the following:
n Cylinder Valves. The cylinder valve threads into the tank with a straight
male connection that is sealed with an O-ring and serves as an on/off valve.
Cylinder valves that employ a built in air reserve mechanism (J valve) are
preferred over valves without a reserve mechanism (K-valves) when diving
in zero visibility where a gauge may not be able to be read because the
J-valve will provide a warning that air is low.

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U.S. Navy Diving Manual — Volume 2

n Manifold Connectors. If two or more cylinders are used together, a connecting
manifold provides the necessary interconnection. Most manifolds use straight
threads and incorporate an O-ring as a seal, but some earlier models may
have a tapered (pipe) thread design. Straight and tapered thread manifold
fittings are not interchangeable.
n Reserve Mechanism. The cylinder valve reserve mechanism retains air in the
cylinder with a spring loaded check valve that is designed to hold back 500
psi. When the reserve lever on the cylinder valve is turned down, the spring
mechanism is compressed and the check valve is lifted (opened) to make
the remaining air available to the diver. Reserve mechanisms on double tank
manifolds retain air in only one of the cylinders so that when the 500 psi is
released from the reserve it is distributed between the two cylinders. The
reserve lever must be turned down (check valve open) to charge the cylinder
because when the reserve lever is in the up position (check valve closed), the
check valve will not let any air into the cylinder.
n Over Pressure Safety Device. The cylinder valve or manifold contains a
high-pressure blowout plug that retains a safety burst disc. Safety burst discs
must be rated at ten percent over the maximum cylinder pressure or at the
manufacturer’s recommended pressure. The burst disc vents pressure in the
event of excessive pressure buildup. Once ruptured by excessive pressure,
the over-pressure safety device does not automatically reset and the entire
content of the cylinder is vented. For this reason, it is advisable to adhere to
safe charging rates, keep cylinders out of direct sun, and keep spare safety
burst discs on hand.
7‑3.1.2.5

7‑3.2

Backpack or Harness. The backpack or harness holds the SCUBA on the diver’s
back. The backpack may include a lightweight frame with the cylinder(s) held in
place with clamps or straps. The usual system for securing the cylinder to the diver
uses shoulder and waist straps. All straps must have a quick-release feature, easily
operated by either hand, so that the diver can remove the cylinder and leave it
behind in an emergency.
Face Mask. The face mask protects the diver’s eyes and nose from the water.
Additionally, it provides maximum visibility by putting a layer of air between the
diver’s eyes and the water.

Face masks are available in a variety of shapes and sizes for diver comfort. To
check for proper fit, hold the mask in place with one hand and inhale gently through
the nose. The suction produced should hold the mask in place. Don the mask with
the head strap properly adjusted and inhale gently through the nose. If the mask
seals, it should provide a good seal in the water.
Some masks are equipped with a one-way purge valve to aid in clearing the mask
of water. Some masks have indentations at the nose or a neoprene nose pad to
allow the diver to block the nostrils to equalize the pressure in the ears and sinuses.
Several models are available for divers who wear eyeglasses. One type provides a
prescription-ground faceplate, while another type has special holders for separate
CHAPTER 7 — SCUBA Air Diving Operations

7-13

lenses. All faceplates must be constructed of tempered or shatterproof safety glass
because faceplates made of ordinary glass can be hazardous. Plastic faceplates are
generally unsuitable as they fog too easily and are easily scratched.
The size or shape of the faceplate is a matter of personal choice, but the diver
should use a mask that provides a wide, clear range of vision.
7‑3.3

Life Preserver. The principal functions of the life preserver are to assist a diver in

rising to the surface in an emergency and to keep the diver on the surface in a faceup position (Figure 7-7).
All ANU life preservers shall:
n Have a low pressure inflation device (CO2).
n Have a manual inflation device.

n Have an overpressure valve (OPV) to prevent rupture of the life preserver on
ascent. (with the exception of the UDT (9C-4220-00-276-8929)).
n Have sufficient volume to raise an unconscious diver safely from the
maximum dive depth to the surface.
n Be sturdy enough to resist normal wear and tear.
Most life preservers employ carbon dioxide (CO2) cartridges as the low pressure
inflation device. The cartridges must be the proper size for the life preserver and
must be weighed prior to use, in accordance with PMS.
7‑3.4

Buoyancy Compensator (BC). A buoyancy compensator may be used at the Diving

Supervisor’s discretion. The decision to use a life preserver or a BC balances diver
safety in the event of an emergency with diver comfort while working in the water
column. BCs will maintain a diver in a head up position on the surface but most are
NOT designed to maintain the diver in a face up position without counter weights.
A number of factors must be considered when selecting a BC: type of wet suit,
diving depth, breathing equipment characteristics, nature of diving activity,
accessory equipment, and weight belt.
Buoyancy compensators shall:
n Provide a minimum of 10 pounds of positive buoyancy at the maximum
depth.
n Have jettisonable weights if integrated into the vest.
n Have a power inflator.
n Have an alternate source of inflation (oral).
n Have an over-pressure relief valve.
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Training and practice under controlled conditions are required to master diving
with a BC. Rapid, excessive inflation can cause an uncontrolled ascent. The diver
must vent air from the compensator during ascent to maintain proper control.
Refer to the appropriate technical manual for complete operations and maintenance
instructions for the equipment. A BC is not required when using a variable volume
dry suit (VVDS).
ANU listed life preservers and buoyancy
compensators must be operated in the
authorized configuration. Additionally,
life
preservers
and
buoyancy
compensators may have specific depth
limits that must be verified with the
ANU.
CAUTION		

7‑3.5

Prior to use of VVDS as a buoyancy
compensator, divers must be
thoroughly familiar with its use.
Weight Belt. SCUBA is designed to

have near neutral buoyancy. With full
tanks, a unit tends to have negative
Figure 7-7. Life Preserver.
buoyancy, becoming slightly positive
as the air supply is consumed. Most
divers are positively buoyant, even more so when wearing a wet suit, and need to
add extra weight to achieve a neutral or slightly negative status. This extra weight
is furnished by a weighted belt worn outside of all other equipment, and strapped
so that it can easily released in the event of an emergency.
Wearing the proper amount of weight is vital to diver safety. An over weighted
diver will be forced to compensate for the extra weight by adding air to the life
preserver or buoyancy compensator and could result in an uncontrolled ascent if
weight is lost. If a life preserver is used to compensate for buoyancy in the water
column due to being over weighted, it will cause the diver discomfort, as the life
preserver will attempt to rotate to the diver to the face up position and distract the
diver from dive tasks. An underweighted diver will have difficulty descending,
particularly in the first 30fsw, until the wetsuit compresses (if worn). As the dive
progresses the air is depleted and the diver will become lighter. After leaving bottom
the diver may experience an uncontrolled ascent, particularly in the last 30fsw, as
the wetsuit expands and adds more buoyancy. Divers should perform a buoyancy
check before leaving surface and add or remove weight as necessary to maintain
neutral or slightly negative buoyancy (with no air in the life preserver/BC).
Each diver may select the style and size of belt and weights that best suit the diver.
A weight belt shall meet certain basic standards:
n The buckle must have a quick-release feature, easily operated by either hand.

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7-15

n The weights (normally made of lead) should have smooth edges so as not to
chafe the diver’s skin or damage any protective clothing.
n The belt should be made of rot- and mildew-resistant fabric, such as nylon
webbing.
7‑3.6

Knife. Several types of knives are available. For EOD and other special missions,

a nonmagnetic knife designed for use when diving near magnetic-influence mines
is used.
Knives may have single- or double-edged blades with chisel or pointed tips. The
most useful knife has one sharp edge and one saw-toothed edge. All knives must
be kept sharp.
The knife must be carried in a suitable scabbard and worn on the diver’s hip,
thigh, or calf. The knife must be readily accessible, must not interfere with
body movement, and must be positioned so that it will not become fouled while
swimming or working. The scabbard should hold the knife with a positive but
easily released lock.
The knife and scabbard must be secured to the diver’s body and not to a piece of
equipment that may be ditched in an emergency.

7‑3.7

Swim Fins. Swim fins increase the efficiency of the diver, permitting faster

swimming over longer ranges with less expenditure of energy. Swim fins are made
of a variety of materials and styles.

Each feature - flexibility, blade size, and configuration - contributes to the relative
power of the fin. A large blade will transmit more power from the legs to the water,
provided the legs are strong enough to use a larger blade. Fins designed for surface
swimming or free diving, fins with small or soft blades, or “split fin” style fins
should not be worn while SCUBA diving since these fins were not designed to
transmit adequate power to propel a diver encumbered with SCUBA. Ultimately,
fin selection is a matter of personal preference based on the diver’s strength and
experience, and the nature of the particular operation.
7‑3.8

7-3.9

Wrist Watch. Analog diver’s watches must be waterproof, pressure proof, and
equipped with a rotating bezel outside the dial that can be set to indicate the elapsed
time of a dive. A luminous dial with large numerals is also necessary. Additional
features such as automatic winding, nonmagnetic components, and stop watch
action are available. Digital watches, with a stop watch feature to indicate the
elapsed time of a dive, are also available, and most are equipped with a maximum
depth indicator.
Depth Gauge. The depth gauge measures the pressure created by the water column

above the diver and is calibrated to provide a direct reading of depth in feet of
sea water. It must be designed to be read under conditions of limited visibility.
The gauge mechanism is delicate and should be handled with care. Accurate depth

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determination is important to a diver’s safety and must be checked in accordance
with PMS, or whenever a malfunction is suspected.
7-4

OPTIONAL EQUIPMENT FOR SCUBA OPERATIONS

The requirements of a specific diving operation determine which items of optional
diving equipment may be necessary. This section lists some of the equipment that
may be used.

7-4.1

n Protective clothing n

Variable volume dry suit

n Wet suit		

n

Acoustic beacons

n Signal flare		

n

Lines and floats

n Gloves		 n

Snorkel

n Hoods		 n

Wrist compass

n Tool bag		

n

Boots or hard-soled shoes

n Whistle		

n

Chem light and strobe light

n Slate and pencil

n

Dive computer

n Tools and light

n

Independent air source

Protective Clothing. A diver needs some form of protection from cold water to

counter heat loss during long exposure in water of moderate temperature and from
the hazards posed by marine life and underwater obstacles. Wet suit, or a dry suit
with or without thermal underwear in Figure 7-8 can provide protection.

7‑4.1.1

Wet Suits. The wet suit is a form-fitting suit, usually made of closed-cell neoprene.

Custom-fitted wet suits are recommended since they provide the greatest freedom
of movement, and thermal protection.
The suit traps a thin layer of water next to the diver’s skin, where it is warmed
by the diver’s body. Wet suits are available in a variety of thicknesses and the
thicker the suit the better the insulation (and the greater the buoyancy). A diver
wearing a thicker wetsuit will fatigue more easily and use more air, which must be
accounted for in dive planning. The buoyancy of a wetsuit must be countered by
adding weight to the diver.
Because wet suits are closed-cell construction they will compress in compliance
with Boyle’s law and lose buoyancy and the ability to thermally protect the diver.
The deeper the dive, the greater the effect of Boyle’s Law on the suit. As a diver
ascends at the end of a dive, the wet suit buoyancy is restored and the diver may
lose control of the ascent, particularly in the last 30fsw where the greatest change
in pressure occurs. This effect is compounded if the diver has depleted most of the
air in the tanks and is positively buoyant as a result.

CHAPTER 7 — SCUBA Air Diving Operations

7-17

7‑4.1.2

Variable Volume Dry Suits. The Variable Volume Dry Suit (VVDS) has proven

to be effective in keeping divers warm in near-freezing water. It is typically
constructed of 1/4-inch closed-cell neoprene with nylon backing on both sides.
Boots are provided as an integral part of the suit, but the hood and three finger
gloves are usually separate. The dry suit keeps the diver dry, but it is the thermal
insulation worn under the suit that insulates the diver and provides warmth.
Inflation is controlled using inlet and outlet valves, which are fitted into the suit. Air
is supplied from a pressure reducer on an auxiliary cylinder, from the emergency
gas supply, or the SCUBA bottle. About 0.2 actual cubic foot of air is required for
normal inflation. Because of this inflation, slightly more weight than would be used
with a wet suit must be carried.
Wet or dry suits can be worn with hoods, gloves, boots, or hard-soled shoes
depending upon conditions. If the diver will be working under conditions where the
suit may be easily torn or punctured, the diver should be provided with additional
protection such as coveralls or heavy canvas chafing gear.
Divers must train and be proficient with dry suit use before conducting operational
dives. A thorough understanding of the unique buoyancy characteristics of the
dry suit is critical to operating effectively. Inflation and dump valves must not
be obstructed and the diver must know their location. The diver must understand
that performing head down descents and operating in a horizontal and head down
position will lead to air migrating to the feet and result in blow up.
Wet Suit

Dry Suit

Water warmed to
body temperature

Underclothing affords
insulating air space

Leg

Foam Neoprene
(insulator)

Leg

Sheet Rubber

Figure 7-8. Protective Clothing.

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U.S. Navy Diving Manual — Volume 2

7‑4.1.3

Gloves. Gloves are an essential item of protective clothing. They can be made

7‑4.1.4

Writing Slate. A rough-surfaced sheet of acrylic makes an excellent writing slate

7‑4.1.5

Signal Flare. A signal flare is used to attract attention if the diver has surfaced

7‑4.1.6

Acoustic Beacons. Acoustic beacons or pingers are battery-operated devices that

7‑4.1.7

Lines and Floats. A lifeline is used when it is necessary to exchange signals,

of leather, cloth, or rubber, depending upon the degree and type of protection
required. Gloves shield the hands from cuts and chafing, and provide protection
from cold water. Some styles are designed to have insulating properties but may
limit the diver’s dexterity.

for recording data, carrying or passing instructions, and communicating between
divers. A grease pencil or graphite pencil should be attached to the slate with a
lanyard.

away from the support crew. Any waterproof flare that can be carried and safely
ignited by a diver can be used, but the preferred type is the MK 99 MOD 3
(NSN 1370-01-177-4072; pouch is NSN 1370-01-194-0844). These are day-ornight flares that give off a heavy orange smoke for day time and a brilliant red
light at night. Each signal lasts for approximately 45 seconds and will withstand
submersion up to depths of 200 fsw without adverse effects. A hexagon shaped
end cap marked SMOKE is threaded into the smoke assembly and a round shaped
end cap with eight grooves marked FLARE is threaded onto the flare assembly.
Also available are the MK 131 MOD 0 (NSN 1370-01-252-0318) and MK 132
MOD 0 (NSN1370-01-252-0317). The MK 131 is for day time distress signaling
while the MK 132 is for night. The only difference between the MK 99 and the
MK 131/132, other than the fact that the MK 99 is a combined day/night signal
flare which gives off yellow smoke and light, is that the MK 99 satisfies magnetic
effect limits of MIL-M-19595 for explosive ordnance disposal (EOD) usage.
Flares should be handled with care. For safety, each diver should carry a maximum
of two flares. All divers/combat divers engaged in submarine Dry Deck Shelter
operations should stow flares in hangar prior to reentering the host submarine.
emit high-frequency signals when activated. The devices may be worn by divers to
aid in keeping track of their position or attached to objects to serve as fixed points
of reference. The signals can be picked up by hand-held sonar receivers, which are
used in the passive or listening mode, at ranges of up to 1,000 yards. The handheld sonar enables the search diver to determine the direction of the signal source
and swim toward the pinger using the heading noted on a compass.

keep track of the diver’s location, or operate in limited visibility. Always attach a
lifeline snugly and securely around the diver’s waist, or to a safety harness worn
under the SCUBA equipment, and never to a piece of equipment that may be
ripped away or may be removed in an emergency. Use of a mechanical connector
(locking carabiner) is authorized provided the connector is securely fastened to a
harness (not a piece of equipment) or around the diver’s waist and back to a loop
in the lifeline which prevents the line from loosening and falling off the diver’s
waist. There are three basic types of lifelines:

CHAPTER 7 — SCUBA Air Diving Operations

7-19

n Tending line. Required for standby diver and single divers. Required when
direct access to the surface is not available.
n Float line. May be used instead of a tending line only when direct access to
the surface is available. The float line reaches from the diver to a suitable
float on the surface. The surface float should be no smaller than an 11 inch
inflatable buoy, or similar, and be brightly colored to be easily visible in open
seas (international orange is recommended). An inner tube with a diving flag
attached makes an excellent float and provides a hand-hold for a surfaced
diver.
n Buddy line. A buddy line, providing six to ten feet of separation between
divers, may be used to connect dive partners at night or when visibility is
poor. May be used with a tending line or float line. A buddy line may be used
with a tending line or float line but the dive supervisor must evaluate the
possibility of introducing a fouling hazard as a result.
Lifelines should be strong and be sized appropriately for the task. Buddy lines and
float lines are lifelines and as such, shall be secured to the diver as stated above.
Nylon, Dacron, and polypropylene are all suitable materials.
7-4.1.8

Snorkel. A snorkel is a simple breathing tube that allows a diver to swim on the
surface for long or short distances face-down in the water. This permits the diver to
search shallow depths from the surface, conserving the SCUBA air supply. When
snorkels are used for skin diving, they are often attached to the face mask with a
lanyard or rubber connector to the opposite side of the regulator.

7-4.1.9

Compass. Small magnetic compasses are commonly used in underwater

7‑4.1.10

Dive Computers. Dive computers have proven useful in the optimization and

7-4.1.11

Independent Secondary Air Source. Dive Supervisors shall consider outfitting

navigation. Such compasses are not highly accurate, but can be valuable when
visibility is poor. Submersible wrist compasses, watches, and depth gauges covered
by NAVSUPINST 5101.6 (series) are items controlled by the Nuclear Regulatory
Commission and require leak testing and reporting every 6 months.

management of dive time and decompression. Only ANU approved dive computers
may be used in lieu of decompression tables. Proper training and strict adherence
to specific guidelines regarding the various dive computers shall be followed.
Dive computers are not a substitute for ORM. Proper planning of the dive remains
the responsibility of the Dive Supervisor. See the ANU and Appendix 2B for more
information regarding dive computers.
each diver with an independent secondary air source to provide a back-up should
the diver experience an equipment malfunction or be forced to ditch the primary
apparatus.

An independent air source is a DOT specification type 3AA or 3AL cylinder with a
minimum capacity of 19scf and an ANU approved first and second stage regulator.
Independent air source cylinders may be sized from 19scf to 50scf. Independent air

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U.S. Navy Diving Manual — Volume 2

sources may be secured to the diver, the life preserver or B.C. with commercially
available harnesses, packs, or straps.
7-5

AIR SUPPLY

Air used in Navy SCUBA dives shall meet the requirements of Table 4-1 or
paragraph 4-3.1.
Air supply is typically computed during dive planning based on an average
respiratory minute volume (RMV) of 1.4 cubic feet per minute (CFM). During
execution however, the tasks and conditions at the dive site may cause a particular
diver to experience RMV rates much higher than average. Therefore, the Dive
Supervisor shall compute the air supply duration before each SCUBA dive and use
a conservative estimate of RMV based on the factors listed in Paragraph 7-5.1 and
Figure 3-6.
WARNING:		

7-5.1

When calculating duration of air supply, an adequate safety margin shall
be factored in. The deeper the dive, the more critical it is to ensure divers
have sufficient air to reach the surface in the event of a mishap. Dive
Supervisors shall consider outfitting each diver with an independent
secondary air source to provide a back-up should the diver experience
an equipment malfunction or be forced to ditch the primary apparatus.
Relying solely on a reserve may leave a diver with insufficient air to reach
the surface.
Duration of Air Supply. The duration of the air supply of any given cylinder or

combination of cylinders depends upon:

n The diver’s consumption rate, which varies with the diver’s work rate.
n The depth of the dive.
n The capacity and pressure of the cylinder(s).
n The surface to bottom temperature differential.
Work rate may be influenced by:
n Water temperature
n Thickness of thermal protection
n Currents and visibility
n Nature of tasks and the diver’s experience performing them
n Diver’s physical fitness
n Diver’s actual experience with SCUBA, the environment, and task
n How current the diver’s experience is

CHAPTER 7 — SCUBA Air Diving Operations

7-21

Temperature correction is usually not performed in calculating air available unless
there is a significant differential in surface cylinder temperatures and bottom
temperatures. Where the possibility of significant temperature differentials may
exist, cylinder and bottom temperatures should be taken to determine if correction
is appropriate in accordance with paragraph 2-11.3.
For example, a dive conducted to 150fsw on twin 80 aluminum cylinders at 3000psi
where the bottom temperature is 45 degrees F and the temperature of the bottles on
surface is 90 degrees F results in a bottom time reduction of 2 minutes.
There are three steps in calculating how long a diver’s air supply will last:
1. Calculate the diver’s consumption rate by using this formula:

C=

D + 33
× RMV
33

Where:
C
=
D
=
RMV =

Diver’s consumption rate, standard cubic feet per minute (scfm)
Depth, fsw
Diver’s Respiratory Minute Volume, actual cubic feet per minute
(acfm) (from Figure 3-6)

2. Calculate the available air capacity provided by the cylinders. The air capacity

must be expressed as the capacity that will actually be available to the diver,
rather than as a total capacity of the cylinder. The formula for calculating the
available air capacity is:

Where:
Pc = Measured cylinder pressure, psig (temperature correction should be
			 considered)
Pm

=

Minimum pressure of cylinder, psig

FV =

Floodable Volume (scf)

N

=

Number of cylinders

Va

=

Capacity available (scf)

3. Calculate the duration of the available capacity (in minutes) by using this

formula:

Duration =

Va
C

Where:
Va = Capacity available, scf
C = Consumption rate, scfm

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U.S. Navy Diving Manual — Volume 2

Sample Problem. Determine the duration of the air supply of a diver doing moderate

work at 70 fsw using twin 72-cubic-foot steel cylinders charged to 2,250 psig.

1. Calculate the diver’s consumption rate in scfm. According to Figure 3-6, the

diver’s consumption rate at depth is 1.4 acfm.

D + 33
× RMV
33
70 + 33
=
× 1.4
33
= 4.37 scfm

C=

2. Calculate the available air capacity provided by the cylinders. Table 7‑1

contains the cylinder data used in this calculation:

n Floodable Volume = 0.420 scf
n Rated working pressure = 2250 psig
n Reserve pressure for twin 72-cubic-foot cylinders = 250 psig

3. Calculate the duration of the available capacity.

Va
C
114 scf
=
4.37 scfm
= 26 minutes

Duration =

The total time for the dive, from initial descent to surfacing at the end of the
dive, is limited to 26 minutes.
7-5.2

Methods for Charging SCUBA Cylinders.

NOTE

Paragraph 7-5.4 addresses safety precautions for charging and handling
cylinders.

SCUBA cylinders shall be charged only with air that meets diving air purity
standards. A diving unit can charge its own cylinders by one of two accepted
methods: (1) by cascading or transferring air from banks of large cylinders into

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7-23

the SCUBA tanks; or (2) by using a high-pressure air compressor. Cascading is the
fastest and most efficient method for charging SCUBA tanks. The NAVSEA/00C
ANU list lists approved high-pressure compressors and equipment authorized for
SCUBA air sources.
The normal cascade system consists of supply flasks connected together by a
manifold and feeding into a SCUBA high-pressure whip. This whip consists of a
SCUBA yoke fitting, a pressure gauge, and a bleed valve for relieving the pressure
in the lines after charging a cylinder. A cascade system, with attached whip, is
shown in Figure 7-9.
SCUBA charging lines shall be fabricated using SAE 100R7 hose for 3,000 psi
service and SAE 100R8 hose for 5,000 psi service. The service pressure of the
SCUBA charging lines shall be no greater than the working pressure of the hose
used.
The working pressure of a hose is determined as one-fourth of its burst pressure.
While this criteria for working pressure was developed based on the characteristics
of rubber hose, it has also been determined to be appropriate for use with the plastic
hoses cited above.
Fleet units using charging lines shall not exceed the rated working pressure
of the hose. If the charging line working pressure rating does not meet service
requirements, restrict the service pressure of the hose to its working pressure and
initiate replacement action immediately.
The use of strain reliefs made from cable, chain, 21-thread, or 3/8-inch nylon,
married at a minimum of every 18 inches and at the end of the hose, is a required
safety procedure to prevent whipping in the event of hose failure under pressure.
Marrying cord shall be 1/8-inch nylon or material of equivalent strength. Tie wraps,
tape, and marlin are not authorized for this purpose.

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Manifold Gauge
Flask Manifold
High Pressure Hose
Charging
Valve

Gauge
Shut-Off
Valve

Bleed
Valve
On/Off
Valve

Water
Tank

SCUBA Cylinders

A

B

C

D

E

F

High Pressure Air Flasks

Figure 7-9. Cascading System for Charging SCUBA Cylinders.

7-5.3

Operating Procedures for Charging SCUBA Tanks. Normally, SCUBA tanks are

charged using the following operating procedures (OPs), which may be tailored to
each unit:

1. Determine that the cylinder is within the hydrostatic test date.
2. Check the existing pressure in the SCUBA cylinder with an accurate pressure

gauge.

3. Attach the cylinder to the yoke fitting on the charging whip, and attach the

safety strain relief.

4. For safety and to dissipate heat generated in the charging process, when

facilities are available, immerse the SCUBA cylinder in a tank of water while
it is being filled. A 55-gallon drum is a suitable container for this purpose.

5. Tighten all fittings in the system.
6. Close the bleed valve.
7. Place reserve mechanism lever in the open (lever down) position.
8. Open the cylinder (on/off) valve. This valve is fully opened with about two

turns on the handle, counter-clockwise. However, the valve must not be used
in a fully open position as it may stick or be stripped if force is used to open a
valve that is incorrectly believed to be closed. The proper procedure is to open

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7-25

the valve fully and then close or back off one-quarter to one-half turn. This will
not impede the flow of air.
9. Open the supply flask valve.
10. Slowly open the charging valve. The sound of the air flowing into the SCUBA

cylinder is noticeable. The operator will control the flow so that the pressure
in the cylinder increases at a rate not to exceed 400 psig per minute. If unable
to submerge SCUBA cylinders during charging, the charging rate must not
exceed 200 psig per minute. The rate of filling must be controlled to prevent
overheating; the cylinder must not be allowed to become too hot to touch.

11. Monitor the pressure gauge carefully. When the reading reaches the rated

pressure for the SCUBA cylinder, close the valve on the first cylinder and take
a reading.

12. Close the charging valve.
13. Close the on/off valve on the SCUBA cylinder.
14. Ensure that all valves in the system are firmly closed.
15. Let the SCUBA cylinder cool to room temperature. Once the cylinder is cool,

the pressure will have dropped and you may need to top off the SCUBA
cylinder.

7‑5.3.1

Topping off the SCUBA Cylinder. Follow this procedure to top off a SCUBA

cylinder:

1. Open the on/off valve on the SCUBA cylinder.
2. Select a supply flask with higher pressure than the SCUBA rated limit.
3. Open the supply valve on the flask.
4. Throttle the charging valve to bring the SCUBA cylinder up to the rated limit.
5. Close all valves.
6. Open the bleed valve and depressurize the lines.
7. When air has stopped flowing through the bleed valve, disconnect the SCUBA

cylinder from the yoke fitting.

8. Reset the reserve mechanism (lever in up position).

In the absence of high-pressure air systems, large-volume air compressors can be
used to charge SCUBA cylinders directly. However, few compressors can deliver
air in sufficient quantity at the needed pressure for efficient operation. Small
compressors should be used only if no other suitable source is available.
If a suitable compressor is available, the basic charging procedure will be the same
as that outlined for cascading except that the compressor will replace the bank of
cylinders.
Additional information on using air compressors is found in Chapter 4.

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U.S. Navy Diving Manual — Volume 2

7-5.4

Safety Precautions for Charging and Handling Cylinders. The following safety

rules apply to charging and handling SCUBA cylinders:

n Carry cylinders by holding the valve and body of the cylinder. Avoid carrying
a cylinder by the backpack or harness straps as the quick-release buckle can
be accidentally tripped or the straps may fail.
n Do not attempt to fill any cylinder if the hydrostatic test date has expired or
if the cylinder appears to be substandard. Dents, severe rusting, bent valves,
frozen reserve mechanisms, or evidence of internal contamination (e.g.,
water scales or rust) are all signs of unsuitability. See CGA Pamphlet C-6,
Standards for Visual Inspection of Compressed Gas Cylinders.
n Always use gauges to measure cylinder pressure. Never point the dial of a
gauge to which pressure is being applied toward the operators face.
n Never work on a cylinder valve while the cylinder is charged.
n Make sure that the air reserve mechanism is open (lever down) before
charging.
n Use only compressed air for filling conventional SCUBA cylinders. Never
fill SCUBA cylinders with oxygen. Air is color-coded black, while oxygen
is color-coded green.
n Tighten all fittings before pressurizing lines.
n When fully charged, close the air reserve (lever up). Mark the filled tank to
indicate the pressure to which it was charged.
n Handle charged cylinders with care. If a charged cylinder is damaged or if
the valve is accidentally knocked loose, the cylinder tank can become an
explosive projectile. A cylinder charged to 2,000 psi has enough potential
energy to propel itself for some distance, tearing through any obstructions in
its way.
n Store filled cylinders in a cool, shaded area. Never leave filled cylinders in
direct sunlight.
n Cylinders should always be properly secured aboard ship or in a diving boat.
7-6

PREDIVE PROCEDURES

Predive procedures for SCUBA operations include equipment preparation, dive
brief, donning gear, and a predive inspection before the divers enter the water. The
SCUBA diving operations setup checklist (Figure 7-11), and Dive Supervisor’s
predive checklist (Figure 7-12) presented in this chapter are examples of U.S.Navy
material and may be used as provided or modified locally to suit specific needs.

CHAPTER 7 — SCUBA Air Diving Operations

7-27

7-6.1

Equipment Preparation. Prior to any dive, all divers must carefully inspect their

own equipment for signs of deterioration, damage, or corrosion. The equipment
must be tested for proper operation. Predive preparation procedures must be
standardized, not altered for convenience, and must be the personal concern of
each diver.
7‑6.1.1

Air Cylinders.

n Inspect air cylinder exteriors and valves IAW PMS.
n Inspect cylinder valve for the presence of an O-ring.
n Verify that the reserve mechanism is closed (lever in up position) signifying
a filled cylinder ready for use.
n Gauge the cylinders according to the following procedure:
1. Attach pressure gauge to O-ring seal face of the on/off valve.
2. Close gauge bleed valve and open air reserve mechanism (lever in

down position). Slowly open the cylinder on/off valve, keeping a
cloth over the face of the gauge.

3. Read pressure gauge. The cylinder must not be used if the pressure

is not sufficient to complete the planned dive.

4. Close the cylinder on/off valve and open the gauge bleed valve.
5. When the gauge reads zero, remove the gauge from the cylinder.
6. Close the air reserve mechanism (lever in up position).
7. If the pressure in cylinders is 50 psi or greater over rating, open the

cylinder on/off valve to bleed off excess and regauge the cylinder.

7‑6.1.2

Harness Straps and Backpack.

n Check for signs of rot and excessive wear.
n Adjust straps for individual use and test quick-release mechanisms.
n Check backpack for cracks and other unsafe conditions.
7‑6.1.3

Breathing Hoses.

n Check the hoses for cracks and punctures.
n Test the connections of each hose at the regulator and mouthpiece assembly
by attempting to unscrew the fittings by hand.
n Check the clamps for corrosion, damage, and signs of separation; replace as
necessary and in accordance with PMS procedures.

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7‑6.1.4

Regulator.
1. Ensure over-bottom pressure of first stage regulator has been set IAW PMS.
2. Attach regulator to the cylinder manifold, ensuring that the O-ring is properly

seated.

3. Crack the cylinder valve open and wait until the hoses and gauges have

equalized.

4. Next open the cylinder valve completely and then close (back off) one-quarter

turn.

5. Check for any leaks in the first stage regulator by listening for the sound of

escaping air. If a leak is suspected, determine the exact location by submerging
the valve assembly and the regulator in a tank of water and watch for escaping
bubbles. Frequently the problem can be traced to an improperly seated regulator
and is corrected by closing the valve, bleeding the regulator, detaching and
reseating. If the leak is at the O-ring and reseating does not solve the problem,
replace the O-ring and check again for leaks.

7‑6.1.5

Life Preserver/Buoyancy Compensator (BC).

n Orally inflate preserver to check for leaks and then squeeze out all air. The
remaining gas should be removed after entry into the water by rolling onto
the back and depressing the oral inflation tube just above the surface. Never
suck the air out, as it may contain excessive carbon dioxide.
n Inspect the carbon dioxide cartridges to ensure they have not been used
(seals intact) and are the proper size for the vest being used and for the depth
of dive.
n The cartridges shall be weighed in accordance with the Planned Maintenance
System.
n The firing pin should not show wear and should move freely.
n The firing lanyards and life preserver straps must be free of any signs of
deterioration.
n When the life preserver inspection is completed, place it where it will not be
damaged. Life preservers should never be used as a buffer, cradle, or cushion
for other gear.
7‑6.1.6

Face Mask.

n Check the seal of the mask and the condition of the head strap.
n Check for cracks in the skirt and faceplate.
7‑6.1.7

Swim Fins.

n Check straps for signs of cracking.

CHAPTER 7 — SCUBA Air Diving Operations

7-29

n Inspect blades for signs of cracking.
7-6.1.8

Dive Knife.

n Ensure knife is sharp.
n Ensure the knife is fastened securely in the scabbard.
n Verify that the knife can be removed from the scabbard without difficulty,
but will not fall out.
7-6.1.9

Snorkel.

n Inspect the snorkel for obstructions.
n Check the condition of the mouthpiece.
7-6.1.10

Weight Belt.

n Check the condition of the weight belt.
n Make sure that the proper number of weights are secure and in place.
n Verify that the quick-release buckle is functioning properly.
7‑6.1.11

Submersible Wrist Watch.

n Ensure wrist watch is set to the correct time.
n Inspect the pins and strap of the watch for wear.
7‑6.1.12

Depth Gauge and Compass.

n Inspect pins and straps.
n If possible, check compass with another compass.
n Make comparative checks on depth gauges to ensure depth gauges read zero
fsw on the surface.
n Zero the maximum depth indicator if so equipped.
7‑6.1.13

Miscellaneous Equipment.

n Inspect any other equipment that will be used on the dive as well as any spare
equipment that may be needed during the dive including spare regulators,
cylinders, and gauges.
n Check all protective clothing, lines, tools, flares, and other optional gear.

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U.S. Navy Diving Manual — Volume 2

7-6.2

Dive Brief. When the divers have inspected and tested their equipment, they report

to the Diving Supervisor. The divers shall be given a predive briefing of the dive
plan. Mission brief and dive brief are discussed in Section 6-6.
When the Diving Supervisor determines that all requirements for the dive are met,
the divers may dress for the dive.
7-6.3

Donning Gear. Although SCUBA divers should be able to put on all gear

themselves, the assistance of a tender is encouraged. Dressing sequence is
important as the weight belt must be outside of all backpack harness straps and
other equipment in order to facilitate its quick release in the event of an emergency.
The following is the recommended dressing sequence:

1. Protective clothing. Ensure adequate protection is worn. Coveralls may provide

protection from abrasions in warm waters.

2. Booties, and hood if required.
3. Dive knife. Attached in a manner so it cannot be jettisoned.
4. Life preserver, with inflation tubes in front and the actuating lanyards exposed

and accessible.

5. SCUBA. Most easily donned with the tender holding the cylinders in position

while the diver fastens and adjusts the harness. The SCUBA should be worn
centered high on the diver’s back but not so high as to interfere with head
movement. All quick-release buckles must be positioned so that they can be
reached by either hand. All straps must be pulled snug so the cylinders are
held firmly against the body. The ends of the straps must hang free so the
quick-release feature of the buckles will function. If the straps are too long,
they should be cut and the ends whipped with small line or a plastic sealer. At
this time, the cylinder on/off valve should be opened fully and then backed
off one-quarter to one-half turn, and the reserve mechanism should be cycled
to the down position and back up. Ensure the buoyancy compensator whip is
connected to the buoyancy compensator.

6. Accessory equipment (diving wrist watch, pressure/depth gauge, snorkel).
7. Weight belt.
8. Gloves.
9. Swim fins.
10. Lifeline snugly secured around the diver’s waist, or attached to a harness.
11. Mask.
7-6.4

Predive Inspection. The divers report to the Diving Supervisor for a final

inspection. During this final predive inspection the Diving Supervisor shall:

1. Ensure that the divers are physically and mentally ready to enter the water.
2. Verify that all divers have all minimum required equipment.
3. Verify and record the cylinder pressure and that the volume of available air is

sufficient for the planned duration of the dive.

CHAPTER 7 — SCUBA Air Diving Operations

7-31

4. Ensure that all quick-release buckles and fastenings can be reached and are

properly rigged for quick release.

5. Verify weights are installed in the proper BC prockets, or that the weight belt is

outside of all other belts, straps, and equipment, and will not become pinched
under the bottom edge of the cylinders.

6. Verify that the life preserver or buoyancy compensator is not constrained and

free to expand, and that all air has been evacuated.

7. Check position of the knife to ensure that it will remain with the diver no matter

what equipment is left behind.

8. Ensure that the cylinder valve is open fully and backed off one-quarter to one-

half turn.

9. Ensure that the hose supplying air passes over the diver’s right shoulder.
10. With mouthpiece or fullface mask in place, breathe in and out for several

breaths, ensuring that the demand regulator and check valves are working
correctly.

11. Depress and release the purge button at the mouthpiece and listen for any sound

of leaking air. Breathe in and out several times ensuring valves are working
correctly.

12. Give the breathing hose and mouthpiece a final check; ensure that none of the

connections have been pulled open during the process of dressing.

13. Check that the air reserve mechanism lever is up (closed position).
14. Conduct a brief final review of the dive plan.
15. Verify that dive signals are displayed and personnel and equipment are ready to

signal other vessels in the event of an emergency.

7-7

WATER ENTRY AND DESCENT
7-7.1

Water Entry. There are several ways to enter the water, with the choice usually

determined by the nature of the diving platform (Figure 7-10). Whenever possible,
entry should be made by ladder, especially in unfamiliar waters. Several basic
rules apply to all methods of entry:
n Look before jumping or pushing off from the platform or ladder.
n Tuck chin into chest and hold the cylinders with one hand to prevent the
manifold from hitting the back of the head.
n Hold the mask in place with the fingers and the mouthpiece in place with the
heel of the hand.
7‑7.1.1

7-32

Step-In Method. The step-in method is the most frequently used, and is best used

from a stable platform or vessel. The divers should simply take a large step out
from the platform, keeping legs in an open stride. They should try to enter the
water with a slightly forward tilt of the upper body so that the force of entry will
not cause the cylinder to hit the back of the head.

U.S. Navy Diving Manual — Volume 2

Front jump or step-in. On edge of platform, one
hand holding face mask and regulator, the other
holding the cylinders, the diver takes a long step
forward, keeping his legs astride.

Rear roll. The diver, facing inboard, sits on the
gunwale. With chin tucked in, holding his mask,
mouthpiece, and cylinders, the diver rolls backwards.

Side roll. Tender assists diver in taking a seated
position. Tender stabilizes the diver as diver holds
mask and cylinders and rolls into the water.

Front roll. Diver sits on edge of platform with
a slight forward lean to offset the weight of the
cylinders. Holding his mask and cylinders, the diver
leans forward.

Figure 7-10. SCUBA Entry Techniques.

CHAPTER 7 — SCUBA Air Diving Operations

7-33

SCUBA DIVING OPERATIONS SETUP CHECKLIST
(Sheet 1 of 2)

A. INITIAL PREPARATION:
o Conduct mission brief (if not part of dive brief)
o Verify that a recompression chamber is ready and notified of diving operations.
o Ensure that all personnel concerned, and in the vicinity, are informed of diving operations.
o Ensure completion of Ship Repair Safety Checklist for Diving if required.
o Post emergency Assistance Checklist
o Alpha/ Diver down flags / Day shapes
B. DIVE EQUIPMENT:
Assemble and lay out all dive equipment and spares.
Minimum equipment
o
o
o
o
o
o

SCUBA regulator assemblies		
o
Octopus for standby			
o
Life preserver / buoyance compensator
o
Weight belt/Weights as required		
o
Depth Gauge				o
Fins 					o

SCUBA cylinders
Submersible pressure gauge
Knife
Watch
Mask
Standby diver tending line

o Predive checks completed in accordance with PMS, or manufacture’s technical manual?
Additional equipment
o
o
o
o
o

Tending/float lines/buddy lines - adequate length for depth/job
Lights and batteries		
o Lift bags
Working lines			
o Tools
Wetsuit/Drysuit			
o Spares kit (o-rings, fin straps, etc)
Primary egress; ladder, small boat, etc.

C. ASSEMBLE EMERGENCY EQUIPMENT:
o Dive site specific method to extract unconscious diver from the water. (Extraction line and harness or
stage may be required. Rescue strops are not designed for unconscious victims.)
o Recall device. Charged/tested?
o Lost Diver kit
o Clump. Weight sufficient for size of float.
o Line. Length sufficient for depth of water (polypropylene recommended)
o Buoy (11 inch minimum diameter)
o Circling line. (25 feet minimum length.)
o First Aid kit				o AED with towel and razor. Charged?
o Portable oxygen supply. psi____________

o Bag Valve mask (AMBU)

o Emergency communication			

o Stretcher/backboard

o SAT phone/Cell phone			
o VHF radio

Figure 7‑11. SCUBA Diving Operations Setup Checklist (Sheet 1 of 2).

7-34

U.S. Navy Diving Manual — Volume 2

SCUBA DIVING OPERATIONS SETUP CHECKLIST
(Sheet 2 of 2)

D. SMALL BOAT:
o Operating condition: Motor, steering, battery, bilge pumps, lights.
o Working VHF marine radio or handheld
o Support for flags
o Adequate fuel				o Paddles		
o Tool kit					o Radar reflector
o Boat capacity not exceeded			
o Binoculars		

o
o
o
o

GPS / compass
Life jackets
Fire extinguisher
Anchor and line

E. SCUBA CYLINDERS AND CHARGING STATION:
General.
o Charging area is segregated from personnel.
o Sufficient cylinder storage to prevent loose cylinders.
o Charging area/cylinder storage area is shaded from the sun.
o Method to cool cylinders while charging.
o Charging procedure posted.
Cylinders.
o
o
o
o

Hydrostatic test dates are current.
Visual inspection within last year.
Valves and reserve mechanisms operate without binding.
Gauge all cylinders, segregate and charge cylinders as required.

Compressors.
o
o
o
o
o
o
o
o

Compressor is ANU listed.
Air sample on compressor within periodicity?
Compressors prepared for use IAW posted operating procedures and PMS?
Sufficient fuel, lubricants and coolant available?
Compressor operating log available.
Compressor secure in diving craft and not subject to operating angles exceeding 15 degrees.
Compressor exhaust is vented away from work areas and, does not foul the compressor intake.
Charging whips have proper leads, do not pass near heat sources, are free of kinks and bends, and are
not exposed on deck in such a way that they can be rolled over, damaged, or severed.
o Verify that charging whips have safety lines and strain reliefs properly attached.
F. FINAL PREPARATIONS.
o Verify that all necessary records, logs, and decompression tables are on the dive station.
o Conduct communications check with boat crew, recompression chamber, ship’s personnel, and
command.
o Verify that proper signals indicating underwater operations are displayed. Rigid Alpha/Code-Alpha,
Civilian “Diver Down”, displayed a minimum of 3 feet off the water.
o Conduct Dive Brief. Assemble all members of the diving team for a predive briefing.

Figure 7‑11. SCUBA Diving Operations Setup Checklist (Sheet 2 of 2).

CHAPTER 7 — SCUBA Air Diving Operations

7-35

7-36

7‑7.1.2

Rear Roll Method. The rear roll is the preferred method for entering the water

7‑7.1.3

Front Roll Method. The front roll method is only appropriate when the freeboard

7-7.1.4

Side Roll Method. The side roll method, like the front roll, is only appropriate

7-7.1.5

Entering the Water from the Beach. Divers working from the beach choose their
method of entry according to the condition of the surf and the slope of the bottom.
If the water is calm and the slope gradual, the divers can walk out carrying their
swim fins until they reach water deep enough for swimming. In a moderate to
high surf, the divers, wearing swim fins, should walk backwards into the waves
until they have enough depth for swimming. They should gradually settle into the
waves as the waves break around them.

from a small boat because it is the most stable for the diver. A fully outfitted diver
standing on the edge of a boat would upset the stability of the craft and would
be in danger of falling either into the boat or into the water. To execute a rear
roll, the diver sits on the gunwale of the boat, facing inboard. With chin tucked
in and one hand holding the mask and mouthpiece in place, the diver slides back
on the gunwale and into the water posterior first and avoids moving through a full
backward somersault.

of the platform is minimal. Divers should not perform this method if there is more
than one or two feet distance between the platform and the water surface. In the
front roll, the diver sits on the edge of the platform with a slight forward lean to
offset the weight of the cylinders. Holding the mask and cylinders, the diver leans
forward and enters the water.
when the freeboard of the platform is minimal. The side roll method exposes the
diver to destabilizing forces as the boat rocks side to side in open seas and may not
be appropriate when there are insufficient tenders to assist in stabilizing the divers.
In the side roll, the diver sits on the edge of the platform with assistance from the
tender. Holding the mask and cylinders, the diver leans forward and enters the
water.

U.S. Navy Diving Manual — Volume 2

DIVE SUPERVISORS PRE-DIVE CHECKLIST
PROCEDURES

DV 1

DV2

STBY

Minimum Equipment:
Tank
Regulator
Life Jacket or BC
Depth Gauge
Mask, Fins
Pressure Gauge
Knife
Watch
Weights as Required
Fully Open Cylinder Valve / Back 1/4 Turn Cycle Reserve / Leave in
up Position
Cylinder Pressures
Quick Releases /Buckles properly rigged:
C02 Cartridges weighed and installed (if used):
Check Life Jacket/BC
Not Constrained
Manual Inflator
Power Inflator
Dump Valves
Weights properly installed or Weight Belt outside all other straps and
equipment
Lifeline attached around waist or to harness - not attached to equipment
Ensure knife cannot be jettisoned
Tuck Submersible Pressure Gauge:
Zero the Maximum Depth Indicator:
Set Watches in Stopwatch Mode:
Purge and Breathe all Regulators
Octopus Secured on or near Divers Chest
Conduct Supervisor Hands On Checks
Dive Supervisor Signature

Date

Figure 7-12. Dive Supervisor Pre-Dive Checklist.

7-7.2

In-Water Checks. Once in the water, and before descending the divers make a final

check of their equipment. They must:

n Make a breathing check of the SCUBA. There should be little breathing
resistance and no evidence of water leaks.
n Visually check dive partner’s equipment for leaks, especially at all connection
points (i.e., cylinder valve, hoses at regulator and mouthpiece).

CHAPTER 7 — SCUBA Air Diving Operations

7-37

n Check partner for loose or entangled straps.
n Check face mask seal. A small amount of water may enter the mask upon
the diver’s entry into the water. The mask may be cleared through normal
methods (see paragraph 7-8.2).
n Check buoyancy. SCUBA divers should strive for neutral buoyancy. Extra
equipment or heavy tools should be lowered and raised on a line if possible
to avoid adversely affecting the divers buoyancy.
n If wearing a dry suit, check for leaks. Adjust suit inflation for proper
buoyancy.
n Orient position with the compass or other fixed reference points.
When ready to descend, the divers report to the Diving Supervisor. The Diving
Supervisor directs the divers to zero their watches and bottom time begins. The
Diving Supervisor gives the signal to descend and the divers descend below the
surface.
7-7.3

Surface Swimming. The diving boat should be moored, or stationed, as near to

the dive site as possible. While swimming, dive partners must keep visual contact
with each other and other divers in the group. They should be oriented to their
surroundings to avoid swimming off course. The most important factor in surface
swimming with SCUBA is to maintain a relaxed pace to conserve energy. The
divers should keep their masks on and breathe through the snorkel. When surface
swimming with a SCUBA regulator, hold the mouthpiece so that air does not freeflow from the system.
Divers should use only their legs for propulsion and employ an easy kick from the
hips without lifting the swim fins from the water. Divers can rest on their backs and
still make headway by kicking. Swimming assistance can be gained by partially
inflating the life preserver or buoyancy compensator. However, the preserver must
be deflated again before the dive begins.

7-7.4

Descent. The divers may swim down or they may use a descending line to pull

themselves down. If either diver experiences difficulty in clearing, both divers
must stop and ascend until the situation is resolved. If the problem persists, or if
the problem is sinus related, the dive shall be aborted and both divers shall return
to the surface. The rate of descent will generally be governed by the ease with
which the divers will be able to equalize the pressure in their ears and sinuses, but
it should never exceed 75 feet per minute.
Upon reaching the operating depth, the divers must orient themselves to their
surroundings, verify the site, and check the underwater conditions. If conditions
appear to be radically different from those anticipated or if they call for a significant
change in the dive plan, the dive should be aborted and the conditions reported to
the Diving Supervisor. The divers should discuss the situation with the Diving
Supervisor and the dive plan should be modified or the mission aborted if warranted.

7-38

U.S. Navy Diving Manual — Volume 2

7-8

UNDERWATER PROCEDURES

In a SCUBA dive, bottom time is at a premium because of a limited supply of
air. Divers must pace their work, conserve their energy, and take up each task or
problem individually. At the same time they must be flexible. They must be ready
to abort the dive at any time they feel that they can no longer progress toward the
completion of their mission or when conditions are judged unsafe. The divers must
be alert for trouble at all times and must monitor the condition of their dive partner
constantly.
7-8.1

Breathing Technique. A novice diver is likely to breathe deeper and more rapid

than normal, and thereby deplete their air supply faster than an experienced diver.
The diver must learn to breathe in an easy, slow rhythm at a steady pace. The rate
of work should be paced to the breathing cycle, rather than changing the breathing
to support the work rate. If a diver is breathing too hard, he should pause in the
work until breathing returns to normal. If normal breathing is not restored, the
affected diver signals the dive partner to abort the dive.
A diver may be tempted to skip-breath when they have a limited supply to conserve
air. Skip breathing occurs when a long unnatural pause is inserted between each
breath and shall not be practiced.

WARNING		

Skip-breathing may lead to hypercapnia, unconsciousness, and death.

Increased breathing resistance results from the design of the equipment and increased
air density. For normal diving, a marked increase of breathing resistance should
not occur until the primary air supply has been almost depleted. This increase in
breathing resistance is a signal to the diver to activate the reserve air supply and to
begin an ascent with their partner immediately. The diver shall monitor air supply
pressure and must terminate the dive whenever bottle pressure is reduced to 500 psi
for a single bottle or 250 psi for a set of double bottles.
7-8.2

Mask Clearing. Some water seepage into the face mask is a normal condition and

is often useful in defogging the lens. From time to time the quantity may build to
a point that it must be removed. On occasion, a mask may become dislodged and
flooded. To clear a flooded mask not equipped with a purge valve, the diver should
roll to the side or look upward, so that the water will collect at the side or bottom
of the mask. Using either hand, the diver applies a firm direct pressure on the
opposite side or top of the mask and exhales firmly and steadily through the nose.
The water will be forced out under the skirt of the mask. When the mask has a
purge valve, the diver tilts his head so that the accumulated water covers the valve,
then presses the mask against the face and exhales firmly and steadily through the
nose. The increased pressure in the mask will force the water through the valve.
Occasionally, more than one exhalation will be required (see Figure 7-13).
7-8.3

Regulator Clearing. The second stage regulator will flood if removed from the
mouth while submerged. This is not a serious problem since the regulator can be
cleared quickly by exhaling into the regulator or by depressing the purge button as
the mouthpiece is being replaced.

CHAPTER 7 — SCUBA Air Diving Operations

7-39

Head-Up Method

Side-Tilt Method
Figure 7-13. Clearing a Face Mask. To clear a flooded face mask, push gently on the
upper or side portion of the mask and exhale through the nose into the mask. As water is
forced out, tilt the head backward or sideway until the mask is clear.

7-8.4

7-8.5

Swimming Technique. In underwater swimming, all propulsion comes from the
action of the legs. The hands are used for maneuvering. The leg kick should be
through a large, easy arc with main thrust coming from the hips. The knees and
ankles should be relaxed. The rhythm of the kick should be maintained at a level
that will not unduly tire the legs or bring on muscle cramps.
Diver Communications. Some common methods of diver communications are:

through-water communication systems, hand signals, slate boards, and line-pull
signals. Communication between the surface and a diver can be best accomplished
with through-water voice communications. However, when through-water
communications are not available, hand signals or line-pull signals can be used.

7‑8.5.1

7-40

Through-Water Communication Systems. Presently, several types of through-

water communication systems are available for SCUBA diving operations. Acoustic
systems provide one-way, topside-to-diver communications. The multidirectional
audio signal is emitted through the water by a submerged transducer. Divers can
hear the audio signal without signal receiving equipment. Amplitude Modulated
(AM) and Single Sideband (SSB) systems provide diver-to-diver, diver-to-topside,
and topside-to-diver communications. Both the AM and SSB systems require
transmitting and receiving equipment worn by the divers. AM systems provide a
stronger signal and better intelligibility, but are restricted to line-of-sight use. SSB
systems provide superior performance in and around obstacles. Through-water
communication systems are listed on the ANU list.
U.S. Navy Diving Manual — Volume 2

Meaning/Signal

Comment

STOP
Clenched fist.

SOMETHING IS WRONG
Hand flat, fingers together, palm out, thumb
down then hand rocking back and forth on
axis of forearm.

This is the opposite of Okay. The
signal does not indicate an emer­
gency.

I AM OKAY or ARE YOU OKAY?
Thumb and forefinger making a circle with
three remaining fingers extended (if possible).

Divers wearing mittens may not
be able to extend three remaining
fingers distinctly. Short range use.

OKAY ON THE SURFACE (CLOSE)
Right hand raised overhead giving Okay
signal with fingers.

Given when diver is close to pickup
boat.

OKAY ON THE SURFACE (DISTANT)
Both hands touching overhead with both arms
bent at 45° angle.

Given when diver is at a distance
from the pickup boat.

DISTRESS or HELP or PICK ME UP
Hand waving overhead (diver may also thrash
hand in water).

Indicates immediate aid is required.

WHAT TIME? or WHAT DEPTH?
Diver points to either watch or depth gauge.

When indicating time, this signal
is commonly used for bottom time
remaining.

GO DOWN or GOING DOWN
Two fingers up, two fingers and thumb against
palm.

GO UP or GOING UP
Four fingers pointing up, thumb against palm.

I’M OUT OF AIR
Hand slashing or chopping at throat.

Indicates signaler is out of air.

I NEED TO BUDDY BREATHE
Fingers pointing to mouth or regulator.

Signaler’s regulator may be in or out
of mouth.

Figure 7-14. SCUBA Hand Signals (page 1 of 3).

CHAPTER 7 — SCUBA Air Diving Operations

7-41

Meaning/Signal

Comment

COME HERE
Hand to chest, repeated.

ME or WATCH ME
Finger to chest, repeated.

OVER, UNDER, or AROUND
Fingers together and arm moving in and over,
under, or around movement.

Diver signals intention to move over,
under, or around an object.

LEVEL OFF or HOW DEEP?
Fingers and thumb spread out and hand
moving back and forth in a level position.

GO THAT WAY
Fist clenched with thumb pointing up, down,
right, or left.

Indicates which direction to swim.

WHICH DIRECTION?
Fingers clenched, thumb and hand rotating
right and left.

EAR TROUBLE
Diver pointing to either ear.

Divers should ascend a few feet. If
problem continues, both divers must
surface.

I’M COLD
Both arms crossed over chest.

TAKE IT EASY OR SLOW DOWN
Hand extended, palm down, in short up-anddown motion.

YOU LEAD, I’LL FOLLOW
Index fingers extended, one hand forward of
the other.

Figure 7-14. SCUBA Hand Signals (page 2 of 3).

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7‑8.5.2

Hand and Line-Pull Signals. Navy divers use common hand signals to ensure

universal understanding. Figure 7-14 presents the U.S. Navy approved hand
signals. Under certain conditions, special signals applicable to a specific mission
may be devised and approved by the Diving Supervisor. If visibility is poor, the
dive partners may be forced to communicate with line-pull signals on a buddy
line. Line-pull signals are discussed in Table 8-2. Hand signals and line-pull
signals should be delivered in a forceful, exaggerated manner so that there is no
ambiguity and no doubt that a signal is being given. If a signal is given, it shall
be acknowledged immediately. Failure of a diver to respond to a signal is an
emergency.

NIGHT DIVING SIGNALS
(Buddy at Distance)
When buddy is near, use regular hand
signals in front of light.

Something is wrong.
I require assistance.
(Large, rapid up-and-down
motions with arm extended.)

I am Okay.
Are you Okay?
(Large, slow circles with
light.)

Figure 7-14. SCUBA Hand Signals (page 3 of 3).

7-8.6

Working with Tools. The near-neutral buoyancy of a SCUBA diver poses certain

problems when working with tools. A diver is at a disadvantage when applying
leverage with tools. When applying force to a wrench, for example, the diver
is pushed away and can apply very little torque. If both sides of the work are
accessible, two wrenches (one on the nut and one on the bolt) should be used. By
pulling on one wrench and pushing on the other, the counter-force permits most of
the effort to be transmitted to the work. When using any tool that requires leverage
or force (including pneumatic power tools), the diver should be braced with feet, a
free hand, or a shoulder.

CHAPTER 7 — SCUBA Air Diving Operations

7-43

NOTE

When using externally powered tools with SCUBA, the diver must have
voice communications with the Diving Supervisor.

Tools should be organized in advance. The diver should carry as few items as
possible. If many tools are required, a canvas tool bag should be used to lower them
to the diver as needed. Further guidelines for working underwater are provided
in the U.S. Navy Underwater Ship Husbandry Manual (NAVSEA S0600- AAPRO-010). Authorized power tools are listed in the NAVSEA/00C ANU list.
7-8.7

Adapting to Underwater Conditions. Through careful and thorough planning, the

divers can be properly prepared for the underwater conditions at the diving site
and be provided with appropriate auxiliary equipment, protective clothing, and
tools. However, the diver may have to employ the following techniques to offset
the effects of certain underwater conditions:

n Stay 2 or 3 feet above a muddy bottom; use a restricted kick and avoid
stirring up the mud. A diver should be positioned so that the current will
carry away any clouds of mud.
n Avoid coral or rocky bottoms, which may cause cuts and abrasions.
n Avoid abrupt changes of depth.
n Do not make excursions away from the dive site unless the excursions have
been included in the dive plan.
n Be aware of the peculiar properties of light underwater. Depth perception is
altered so that an object appearing to be 3 feet away is actually 4 feet away,
and objects appear larger than they actually are.
n Be aware of unusually strong currents, particularly rip currents near a
shoreline.
n If caught in a rip current, relax and ride along with it until it diminishes
enough to swim clear.
n If practical, swim against a current to approach a job site. The return swim
with the current will be easier and will offset some of the fatigue caused by
the job.
n Stay clear of lines or wires that are under stress.
7-8.8

Emergency Assistance/Procedures. The safest teams are well trained, conduct

detailed planning, and challenging emergency drills. Pre-operation emergency
drills validate planning assumptions and prepare the team to respond in the event of
an actual emergency. The most effective emergency drills are those that challenge
the entire team and exercise standby diver to the full depth of the operation.

A diver in trouble underwater should relax, avoid panic, carefully think through the
possible solutions to the situation, and communicate the problem to their buddy or

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U.S. Navy Diving Manual — Volume 2

the surface if possible. The Diving Supervisor must ensure calm, orderly execution
of preplanned topside emergency procedures, and should ensure that common
sense and good seamanship prevail to safely resolve an emergency.
7-8.8.1

Emergency Equipment. In addition to the emergency equipment required in

paragraph 6-5.1.3, a diver recall device and a lost diver kit shall be available
and ready for use on all SCUBA dive stations. The diver recall device may be
any acoustic generating device or method that is clearly audible to the divers for
recalling the divers or initiate an emergency recall. The preferred device is an
electronic acoustic unit capable of sending voice or variable underwater tones to
recall divers. Authorized electronic recall devices are listed on the ANU.
A lost diver kit shall include:
n A clump with sufficient weight to avoid being dragged by a searching diver.
n Line of sufficient length for the depth of water (polypropylene is recommended
due to its buoyant properties).
n A buoy of sufficient size to avoid being pulled underwater (minimum 11
inch buoy).
n A circling line of at least 25 feet attached to the clump (usually wound on
an”H” board).

The SCUBA Predive Checklist (Figure 7-11) lists emergency equipment for
SCUBA dive stations.
7-8.8.2

Emergency Procedures. Emergencies may occur despite detailed planning,
thorough training, and ORM. Effective execution of emergency procedures gives
the divers the best opportunity for an acceptable outcome should an emergency
occur. The following procedures provide diver and Dive Supervisor actions for
lost diver, trapped diver, a loss of air, and unconscious diver on the bottom.

7-8.8.2.1

Lost Diver. Losing contact with a SCUBA diver can be the first sign of a serious

problem. Each situation may be different based on whether the diver is tended or
untended, buddy paired or single diver. Time is of the essence and decisive action
must be taken at the first sign of a lost diver.
Diver actions if loss of contact with buddy while conducting paired diving:
n Perform a 360 degree visual search from current position.
n Note max depth and bottom time.
n Ascend to the surface at 30fpm while tapping in 4 tap intervals on tanks.
n Continue a 360 degree visual search for the lost diver or bubbles while on
ascent.

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7-45

n Upon reaching the surface, perform another 360 degree surface search for
the lost diver or bubble trail.
n Immediately inflate the life preserver or BC and signal the support craft with
hand signals, whistle, or flare. Once in contact with the Diving Supervisor,
report the lost diver, your maximum depth, bottom time, and air remaining.
n If a bubble column is located while on ascent follow the bubbles down to the
lost diver.
n If the diver is trapped follow procedure for trapped diver.
n If the diver is unconscious follow procedures for unconscious diver.
A lost diver is often disoriented and confused and may have left the operating area.
Nitrogen narcosis or other complications involving the breathing mixture, which
can result in confusion, dizziness, anxiety, or panic, are common in recovered lost
divers. The diver may harm the rescuers unknowingly. When the diver is located,
the rescuer should approach with caution to prevent being harmed and briefly
analyze the stricken diver’s condition.
Diving Supervisor actions for lost diver:
n Sound the recall and post lookouts. The best chances of spotting bubbles or a
surfaced diver are obtained from a higher vantage point. Continue to sound
the recall in frequent intervals.
n Lower the lost diver clump and buoy, hand over hand, at the last known
location of the lost diver.
n Initiate a search with standby diver in the area of the lost diver’s last known
location. A surfacing buddy diver may be used in lieu of the standby diver,
if he displays sufficient composure, has adequate air, and no-decompression
time remaining.
n Activate the emergency assistance plan to alert medical personnel and to
have emergency transportation standing by.
n Notify the command or pre-planned resource (other dive unit, fire department,
Coast Guard, etc.) to allow gathering of additional resources to aid in the
search.
n Continue searching and sounding the recall until the lost diver is found, all
resources are exhausted, or competent authority calls off the search.
7-8.8.2.2

Trapped/Fouled Diver. Fouling can be a serious emergency or a momentary

inconvenience depending on the diver’s reaction to the condition. Inexperienced
divers have a higher risk of becoming fouled, but no diver is immune. Divers must
maintain situational awareness to avoid becoming fouled or trapped when working
with lines, hoses, and cables, especially in reduced visibility.
Diver actions in case of entrapment/fouling:

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U.S. Navy Diving Manual — Volume 2

n The first and most important action that a trapped diver can take is to stop
and think. Panic and overexertion are the greatest dangers to the trapped
diver.
n The diver shall remain calm, analyze the situation, and carefully try to work
free.
n Help should be obtained through line pull signals or the buddy diver if the
situation cannot be resolved.
n The buddy diver should attach a tending line, if equipped, to the trapped
diver.
n Verify the trapped diver’s remaining air and depth. Determine what aid is
needed before surfacing for help.
n The diver may have no other recourse but to remove the SCUBA and shift to
an alternate air source (pony bottle), buddy breath, or make a free ascent.
Dive Supervisors actions:
n Dive supervisors should anticipate situations where a significant possibility
of fouling or entrapment exists and have appropriate resources ready to
deploy to resolve the situation (wire cutters, bolt cutters, hack saw, extra
SCUBA rigs/bottles, etc.).
n Upon learning of a trapped diver, ascertain if the diver has sufficient air and
what assistance is required.
n Launch standby diver to provide required assistance. For example, stand-by
diver may deliver a new apparatus and assist cutting the trapped diver free.
n A surfacing buddy diver may be used in lieu of stand-by for a rescue if the
buddy displays sufficient composure, has adequate air, and is in a favorable
decompression status.
7-8.8.2.3

Loss of Air. Careful planning (which includes calculating duration of air supply),
diver control of breathing/work rate, and situational awareness should preclude
a diver from running out of air. However, equipment malfunction, task fixation,
or being trapped may place the diver in a situation where the diver is without
air. Shifting to an alternate air source, buddy breathing, or a free ascent may be
necessary.

If a diver experiences a loss of air:
n Notify buddy.
n Check that the bottle valve is fully opened.
n Open reserve by turning the reserve lever to the down position.

CHAPTER 7 — SCUBA Air Diving Operations

7-47

n If primary regulator failed, switch to the secondary regulator or independent
air source if equipped.
n Abort dive. Buddy breathe or conduct a free ascent if necessary.
CAUTION:		

7-8.8.2.4

Do not ditch the apparatus unless absolutely necessary as more air
may be available as the diver ascends due to the decreasing ambient
pressure.
Unconscious Diver on the Bottom. An unconscious diver on the bottom in
SCUBA is a serious emergency. If a diver is found unconscious on the bottom
perform the following actions:

Rescue Diver actions:
n Approach with caution.
n Insert regulator in mouth if not already there and open airway. Do not purge
the regulator.
n Maintain the affected diver’s head in a chin up position to keep the airway
open.
n Ensure cylinder valve is on, check bottle pressure, and reserve position.
n Maintain positive physical control of the affected diver.
n Ditch the affected diver’s weights.
n Swim the affected diver to the surface, or signal to be hauled up if tended.
n If the rescue diver encounters difficulty in trying to swim the affected diver
to the surface, the rescuer should slowly inflate the affected diver’s buoyancy
compensator or actuate the CO2 of the life preserver. Do not lose direct
contact with the affected diver.
n Once on the surface, fully inflate the affected diver’s life preserver or BC,
gain the attention of the Dive Supervisor, and report the situation (diver
breathing/not breathing, diver found with regulator in/out of mouth).
Dive Supervisor direct the following actions when an unconscious diver is brought
to the surface:
n Inflate the affected diver’s life preserver/BC if not already inflated.
n Rescue diver to inflate his own life preserver/BC if not already inflated.
n Maintain an open airway of the victim.
n Give two rescue breaths if unconscious diver is not breathing.

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n Extract the divers in accordance with the pre-mishap plan.
n Begin basic life support measures and transport the diver to the recompression
chamber or medical facility
Surfacing divers may be suffering from POIS, hypoxia, hypercapnia, missed
decompression, or a combination of the four, and should be treated accordingly.
However, medical treatment for drowning as specified in 3-5.4, and 20-2.3 shall
take precedence when a surfacing diver has no pulse.
7-8.8.3

Actions following an Emergency. Divers that have experienced one or more of the
situations above must be treated appropriately. Dive Supervisors shall consider the
following for any diver that has experienced an emergency:

n The diver may be tired and emotionally exhausted.
n The diver may be suffering from or approaching hypothermia.
n The diver may have a physical injury.
n If a free ascent has been made, POIS may have developed.
n Significant decompression time may have been missed.
7-9

ASCENT PROCEDURES
7-9.1

Ascent Procedures. When it is time to return to the surface, either diver may

signal the end of the dive. When the signal has been acknowledged, the divers
shall ascend to the surface together at a rate not to exceed 30 feet per minute. For
a normal ascent, the divers will breathe steadily and naturally. Divers must never
hold their breath during ascent because of the danger of an air embolism. While
ascending, divers must keep an arm extended overhead to watch for obstructions
and should spiral slowly while rising to obtain a full 360 degree scan of the water
column.

NOTE

Buddy breathing and free ascent may be required as a result of one or
more emergency situation.

7-9.1.1

Buddy Breathing Procedure. The preferred method of buddy breathing is the use
of an octopus. As an alternative, the two divers may face each other and alternately
breathe from the same mouthpiece while ascending. Buddy breathing may be
used in an emergency and must be practiced so that each diver will be thoroughly
familiar with the procedure. The buddy breathing procedure without an octopus is:
1. The distressed diver should remain calm and signal “out of air” to the dive

partner and give the signal “I need to buddy breathe” by pointing to the second
stage regulator.

CHAPTER 7 — SCUBA Air Diving Operations

7-49

2. The partner and the distressed diver should hold on to each other by grasping

a strap or the free arm. The divers must be careful not to drift away from each
other.

3. The partner must make the first move by taking a breath and passing the

regulator to the distressed diver. The distressed diver must not grab for the dive
partner’s regulator. The dive partner guides it to the distressed diver’s mouth.
Both divers maintain direct hand contact on the regulator.

4. The regulator may have flooded during the transfer. In this case, clear the

regulator by exhaling into the mouthpiece or using the purge button if needed
before taking a breath.

5. The distressed diver should take two full breaths (exercising caution in the

event that all of the water has not been purged) and guide the regulator back to
the partner. The partner should then clear the regulator as necessary and take
two breaths.

6. The divers should repeat the breathing cycle and establish a smooth rhythm. No

attempt should be made to surface until the cycle is stabilized and the proper
signals have been exchanged.

Note:

Exhaling forcefully into the regulator is the preferred method to clear a
flooded regulator while buddy breathing. With two divers breathing off
one SCUBA the air supply will be depleted more rapidly. Using the purge
button to clear the regulator needlessly uses the limited supply of air.

7-9.1.2

Emergency Free-Ascent Procedures. If a diver has no other options but to make a

free ascent, the following guidelines are provided:

1. Drop any tools or objects being carried by hand.
2. Ditch the weight belt.
3. Actuate the life preserver or inflate the B.C. to surface immediately. Do not

ditch the SCUBA unless it is absolutely necessary.

4. If the SCUBA has become entangled and must be abandoned, actuate the quick-

release buckles to ditch the apparatus. SCUBA ditch and don refresher should
be included in work-up training dives under controlled conditions.

WARNING		

7-9.2

During a free ascent or buddy breathing, the affected diver, or the diver
without the mouthpiece must exhale continuously to prevent a POIS due
to expanding air in the lungs.
Ascent From Under a Vessel. When underwater ship husbandry tasks are required,

surface-supplied lightweight equipment is preferred. SCUBA diving is permitted
under floating hulls, however, a tending line to the SCUBA diver must be provided.
Ships are often moored against closed-face piers or heavy camels and care must
be exercised to ensure that the tending line permits a clear path for emergency
surfacing of the diver.

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Due to the unique nature of EOD operations involving neutralization of live limpet
mines, the use of tending lines is not practical or required. During limpet mine
search training, the use of tending lines is required.
SCUBA dive plans on deep-draft ships should restrict diving operations to one
quadrant of the hull at a time. This theoretical quartering of the ship’s hull will
minimize potential diver disorientation caused by multiple keel crossings or fore
and aft confusion.
Predive briefs must include careful instruction on life preserver use when working
under a hull to prevent panic blowup against the hull. Life preservers should not be
fully inflated until after the diver passes the turn of the bilge.
7-9.3

Decompression. Open-circuit SCUBA dives are normally planned as no-

decompression dives. Open-circuit SCUBA dives requiring decompression
may be made only when considered absolutely necessary and authorized by the
Commanding Officer or Officer in Charge (OIC). Under this unique situation, the
following provides guidance for SCUBA decompression diving.
The Diving Supervisor shall determine the required bottom time for each dive.
Based upon the time and depth of the dive, the required decompression profile from
the tables presented in Chapter 9 shall be computed. The breathing supply required
to support the total time in the water must then be calculated. If the air supply is not
sufficient, a backup SCUBA shall be made available to the divers. The backup unit
can be strapped to a stage or tied off on a descent line, which also has been marked
to indicate the various decompression stops to be used.
When the divers have completed the assigned task, or have reached the maximum
allowable bottom time prescribed in the dive plan, they must ascend to the stage
or the marked line and signal the surface to begin decompression. With the stage
being handled from the surface, the divers will be taken through the appropriate
stops while the timekeeper controls the progress. Before each move of the stage,
the tender will signal the divers to prepare for the lift and the divers will signal back
when prepared. When using a marked line, the tender will signal when each stop
has been completed, at which point the divers will swim up, signaling their arrival
at the next stop. Stop times will always be regulated by the Dive Supervisor.
In determining the levels for the decompression stops, the sea state on the surface
must be taken into consideration. If large swells are running, the stage or marker
line will be constantly rising and falling with the movements of the surface-support
craft. The depth of each decompression stop should be calculated so that the
divers’ chests will never be brought above the depths prescribed for the stops in the
decompression tables.
In the event of an accidental surfacing or an emergency, the Diving Supervisor will
have to determine if decompression should be resumed in the water or if the services
of a recompression chamber are required. The possibility of having to make such a
choice should be anticipated during the planning stages of the operation.

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7-51

7-9.4

Surfacing and Leaving the Water. When approaching the surface, divers must

not come up under the support craft or any other obstruction. They should
listen for the sound of propellers and delay surfacing until satisfied that there
is no obstruction. Once on the surface, the diver should scan immediately in all
directions and check for hazards (e.g., approaching surface vessels) and for the
location of the support craft and other divers. After the area is deemed clear of
hazards, immediately inflate the life preserver or BC and signal the support craft
with hand signals, whistle, or flare. Once in contact with the Diving Supervisor,
divers report their maximum depth attained, bottom time, air remaining, and any
problems encountered.
As the divers break the surface, the tender and other personnel in the support craft
must keep them in sight constantly and be alert for any signs of trouble. While one
diver is being taken aboard the support craft, attention must not be diverted from
the remaining divers in the water.
Usually, getting into the boat will be easier if the divers first remove the weight
belts, then the SCUBA, and hand them to the tenders. If the boat has a ladder, swim
fins should also be removed. Without a ladder, the swim fins will help to give the
diver an extra push to get aboard. A small boat may be boarded over the side or
over the stern depending on the type of craft and the surface conditions.

7-10

POSTDIVE PROCEDURES

The Diving Supervisor should debrief each returning diver while the experience of
the dive is still fresh. The Diving Supervisor should determine if the assigned tasks
were completed, if any problems were encountered, if any changes to the overall
dive plan are indicated and if the divers have any suggestions for the next team.
The diver shall remain within under the direct observation of the Dive Supervisor,
or a competent representative, for 10 minutes post dive and 30 minutes’ travel
time of the diving unit for at least 2 hours after surfacing. When satisfied with
their physical condition, the divers’ first responsibility after the dive is to check
their equipment for damage and get it properly cleaned and stowed. Each diver
is responsible for the immediate postdive maintenance and proper disposition of
the equipment used during the dive. The Planned Maintenance System provides
direction for postdive maintenance.

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CHAPTER 8

Surface Supplied Air
Diving Operations
8-1

INTRODUCTION
8-1.1

8-1.2

Purpose. Surface supplied air diving includes those forms of diving where air is
supplied from the surface to the diver by a flexible hose. Surface Supplied Diving
(SSD) is used primarily for operations to 190 fsw.
Scope. This chapter identifies the equipment, personnel, and operational limits

and procedures for conducting surface supplied diving.

8-1.3

References. References cited in this chapter:

n 29 CFR Part 1910 Subpart T. U.S. Government Occupational Safety and Health
Administration (OSHA) Diving Standards.
n Military Divers Personnel Qualification Standard. NAVEDTRA 43910 Series.
n Navy Diving Program. OPNAV 3150.27 (Series).
n Naval Military Personnel Manual. MILPERSMAN 1220.
n KM-37NS Surface Supported Diving System. T6560-AC-OMP-010
n MK 20 MOD 0/1 Operations and Maintenance Manual. NAVSEA SS600-AKMMO-010.
n MK 3 Lightweight Dive System Operating and Maintenance Manual. SS500HK-MMO-010.
n Fly Away Dive System (FADS) III Air System Operation and Maintenance
Manual. S9592-B1-MMO-010.
n U.S. Navy Diving and Manned Hyperbaric Systems Safety Certification
Manual. SS521-AA-MAN-010.
8-2

OPERATIONAL CONSIDERATIONS
8-2.1

Operational Limits. Operational limits are based on a practical consideration of

working time verses decompression time and oxygen tolerance limits. Depth
limits are listed in Figure 8-1. Maximum depth limits shall not be exceeded except
as authorized in OPNAVINST 3150.27 (series). Due to a significantly higher risk
of DCS and CNS oxygen toxicity, planned exceptional exposure dives shall not be
conducted except by specific authorization. Planned exceptional exposure dives or

CHAPTER 8 — Surface Supplied Air Diving Operations

8-1

dives where maximum depth limits are exceeded require the presence of a DMO
on the side.
NORMAL AND MAXIMUM LIMITS FOR SURFACE SUPPLIED AIR DIVING
Depth fsw
(meters)

Limit for Equipment

60 (18)

MK 20. Maximum working limit with surface supplied systems other than Divator DP

60 (18)

KM‑37 NS. Maximum limit without Emergency Gas Supply (EGS)

60 (18)

Divator DP configuration 2 (Egress manifold)

190 (58)

Divator DP Configuration 1 (Surface augmented) and 3 (SCUBA). Maximum depth
limit. No decompression.

190 (58)

KM-37 NS. Normal working limit. Deeper than 190fsw requires specific authorization in
accordance with OPNAVINST 3150.27 (series)..

285 (87)

KM-37 NS. Maximum depth limit

Notes:
1.

Officers-in-Charge exercising command authority to include exceptions to above limits must be
designated in writing.

2.

When diving in an enclosed space, EGS must be used by each diver. EGS shall be considered for all
surface supplied dives during the dive planning and ORM processes and utilized effectively to benefit
the safety of the diver.

3.

29 CFR Part 1910 and OSHA Directive CPL 02-00-151 provides additional OSHA restrictions for
civilian DOD Surface Supplied Air diving. DOD civilian divers are identified as all permanent DOD
employees who have been formally trained at an approved U.S. Navy diving school. Commercial divers
contracted by DOD who are not permanent government employees are subject to these provisions.
The following are some examples of OSHA restrictions for DOD divers:

4.

a.

The maximum depth for surface-supplied air diving is 190 fsw, except that surface-supplied air dives
with bottom times of less than 30 minutes may be conducted to a maximum depth of 220 fsw.

b.

A decompression chamber is required (available within 5 minutes from the dive location) for dives
deeper than 100 fsw, or any dive that requires planned decompression.

c.

A emergency gas supply (come-home bottle) is required for all planned decompression dives
regardless of depth.

d.

DOD Civilian divers shall remain at the location of the recompression chamber for 1 hour after surfacing
for all dives that require a recompression chamber to be available within 5 minutes of the dive location.

DOD civilian divers are exempt from regulation by OSHA when conducting uniquely military operations.
Commanding Officer shall issue a letter designating military centric diving operations.

Figure 8‑1. Normal and Maximum Limits for Surface Supplied Air Diving.

8-2.2

Personnel. The size of the diving team will vary depending upon the scope and

duration of the mission, and other factors. The minimum number of qualified
divers required on station for each particular type of diving equipment is provided
in Figure 8-2. Personnel levels may need to be increased as necessary to satisfy

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U.S. Navy Diving Manual — Volume 2

specific operational conditions and situations to maintain safe and effective
dive sides. For example an optimum dive side for a typical Underwater Ship’s
Husbandry (UWSH) tasks is 10-14 personnel.
The dive team may include the Diving Officer, Master Diver, Diving Medical
Officer, divers qualified in various techniques and equipment, recorder, and medical
personnel. Other members provide support in varying degrees in roles such as boat
crew, winch operators, special systems and equipment operators, and line handlers.
MINIMUM PERSONNEL FOR DIVATOR DP SURFACE AUGMENTED
AND SURFACE SUPPLIED AIR DIVING

Diving Supervisor

1 (a)

Comms and Logs

(a, b)

Console/DP Operator

1(b)

Diver

1

Standby Diver (b)

1 (c)

Diver Tender

1(d)

Standby Diver Tender
Total

1
6(e, f)

WARNING
These are the minimum qualified divers required. ORM may require increases
to these levels for safe diving operations.
NOTES:
(a) Diving Supervisor may perform Comms/Logs as required.
(b) Console operator may also serve as Comms/Logs.
(c) SCUBA shall not be used for the standby diver for surface-supplied diving with the exception of the
DP surface augmented diving apparatus.
(d) One tender per diver. The Dive Supervisor may elect to use a non-diver tender. The Dive
Supervisor shall ensure any non-diver tenders thoroughly instructed in the required duties.
(e) Six is the minimum number of qualified divers for surface supplied air diving and Divator DP
operations (configurations 1 and 2), seven or more is highly recommended based on mission
requirements and ORM.
(f) All divers must be CPR qualified.

		
8-2.2.1

Figure 8‑2. Minimum Qualified Divers for Surface Supplied Air Diving Stations.

Watchstation Diving Officer. The Watchstation Diving Officer provides overall

supervision of diving operations and ensures strict adherence to procedures and
precautions and is present on the side as the scope of the operation dictates. The
Watchstation Diving Officer provides backup to the Diving Supervisor and may be
called upon to assume the side to assist in an emergency.
CHAPTER 8 — Surface Supplied Air Diving Operations

8-3

The Watchstation Diving Officer shall be a formally trained and PQS qualified diver.
The Watchstation Diving Officer is responsible to the Commanding Officer for
the safe and successful conduct of a particular diving operation. The Watchstation
Diving Officer must be designated in writing by the Commanding Officer.
8-2.2.2

Master Diver Responsibilities. The Master Diver provides advice, technical

expertise, and oversight of the Diving Supervisor. The Master Diver advises the
chain of command on matters pertaining to diving and recommends divers to the
Commanding Officer for appointment as Diving Supervisors.
The Master Diver is a graduate of the Master Diver Evaluation Course (CIN
A-433-0019) and is the most qualified person to supervise diving operations and
recompression treatments. The Master Diver is responsible to the Commanding
Officer, via the Diving Officer, for the safe conduct of all phases of diving operations.

8-2.2.3

Dive Supervisor. The Diving Supervisor is in charge of an individual dive,

or series of dives, regardless of rank. Dive Supervisors are selected based on
leadership, maturity, supervisory ability, and technical expertise and may be any
formally trained U.S. military diver, PQS qualified, and designated in writing by
the Commanding Officer.
The Dive Supervisor shall execute dives in a safe and effective manner and
discontinue diving operations in the event of unsafe diving conditions. The Dive
Supervisor is responsible for knowing and complying with rules, limits, procedures,
and for understanding the extent of their authority as delegated by the Commanding
Officer. The Dive Supervisor shall be included in operational planning and shall
conduct and document an ORM assessment for each diving day. Diving operations
shall not be conducted without the presence of the Diving Supervisor.

8-2.2.4

Console/Rack Operator. The console operator is a critical member of the surface

supplied dive team and must be thoroughly trained and proficient on the systems
for which they are qualified.
The console operator is responsible for:
n Monitoring/charging gas supply racks.
n Maintaining required air pressure to the divers.
n Monitoring primary and secondary supply pressure.
n Monitoring divers depth.
n Executing emergency procedures.

The console operator is responsible for ensuring minimum manifold pressure(MMP)
is maintained at a pressure that is 10fsw ahead of the divers while on decent and
monitors MMP throughout the dive. The console operator obtains the stage
depth when divers reach the bottom and monitors the deepest depth throughout
the dive. When divers are ready to leave the bottom, the console operator purges
8-4

U.S. Navy Diving Manual — Volume 2

the pneumofathometer and obtains the final stage depth. The console operator
monitors depth while the divers are ascending, adjusts MMP, and reports depths to
the Diving Supervisor as directed.
On large dive systems the duties of rack operator may be assigned to a separate
operator.
8-2.2.5

Standby Diver. The standby diver is a fully qualified and experienced diver

assigned to provide emergency assistance. A standby diver is required for all diving
operations. The standby diver need not be equipped with the same equipment as
the primary diver, but shall have equivalent depth and operational capabilities.
SCUBA shall not be used for standby diver for surface-supplied dives with the
exception of the DP surface augmented diving apparatus.
The standby diver receives the same briefings and instructions as the working
diver, monitors the progress of the dive, and is fully prepared to respond if called
upon for assistance. The standby diver shall have equivalent depth and operational
capabilities as the primary divers and be seated with strain relief connected to the
harness. Under certain conditions, the Diving Supervisor may require that the
helmet be worn.
The SSD standby diver may be deployed as a working diver provided all of the
following conditions are met:
n No-decompression dive of 60fsw or less.
n Same job/location, e.g., working on port and starboard propellers on the vessel.
n Prior to deploying the standby diver, the work area shall be determined to be
free of hazards (i.e., suctions, discharges) by the first diver on the job site.
n UWSH or UCT work. Salvage not authorized.
The standby diver may deploy outside an enclosed or confined space to tend the
working divers.

NOTE

8-2.2.6

The standby diver shall remain on deck and be ready for deployment
during salvage operations and as indicated by ORM.
Divers. The dive team selected for an operation shall be trained and qualified for
the diving technique used, the positions manned, and the equipment involved
in accordance with NAVEDTRA 43910 Series, OPNAV 3150.27 (Series) and
MILPERSMAN 1220. Divers are responsible for:

n Reporting any conditions that may interfere with safe diving.
n Preparation, maintenance, and safe operation of diving and ancillary equipment
and systems.

CHAPTER 8 — Surface Supplied Air Diving Operations

8-5

n Maintaining proficiency on systems, equipment, and procedures in which they
are qualified
n Keeping the Diving Supervisor informed of conditions on the bottom, progress
of the task, and of any developing problems that may indicate a need for
changes to the plan.
n Obeying a signal from the surface and repeating all commands.
8-2.2.7

Diver Tender. The tenders are responsible for:

n Assisting the diver in donning/doffing the dive gear.
n Continuously tending the umbilical to eliminate excess slack or tension (certain
UWSH tasks may preclude this requirement, e.g., working in submarine ballast
tanks, shaft lamination, dry habitat welding, etc.).
n Exchanging line-pull signals with the diver and keeping the Dive Supervisor
informed of the line pull signals and amount of umbilical over the side.
n Remaining alert for any signs of an emergency.
n Knowing CPR and first aid.
n Rendering aid to a stricken diver on the surface as directed by the diving
supervisor (extraction, first aid/CPR, administering 100% oxygen,
evacuation...).
8-2.2.8

Log Keeper. The log keeper shall be a qualified diver. The log keeper is responsible

for:

n Having on hand the U.S. Navy Decompression
Table being used.
n Maintaining worksheets and the diving log for
the operation.
n Recording the depth of dive, bottom time, and
significant events of the dive.
n Recording the schedule selected by the Diving
Supervisor.
n Reporting to the Diving Supervisor the
required ascent time, first stop, and time
required at the decompression stop.
n Keeping all members of the team advised
of the decompression requirements of the
divers.
8-6

Figure 8-3. KM 37 SSDS.

U.S. Navy Diving Manual — Volume 2

The log keeper is often assigned the task of handling communications to and
from the divers. When handling communications, the log keeper shall relay all
communications to and from the divers as directed by the Dive Supervisor.
8-2.2.9

8-3

Other Support Personnel. Support personnel are vital members of the surface
supplied dive team. Support personnel may include small boat operators, winch
operators, crane operators, or special equipment operators. Support personnel,
such as winch operators or deck crew that interact with the operation directly, shall
be under the control of the Diving Supervisor.

KM-37 NS

The KM-37 NS is an open circuit, demand, diving helmet (Figure 8-3 and Figure
8-4).
8-3.1

Operation and Maintenance. To ensure safe and reliable service, all surface

supplied UBAs must be maintained and repaired in accordance with PMS and the
operation and maintenance manual.

The following is the Navy technical manual used with the surface supplied UBA
KM-37 NS:
n KM-37 NS, T6560-AC-OMP-010, Operation and Maintenance Manual.
8-3.2

Air Supply. Air for the KM 37 NS system is supplied from the surface by either an

air compressor or (more often) a bank of high pressure air. Any air source used for
surface supplied diving shall:

n Provide air for the duration of the dive at an average sustained flow of 1.4 acfm.
n Provide an emergency back-up supply.
n Meet purity standards listed in Chapter 4.
The diver’s air consumption using KM 37 varies between .75 and 1.5 acfm when
used in a demand mode and can be greater than 8 acfm when used in a free flow
mode (steady flow open).
8‑3.2.1

Pressure Requirements. Because the KM-37 NS helmet is a demand type UBA,

the regulators have an optimum pressure that ensures the lowest possible breathing
resistance and reduces the possibility of over breathing the regulator (demanding
more air than is available). To determine the optimal pressure to send to the divers,
the appropriate over bottom pressure for the depth of the divers from Table 8-1 is
added to the bottom pressure of the divers. This becomes the minimum pressure
allowable on the diver’s air supply manifold, Minimum Manifold Pressure (MMP).
MMP ensures air overcomes bottom pressure, and the pressure drop that occurs as
air flows through the dive hose and valves of the mask, and reaches the diver at a
high enough pressure to provide a sufficient flow rate.

CHAPTER 8 — Surface Supplied Air Diving Operations

8-7

Table 8‑1. KM-37 NS Overbottom Pressure Requirements.
Dive Depth

Pressure in psig
Minimum

Desired

Maximum

90*

135

165

0-60 fsw
61-130 fsw

135

135

165

131-190 fsw

165**

165

165

* Not approved for use with a double exhaust kit installed. Instead use a minimum of 135 psig.
** 135 psig is authorized for diver life support systems not capable of sustaining 165 psig over bottom
due to system design limitations.

8‑3.2.2

Air Available Requirements. Sufficient air in storage (compensated for minimum

flask pressure and MMP) must be available to support a given dive for both the
primary divers and standby diver. When planning dive missions, flow calculations
are based on 1.4 acfm for decent and bottom phases and 0.75 acfm for ascent and
decompression phases.

Sample Problem 1. Determine the number of dives a bank of high pressure flasks is

capable of supporting with two KM-37 NS divers and one standby diver at a depth
of 130 fsw for 30 minutes. There are 5 flasks in the bank; only 4 are on line. Each
flask has a floodable volume of 8 cubic feet and is charged to 3,000 psig.
There are 3 steps to calculate air required:
1. First calculate standard cubic feet (scf) of air available in the banks. The

formula for calculating the scf of air available is:
Scf available = Pf – (Pmf + MMP) / 14.7 x FV x N
Where:
Pf

= Flask pressure

Pmf = Minimum flask pressure = 200 psig
FV =

Floodable volume

N

Number of flasks

=

n Calculate minimum manifold pressure (MMP):
MMP (psig) = (D x 0.445) + 135 psig
= (130 x 0.445) + 135 psig
= 193 psig (Rounded up)
n Calculate scf available:

scf required =

3000 - (200 + 193)
x8x4
14.7

= 5675.10 = 5675 scf (Rounded down)

8-8

U.S. Navy Diving Manual — Volume 2

KM-37 NS General Characteristics

Advantages:
1.
2.
3.
4.
5.

Unlimited by air supply
Head protection
Good horizontal mobility
Voice and/or line pull signal capabilities
Fast deployment

Disadvantages:
1.

Limited mobility

Restrictions:
1.
2.

3.

Depth limits: 190 fsw
Emergency air supply (EGS) required
deeper than 60 fsw or diving inside a wreck
or enclosed space
Current - Above 1.5 knots requires extra
weights

Operational Considerations:

Principle of Operation:

1.
2.

Adequate air supply system required
Standby diver required

Surface-supplied, open-circuit system

Minimum Equipment:
1.
2.
3.
4.
5.
6.
7.

KM-37 NS Helmet
Harness
Weight belt (if required)
Dive knife
Swim fins or boots
Surface umbilical
EGS bottle deeper than 60 fsw

Principal Applications:
1.
2.
3.
4.

Search
Salvage
Inspection
Underwater Ships Husbandry and enclosed
space diving

KM-37 NS Helmet.

Figure 8-4. KM-37 NS General Characteristics.

CHAPTER 8 — Surface Supplied Air Diving Operations

8-9

2. The second step is to calculate total amount of air required to make the dive.

To do this, calculate the air required for the bottom time, the air required for
each decompression stop, and the air required for the ascent. The formula to
calculate air required is:
Scf required = ata x C x N x T
Where:
ata

= D + 33 / 33

C = Consumption rate in acfm
N = Number of divers
T = Time at depth in minutes
n Air required on decent and the bottom:
scf = ata x C x N x T
= ((130fsw+ 33)/33) x 1.4 x 3 x :30
= 622.36 = 623 scf (Round up)
n Air required at decompression stop:
The 130/:30 schedule has a single 34 minute stop at 20 fsw
Scf required = ata x C x N x T
= ((20fsw+33)/33)) x .75 x 3 x 34
= 122.86 = 123 scf (Round up)
n Scf required for ascent:
Scf required = average ata x C x N x T
Average depth = 130 fsw + 0 fsw/2 = 65 fsw
= (65fsw + 33)/33 x .75 x 3 x :05
= = 33.40 = 34 scf (Round up)
Where:
Average ata = based on the average depth from the bottom to the surface
C = Consumption rate in acfm
N = Number of divers
T = Time is the total ascent time rounded up to the nearest whole minute
n Add all air required for total air requirement:
623scf on bottom + 123 scf at stop + 34scf on ascent
= 780 scf total

8-10

U.S. Navy Diving Manual — Volume 2

3. The third step is to divide air required into air available:

Number of dives = air available / air required
= 5675 scf/ 780 scf
= 7.27 = 7 dives (Rounded down)
The actual number of dives available would be higher since planning calculations
include standby diver for all dives.
NOTE

8-3.2.3

Planned air usage estimates will vary from actual air usage. Dive
Supervisors must note initial bank pressures and monitor consumption
throughout the dive. If actual consumption exceeds planned consumption,
the Diving Supervisor may be required to curtail the dive in order to ensure
there is adequate air remaining in the primary air supply to complete
decompression.
Emergency Gas Supply Requirements. An EGS is mandatory at depths deeper

than 60 fsw and when diving inside an enclosed space. An EGS may be required
for dives shallower than 60 fsw based on hazards of the task(s), and shall be
strongly considered during pre-dive planning and the ORM process. The Diving
Supervisor may elect to use an EGS that can be man-carried or located outside the
enclosed space (at or about the same depth as the diver) and connected to the diver
with a 50 to150 foot whip. The EGS cylinder may be located on the surface, if
diving 60fsw or shallower, in this case adjust the first stage regulator to 150 psi.
The EGS system consists of an adequately charged ANU approved SCUBA
cylinder with either a K- or J- valve (with reserve turned down) and a first stage
regulator set at manufacturer’s recommended pressure, but not lower than 135
psig. A relief valve set at 180 ± 5 psig must be installed on the first stage regulator
to prevent rupture of the low pressure hose should the first stage regulator fail.
The emergency supply valve on the helmet side block provides an air supply path
parallel to the non-return valve and is connected to the EGS first stage regulator
with a flexible low pressure hose. A submersible pressure gauge is required on the
first stage regulator.
An adequately charged SCUBA cylinder is defined as the pressure that provides
sufficient air to bring the diver to his first decompression stop or the surface for
no- decompression dives. It is assumed that this will give topside personnel enough
time to perform required emergency procedures to restore umbilical air to the diver.
NOTE

An operational risk assessment may indicate EGS use during dives
shallower than 60 fsw.
Sample Problem 1. Determine the minimum EGS cylinder pressure required for a
KM-37 NS dive to 190 fsw for five minutes.

CHAPTER 8 — Surface Supplied Air Diving Operations

8-11

1. To calculate the EGS cylinder pressure, you must first determine the amount

of gas required to get the diver back to the stage and leave bottom plus the gas
required for ascent to the first decompression stop. The formula for calculating
gas required is:
Scf required = ata x C x T
Where:
Ata = (Depth + 33) / 33
C=

Consumption rate in acfm per diver from Table 8-2

T=

Time (minutes)

n Air required while on the bottom: For this example, if the time to get the
diver to the stage and leave bottom is 3 minutes, then:
scf = (190 + 33) / 33 x 1.4 x :03
= 28.38 scf = 29 scf (rounded up)
n Air required for ascent to reach the first stop: For this example, you need to
determine ascent time and average depth. Ascent time is 7 minutes (rounded up
from 6 minutes 20 seconds) from 190 fsw to the surface at 30 feet per minute.
Air required is calculated as follows:
scf = average ata x C x T
Average depth = 190/2 = 95 fsw
Scf = (95 fsw + 33) /33 x 0.75 x :07
Scf = 20.36 = 21 scf (rounded up)
Where:
Average ata is based on the average depth from the bottom to the first stop.
n Determine total air required.
Air required on the bottom

29 scf

Air required on ascent

+ 21scf

Total scf

= 50 scf

2. The next step is to convert the required scf to an equivalent cylinder pressure in

psig. In this example, we are using an 80 ft3 aluminum cylinder to support this
dive. Refer to Table 7-1 for cylinder data used in this calculation:
PSIG required (Pr) = (scf /FV) x 14.7 + Pm
Where:
FV

= Floodable Volume (scf) = 0.399 scf

14.7 = Atmospheric Pressure (psi)
Pm
8-12

= Minimum cylinder pressure (psi)
U.S. Navy Diving Manual — Volume 2

MK 20 General Characteristics
Advantages:
1.
2.
3.

Unlimited by air supply
Good horizontal mobility
Voice and/or line-pull signal capabilities

Disadvantages:
1.

Limited physical protection

Restrictions:
1.
2.
3.

Depth limits: 60 fsw
Current - Above 1.5 knots requires extra
weights
Enclosed space diving requires an
Emergency Gas Supply (EGS) with 50 to
150 foot whip and second-stage regulator.

Operational Considerations:
1.
2.

Adequate air supply system required
Standby diver required

Principle of Operation:
Surface-supplied, open-circuit lightweight
system

Minimum Equipment:
1.
2.
3.
4.
5.
6.

MK 20 MOD 0 mask
Harness
Weight belt (as required)
Dive knife
Swim fins or boots
Surface umbilical

Principal Application:
Underwater Ships Husbandry

Figure 8-5. MK 20 General Characteristics.

CHAPTER 8 — Surface Supplied Air Diving Operations

8-13

Pm = First stage regulator setting + bottom pressure at final stop: 135 psig + (0
fsw x 0.445 psi) = 135 psig
= (50 / .399) X 14.7 +135
= 1977.10 (round up to nearest 100 psi)
= 2000psi
8-4

MK 20

The MK 20 is a surface-supplied UBA consisting of a full face mask, diver
communications components, equipment harness, and an umbilical assembly
(Figure 8-5).
The MK 20 UBA is available in two versions. The MK 20 MOD 0 is a positive
pressure UBA that is best used where protection from water suspected of
contamination is desired. The MK 20 Mod 1 is a non-positive pressure UBA suited
for all other diving.
8-4.1

8-4.2

Operation and Maintenance. NAVSEA SS600-AK-MMO-010, Operation and
Maintenance Manual details specific procedures for the MK 20 UBA. To ensure
safe and reliable service, the MK 20 system must be maintained and repaired
in accordance with PMS procedures and the MK 20 operation and maintenance
manual.
Air Supply. Air for the MK 20 system is supplied from the surface by either an

air compressor or a bank of high-pressure flasks. The MK 20 requires a breathing
gas flow of 1.4 acfm and an overbottom pressure of 90 psig. Flow and pressure
requirement calculations are identical to those for the KM-37 NS (see paragraph
8-3.2.1). Diver’s air must meet purity standards listed in Chapter 4.
8‑4.2.1

Emergency Gas Supply Requirements for MK 20 Enclosed-Space Diving (ESD).

When working in enclosed or confined spaces an EGS assembly must be used. As
a minimum, the EGS assembly consists of:
n An adequately charged ANU approved SCUBA cylinder with either a K- or
J-valve.
n An ANU approved first and second stage SCUBA regulator with the first stage
set at manufacturer’s recommended pressure, but not lower than 135 psi.
n An extended EGS whip 50 to 150 feet in length.
n An approved submersible pressure gauge.
The second stage regulator of the EGS must be securely attached to the diver’s
harness before entering the work space so that the diver has immediate access
to it in an emergency. The EGS whip may be married to the diver’s umbilical
and the SCUBA cylinder may be left on the surface or secured at the opening of
the enclosed space being entered. If the diving scenario dictates leaving the EGS

8-14

U.S. Navy Diving Manual — Volume 2

topside, adjust the first stage regulator to
150 psig.
8‑4.2.2

Additional EGS Guidance. The diving

supervisor may use an ANU approved
cylinder with the DSI sideblock
assembly to attach the emergency gas
source (EGS) when conducting dives
other than in an enclosed space, where
ORM indicates EGS use is desirable, and
strongly recommended. See Appendix
2C for more information on enclosed
space diving.

8-5

PORTABLE SURFACE-SUPPLIED DIVING
SYSTEMS
8-5.1

Divator Dive Panel (DP). Divator DP is a

class-certified portable diving apparatus
Figure 8-6. MK 20 MOD 0 UBA.
for SCUBA and diving operations using
surface supplied air. The apparatus is
lightweight and highly portable, which
makes it ideal for rapid deployment to
remote locations from a variety of platforms in support of various missions to
depths up to 190fsw in water temperatures of 29 degrees Fahrenheit and warmer.
(see Chapter 11 for cold or ice covered diving).
Each Divator DP system includes a surface control box, composite flasks, high
pressure interconnecting hoses, high pressure umbilicals, diver worn regulators
with an integrated EGS system, and the MK 20 Mod 0 full face mask.
The DP apparatus utilizes a minimum of two independent ANU authorized
cylinders, one acting as the primary air supply and the other as a secondary. Each
dual composite cylinder pack holds 140 scf of compressed air at 4,350 psi. High
pressure air is reduced by the diver worn P+ regulator to supply the MK-20 full
face mask (FFM). The EGS includes diver worn high pressure composite cylinders
which holds 71 scf of compressed air at 4,350 psi, a MK II regulator to reduce HP
air from the diver worn cylinders (in the event of a loss of surface air), interface
hose, and a balanced weight system (Figure 8-7).
It may be desirable or advantageous to utilize topside approved air supply sources
other than the HP Dual Cylinder Packs when diving Configuration 1 or 2. Divers air
purity must meet U.S. Military Diver’s Breathing Air Standards in accordance with
paragraph 4-3. NAVSEA controlled air sources (i.e., Light Weight Dive System
(LWDS) Flask Rack Assemblies, Fly Away Dive System (FADS) III Air Supply
Rack Assemblies, or other certified air sources) may be utilized, but permission
from NAVSEA 00C3 must be obtained prior to use.

CHAPTER 8 — Surface Supplied Air Diving Operations

8-15

Set-up and operating procedures for the DP are found in the Operation and
Maintenance Technical Manual for Divator Self-Contained UBA/Divator Products
(DP) Surface Supply Apparatus, SS510-AC-TMM-010.
8-5.1.1

DP Configurations. Divator DP may be utilized in three configurations and two

modes. Divator DP supports one diver (DP1 mode) and may be modified by the
addition of a T-piece to support an additional diver (DP2 mode). Configurations
1 and 2 can be set up to support either DP1 or DP2 Mode. Divers shall be trained
on proper use of the Divator DP system prior to use. The three Divator DP
configurations are:
n Configuration 1. Divator DP Surface Supply – Configuration 1 is a surface
augmented mode with a diver worn EGS. Authorized for all U.S. Navy
DP trained divers to 190fsw. In DP1 mode the standby diver shall use an
independent DP1 mode surface supply apparatus with an EGS. In DP2 mode
the standby diver may be the second diver in DP2 mode for depths of 60 fsw or
less. For depths greater than 60 fsw, the standby diver shall use an indpendent
DP1 mode surface supply apparatus with EGS.
Configuration 1 shall be supervised by a qualified surface supplied diving supervisor.
Configuration 1 may be used for enclosed space salvage operations by Surface
Supplied Diving (SSD) DP trained divers. During salvage, a diver supported by
DP2 shall tend the primary diver from outside the space and standby diver shall be
supplied by a separate DP1. Divator DP shall be used during salvage only for short
duration operations or as a support rig (e.g., examining items of interest, quick
recovery, underwater photographer, shuttling underwater tools, etc).
n Configuration 2. Divator DP Surface Supply w/ manifold kit. Configuration
2 is a surface augmented mode divided into Configuration 2A, 2B, 2C, and
is intended for open water dives, UWSH enclosed space diving in submarine
ballast tanks and cofferdams, aviation underwater egress training, and other
authorized pool diving scenarios. Configuration 2 uses the DP manifold kit, and
a topside EGS as outlined in paragraph 8-4.2.1. Configuration 2 is authorized
for Surface Supplied Diving (SSD) DP trained divers to 60fsw or shallower.
Configuration 2A is for open water dive missions that have direct access to the
surface. An EGS is not required for 2A, but the Divator SCUBA used as an EGS or
a separate surface-supplied EGS, may be utilized. The standby diver shall require
an independent DP1 mode surface supply apparatus.
Configuration 2B is for enclosed space diving. The standby diver shall require an
independent DP1 mode surface supply apparatus with a separate surface-supplied
EGS.
Configuration 2C is for aviation underwater egress training and other pool diving
scenarios. The standby diver may be the second diver in DP2 mode, or utilize an
independent DP1 mode surface supply apparatus.

8-16

U.S. Navy Diving Manual — Volume 2

Divator DP Surface Augmented
Underwater Breathing
Apparatus
Principle Mode of Operation:
Surface augmented, open circuit system

Minimum Equipment:
Divator DP surface box with adequate
cylinders per dive plan
2. Divator MK-II regulator with octopus
regulator.
3. MK 20 Full Face Mask
4. HP umbilical with P+ regulator
5. Life Preserver (Configuration 3 only)
6. Weights (if required)
7. Dive knife
8. Swim fins
9. Submersible wrist watch
10. Depth Gauge or Navy Dive Computer for
each diver
1.

Principal Applications:
1.
2.
3.

Shallow water search
Inspection
Light repair and recovery

Advantages:
1.
2.
3.
4.
5.
6.

Lightweight
Rapid deployment
Portability
Minimum support requirements
Excellent horizontal and vertical mobility
Greater endurance, air supply not limited
to diver worn cylinders

Restrictions:
Work limits:
1. Depth Limits: 190 fsw (Configuration 1,
3); 60 fsw (Configuration 2).
2. Standby diver required.
3. Within no-decompression limits.
4. Current – 1 knot maximum.
5. Diving team – minimum 5 persons.

Open Water Operational Considerations:
1.
2.

Standby diver required.
Float may be added to keep the negative
umbilical off the bottom.

CAUTION
When two divers are diving from the same
surface unit (DP 2), if one diver experiences an
umbilical casualty (cut) the primary air supply
for both divers will be lost. Shift to EGS is
automatic. Divers shall abort the dive if surface
air is lost.

Disadvantages:
1.
2.

Limited physical protection
Influenced by current

3.

Negatively buoyant HP umbilical

Figure 8‑7. Divator DP General Characteristics.

CHAPTER 8 — Surface Supplied Air Diving Operations

8-17

Configuration 2 shall be supervised by a qualified surface supplied diving supervisor.
n Configuration 3. Divator SCUBA. Non-surface augmented. Operational
guidelines of SCUBA apply. (see Chapter 7). Authorized for all U.S. Navy DP
trained divers to 190fsw.
Configuration 3 shall be supervised, at a minimum, by a qualified SCUBA diving
supervisor.
Divator DP Pre-Dive Checklists are located on the secure SUPSALV website on
the 00C3 publications page. The applicable checklist must be completed prior to
diving.
8-5.2

MK 3 Lightweight Dive System (LWDS). The MK 3 LWDS is a portable, selfcontained, surface-supplied diver life-support system (DLSS) (Figure 8-8). The
MK III LWDS is certified in two configurations and may be deployed pierside
or from a variety of support platforms. Each LWDS includes a control console
assembly, volume tank assembly, and stackable compressed-air rack assemblies,
each consisting of three high-pressure composite flasks (0.935 cu ft floodable
volume each). Each flask holds 191 scf of compressed air at 3,000 psi.

Set-up and operating procedures for the LWDS are found in the Operating and
Maintenance Manual for Lightweight Dive System (LWDS) MK 3 MOD 0, SS500HK-MMO-010 and system parameters and limitations are found in the approved
systems pre-survey outline book (PSOB).

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U.S. Navy Diving Manual — Volume 2

Figure 8-8. MK 3 Lightweight Dive System.

8-5.3

Flyaway Dive System (FADS) III.

The FADS III is a portable, self-contained, surface-supplied diver life-support
system designed to support dive missions to 190 fsw (Figure 8-9). Compressed
air at 5,000 psi is contained in nine 3.15 cu ft floodable volume composite flasks
vertically mounted in an Air Supply Rack Assembly (ASRA). The ASRA will hold
9671 scf of compressed air at 5,000 psi. Compressed air is provided by a 5,000 psi
air compressor assembly which includes an air purification system. The FADS III
also includes a control console assembly and a volume tank assembly. Three banks
of two, three, and four flasks allow the ASRA to provide primary and secondary
air to the divers as well as air to support chamber operations. Set-up and operating
procedures for the FADS III are found in the Operating and Maintenance Technical
Manual for Fly Away Dive System (FADS) III Air System, S9592-B1-MMO-010.

CHAPTER 8 — Surface Supplied Air Diving Operations

8-19

Figure 8-9. Flyaway Dive System (FADS) III.

WARNING

Due to increased fire hazard risk, the use of oxygen in air diving systems
is restricted to those systems using ANU Purification Systems and
verified as meeting the requirements of Table 4-1.

CAUTION

Personnel  conducting  oxygen DLSS  maintenance  shall  be  qualified in
writing as an oxygen worker and DLSS maintenance Technician or O2 /
mixed-gas UBA Technician for the UBA they are conducting maintenance
on.

8-5.4

Oxygen Regulator Console Assembly (ORCA). The ORCA is designed to be used

with any certified DLSS to provide 100% oxygen to the diver’s umbilical during
in-water decompression (Figure 8-10). It requires a separate oxygen supply and
consists of a valve control system and pressure regulator. The valve control system
contains isolation, bleed, control valves, gauges, and a high-pressure oxygen
pressure regulator to simultaneously provide low-pressure oxygen to up to three
divers. The system piping is installed to allow a straight pass-through of diver’s
breathable gas air from any compatible diver air supply system when not using the
oxygen reducer (Figure 8-11).

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U.S. Navy Diving Manual — Volume 2

Figure 8-10. Oxygen Regulator Control Assembly (ORCA) II.

8-6

SURFACE-SUPPLIED DIVING ACCESSORY EQUIPMENT

The following accessory equipment is often useful in surface-supplied diving
operations:
n Lead Line. The lead line is a weighted line that is used to physically measure
depth. Other methods of measuring depth may be used such as handheld
depth sounders or the ships fathometer. If a ships fathometer is used it must be
understood that it measures depth under the keel.
n Descent Line. The descent line guides the diver to the bottom and is used
to pass tools and equipment. A 3-inch double-braid line is recommended, to
prevent twisting and to facilitate easy identification by the diver on the bottom.
The end of the line may be fastened to a fixed underwater object, or it may be
anchored with a weight heavy enough to withstand the current. In the event of
fouling, the decent line shall be able to be cut by the diver.

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Figure 8-11. Oxygen Regulator Control Assembly (ORCA) II Schematic.

WARNING		

If job conditions call for using
a steel cable or a chain as a
descent line, the Diving Officer
must approve such use.

n Diver’s Stage. Constructed to
carry one or more divers, the
stage is used to put divers into
the water and to bring them to
the surface, especially when
decompression stops must
be made. The stage platform
is made in an open grillwork
pattern to reduce resistance
from the water and may include
seats. A guide for the descent
line, several eyebolts for
attaching tools, and steadying
lines or weights is provided.
The frames of the stages may
be collapsible for easy storage.

8-22

Figure 8-12. Communicating with Line-Pull
Signals.

U.S. Navy Diving Manual — Volume 2

NOTE

WARNING		

Diver Handling Systems (DHS) must be designed, tested, and installed
in accordance with U.S. Navy Diving and Manned Hyperbaric Systems
Safety Certification Manual (SS521-AA-MAN-010) Appendix C.
When possible, shackle the lift line directly to the stage with a safety
shackle, or screw-pin shackle seized with wire. If a hook is used it shall
be moused or pinned to prevent loss of the stage and injury to divers.

n Stage Line. The stage line is used to raise and lower the stage and shall be
3-inch double braid, or 3/8-inch wire rope minimum.
n Diving Ladder. The diving ladder may be used to enter or exit the water. The
ladder is most often used as a secondary method of exit from the water. Ladders
used for diving should be of sturdy construction and affixed securely to the
vessel or pier, and in such a manner as to not pose a trip hazard to the diver.
n Weights. Cast iron or lead weights are used to weight the diver, the descent line,
and/or the stage. Weighted harness may be worn by the diver to add additional
weight which will aid the diver in strong currents.
8-7

DIVER COMMUNICATIONS

There are several means for communicating in surface supplied diving. Typically
voice communications are the primary method, but line pull signals are also used.
Line-pull signals are generally used as a backup. Diver-to-diver communications
are available through topside intercom, diver-to-diver hand signals, or slate boards.
8-7.1

Intercommunication Systems. The major components of the
intercommunication system include the diver’s earphones and microphone, the
communication cable to each diver, the surface control unit, and the tender’s
speaker and microphone. The system is equipped with an external power cord and
can accept 115VAC or 12VDC. The internal battery is used for backup power and
should not be used as the primary power source unless an external power source is
not available.

Diver

ANU approved diver communication systems are compatible with all surface
supplied UBAs and allow conference (round robin) communications between the
tender and up to three divers. Topside continuously monitors and controls diver
communications on the surface and may isolate one diver from another if required.
To enable clear effective communications divers and topside should use
standard diving terminology, speak slow, lower the pitch of their voice, and keep
communication short and to the point; especially in an emergency.
8-7.2

Line-Pull Signals. A line-pull signal consists of one or a series of sharp, distinct
pulls on the umbilical that are strong enough to be felt by the diver (Figure
8-12). All slack must be taken out of the umbilical before the signal is given.

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Table 8‑2. Line-Pull Signals.
From Tender to Diver

Searching Signals (Without Circling Line)

1 Pull

“Are you all right?” When diver is descending,
one pull means “Stop.”

7 Pulls

“Go on (or off) searching signals.”

2 Pulls

“Going Down.” During ascent, two pulls mean
“You have come up too far; go back down until
we stop you.”

1 Pull

“Stop and search where you are.”

3 Pulls

“Stand by to come up.”

2 Pulls

“Move directly away from the tender if given
slack; move toward the tender if strain is taken on
the life line.”

4 Pulls

“Come up.”

3 Pulls

“Face your umbilical, take a strain, move right.”

2-1 Pulls

“I understand” or “Talk to me.”

4 Pulls

“Face your umbilical, take a strain, move left.”

3-2 Pulls

“Ventilate.”

4-3 Pulls

“Circulate.”

1 Pull

“I am all right.” When descending, one pull
means “Stop” or “I am on the bottom.”

7 Pulls

“Go on (or off) searching signals.”

2 Pulls

“Lower” or “Give me slack.”

1 Pull

“Stop and search where you are.”

3 Pulls

“Take up my slack.”

2 Pulls

“Move away from the weight.”

4 Pulls

“Haul me up.”

3 Pulls

“Face the weight and go right.”

2-1 Pulls

“I understand” or “Talk to me.”

4 Pulls

“Face the weight and go left.”

3-2 Pulls

“More air.”

4-3 Pulls

“Less air.”

From Diver to Tender

Searching Signals (With Circling Line)

Special Signals From the Diver

Emergency Signals From the Diver

1-2-3 Pulls

“Send me a square mark.”

2-2-2 Pulls

“I am fouled and need the assistance of another
diver.”

5 Pulls

“Send me a line.”

3-3-3 Pulls

“I am fouled but can clear myself.”

2-1-2 Pulls

“Send me a slate.”

4-4-4 Pulls

“Haul me up immediately.”

ALL EMERGENCY SIGNALS SHALL BE ANSWERED AS GIVEN EXCEPT 4-4-4

The line-pull signal code (Table 8-2) has been established through many years of
experience. Standard signals are applicable to all diving operations; special signals
may be arranged between the divers and Diving Supervisor to meet particular
mission requirements. Most signals are acknowledged as soon as they are received.
This acknowledgment consists of replying with the same signal. If a signal is not
properly returned by the diver, the signal is sent again. A continued absence of
confirmation is assumed to mean one of three things: the line has become fouled,
there is too much slack in the line, or the diver is in trouble.
If communications are lost, the Diving Supervisor must be notified immediately
and steps taken to identify the problem. The situation is treated as an emergency
(see paragraph 8-10.9.3).
Two line-pull signals are not answered by repeating the line pull. They are from
diver to tender, “haul me up” and “haul me up immediately.” Acknowledgment
consists of initiation of the action. A third signal, “come up”, signaled from the

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U.S. Navy Diving Manual — Volume 2

tender to diver, is not acknowledged until the diver is ready to leave the bottom. If
for some reason the diver cannot respond to the order, the diver must communicate
the reason via the voice intercom system or through the line-pull signal meaning “I
understand,” followed (if necessary) by an appropriate emergency signal.
A special group of searching signals is used by the tender to direct a diver in moving
along the bottom. These signals are duplicates of standard line-pull signals, but
their use is indicated by an initial seven-pull signal to the diver that instructs the
diver to interpret succeeding signals as searching signals. When the tender wants to
revert to standard signals, another seven-pull signal is sent to the diver which means
searching signals are no longer in use. Only the tender uses searching signals; all
signals initiated by the diver are standard signals. To be properly oriented for using
searching signals, the diver must face the line (either the lifeline or the descent line,
if a circling line is being employed).
8-8

PREDIVE PROCEDURES

The predive activities for a surface-supplied diving operation involve many people
and include setting a moor, inspecting and assembling the equipment, preparing the
dive station, activating the air supply systems, and dressing the divers. The surface
supplied dive station setup check list (Figure 8-13) is provided as an aid and may
be locally modified to suit specific needs.
8-8.1

Setting a moor. Any vessel being used to support surface-supplied diving

operations on fixed objects such as the ocean bottom, a wreck, or an underwater
structure shall be secured by at least a two-point moor or use a Dynamic
Positioning vessel IMO Equipment Class 2 or 3. A three, or four-point moor, while
more difficult to set, (or use of a Dynamic Positioning vessel), may be preferred
depending on the size of area to be worked or the existence of known or expected,
dramatic shifts in winds or seas in the area of operations.
Exceptions to diving from a two-point moor or Dynamic Positioning vessel IMO
Equipment Class 2 or 3 may occur when moored alongside a pier or another vessel
that is properly anchored, or when a ship is performing diving during open ocean
transits and cannot moor due to depth. See Appendix 2D, Guidance for U.S. Navy
Diving on a Dynamic Positioning Vessel, for conducting diving operations from a
DP vessel.

8-8.2

Dive Station Preparation. The diving station is neatly organized with all diving

and support equipment placed in an assigned location. Deck space must not be
cluttered with gear; items that could be a trip hazard or become damaged are
placed out of the way (preferably off the deck). A standard layout pattern should
be established and followed.

8-8.3

Air Supply Preparation. The primary and secondary air supply systems are

checked to ensure that adequate air is available. Diver’s air compressors are
started and checked for proper operation. The pressure in the accumulator tanks is
checked. If HP air cylinders are being used, the manifold pressure is checked. If a
compressor is being used as a secondary air supply, it is started and kept running
throughout the dive.
CHAPTER 8 — Surface Supplied Air Diving Operations

8-25

8-8.4

Line Preparation. Depth soundings are taken and descent line, stage, stage lines,

and connections are checked, with decompression stops properly marked.

8-8.5

Verify Environmental Conditions. Verify actual, verses assumed, conditions.

Check weather reports, sea state, and expected changes in conditions for the diving
day. Measurements of water temperature at the surface and at the bottom may
reveal unknown thermoclines, and lowering the stage or a weighted line while
observing its behavior in the water may reveal stronger currents that expected.

8-8.6

Recompression Chamber Inspection and Preparation. The recompression

chamber is inspected and all necessary equipment is placed on hand at the chamber
IAW the recompression chamber pre-dive checklist (Figure 18-13). Verify chamber
exhaust valves are closed, adequate air supply for immediate pressurization of
the chamber is available, and the oxygen supply system is charged and ready for
operation in accordance with system operating procedures and Chapter 18.

8-8.7

Predive Inspection. When the Diving Supervisor is satisfied that all equipment is

on station and in good operating condition, the next step is to dress the divers.

8-8.8

Donning Gear. Dressing the divers is the responsibility of the tender.

8-8.9

Diving Supervisor Predive Checklist. The Diving Supervisor must always use

a predive checklist prior to putting divers in the water. This checklist must be
tailored by the unit to the specific equipment and systems being used. Refer to the
appropriate operations and maintenance manual for detailed checklists for specific
equipment.
8-9

WATER ENTRY AND DESCENT

Once the predive procedures have been completed, the divers are ready to enter
the water. There are several ways to enter the water; the divers may step in, climb
down a ladder, or ride a stage. The choice is usually determined by the nature
of the diving platform. Regardless of the method of entry, the divers should look
before entering the water.
8-9.1

Predescent Surface Check. In the water and prior to descending to operating

depth, the diver makes a final equipment check.

n The diver immediately checks for leaks in the suit or air connections.
n If two divers are being employed, both divers perform as many checks as
possible on their own rigs and then check their dive partner’s rig. The tender or
another diver can assist in detecting leaks by looking for any telltale bubbles.
n Conduct diver buoyancy check.
n A communications check is made and malfunctions or deficiencies not
previously noted are reported at this time.

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U.S. Navy Diving Manual — Volume 2

When satisfied that the divers are ready in all respects to begin the dive, they notify
the Diving Supervisor and the tenders move the divers to the descent line. When in
position for descent, the diver adjusts for negative buoyancy and signals readiness
to the Diving Supervisor.
8-9.2

Descent. Descent may be accomplished with the aid of a descent line or stage.

Topside personnel must ensure that air is being supplied to the diver in sufficient
quantity and at a pressure sufficient to offset the effect of the steadily increasing
water pressure.
While descending, the diver adjusts the dial-a-breath, so that breathing is easy and
comfortable. The diver continues to equalize the pressure in the ears as necessary
during descent and must be on guard for any pain in the ears or sinuses, or any other
warning signals of possible danger. If any such indications are noted, the descent is
halted. The difficulty may be resolved by ascending a few feet to regain a pressure
balance; after two ineffective attempts, the diver is returned to the surface and
evaluated for a barotrauma. If sinus pain is noted at any point in the decent the dive
shall be aborted.
Some specific guidelines for descent are as follows:
n With a descent line, the diver locks the legs around the line and holds on to the
line with one hand.
n In a current or tideway, the diver descends with back to the flow in order to be
held against the line and not be pulled away. If the current measures more than
1.5 knots, the diver wears additional weights or descends on a weighted stage,
so that descent is as nearly vertical as possible.
n The maximum allowable rate of descent, by any method, normally should not
exceed 75 feet per minute (fpm), although such factors as the diver’s ability
to clear the ears, currents and visibility, and the need to approach an unknown
bottom with caution may render the actual rate of descent considerably less.
n When a stage is used for descent, it is lowered with the aid of a winch or a
diver’s davit and guided to the site by a shackle around the descent line. The
diver keeps watch for the approaching bottom and determines if the stage has a
safe landing area. If the bottom is fouled, stopping the stage five to 10 feet off
the bottom may be needed.
n The diver signals arrival on the bottom and gives a stage report then a bottom
report. A stage report describes the condition of the stage (flat on the bottom,
on top of the the clump etc.) and the lift line catenary (sufficient slack for the
sea state, but not so much as to pose a hazard to the divers). A bottom report
may be a brief statement that confirms conditions are as briefed, or may include
a report of water temperature (cool, comfortable, etc., a subjective measure
based on the thermal protection worn), visibility, current, and bottom type.
Conditions that are different than expected shall be reported. If there is any

CHAPTER 8 — Surface Supplied Air Diving Operations

8-27

SURFACE-SUPPLIED DIVING STATION SETUP CHECKLIST
(Sheet 1 of 2)

CAUTION
This checklist is intended for use with the detailed Operating Procedures (OPs) from the appropriate
equipment O&M technical manual.

A. RECOMPRESSION CHAMBER.
__ 1. Recompression chamber prepared IAW OPs and Chamber Pre-Dive Checklist (Fig 21-13)?
__ 2. Chamber Innerlock and outerlock exhaust valves shut?
__ 3. Path to chamber un-obstructed?
__ 4. Off-site non-USN recompression chamber facility inspected and deemed safe for use?
__ 5. Off-site recompression chamber facility notified of commencement of diving operations?
__ 6. Transportation method to off-site recompression chamber facility?
__ 7. Permissions/waivers obtained IAW Figure 6-18 if applicable?
B. EMERGENCY EQUIPMENT.
__ 1. Emergency Assistance Checklist filled out and conspicuously posted.
__ 2. First aid kit on station w/bag valve mask?
__ 3. Portable oxygen kit on station? Psi. ______________.
__ 4. Automated External Defibrillator on station? Charged/Tested
__ 5. Stretcher / backboard available?
__ 6. Means to extract injured diver available?
C. EQUIPMENT PREPARATION.
__ 1. KM-37 NS/MK 20 MOD 0 prepared IAW NAVSEA technical manuals and PMS?
__ 2. Assemble primary and spare dive equipment, umbilicals, accessory equipment, and tools.
__ 3. Check all equipment for damage, wear and tear, dents, distortion, or other discrepancies.
D. GENERAL EQUIPMENT.
__ 1. All accessory equipment in good working order: tools, lights, special systems, spares, etc?
__ 2. Erect diving stage.
__ a. Stage ballast installed?
__ b. Decent line bail in good working order?
__ c. Stage line connection secure? - Screw pin shackle seized with wire, or safety shackle used? If a
hook is used: pinned or wire moused?
__ 3. Portable Divers Handling systems listed in system PSOB?
__ 4. Portable Divers Handling systems installed IAW system drawing?
__ 5. Portable Divers Handling system tested IAW U.S. Navy Diving and Manned Hyperbaric System
Safety Certification Manual (SS521­AA­MAN­010) and PMS?
__ 6. Decent line is 3 inch double braid or similar? Able to be cut if required?
__ 7. Decent line plumbed? Clump adequate for current?
__ 8. Decent line able to be cast off quickly in an emergency?
__ 9. Diving ladder attached securely? Does not pose a trip hazard to a diver coming up and over?

Figure 8‑13. Surface Supplied Diving Station Setup Checklist (Sheet 1 of 2).

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SURFACE-SUPPLIED DIVING STATION SETUP CHECKLIST
(Sheet 2 of 2)

E. DIVE SYSTEM PREPARATION.
__ 1. System certification current and will not expire during mission?
__ 2. No open re-entry control actions on the system?
__ 3. System aligned IAW approved system operating procedures?
__ 4. Compressors:
__ a. Compressor is ANU listed or within the scope of certification?
__ b. Air sample is within periodicity?
__ c. Compressor is prepared for use IAW posted operating procedures and PMS?
__ d. Sufficient fuel, lubricants, and coolant available?
__ e. All compressor controls are properly marked and any remote valving tagged with
“Divers Air Supply - Do Not Touch” signs?
__ f. Compressor secure in diving craft and not subject to operating angles exceeding 15 degrees?
__ g. Compressor exhaust vented away from work areas?
__ h. Compressor intake obtaining an uncontaminated suction?
__ i. Compressor operating log available?
__ 5. All air supply hoses have proper leads, do not pass near high‑heat areas, are free of kinks and
bends, and are not exposed on deck in such a way that they could be rolled over, damaged, or
severed by machinery or other means?
__ 6. All pressure supply hoses have safety lines and strain reliefs properly attached?
__ 7. Gas status board up to date?
F. ENVIRONMENTAL.
__ 1. Weather conditions/reports verified?
__ 2. Winds and sea state greater than expected? Expected to change?
__ 3. Stable mooring?
__ 4. Affect of changes in wind, sea state, and current on mooring evaluated?
__ 5. Water depth verified by handheld depth sounder or lead line?
__ 6. Water temperature on the bottom?
__ 7. Current assessed? Extra weights on divers, stage, and clump if required?
G. FINAL PREPARATIONS.
__ 1. Records, logs, tables, and charts on station?
__ 2. Diver’s benches reasonably close to the diving ladder or stage?
__ 3. Standby positioned near, or able to hear, comms?
__ 4. Appropriate flags / day shapes / lights, hoisted or lighted?
__ 5. CO, port authority, and others as required, notified of commencement of diving?
__ 6. Assemble all members of the diving team for dive brief.

Figure 8‑13. Surface Supplied Diving Station Setup Checklist (Sheet 2 of 2).

CHAPTER 8 — Surface Supplied Air Diving Operations

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doubt about the safety of the diver or the diver’s readiness to operate under the
changed conditions, the dive is aborted.
8-10

UNDERWATER PROCEDURES
8-10.1

Adapting to Underwater Conditions. Through careful and thorough planning, the

divers can be properly prepared for the underwater conditions at the diving site.
The diver will employ the following techniques to adapt to underwater conditions:
n Upon reaching the bottom and before leaving the area of the stage or descent
line, the diver checks equipment and makes certain that the air supply is
adequate.
n The diver becomes oriented to the bottom and the work site using such clues
as the lead of the umbilical, natural features on the bottom, and the direction
of current. However, bottom current may differ from the surface current. The
direction of current flow may change significantly during the period of the
dive. If the diver has any trouble in orientation, the tender can guide the diver
by using the line-pull searching signals.
The diver is now ready to move to the work site and begin the assignment.

8-10.2

Movement on the Bottom. Divers should follow these guidelines for movement

on the bottom:

n Before leaving the descent line or stage, ensure that the umbilical is not fouled.
n The Diving Supervisor must determine if it is advantageous to move the divers
out through the stage or have them back off the stage. Moving through the stage
captures the umbilical allowing the divers to easily find the stage at the end of
the dive but also hampers line pull signals and may affect the divers ability to
move freely on or around the job site.
n Loop one turn of the umbilical over an arm; this acts as a buffer against a
sudden surge or pull on the lines.
n Proceed slowly and cautiously to increase safety and to conserve energy.
n If obstructions are encountered, pass over the obstruction, not under or around.
If you pass around an obstruction, you must return by the same side to avoid
fouling lines.
n When using a Variable Volume Dry Suit, buoyancy adjustments to aid in
movement, avoid bouncing along the bottom; all diver movements are
controlled.
n If the current is strong, stoop or crawl to reduce body area exposed to the
current.

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n When moving on a rocky or coral bottom, make sure lines do not become fouled
on outcroppings, guarding against tripping and getting feet caught in crevices.
Watch for sharp projections that can cut hoses, diving dress, or unprotected
hands. The tender is particularly careful to take up any slack in the diver’s
umbilical to avoid fouling.
n Avoid unnecessary movements that stir up the bottom and impair visibility.
n A diver should thoroughly ventilate at subsequent intervals as the diver feels
necessary and as directed from the surface. On dives deeper than 100fsw, the
diver may not notice warning symptoms of hypercapnia because of nitrogen
narcosis. It is imperative that the Diving Supervisor monitors the divers
ventilation.
CAUTION

When diving with a Variable Volume Dry Suit, avoid overinflation and
be aware of the possibility of blowup when breaking loose from mud.
If stuck, it is better to call for aid from the standby diver than to risk
blowup.

n Mud and silt may not be solid enough to support your weight. Many hours may
be spent working under mud without unreasonable risk. Demand regulators
may not function well when covered by mud or heavy silt. If it is anticipated that
the diver may become covered by mud, as in a jetting or tunneling operations,
the diver should keep the helmet steady-flow valve slightly open. The primary
hazard with mud bottoms comes from the concealment of obstacles and
dangerous debris.
8-10.3

Searching on the Bottom. Bottom time is always at a premium. Electronic visual,
acoustic, or remotely operated equipment should be sought and used whenever
possible to increase search effectiveness. If appropriate electronic searching
equipment is not available, it may be necessary to use unaided divers to conduct
the search. A surface directed diver search of the bottom can be accomplished
using verbal commands or searching signals based on the location of the divers
bubbles. More often, a second diver is deployed to tend the searching diver using
the stage or the descent line as a point of reference.
1. Sweeps are made with the umbilical held taut at a distance determined by the

range of visibility. A starting point is established by a marker, a wrist worn
compass, or the tending diver. Currents may hamper topside’s ability to direct
a bottom search using bubbles as a reference but those same currents can also
be used a reference by the diver.

If it is necessary to search in currents, especially very strong currents, it may
be more effective to begin the search by moving directly into the current, then,
after reaching the appropriate distance from the stage or clump, the diver turns
left or right to effect a clock-wise or counter-clock wise search. The diver then
“rides” the current downstream while keeping the umbilical taut until half the
circle is searched. The diver will then be directly downstream of the tending
diver. The searching diver then moves directly back into the current and back

CHAPTER 8 — Surface Supplied Air Diving Operations

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out to the starting point and completes a sweep in the opposite direction to
sweep the other half of the circle.
After a full 360-degree sweep is made, the diver returns to the starting point
and moves out another increment and makes another 360 degree sweep in the
same manner as the first. As more umbilical is let out the current exerts a greater
total force on the exposed umbilical which makes moving more difficult. This
method minimizes the force exerted on the umbilical by the current when it is
exposed sideways to the current because it is far more effective for a diver to
move directly into, and with, the current than across it.
2. If the effective range of the search is reached and the object is not found, the

moor will have to be shifted. An accurate chart of the areas searched should be
kept to avoid unnecessary duplication in the search and to ensure gaps in the
search area are minimized.

3. Once the object of a search is located, it is recovered by the diver or marked.

The tending diver can bring a marker line, lift line, or a buoy line out to the
searching diver to attach to the object. Divers must ensure umbilicals and lines
do not become fouled by following the umbilical back to the stage or decent
line hand-over-hand.

8-10.4

Working Around Corners. When working around corners where the umbilical

is likely to become fouled or line-pull signals may be dissipated, a second
diver (tending diver) may be sent down to tend the lines of the first diver at the
obstruction and to pass along any line-pull signals. Line-pull signals are passed on
the diver’s umbilical to which they pertain.

8-10.5

Working Inside a Wreck. When working inside a wreck, the same procedure

used when working around corners is followed, where each level penetrated may
require a tending diver to relay line pull signals. Ultimately, the number of tending
divers deployed depends on the specific situation, a sound risk assessment of the
hazards, and the good judgment of the Diving Supervisor.
Obviously, an operation requiring penetration through multiple deck levels requires
detailed advanced planning in order to provide for the proper support of the number
of divers required. KM-37 NS is the first choice for working inside of a wreck.
However, use of MK 20 Mod 0 may be used if deemed safe. The diver enters a
wreck feet first and never uses force to gain entry through an opening. Additional
information for enclosed space diving can be found in Appendix 2C.
8-10.6

Working With or Near Lines or Moorings. When working with or near lines or

moorings, observe the following rules:
n Stay away from lines under strain.

n Avoid passing under lines or moorings if at all possible; avoid brushing against
lines or moorings that have become encrusted with barnacles.

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U.S. Navy Diving Manual — Volume 2

n If a line or mooring is to be shifted, the diver is brought to the surface and, if
not removed from the water, moved to a position well clear of any hazard.
n If a diver must work with several lines (messengers, float lines, lifting lines,
etc.) each should be distinct in character (size or material) or marking (color
codes, tags, wrapping).
n Never cut a line unless the line is positively identified.
n When preparing to lift heavy weights from the bottom, the lines selected must
be strong enough and the surface platform must be positioned directly over the
object to be raised. Prior to the lift, make sure the diver is clear of the lift area
or leaves the water.
8-10.7

Bottom Checks. Bottom checks are conducted after returning to the stage or

descent line and prior to ascent. The checks are basically the same for each rig.
1. Ensure all tools are ready for ascent.
2. Check that all umbilicals and lines are clear for ascent.

3. Assess and report your condition (level of fatigue, remaining strength, physical

aches or pains, etc.) and mental acuity.

8‑10.8

Working with Tools. Underwater work requires appropriate tools and materials,

such as cement, foam plastic, and patching compounds. Many of these are
standard hand tools (preferably corrosion-resistant) and materials; others are
specially designed for underwater work. Consult the appropriate operations and
maintenance manuals for the use techniques of specific underwater tools. Apply
the following guidelines when working with tools:
n Never use a tool that is not in good repair. If a cutting tool becomes dulled,
return it to the surface for sharpening.
n Do not overburden the worksite with unnecessary tools, but have all tools that
may be needed readily available.
n Attach lanyards to all tools and parts that may be dropped and lost. Tools may
be hand carried (less desired), secured to the diving stage, or lowered on the
descent line. Secure power to all tools prior to ascent or descent.
n Use a diving stage, if possible,to provide the diver leverage and when applying
force (as to a wrench), or when working with a power that transmits a force
back through the diver.
n Use a hogging line if a stage is impractical to keep the diver close to the task
and provide leverage.

8-10.9

Safety. The safest teams are technically competent, well trained, and conduct

detailed planning and challenging emergency drills. A diver in trouble underwater

CHAPTER 8 — Surface Supplied Air Diving Operations

8-33

should relax, avoid panic, communicate the problem to the surface, and carefully
think through the possible solutions to the situation. The Diving Supervisor shall
ensure a calm, orderly execution of emergency procedures and ensure common
sense and good seamanship prevail to safely resolve an emergency.
Knowledge and understanding of specific job hazards is imperative for safe
execution of specific job tasks. Chapter 6 discusses hazards and mitigations, and
work specific operations manuals (i.e. U/W Cutting and Welding Manual, Salvage
Manual) contain warnings and cautions that shall be followed. Specific emergency
procedures are covered for each equipment in its operations and maintenance
manual. Dive system operators shall be able to execute the emergency procedures
for the system in use without hesitation.
A diver is likely to encounter the situations below in the normal range of diving
activity which, if not promptly solved, can lead to full-scale emergencies.
8‑10.9.1

Fouled Umbilical. As soon as a diver discovers that the umbilical has become

fouled:

1. The diver must stop and examine the situation. Pulling or tugging without a

plan may only serve to complicate the problem and could lead to a severed
hose.

2. Notify the Diving Supervisor if possible (the fouling may prevent transmission

of line-pull signals).

3. Follow umbilical back to the point of fouling and clear the umbilical.
4. If the umbilical was fouled on a sharp obstruction, inspect umbilical for damage

and report to the Dive Supervisor.

5. Deploy the standby or buddy diver if the umbilical cannot be freed.
6. The standby diver, using the first diver’s umbilical (as a descent line), should

follow the affected diver’s umbilical and free it.

7. If it is impossible to free the umbilical, the standby diver should signal for a

replacement umbilical.

8‑10.9.2

Fouled Descent Lines. If the diver becomes fouled with the descent line and

cannot be easily cleared, it is necessary to haul the diver and the line to the surface,
or to cut the weight free of the line and attempt to pull it free from topside. If the
descent line is secured to an object or if the weight is too heavy, the diver may
have to cut the line before being hauled up. For this reason, a diver should not
descend on a line that cannot be cut.

8‑10.9.3

Loss of Communications. If audio communications are lost, the system may have

failed or the diver could be in trouble. If communications are lost:

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U.S. Navy Diving Manual — Volume 2

1. Use line-pull signals at once. Depth, current, bottom or work site conditions

may interfere.

2. Check for rising bubbles of air. A cessation or marked decrease of bubbles

could be a sign of trouble.

3. Listen for sounds from the diving helmet. If no sound is heard, the circuit may

be out of order. If the flow of bubbles seems normal, the diver may be all right.

4. If sounds are heard and the diver does not respond to signals, assume the diver

is in trouble.

5. Have divers already on the bottom investigate, or send down the standby diver

to do so.

WARNING		

8-10.9.4

If only one diver is in the water and no response is received from the diver.
The possibility of contaminated breathing supply should be considered
and a shift to secondary may be required.
Loss of Gas Supply. Usually, when a diver loses breathing gas it should be obvious

almost immediately. Some diving configurations may employ an emergency gas
supply (EGS). When breathing gas supply is interrupted the approved emergency
procedure for the system in use must be executed and the dive shall be aborted.
The diver is surfaced as soon as possible. Surfacing divers may be suffering from
hypoxia, hypercapnia, missed decompression, or a combination of the three, and
should be treated accordingly.

8-10.9.5

Falling. When working at mid-depth in the water column, the diver should keep

a hand on the stage or rigging to avoid falling. The diver avoids putting an arm
overhead in a dry suit; air leakage around the edges of the cuffs may change the
suit buoyancy and increase the possibility of a fall in the water column.

8‑10.9.6

Damage to Helmet and Diving Dress. If a leak occurs in the helmet, the diver’s

head is lowered and the air pressure slightly increased to prevent water leakage. A
leak in the diving suit only requires remaining in an upright position; water in the
suit does not endanger breathing.
8-10.10

Tending the Diver. Procedures for tending the diver follow.
1. Before the dive, the tender ensures the dive hat has been properly prepared for

diving IAW PMS and that outerwear, harnesses, weights, boots, and gloves are
all ready and in good repair. The tender ensures that everything needed to dress
and prepare the diver for the dive is available at the bench before the diver sits
down (i.e., electrical tape, lanyards, N.I.D. buckets, foxtails, etc.).

2. When the diver is ready, the tenders dress and assist the diver to the stage or

ladder or water’s edge, always keeping a hand on the umbilical.

3. As the diver approaches the water’s edge the tenders put sufficient umbilical

slack over the side to allow the water to “break the divers fall” but not so much
as to allow the diver to descend too deep. Tenders pay out the umbilical at a
steady rate to permit the diver to descend smoothly and are vigilant for a call to

CHAPTER 8 — Surface Supplied Air Diving Operations

8-35

“hold” by the diver. Tenders call out increments of umbilical over the side as
directed by the Dive Supervisor.
4. Throughout the dive the tender keeps slack out of the line while not holding

it too tautly. The umbilical shall never be allowed to run free or be belayed
around a cleat or set of bitts. Two or three feet of slack permits the diver
freedom of movement and prevents the diver from being pulled off the bottom
by surging of the support craft or the force of current acting on the line. The
tender occasionally checks the umbilical to ensure that movement by the diver
has not resulted in excessive slack. Excessive slack makes signaling difficult
and increases the possibility of fouling the umbilical.

5. The tender monitors the umbilical by feel and the descent line by sight for

any line-pull signals from the diver. If an intercom is not being used, or if the
diver is silent, the tender periodically verifies the diver’s condition by line-pull
signal. If the diver does not answer, the signal is repeated; if still not answered,
the Diving Supervisor is notified. If communications are lost, the situation is
treated as an emergency.

8-10.11

Monitoring the Diver’s Movements. The Diving Supervisor and designated
members of the dive team constantly monitor the diver’s progress and keeps track
of their relative position.
1. Follow the bubble trail, while considering current(s). If the diver is searching

the bottom, bubbles move in a regular pattern. If the diver is working in place,
bubbles do not shift position. If the diver has fallen, the bubbles may move
rapidly off in a straight line.

2. Monitor the pneumofathometer pressure gauge to keep track of operating

depth. If the diver remains at a constant depth or rises, the gauge provides a
direct reading, without the need to add air. If the diver descends, the hose must
be cleared and a new reading made.

3. Additional Personnel Actions. Monitor the gauges on the supply systems for

any powered equipment. For example, the ammeter on an electric welding unit
indicates a power drain when the arc is in use; the gas pressure gauges for a gas
torch registers the flow of fuel. A change in pressure and flow of the hydraulic
power unit indicates tool use.

8-11

ASCENT PROCEDURES

Follow these ascent procedures when it is time for the divers to return to the surface:
1. To prepare for a normal ascent, the diver clears the job site of tools and

equipment. These can be returned to the surface by special messenger lines sent
down the descent line. Or if the diver cannot find the descent line and needs a
special line, this can be bent onto the umbilical and pulled down by the diver.
The diver must be careful not to foul the line as it is laid down. The tender then

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U.S. Navy Diving Manual — Volume 2

pulls up the slack. This technique is useful in shallow water, but not practical
in deep dives.
2. If possible, the diving stage is positioned on the bottom. If some malfunction

such as fouling of the descent line prevents lowering the stage to the bottom,
the stage should be positioned below the first decompression stop if possible.
Readings from the pneumofathometer are the primary depth measurements.

3. If ascent is being made using the descent line or the stage has been positioned

below the first decompression stop, the tender signals the diver “Standby to
come up” when all tools and extra lines have been cleared away. The diver
acknowledges the signal. The diver, however, does not pull up. The tender lifts
the diver off the bottom when the diver signals “Ready to come up,” and the
tender signals “Coming up. Report when you leave the bottom.” The diver so
reports.

Figure 8-14. Surface Decompression.

4. If, during the ascent, while using a descent line, the diver becomes too buoyant

and rises too quickly, the diver checks the ascent by clamping his legs on the
descent line.

5. The rate of ascent is a critical factor in decompressing the diver. Ascent

must be carefully controlled at 30 feet per minute by the tender. The ascent
is monitored with the pneumofathometer. As the diver reaches the stage and
climbs aboard, topside is notified of arrival. The stage is then brought up to the
first decompression stop. Refer to Chapter 9 for decompression procedures.

6. While ascending and during the decompression stops, the diver must be

satisfied that no symptoms of physical problems have developed. If the diver
feels any pain, dizziness, or numbness, the diver immediately notifies topside.

CHAPTER 8 — Surface Supplied Air Diving Operations

8-37

During this often lengthy period of ascent, the diver also checks to ensure that
the umbilical is not fouled.
7. Upon arrival at the surface, topside personnel, timing the movement as dictated

by any surface wave action, coordinate bringing the stage and umbilical up and
over the side.

8. The tenders provide assistance if the diver exits the water via the ladder. The

diver may be tired, and a fall back into the water could result in serious injury.

If an emergency requires the diver to be hauled out of the water, any required
extraction aids should have been identified in the planning stage and the remedy
tested and ready prior to operations. Under no conditions is any of the diver’s gear
to be removed before the diver is firmly on deck.
8-12

SURFACE DECOMPRESSION
8-12.1

Surface Decompression Considerations. Surface decompression procedures

are discussed in paragraph 9-8.3. When transferring a diver from the water to the
chamber, the tenders are allowed no more than 3½ minutes to undress the diver.
Undressing a diver for surface decompression should be practiced until a smooth,
coordinated procedure is developed. The time factor is critical and delays cannot
be tolerated.
The route from the diver’s benches to the chamber must be kept clear from
obstructions and trip hazards. The chamber team must be alert to the dive
supervisor’s cue to man the chamber and be ready at their stations before the divers
arrive. An inside tender, or diving medical personnel, as required by the nature of
the dive or the condition of the diver, must be in the chamber with any necessary
supplies prior to arrival of the diver. (Figure 8-14)
Unassigned personnel must be ready to assist in getting the diver safely to the
chamber and back under pressure within the allotted time.

8-13

POSTDIVE PROCEDURES

Postdive procedures are planned in advance to ensure personnel are carefully
examined for any possible injury or adverse effects and equipment is inspected,
maintained, and stowed in good order.
8-13.1

Personnel and Reporting. Immediate postdive activities include any required
medical treatment for the diver and completing of mandatory reports.

n Medical treatment is administered for cuts or abrasions. The general condition
of the diver is monitored until problems are unlikely to develop. The Diving
Supervisor resets the stopwatch after the diver reaches the surface and remains
alert for irregularities in the diver’s actions or mental state. The diver shall
remain within under the direct observation of the Dive Supervisor, or a

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U.S. Navy Diving Manual — Volume 2

competent representative, for 10 minutes post dive and 30 minutes’ travel time
of the diving unit for at least 2 hours after surfacing.
n Mandatory records and reports are covered in Chapters 5 and 6. Certain
information is logged as soon as the diving operations are completed, while
other record keeping is scheduled when convenient. The Diving Supervisor
is responsible for the diving log, which is kept as a running account of the
dive. The diver is responsible for making appropriate entries in the personal
diving record. Other personnel, as assigned, are responsible for maintaining
equipment usage logs.
8-13.2

Equipment. A postdive checklist, tailored to the equipment used, is followed
to ensure equipment receives proper maintenance prior to storage. Postdive
maintenance procedures are contained in the equipment operation and maintenance
manual and the planned maintenance system package.

CHAPTER 8 — Surface Supplied Air Diving Operations

8-39

PAGE LEFT BLANK INTENTIONALLY

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U.S. Navy Diving Manual — Volume 2

CHAPTER 9

Air Decompression
9-1

INTRODUCTION
9-1.1

9-1.2

Purpose. This chapter discusses the decompression requirements for air diving
operations.
Scope. This chapter explains the theory and provides general guidance to

safely conduct air decompression dives. Air dives are completed utilizing NoDecompression, In-Water Decompression, In-Water Decompression on Air and
Oxygen, and Surface Decompression tables and procedures. This chapter also
explains charting air dives, exceptional exposure diving, altitude diving, and
emergency procedures.

9-2

THEORY OF DECOMPRESSION

As a diver descends, the partial pressure of nitrogen in his lungs rises above
the partial pressure of nitrogen dissolved in his tissues. This pressure difference
causes nitrogen to be transported from the lungs to the tissues via the bloodstream.
Transport to a given tissue will continue as long as the partial pressure of nitrogen
in the lungs is higher than the partial pressure of nitrogen in that tissue. The process
will stop when the tissue has absorbed enough nitrogen to raise its partial pressure
to a value equal to that in the lungs. Different tissues absorb nitrogen at different
rates. A tissue with a high blood flow, like the brain, will come into equilibrium
with the partial pressure of nitrogen in the lungs faster than a tissue with low blood
flow, like muscle or tendon. The total amount of nitrogen absorbed by a tissue
will be greater the deeper the dive and the longer the bottom time, until the tissue
becomes saturated.
As a diver ascends, the process is reversed. The partial pressure of nitrogen in the
tissues comes to exceed that in the lungs. During ascent, nitrogen is transported
back from the tissues to the lungs through circulation. The ascent rate must be
carefully controlled to allow time for this process to occur and not allow the tissue
nitrogen partial pressure to exceed the ambient pressure by too great an amount.
The more the tissue nitrogen partial pressure exceeds the ambient pressure during
ascent, the more likely nitrogen bubbles will form in tissues and blood, causing
decompression sickness.
To reduce the possibility of decompression sickness, special decompression
schedules have been developed for air diving. These schedules take into consideration
the amount of nitrogen absorbed by the body at various depths and times. Other
considerations are the extent to which the tissue nitrogen partial pressure can
exceed the ambient pressure without excessive bubble formation and the different
nitrogen elimination rates associated with the various body tissues. Because of its
operational simplicity, staged decompression is used for air decompression. Staged

CHAPTER 9 — Air Decompression

9-1

decompression requires decompression stops in the water at various depths for
specific periods of time.
Years of scientific study, calculations, animal and human experimentation, and
extensive field experience have all contributed to the air decompression tables.
While the tables contain the best information available, the tables tend to be less
accurate as dive depth and bottom time increase. To ensure maximum diver safety,
the tables must be strictly followed. Deviations from established decompression
procedures are not permitted except in an emergency and with the guidance and
recommendation of a Dive Medical Officer (DMO) with the Commanding Officer
or Officer-in-Charge’s approval.
9-3

AIR DECOMPRESSION DEFINITIONS

The following terms must be understood before using the air decompression tables.
9-3.1

9-3.2

Descent Time. Descent time is the total elapsed time from the time the diver leaves
the surface to the time he reaches the bottom. Descent time is rounded up to the
next whole minute for charting purposes.
Bottom Time. Bottom time is the total elapsed time from the time the diver leaves

the surface to the time he leaves the bottom. Bottom time is measured in minutes
and is rounded up to the next whole minute.

9-3.3

Total Decompression Time. The total decompression time is the total elapsed time

from the time the diver leaves the bottom to the time he arrives on the surface. This
time is also frequently called the total ascent time. The two terms are synonymous
and can be used interchangeably.

9-3.4

9-3.5

Total Time of Dive. The total time of dive is the total elapsed time from the time
the diver leaves the surface to the time he arrives back on the surface.
Deepest Depth. The deepest depth is the deepest depth recorded on the depth

gauge during a dive.

9-3.6

Maximum Depth. Maximum depth is the deepest depth obtained by the diver

after correction of the depth gauge reading for error. When conducting SCUBA
operations, the diver’s depth gauge is considered error free. The diver’s maximum
depth is the deepest depth gauge reading. When conducting surface-supplied
diving operations using a pneumofathometer to measure depth, maximum depth
is the deepest reading on the pneumofathometer gauge plus the pneumofathometer
correction factor (Table 9-1). Maximum depth is the depth used to enter the
decompression tables.

9-3.7

9-2

Stage Depth. Stage depth is the pneumofathometer reading taken when the divers
are on the stage just prior to leaving the bottom. Stage depth is used to compute the
distance and travel time to the first stop, or to the surface if no stops are required.

U.S. Navy Diving Manual — Volume 2

9-3.8

Decompression Table. A decompression table is a structured set of decompression

schedules, or limits, usually organized in order of increasing bottom times and
depths.
9-3.9

9-3.10

9-3.11

Decompression Schedule. A decompression schedule is a specific decompression
procedure for a given combination of depth and bottom time as listed in a
decompression table. It is normally indicated as feet/minutes.
Decompression Stop. A decompression stop is a specified depth where a diver
must remain for a specified length of time (stop time) during ascent.
No-Decompression (No “D”) Limit. The maximum time a diver can spend at a

given depth and still ascend directly to the surface at the prescribed travel rate
without taking decompression stops.

9-3.12

9-3.13

No-Decompression Dive. A dive that does not require a diver to take decompression
stops during ascent to the surface.
Decompression Dive. A dive that does require a diver to take decompression stops

during ascent to the surface.

9-3.14

9-3.15

Surface Interval. In the context of repetitive diving, the surface interval is the
time a diver spends on the surface between dives. It begins as soon as the diver
surfaces and ends as soon as he starts his next descent. In the context of surface
decompression, the surface interval is the total elapsed time from when the diver
leaves the 40 fsw water stop to the time he arrives at 50 fsw in the recompression
chamber.
Residual Nitrogen. Residual nitrogen is the excess nitrogen gas still dissolved in a

diver’s tissues after surfacing. This excess nitrogen is gradually eliminated during
the surface interval. If a second dive is performed before all the residual nitrogen
has been eliminated, the residual nitrogen must be considered in computing the
decompression requirements of the second dive.
9-3.16

Single Dive. A single dive is any dive conducted after all the residual nitrogen

from prior dives has been eliminated from the tissues.
9-3.17

Repetitive Dive. A repetitive dive is any dive conducted while the diver still has

some residual nitrogen in his tissues from a prior dive.

9-3.18

9-3.19

Repetitive Group Designator. The repetitive group designator is a letter used to
indicate the amount of residual nitrogen remaining in the diver’s body following a
previous dive.
Residual Nitrogen Time. Residual nitrogen time is the time that must be added to
the bottom time of a repetitive dive to compensate for the nitrogen still in solution
in a diver’s tissues from a previous dive. Residual nitrogen time is expressed in
minutes.

CHAPTER 9 — Air Decompression

9-3

9-3.20

Equivalent Single Dive. A repetitive dive is converted to its single dive equivalent

before entering the decompression tables to determine the decompression
requirement. The depth of the equivalent single dive is equal to the depth of the
repetitive dive. The bottom time of the equivalent single dive is equal to the sum
of the residual nitrogen time and the actual bottom time of the repetitive dive.
9-3.21

Equivalent Single Dive Time. The equivalent single dive time is the sum of the

residual nitrogen time and the bottom time of a repetitive dive. Equivalent single
dive time is used to select the decompression schedule for a repetitive dive. This
time is expressed in minutes.

9-3.22

9-3.23

Surface Decompression. Surface decompression is a technique where some of
the decompression stops in the water are skipped. These stops are made up by
compressing the diver back to depth in a recompression chamber on the surface.
Exceptional Exposure Dive. An exceptional exposure dive is one in which the risk

of decompression sickness, oxygen toxicity, and/or exposure to the elements is
substantially greater than on a normal working dive. Planned exceptional exposure
dives require CNO approval.

9-4

DIVE CHARTING AND RECORDING

Chapter 5 provides information for maintaining a Command Diving Log and a
personal dive log and for reporting individual dives to the Naval Safety Center.
In addition to these records, every Navy dive may be recorded on a diving chart
similar to Figure 9-1. The diving chart is a convenient means of collecting the dive
data, which in turn will be transcribed into the dive log. Abbreviations that may be
used in the diving chart and Command Diving Log are:
n LS - Left Surface
n RB - Reached Bottom
n LB - Left Bottom
n R - Reached a decompression stop
n L - Left a decompression stop
n RS - Reached Surface
n TBT - Total Bottom Time (computed from leaving the surface to leaving the
bottom)
n TDT - Total Decompression Time (computed from leaving the bottom to
reaching the surface)

9-4

U.S. Navy Diving Manual — Volume 2

Date:

Type of Dive:

Diver 1:

AIR

HeO2

Diver 2:

Rig:

O2%:

PSIG:

Diving Supervisor:
EVENT

Rig:

Standby:
PSIG:

O2%:

Rig:

Chartman:
STOP TIME

O2%:

Bottom Mix:

CLOCK TIME

LS or 20 fsw

PSIG:

EVENT

TIME/DEPTH

Descent Time (Water)

RB

Stage Depth (fsw)

LB

Maximum Depth (fsw)

st

Total Bottom Time

R 1 Stop
190 fsw

Table/Schedule

180 fsw

Time to 1st Stop ( Actual)

170 fsw

Time to 1st Stop (Planned)

160 fsw

Delay to 1st Stop

150 fsw

Travel/Shift/Vent Time

140 fsw

Ascent Time-Water/SurD (Actual)

130 fsw

Undress Time-SurD (Actual)

120 fsw

Descent Chamber-SurD (Actual)

110 fsw

Total SurD Surface Interval

100 fsw

Ascent Time–Chamber (Actual)

90 fsw

HOLDS ON DESCENT

80 fsw

DEPTH

PROBLEM

70 fsw
60 fsw
50 fsw
40 fsw

DELAYS ON ASCENT

30 fsw

DEPTH

PROBLEM

20 fsw
RS
RB CHAMBER
50 fsw chamber

DECOMPRESSION PROCEDURES USED

40 fsw chamber

AIR
o In-water Air decompression
o In-water Air/O2 decompression
o SurDO2

30 fsw chamber
RS CHAMBER
TDT

TTD

HeO2
o In-water HeO2/O2 decompression
o SurDO2
REPETITIVE GROUP:

Remarks:

Figure 9-1. Diving Chart.

CHAPTER 9 — Air Decompression

9-5

n TTD - Total Time of Dive (computed from leaving the surface to reaching the
surface)
Figure 9‑2 illustrates these abbreviations in conjunction with a dive profile.

Figure 9‑2. Graphic View of a Dive with Abbreviations.

9-5

THE AIR DECOMPRESSION TABLES

Six Tables are required to perform the full spectrum of air dives
n No-Decompression Limits and Repetitive Group Designation Table for NoDecompression Air Dives. This Table gives the no-decompression limits and
the repetitive group designators for dives that do not require decompression
stops.
n Air Decompression Table. This Table gives the decompression schedules and
repetitive group designators for dives that require decompression stops.
n Residual Nitrogen Timetable for Repetitive Air Dives. This Table allows the
diver to determine his Residual Nitrogen Time when performing a repetitive
dive.
n Sea Level Equivalent Depth Table. This Table allows the diver to correct the
sea level decompression tables for use at altitude.

9-6

U.S. Navy Diving Manual — Volume 2

n Repetitive Groups Associated with Initial Ascent to Altitude Table. This
Table allows the diver to adjust his decompression if he is not fully equilibrated
at altitude.
n Required Surface Interval Before Ascent to Altitude After Diving. This
Table tells the diver when it is safe to fly or ascend to higher altitude after a dive.
9-6

GENERAL RULES FOR THE USE OF AIR DECOMPRESSION TABLES
9-6.1

Selecting the Decompression Schedule. To select the proper decompression

schedule, record the bottom time and the maximum depth attained by the diver.
Enter the table at the exact or next greater depth and at the exact or next longer
bottom time. The new air tables are designed to provide safe decompression
even for divers who work hard on the bottom or are exceptionally cold during
decompression. It is not necessary to select the next deeper or next longer
decompression schedule under these conditions as in the past.
When using a pneumofathometer to measure depth, first correct the observed depth
reading by adding the pneumofathometer correction factor shown in Table 9-1.
Ensure the pneumofathometer is located at mid-chest level.

Table 9‑1. Pneumofathometer Correction Factors.
Pneumofathometer Depth

Correction Factor

0-100 fsw

+1 fsw

101-200 fsw

+2 fsw

201-300 fsw

+4 fsw

301-400 fsw

+7 fsw

Example: The diver’s pneumofathometer reads 145 fsw. In the depth range of
101–200 fsw, the pneumofathometer underestimates the diver’s actual depth by
2 fsw. To determine the diver’s actual depth, add 2 fsw to the pneumofathometer
reading. The diver’s actual depth is 147 fsw.
9-6.2

9-6.3

9-6.4

Descent Rate. The descent rate on an air dive is not critical, but in general it should
not exceed 75 fsw/min.
Ascent Rate. The ascent rate from the bottom to the first decompression stop,
between decompression stops, and from the last decompression stop to the surface
is 30 fsw/min (20 seconds per 10 fsw). Minor variations in the rate of ascent
between 20 and 40 fsw/min are acceptable. For surface decompression, the ascent
rate from the 40 fsw water stop to the surface is 40 fsw/min.
Decompression Stop Time. For in-water decompression on air, the time at the

first decompression stop begins when the diver arrives at the stop and ends when
he leaves the stop. For all subsequent stops, the stop time begins when the diver

CHAPTER 9 — Air Decompression

9-7

leaves the previous stop and ends when he leaves the stop. In other words, ascent
time between stops is included in the subsequent stop time. The same rules apply
to in-water decompression on air/oxygen with the exception of the first stop on
oxygen. The time at the first oxygen stop begins when all divers are confirmed on
oxygen and ends when the divers leave the stop.
9-6.5
9-6.6

9-7

Last Water Stop. The last water stop for all in-water decompressions is 20 fsw.
Eligibility for Surface Decompression. A diver is eligible for surface
decompression upon completion of the 40 fsw water stop. If a 40 fsw stop is not
required by the decompression schedule, the diver may ascend directly to the
surface without decompression stops and begin surface decompression.

NO-DECOMPRESSION LIMITS AND REPETITIVE GROUP DESIGNATION TABLE
FOR NO-DECOMPRESSION AIR DIVES

The No-Decompression Table (Table 9-7) gives the maximum time that can be spent
at a given depth without the need for decompression stops during the subsequent
ascent to the surface. This table is sometimes called the “no-stop” table. At depths
of 20 fsw and shallower, there is no limit on the amount of time that can be spent at
depth. Deeper than 20 fsw, the time that can be spent is limited. For example, at 60
fsw, any dive longer than 63 minutes will require decompression stops.
The No-Decompression Table also provides the repetitive group designators for
dives that fall within the no-decompression limits. Even though no decompression
stops are required during ascent, the diver still surfaces with some residual nitrogen
in his tissues. This residual nitrogen needs to be accounted for if a repetitive dive
is planned.
If a diver exceeds the limits given in the No-Decompression Table, then the
decompression stop requirement must be calculated using Table 9-9.
For each depth listed in the No-Decompression Table, the corresponding nodecompression limit is indicated in the second column. This limit is the maximum
bottom time that a diver may spend at that depth and still return to the surface
without taking decompression stops. To find the no-decompression limit, enter the
table at the depth equal to or next greater than the maximum depth of the dive.
Follow that row to the second column to obtain the no-decompression limit.
The columns to the right of the no-decompression limit column contain the
repetitive group designators for dives with bottom times equal to or shorter than
the no-decompression limit. A repetitive group designator must be assigned to a
diver subsequent to every dive, even a no-decompression dive.
To find the repetitive group designator following a no-decompression dive:
1. Enter the table at the depth equal to or next greater than the maximum depth of

the dive.

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U.S. Navy Diving Manual — Volume 2

2. Follow that row to the right to the bottom time equal to or next greater than the

actual bottom time of the dive.

3. Follow the column up to obtain the repetitive group designator.
Example: Divers conduct a brief inspection of a worksite located at a depth of 74

fsw. Bottom time is 10 min. What is the no-decompression limit for a dive to 74
fsw? What is the repetitive group designator following this 10-minute dive?
Enter the No-Decompression Table at the next greater depth, 80 fsw. Follow the
row horizontally to the second column. The no-decompression limit at 80 fsw is
39 min. The divers could spend up to 39 min at this depth and still ascend to the
surface without decompression stops. Continue reading horizontally to the right
to the bottom time that is next greater than the actual bottom time. This is 12 min.
Read vertically up the column to obtain the repetitive group designator for this 10min dive. The repetitive group designator is C. If the divers had spent the full 39
min allowed at 74 fsw, the repetitive group designator would have been J. This dive
is illustrated in Figure 9-3.

9-7.1

9-8

Optional Shallow Water No-Decompression Table. Appendix 2A contains an
expanded version of Table 9-7 and Table 9-8 covering the depth range of 30–50 fsw
in one-foot increments. In this depth range, a small change in the diver’s maximum
depth can make a substantial difference in the allowable no-decompression time.
For example, at 35 fsw the no-decompression limit is 232 minutes; at 40 fsw it is
only 163 minutes, more than an hour less. When the diver’s maximum depth is
accurately known at the beginning of the dive, for example in ballast tank dives, or
when continuous depth recording is available, for example with a decompression
computer, the expanded table can be used to maximize no-decompression time.
These optional tables are most suited to ship husbandry diving, but can be used in
other shallow air diving applications as well.

THE AIR DECOMPRESSION TABLE

The Air Decompression Table, Table 9-9, combines three modes of decompression
into one table. These modes are: (1) in-water decompression on air, (2) in-water
decompression on air and oxygen, and (3) surface decompression on oxygen.
9-8.1

In-Water Decompression on Air. This mode of decompression is used when the

entire decompression will be conducted on air. The top row labeled “Air” under
each depth/bottom time entry gives the decompression schedule for in-water air
decompression. Enter the table at the depth that is exactly equal to or next deeper
than the diver’s maximum depth. Select the schedule for the bottom time that is
exactly equal to or next longer than the diver’s actual bottom time. Read across the
row to obtain the required decompression stop times. The last decompression stop
is taken at 20 fsw. The total ascent time is given in the next column. The repetitive
group designator upon surfacing is given in the last column.

Example: A diver makes a surface-supplied air dive to 78 fsw for 47 minutes. What

is the required decompression?

CHAPTER 9 — Air Decompression

9-9

1313
Date: 4 Sept 07

Type of Dive:

Diver 1: ND1Hooper

AIR

HeO2

Diver 2: ND1 Patterson

Standby: ND2 Webb

Rig: KM 37 PSIG: 3000 O2%:

Rig: KM 37 PSIG: 3000 O2%:

Rig: KM 37 PSIG: 3000 O2%:

Diving Supervisor: NDC Degitz

Chartman: NDC Palmer

Bottom Mix:

EVENT

STOP TIME

CLOCK TIME

EVENT

TIME/DEPTH

LS or 20 fsw

1300

Descent Time (Water)

:01

RB

1301

Stage Depth (fsw)

73

LB

1310

Maximum Depth (fsw)

st

R 1 Stop

73+1=74

Total Bottom Time

190 fsw

Table/Schedule

180 fsw

Time to 1st Stop (Actual)
st

:10
80/12 No D
:02::30

170 fsw

Time to 1

160 fsw

Delay to 1st Stop

150 fsw

Travel/Shift/Vent Time

140 fsw

Ascent Time-Water/SurD (Actual)

130 fsw

Undress Time-SurD (Actual)

120 fsw

Descent Chamber-SurD (Actual)

110 fsw

Total SurD Surface Interval

100 fsw

Ascent Time–Chamber (Actual)

90 fsw

Stop (Planned)

:02::26
::04

HOLDS ON DESCENT

80 fsw

DEPTH

PROBLEM

70 fsw
60 fsw
50 fsw
40 fsw

DELAYS ON ASCENT

30 fsw

DEPTH

PROBLEM

20 fsw
RS

1313

RB CHAMBER
50 fsw chamber

DECOMPRESSION PROCEDURES USED

40 fsw chamber

AIR
o In-water Air decompression
o In-water Air/O2 decompression
o SurDO2

30 fsw chamber
RS CHAMBER
TDT

TTD

:02::30

:13

HeO2
o In-water HeO2/O2 decompression
o SurDO2
REPETITIVE GROUP: C

Remarks:

Figure 9‑3. Completed Air Diving Chart: No-Decompression Dive.

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U.S. Navy Diving Manual — Volume 2

Enter the Air Decompression Table at the next deeper depth, 80 fsw, and the
next longer bottom time, 50 min. Read across the row labeled “Air”. A 17 min
decompression stop at 20 fsw is required. The diver ascends from 78 to 20 fsw at
30 fsw/min, spends 17 min at 20 fsw, then ascends to the surface at 30 fsw/min.
The repetitive group designator for this dive is “M”. This dive is illustrated in
Figure 9-4.
If the bottom time of a dive is less than the first bottom time listed for its depth in the
Air Decompression Table, decompression stops are not required. The divers may
ascend directly to the surface at 30 fsw/min. Refer to the No-Decompression Table,
Table 9-7, to obtain the repetitive group designator for a no-decompression dive.
If the Air Decompression Table does not list a repetitive group designator for a
dive, no repetitive dives deeper than 20 fsw are permitted following this dive. The
diver must have an 18-hour surface interval before making another dive deeper
than 20 fsw.
9-8.2

In-Water Decompression on Air and Oxygen.

WARNING

Due to increased fire hazard risk, the use of oxygen in air diving systems
is restricted to those systems using ANU Purification Systems and
verified as meeting the requirements of Table 4-1.

CAUTION

Personnel conducting O2 DLSS maintenance shall be qualified, in writing,
as an oxygen worker and DLSS maintenance Technician or O2/mixed-gas
UBA Technician for the UBA they are conducting maintenance on.

This mode of decompression is used when the decompression will be conducted
partly on air and partly on 100% oxygen. The bottom row labeled “Air/O2” under
each depth/bottom time entry in Table 9-9 gives the decompression schedule for inwater air/oxygen decompression. Enter the table at the depth that is exactly equal to
or next deeper than the diver’s maximum depth. Select the schedule for the bottom
time that is exactly equal to or next longer than the diver’s actual bottom time.
Read across the Air/O2 row to obtain the required decompression stop times. The
diver follows the air schedule to 30 fsw (or 20 fsw if there is no 30 fsw stop), then
shifts from air to 100% oxygen. The oxygen stop times are shown in bold print.
Oxygen stop time begins when all divers are confirmed on oxygen. If more than 30
minutes must be spent on oxygen, a 5 min air break is required every 30 minutes.
Upon completion of the 20 fsw oxygen stop time, the diver surfaces at 30 fsw/
min while continuing to breathe 100% oxygen. The total ascent time, including air
breaks, is given in the next column. The repetitive group designator upon surfacing
is given in the last column and is the same as the repetitive group designator for an
air decompression dive.
All decompression stops deeper than 30 fsw are done on air. Decompression stops
on oxygen commence at 20 or 30 fsw in accordance with Table 9-9. Stops on
oxygen are in bold type in Table 9-9.

CHAPTER 9 — Air Decompression

9-11

1007
Date: 4 Sept 07

Type of Dive:

Diver 1: ND1 Hedrick

AIR

HeO2

Diver 2: HM2 Tyau

Standby: ND2 Parsons

Rig: KM 37 PSIG: 3000 O2%:

Rig: KM 37 PSIG: 3000 O2%:

Rig: KM 37 PSIG: 3000 O2%:

Diving Supervisor: NDCM Wiggins

Chartman: NDC Kriese

Bottom Mix:

EVENT

STOP TIME

CLOCK TIME

EVENT

TIME/DEPTH

LS or 20 fsw

0900

Descent Time (Water)

:02

RB

0902

Stage Depth (fsw)

77

LB

0947

Maximum Depth (fsw)

st

0949

Total Bottom Time

R 1 Stop

77+1=78
:47

190 fsw

Table/Schedule

80/50

180 fsw

Time to 1st Stop (Actual)

:01::58

st

170 fsw

Time to 1

Stop (Planned)

:01::54

st

160 fsw

Delay to 1 Stop

150 fsw

Travel/Shift/Vent Time

140 fsw

Ascent Time-Water/SurD (Actual)

130 fsw

Undress Time-SurD (Actual)

120 fsw

Descent Chamber-SurD (Actual)

110 fsw

Total SurD Surface Interval

100 fsw

Ascent Time–Chamber (Actual)

90 fsw

::04
::45

HOLDS ON DESCENT

80 fsw

DEPTH

PROBLEM

70 fsw
60 fsw
50 fsw
40 fsw

DELAYS ON ASCENT

30 fsw
20 fsw

DEPTH
:17

PROBLEM

1006

RS

1007

RB CHAMBER
50 fsw chamber

DECOMPRESSION PROCEDURES USED

40 fsw chamber

AIR
 In-water Air decompression
o In-water Air/O2 decompression
o SurDO2

30 fsw chamber
RS CHAMBER
TDT
:20

TTD
1:07

HeO2
o In-water HeO2/O2 decompression
o SurDO2
REPETITIVE GROUP: M

Remarks:

Figure 9‑4. Completed Air Diving Chart: In-water Decompression on Air.

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U.S. Navy Diving Manual — Volume 2

Current USN surface-supplied air diving systems (FADS III, LWDS, DSM, etc.)
require the use of an Oxygen Regulator Console Assembly (ORCA) to deliver
oxygen to the diver in the water. The Fly-Away Mixed Gas Diving System (FMGS),
which can be used to conduct air dives as well as mixed gas dives, is capable of
providing oxygen to the diver without the addition of an ORCA.
9-8.2.1

Procedures for Shifting to 100% Oxygen at 30 or 20 fsw. Upon arrival at the first

oxygen stop, ventilate each diver with oxygen following these steps:

1. Align the ORCA or FMGS to supply 100% oxygen to the diver.
2. Ventilate each diver for 20 seconds. Divers may be vented simultaneously or

sequentially.

3. Verify that the oxygen monitoring device on the ORCA or FMGS, if one is

present, shows 100% oxygen being delivered to the diver.

The Air Diving Chart has a space to enter the “Travel/Shift/Vent” time. For dives
in which the first stop is at 40 fsw or deeper, the travel/shift/vent time includes the
20 second ascent from 40 to 30 fsw as well as the time required to shift the console
to oxygen, vent the divers, and confirm that the divers are on oxygen. For dives
in which the first stop is an oxygen stop at 30 or 20 fsw, the travel/shift/vent time
only includes the time required to shift the console, vent the divers, and confirm
that they are on oxygen. The travel time to the stop is not included. The travel/shift/
vent time is recorded as minutes and seconds. The travel/shift/vent time should be
under 3 minutes.
9-8.2.2

Air Breaks at 30 and 20 fsw. At the 30 fsw and 20 fsw water stops, the diver

breathes oxygen for 30 min periods separated by 5 min air breaks. The air breaks do
not count toward required decompression time. When an air break is required, shift
the ORCA or FMGS to air for 5 minutes then back to 100% oxygen. Ventilation
of the divers is not required. For purposes of timing air breaks, begin clocking
oxygen time when all divers are confirmed on oxygen. If the total oxygen stop time
is 35 minutes or less, an air break is not required at 30 minutes. If the final oxygen
period is 35 minutes or less, a final air break at the 30-min mark is not required.
In either case, surface the diver on 100% oxygen upon completion of the oxygen
time.
Example: A diver makes a surface-supplied air dive to 145 fsw for 39 min. What is

the required decompression on air and oxygen?

1. Enter the Air Decompression Table at the next deeper depth, 150 fsw, and the

next longer bottom time, 40 min.

2. Read across the row labeled “Air/O2.” A 2-min decompression stop on air at

50 fsw is required.

3. The diver ascends from 145 to 50 fsw at 30 fsw/min, spends 2 min on air at

50 fsw, and then ascends to 40 fsw at 30 fsw/min.

CHAPTER 9 — Air Decompression

9-13

1141
Date: 5 Sept 07

Type of Dive:

AIR

HeO2

Diver 1: ND1 Poulan

Diver 2: HM2 Montgomery

Standby: NDC Miller

Rig: KM-37 NS PSIG: 2900 O2%:

Rig: KM-37 NS PSIG: 2900 O2%:

Rig: KM-37 NS PSIG: 2900 O2%:

Diving Supervisor: NDCM
Westling

Chartman: ND1 Slappy

Bottom Mix:

EVENT

STOP TIME

CLOCK TIME

EVENT

TIME/DEPTH

LS or 20 fsw

1000

Descent Time (Water)

:02

RB

1002

Stage Depth (fsw)

143

LB

1039

Maximum Depth (fsw)

st

1043

Total Bottom Time

R 1 Stop

143+2=145
:39

190 fsw

Table/Schedule

150/40

180 fsw

Time to 1st Stop (Actual)

:03::10

st

170 fsw

Time to 1

Stop (Planned)

:03::06

160 fsw

st

Delay to 1 Stop

::04

150 fsw

Travel/Shift/Vent Time

:02

140 fsw

Ascent Time-Water/SurD (Actual)

::40

130 fsw

Undress Time-SurD (Actual)

120 fsw

Descent Chamber-SurD (Actual)

110 fsw

Total SurD Surface Interval

100 fsw

Ascent Time–Chamber (Actual)

90 fsw

HOLDS ON DESCENT

80 fsw

DEPTH

PROBLEM

70 fsw
60 fsw
50 fsw

:02 (Air)

1045

40 fsw

:06 (Air)

1051

30 fsw

:02+:07 (O2)

1100

20 fsw

:23+:05+:12(O2)

1140

RS

DELAYS ON ASCENT
DEPTH

PROBLEM

1141

RB CHAMBER
50 fsw chamber

DECOMPRESSION PROCEDURES USED

40 fsw chamber

AIR
o In-water Air decompression
 In-water Air/O2 decompression
o SurDO2

30 fsw chamber
RS CHAMBER
TDT
1:02

TTD
1:41

HeO2
o In-water HeO2/O2 decompression
o SurDO2
REPETITIVE GROUP: Z

Remarks:

Figure 9‑5. Completed Air Diving Chart: In-water Decompression on Air and Oxygen.

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U.S. Navy Diving Manual — Volume 2

4. Upon arrival at 40 fsw, the diver spends 6 min on air, and then ascends to 30

fsw at 30 fsw/min.

5. Upon arrival at 30 fsw, the diver shifts to 100% oxygen. The diver spends a

total of 7 min at 30 fsw after the shift to oxygen.

6. The diver ascends on oxygen to 20 fsw and spends a total of 35 minutes on

oxygen at 20 fsw. The 20 second ascent time from 30 to 20 fsw is included in
the 35-min stop time. A five minute air break is required 23 minutes into the
20 fsw stop. The diver takes the air break then completes the remaining 12
minutes of oxygen required at 20 fsw.

7. Upon completion of the 20 fsw stop time, the diver ascends to the surface on

100% oxygen at 30 fsw/min. The total ascent time, including the air break is 59
minutes 40 seconds, not counting the time required to shift the divers to oxygen
at 30 fsw. The repetitive group designator for this dive is “Z”.

This dive is illustrated in Figure 9-5.
9-8.3

Surface Decompression on Oxygen (SurDO2). Surface decompression is a

technique for fulfilling all or a portion of a diver’s decompression obligation in
a recompression chamber instead of in the water. Decompression in the water
column is time consuming, uncomfortable, and inhibits the ability of the support
vessel to get underway. Advantages of surface decompression include:
n Reduces the time a diver must spend in the water.
n Enhanced diver’s safety.
n Shorter exposure time in the water keeps divers from chilling to a dangerous
level when diving in cold water.
n Divers can be maintained at a constant pressure inside the recompression
chamber, unaffected by the surface conditions of the sea.
n Speeds up operations. Once divers have been recovered into the recompression
chamber, a second dive team can begin descent, provided the recompression
chamber and the surface-supplied diving system have separate air supplies.
Delays from in-water decompression may present other problems for the support
vessel: weather, threatened enemy action, or operating schedule constraints. Inwater decompression delays medical treatment, when needed, and increases the
possibility of severe chilling and accident. For these reasons, decompression is
often accomplished in a recompression chamber on the support ship.
To decompress the diver using the Surface Decompression on Oxygen mode, follow
the in-water air decompression schedule (top row) through the end of the 40 fsw
water stop, then initiate surface decompression following the rules given below. If
there is no 40 fsw water stop in the air schedule, surface the diver without taking
any stops. In either case, start timing the surface interval when the diver leaves 40

CHAPTER 9 — Air Decompression

9-15

fsw. The required time on oxygen in the recompression chamber is shown in the
next to last column of the Table. Oxygen time is divided into periods. Each period
is 30 minutes long; each half-period is 15 minutes long. The first 15 minutes is
always spent at 50 fsw in the chamber; the remainder of the oxygen time is taken at
40 fsw. If the schedule requires only one half of an oxygen period, the diver spends
15 minutes breathing oxygen at 50 fsw in the chamber, then surfaces at 30 fsw/min.
The repetitive group designator for a surface decompression dive is shown in the
last column of the Table and is the same as the repetitive group designator for an
air decompression dive.
9-8.3.1

Surface Decompression on Oxygen Procedure
1. Complete any required decompression stops on air 40 fsw and deeper.
2. Upon completion of the 40 fsw stop, bring the diver to the surface at 40 fsw/

min. If a 40 fsw water stop is not required, bring the diver from the bottom to
40 fsw at 30 fsw/min and then from 40 fsw to the surface at 40 fsw/min. Once
the diver is on the surface, tenders have approximately 3 and a half minutes to
remove the breathing apparatus and diving dress and assist the diver into the
recompression chamber.

3. Place the diver and a tender in the recompression chamber. The job of the

tender is to monitor the diver closely for signs of decompression sickness and
CNS oxygen toxicity during the subsequent recompression. When two divers
undergo surface decompression simultaneously, the dive supervisor may elect
not to use an inside tender. In this case, both divers will carefully monitor each
other in addition to being closely observed by topside personnel.

4. Compress the diver on air to 50 fsw at a maximum compression rate of 100

fsw/min. The surface interval is the elapsed time from the time the diver leaves
the 40 fsw water stop to the time the diver arrives at 50 fsw in the chamber. A
normal surface interval should not exceed 5 minutes.

WARNING

The interval from leaving 40 fsw in the water to arriving at 50 fsw in the
chamber cannot exceed 5 minutes without incurring a penalty. (See
paragraph 9-12.6.)
5. Upon arrival at 50 fsw, place the diver on 100 percent oxygen by mask. Instruct

the diver to strap the mask on tightly to ensure a good oxygen seal.

6. In the chamber, have the diver breathe oxygen for the number of 30-minute

periods and 15-min half periods indicated in the next to last column of the Air
Decompression Table. The first period consists of 15 minutes on oxygen at 50
fsw followed by 15 minutes on oxygen at 40 fsw. Periods 2–4 are spent at 40
fsw. If more than 4 periods are required, the remaining periods are spent at 30
fsw. Ascent from 50 fsw to 40 fsw and from 40 fsw to 30 fsw is at 30 fsw/min.
Ascent time from 50 to 40 fsw is included in the first oxygen period. Ascent
from 40 to 30 fsw, if required, should take place during an air break.

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U.S. Navy Diving Manual — Volume 2

7. Interrupt oxygen breathing with a 5-min air break after every 30 minutes on

oxygen. This air time is considered dead time. Oxygen time begins when the
diver is confirmed to be on oxygen at 50 fsw.

8. When the last oxygen breathing period has been completed, return the diver to

breathing chamber air.

9. Ascend to the surface at 30 fsw/min.
Example: A surface-supplied diver makes an air dive to a maximum depth of
118 fsw for 65 minutes. The intent is to decompress the diver using the surface
decompression on oxygen mode. What is the proper decompression?
1. Enter the Air Decompression Table at the next deeper depth, 120 fsw, and the

next longer bottom time, 70 min.

2. Read across the row labeled “Air.” A 13-min decompression stop on air at

40 fsw is required. Continue reading across the row to the column labeled
“Chamber O2 Periods.” Two and one half chamber oxygen periods are required.

3. The diver ascends from 118 to 40 fsw at 30 fsw/min, spends 13 minutes on

air at 40 fsw, and then ascends to the surface at 40 fsw/min. Surfacing takes
1 minute.

4. Upon surfacing the diver is undressed as quickly as possible, placed in the

recompression chamber, and recompressed on air to 50 fsw. The total time
from leaving 40 fsw in the water to arriving at 50 fsw in the chamber normally
should not exceed 5 minutes.

5. Upon arrival at 50 fsw, the diver goes on 100% oxygen by mask and breathes

oxygen for 15 minutes. Time on oxygen begins when the diver goes on the
oxygen mask.

6. After 15 minutes on oxygen at 50 fsw, the diver ascends to 40 fsw at 30 fsw/

min while continuing to breathe oxygen from the mask. Ascent to 40 fsw takes
20 seconds. The diver continues to breathe oxygen at 40 fsw for an additional
14 min and 40 seconds. This ends the first 30-min oxygen period and the diver
takes a 5-min air break.

7. Upon completion of the air break, the diver resumes oxygen breathing by mask

for another 30-minute period. This ends the second 30-min oxygen period and
the diver takes a second 5-min air break.

8. Upon completion of the second air break, the diver resumes oxygen breathing

for 15 minutes, the remaining one-half period of oxygen required.

9. Upon completion of this last half period of oxygen, the diver goes off the

oxygen mask and breathes chamber air. The diver is brought to the surface at
30 fsw/min while breathing air.

10. No repetitive group designator is shown for this dive. The diver must wait 18

hours before making another dive.

This dive is illustrated in Figure 9-6.

CHAPTER 9 — Air Decompression

9-17

1253
Date: 5 Sept 07

Type of Dive:

AIR

Diver 1: ND1 Chaisson

HeO2

Diver 2: ND2 Hutcheson

Standby: ND1 Collins

Rig: KM-37 NS PSIG: 2900 O2%:

Rig: KM-37 NS PSIG: 2900 O2%:

Rig: KM-37 NS PSIG: 2900 O2%:

Diving Supervisor: NDCM Orns

Chartman: ND1 Saurez

Bottom Mix:

EVENT

STOP TIME

CLOCK TIME

EVENT

TIME/DEPTH

LS or 20 fsw

1000

Descent Time (Water)

:02

RB

1002

Stage Depth (fsw)

116

LB

1105

Maximum Depth (fsw)

st

1108

R 1 Stop

116+2=118

Total Bottom Time

:65

190 fsw

Table/Schedule

120/70

180 fsw

Time to 1st Stop (Actual)

:02::32

170 fsw

Time to 1

st

Stop (Planned)

:02::32

st

160 fsw

Delay to 1 Stop

150 fsw

Travel/Shift/Vent Time

140 fsw

AscentTime-Water/SurD (Actual)

130 fsw

Undress Time-SurD (Actual)

:01
:03::20

120 fsw

Descent Chamber-SurD (Actual)

::40

110 fsw

Total SurD Surface Interval

:05

100 fsw

Ascent Time–Chamber (Actual)

90 fsw

:01::20

HOLDS ON DESCENT

80 fsw

DEPTH

PROBLEM

70 fsw
60 fsw
50 fsw
40 fsw

:13 (Air)

1121

30 fsw

DELAYS ON ASCENT
DEPTH

PROBLEM

20 fsw
RS

1122

RB CHAMBER

1126

50 fsw chamber

:15

1141

40 fsw chamber :15+:5+:30+:5+:15

1251

DECOMPRESSION PROCEDURES USED
AIR
o In-water Air decompression
o In-water Air/O2 decompression
 SurDO2

30 fsw chamber
RS CHAMBER
TDT
1:48

1253
TTD
2:53

HeO2
o In-water HeO2/O2 decompression
o SurDO2
REPETITIVE GROUP: No Repet, must wait 18 hours.

Remarks:

Figure 9‑6. Completed Air Diving Chart: Surface Decompression on Oxygen.

9-18

U.S. Navy Diving Manual — Volume 2

9-8.3.2

Surface Decompression from 30 and 20 fsw

The diving supervisor can initiate surface decompression at any point during
in-water decompression at 30 or 20 fsw, if desired. Surface decompression may
become desirable if sea conditions are deteriorating, the diver feels ill, or some
other contingency arises. Surface decompression may be initiated regardless of
whether the divers are decompressing on air or oxygen. The diving supervisor may
elect to prescribe the full number of chamber oxygen periods listed in the surface
decompression schedule or elect to reduce that number of periods to take credit for
the time already spent on air or oxygen in the water.
1. If surface decompression is elected before the divers have been shifted to oxy-

gen, take the full number of chamber oxygen periods prescribed by the table.

2. If surface decompression is elected after divers have switched to oxygen,

compute the number of chamber oxygen periods required by multiplying the
remaining oxygen time at the stops by 1.1, dividing the total by 30 minutes,
then rounding the result up to the next highest half period. One half period (15
minutes at 50 fsw) is the minimum requirement.
Example: The supervisor elects to surface decompress when the diver has a

remaining oxygen time of 5 minutes at 30 fsw and 33 minutes at 20 fsw. The
total remaining oxygen time is 38 minutes. The number of 30-min SurDO2
periods required is (1.1 × 38) / 30 = 1.39. This number is rounded up to 1.5.

3. If surface decompression is elected while the divers are decompressing on air,

first convert the remaining air time at the stops to the equivalent remaining
oxygen time at the stops, then convert this remaining oxygen time to the
number of chamber oxygen periods required as shown above.
n For a diver at 30 fsw: First compute the air/oxygen trading ratio at 30
fsw by dividing the 30 fsw air stop time listed in the table by the 30-fsw
oxygen time. Next divide the remaining air time at 30 fsw by the air/
oxygen trading ratio to determine the equivalent remaining oxygen time at
30 fsw. Add the oxygen time shown in the table at 20 fsw to the equivalent
remaining oxygen time at 30 fsw to obtain the total remaining oxygen time.
Compute the number of chamber oxygen periods required by multiplying
the remaining oxygen time at the stops by 1.1, dividing the total by 30
minutes, then rounding the result up to the next highest half period. One
half period (15 minutes at 50 fsw) is the minimum requirement.
n For a diver at 20 fsw: Compute the air/oxygen trading ratio at 20 fsw by
dividing the 20 fsw air stop time listed in the table by the 20-fsw oxygen
time. Divide the remaining air time at 20 fsw by the air/oxygen trading
ratio to obtain the equivalent remaining oxygen time. Compute the number
of chamber oxygen periods required by multiplying the remaining oxygen
time at the stops by 1.1, dividing the total by 30 minutes, then rounding the
result up to the next highest half period. One half period (15 minutes at 50
fsw) is the minimum requirement.

CHAPTER 9 — Air Decompression

9-19

No

In-Water
Decompression on
Air > 15 min

Use
In-Water
Decompression
on Air

No

Use
In-Water
Decompression
on Air
TDT NTE 90 min

No

Chamber
Available

Yes

Yes

ORCA
Available

Yes

Use
Surface
Decompression
on oxygen

No

Chamber
Available

Use
In-Water
Decompression
on Air/O2
TDT NTE 90 min

No

Use In-Water
Decompression
on Air/O2
-orSurface
Decompression
on oxygen

Yes

In-water
Air/O2 TDT
> 90 min

Yes

Use
Surface
Decompression
on
oxygen

Figure 9‑7. Decompression Mode Selection Flowchart.
F ig ure 9-7. Decompression Mode Selection Flowchart

Example: A diver is decompressing on a schedule that calls for a single 50

min stop on air at 20 fsw. The corresponding 20 fsw oxygen stop time is 27
min. After 20 minutes on air at 20 fsw, the diving supervisor elects to surface
decompress the diver. The air/oxygen trading ratio at 20 fsw is 50/27 = 1.85,
i.e., every 1.85 minutes spent air at 20 fsw is the equivalent of 1 minute spent
on oxygen at 20 fsw. The remaining time on air at 20 fsw is 50 – 20 = 30

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U.S. Navy Diving Manual — Volume 2

minutes. The equivalent remaining oxygen time at 20 fsw is 30/1.85 = 16.2
minutes. This remaining oxygen time is rounded up to the next whole minute,
17 min. The number of 30-min SurDO2 periods required is (1.1 × 17) / 30 =
0.62. This number is rounded up to 1.0.
9-8.4

Selection of the Mode of Decompression

Figure 9-7 provides guidance for selecting the best mode of decompression for a
given dive.
In-water decompression on air is the most suitable mode for dives that do not
require more than 15 minutes of total decompression stop time. Most dives will
fall in this category. In-water decompression on air avoids the additional logistic
burden of bringing an ORCA and/or a recompression chamber to the dive station.
In-water decompression on air and oxygen is strongly recommended whenever the
total decompression stop time on air exceeds 15 minutes and surface decompression
on oxygen is not a viable alternative. Surface decompression may not be possible
either because a recompression chamber is not available on the dive station or the
short surface interval associated with surface decompression does not allow enough
time for diver decontamination following a contaminated water dive. In-water
decompression on air and oxygen is most suitable for dives that do not require more
than 90 minutes of total air and oxygen time in the water. Longer times increase the
risk of CNS oxygen toxicity and exposure to the elements. If the total air/oxygen
decompression time in the water is greater than 90 minutes, surface decompression
on oxygen is required unless CNO permission to conduct exceptional exposure dives
is obtained.
9-9

REPETITIVE DIVES

During the surface interval after an air dive, the quantity of residual nitrogen in
the diver’s body will gradually be reduced to its normal value. If the diver makes a
second dive before the residual nitrogen has been dissipated (a repetitive dive), he
must consider his residual nitrogen level when planning for the second dive.
The procedures for conducting a repetitive dive are summarized in Figure 9-8.
Upon completing the first dive, the diver is assigned a repetitive group designator
from either the Air Decompression Table or the No-Decompression Table. This
designator tells the diver how much residual nitrogen he has upon surfacing from
the first dive. A diver in Group A has the lowest amount of residual nitrogen; a diver
in Group Z has the highest. As nitrogen passes out of the diver’s body during the
surface interval, the repetitive group designation changes to a lower letter group
to reflect the lower quantity of residual nitrogen. The top half of Table 9-8 allows
the repetitive group designator to be determined at any time during the surface
interval. The lower half of Table 9-8 gives the Residual Nitrogen Time (RNT)
corresponding to the repetitive group designator at the end of the surface interval
and the depth of the repetitive dive. The residual nitrogen time is the time a diver
would have had to spend at the depth of the repetitive dive to absorb the amount

CHAPTER 9 — Air Decompression

9-21

Conduct
single
dive

Decompress according
to Air Decompression
Table or NoDecompression Table

Obtain repetitive
group designation

Enter top half Table
9-9 on diagonal
9-8

Surface interval greater
than maximum time
listed

Surfaceinterval
intervalgreater
greater
Surface
than10
10minutes
minutesbut
butless
less
than
than maximum
maximum time
time listed
listed
than

Obtain residual nitrogen time
using Residual Nitrogen
Timetable

Surface interval less
than 10 minutes

Add bottom time of
previous dive to that
of repetitive dive

Add residual
residual nitrogen
nitrogen time
time
Add
to bottom
bottom time
time of
of repetitive
repetitive
to
dive to
giving
equivalent
single
dive
obtain
equivalent
dive
bottom
time
single dive time

Decompress using schedule
Decompress
for repetitive
dive depthdive
schedule
for repetitive
and equivalent
single single
dive
depth
and equivalent
bottom
time
dive
time

Decompress from repetitive
dive using schedule for
deeper of two dives and
combined bottom times

Figure 9‑8. Repetitive Dive Flow Chart.
F ig ure 9-8. Repetitive Dive Flowchart.

9-22

U.S. Navy Diving Manual — Volume 2

of nitrogen he has left over from the previous dive. The residual nitrogen time is
added to the bottom time of the repetitive dive to obtain the Equivalent Single Dive
Time (ESDT). The decompression schedule for the repetitive dive is obtained by
entering either the Air Decompression Table or the No-Decompression Table at the
depth of the repetitive dive and the equivalent single dive time.
9-9.1

Repetitive Dive Procedure. To use the repetitive dive procedure described below,

the interval on the surface between dives must be at least 10 minutes. If the surface
interval between dives is less than 10 minutes, add the bottom time of the two
dives and enter the decompression table at the deeper of the two depths.

To determine the decompression schedule for a repetitive dive when the surface
interval is greater than 10 minutes:
1. Obtain the repetitive group designator from the Air Decompression Table or

the No-Decompression Table upon surfacing from the first dive.

2. Using the repetitive group designator, enter the top half of Table 9-8 on the

diagonal. Table 9-8 is the Residual Nitrogen Timetable for Repetitive Air
Dives.

3. Read horizontally across the row to locate the time interval that includes the

diver’s surface interval. The times are expressed in hours and minutes (e.g.,
2:21 = 2 hours 21 minutes). Each time interval has a minimum time (top limit)
and a maximum time (bottom limit). The time spent on the surface must be
between or equal to the limits of the selected interval. If the surface interval
exceeds the longest time shown in the row, the dive is not a repetitive dive. No
correction for residual nitrogen is required.

4. Read vertically down the column to obtain the repetitive group designator at

the end of the surface interval.

5. Continue down the same column to the depth row that is exactly equal or next

deeper than the depth of the repetitive dive. The time given at the intersection
of the column and row is the residual nitrogen time in minutes.

6. Add the residual nitrogen time to the actual bottom time of the repetitive dive

to get the Equivalent Single Dive Time (ESDT).

7. Enter the Air Decompression Table or No-Decompression Table at the depth

that is exactly equal to or next deeper than the actual depth of the repetitive dive.
Select the schedule that is exactly equal to or next longer than the Equivalent
Single Dive Time. Follow the prescribed decompression to the surface.

8. At depths of 10, 15, and 20 fsw, some of the higher repetitive groups do not

have a defined residual nitrogen time. These groups are marked with a double
asterisk in the lower half of Table 9-8. The RNT is undefined because the tissue
nitrogen loading associated with those repetitive groups is higher than the
nitrogen loading that could be achieved even if the diver were to remain at
those depths for an infinite period of time. A diver entering the dive in one of
those higher groups marked by a double asterisk can still perform a repetitive
dive at 10, 15 or 20 fsw because the no-decompression time at those depths
is unlimited. An RNT time is not required to make the dive. If a subsequent
repetitive dive to a deeper depth is planned, however, the diver will need a

CHAPTER 9 — Air Decompression

9-23

Date:

REPETITIVE DIVE WORKSHEET
1st DIVE
Max Depth
Bottom Time
Table & Schedule

REPET Group

Surface Interval

New Group

2nd DIVE
Max Depth
Bottom Time

MD + ESDT = Table & Schedule
+

RNT

+

=

ESDT

=

=

Table & Schedule

REPET
Group

=

Ensure the RNT Exception Rule does not apply
Surface Interval

New Group

3rd DIVE
Max Depth
Bottom Time

MD + ESDT = Table & Schedule
+

RNT

+

=

ESDT

=

=

Table & Schedule

REPET
Group

=

Ensure the RNT Exception Rule does not apply
Surface Interval

New Group

4th DIVE
Max Depth
Bottom Time

MD + ESDT = Table & Schedule
+
+

RNT

=
=

ESDT

=

Table & Schedule

REPET
Group

=

Ensure the RNT Exception Rule does not apply
Surface Interval

New Group

Figure 9‑9. Repetitive Dive Worksheet.

9-24

U.S. Navy Diving Manual — Volume 2

repetitive group at the end of the shallow dive in order to continue using the
RNT table. If a double asterisk is encountered in Table 9-8, assume that the
repetitive group remains unchanged during the course of the dive at 10, 15, or
20 fsw.
Example: A diver surfaces from a dive in repetitive Group N. Thirty minutes

later, he makes a dive to 20 fsw. The diver begins the 20 fsw dive in Group
N. The RNT time for Group N at 20 fsw is undefined. This is not a problem
because the no-decompression time at 20 fsw is unlimited. Regardless of his
starting repetitive group, the diver can spend any amount of time at 20 fsw
without incurring a decompression obligation. If a subsequent dive deeper than
20 fsw is planned, the diver should assume that he surfaced from the 20 fsw
dive in Group N regardless of the duration of the 20 fsw dive.

9. If a repetitive group is not shown in the decompression schedule, repetitive

dives deeper than 20 fsw are not allowed following a dive on that schedule. The
diver must remain on the surface for at least 18 hours before making another
dive deeper than 20 fsw.

10. Do not perform repetitive dives that require the use of Exceptional Exposure

decompression schedules.

Always use the Repetitive Dive Worksheet, shown in Figure 9-9, when determining
the decompression schedule for a repetitive dive.
Example: A repetitive dive is planned to 98 fsw for an estimated bottom time

of 15 minutes. The previous dive was to a depth of 101 fsw (100 fsw + 1 fsw
pneumofathometer correction factor) and had a bottom time of 48 minutes.
Decompression was conducted using the in-water air/oxygen option. The diver’s
surface interval is 6 hours 26 minutes (6:26). What is the proper decompression
schedule for the repetitive dive?

1. Enter the Air Decompression Table at a depth of 110 fsw and a bottom time of

50 minutes. Read across the row to obtain the repetitive group designator upon
surfacing from the first dive. The repetitive group designator is Z.

2. Move to the Residual Nitrogen Timetable for Repetitive Air Dives, Table 9-8.
3. Enter the top half of the table on the diagonal line at Z.
4. Read horizontally across the line until reaching the time interval that includes

the diver’s surface interval of 6 hours 25 minutes. The diver’s surface interval
falls within the limits of the 6:07/6:58 column.

5. Read vertically down the 6:07/6:58 column. The repetitive group designator at

the end of the surface interval is I.

6. Continue to read down the column until reaching the depth that is exactly equal

or next deeper than the depth of the repetitive dive. This is 100 fsw. The residual
nitrogen time is 30 minutes.

7. Add the 30 minutes of residual nitrogen time to the estimated bottom time of

15 minutes to obtain the single equivalent dive time of 45 minutes.

CHAPTER 9 — Air Decompression

9-25

1026
Date: 5 Sept 07

Type of Dive:

AIR

Diver 1: NDCM Boyd

HeO2

Diver 2: NDC Parson

Standby: ND3 Jones

Rig: KM-37 NS PSIG: 2900 O2%:

Rig: KM-37 NS PSIG: 2900 O2%:

Rig: KM-37 NS PSIG: 2900 O2%:

Diving Supervisor: NDCM Mariano

Chartman: ND1 Peters

Bottom Mix:

EVENT

STOP TIME

CLOCK TIME

TIME/
DEPTH

EVENT

LS or 20 fsw

0900

Descent Time (Water)

RB

0902

Stage Depth (fsw)

LB

0948

Maximum Depth (fsw)

R 1st Stop

0951

Total Bottom Time

:02
100
100+1=101
:48

190 fsw

Table/Schedule

110/50

180 fsw

Time to 1st Stop (Actual)

:02::46

170 fsw

Time to 1st Stop (Planned)

:02::40

st

160 fsw

Delay to 1 Stop

150 fsw

Travel/Shift/Vent Time

:02

140 fsw

Ascent Time-Water/SurD (Actual)

::40

130 fsw

Undress Time-SurD (Actual)

120 fsw

Descent Chamber-SurD (Actual)

110 fsw

Total SurD Surface Interval

100 fsw

Ascent Time–Chamber (Actual)

90 fsw

::06

HOLDS ON DESCENT

80 fsw

DEPTH

PROBLEM

70 fsw
60 fsw
50 fsw
40 fsw

DELAYS ON ASCENT

30 fsw
20 fsw

DEPTH
:02+:32

PROBLEM

1025

RS

1026

RB CHAMBER
50 fsw chamber

DECOMPRESSION PROCEDURES USED

40 fsw chamber

AIR
o In-water Air decompression
 In-water Air/O2 decompression
o SurDO2

30 fsw chamber
RS CHAMBER
TDT
:38

TTD
1:26

HeO2
o In-water HeO2/O2 decompression
o SurDO2
REPETITIVE GROUP: Z

Remarks:

Figure 9‑10. Completed Air Diving Chart: First Dive of Repetitive Dive Profile.

9-26

U.S. Navy Diving Manual — Volume 2

Date:

REPETITIVE DIVE WORKSHEET

5 Sept 07

1st DIVE
Max Depth

100+1=101

Bottom Time

:48

Table & Schedule

110/50

Surface Interval

6:25

REPET Group

Z

New Group

I

2nd DIVE
Max Depth

97+1=98

Bottom Time

+

RNT

=

ESDT

=

Table & Schedule

REPET
Group

+

:30

=

:45

=

100/45

N

:15

MD + ESDT = Table & Schedule

Ensure the RNT Exception Rule does not apply
Surface Interval

New Group

3rd DIVE
Max Depth
Bottom Time

MD + ESDT = Table & Schedule
+

RNT

+

=

ESDT

=

=

Table & Schedule

REPET
Group

=

Ensure the RNT Exception Rule does not apply
Surface Interval

New Group

4th DIVE
Max Depth
Bottom Time

MD + ESDT = Table & Schedule
+

RNT

+

=

ESDT

=

=

Table & Schedule

REPET
Group

=

Ensure the RNT Exception Rule does not apply
Surface Interval

New Group

Figure 9‑11. Completed Repetitive Dive Worksheet.

CHAPTER 9 — Air Decompression

9-27

1731
Date: 5 Sept 07

Type of Dive:

AIR

HeO2

Diver 1: NDCM Boyd

Diver 2: NDC Parson

Rig: KM-37 NS PSIG: 2900 O2%:

Rig: KM-37 NS PSIG: 2900 O2%:

Rig: KM-37 NS PSIG: 2900 O2%:

Diving Supervisor: NDCM
Mariano

Chartman: CWO4 Perna

Bottom Mix:

EVENT

STOP TIME

Standby: CWO5 Armstrong

CLOCK TIME

EVENT

TIME/DEPTH

LS or 20 fsw

1651

Descent Time (Water)

:02

RB

1653

Stage Depth (fsw)

97

LB

1706

Maximum Depth (fsw)

st

1709

R 1 Stop
190 fsw

97+1=98

Total Bottom Time

:15+:30=:45

Table/Schedule

100/45

st

Time to 1 Stop (Actual)

180 fsw

st

170 fsw

Time to 1

:02::35

Stop (Planned)

:02::34

160 fsw

st

Delay to 1 Stop

::01

150 fsw

Travel/Shift/Vent Time

:02

140 fsw

Ascent Time-Water/SurD (Actual)

::45

130 fsw

Undress Time-SurD (Actual)

120 fsw

Descent Chamber-SurD (Actual)

110 fsw

Total SurD Surface Interval

100 fsw

Ascent Time–Chamber (Actual)

90 fsw

HOLDS ON DESCENT

80 fsw

DEPTH

PROBLEM

70 fsw
60 fsw
50 fsw
40 fsw

DELAYS ON ASCENT

30 fsw
20 fsw

DEPTH
:02+:19

PROBLEM

1730

RS

1731

RB CHAMBER
50 fsw chamber

DECOMPRESSION PROCEDURES USED

40 fsw chamber

AIR
o In-water Air decompression
 In-water Air/O2 decompression
o SurDO2

30 fsw chamber
RS CHAMBER
TDT
:25

TTD
:40

HeO2
o In-water HeO2/O2 decompression
o SurDO2
REPETITIVE GROUP: N

Remarks:

Figure 9‑12. Completed Air Diving Chart: Second Dive of Repetitive Dive Profile.

9-28

U.S. Navy Diving Manual — Volume 2

8. The diver will be decompressed on the 100 fsw/45 min schedule in the Air

Decompression Table.

Figure 9-10 depicts the dive profile for the first dive, Figure 9-11 shows the
completed Repetitive Dive Worksheet, and Figure 9-12 shows the dive profile for
the repetitive dive.
9-9.2

RNT Exception Rule. In some cases, the residual nitrogen time given in Table 9-8

may be longer than needed to provide adequate decompression on the repetitive
dive. This situation is most likely to occur when the surface interval between the
dives is short. After determining the decompression requirement for the repetitive
dive using the procedure in paragraph 9-9.1, the diver should recalculate the
requirement by summing the bottom times of the two dives and taking the deepest
depth. If the resultant table and schedule produces a longer no-decompression
time or a shorter decompression time than the procedure in paragraph 9-9.1, the
table and schedule with the lesser decompression obligation may be used. This
alternative method of determining the table and schedule is referred to as the RNT
Exception Rule.

Example: A diver makes an air dive to 60 fsw for 40 minutes and plans to make

a repetitive air dive to 56 fsw for 20 minutes after a 30-minute surface interval.
Determine the table and schedule for the repetitive dive.
The diver surfaces from the first dive in repetitive group H. After 30 minutes on
the surface he remains in repetitive group H. The depth of the repetitive dive is
rounded up to the next deeper depth in Table 9-8, 60 fsw. The residual nitrogen
time for a group H diver at 60 fsw is 46 minutes. The equivalent single dive time of
the repetitive dive is 20 + 46 = 66 minutes. The 60 fsw/70 min schedule calls for a
7 min stop on air at 20 fsw. The alternative table and schedule for the repetitive dive
is 60 fsw (deepest of the two depths) and 60 minutes (sum of the 40 and 20-minute
bottom times). The 60 fsw / 63 min schedule does not require decompression stops.
The diver uses the 60 fsw / 63 min schedule for the repetitive dive under the RNT
exception rule.

Example: A diver makes a dive to 100 fsw for 25 minutes and plans to make a

repetitive dive to 60 fsw for 20 minutes after a 30-minute surface interval. Determine
the table and schedule for the repetitive dive.
The diver surfaces from the first dive in repetitive group H. After 30 minutes on the
surface, he remains in repetitive group H. The residual nitrogen time for group H
at 60 fsw is 46 minutes. The equivalent single dive time of the repetitive dive is 20
+ 46 = 66 minutes. The 60 fsw / 70 min schedule calls for a 7 min stop on air at 20
fsw. The alternative table and schedule for the repetitive dive is 100 fsw (deepest
of the two depths) and 45 minutes (sum of 25 and 20-minute bottom times). The
100 fsw / 45 min schedule calls for 36 minutes on air at 20 fsw. The diver uses the
shorter 60 fsw / 70 min schedule under the provisions of paragraph 9-9.1.
The RNT exception rule can be applied to a series of repetitive dives. The table
and schedule for the next dive in the series is determined first using the procedure

CHAPTER 9 — Air Decompression

9-29

in paragraph 9-9.1, then by adding the bottom times of all the repetitive dives in
the series and taking the deepest depth. Whichever table and schedule produces the
shorter decompression time or the longer no-decompression time is the table and
schedule to be used for the repetitive dive.
9-9.3

Repetitive Air to nitrogen-oxygen Electronically Controlled (EC)-UBA or nitrogen
oxygen EC-UBA to Air Dives. The repetitive group designators for air diving and

EC-UBA diving are defined identically. This means that it is possible to perform
a repetitive dive on air following either a EC-UBA nitrogen-oxygen dive or vice
versa using the existing tables. To perform a repetitive dive on air following a
nitrogen-oxygen dive, refer to Section 15-8.2.
9-9.4

Order of Repetitive Dives. From the decompression standpoint, the most

efficient way to perform repetitive dives is to perform the deepest dive first and
the shallowest dive last. This pattern yields the most bottom time for the least
decompression time. There is no prohibition on performing repetitive dives in the
reverse order, i.e., shallowest dive first and deepest dive last, or in any random
order if the operational situation requires it. It is just that patterns other than deep
to shallow are not the most efficient in terms of decompression.
Example: A diver plans to perform two dives separated by a 30-min surface interval.
One dive is to 100 fsw for 20 min. The second dive is to 60 fsw for 20 min. Which
dive should be performed first?

Following the normal pattern of deep to shallow, the diver does the 100 fsw dive
first. He surfaces in repetitive group G and remains in Group G during the surface
interval. The RNT for Group G at 60 fsw is 40 min. The Equivalent Single Dive
Time of the 60 fsw dive therefore is 60 min (40 + 20). A 60 fsw/60 min dive is close
to the no-decompression limit. No decompression is required for either dive.
Following the reverse pattern of shallow to deep, the diver does the 60 fsw dive
first. He surfaces in repetitive Group D and remains in Group D during the surface
interval. The RNT for Group D at 100 fsw is 14 min. The Equivalent Single Dive
Time of the 100 fsw dive therefore is 34 min (14 + 20). The diver decompresses on
the 100 fsw/35 min schedule. A 15 min decompression stop at 20 fsw is required.
With the normal pattern, the diver achieved 40 minutes of bottom time without
having to decompress. With the reverse pattern the diver required 15 min of
decompression stop time for the same 40 minutes of bottom time.
9-10

EXCEPTIONAL EXPOSURE DIVES

Exceptional exposure dives are those dives in which the risk of decompression
sickness, oxygen toxicity, and/or exposure to the elements is substantially greater
than on normal working dives. These exceptional exposure schedules are intended
to be used only in emergencies such as diver entrapment. Exceptional exposures
should not be planned in advance except under the most unusual operational
circumstances. The Commanding Officer must carefully assess the need for planned
exceptional exposure diving in accordance with OPNAVINST 3150.27 (series).

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U.S. Navy Diving Manual — Volume 2

Exceptional exposure dives are defined by the required decompression time for the
decompression mode selected. The following air dives are considered exceptional
exposure.
n Any air dive deeper than 190 fsw.
n Any in-water decompression dive with a total decompression time on air or air/
oxygen greater than 90 minutes.
n Any SurDO2 dive with a chamber oxygen time greater than 120 minutes (4
oxygen periods).
NOTE
9-11

The Commanding Officer must have approval to conduct planned
exceptional exposure dives.

VARIATIONS IN RATE OF ASCENT

The following rules for correcting for variations in rate of ascent apply to all the
tables given in this chapter. The normal rate of ascent to the first stop and between
subsequent stops is 30 fsw/min. Minor variations in the rate of travel between 20
and 40 fsw/min are acceptable and do not require correction.
9-11.1

9-11.2

Travel Rate Exceeded. If the rate of ascent is greater than 40 fsw/min, stop the
ascent, allow the watches to catch up, and then continue ascent.
Early Arrival at the First Decompression Stop. If the divers arrive early at the first

decompression stop:

1. Begin timing the first stop when the required travel time has been completed.
2. If the first stop is an oxygen stop, shift the divers to oxygen upon arrival at

the stop. Begin stop time when the divers are confirmed on oxygen and the
required travel time has been completed.

9-11.3

Delays in Arriving at the First Decompression Stop

n Delay up to 1 minute. A delay of up to one minute in reaching the first
decompression stop can be ignored.
n Delay greater than 1 minute, deeper than 50 fsw. Round up the delay
time to the next whole minute and add it to the bottom time. Recompute the
decompression schedule. If no change in schedule is required, continue on
the planned decompression. If a change in schedule is required and the new
schedule calls for a decompression stop deeper than the diver’s current depth,
perform any missed deeper stops at the diver’s current depth. Do not go deeper.
Example: Divers make a dive to 115 fsw. Stage depth is 113 fsw. Bottom time
is 55 minutes. According to the 120 fsw / 55 min decompression schedule, the

CHAPTER 9 — Air Decompression

9-31

first decompression stop is 30 fsw. During ascent, the divers were delayed at
100 fsw for 3 minutes 27 seconds and it actually took 6 min 13 seconds to reach
the 30-foot decompression stop. Determine the new decompression schedule.
The total delay is 3 minutes 27 seconds. Round this delay time up to the next
whole minute, 4 minutes, and add the rounded up delay to the bottom time.
The new bottom time is 59 minutes. Re-compute the decompression schedule
using a 60-min bottom time and continue decompression according to the new
decompression schedule, 120 fsw / 60 min. This dive is illustrated in Figure 9-13.
n Delay greater than 1 minute, shallower than 50 fsw. If a delay in ascent
greater than 1 minute occurs shallower than 50 fsw, round the delay time up to
the next whole minute and add the delay time to the diver’s first decompression
stop.
Example: Divers made a dive to 113 fsw. Bottom time was 60 minutes. According
to the Air Decompression Table, the first decompression stop is at 30 fsw. During
ascent, the divers were delayed at 40 fsw and it actually took 6 minutes 20
seconds to reach the 30-fsw stop. Determine the new decompression schedule.

If the divers had maintained an ascent rate of 30 fsw/min, the correct ascent time
would have been 2 minutes 46 seconds. Because it took 6 minutes 20 seconds
to reach the 30-fsw stop, there was a delay of 3 minutes 34 seconds (6 minutes
20 seconds minus 2 minutes 46 seconds). Therefore, increase the length of the
30-fsw decompression stop by 3 minutes 34 seconds, rounded up to 4 minutes.
Instead of 14 minutes on oxygen at 30 fsw, the divers must spend 18 minutes
on oxygen. This dive is illustrated in Figure 9-14.
9.11.4

Delays in Leaving a Stop or Between Decompression Stops.

n Delay less than 1 minute leaving an air stop. When the delay in leaving
an air stop is less than 1 minute, disregard the delay. Resume the normal
decompression when the delay is over.
n Delay less than 1 minute between air stops. If the delay between stops is less
than 1 minute, disregard the delay.
n Delay greater than 1 minute leaving an air stop or between air stops deeper
than 50 fsw. Add the delay to the bottom time and recalculate the required
decompression. If a new schedule is required, pick up the new schedule at
the present stop or subsequent stop if delay occurs between stops. Ignore any
missed stops or time deeper than the depth at which the delay occurred.
n Delay greater than 1 minute leaving an air stop or between air stops
shallower than 50 fsw. Ignore the delay. Resume the normal schedule upon
completion of the delay.
n Delay leaving an oxygen stop at 30 fsw or delay between oxygen stops at
30 and 20 fsw. Subtract any delay in leaving the 30 fsw oxygen stop or any
9-32

U.S. Navy Diving Manual — Volume 2

1503
Date: 22 Oct 07

Type of Dive:

Diver 1: ND1 Schlabach
Rig: KM 37

PSIG:

HeO2

Diver 2: ND2 Hedrick
O2%:

Diving Supervisor: NDC Blanton
EVENT

AIR

STOP TIME

Rig: KM 37

Standby: HM2 Montgomery

PSIG:

O2%:

Rig: KM 37

Chartman: LT Slappy

PSIG:

O2%:

Bottom Mix:

CLOCK TIME

EVENT

TIME/DEPTH

LS or 20 fsw

1300

Descent Time (Water)

:02

RB

1302

Stage Depth (fsw)

113

LB

1355

Maximum Depth (fsw)

113+2=115

st

1402

Total Bottom Time

:55+:04=:59

R 1 Stop
190 fsw

Table/Schedule

120/60

st

Time to 1 Stop (Actual)

180 fsw

st

170 fsw

Time to 1

:06::13

Stop (Planned)

:02::46

160 fsw

st

Delay to 1 Stop

:03::27

150 fsw

Travel/Shift/Vent Time

:02

140 fsw

Ascent Time-Water/SurD (Actual)

:45

130 fsw

Undress Time-SurD (Actual)

120 fsw

Descent Chamber-SurD (Actual)

110 fsw

Total SurD Surface Interval

100 fsw

:3::27

1359

Ascent Time–Chamber (Actual)

90 fsw

HOLDS ON DESCENT

80 fsw

DEPTH

PROBLEM

70 fsw
60 fsw
50 fsw
40 fsw

DELAYS ON ASCENT

30 fsw

:02+:14

1418

DEPTH

PROBLEM

20 fsw

:16+:05+:23

1502

100

fouled

RS

1503

RB CHAMBER
50 fsw chamber

DECOMPRESSION PROCEDURES USED

40 fsw chamber

AIR
o In-water Air decompression
 In-water Air/O2 decompression
o SurDO2

30 fsw chamber
RS CHAMBER
TDT
1:08

TTD
2:03

HeO2
o In-water HeO2/O2 decompression
o SurDO2
REPETITIVE GROUP: Z

Remarks: Diver fouled at 100 fsw for :3::27. Rounded up to :4 add to BT, Re-compute T/S

Figure 9‑13. Completed Air Diving Chart: Delay in Ascent deeper than 50 fsw.

CHAPTER 9 — Air Decompression

9-33

1711
Date: 22 Oct 07

Type of Dive:

Diver 1: ND1 Bauer
Rig: KM 37

PSIG:

HeO2

Diver 2: ND2 Brown
O2%:

Diving Supervisor: NDC Poulan
EVENT

AIR

STOP TIME

Rig: KM 37

Standby: HM2 Seymour

PSIG:

O2%:

Rig: KM 37

Chartman: CDR Daubon

PSIG:

O2%:

Bottom Mix:

CLOCK TIME

EVENT

TIME/DEPTH

LS or 20 fsw

1500

Descent Time (Water)

:02

RB

1502

Stage Depth (fsw)

113

LB

1600

Maximum Depth (fsw)

st

1607

R 1 Stop

113+2=115

Total Bottom Time

:60

190 fsw

Table/Schedule

120/60

180 fsw

Time to 1st Stop ( Actual)

:06::20

170 fsw

Time to 1

st

Stop (Planned)

:02::46

160 fsw

st

Delay to 1 Stop

:03::34

150 fsw

Travel/Shift/Vent Time

:02

140 fsw

Ascent Time-Water/SurD (Actual)

:45

130 fsw

Undress Time-SurD (Actual)

120 fsw

Descent Chamber-SurD (Actual)

110 fsw

Total SurD Surface Interval

100 fsw

Ascent Time–Chamber (Actual)

90 fsw

HOLDS ON DESCENT

80 fsw

DEPTH

PROBLEM

70 fsw
60 fsw
50 fsw
40 fsw

:03::34

1606

30 fsw

:02+:04+:14

1626

DEPTH

PROBLEM

20 fsw

:12+:05+:27

1710

40

fouled

RS

DELAYS ON ASCENT

1711

RB CHAMBER
50 fsw chamber

DECOMPRESSION PROCEDURES USED

40 fsw chamber

AIR
o In-water Air decompression
 In-water Air/O2 decompression
o SurDO2

30 fsw chamber
RS CHAMBER
TDT
1:11

TTD
2:11

HeO2
o In-water HeO2/O2 decompression
o SurDO2
REPETITIVE GROUP: Z

Remarks: Diver fouled at 40 fsw for :3::34. Rounded up to :04 add to 1st stop.

Figure 9‑14. Completed Air Diving Chart: Delay in Ascent Shallower than 50 fsw.

9-34

U.S. Navy Diving Manual — Volume 2

delay during travel from 30 to 20 fsw on oxygen from the subsequent 20-fsw
oxygen stop time. If the delay causes the total time on oxygen deeper than 20
fsw to exceed 30 minutes, shift the diver to air at the 30-minute mark. When
the problem has been resolved, shift the diver back to oxygen and resume
decompression. Ignore any time spent on air.
Example: The diver’s decompression schedule calls for a 20 min stop on
oxygen at 30 fsw and a 40 min stop on oxygen at 20 fsw. The diver has a 15
min delay leaving the 30-fsw stop due to a stage malfunction.

The first 10 minutes of the delay can be spent on oxygen at 30 fsw, giving a
total oxygen time of 30 minutes at 30 fsw. The diver should then be shifted to
air for the remaining 5 minutes of the delay. When the problem is resolved,
switch the diver back to oxygen at 30 fsw and ascend to 20 fsw to begin the 20fsw stop time. The 20-fsw stop time is reduced from 40 to 30 minutes because
of the extra 10 minutes spent on oxygen at 30 fsw. The 5 minute air break is
ignored.
n Delay in leaving the 20-fsw oxygen stop. Delays leaving the 20-fsw oxygen
stop can be ignored. However, do not leave divers on oxygen longer than 30
minutes as described in paragraph 9-8.2.2. Shift the divers to air and remain on
air until travel to the surface is possible.
n Delay in Travel from 40 fsw to the Surface for Surface Decompression.
Disregard any delays in travel from 40 fsw to the surface during surface
decompression unless the diver exceeds the allowed 5-minute surface interval.
If the diver exceeds the 5-minute surface interval, follow the guidance in
paragraph 9-12.6.
9-12

EMERGENCY PROCEDURES

In air diving, specific procedures are used in emergency situations. The following
paragraphs detail these emergency procedures.
9-12.1

Bottom Time in Excess of the Table

In the rare instance of diver entrapment or umbilical fouling, bottom time may
exceed the longest bottom time listed in the table for the diver’s depth. When it is
foreseen the bottom time will exceed the longest listed value, immediately contact
the Navy Experimental Diving Unit for advice on how to decompress. If the Navy
Experimental Diving Unit cannot be contacted in time, take the following action:
1. If available, use the U.S. Navy Thalmann Algorithm Dive Planner to compute

the decompression requirement.

2. Read down to deeper depths in the Air Decompression Table until a depth is

found that has a schedule that is equal to or longer than the bottom time. The Air

CHAPTER 9 — Air Decompression

9-35

Decompression Table contains longer schedules at various depths especially
for this purpose.
Example: A diver is trapped on the bottom at a depth of 155 fsw. By the time he
is freed, the bottom time is 100 min. The longest schedule in the 160 fsw table is
80 min. Read down to the 170 fsw table. The 120 min schedule is longer than the
diver’s bottom time. Decompress the diver on the 170 fsw / 120 minute schedule.

9-12.2

Loss of Oxygen Supply in the Water

If the diver cannot be shifted to oxygen at 30 or 20 fsw:
1. Have the diver continue to breathe air while the problem is investigated.
2. If the problem can be corrected quickly, ventilate the diver with oxygen as

soon as the gas supply is restored. Consider any time spent on air as dead time.
Remain on oxygen at the stop for the full stop time listed in the table.

3. If the problem cannot be corrected, initiate surface decompression or continue

decompression in the water on air. In this situation, the surface interval for
surface decompression is the time from leaving the in-water stop to reaching
the 50-fsw stop in the recompression chamber.

If the oxygen supply is lost during the 30 or 20-fsw water stops after the diver has
shifted to oxygen:
1. Shift the diver back to air.
2. If the problem can be corrected quickly, re-ventilate the diver with oxygen and

resume the schedule at the point of interruption. Consider any time spent on air
as dead time.

3. If the problem cannot be corrected and a recompression chamber is available

on the dive station, initiate surface decompression. Compute the number of
chamber oxygen periods required by multiplying the remaining oxygen time at
the stops by 1.1, dividing the total by 30 minutes, then rounding the result up
to the next highest half period. One half period (15 minutes at 50 fsw) is the
minimum requirement.

Example: The oxygen supply is lost permanently when the diver has a

remaining oxygen time of 5 minutes at 30 fsw and 33 minutes at 20 fsw. The
total remaining oxygen time is 38 minutes. The number of 30-min SurDO2
periods required is (1.1 × 38) / 30 = 1.39. This number is rounded up to 1.5.

4. If the problem cannot be corrected and a recompression chamber is not available

on the dive station, continue decompression on air in the water. Compute the
remaining stop time on air at the depth of the loss by multiplying the remaining

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U.S. Navy Diving Manual — Volume 2

stop time on oxygen at that depth by the ratio of the air stop time to the oxygen
time at that depth.
Example: The oxygen supply is lost permanently when the diver has a

remaining oxygen time of 10 minutes at 20 fsw. His decompression schedule
calls for either 140 minutes on air at 20 fsw or 34 minutes on oxygen at 20 fsw.
The ratio of air stop time to oxygen time at the 20-fsw stop is 140/34 = 4.12.
His remaining time on air at 20 fsw is 10 × 4.12 = 41.2 minutes. Round this
time up to 42 minutes.
If the shift to air occurs at 30 fsw, compute the remaining stop time on air at 30
fsw as shown above, then take the full 20-fsw air stop as prescribed in the Air
Decompression Table.

9-12.3

Contamination of Oxygen Supply with Air

It will be difficult to detect mixing of air with the oxygen supply during oxygen
decompression in the water as no voice change will occur as it does in heliumoxygen diving. On shifting to oxygen, the ORCA operator should verify that the
ORCA is properly lined up and that the oxygen monitor, if one is present, indicates
100% oxygen going to the diver’s umbilical. The diver should monitor his EGS
pressure gauge periodically to ensure that there is no drop in pressure.
If the operator discovers that the ORCA is improperly lined up, take the following
action:
1. Align the ORCA properly.
2. Re-ventilate each diver with oxygen for 20 seconds.
3. Restart oxygen time. Consider any time spent on contaminated oxygen as dead

time.

9-12.4

CNS Oxygen Toxicity Symptoms (Non-convulsive) at 30 or 20 fsw Water Stop

Most divers will easily tolerate the oxygen exposures prescribed by these Tables.
CNS oxygen toxicity symptoms, if they do develop, are most likely to occur near
the end of the 20-fsw oxygen stop. Nausea is the most likely symptom.
If the diver develops symptoms of CNS toxicity at the 30- or 20-fsw water stops,
take the following action:
1. If a recompression chamber is available on the dive station, initiate surface

decompression. Shift the console to air during travel to the surface. Compute
the number of chamber oxygen periods required by multiplying the remaining
oxygen time at the stops by 1.1, dividing the total by 30 minutes, then rounding
the result up to the next highest half period. One half period (15 minutes at 50
fsw) is the minimum requirement.

CHAPTER 9 — Air Decompression

9-37

2. If a recompression chamber is not available on the dive station and the event

occurs at 30 fsw, bring the divers up 10 fsw and shift to air to reduce the partial
pressure of oxygen. Shift the console as the divers are traveling to 20 fsw.
Ventilate both divers with air upon arrival at 20 fsw. Ventilate the affected
diver first. Complete the decompression on air at 20 fsw. Compute the 20-fsw
stop time as follows: Multiply the missed stop time on oxygen at 30 fsw by the
ratio of the air to oxygen stop time at 30 fsw to obtain the equivalent missed
air time at 30 fsw. Add this time to the 20-fsw air stop time shown in the Air
Decompression Table.

3. If a recompression chamber is not available on the dive station and the event

occurs at 20 fsw, shift the console to air, ventilate both divers, affected diver
first, and complete the decompression in the water at 20 fsw on air. Compute the
remaining stop time on air at 20 fsw by multiplying the remaining stop time on
oxygen at 20 fsw by the ratio of the air stop time to the oxygen time at 20 fsw.
Example: After 10 minutes on oxygen at 30 fsw, a diver has a non-convulsive

CNS oxygen toxicity symptom. A recompression chamber is not available on
the dive station. The diver is immediately brought up to 20 fsw and ventilated
with air. His decompression schedule calls for 28 minutes on air at 30 fsw and
175 minutes on air at 20 fsw. The oxygen stop time at 30 fsw is 14 minutes.
The missed oxygen time at 30 fsw is 4 minutes (14 – 10). The ratio of air to
oxygen time at 30 fsw is 28/14 = 2.0. The missed air time at 30 fsw therefore
is 4 × 2.0 = 8 minutes. The required air decompression time at 20 fsw is 183
minutes (8 + 175).

Example: After 21 minutes on oxygen at 20 fsw, a diver has a non-convulsive
CNS oxygen toxicity symptom. A recompression chamber is not available
on the dive station. The diver is shifted to air with 10 min of oxygen time
remaining at 20 fsw. His decompression schedule calls for either 140 minutes
on air at 20 fsw or 31 minutes on oxygen at 20 fsw. The ratio of air stop time to
oxygen time at the 20-fsw stop is 140/31 = 4.52. His remaining time on air at
20 fsw is 10 × 4.52 = 45.2 minutes. Round this time up to 46 minutes.
9-12.5

Oxygen Convulsion at the 30- or 20-fsw Water Stop

If symptoms progress to an oxygen convulsion despite the above measures, or if a
convulsion occurs suddenly without warning, take the following action.
1. Shift both divers to air if this action has not already been taken.
2. Have the unaffected diver ventilate himself and then ventilate the stricken

diver.

3. If only one diver is in the water, launch the standby diver immediately and have

him ventilate the stricken diver.

4. Hold the divers at depth until the tonic-clonic phase of the convulsion has

subsided. The tonic-clonic phase of a convulsion generally lasts 1–2 minutes.

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U.S. Navy Diving Manual — Volume 2

5. At the end of the tonic-clonic phase, have the dive partner or standby diver

ascertain whether the diver is breathing. The presence or absence of breath
sounds will usually be audible over the diver communication system.

6. If the diver appears not to be breathing, have the dive partner or standby diver

attempt to reposition the head to open the airway. Airway obstruction will be
the most common reason why an unconscious diver fails to breathe.

7. If the diver is breathing, hold him at depth until he is stable, then surface

decompress. Compute the number of chamber oxygen periods required by
multiplying the remaining oxygen time at the stops by 1.1, dividing the total
by 30 min, then rounding the result up to the next highest half period. One half
period (15 minutes at 50 fsw) is the minimum requirement.

8. If surface decompression is not feasible, continue decompression on air in the

water. Compute the remaining stop time on air at the depth of the incident by
multiplying the remaining stop time on oxygen at that depth by the ratio of the
air stop time to the oxygen time at that depth. If the shift to air occurs at 30 fsw,
compute the remaining stop time on air at 30 fsw, then take the full 20-fsw air
stop as prescribed in the Air Decompression Table.

9. If it is not possible to verify that the affected diver is breathing, leave the

unaffected diver at the stop to complete decompression, and surface the
affected diver and the standby diver at 30 fsw/min. The standby diver should
attempt to maintain an open airway on the stricken diver during ascent. On the
surface, the affected diver should receive any necessary airway support and be
immediately recompressed and treated for arterial gas embolism in accordance
with Figure 17-1.

9-12.6

Surface Interval Greater than 5 Minutes. If the time from leaving 40 fsw in the
water to the time of arrival at 50 fsw in the chamber during surface decompression
exceeds 5 minutes, take the following action:
1. If the surface interval is more than 5 minutes but less than or equal to 7 minutes,

increase the time on oxygen at 50 fsw from 15 to 30 minutes, i.e., add onehalf oxygen period to the 50 fsw chamber stop. Ascend to 40 fsw during the
subsequent air break. The 15-min penalty is considered a part of the normal
surface decompression procedure, not an emergency procedure.

Example: Divers are decompressing on a SurDO2 schedule that requires 1.5
oxygen breathing periods. It took 6 minutes and 20 seconds to travel from 40
fsw to the surface, undress the diver, and recompress to 50 fsw in the chamber.
The divers are placed on oxygen at 50 fsw in the chamber. They will breathe
oxygen at 50 fsw for the 15 minutes (one-half period) required by the original
schedule plus an additional 15 minutes to compensate for exceeding the normal
5-min surface interval. Upon completion of 30 minutes on oxygen at 50 fsw,
they will remove the BIBS to initiate a 5-minute air break and ascend from
50 fsw to 40 fsw at 30 fsw/min while breathing air. After 5 minutes on air, the
divers will breathe oxygen for 30 minutes to complete the oxygen time required
at 40 fsw on the original schedule. After 30 minutes on oxygen at 40 fsw, the
divers will remove the BIBS and ascend to the surface at 30 fsw/min breathing

CHAPTER 9 — Air Decompression

9-39

air. Because the divers exceeded the normal 5-minute surface interval, the total
number of oxygen periods is increased from 1.5 to 2.0.
2. If the surface interval is greater than 7 minutes, continue compression to a depth

of 60 fsw. Treat the divers on Treatment Table 5 if the original schedule required
2 or fewer oxygen periods in the chamber. Treat the divers on Treatment Table
6 if the original schedule required 2.5 or more oxygen periods in the chamber.

3. On rare occasions a diver may be unable to reach 50 fsw in the chamber due

to difficulty equalizing middle ear pressure. In this situation, an alternative
procedure for surface decompression on oxygen may be used:
n Begin oxygen breathing at the initially attained depth - presumed to be less
than 20 fsw.
n If surface decompression was initiated while the diver was decompressing
on oxygen in the water at 20 fsw, attempt to gradually compress the diver
to 20 fsw.
n If surface decompression was initiated from deeper than 20 fsw, attempt to
gradually compress the diver to 30 fsw.
n In either case, double the number of chamber oxygen periods indicated
in the table and take these periods at the deepest depth the diver is able to
attain. Oxygen time starts when the diver initially goes on oxygen.
n Interrupt oxygen breathing every 60 minutes with a 15-min air break. The
air break does not count toward the total oxygen time.
n Surface the diver at 30 fsw/min upon completion of the oxygen breathing
periods and carefully observe the diver for the onset of decompression
sickness.

This “safe way out” procedure is not intended to be used in place of normal surface
decompression procedures. Divers that experienced ear difficulty on descent in the
water column may not be good candidates for surface decompression.
Repetitive diving is not authorized following use of this procedure.
9-12.7

9-40

Decompression Sickness During the Surface Interval. If symptoms of Type
I decompression sickness occur during travel from 40 fsw to the surface during
surface decompression or during the surface undress phase, compress the diver to
50 fsw following normal surface decompression procedures. Delay neurological
exam until the diver reaches the 50-fsw stop and is on oxygen. If Type I symptoms
resolve during the 15 minute 50-fsw stop, the surface interval was 5 minutes or
less, and no neurological signs are found, increase the 50 fsw oxygen time from
15 to 30 minutes as outlined above, then continue normal decompression for the
schedule of the dive. Ascend from 50 to 40 fsw during the subsequent air break.

U.S. Navy Diving Manual — Volume 2

If Type I symptoms do not resolve during the 15 minute 50-fsw stop or symptoms
resolve but the surface interval was greater than 5 minutes, compress the diver to
60 fsw on oxygen. Treat the diver on Treatment Table 5 if the original schedule
required 2 or fewer oxygen periods in the chamber. Treat the diver on Treatment
Table 6 if the original schedule required 2.5 or more oxygen periods in the
chamber. Treatment table time starts upon arrival at 60 fsw. Follow the guidelines
for treatment of decompression sickness given in Chapter 18.
If symptoms of Type II decompression sickness occur during travel from 40 fsw
to the surface, during the surface undress phase, or the neurological examination
at 50 fsw is abnormal, compress the diver to 60 fsw on oxygen. Treat the diver on
Treatment Table 6. Treatment table time starts upon arrival at 60 fsw. Follow the
guidelines for treatment of decompression sickness given in Chapter 18.
Table 9-2 summarizes the guidance for managing an extended surface interval and
for managing Type I decompression sickness during the surface interval.
Table 9‑2. Management of Extended Surface Interval and Type I Decompression Sickness during the
Surface Interval.
Surface Interval
(Note 1)

Asymptomatic Diver

Symptomatic Diver
(Type I DCS)

5 min or less

Follow original schedule

Increase O2 time at 50 fsw from 15 to
30 min (Note 2)

Greater than 5 min but less than or
equal to 7 min

Increase O2 time at 50 fsw from 15 to
30 min

Greater than 7 min

Treatment Table 5 if 2 or fewer
SurDO2 periods
Treatment Table 6 if more than 2
SurDO2 periods

Treatment Table 5 if 2 or fewer
SurDO2 periods
Treatment Table 6 if more than 2
SurDO2 periods

Notes:
1. Surface interval is the time from leaving the 40-fsw water stop to arriving at the 50-fsw chamber stop.
2.	Type I symptoms must completely resolve during the first 15 minutes at 50 fsw and a full neurological examination at 50
fsw must be normal. If symptoms do not resolve within 15 min, treat the diver on Treatment Tables 5 or 6 as indicated for
surface intervals longer than 5 min.
3.	If Type II symptoms are present at any time during the surface interval or the neurological examination at 50 fsw is
abnormal, treat the diver on Treatment Table 6.

If DCS symptoms appear while the diver is undergoing decompression at 50, 40
or 30 fsw in the chamber, treat the symptoms as a recurrence in accordance with
Figure 17-3.
9-12.8

Loss of Oxygen Supply in the Chamber

For loss of oxygen supply in the chamber, have the diver breathe chamber air. If
the loss is temporary, return the diver to oxygen breathing. Consider any time spent
on air as dead time.

CHAPTER 9 — Air Decompression

9-41

If the loss of the oxygen supply is permanent, complete decompression in the
chamber on 50% nitrogen 50% oxygen (preferred) or on air. If 50% nitrogen
50% oxygen is available, multiply the remaining oxygen time by two to obtain
the equivalent chamber decompression time on 50/50. Air breaks are not required
when breathing 50/50. Diver may remove mask briefly (e.g., for drinking fluids).
Consider any time spent on air as dead time. If chamber air is the only gas available,
multiply the remaining chamber time on oxygen by the ratio of the water stop times
on air at 30 and 20 fsw to the oxygen time at those depths to obtain the equivalent
chamber decompression time on air. Allocate 10% of the equivalent air or 50/50
nitrogen-oxygen time to the 40-fsw stop, 20% to the 30-fsw stop, and 70% to the
20-fsw stop. If the diver is at 50 fsw when the loss occurs, ascend to 40 fsw and
begin the stop time. If the loss occurred at 30 fsw, allocate 30% of the equivalent
air or nitrogen-oxygen time to the 30-fsw stop and 70% to the 20-fsw stop. Round
the stop times to the nearest whole minute. Surface the divers upon completion of
the 20-fsw stop.
Example: A SurDO2 schedule calls for two 30-min oxygen periods in the chamber.

The chamber oxygen supply is lost permanently after 28 minutes on oxygen at 50
and 40 fsw. Chamber air is the only gas available. The remaining oxygen time is (2
× 30) – 28 = 32 minutes. The original decompression schedule calls for 52 and 140
minute in-water air decompression stops at 30 and 20 fsw for a total air stop time
of 192 minutes. The corresponding oxygen stop times are 13 and 34 minutes, for a
total of oxygen stop time of 47 min. The ratio of air stop time to oxygen stop time
is 192/47 = 4.08. The remaining chamber air time is 32 × 4.08 = 131 minutes. This
time is allocated as follows: 13 min at 40 fsw (131 × 0.1), 26 min at 30 fsw (131 ×
0.2), and 92 min at 20 fsw (131 × 0.7).

9-12.9

CNS Oxygen Toxicity in the Chamber

At the first sign of CNS oxygen toxicity, the diver should be removed from
oxygen and allowed to breathe chamber air. Fifteen minutes after all symptoms
have completely subsided, resume oxygen breathing at the point of interruption. If
symptoms develop again, or if the first symptom is a convulsion, take the following
action:
1. Remove the mask.
2. After all symptoms have completely subsided, decompress 10 feet at a rate of

1 fsw/min. For a convulsion, begin travel when the patient is fully relaxed and
breathing normally.

3. Resume oxygen breathing at the shallower depth at the point of schedule

interruption.

4. If another oxygen symptom occurs after ascending 10 fsw, complete

decompression on chamber air. Compute the remaining chamber time on air as
shown in paragraph 9-12.8 above. If the diver is at 40 fsw, allocate 10% of the
remaining air time to the 40-fsw stop, 20% to the 30-fsw stop, and 70% to the
20-fsw stop. If the diver is at 30 fsw, allocate 30% of the remaining time to the

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U.S. Navy Diving Manual — Volume 2

30-fsw stop and 70% to the 20-fsw stop. Round the stop times to the nearest
whole minute. Surface the divers upon completion of the 20-fsw stop.
9-12.10

Asymptomatic Omitted Decompression

Certain emergencies, such as uncontrolled ascents, an exhausted air supply,
or bodily injury may interrupt or prevent required decompression. If the diver
shows symptoms of decompression sickness or arterial gas embolism, immediate
treatment using the appropriate recompression treatment table is essential. Even if
the diver shows no symptoms, omitted decompression must be addressed in some
manner to avert later difficulty.
Omitted decompression may or may not be planned. Planned omitted decompression
results when a condition develops at depth that will require the diver to surface
before completing all of the decompression stops and when there is time to consider
all available options, ready the recompression chamber, and alert all personnel as
to the planned evolution. Equipment malfunctions, diver injury, or sudden severe
storms are examples of these situations. In unplanned omitted decompression, the
diver suddenly appears on the surface without warning or misses decompression
for some unforeseen reason.
Table 9-3 summarizes management of asymptomatic omitted decompression.
Table 9‑3. Management of Asymptomatic Omitted Decompression.
Action
Chamber Available
(Note 2)

No Chamber
Available

Deepest Decompression
Stop Omitted

Surface Interval
(Note 1)

None

Any

Observe on surface for 1 hour

Less than 1 min

Return to depth of stop. Increase stop time by 1 min. Resume
decompression according to original schedule.

1 to 7 min

Use Surface Decompression
Procedure (Note 3)

20 or 30 fsw

Greater than 7 min

Treatment Table 5 if 2 or fewer
SurDO2 periods

Return to depth of stop.
Multiply 30 and/or 20 fsw air
or O2 stop times by 1.5.

Treatment Table 6 If more than
2 SurDO2 periods
Deeper than
30 fsw

Any

Treatment Table 6 (Note 4)

Descend to depth of first stop.
Follow the schedule to 30
fsw. Switch to O2 at 30 fsw if
available. Multiply 30 and 20
fsw air or O2 stops by 1.5.

Notes:
1. For surface decompression, surface interval is the time from leaving the stop to arriving at depth in the chamber.
2.	Using a recompression chamber is strongly preferred over in-water recompression for returning a diver to pressure.
Compress to depth as fast as possible not to exceed 100 fsw/min.
3.	For surface intervals greater than 5 minutes but less than or equal to 7 minutes, increase the oxygen time at 50 fsw
from 15 to 30 minutes.
4.	If a diver missed a stop deeper than 50 fsw, compress to 165 fsw and start Treatment Table 6A.

CHAPTER 9 — Air Decompression

9-43

9-12.10.1

No-Decompression Stops Required

If a diver makes an uncontrolled ascent to the surface at a rate greater than 30
fsw/min, but the dive itself is within no-decompression limits, the diver should be
observed on the surface for one hour to ensure that symptoms of decompression
sickness or arterial gas embolism do not develop. Recompression is not necessary
unless symptoms develop.
9-12.10.2

Omitted Decompression Stops at 30 and 20 fsw

If the diver omits some or all of the decompression time at 30 and/or 20 fsw, take
the following action:
1. If the diver is on the surface for less than one minute, return the diver to depth

of the stop from which he came. Increase that stop time by one minute. Resume
decompression according to the original schedule.

2. If the diver is on the surface for 1 to 5 minutes and a recompression chamber

is available on dive station, place the diver in the recompression chamber and
complete the decompression using surface decompression. If the diver was on
oxygen at the time of the omission, compute the number of chamber oxygen
periods required by multiplying the remaining oxygen time at the stops by 1.1,
dividing the total by 30 min, then rounding the result up to the next highest
half period. If the diver was on air at the time of the omission, first compute the
equivalent remaining oxygen time at the stop as shown in paragraph 9-8.3.2.
If the omission occurred at 20 fsw, use this remaining oxygen time to compute
the number of oxygen periods as shown above. If the omission occurred at 30
fsw, compute the remaining oxygen time at 30 fsw, then add the oxygen time
shown in the decompression table at 20 fsw to get the total remaining oxygen
time. Use the total remaining oxygen time to compute the number of oxygen
periods. In all instances, one half period (15 minutes at 50 fsw) is the minimum
requirement.

3. If the diver is on the surface for more than 5 minutes but less than or equal to

7 minutes and a recompression chamber is available on the dive station, place
the diver in the recompression chamber and complete the decompression using
surface decompression as outlined in paragraph 2 above. Increase the time on
oxygen at 50 fsw from 15 to 30 minutes.

4. If the diver is on the surface for more than 7 minutes and a recompression

chamber is available on the dive station, treat the diver with Treatment Table
5 if the surface decompression schedule for that dive required two or fewer
oxygen periods in the chamber. Treat on Treatment Table 6 if the surface
decompression schedule for that dive required 2.5 or more oxygen periods in
the chamber.

5. If the diver is on the surface for more than 1 minute and a recompression

chamber is not available, return the diver to the depth of the omitted stop.

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U.S. Navy Diving Manual — Volume 2

Complete decompression in the water by multiplying the 30- and/or 20-fsw air
or oxygen stops by 1.5.
9-12.10.3

Omitted Decompression Stops Deeper than 30 fsw

If the diver omits part or all of a decompression stop at 40 fsw or deeper and
a recompression chamber is available on the dive station, treat the diver with
Treatment Table 6. If a recompression chamber is not available on the dive station,
return the diver to the depth of the first decompression stop. Follow the original
decompression schedule to 30 fsw. At 30 fsw, shift the diver to oxygen if it is
available. Complete decompression from 30 fsw by multiplying the 30- and 20-fsw
air or oxygen stops by 1.5.
9-12.11

Decompression Sickness in the Water.

In rare instances, decompression sickness may develop in the water during
prolonged decompression on air or air/oxygen. The predominant symptom will
usually be joint pain but more serious manifestations such as numbness, weakness,
hearing loss, and vertigo may also occur. Decompression sickness is most likely
to appear at the shallow stops just prior to surfacing. Some cases, however, have
occurred during ascent to the first stop or shortly thereafter.
Managing decompression sickness in the water will be difficult in the best of
circumstances. Only general guidance can be presented here. Management
decisions must be made on site, taking in account all known factors. The advice of
a Diving Medical Officer should be sought whenever possible.
9-12.11.1

Diver Remaining in the Water. If the diver indicates that he has decompression

sickness but feels he can remain in the water:

1. Dispatch the standby diver to assist. Continue to decompress the other divers

according to the original schedule.

2. If the diver is decompressing on air at 30 or 20 fsw, switch the diver to 100%

oxygen if available.

3. Have the diver descend 10 fsw. If significant relief of symptoms is not obtained,

have the diver descend an additional 10 fsw, but no deeper than 40 fsw if the
diver is on oxygen.

4. Remain at treatment depth for at least 30 minutes.
5. If the diver is on air, resume decompression from treatment depth by multiplying

subsequent air or oxygen stop times in the Air Decompression Table by 1.5.
If recompression went deeper than the depth of the first stop on the original
air decompression schedule, insert intervening stops in 10 fsw increments

CHAPTER 9 — Air Decompression

9-45

between the treatment depth and the original first stop depth equal to 1.5 times
the original first stop time.
6. If the diver is undergoing treatment on oxygen at 40 fsw, return to the surface

by multiplying the 30 and 20-fsw oxygen stop times by 1.5. If the original
schedule did not call for a 30-fsw oxygen stop, insert a 30-fsw oxygen stop
with a stop time equal to the 20-fsw stop time.

7. If the diver is undergoing treatment on oxygen at 30 fsw, return to the surface

by multiplying the 20-fsw oxygen stop time by 1.5.

8. If the diver is symptom-free upon surfacing, place the diver on oxygen, transport

to the nearest appropriate recompression chamber, and treat on Treatment Table
5. This requirement may be waived for dives conducted in remote locations
that do not have recompression chambers within a reasonable travel distance. If
the diver is not symptom-free upon surfacing, transport the diver to the nearest
chamber and treat on Treatment Table 6.

9. If a recompression chamber is immediately available on the dive station, the

diving supervisor may elect to forego treatment with in-water recompression
and surface the diver for treatment in the recompression chamber or treat the
diver in the water for 30 minutes to relieve symptoms, then surface the diver
for further treatment in the recompression chamber. In either case, the surface
interval should be 5 minutes or less, and the diver should be considered to
have Type II decompression sickness, even if the symptoms are Type I. After
completing recompression treatment, observe the diver for at least 6 hours. If
any symptoms recur, treat as a recurrence of Type II symptoms.

9-12.11.2

Diver Leaving the Water. If the diver indicates that he has decompression sickness

and feels he cannot safely remain in the water:

1. Surface the diver at a moderate rate (not to exceed 30 fsw/min).
2. If a Level I recompression chamber is available, recompress the diver as

outlined in step 9 above.

3. If a recompression chamber is not immediately available, transport the diver to

the nearest chamber. Follow the management guidance given in Chapter 17.

9-13

DIVING AT ALTITUDE

Because of the reduced atmospheric pressure, dives conducted at altitude require
more decompression than identical dives conducted at sea level. The air
decompression tables, therefore, cannot be used as written. Some organizations
calculate specific decompression tables for use at each altitude. An alternative
approach is to correct the altitude dive to obtain the equivalent sea level dive, then
determine the decompression requirement using standard tables. This procedure is
commonly known as the “Cross Correction” technique and always yields a sea level
dive that is deeper than the actual dive at altitude. A deeper sea level equivalent
dive provides the extra decompression needed to offset effects of diving at altitude.

9-46

U.S. Navy Diving Manual — Volume 2

9-13.1

Altitude Correction Procedure. To apply the “Cross Correction” technique, two

corrections must be made for altitude diving. First, the actual dive depth must be
corrected to determine the sea level equivalent depth. Second, the decompression
stops in the sea level equivalent depth table must be corrected for use at altitude.
Strictly speaking, ascent rate should also be corrected, but this third correction can
safely be ignored.

9-13.1.1

Correction of Dive Depth. The depth of the sea level equivalent dive is determined
by multiplying the depth of the dive at altitude by the ratio of the atmospheric
pressure at sea level to the atmospheric pressure at altitude.

Example: A diver makes a dive to 60 fsw at an altitude of 5000 feet. The
atmospheric pressure measured at 5000 feet is 843 millibars (0.832 ATA).
Atmospheric pressure at sea level is assumed to be 1013 millibars (1.000 ATA).
Sea level equivalent depth is then:

9-13.1.2

Correction of Decompression Stop Depth. The depth of the corrected stop at
altitude is calculated by multiplying the depth of a sea level equivalent stop by
the ratio of the atmospheric pressure at altitude to the atmospheric pressure at sea
level. [Note: this ratio is the inverse of the ratio in the formula above.]

Example: A diver makes a dive at an altitude of 5000 feet. An equivalent sea level

dive requires a decompression stop at 20 fsw. Stop depth used at altitude is then:

To simplify calculations, Table 9-4 gives corrected sea level equivalent depths and
equivalent stop depths for dives from 10–190 fsw and for altitudes from 1,000 to
10,000 feet in 1,000 foot increments. For exact calculations, refer to Chapter 2,
Table 2-19 for atmospheric pressure at altitude.

CHAPTER 9 — Air Decompression

9-47

Table 9‑4. Sea Level Equivalent Depth (fsw).
Altitude (feet)

Actual Depth
(fsw)

1000

2000

3000

4000

5000

6000

7000

8000

9000

10

10

15

15

15

15

15

15

15

15

15

15

15

20

20

20

20

20

20

25

25

25

20

20

25

25

25

25

25

30

30

30

30

25

25

30

30

30

35

35

35

35

35

40

30

30

35

35

35

40

40

40

45

45

45

35

35

40

40

45

45

45

50

50

50

60

40

40

45

45

50

50

50

55

55

60

60

45

45

50

55

55

55

60

60

70

70

70

50

50

55

60

60

70

70

70

70

70

80

55

55

60

70

70

70

70

80

80

80

80

60

60

70

70

70

80

80

80

90

90

90
100

65

65

70

80

80

80

90

90

90

100

70

70

80

80

90

90

90

100

100

100

110

75

75

90

90

90

100

100

100

110

110

110

80

80

90

90

100

100

100

110

110

120

120

85

85

100

100

100

110

110

120

120

120

130

90

90

100

110

110

110

120

120

130

130

140

95

95

110

110

110

120

120

130

130

140

140

100

100

110

120

120

130

130

130

140

140

150

105

105

120

120

130

130

140

140

150

150

160

110

110

120

130

130

140

140

150

150

160

160

115

115

130

130

140

140

150

150

160

170

170

120

120

130

140

140

150

150

160

170

170

180

125

125

140

140

150

160

160

170

170

180

190

130

130

140

150

160

160

170

170

180

190

190

135

135

150

160

160

170

170

180

190

190

200

140

140

160

160

170

170

180

190

190

200

210

145

145

160

170

170

180

190

190

200

210

150

160

170

170

180

190

190

200

210

210

155

170

170

180

180

190

200

160

170

180

180

190

200

200

200

165

180

180

190

200

170

180

190

190

200

175

190

190

200

180

190

200

210

185

200

200

190

200

Table
Water Stops

Note:

9-48

10000

Equivalent Stop Depths (fsw)

10

10

9

9

9

8

8

8

7

7

7

20

19

19

18

17

17

16

15

15

14

14

30

29

28

27

26

25

24

23

22

21

21

40

39

37

36

35

33

32

31

30

29

28

50

48

47

45

43

42

40

39

37

36

34

60

58

56

54

52

50

48

46

45

43

41

= Exceptional Exposure Limit

U.S. Navy Diving Manual — Volume 2

WARNING

9-13.2

Table 9-4 cannot be used when diving with equipment that maintains a
constant partial pressure of oxygen such as the MK 16 MOD 0 and the MK
16 MOD 1. Consult NAVSEA 00C for specific guidance when diving the
MK 16 at altitudes greater than 1000 feet.
Need for Correction. No correction is required for dives conducted at altitudes

between sea level and 300 feet. The additional risk associated with these dives is
minimal. At altitudes between 300 and 1000 feet, correction is required for dives
deeper than 145 fsw (actual depth). At altitudes above 1000 feet, correction is
required for all dives.

9-13.3

Depth Measurement at Altitude. The preferred method for measuring depth at

altitude is a mechanical or electronic gauge that can be re-zeroed at the dive site.
Once re-zeroed, no further correction of the reading is required.

When using a recompression chamber for decompression, zero the chamber depth
gauges before conducting surface decompression.
Most mechanical depth gauges carried by divers have a sealed one-atmosphere
reference and cannot be adjusted for altitude; thus they will read low throughout a
dive at altitude. A correction factor of 1 fsw for every 1000 feet of altitude should
be added to the reading of a sealed reference gauge before entering Table 9-4.
Pneumofathometers can be used at altitude. Add the pneumofathometer
correction factor (Table 9-1) to the depth reading before entering Table 9-4. The
pneumofathometer correction factors are unchanged at altitude.
A sounding line or fathometer may be used to measure the depth if a suitable depth
gauge is not available. These devices measure the linear distance below the surface
of the water, not the water pressure. Though fresh water is less dense than sea water,
all dives will be assumed to be conducted in sea water, thus no corrections will be
made based on water salinity. Enter Table 9-4 directly with the depth indicated on
the line or fathometer.
9-13.4

Equilibration at Altitude. Upon ascent to altitude, two things happen. The body
off-gases excess nitrogen to come into equilibrium with the lower partial pressure
of nitrogen in the atmosphere. It also begins a series of complicated adjustments
to the lower partial pressure of oxygen. The first process is called equilibration;
the second is called acclimatization. Approximately twelve hours at altitude is
required for equilibration. A longer period is required for full acclimatization.

If a diver begins a dive at altitude within 12 hours of arrival, the residual nitrogen
left over from sea level must be taken into account. In effect, the initial dive at
altitude can be considered a repetitive dive, with the first dive being the ascent
from sea level to altitude. Table 9-5 gives the repetitive group associated with an
initial ascent to altitude. Using this group and time at altitude before diving, enter
the Residual Nitrogen Timetable for Repetitive Air Dives (Table 9-8) to determine
the new repetitive group designator associated with that period of equilibration.
Determine the sea level equivalent depth for your planned dive using Table 9-4.
CHAPTER 9 — Air Decompression

9-49

Table 9‑5. Repetitive Groups Associated with Initial Ascent to Altitude.
Altitude (feet)

Repetitive Group

1000

A

2000

A

3000

B

4000

C

5000

D

6000

E

7000

F

8000

G

9000

H

10000

I

From your new repetitive group and sea level equivalent depth, determine the
residual nitrogen time associated with the dive. Add this time to the actual bottom
time of the dive. If the diver has spent enough time at altitude to desaturate beyond
repetitive group A in Table 9-8, no addition of residual nitrogen time to bottom time
is needed. The diver is “clean.”
Example: A diver ascends rapidly to 6000 feet in a helicopter and begins a dive to

100 fsw 90 minutes later. How much residual nitrogen time should be added to the
dive?

From Table 9-5, the repetitive group upon arrival at 6000 feet is Group E. During
90 minutes at altitude, the diver will desaturate to Group D. From Table 9-4, the sea
level equivalent depth for a 100 fsw dive is 130 fsw. From Table 9-8, the residual
nitrogen time for a 130 fsw dive in Group D is 11 minutes. The diver should add
11 minutes to the bottom time.
Table 9-5 can also be used when a diver who is fully equilibrated at one altitude
ascends to and dives at a higher altitude. Enter Table 9-5 with the difference
between the two altitudes to determine the initial repetitive group.
Example: Divers equilibrated at a base camp altitude of 6000 feet fly by helicopter

to the dive site at 10,000 feet. The difference between the altitudes is 4000 feet.
From Table 9-5, the initial repetitive group to be used at 10,000 feet is Group C.

WARNING

9-50

Altitudes above 10,000 feet can impose serious stress on the body resulting
in significant medical problems while the acclimatization process takes
place. Ascents to these altitudes must be slow to allow acclimatization to
occur and prophylactic drugs may be required to prevent the occurrence
of altitude sickness. These exposures should always be planned in
consultation with a Diving Medical Officer. Commands conducting diving
operations above 10,000 feet may obtain the appropriate decompression
procedures from NAVSEA 00C.

U.S. Navy Diving Manual — Volume 2

Date: __________________

DIVING AT ALTITUDE WORKSHEET
Actual Dive Site Altitude________________ feet
1. Altitude from Table 9-4 		

________ feet

2. Actual Depth of Dive (Corrected per Section 9-13.3) 		

________ fsw

3. Sea Level Equivalent Depth from Table 9-4		

________ SLED

4. Repetitive Group from Table 9-5

________

5. Time at Altitude

________ hrs

6. New Repetitive Group Designator from Table 9-8

________

7. Residual Nitrogen Time

________ min

________ min

8. Planned Bottom Time

+ ________ min

9. Equivalent Single Dive Time

= ________ min

10. Decompression Mode
o No-Decompression

o In-water Air/Oxygen Decompression

o In-water Air Decompression

o Surface Decompression Using Oxygen

11. Table/Schedule

_______ / _______

12. Decompression Schedule
Sea Level Stop Depth

Altitude Stop Depth

Water Stop Time

60 fsw

_________ fsw

________ min

50 fsw

_________ fsw

________ min

________ min *

40 fsw

_________ fsw

________ min

________ min *

30 fsw

_________ fsw

________ min

________ min *

20 fsw

_________ fsw

________ min

13. Repetitive Group Designator ______

Chamber Stop Time

* Chamber stops on SurDO2 will be at 		
50, 40, and 30 fsw

Figure 9‑15. Diving at Altitude Worksheet.

CHAPTER 9 — Air Decompression

9-51

9-13.5

Diving at Altitude Worksheet. Figure 9-15 is a diving at altitude worksheet. To

determine Sea Level Equivalent Depth (SLED) and corrected decompression stops
for an altitude dive, follow these steps:
9-13.5.1

NOTE

Corrections for Depth of Dive at Altitude and In-Water Stops.
Line 1.

Determine the dive site altitude by referring to a map or measuring the
barometric pressure. From Table 9-4, enter the altitude in feet that is
equal to or next greater than the altitude at the dive site.

Line 2.

Enter the actual depth of the dive in feet of sea water.

Refer to paragraph 9-13.3 to correct divers’ depth gauge readings to
actual depths at altitude.
Line 3.

9-13.5.2

9-52

Read Table 9-4 vertically down the Actual Depth Column. Select a
depth that is equal to or next greater than the actual depth. Reading
horizontally, select the Sea Level Equivalent Depth corresponding to
an altitude equal to or next greater than that of your dive site.

Corrections for Equilibration.
Line 4.

Enter the Repetitive Group upon arrival at altitude from Table 9-5 for
the altitude listed on Line 1.

Line 5.

Record the time in hours and minutes spent equilibrating at altitude
prior to the dive. If the equilibration time is longer than the time needed
to desaturate beyond Repetitive Group A in Table 9-8, proceed to Step
7 and enter zero.

Line 6.

Using Table 9-8, determine the Repetitive Group at the end of the predive equilibration interval.

Line 7.

Using Table 9-8, determine the Residual Nitrogen Time for the new
repetitive group designator from Line 6 and the Sea Level Equivalent
Depth from Line 3.

Line 8.

Enter the planned bottom time.

Line 9.

Add the bottom time and the residual nitrogen time to obtain the
Equivalent Single Dive Time.

Line 10.

Select the mode of decompression to be used, e.g., in-water air/oxygen.

Line 11.

Enter the Schedule from the Air Decompression Table using the Sea
Level Equivalent Depth from Line 3 and the Equivalent Single Dive
Time from Line 9.

U.S. Navy Diving Manual — Volume 2

Line 12.

NOTE

For surface decompression dives on oxygen, the chamber stops
are not adjusted for altitude. Enter the same depths as at sea level.
Keeping chamber stop depths the same as sea level provides an extra
decompression benefit for the diver on oxygen.
Line 13.

NOTE

Using the lower section of Table 9-4, read down the Table Water
Stops column on the left to the decompression stop(s) given in the
Sea Level Equivalent Depth Table/Schedule. Read horizontally to the
altitude column. Record the corresponding altitude stop depths on the
worksheet.

Record the Repetitive Group Designator at the end of the dive.

Follow all decompression table procedures for ascent and descent.
Example: Five hours after arriving at an altitude of 7750 feet, divers make a

60-minute air dive to a gauge depth of 75 fsw. Depth is measured with a pneumofathometer having a non-adjustable gauge with a fixed reference pressure of one
atmosphere. Surface decompression with oxygen will be used for decompression.
What is the proper decompression schedule?

The altitude is first rounded up to 8000 feet. A depth correction of +8 fsw
must be added to the maximum depth recorded on the fixed reference gauge. A
pneumofathometer correction factor of + 1 fsw must also be added. The diver’s
actual depth is 84 fsw. Table 9-4 is entered at an actual depth of 85 fsw. The Sea
Level Equivalent Depth for 8000 feet of altitude is 120 fsw. The repetitive group
upon arrival at altitude from Table 9-5 is Group G. This decays to Group B during
the five hours at altitude pre-dive. The residual nitrogen time for Group B at 120
fsw is 7 minutes. The Equivalent Single Dive Time therefore is 67 minutes. The
appropriate schedule from the Air Decompression Table is 120 fsw for 70 minutes.
By the schedule, a 12-minute water stop on air at 40 fsw is required followed by
two and one half oxygen periods in the chamber. The water stop is taken at a depth
of 30 fsw. The chamber stops are taken at depths of 50 and 40 fsw.
Figure 9-16 shows the filled-out Diving at Altitude Worksheet for this dive. Figure
9-17 shows the filled-out Diving Chart.
9-13.6

Repetitive Dives. Repetitive dives may be conducted at altitude. The procedure is

identical to that at sea level, with the exception that the sea level equivalent dive
depth is always used to replace the actual dive depth. Figure 9-18 is a Repetitive
Dive at Altitude Worksheet.

Example: Fourteen hours after ascending to an altitude of 7750 feet, divers make
an 82-fsw 50-minute KM 37 dive using in-water air/oxygen decompression. Depth
is measured with a pneumofathometer having a depth gauge adjustable for altitude.
After two hours and ten minutes on the surface, they make a second dive to 79 fsw
for 18 minutes and decompress using surface decompression on oxygen. What is
the proper decompression schedule for the second dive?

CHAPTER 9 — Air Decompression

9-53

DIVING AT ALTITUDE WORKSHEET
Actual Dive Site Altitude

7,750

23 Oct 07

Date:

feet

1. Altitude from Table 9-4 		

8,000

2. Actual Depth of Dive (Corrected per Section 9-13.3) 		

feet

75+8+1=84 fsw

3. Sea Level Equivalent Depth from Table 9-4		

120

4. Repetitive Group from Table 9-5

G

5. Time at Altitude

5

6. New Repetitive Group Designator from Table 9-8

B

7. Residual Nitrogen Time

7

min

hrs

SLED
min

8. Planned Bottom Time

+

60

min

9. Equivalent Single Dive Time

=

67

min

10. Decompression Mode
o No-Decompression

o In-water Air/Oxygen Decompression

o In-water Air Decompression

o Surface Decompression Using Oxygen

11. Table/Schedule

120/70

12. Decompression Schedule
Sea Level Stop Depth

Altitude Stop Depth

Water Stop Time

60 fsw

fsw

min

50 fsw

fsw

min

40 fsw

30

fsw

13

min

30 fsw

fsw

min

20 fsw

fsw

min

13. Repetitive Group Designator

Chamber Stop Time
15

min*

15+5+30+5+15 min*
min*

* Chamber stops on SurDO2 will be at 		
50, 40, and 30 fsw

Figure 9‑16. Completed Diving at Altitude Worksheet.

9-54

U.S. Navy Diving Manual — Volume 2

1247
Date: 5 Sept 07

Type of Dive:

AIR

Diver 1: ND1 Chaisson
Rig: MK-37

PSIG: 2900

O2%:

Diving Supervisor: NDCM Orns
EVENT

STOP TIME

ALTITUDE 8000
HeO2

Diver 2: ND2 Hutcheson

Standby: ND1 Collins

Rig: MK-37 PSIG: 2900 O2%:

Rig: MK-37

Chartman: ND1 Saurez

Bottom Mix:

CLOCK TIME

PSIG: 2900

EVENT

O2%:

TIME/DEPTH

LS or 20 fsw

1000

Descent Time (Water)

:02

RB

1002

Stage Depth (fsw)

84

LB

1100

Maximum Depth (fsw)

st

1102

Total Bottom Time

R 1 Stop
190 fsw

Table/Schedule

180 fsw

Time to 1st Stop (Actual)
st

170 fsw

Time to 1

75+8+1=84
:60+:07=:67
120/70 SLED
:01::32

Stop (Planned)

:01::30

st

160 fsw

Delay to 1 Stop

150 fsw

Travel/Shift/Vent Time

::02

140 fsw

Ascent Time-Water/SurD (Actual)

130 fsw

Undress Time-SurD (Actual)

:01
:03::20

120 fsw

Descent Chamber-SurD (Actual)

::40

110 fsw

Total SurD Surface Interval

:05

100 fsw

Ascent Time–Chamber (Actual)

90 fsw

:01::20

HOLDS ON DESCENT

80 fsw

DEPTH

PROBLEM

70 fsw
60 fsw
50 fsw
40 fsw
30 fsw

DELAYS ON ASCENT
:13(AIR)

1115

DEPTH

PROBLEM

20 fsw
RS

1116

RB CHAMBER

1120

50 fsw chamber

:15

1135

40 fsw chamber

:15+:5+:30+:5+:15

1245

DECOMPRESSION PROCEDURES USED
AIR
o In-water Air decompression
o In-water Air/O2 decompression
 SurDO2

30 fsw chamber
1247

RS CHAMBER
TDT
1:47

TTD

HeO2
o In-water HeO2/O2 decompression
o SurDO2

2:48

REPETITIVE GROUP: No repet
Remarks:

Figure 9‑17. Completed Air Diving Chart: Dive at Altitude.

CHAPTER 9 — Air Decompression

9-55

REPETITIVE DIVE AT ALTITUDE WORKSHEET
1.

PREVIOUS DIVE

2.

Date:

Decompression Mode

_____

minutes

o No-Decompression

o In-water Air/Oxygen Decompression

_____

SLED

o In-water Air Decompression

o Surface Decompression Using Oxygen

_____

Repetitive Group Letter Designator

SURFACE INTERVAL

3.

_____

hours

______ minutes on surface

_____

repetitive group from item 1 above

_____

new repetitive group letter designator from Residual Nitrogen Timetable

RESIDUAL NITROGEN TIME FOR REPETITIVE DIVE
Altitude from Table 9-4		

_________ feet

Actual Depth of Dive (corrected per section 9-13.3)		

_________ fsw

Sea Level Equivalent Depth of repetitive dive from Table 9-4		

_________ SLED

_____

new repetitive group letter designator from item 2 above

_____ minutes, residual nitrogen time from Residual Nitrogen Timetable
4.

EQUIVALENT SINGLE DIVE TIME
_____

minutes, residual nitrogen time from item 3 above

+ _____

minutes, actual bottom time of repetitive dive

= _____

minutes, equivalent single dive time

5.

DECOMPRESSION FOR REPETITIVE DIVE
_____

SLED of repetitive dive

_____

minutes, equivalent single dive time from item 4 above

Decompression Mode (check one)
o No-Decompression

o In-water Air/Oxygen Decompression

o In-water Air Decompression

o Surface Decompression Using Oxygen

___________ schedule used (depth/time)
Sea Level Stop Depth

Altitude Stop Depth

60 fsw
50 fsw
40 fsw
30 fsw
20 fsw

fsw
fsw
fsw
fsw
fsw

13. Repetitive Group Letter Designator ______

Water Stop Time

Chamber Stop Time

min
min
min
min
min

min*
min*
min*

*	Chamber stops on SurDO2 will be at
50, 40, and 30 fsw

Figure 9‑18. Repetitive Dive at Altitude Worksheet.

9-56

U.S. Navy Diving Manual — Volume 2

The altitude is first rounded up to 8000 feet. For the first dive, a depth correction of
+1 fsw must be added to the 82 fsw pneumofathometer reading. The divers’ actual
depth on the first dive is 83 fsw. Table 9-4 is entered at an actual depth of 85 fsw.
The Sea Level Equivalent Depth for the first dive is 120 fsw. The repetitive group
designation upon completion of the 50 minute dive is Group Z. This decays to
Group N during the 2 hour 10 minute surface interval.
The actual depth of the second dive is 80 fsw (79 fsw plus a 1 fsw pneumofathometer
correction factor). Table 9-4 is entered at an actual depth of 80 fsw. The Sea Level
Equivalent Depth for the second dive is 110 fsw. The residual nitrogen time for
Group N at 110 fsw is 42 minutes. The equivalent single dive time therefore is 60
minutes. The appropriate surface decompression schedule is 110 fsw for 60 minutes.
This schedule does not require any water stops. The divers spend 60 minutes on
oxygen (2 oxygen periods) at 50 and 40 fsw in the recompression chamber.
Figure 9-19 shows the filled-out Repetitive Dive at Altitude Worksheet for these
two dives. Figure 9-20 and Figure 9-21 show the filled-out Diving Charts for the
first and second dives.
9-14

ASCENT TO ALTITUDE AFTER DIVING / FLYING AFTER DIVING

Leaving the dive site may require temporary ascent to a higher altitude. For
example, divers may drive over a mountain pass at higher altitude or leave the
dive site by air. Ascent to altitude after diving increases the risk of decompression
sickness because of the additional reduction in atmospheric pressure. The higher the
altitude, the greater the risk. (Pressurized commercial airline flights are addressed
in Note 3 of Table 9-6).
Table 9-6 gives the surface interval (hours:minutes) required before making a
further ascent to altitude. The surface interval depends on the planned increase in
altitude and the highest repetitive group designator obtained in the previous 24hour period. Enter the table with the highest repetitive group designator obtained
in the previous 24-hour period. Read the required surface interval from the column
for the planned change in altitude.
Example: A diver surfaces from a 60 fsw for 60 minutes no-decompression dive

at sea level in Repetitive Group K. After a surface interval of 6 hours 10 minutes,
the diver makes a second dive to 30 fsw for 20 minutes placing him in Repetitive
Group F. He plans to fly home in a commercial aircraft in which the cabin pressure
is controlled at 8000 feet. What is the required interval before flying?
The planned increase in altitude is 8000 feet. Because the diver has made two dives
in the previous 24-hour period, you must use the highest repetitive group designator
of the two dives. Enter Table 9-6 at 8000 feet and read down to Repetitive Group
K. The diver must wait 15 hours 35 minutes after completion of the second dive
before flying.

CHAPTER 9 — Air Decompression

9-57

Example: Upon completion of a dive at an altitude of 4000 feet, the diver plans to

ascend to 7500 feet in order to cross a mountain pass. The diver’s repetitive group
upon surfacing is Group G. What is the required surface interval before crossing
the pass?
The planned increase in altitude is 3500 feet. Enter Table 9-6 at 4000 feet and read
down to Repetitive Group G. The diver does not require a surface interval before
crossing the pass.

Example: Upon completion of a dive at 2000 feet, the diver plans to fly home in an

un-pressurized aircraft at 5000 feet. The diver’s repetitive group designator upon
surfacing is Group K. What is the required surface interval before flying?
The planned increase in altitude is 3000 feet. Enter Table 9-6 at 3000 feet and
read down to Repetitive Group K. The diver must delay 3 hours 47 minutes before
taking the flight.

9-15

DIVE COMPUTER

The wrist-worn Cochran Navy Air III decompression computer may be used in
lieu of the decompression tables contained in this chapter. The Air III is intended
for no-decompression diving only. Once a diver exceeds the no-decompression
limit, the decompression obligation prescribed by the Air III will build rapidly
and may result in the diver running out of air before the decompression time
can be completed. If a diver does develop a decompression obligation while
diving the Air III, he should immediately abort the dive to minimize further
accumulation of decompression time and ascend to the surface taking the stops
indicated by the computer.
The Air III is not authorized for altitude diving operations above 2000 feet.
Once the AIR III switches back to a “first dive” surface display when activated,
the diver has completed his off gassing and may be considered a clean diver
with no restrictions on air travel or subsequent dives using other methods of
decompression. If repetitive dives are to be made, divers must use the same Air
III throughout the series of dives. Buddy pairs must remain the same to insure
equal amounts of residual nitrogen time.
NOTE:

9-58

The Air III is not a substitute for ORM. Proper planning of the diving
evolution is essential.

U.S. Navy Diving Manual — Volume 2

REPETITIVE DIVE AT ALTITUDE WORKSHEET
1.

PREVIOUS DIVE

2.

Date:

Decompression Mode

50

minutes

o No-Decompression

 In-water Air/Oxygen Decompression

120

SLED

o In-water Air Decompression

o Surface Decompression Using Oxygen

Z

Repetitive Group Letter Designation

SURFACE INTERVAL

3.

2

hours

10

minutes on surface

Z

repetitive group from item 1 above

N

new repetitive group letter designator from Residual Nitrogen Timetable

RESIDUAL NITROGEN TIME FOR REPETITIVE DIVE
Altitude from Table 9-4		

8,000

Actual Depth of Dive (corrected per section 9-13.3)		

4.

feet

79+1=80 fsw

Sea Level Equivalent Depth of repetitive dive from Table 9-4		

5.

23 Oct 07

110

N

new repetitive group letter designator from item 2 above

42

minutes, residual nitrogen time from Residual Nitrogen Timetable

SLED

EQUIVALENT SINGLE DIVE TIME
42

minutes, residual nitrogen time from item 3 above

+

18

minutes, actual bottom time of repetitive dive

=

60

minutes, equivalent single dive time

DECOMPRESSION FOR REPETITIVE DIVE
110

SLED of repetitive dive

60

minutes, equivalent single dive time from item 4 above

Decompression Mode (check one)
o No-Decompression

o In-water Air/Oxygen Decompression

o In-water Air Decompression

 Surface Decompression Using Oxygen

110/60

schedule used (depth/time)

Sea Level Stop Depth

Altitude Stop Depth

60 fsw
50 fsw
40 fsw
30 fsw
20 fsw
13. Repetitive Group Letter Designator

Water Stop Time

fsw
fsw
fsw
fsw
fsw

min
min
min
min
min

Chamber Stop Time
15
min*
15+3+30 min*
min*

*	Chamber stops on SurDO2 will be at
50, 40, and 30 fsw

Figure 9‑19. Completed Repetitive Dive at Altitude Worksheet.

CHAPTER 9 — Air Decompression

9-59

1038
Date: 23 Oct 07

Type of Dive:

Diver 1: ND1 Sullivan
Rig: KM 37

HeO2

Diver 2: ND2 Schleef

PSIG: 2900

O2%:

Diving Supervisor: NDCM Van
Horn
EVENT

AIR

ALTITUDE 8000

STOP TIME

Rig: KM 37

Standby: ND2 Bartley

PSIG: 2900

O2%:

Rig: KM 37

Chartman: ND2 Bradley

PSIG: 2900

O2%:

Bottom Mix:

CLOCK TIME

EVENT

TIME/DEPTH

LS or 20 fsw

0900

Descent Time (Water)

:02

RB

0902

Stage Depth (fsw)

82

LB

0950

Maximum Depth (fsw)

st

0952

R 1 Stop

Total Bottom Time

190 fsw

Table/Schedule

180 fsw

Time to 1st Stop (Actual)
st

170 fsw

82+1=83

Time to 1

:50
120/50 SLED
:01::44

Stop (Planned)

:01::44

st

160 fsw

Delay to 1 Stop

150 fsw

Travel/Shift/Vent Time

:02

140 fsw

AscentTime-Water/SurD (Actual)

::45

130 fsw

Undress Time-SurD (Actual)

120 fsw

Descent Chamber-SurD (Actual)

110 fsw

Total SurD Surface Interval

100 fsw

Ascent Time–Chamber (Actual)

90 fsw

HOLDS ON DESCENT

80 fsw

DEPTH

PROBLEM

70 fsw
60 fsw
50 fsw
40 fsw

DELAYS ON ASCENT

30 fsw

:02+:05

0959

20 fsw

:15+:05+:18

1037

RS

DEPTH

PROBLEM

1038

RB CHAMBER
50 fsw chamber

DECOMPRESSION PROCEDURES USED

40 fsw chamber

AIR
o In-water Air decompression
 In-water Air/O2 decompression
o SurDO2

30 fsw chamber
RS CHAMBER
TDT
:48

TTD
1:38

HeO2
o In-water HeO2/O2 decompression
o SurDO2
REPETITIVE GROUP: Z

Remarks:

Figure 9‑20. Completed Air Diving Chart: First Dive of Repetitive Dive Profile at Altitude.

9-60

U.S. Navy Diving Manual — Volume 2

Date: 23 Oct 07

Type of Dive:

Diver 1: ND1 Sullivan
Rig: KM 37

ALTITUDE 8000

AIR

HeO2

Diver 2: ND2 Schleef

PSIG: 2900

O2%:

Diving Supervisor: NDCM Van
Horn
EVENT

1420

STOP TIME

Rig: KM 37

Standby: ND2 Bartley

PSIG: 2900

O2%:

Rig: KM 37

Chartman: ND2 Bradley

PSIG: 2900

O2%:

Bottom Mix:

CLOCK TIME

EVENT

TIME/DEPTH

LS or 20 fsw

1248

Descent Time (Water)

:02

RB

1250

Stage Depth (fsw)

79

LB

1306

Maximum Depth (fsw)

st

1309

Total Bottom Time

:18 + :42 = 60

Table/Schedule

110/60 SLED

R 1 Stop
190 fsw

79+1=80

st

Time to 1 Stop (Actual)

180 fsw
170 fsw

Time to 1

st

:02::20

Stop (Planned)

:02::18

st

160 fsw

Delay to 1 Stop

150 fsw

Travel/Shift/Vent Time

::02

140 fsw

AscentTime-Water/SurD (Actual)

130 fsw

Undress Time-SurD (Actual)

:01
:02::30

120 fsw

Descent Chamber-SurD (Actual)

110 fsw

Total SurD Surface Interval

:04::20

100 fsw

Ascent Time–Chamber (Actual)

:01::20

90 fsw

::50

HOLDS ON DESCENT

80 fsw

DEPTH

PROBLEM

70 fsw
60 fsw
50 fsw
40 fsw

DELAYS ON ASCENT

30 fsw

DEPTH

PROBLEM

20 fsw
RS

1309

RB CHAMBER

1313

50 fsw chamber

:15

1328

40 fsw chamber

:15+:5+:30

1418

DECOMPRESSION PROCEDURES USED
AIR
o In-water Air decompression
o In-water Air/O2 decompression
 SurDO2

30 fsw chamber
RS CHAMBER
TDT
1:14

1420
TTD
1:32

HeO2
o In-water HeO2/O2 decompression
o SurDO2
REPETITIVE GROUP: Z

Remarks:

Figure 9‑21. Completed Air Diving Chart: Second Dive of Repetitive Dive Profile at Altitude.

CHAPTER 9 — Air Decompression

9-61

Table 9‑6. Required Surface Interval Before Ascent to Altitude After Diving.
Repetitive
Group
Designator

Increase in Altitude (feet)
1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

A

0:00

0:00

0:00

0:00

0:00

0:00

0:00

0:00

0:00

0:00

B

0:00

0:00

0:00

0:00

0:00

0:00

0:00

0:00

0:00

1:42

C

0:00

0:00

0:00

0:00

0:00

0:00

0:00

0:00

1:48

6:23

D

0:00

0:00

0:00

0:00

0:00

0:00

0:00

1:45

5:24

9:59

E

0:00

0:00

0:00

0:00

0:00

0:00

1:37

4:39

8:18

12:54

F

0:00

0:00

0:00

0:00

0:00

1:32

4:04

7:06

10:45

15:20

G

0:00

0:00

0:00

0:00

1:19

3:38

6:10

9:13

12:52

17:27

H

0:00

0:00

0:00

1:06

3:10

5:29

8:02

11:04

14:43

19:18

I

0:00

0:00

0:56

2:45

4:50

7:09

9:41

12:44

16:22

20:58

J

0:00

0:41

2:25

4:15

6:19

8:39

11:11

14:13

17:52

22:27

K

0:30

2:03

3:47

5:37

7:41

10:00

12:33

15:35

19:14

23:49

L

1:45

3:18

5:02

6:52

8:56

11:15

13:48

16:50

20:29

25:04

M

2:54

4:28

6:12

8:01

10:06

12:25

14:57

18:00

21:38

26:14

N

3:59

5:32

7:16

9:06

11:10

13:29

16:02

19:04

22:43

27:18

O

4:59

6:33

8:17

10:06

12:11

14:30

17:02

20:05

23:43

28:19

Z

5:56

7:29

9:13

11:03

13:07

15:26

17:59

21:01

24:40

29:15

Exceptional Exposure

Wait 48 hours before ascent

NOTE 1 When using Table 9-6, use the highest repetitive group designator obtained in the previous 24-hour
period.
NOTE 2 Table 9-6 may only be used when the maximum altitude achieved is 10,000 feet or less. For ascents
above 10,000 feet, consult NAVSEA 00C for guidance.
NOTE 3 The cabin pressure in commercial aircraft is maintained at a constant value regardless of the actual
altitude of the flight. Though cabin pressure varies somewhat with aircraft type, the nominal value is
8,000 feet. For commercial flights, use a final altitude of 8,000 feet to compute the required surface
interval before flying.
NOTE 4 No surface interval is required before taking a commercial flight if the dive site is at 8,000 feet or
higher. In this case, flying results in an increase in atmospheric pressure rather than a decrease.
NOTE 5 For ascent to altitude following a non-saturation helium-oxygen dive, wait 12 hours if the dive was
a no-decompression dive. Wait 24 hours if the dive was a decompression dive.

9-62

U.S. Navy Diving Manual — Volume 2

Table 9‑7. No-Decompression Limits and Repetitive Group Designators for No-Decompression Air Dives.
Repetitive Group Designation

Depth
(fsw)

No-Stop
Limit

A

B

C

D

E

10

Unlimited

57

101

158

245

426

*

15

Unlimited

36

60

88

121

163

20

Unlimited

26

43

61

82

25

1102

20

33

47

30

371

17

27

35

232

14

40

163

45

F

G

H

I

J

K

217

297

449

*

106

133

165

205

62

78

97

117

38

50

62

76

23

32

42

52

12

20

27

36

125

11

17

24

50

92

9

15

55

74

8

60

63

70

L

M

N

O

Z

256

330

461

*

140

166

198

236

285

354

469

992

1102

91

107

125

145

167

193

223

260

307

371

63

74

87

100

115

131

148

168

190

215

232

44

53

63

73

84

95

108

121

135

151

163

31

39

46

55

63

72

82

92

102

114

125

21

28

34

41

48

56

63

71

80

89

92

14

19

25

31

37

43

50

56

63

71

74

7

12

17

22

28

33

39

45

51

57

63

48

6

10

14

19

23

28

32

37

42

47

48

80

39

5

9

12

16

20

24

28

32

36

39

90

33

4

7

11

14

17

21

24

28

31

33

100

25

4

6

9

12

15

18

21

25

110

20

3

6

8

11

14

16

19

20

120

15

3

5

7

10

12

15

130

12

2

4

6

9

11

12

140

10

2

4

6

8

10

150

8

3

5

7

8

160

7

3

5

6

7

170

6

4

6

180

6

4

5

190

5

3

5

6

* Highest repetitive group that can be achieved at this depth regardless of bottom time.

CHAPTER 9 — Air Decompression

9-63

Table 9‑8. Residual Nitrogen Time Table for Repetitive Air Dives.
Locate the diver’s repetitive group designation from his previous dive along the diagonal line
above the table. Read horizontally to the interval in which the diver’s surface interval
lies.

ng

up

ive

:10
:52
:53
1:44

:10
:52
:53
1:44
1:45
2:37

:10
:52
:53
1:44
1:45
2:37
2:38
3:29

:10
:52
:53
1:44
1:45
2:37
2:38
3:29
3:30
4:21

Z

O

N

M

L

**
**
**
†
372
245
188
154
131
114
101
83
70
61
54
48
44
40
37
34
32
30
28
26

**
**
**
†
308
216
169
140
120
105
93
77
65
57
50
45
41
37
34
32
30
28
26
25

**
**
**
470
261
191
152
127
109
96
86
71
60
52
47
42
38
35
32
30
28
26
25
23

**
**
**
354
224
169
136
115
99
88
79
65
55
48
43
39
35
32
30
28
26
24
23
22

**
**
**
286
194
149
122
104
90
80
72
59
51
44
40
36
32
30
27
26
24
22
21
20

M
N
O
:10
:52

Dive
Depth
10
15
20
25
30
35
40
45
50
55
60
70
80
90
100
110
120
130
140
150
160
170
180
190

:10
:52
:53
1:44
1:45
2:37
2:38
3:29
3:30
4:21
4:22
5:13

:10
:52
:53
1:44
1:45
2:37
2:38
3:29
3:30
4:21
4:22
5:13
5:14
6:06

:10
:52
:53
1:44
1:45
2:37
2:38
3:29
3:30
4:21
4:22
5:13
5:14
6:06
6:07
6:58

r
te

D

n

eI

c
rfa

E
F

G
H

I
J

K
L

Z

o
Gr

it
et

p

Re

Be

l

va

Su

i
nn

gi

at

of

B
C

Next, read vertically downward to the new repetitive group designation.
Continue downward in this same column to the row that represents
the depth of the repetitive dive. The time given at the intersection
is residual nitrogen time, in minutes, to be applied to the
repetitive dive.
* Dives following surface intervals longer than
this are not repetitive dives. Use actual
bottom times in the Air Decompression
Tables to compute decompression
for such dives.

A

:10
:52
:53
1:44
1:45
2:37
2:38
3:29
3:30
4:21
4:22
5:13
5:14
6:06
6:07
6:58
6:59
7:50

:10
:52
:53
1:44
1:45
2:37
2:38
3:29
3:30
4:21
4:22
5:13
5:14
6:06
6:07
6:58
6:59
7:50
7:51
8:42

:10
:52
:53
1:44
1:45
2:37
2:38
3:29
3:30
4:21
4:22
5:13
5:14
6:06
6:07
6:58
6:59
7:50
7:51
8:42
8:43
9:34

:10
:52
:53
1:44
1:45
2:37
2:38
3:29
3:30
4:21
4:22
5:13
5:14
6:06
6:07
6:58
6:59
7:50
7:51
8:42
8:43
9:34
9:35
10:27

K
J
I
H
G
F
E
Repetitive Group at the End of the Surface Interval
**
**
**
**
**
**
**
**
450
298
462
331
257
206
166
237
198
167
141
118
168
146
126
108
92
132
116
101
88
75
109
97
85
74
64
93
83
73
64
56
81
73
65
57
49
72
65
58
51
44
65
58
52
46
40
54
49
44
39
34
46
42
38
33
29
41
37
33
29
26
36
33
30
26
23
33
30
27
24
21
30
27
24
22
19
27
25
22
20
18
25
23
21
19
16
23
21
19
17
15
22
20
18
16
14
21
19
17
15
14
19
18
16
14
13
12
18
17
15
14
Residual Nitrogen Times (Minutes)

**
218
134
98
77
64
55
48
42
38
35
29
25
22
20
18
17
15
14
13
13
12
11
11

427
164
106
79
63
53
45
40
35
32
29
25
22
19
17
16
14
13
12
11
11
10
10
9

:10
:52
:53
1:44
1:45
2:37
2:38
3:29
3:30
4:21
4:22
5:13
5:14
6:06
6:07
6:58
6:59
7:50
7:51
8:42
8:43
9:34
9:35
10:27
10:28
11:19

:10
:55
:53
1:47
1:45
2:39
2:38
3:31
3:30
4:23
4:22
5:16
5:14
6:08
6:07
7:00
6:59
7:52
7:51
8:44
8:43
9:37
9:35
10:29
10:28
11:21
11:20
12:13

:10
1:16
:56
2:11
1:48
3:03
2:40
3:55
3:32
4:48
4:24
5:40
5:17
6:32
6:09
7:24
7:01
8:16
7:53
9:09
8:45
10:01
9:38
10:53
10:30
11:45
11:22
12:37
12:14
13:30

D

C

B

246
122
83
63
51
43
37
32
29
26
24
20
18
16
14
13
12
11
10
9
9
8
8
8

159
89
62
48
39
33
29
25
23
20
19
16
14
12
11
10
9
9
8
8
7
7
6
6

101
61
44
34
28
24
21
18
17
15
14
12
10
9
8
8
7
6
6
6
5
5
5
5

:10
2:20 *
1:17
3:36 *
2:12
4:31 *
3:04
5:23 *
3:56
6:15 *
4:49
7:08 *
5:41
8:00 *
6:33
8:52 *
7:25
9:44 *
8:17
10:36 *
9:10
11:29 *
10:02
12:21 *
10:54
13:13 *
11:46
14:05 *
12:38
14:58 *
13:31
15:50 *
A

58
37
27
21
18
15
13
12
11
10
9
8
7
6
5
5
5
4
4
4
4
3
3
3

** Residual Nitrogen Time cannot be determined using this table (see paragraph 9-9.1 subparagraph 8 for instructions).
†	Read vertically downward to the 30 fsw repetitive dive depth. Use the corresponding residual nitrogen times to compute the
equivalent single dive time. Decompress using the 30 fsw air decompression table.

9-64

U.S. Navy Diving Manual — Volume 2

Table 9‑9. Air Decompression Table.
(DESCENT RATE 75 FPM—ASCENT RATE 30 FPM)

Bottom Time
(min)

Time
to First
Stop
(M:S)

DECOMPRESSION STOPS (FSW)
Stop times (min) include travel time,
except first air and first O2 stop
Gas Mix

100

90

80

70

60

50

40

30

20

Total
Ascent
Time
(M:S)

Chamber
O2
Periods

Repet
Group

0

Z

0.5

Z

30 FSW
371
380

1:00
0:20

AIR

0

1:00

AIR/O2

0

1:00

AIR

5

6:00

AIR/O2

1

2:00

In-Water Air/O2 Decompression or SurDO2 Recommended -------------------------------------------------------------------------------------420
480
540

0:20
0:20
0:20

AIR

22

23:00

AIR/O2

5

6:00

AIR

42

43:00

AIR/O2

9

10:00

AIR

71

72:00

AIR/O2

14

15:00

0.5

Z

0.5
1

Exceptional Exposure: In-Water Air Decompression ------------- In-Water Air/O2 Decompression or SurDO2 Required ----------600
660
720

0:20
0:20
0:20

AIR

92

93:00

AIR/O2

19

20:00

AIR

120

121:00

AIR/O2

22

23:00

AIR

158

159:00

AIR/O2

27

28:00

1
1
1

35 FSW
232
240

1:10
0:30

AIR

0

1:10

AIR/O2

0

1:10

AIR

4

5:10

AIR/O2

2

3:10

0

Z

0.5

Z

In-Water Air/O2 Decompression or SurDO2 Recommended -------------------------------------------------------------------------------------270
300
330
360

0:30
0:30
0:30
0:30

AIR

28

29:10

AIR/O2

7

8:10

AIR

53

54:10

AIR/O2

13

14:10

AIR

71

72:10

AIR/O2

18

19:10

AIR

88

89:10

AIR/O2

22

23:10

0.5

Z

0.5

Z

1

Z

1

Exceptional Exposure: In-Water Air Decompression ------------- In-Water Air/O2 Decompression or SurDO2 Required ----------420
480
540
600
660
720

0:30
0:30
0:30
0:30
0:30
0:30

AIR

134

135:10

AIR/O2

29

30:10

AIR

173

174:10

AIR/O2

38

44:10

AIR

228

229:10

AIR/O2

45

51:10

AIR

277

278:10

AIR/O2

53

59:10

AIR

314

315:10

AIR/O2

63

69:10

AIR

342

343:10

AIR/O2

71

82:10

CHAPTER 9 — Air Decompression

1.5
1.5
2
2
2.5
3

9-65

Table 9-9. Air Decompression Table (Continued).
(DESCENT RATE 75 FPM—ASCENT RATE 30 FPM)

Bottom Time
(min)

Time
to First
Stop
(M:S)

DECOMPRESSION STOPS (FSW)
Stop times (min) include travel time,
except first air and first O2 stop
Gas Mix

100

90

80

70

60

50

40

30

20

Total
Ascent
Time
(M:S)

Chamber
O2
Periods

Repet
Group

0

O

0.5

O

0.5

Z

40 FSW
163
170
180

1:20
0:40
0:40

AIR

0

1:20

AIR/O2

0

1:20

AIR

6

7:20

AIR/O2

2

3:20

AIR

14

15:20

AIR/O2

5

6:20

In-Water Air/O2 Decompression or SurDO2 Recommended -------------------------------------------------------------------------------------190
200
210

0:40
0:40
0:40

220

0:40

230

0:40

240

0:40

AIR

21

22:20

AIR/O2

7

8:20

AIR

27

28:20

AIR/O2

9

10:20

AIR

39

40:20

AIR/O2

11

12:20

AIR

52

53:20

AIR/O2

12

13:20

AIR

64

65:20

AIR/O2

16

17:20

AIR

75

76:20

AIR/O2

19

20:20

0.5

Z

0.5

Z

0.5

Z

0.5

Z

1

Z

1

Z

Exceptional Exposure: In-Water Air Decompression ------------- In-Water Air/O2 Decompression or SurDO2 Required ----------270

0:40

300

0:40

330

0:40

360
420
480

0:40
0:40
0:40

AIR

101

102:20

AIR/O2

26

27:20

AIR

128

129:20

AIR/O2

33

34:20

AIR

160

161:20

AIR/O2

38

44:20

AIR

184

185:20

AIR/O2

44

50:20

AIR

248

249:20

AIR/O2

56

62:20

AIR

321

322:20

AIR/O2

68

79:20

1

Z

1.5
1.5
2
2.5
2.5

Exceptional Exposure: In-Water Air/02 Decompression ------------- SurDO2 Required------------------------------------------------------540
600
660

0:40
0:40
0:40

AIR

372

373:20

AIR/O2

80

91:20

AIR

410

411:20

AIR/O2

93

104:20

AIR

439

440:20

AIR/O2

103

119:20

3
3.5
4

Exceptional Exposure: SurDO2 ---------------------------------------------------------------------------------------------------------------------------720

9-66

0:40

AIR

461

462:20

AIR/O2

112

128:20

4.5

U.S. Navy Diving Manual — Volume 2

Table 9-9. Air Decompression Table (Continued).
(DESCENT RATE 75 FPM—ASCENT RATE 30 FPM)

Bottom Time
(min)

Time
to First
Stop
(M:S)

DECOMPRESSION STOPS (FSW)
Stop times (min) include travel time,
except first air and first O2 stop
Gas Mix

100

90

80

70

60

50

40

30

20

Total
Ascent
Time
(M:S)

Chamber
O2
Periods

Repet
Group

0

N

0.5

O

0.5

O

45 FSW
125
130
140

1:30
0:50
0:50

AIR

0

1:30

AIR/O2

0

1:30

AIR

2

3:30

AIR/O2

1

2:30

AIR

14

15:30

AIR/O2

5

6:30

In-Water Air/O2 Decompression or SurDO2 Recommended -------------------------------------------------------------------------------------150
160
170

0:50
0:50
0:50

180

0:50

190

0:50

AIR

25

26:30

AIR/O2

8

9:30

AIR

34

35:30

AIR/O2

11

12:30

AIR

41

42:30

AIR/O2

14

15:30

AIR

59

60:30

AIR/O2

17

18:30

AIR

75

76:30

AIR/O2

19

20:30

0.5

Z

0.5

Z

1

Z

1

Z

1

Z

Exceptional Exposure: In-Water Air Decompression ------------- In-Water Air/O2 Decompression or SurDO2 Required ----------200
210

0:50
0:50

220

0:50

230

0:50

240
270

0:50
0:50

300

0:50

330

0:50

360

0:50

AIR

89

90:30

AIR/O2

23

24:30

AIR

101

102:30

AIR/O2

27

28:30

AIR

112

113:30

AIR/O2

30

31:30

AIR

121

122:30

AIR/O2

33

34:30

AIR

130

131:30

AIR/O2

37

43:30

AIR

173

174:30

AIR/O2

45

51:30

AIR

206

207:30

AIR/O2

51

57:30

AIR

243

244:30

AIR/O2

61

67:30

AIR

288

289:30

AIR/O2

69

80:30

1

Z

1

Z

1.5

Z

1.5

Z

1.5

Z

2
2
2.5
3

Exceptional Exposure: In-Water Air/02 Decompression ------------- SurDO2 Required------------------------------------------------------420
480

0:50
0:50

AIR

373

374:30

AIR/O2

84

95:30

AIR

431

432:30

AIR/O2

101

117:30

3.5
4

Exceptional Exposure: SurDO2 ---------------------------------------------------------------------------------------------------------------------------540

0:50

AIR

473

474:30

AIR/O2

117

133:30

CHAPTER 9 — Air Decompression

4.5

9-67

Table 9-9. Air Decompression Table (Continued).
(DESCENT RATE 75 FPM—ASCENT RATE 30 FPM)

Bottom Time
(min)

Time
to First
Stop
(M:S)

DECOMPRESSION STOPS (FSW)
Stop times (min) include travel time,
except first air and first O2 stop
Gas Mix

100

90

80

70

60

50

40

30

20

Total
Ascent
Time
(M:S)

Chamber
O2
Periods

Repet
Group

0

M

0.5

M

0.5

N

0.5

O

50 FSW
92
95
100
110

1:40
1:00
1:00
1:00

AIR

0

1:40

AIR/O2

0

1:40

AIR

2

3:40

AIR/O2

1

2:40

AIR

4

5:40

AIR/O2

2

3:40

AIR

8

9:40

AIR/O2

4

5:40

In-Water Air/O2 Decompression or SurDO2 Recommended -------------------------------------------------------------------------------------120
130
140
150
160

1:00
1:00
1:00
1:00
1:00

AIR

21

22:40

AIR/O2

7

8:40

AIR

34

35:40

AIR/O2

12

13:40

AIR

45

46:40

AIR/O2

16

17:40

AIR

56

57:40

AIR/O2

19

20:40

AIR

78

79:40

AIR/O2

23

24:40

0.5

O

0.5

Z

1

Z

1

Z

1

Z

Exceptional Exposure: In-Water Air Decompression ------------- In-Water Air/O2 Decompression or SurDO2 Required ----------170
180
190
200
210
220
230
240
270
300

1:00
1:00
1:00
1:00
1:00
1:00
1:00
1:00
1:00
1:00

AIR

96

97:40

AIR/O2

26

27:40

AIR

111

112:40

AIR/O2

30

31:40

AIR

125

126:40

AIR/O2

35

36:40

AIR

136

137:40

AIR/O2

39

45:40

AIR

147

148:40

AIR/O2

43

49:40

AIR

166

167:40

AIR/O2

47

53:40

AIR

183

184:40

AIR/O2

50

56:40

AIR

198

199:40

AIR/O2

53

59:40

AIR

236

237:40

AIR/O2

62

68:40

AIR

285

286:40

AIR/O2

74

85:40

1

Z

1.5

Z

1.5

Z

1.5

Z

2
2
2
2
2.5
3

Exceptional Exposure: In-Water Air/O2 Decompression ------------- SurDO2 Required------------------------------------------------------330
360

1:00
1:00

AIR

345

346:40

AIR/O2

83

94:40

AIR

393

394:40

AIR/O2

92

103:40

3.5
3.5

Exceptional Exposure: SurDO2 ---------------------------------------------------------------------------------------------------------------------------420

9-68

1:00

AIR

464

465:40

AIR/O2

113

129:40

4.5

U.S. Navy Diving Manual — Volume 2

Table 9-9. Air Decompression Table (Continued).
(DESCENT RATE 75 FPM—ASCENT RATE 30 FPM)

Bottom Time
(min)

Time
to First
Stop
(M:S)

DECOMPRESSION STOPS (FSW)
Stop times (min) include travel time,
except first air and first O2 stop
Gas Mix

100

90

80

70

60

50

40

30

20

Total
Ascent
Time
(M:S)

Chamber
O2
Periods

Repet
Group

0

L

0.5

L

0.5

M

0.5

N

55 FSW
74
75
80
90

1:50
1:10
1:10
1:10

AIR

0

1:50

AIR/O2

0

1:50

AIR

1

2:50

AIR/O2

1

2:50

AIR

4

5:50

AIR/O2

2

3:50

AIR

10

11:50

AIR/O2

5

6:50

In-Water Air/O2 Decompression or SurDO2 Recommended -------------------------------------------------------------------------------------100
110
120
130
140

1:10
1:10
1:10
1:10
1:10

AIR

17

18:50

AIR/O2

8

9:50

AIR

34

35:50

AIR/O2

12

13:50

AIR

48

49:50

AIR/O2

17

18:50

AIR

59

60:50

AIR/O2

22

23:50

AIR

84

85:50

AIR/O2

26

27:50

0.5

O

0.5

O

1

Z

1

Z

1

Z

Exceptional Exposure: In-Water Air Decompression ------------- In-Water Air/O2 Decompression or SurDO2 Required ----------150
160
170
180
190
200
210
220
230
240

1:10
1:10
1:10
1:10
1:10
1:10
1:10
1:10
1:10
1:10

AIR

105

106:50

AIR/O2

30

31:50

AIR

123

124:50

AIR/O2

34

35:50

AIR

138

139:50

AIR/O2

40

46:50

AIR

151

152:50

AIR/O2

45

51:50

AIR

169

170:50

AIR/O2

50

56:50

AIR

190

191:50

AIR/O2

54

60:50

AIR

208

209:50

AIR/O2

58

64:50

AIR

224

225:50

AIR/O2

62

68:50

AIR

239

240:50

AIR/O2

66

77:50

AIR

254

255:50

AIR/O2

69

80:50

1.5

Z

1.5

Z

1.5

Z

2

Z

2
2
2.5
2.5
2.5
3

Exceptional Exposure: In-Water Air/02 Decompression ------------- SurDO2 Required------------------------------------------------------270
300
330

1:10
1:10
1:10

AIR

313

314:50

AIR/O2

83

94:50

AIR

380

381:50

AIR/O2

94

105:50

AIR

432

433:50

AIR/O2

106

122:50

3.5
3.5
4

Exceptional Exposure: SurDO2 ---------------------------------------------------------------------------------------------------------------------------360

1:10

AIR

474

475:50

AIR/O2

118

134:50

CHAPTER 9 — Air Decompression

4.5

9-69

Table 9-9. Air Decompression Table (Continued).
(DESCENT RATE 75 FPM—ASCENT RATE 30 FPM)

Bottom Time
(min)

Time
to First
Stop
(M:S)

DECOMPRESSION STOPS (FSW)
Stop times (min) include travel time,
except first air and first O2 stop
Gas Mix

100

90

80

70

60

50

40

30

20

Total
Ascent
Time
(M:S)

Chamber
O2
Periods

Repet
Group

0

K

0.5

L

0.5

L

0.5

N

60 FSW
63
65
70
80

2:00
1:20
1:20
1:20

AIR

0

2:00

AIR/O2

0

2:00

AIR

2

4:00

AIR/O2

1

3:00

AIR

7

9:00

AIR/O2

4

6:00

AIR

14

16:00

AIR/O2

7

9:00

In-Water Air/O2 Decompression or SurDO2 Recommended -------------------------------------------------------------------------------------90
100
110
120

1:20
1:20
1:20
1:20

AIR

23

25:00

AIR/O2

10

12:00

AIR

42

44:00

AIR/O2

15

17:00

AIR

57

59:00

AIR/O2

21

23:00

AIR

75

77:00

AIR/O2

26

28:00

0.5

O

1

Z

1

Z

1

Z

Exceptional Exposure: In-Water Air Decompression ------------- In-Water Air/O2 Decompression or SurDO2 Required ----------130
140
150
160
170
180
190
200
210
220

1:20
1:20
1:20
1:20
1:20
1:20
1:20
1:20
1:20
1:20

AIR

102

104:00

AIR/O2

31

33:00

AIR

124

126:00

AIR/O2

35

37:00

AIR

143

145:00

AIR/O2

41

48:00

AIR

158

160:00

AIR/O2

48

55:00

AIR

178

180:00

AIR/O2

53

60:00

AIR

201

203:00

AIR/O2

59

66:00

AIR

222

224:00

AIR/O2

64

71:00

AIR

240

242:00

AIR/O2

68

80:00

AIR

256

258:00

AIR/O2

73

85:00

AIR

278

280:00

AIR/O2

77

89:00

1.5

Z

1.5

Z

2

Z

2

Z

2
2.5
2.5
2.5
3
3

Exceptional Exposure: In-Water Air/02 Decompression ------------- SurDO2 Required------------------------------------------------------230
240
270

1:20
1:20
1:20

AIR

300

302:00

AIR/O2

82

94:00

AIR

321

323:00

AIR/O2

88

100:00

AIR

398

400:00

AIR/O2

102

119:00

3.5
3.5
4

Exceptional Exposure: SurDO2 ---------------------------------------------------------------------------------------------------------------------------300

9-70

1:20

AIR

456

458:00

AIR/O2

115

132:00

4.5

U.S. Navy Diving Manual — Volume 2

Table 9-9. Air Decompression Table (Continued).
(DESCENT RATE 75 FPM—ASCENT RATE 30 FPM)

Bottom Time
(min)

Time
to First
Stop
(M:S)

DECOMPRESSION STOPS (FSW)
Stop times (min) include travel time,
except first air and first O2 stop
Gas Mix

100

90

80

70

60

50

40

30

20

Total
Ascent
Time
(M:S)

Chamber
O2
Periods

Repet
Group

0

K

0.5

K

0.5

L

0.5

M

70 FSW
48

2:20

50

1:40

55

1:40

60

1:40

AIR

0

2:20

AIR/O2

0

2:20

AIR

2

4:20

AIR/O2

1

3:20

AIR

9

11:20

AIR/O2

5

7:20

AIR

14

16:20

AIR/O2

8

10:20

In-Water Air/O2 Decompression or SurDO2 Recommended -------------------------------------------------------------------------------------70

1:40

80

1:40

90

1:40

AIR

24

26:20

AIR/O2

13

15:20

AIR

44

46:20

AIR/O2

17

19:20

AIR

64

66:20

AIR/O2

24

26:20

0.5

N

1

O

1

Z

Exceptional Exposure: In-Water Air Decompression ------------- In-Water Air/O2 Decompression or SurDO2 Required ----------100
110
120
130
140
150
160

1:40
1:40
1:40
1:40
1:40
1:40
1:20

AIR

88

90:20

AIR/O2

31

33:20

AIR

120

122:20

AIR/O2

38

45:20

AIR

145

147:20

AIR/O2

44

51:20

AIR

167

169:20

AIR/O2

51

58:20

AIR

189

191:20

AIR/O2

59

66:20

AIR

219

221:20

AIR/O2

66

78:20

AIR

1

244

247:00

AIR/O2

1

72

85:00

1.5

Z

1.5

Z

2

Z

2

Z

2.5
2.5
3

Exceptional Exposure: In-Water Air/02 Decompression ------------- SurDO2 Required------------------------------------------------------170
180
190

1:20
1:20
1:20

200

1:20

210

1:20

AIR

2

265

269:00

AIR/O2

1

78

91:00

AIR

4

289

295:00

AIR/O2

2

83

97:00

AIR

5

316

323:00

AIR/O2

3

88

103:00

AIR

9

345

356:00

AIR/O2

5

93

115:00

AIR

13

378

393:00

AIR/O2

7

98

122:00

3
3.5
3.5
4
4

Exceptional Exposure: SurDO2 ---------------------------------------------------------------------------------------------------------------------------240

1:20

AIR

25

454

481:00

AIR/O2

13

110

140:00

CHAPTER 9 — Air Decompression

5

9-71

Table 9-9. Air Decompression Table (Continued).
(DESCENT RATE 75 FPM—ASCENT RATE 30 FPM)

Bottom Time
(min)

Time
to First
Stop
(M:S)

DECOMPRESSION STOPS (FSW)
Stop times (min) include travel time,
except first air and first O2 stop
Gas Mix

100

90

80

70

60

50

40

30

20

Total
Ascent
Time
(M:S)

Chamber
O2
Periods

Repet
Group

0

J

0.5

J

0.5

K

80 FSW
39

2:40

40

2:00

45

2:00

AIR

0

2:40

AIR/O2

0

2:40

AIR

1

3:40

AIR/O2

1

3:40

AIR

10

12:40

AIR/O2

5

7:40

In-Water Air/O2 Decompression or SurDO2 Recommended -------------------------------------------------------------------------------------50
55

2:00
2:00

60

2:00

70

2:00

80

2:00

AIR

17

19:40

AIR/O2

9

11:40

AIR

24

26:40

AIR/O2

13

15:40

AIR

30

32:40

AIR/O2

16

18:40

AIR

54

56:40

AIR/O2

22

24:40

AIR

77

79:40

AIR/O2

30

32:40

0.5

M

0.5

M

1

N

1

O

1.5

Z

Exceptional Exposure: In-Water Air Decompression ------------- In-Water Air/O2 Decompression or SurDO2 Required ----------90
100
110
120
130

2:00
1:40
1:40
1:40
1:40

AIR

114

116:40

AIR/O2

39

46:40

AIR

1

147

150:20

AIR/O2

1

46

54:20

AIR

6

171

179:20

AIR/O2

3

51

61:20

AIR

10

200

212:20

AIR/O2

5

59

71:20

AIR

14

232

248:20

AIR/O2

7

67

86:20

1.5

Z

2

Z

2

Z

2.5
3

Exceptional Exposure: In-Water Air/02 Decompression ------------- SurDO2 Required------------------------------------------------------140
150
160
170

1:40
1:40
1:40
1:40

AIR

17

258

277:20

AIR/O2

9

73

94:20

AIR

19

285

306:20

AIR/O2

10

80

102:20

AIR

21

318

341:20

AIR/O2

11

86

114:20

AIR

27

354

383:20

AIR/O2

14

90

121:20

3.5
3.5
4
4

Exceptional Exposure: SurDO2 ---------------------------------------------------------------------------------------------------------------------------180
210

9-72

1:40
1:40

AIR

33

391

426:20

AIR/O2

17

96

130:20

AIR

51

473

526:20

AIR/O2

26

110

158:20

4.5
5

U.S. Navy Diving Manual — Volume 2

Table 9-9. Air Decompression Table (Continued).
(DESCENT RATE 75 FPM—ASCENT RATE 30 FPM)

Bottom Time
(min)

Time
to First
Stop
(M:S)

DECOMPRESSION STOPS (FSW)
Stop times (min) include travel time,
except first air and first O2 stop
Gas Mix

100

90

80

70

60

50

40

30

20

Total
Ascent
Time
(M:S)

Chamber
O2
Periods

Repet
Group

0

J

0.5

J

0.5

L

90 FSW
33

3:00

35

2:20

40

2:20

AIR

0

3:00

AIR/O2

0

3:00

AIR

4

7:00

AIR/O2

2

5:00

AIR

14

17:00

AIR/O2

7

10:00

In-Water Air/O2 Decompression or SurDO2 Recommended -------------------------------------------------------------------------------------45
50

2:20
2:20

55

2:20

60

2:20

70

2:20

AIR

23

26:00

AIR/O2

12

15:00

AIR

31

34:00

AIR/O2

17

20:00

AIR

39

42:00

AIR/O2

21

24:00

AIR

56

59:00

AIR/O2

24

27:00

AIR

83

86:00

AIR/O2

32

35:00

0.5

M

1

N

1

O

1

O

1.5

Z

Exceptional Exposure: In-Water Air Decompression ------------- In-Water Air/O2 Decompression or SurDO2 Required ----------80
90
100
110

2:00
2:00
2:00
2:00

AIR

5

125

132:40

AIR/O2

3

40

50:40

AIR

13

158

173:40

AIR/O2

7

46

60:40

AIR

19

185

206:40

AIR/O2

10

53

70:40

AIR

25

224

251:40

AIR/O2

13

61

86:40

2

Z

2

Z

2.5
3

Exceptional Exposure: In-Water Air/02 Decompression ------------- SurDO2 Required------------------------------------------------------120
130
140

1:40
1:40
1:40

AIR

2

28

256

288:20

AIR/O2

2

14

70

98:40

AIR

5

28

291

326:20

AIR/O2

5

14

79

110:40

AIR

8

28

330

368:20

AIR/O2

8

14

87

126:40

3.5
3.5
4

Exceptional Exposure: SurDO2 ---------------------------------------------------------------------------------------------------------------------------150
160
170
180
240

1:40
1:40
1:40
1:40
1:40

AIR

11

34

378

425:20

AIR/O2

11

17

94

139:40

AIR

13

40

418

473:20

AIR/O2

13

20

101

151:40

AIR

15

45

451

513:20

AIR/O2

15

23

106

166:40

AIR

16

51

479

548:20

AIR/O2

16

26

112

176:40

AIR

42

68

592

704:20

AIR/O2

42

34

159

267:40

CHAPTER 9 — Air Decompression

4.5
4.5
5
5.5
7.5

9-73

Table 9-9. Air Decompression Table (Continued).
(DESCENT RATE 75 FPM—ASCENT RATE 30 FPM)

Bottom Time
(min)

Time
to First
Stop
(M:S)

DECOMPRESSION STOPS (FSW)
Stop times (min) include travel time,
except first air and first O2 stop
Gas Mix

100

90

80

70

60

50

40

30

20

Total
Ascent
Time
(M:S)

Chamber
O2
Periods

Repet
Group

0

H

0.5

J

0.5

L

100 FSW
25

3:20

30

2:40

35

2:40

AIR

0

3:20

AIR/O2

0

3:20

AIR

3

6:20

AIR/O2

2

5:20

AIR

15

18:20

AIR/O2

8

11:20

In-Water Air/O2 Decompression or SurDO2 Recommended -------------------------------------------------------------------------------------40
45

2:40
2:40

50

2:40

55

2:40

60

2:40

AIR

26

29:20

AIR/O2

14

17:20

AIR

36

39:20

AIR/O2

19

22:20

AIR

47

50:20

AIR/O2

24

27:20

AIR

65

68:20

AIR/O2

28

31:20

AIR

81

84:20

AIR/O2

33

36:20

1

M

1

N

1

O

1.5

Z

1.5

Z

Exceptional Exposure: In-Water Air Decompression ------------- In-Water Air/O2 Decompression or SurDO2 Required ----------70
80
90

2:20
2:20
2:00

AIR

11

124

138:00

AIR/O2

6

39

53:00

AIR

21

160

184:00

AIR/O2

11

45

64:00

AIR

2

28

196

228:40

AIR/O2

2

14

53

82:00

2

Z

2.5

Z

2.5

Exceptional Exposure: In-Water Air/02 Decompression ------------- SurDO2 Required------------------------------------------------------100
110
120

2:00
2:00
2:00

AIR

9

28

241

280:40

AIR/O2

9

14

66

102:00

AIR

14

28

278

322:40

AIR/O2

14

14

76

117:00

AIR

19

28

324

373:40

AIR/O2

19

14

85

136:00

3
3.5
4

Exceptional Exposure: SurDO2 ---------------------------------------------------------------------------------------------------------------------------150

9-74

1:40

AIR

3

26

46

461

538:20

AIR/O2

3

26

23

109

183:40

5

U.S. Navy Diving Manual — Volume 2

Table 9-9. Air Decompression Table (Continued).
(DESCENT RATE 75 FPM—ASCENT RATE 30 FPM)

Bottom Time
(min)

Time
to First
Stop
(M:S)

DECOMPRESSION STOPS (FSW)
Stop times (min) include travel time,
except first air and first O2 stop
Gas Mix

100

90

80

70

60

50

40

30

20

Total
Ascent
Time
(M:S)

Chamber
O2
Periods

Repet
Group

0

H

0.5

I

0.5

K

110 FSW
20

3:40

25

3:00

30

3:00

AIR

0

3:40

AIR/O2

0

3:40

AIR

5

8:40

AIR/O2

3

6:40

AIR

14

17:40

AIR/O2

7

10:40

In-Water Air/O2 Decompression or SurDO2 Recommended -------------------------------------------------------------------------------------35
40

3:00
3:00

45

3:00

50

3:00

AIR

27

30:40

AIR/O2

14

17:40

AIR

39

42:40

AIR/O2

20

23:40

AIR

50

53:40

AIR/O2

26

29:40

AIR

71

74:40

AIR/O2

32

35:40

1

M

1

N

1

O

1.5

Z

Exceptional Exposure: In-Water Air Decompression ------------- In-Water Air/O2 Decompression or SurDO2 Required ----------55
60
70

2:40
2:40
2:40

AIR

5

85

93:20

AIR/O2

3

33

44:20

AIR

13

111

127:20

AIR/O2

7

36

51:20

AIR

26

155

184:20

AIR/O2

14

42

64:20

1.5

Z

2

Z

2.5

Z

Exceptional Exposure: In-Water Air/02 Decompression ------------- SurDO2 Required------------------------------------------------------80
90
100
110

2:20
2:20
2:20
2:00

AIR

9

28

200

240:00

AIR/O2

9

14

54

90:20

AIR

18

28

249

298:00

AIR/O2

18

14

68

113:20

AIR

25

28

295

351:00

AIR/O2

25

14

79

131:20

AIR

5

26

28

353

414:40

AIR/O2

5

26

14

91

154:00

2.5
3.5
3.5
4

Exceptional Exposure: SurDO2 ---------------------------------------------------------------------------------------------------------------------------120
180

2:00
1:40

AIR

10

26

35

413

486:40

AIR/O2

10

26

18

101

173:00

AIR

3

23

47

68

593

736:20

AIR/O2

3

23

47

34

159

298:40

CHAPTER 9 — Air Decompression

4.5
7.5

9-75

Table 9-9. Air Decompression Table (Continued).
(DESCENT RATE 75 FPM—ASCENT RATE 30 FPM)

Bottom Time
(min)

Time
to First
Stop
(M:S)

DECOMPRESSION STOPS (FSW)
Stop times (min) include travel time,
except first air and first O2 stop
Gas Mix

100

90

80

70

60

50

40

30

20

Total
Ascent
Time
(M:S)

Chamber
O2
Periods

Repet
Group

0

F

0.5

H

0.5

J

120 FSW
15

4:00

20

3:20

25

3:20

AIR

0

4:00

AIR/O2

0

4:00

AIR

4

8:00

AIR/O2

2

6:00

AIR

9

13:00

AIR/O2

5

9:00

In-Water Air/O2 Decompression or SurDO2 Recommended -------------------------------------------------------------------------------------30
35

3:20
3:20

40

3:00

45

3:00

AIR

24

28:00

AIR/O2

13

17:00

AIR

38

42:00

AIR/O2

20

24:00

AIR

2

49

54:40

AIR/O2

1

26

30:40

AIR

3

71

77:40

AIR/O2

2

31

36:40

0.5

L

1

N

1

O

1.5

Z

Exceptional Exposure: In-Water Air Decompression ------------- In-Water Air/O2 Decompression or SurDO2 Required ----------50
55
60
70

3:00
3:00
3:00
2:40

AIR

10

85

98:40

AIR/O2

5

33

46:40

AIR

19

116

138:40

AIR/O2

10

35

53:40

AIR

27

142

172:40

AIR/O2

14

39

61:40

AIR

13

28

190

234:20

AIR/O2

13

14

51

86:40

1.5

Z

2

Z

2

Z

2.5

Exceptional Exposure: In-Water Air/02 Decompression ------------- SurDO2 Required------------------------------------------------------80
90
100

2:40
2:20
2:20

AIR

24

28

246

301:20

AIR/O2

24

14

67

118:40

AIR

7

26

28

303

367:00

AIR/O2

7

26

14

80

140:20

AIR

15

25

28

372

443:00

AIR/O2

15

25

14

95

167:20

3
3.5
4

Exceptional Exposure: SurDO2 ---------------------------------------------------------------------------------------------------------------------------110
120

9-76

2:20
2:00

AIR

21

25

38

433

520:00

AIR/O2

21

25

19

105

188:20

AIR

3

23

25

47

480

580:40

AIR/O2

3

23

25

24

113

211:00

5
5.5

U.S. Navy Diving Manual — Volume 2

Table 9-9. Air Decompression Table (Continued).
(DESCENT RATE 75 FPM—ASCENT RATE 30 FPM)

Bottom Time
(min)

Time
to First
Stop
(M:S)

DECOMPRESSION STOPS (FSW)
Stop times (min) include travel time,
except first air and first O2 stop
Gas Mix

100

90

80

70

60

50

40

30

20

Total
Ascent
Time
(M:S)

Chamber
O2
Periods

Repet
Group

0

F

0.5

G

0.5

I

130 FSW
12

4:20

15

3:40

20

3:40

AIR

0

4:20

AIR/O2

0

4:20

AIR

3

7:20

AIR/O2

2

6:20

AIR

8

12:20

AIR/O2

5

9:20

In-Water Air/O2 Decompression or SurDO2 Recommended -------------------------------------------------------------------------------------25
30

3:40
3:20

35

3:20

40

3:20

AIR

17

21:20

AIR/O2

9

13:20

AIR

2

32

38:00

AIR/O2

1

17

22:00

AIR

5

44

53:00

AIR/O2

3

23

30:00

AIR

6

66

76:00

AIR/O2

3

30

37:00

0.5

K

1

M

1

O

1.5

Z

Exceptional Exposure: In-Water Air Decompression ------------- In-Water Air/O2 Decompression or SurDO2 Required ----------45
50
55
60

3:00
3:00
3:00
3:00

AIR

1

11

84

99:40

AIR/O2

1

6

33

49:00

AIR

2

20

118

143:40

AIR/O2

2

10

36

57:00

AIR

4

28

146

181:40

AIR/O2

4

14

40

67:00

AIR

12

28

170

213:40

AIR/O2

12

14

46

81:00

1.5

Z

2

Z

2

Z

2.5

Z

Exceptional Exposure: In-Water Air/02 Decompression ------------- SurDO2 Required------------------------------------------------------70
80
90

2:40
2:40
2:40

AIR

1

26

28

235

293:20

AIR/O2

1

26

14

63

117:40

AIR

12

26

28

297

366:20

AIR/O2

12

26

14

79

144:40

AIR

22

25

28

375

453:20

AIR/O2

22

25

14

95

174:40

3
3.5
4

Exceptional Exposure: SurDO2 ---------------------------------------------------------------------------------------------------------------------------100
120
180

2:20
2:20
2:00

AIR

6

23

26

38

444

540:00

AIR/O2

6

23

26

20

106

204:20

AIR

17

24

27

57

534

662:00

AIR/O2

17

24

27

29

130

255:20

AIR

13

21

45

57

94

658

890:40

AIR/O2

13

21

45

57

46

198

418:00

CHAPTER 9 — Air Decompression

5
6
9

9-77

Table 9-9. Air Decompression Table (Continued).
(DESCENT RATE 75 FPM—ASCENT RATE 30 FPM)

Bottom Time
(min)

Time
to First
Stop
(M:S)

DECOMPRESSION STOPS (FSW)
Stop times (min) include travel time,
except first air and first O2 stop
Gas Mix

100

90

80

70

60

50

40

30

20

Total
Ascent
Time
(M:S)

Chamber
O2
Periods

Repet
Group

0

E

0.5

H

0.5

J

140 FSW
10

4:40

15

4:00

20

4:00

AIR

0

4:40

AIR/O2

0

4:40

AIR

5

9:40

AIR/O2

3

7:40

AIR

13

17:40

AIR/O2

7

11:40

In-Water Air/O2 Decompression or SurDO2 Recommended -------------------------------------------------------------------------------------25
30
35

3:40
3:40
3:20

AIR

3

24

31:20

AIR/O2

2

12

18:20

AIR

7

37

48:20

AIR/O2

4

19

27:20

AIR

2

7

58

71:00

AIR/O2

2

4

26

36:20

1

L

1

N

1.5

O

Exceptional Exposure: In-Water Air Decompression ------------- In-Water Air/O2 Decompression or SurDO2 Required ----------40
45
50
55

3:20
3:20
3:20
3:00

AIR

4

7

82

97:00

AIR/O2

4

4

33

50:20

AIR

5

18

114

141:00

AIR/O2

5

9

36

59:20

AIR

8

27

145

184:00

AIR/O2

8

14

39

70:20

AIR

1

15

29

171

219:40

AIR/O2

1

15

15

45

85:00

1.5

Z

2

Z

2

Z

2.5

Z

Exceptional Exposure: In-Water Air/02 Decompression ------------- SurDO2 Required------------------------------------------------------60
70
80

3:00
3:00
2:40

AIR

2

23

28

209

265:40

AIR/O2

2

23

14

56

109:00

AIR

14

25

29

276

347:40

AIR/O2

14

25

15

74

142:00

AIR

2

24

25

29

362

445:20

AIR/O2

2

24

25

15

91

175:40

3
3.5
4

Exceptional Exposure: SurDO2 ---------------------------------------------------------------------------------------------------------------------------90

9-78

2:40

AIR

12

23

26

38

443

545:20

AIR/O2

12

23

26

19

107

210:40

5

U.S. Navy Diving Manual — Volume 2

Table 9-9. Air Decompression Table (Continued).
(DESCENT RATE 75 FPM—ASCENT RATE 30 FPM)

Bottom Time
(min)

Time
to First
Stop
(M:S)

DECOMPRESSION STOPS (FSW)
Stop times (min) include travel time,
except first air and first O2 stop
Gas Mix

100

90

80

70

60

50

40

30

20

Total
Ascent
Time
(M:S)

Chamber
O2
Periods

Repet
Group

0

E

0.5

F

0.5

H

150 FSW
8

5:00

10

4:20

15

4:20

AIR

0

5:00

AIR/O2

0

5:00

AIR

2

7:00

AIR/O2

1

6:00

AIR

8

13:00

AIR/O2

5

10:00

In-Water Air/O2 Decompression or SurDO2 Recommended -------------------------------------------------------------------------------------20
25
30

4:00
4:00
3:40

AIR

2

15

21:40

AIR/O2

1

8

13:40

AIR

7

29

40:40

AIR/O2

4

14

22:40

AIR

4

7

45

60:20

AIR/O2

4

4

22

34:40

0.5

K

1

M

1.5

O

Exceptional Exposure: In-Water Air Decompression ------------- In-Water Air/O2 Decompression or SurDO2 Required ----------35
40
45
50

3:40
3:20
3:20
3:20

AIR

6

7

74

91:20

AIR/O2

6

4

30

44:40

AIR

2

6

14

106

132:00

AIR/O2

2

6

7

35

59:20

AIR

3

8

24

142

181:00

AIR/O2

3

8

12

40

72:20

AIR

4

14

28

170

220:00

AIR/O2

4

14

14

46

87:20

1.5

Z

2

Z

2

Z

2.5

Z

Exceptional Exposure: In-Water Air/02 Decompression ------------- SurDO2 Required------------------------------------------------------55
60
70

3:20
3:20
3:00

AIR

7

21

28

212

272:00

AIR/O2

7

21

14

57

113:20

AIR

11

26

28

248

317:00

AIR/O2

11

26

14

67

132:20

AIR

3

24

25

28

330

413:40

AIR/O2

3

24

25

14

85

170:00

3
3
4

Exceptional Exposure: SurDO2 ---------------------------------------------------------------------------------------------------------------------------80
90
120
180

3:00
2:40
2:20
2:00

AIR

15

23

26

35

430

532:40

AIR/O2

15

23

26

18

104

205:00

AIR

3

22

23

26

47

496

620:20

AIR/O2

3

22

23

26

24

118

239:40

AIR

3

20

22

23

50

75

608

804:00

AIR/O2

3

20

22

23

50

37

168

356:20

AIR

2

19

20

42

48

79

121

694

1027:40

AIR/O2

2

19

20

42

48

79

58

222

538:00

CHAPTER 9 — Air Decompression

4.5
5.5
8
10.5

9-79

Table 9-9. Air Decompression Table (Continued).
(DESCENT RATE 75 FPM—ASCENT RATE 30 FPM)

Bottom Time
(min)

Time
to First
Stop
(M:S)

DECOMPRESSION STOPS (FSW)
Stop times (min) include travel time,
except first air and first O2 stop
Gas Mix

100

90

80

70

60

50

40

30

20

Total
Ascent
Time
(M:S)

Chamber
O2
Periods

Repet
Group

0

E

0.5

F

0.5

I

160 FSW
7

5:20

10

4:40

15

4:20

AIR

0

5:20

AIR/O2

0

5:20

AIR

4

9:20

AIR/O2

2

7:20

AIR

2

10

17:00

AIR/O2

1

6

12:00

In-Water Air/O2 Decompression or SurDO2 Recommended -------------------------------------------------------------------------------------20
25
30

4:00
4:00
3:40

AIR

1

4

19

28:40

AIR/O2

1

2

10

18:00

AIR

4

7

35

50:40

AIR/O2

4

4

17

30:00

AIR

2

6

7

62

81:20

AIR/O2

2

6

4

26

42:40

0.5

L

1

N

1.5

Z

Exceptional Exposure: In-Water Air Decompression ------------- In-Water Air/O2 Decompression or SurDO2 Required ----------35
40
45

3:40
3:40
3:20

AIR

4

6

8

89

111:20

AIR/O2

4

6

4

34

57:40

AIR

6

6

21

134

171:20

AIR/O2

6

6

11

38

70:40

AIR

2

5

11

28

166

216:00

AIR/O2

2

5

11

14

45

86:20

1.5

Z

2

Z

2.5

Z

Exceptional Exposure: In-Water Air/02 Decompression ------------- SurDO2 Required------------------------------------------------------50
55
60

3:20
3:20
3:20

AIR

2

8

19

28

207

268:00

AIR/O2

2

8

19

15

55

113:20

AIR

3

11

26

28

248

320:00

AIR/O2

3

11

26

14

67

135:20

AIR

6

17

25

29

291

372:00

AIR/O2

6

17

25

15

77

154:20

3
3
3.5

Exceptional Exposure: SurDO2 ---------------------------------------------------------------------------------------------------------------------------70

3:20

80

3:00

AIR

15

AIR/O2

9-80

23

26

29

399

496:00

15

23

26

15

99

197:20

AIR

6

21

24

25

44

482

605:40

AIR/O2

6

21

24

25

23

114

237:00

4.5
5.5

U.S. Navy Diving Manual — Volume 2

Table 9-9. Air Decompression Table (Continued).
(DESCENT RATE 75 FPM—ASCENT RATE 30 FPM)

Bottom Time
(min)

Time
to First
Stop
(M:S)

DECOMPRESSION STOPS (FSW)
Stop times (min) include travel time,
except first air and first O2 stop
Gas Mix

100

90

80

70

60

50

40

30

20

Total
Ascent
Time
(M:S)

Chamber
O2
Periods

Repet
Group

0

D

0.5

G

170 FSW
6
10

5:40
5:00

AIR

0

5:40

AIR/O2

0

5:40

AIR

6

11:40

AIR/O2

3

8:40

In-Water Air/O2 Decompression or SurDO2 Recommended -------------------------------------------------------------------------------------15
20
25

4:40
4:20
4:00

AIR

3

13

21:20

AIR/O2

2

6

13:20

AIR

3

6

24

38:00

AIR/O2

3

3

12

23:20

AIR

1

7

7

41

60:40

AIR/O2

1

7

4

20

37:00

0.5

J

1

M

1

O

Exceptional Exposure: In-Water Air Decompression ------------- In-Water Air/O2 Decompression or SurDO2 Required ----------30
35
40

4:00
3:40
3:40

AIR

5

7

7

77

100:40

AIR/O2

5

7

3

30

50:00

AIR

2

6

6

15

120

153:20

AIR/O2

2

6

6

8

37

68:40

AIR

4

6

9

25

158

206:20

AIR/O2

4

6

9

12

44

84:40

1.5

Z

2

Z

2.5

Z

Exceptional Exposure: In-Water Air/02 Decompression ------------- SurDO2 Required------------------------------------------------------45

3:40

50

3:20

AIR

5

AIR/O2

55
60

3:20
3:20

7

16

28

197

257:20
109:40

5

7

16

14

53

AIR

1

5

11

23

28

244

316:00

AIR/O2

1

5

11

23

14

66

134:20

AIR

2

7

16

26

28

289

372:00

AIR/O2

2

7

16

26

14

77

156:20

AIR

2

11

21

26

28

344

436:00

AIR/O2

2

11

21

26

14

88

181:20

2.5

Z

3
3.5
4

Exceptional Exposure: SurDO2 ---------------------------------------------------------------------------------------------------------------------------70

3:20

80

3:20

90
120
180

3:00
2:40
2:20

AIR

7

19

24

25

39

454

572:00

AIR/O2

7

19

24

25

20

109

228:20

AIR

17

22

23

26

53

525

670:00

AIR/O2

17

22

23

26

27

128

267:20

AIR

8

19

22

23

37

66

574

752:40

AIR/O2

8

19

22

23

37

33

148

319:00

AIR

9

19

20

22

42

60

94

659

928:20

AIR/O2

9

19

20

22

42

60

46

198

454:40

AIR

10

18

19

40

43

70

97

156

703

1159:00

AIR/O2

10

18

19

40

43

70

97

74

229

648:00

CHAPTER 9 — Air Decompression

5
6
7
9
11.5

9-81

Table 9-9. Air Decompression Table (Continued).
(DESCENT RATE 75 FPM—ASCENT RATE 30 FPM)

Bottom Time
(min)

Time
to First
Stop
(M:S)

DECOMPRESSION STOPS (FSW)
Stop times (min) include travel time,
except first air and first O2 stop
Gas Mix

100

90

80

70

60

50

40

30

20

Total
Ascent
Time
(M:S)

Chamber
O2
Periods

Repet
Group

0

E

0.5

G

180 FSW
6
10

6:00
5:20

AIR

0

6:00

AIR/O2

0

6:00

AIR

8

14:00

AIR/O2

4

10:00

In-Water Air/O2 Decompression or SurDO2 Recommended -------------------------------------------------------------------------------------15
20
25

4:40
4:20
4:20

AIR

2

3

14

24:20

AIR/O2

2

2

7

16:40

AIR

1

5

7

29

47:00

AIR/O2

1

5

3

15

29:20

AIR

5

6

7

57

80:00

AIR/O2

5

6

4

24

44:20

0.5

K

1

M

1.5

O

Exceptional Exposure: In-Water Air Decompression ------------- In-Water Air/O2 Decompression or SurDO2 Required ----------30
35

4:00
3:40

AIR

3

6

6

7

95

121:40

AIR/O2

3

6

6

4

34

63:00

AIR

1

5

6

6

22

144

188:20

AIR/O2

1

5

6

6

11

41

79:40

1.5

Z

2

Z

Exceptional Exposure: In-Water Air/02 Decompression ------------- SurDO2 Required------------------------------------------------------40

3:40

45

3:40

50

3:40

55

3:40

AIR

2

6

5

13

28

178

236:20

AIR/O2

2

6

5

13

14

48

97:40

AIR

4

5

10

20

28

235

306:20

AIR/O2

4

5

10

20

14

63

130:40

AIR

4

8

13

25

29

277

360:20

AIR/O2

4

8

13

25

15

75

154:40

AIR

5

11

19

26

28

336

429:20

AIR/O2

5

11

19

26

14

87

181:40

2.5
3
3.5
4

Exceptional Exposure: SurDO2 ---------------------------------------------------------------------------------------------------------------------------60
70

9-82

3:20
3:20

AIR

1

8

13

23

25

31

406

511:00

AIR/O2

1

8

13

23

25

16

100

205:20

AIR

4

12

21

24

25

48

499

637:00

AIR/O2

4

12

21

24

25

24

119

253:20

4.5
5.5

U.S. Navy Diving Manual — Volume 2

Table 9-9. Air Decompression Table (Continued).
(DESCENT RATE 75 FPM—ASCENT RATE 30 FPM)

Bottom Time
(min)

Time
to First
Stop
(M:S)

DECOMPRESSION STOPS (FSW)
Stop times (min) include travel time,
except first air and first O2 stop
Gas Mix

100

90

80

70

60

50

40

30

20

Total
Ascent
Time
(M:S)

Chamber
O2
Periods

Repet
Group

0

D

0.5

H

190 FSW
5
10

6:20
5:20

AIR

0

6:20

AIR/O2

0

6:20

AIR

2

8

16:00

AIR/O2

1

4

11:00

In-Water Air/O2 Decompression or SurDO2 Recommended -------------------------------------------------------------------------------------15
20

4:40
4:20

AIR

1

3

3

16

28:20

AIR/O2

1

3

2

8

19:40

AIR

1

2

6

7

34

55:00

AIR/O2

1

2

6

4

17

35:20

0.5

K

1

N

Exceptional Exposure: In-Water Air Decompression ------------- In-Water Air/O2 Decompression or SurDO2 Required ----------25
30

4:20
4:00

AIR

2

6

7

7

72

99:00

AIR/O2

2

6

7

3

28

51:20

AIR

1

6

5

7

13

122

158:40

AIR/O2

1

6

5

7

7

38

74:00

1.5

Z

2

Z

Exceptional Exposure: In-Water Air/02 Decompression ------------- SurDO2 Required------------------------------------------------------35
40

4:00
3:40

45

3:40

50

3:40

AIR

4

5

6

8

26

165

218:40

AIR/O2

4

5

6

8

13

45

91:00

AIR

1

5

5

8

17

28

217

285:20

AIR/O2

1

5

5

8

17

15

58

123:40

AIR

2

5

6

12

24

29

264

346:20

AIR/O2

2

5

6

12

24

15

71

149:40

AIR

3

5

10

17

26

28

324

417:20

AIR/O2

3

5

10

17

26

14

85

179:40

2.5

Z

3
3.5
4

Exceptional Exposure: SurDO2 ---------------------------------------------------------------------------------------------------------------------------55
60

3:40
3:40

90

3:20

120

3:00

AIR

4

8

10

24

25

30

397

502:20

AIR/O2

4

8

10

24

25

15

99

204:40

AIR

5

10

16

24

25

40

454

578:20

AIR/O2

5

10

16

24

25

20

109

233:40

11

19

20

21

28

51

83

626

863:00

AIR
AIR/O2

11

19

20

21

28

51

41

178

408:20

AIR

15

17

19

20

37

46

79

113

691

1040:40

AIR/O2

15

17

19

20

37

46

79

55

219

551:00

CHAPTER 9 — Air Decompression

4.5
5
8.5
10.5

9-83

Table 9-9. Air Decompression Table (Continued).
(DESCENT RATE 75 FPM—ASCENT RATE 30 FPM)

Bottom Time
(min)

Time
to First
Stop
(M:S)

DECOMPRESSION STOPS (FSW)
Stop times (min) include travel time,
except first air and first O2 stop
Gas Mix

100

90

80

70

60

50

40

30

20

Total
Ascent
Time
(M:S)

Chamber
O2
Periods

Repet
Group

200 FSW
Exceptional Exposure --------------------------------------------------------------------------------------------------------------------------------5
10
15
20
25
30
35

6:40
5:40
5:00
4:40
4:20
4:20
4:00

40

4:00

45

3:40

AIR

0

6:40

AIR/O2

0

6:40

AIR

3

8

17:20

AIR/O2

2

4

12:20

AIR

2

3

5

19

34:40

AIR/O2

2

3

3

9

23:00

AIR

2

4

6

7

43

67:20

AIR/O2

2

4

6

4

20

41:40

AIR

1

5

6

6

7

85

115:00

AIR/O2

1

5

6

6

4

32

64:20

AIR

4

6

5

7

19

145

191:00

AIR/O2

4

6

5

7

10

42

84:20

AIR

2

5

5

6

13

28

188

251:40

AIR/O2

2

5

5

6

13

14

51

106:00

AIR

4

5

5

11

21

28

249

327:40
143:00

AIR/O2

50

3:40

4

5

5

11

21

14

68

AIR

1

4

5

10

14

25

28

306

397:20

AIR/O2

1

4

5

10

14

25

14

81

168:40

AIR

2

4

8

10

21

26

28

382

485:20

AIR/O2

2

4

8

10

21

26

14

97

201:40

0

E

0.5

H

0.5

L

1

O

1.5

Z

2

Z

2.5
3.5
3.5
4.5

210 FSW
Exceptional Exposure --------------------------------------------------------------------------------------------------------------------------------4
5
10
15
20
25

7:00
6:20
5:40
5:00
4:40
4:40

30

4:20

35

4:00

AIR

0

7:00

AIR/O2

0

7:00

AIR

2

9:00

AIR/O2

1

8:00

AIR

2

3

9

20:20

AIR/O2

2

2

4

14:40

AIR

1

3

3

6

24

42:40

AIR/O2

1

3

3

3

12

28:00

AIR

1

3

5

6

7

57

84:20

AIR/O2

1

3

5

6

4

23

47:40

AIR

3

6

5

7

8

110

144:20

AIR/O2

3

6

5

7

4

38

73:40

2

5

6

6

6

26

163

219:00

AIR
AIR/O2

40
45
50

9-84

4:00
4:00
3:40

2

5

6

6

6

13

45

93:20

AIR

1

4

5

6

7

18

28

223

296:40

AIR/O2

1

4

5

6

7

18

14

60

130:00

AIR

2

5

5

7

11

26

28

278

366:40

AIR/O2

2

5

5

7

11

26

14

76

161:00

AIR

4

4

6

11

18

26

28

355

456:40

AIR/O2

4

4

6

11

18

26

14

91

194:00

AIR

1

4

5

10

12

23

26

36

432

553:20

AIR/O2

1

4

5

10

12

23

26

18

105

223:40

0

D

0.5

E

0.5

I

1

M

1

O

2

Z

2.5

Z

3
3.5
4
5

U.S. Navy Diving Manual — Volume 2

Table 9-9. Air Decompression Table (Continued).
(DESCENT RATE 75 FPM—ASCENT RATE 30 FPM)

Bottom Time
(min)

Time
to First
Stop
(M:S)

Gas
Mix

DECOMPRESSION STOPS (FSW)
Stop times (min) include travel time,
except first air and first O2 stop
130

120

110

100

90

80

70

60

50

40

30

20

Total
Ascent
Time
(M:S)

Chamber
O2
Periods

Repet
Group

220 FSW
Exceptional Exposure --------------------------------------------------------------------------------------------------------------------------------4
5
10
15
20
25
30
35
40

7:20
6:40
6:00
5:20
5:00
4:40
4:20
4:20
4:00

AIR

0

7:20

AIR/O2

0

7:20

AIR

3

10:20

AIR/O2

2

9:20

AIR

3

4

10

23:40

AIR/O2

3

2

5

17:00

AIR

3

2

4

7

28

50:00

AIR/O2

3

2

4

4

14

33:20

AIR

2

4

6

6

7

70

100:40

AIR/O2

2

4

6

6

4

26

54:00

AIR

1

5

6

6

6

14

133

176:20

AIR/O2

1

5

6

6

6

7

41

82:40

AIR

1

4

5

6

6

10

28

183

248:00

AIR/O2

1

4

5

6

6

10

14

50

106:20

AIR

3

5

5

5

10

22

28

251

334:00

AIR/O2

3

5

5

5

10

22

14

68

147:20

AIR

1

4

5

5

9

15

26

28

319

416:40

AIR/O2

1

4

5

5

9

15

26

14

84

183:00

0

E

0.5

E

0.5

J

1

N

1.5

Z

2

Z

2.5
3.5
4

250 FSW
Exceptional Exposure --------------------------------------------------------------------------------------------------------------------------------4
5
10
15
20
25
30
35

7:40
7:40
6:20
5:40
5:20
5:00
4:40
4:40

AIR

4

12:20

AIR/O2

2

10:20

AIR

7

15:20

AIR/O2

4

12:20

AIR

2

2

4

3

15

33:00

AIR/O2

2

2

4

2

7

24:20

AIR

2

2

3

4

6

7

53

83:20

AIR/O2

2

2

3

4

6

4

22

49:40

AIR

2

2

4

6

6

6

11

125

168:00

AIR/O2

2

2

4

6

6

6

6

39

82:20

AIR

1

4

4

5

6

6

10

28

189

258:40

AIR/O2

1

4

4

5

6

6

10

14

51

112:00

AIR

1

4

4

4

5

6

9

25

28

267

358:20

AIR/O2

1

4

4

4

5

6

9

25

15

72

160:40

AIR

3

4

4

5

5

10

19

26

28

363

472:20

AIR/O2

3

4

4

5

5

10

19

26

14

93

203:40

CHAPTER 9 — Air Decompression

0.5

F

0.5

G

0.5

L

1

O

2

Z

2.5
3.5
4

9-85

Bottom Time
(min)

Time
to First
Stop
(M:S)

Gas
Mix

DECOMPRESSION STOPS (FSW)
Stop times (min) include travel time,
except first air and first O2 stop
130

120

110

100

90

80

70

60

50

40

30

20

Total
Ascent
Time
(M:S)

Chamber
O2
Periods

Repet
Group

300 FSW
Exceptional Exposure --------------------------------------------------------------------------------------------------------------------------------4
5
10
15
20
25

9-86

9:00
8:40
7:20
6:20
6:00
5:40

AIR

3

7

19:40

AIR/O2

2

4

15:40

AIR

3

3

8

23:20

AIR/O2

3

2

4

18:40

AIR

2

3

2

3

4

7

35

64:00

AIR/O2

2

3

2

3

4

4

18

44:20

AIR

1

2

2

3

3

5

6

7

11

125

172:00

AIR/O2

1

2

2

3

3

5

6

7

6

39

86:20

AIR

2

2

2

4

5

5

5

6

16

28

219

300:40

AIR/O2

2

2

2

4

5

5

5

6

16

14

59

137:00

AIR

1

3

4

4

4

5

5

5

18

26

28

324

433:20

AIR/O2

1

3

4

4

4

5

5

5

18

26

14

85

195:40

0.5

G

0.5

I

1

N

2

Z

3
4

U.S. Navy Diving Manual — Volume 2

CHAPTER 10

Nitrogen-Oxygen Diving Operations
10-1

INTRODUCTION

Nitrogen-oxygen (NITROX) diving is a unique type of diving using nitrogenoxygen breathing gas mixtures ranging from 75 percent nitrogen/25 percent
oxygen to 60 percent nitrogen/40 percent oxygen. Using NITROX significantly
increases the amount of time a diver can spend at depth without decompressing. It
also decreases the required decompression time compared to a similar dive made
to the same depth using air. NITROX may be used in all diving operations suitable
for air, but its use is limited to a normal depth of 140 fsw.
NITROX breathing gas mixtures are normally used for shallow dives. The most
benefit is gained when NITROX is used shallower than 50 fsw, but it can be
advantageous when used to a depth of 140 fsw.
10-1.1

Advantages and Disadvantages of NITROX Diving. The advantages of using

NITROX rather than air for diving include:
n
n
n
n
n

Extended bottom times for no-decompression diving.
Reduced decompression time.
Reduced residual nitrogen in the body after a dive.
Reduced possibility of decompression sickness.
Reduced Nitrogen Narcosis

The disadvantages of using NITROX include:
n
n
n
n
n
n
10-2

Increased risk of CNS oxygen toxicity.
Producing NITROX mixtures requires special equipment.
NITROX equipment requires special cleaning techniques.
Long-duration NITROX dives can result in pulmonary oxygen toxicity.
Working with NITROX systems requires special training.
NITROX is expensive to purchase.

EQUIVALENT AIR DEPTH

The partial pressure of nitrogen in a NITROX mixture is the key factor deter­mining
the diver’s decompression obligation. Oxygen plays no role. The decompression
obligation for a NITROX dive therefore can be determined using the Standard Air
Tables simply by selecting the depth on air that has the same partial pressure of
nitrogen as the NITROX mixture. This depth is called the Equivalent Air Depth
(EAD). For example, the nitrogen partial pressure in a 68% nitrogen 32% oxygen
mixture at 63 fsw is 2.0 ata. This is the same partial pressure of nitrogen found in
air at 50 fsw. 50 fsw is the Equivalent Air Depth.

CHAPTER 10 — Nitrogen-Oxygen Diving Operations

10-1

10-2.1

Equivalent Air Depth Calculation.

The Equivalent Air Depth can be computed from the following formula:

Where:
EAD = equivalent depth on air (fsw)
D
= diving depth on mixture (fsw)
O2% = oxygen concentration in breathing medium (percentage decimal)
For example, while breathing a mixture containing 40 percent oxygen (O2% =
0.40) at 70 fsw (D = 70), the equivalent air depth would be:

Note that with NITROX, the Equivalent Air Depth is always shallower than the
diver’s actual depth. This is the reason that NITROX offers a decompression
advantage over air.
10-3

OXYGEN TOXICITY

Although the use of NITROX can increase the diver’s bottom time and reduce the
risk of nitrogen narcosis, using a NITROX mixture raises the concern for oxygen
toxicity. For example, using air as the breathing medium, an oxygen partial pres­
sure (ppO2) of 1.6 ata is reached at a depth of 218 fsw. In contrast, when using the
NITROX mixture containing 60 percent nitrogen and 40 percent oxygen, a ppO2 of
1.6 ata is reached at 99 fsw. Therefore, oxygen toxicity must be considered when
diving a NITROX mixture and is a limiting factor when considering depth and
duration of a NITROX dive.
Generally speaking, there are two types of oxygen toxicity—central nervous system
(CNS) oxygen and pulmonary oxygen toxicity. CNS oxygen toxicity is usually
not encountered unless the partial pressure of oxygen approaches or exceeds 1.6
ata, but it can result in serious symptoms including potentially life-threatening
convulsions. Pulmonary oxygen toxicity may result from conducting long-duration
dives at oxygen partial pressures in excess of 1.0 ata. For example, a dive longer
than 240 minutes at 1.3 ata or a dive longer than 320 minutes at 1.1 ata may place

10-2

U.S. Navy Diving Manual — Volume 2

the diver at risk if the exposure is on a daily basis. Pulmonary oxygen toxicity
under these conditions can result in decrements of pulmonary function, but is not
life threatening.
The NITROX Equivalent Air Depth (EAD) Decompression Selection Table (Table
10‑1) was developed considering both CNS and pulmonary oxygen toxicity. Normal
working dives that exceed a ppO2 of 1.4 ata are not permitted, principally to avoid
the risk of CNS oxygen toxicity. Dives with a ppO2 less than 1.4 ata, however, can
be conducted using the full range of bottom times allowed by the air tables without
concern for CNS or pulmonary oxygen toxicity.
Supervisors must keep in mind that pulmonary oxygen toxicity may become an
issue with frequent, repetitive diving. The effects of pulmonary oxygen toxicity
can be cumulative and can reduce the underwater work performance of susceptible
individuals after a long series of repetitive daily exposures. Fatigue, headache, flulike symptoms, and numbness of the fingers and toes may also be experienced with
repetitive exposures. Table 10‑1 takes these repetitive exposures into account, and
therefore problems with oxygen toxicity should not be encountered with its use.
If symptoms are experienced, the diver should stop diving NITROX until they
resolve.
10-3.1

Selecting the Proper NITROX Mixture. Considerable caution must be used when

selecting the proper NITROX mixture for a dive. The maximum depth of the
dive must be known as well as the planned bottom time. Once the maximum
depth is known, the various NITROX mixtures can be evaluated to determine
which one will provide the least amount of decom­pression while also allowing
for a maximum bottom time. If a diver’s depth exceeds that allowed for a certain
NITROX mixture, the diver is at great risk of life-threatening oxygen toxicity.
10-4

NITROX DIVING PROCEDURES
10-4.1

NITROX Diving Using Equivalent Air Depths. NITROX diving is based upon the

current Air Decompression Tables. The actual schedule used is adjusted for the
oxygen percentage in the breathing gas. To use the EAD Decompression Selection
Table (Table 10-1), find the actual oxygen percentage of the breathing gas in the
heading and the diver’s actual depth in the left column to determine the appropriate
schedule to be used from the Air Decompression Tables. The EAD decompression
schedule is where the column and row intersect. When using Table 10-1, round all
gas mixtures using the standard rounding rule where gas mixes at or above 0.5%
round up to the next whole percent and mixes of 0.1% to 0.4% round down to
the next whole percent. Once an EAD is determined and an air table is selected,
follow the rules of the air table using the EAD for the remainder of the dive.

CHAPTER 10 — Nitrogen-Oxygen Diving Operations

10-3

Table 10‑1. Equivalent Air Depth Table.
EAD Feet

Diver’s
Actual
Depth
(fsw)

25%
O2

26%
O2

27%
O2

28%
O2

29%
O2

30%
O2

31%
O2

32%
O2

33%
O2

34%
O2

35%
O2

36%
O2

37%
O2

38%
O2

39%
O2

40%
O2

20

20

20

20

20

20

20

20

15

15

15

15

15

10

10

10

10

30

30

30

30

30

30

30

30

25

25

25

20

20

20

20

20

20

40

40

40

40

40

40

40

40

35

30

30

30

30

30

30

25

25

50

50

50

50

50

50

50

50

40

40

40

40

40

35

35

35

35

60

60

60

60

60

60

60

50

50

50

50

50

50

50

50

40

40

70

70

70

70

70

70

60

60

60

60

60

60

60

50

50

50

50

80

80

80

80

80

70

70

70

70

70

70

70

60

60

60

60

60

90

90

90

90

90

80

80

80

80

80

80

70

70

70
70
(:107) (:80)

70
(:61)

70
(:47)

100

100

100

100

90

90

90

90

90

90

80
(:113)

80
(:82)

80
(:61)

80
(:46)

80
(:29)

70
(:23)

110

110

110

110

100

100

100

100

100
(:96)

100
(:69)

90
(:51)

90
(:39)

90
(:30)

120

120

120

120

110

110

110
(:91)

110
(:64)

110
(:47)

100
(:35)

100
(:27)

130

130

130

120

120
(:95)

120
(:65)

120
(:47)

120
(:35)

110
(:26)

140

140

140
130
(:109) (:73)

130
(:50)

130
(:36)

150

150
(:89)

150
(:59)

160

160
(:50)

160
(:35)

EAD

=

Equivalent Air Depth - For Decompression Table Selection Only Rounded to Next Greater Depth

=

1.4 ata Normal working limit.

=

Depth exceeds the normal working limit, requires the Commanding Officer’s authorization and surface-

80
(:36)

140
(:41)

supplied equipment. Repetitive dives are not authorized. Times listed in parentheses indicate maximum
allowable exposure.

10-4

Note1:

Depths not listed are considered beyond the safe limits of NITROX diving.

Note2:

The EAD, 1.4 ata Normal Working Limit Line and Maximum Allowable Exposure Time for dives deeper than
the Normal Working Limit Line are calculated assuming the diver rounds the oxygen percentage in the gas
mixture using the standard rounding rule discussed in paragraph 10‑4.1. The calculations also take into
account the allowable ± 0.5 percent error in gas analysis.

U.S. Navy Diving Manual — Volume 2

10-4.2

SCUBA Operations. For SCUBA operations, analyze the nitrox mix in each bottle

to be used prior to every dive.

10-4.3

Special Procedures. In the event there is a switch to air during the NITROX dive,

using the diver’s maximum depth and bottom time follow the Air Decompression
Table for the actual depth of the dive.

10-4.4

Omitted Decompression. In the event that the loss of gas required a direct

ascent to the surface, any decom­pression requirements must be addressed using
the standard protocols for “omitted decompression.” For omitted decompression
dives that exceed the maximum depth listed on Table 10-1, the diving supervisor
must rapidly calculate the diver’s EAD and follow the omitted decompression
procedures based on the diver’s EAD, not his or her actual depth. If time will
not permit this, the diving supervisor can elect to use the diver’s actual depth and
follow the omitted decompression procedures.

10-4.5

Dives Exceeding the Normal Working Limit. The EAD Table has been developed

to restrict dives with a ppO2 greater than 1.4 ata and limits dive duration based
on CNS oxygen toxicity. Dives exceeding the normal working limits of Table
10-1 require the Commanding Officer’s authoriza­tion and are restricted to surfacesupplied diving equipment only. All Equivalent Air Depths provided below the
normal working limit line have the maximum allowable exposure time listed
alongside. This is the maximum time a diver can safely spend at that depth and
avoid CNS oxygen toxicity. Repetitive dives are not authorized when exceeding
the normal working limits of Table 10-1.
10-5

NITROX REPETITIVE DIVING

Repetitive diving is possible when using NITROX or combinations of air and
NITROX. Once the EAD is determined for a specific dive, the Air Decompression
Tables are used throughout the dive using the EAD from Table 10‑1.
The Residual Nitrogen Timetable for Repetitive Air Dives will be used when
applying the EAD for NITROX dives. Determine the Repetitive Group Designator
for the dive just completed using either Table 9-7, No-Decompression Limits and
Repetitive Group Designators for No-Decompression Air Dives or Table 9-9, Air
Decompression Table.
Enter Table 9‑8, Residual Nitrogen Timetable for Repetitive Air Dives, using the
repetitive group designator. If the repetitive dive is an air dive, use Table 9‑8 as is.
If the repetitive dive is a NITROX dive, determine the EAD of the repetitive dive
from Table 10‑1 and use that depth as the repetitive dive depth.
10-6

NITROX DIVE CHARTING

The NITROX Diving Chart (Figure 10‑1) should be used for NITROX diving and
filled out as described in Chapter 9. The NITROX chart has an additional block for
EAD with the percentage of gas written in the bottom mix block.

CHAPTER 10 — Nitrogen-Oxygen Diving Operations

10-5

Date:

Type of Dive:

N2O2

Diver 1:

Diver 2:

Rig:

PSIG:

O2%:

Rig:

Diving Supervisor:
EVENT

Standby:
PSIG:

O2%:

Rig:

Chartman:
STOP TIME

O2%:

Bottom Mix:

CLOCK TIME

LS or 20 fsw

PSIG:

EVENT

TIME/DEPTH

Descent Time (Water)

RB

Stage Depth (fsw)

LB

Maximum Depth (fsw)

st

EAD (NITROX)

R 1 Stop
190 fsw

Total Bottom Time

180 fsw

Table/Schedule

170 fsw

Time to 1st Stop (Planned)

160 fsw

Time to 1st Stop (Actual)

150 fsw

Delay to 1st Stop

140 fsw

Travel/Shift/Vent Time

130 fsw

Ascent Time-Water/SurD (Actual)

120 fsw

Undress Time-SurD (Actual)

110 fsw

Descent Chamber-SurD (Actual)

100 fsw

Total SurD Surface Interval

90 fsw

Ascent Time–Chamber (Actual)

80 fsw

HOLDS ON DESCENT

70 fsw

DEPTH

PROBLEM

60 fsw
50 fsw
40 fsw
30 fsw

DELAYS ON ASCENT

20 fsw

DEPTH

PROBLEM

RS
RB CHAMBER
50 fsw chamber

DECOMPRESSION PROCEDURES USED

40 fsw chamber

N2O2

30 fsw chamber
RS CHAMBER
TDT

TTD

o In-water N2O2 decompression
o In-water N2O2/O2 decompression
o SurDO2
REPETITIVE GROUP:

Remarks:

Figure 10‑1. NITROX Diving Chart.

10-6

U.S. Navy Diving Manual — Volume 2

10-7

FLEET TRAINING FOR NITROX

A Master Diver shall conduct training for NITROX diving prior to conducting
NITROX diving operations. Actual NITROX dives are not required for this
training. The following are the minimum training topics to be covered:
n Pulmonary and CNS oxygen toxicity associated with NITROX diving.
n EAD tables and their association with the air tables.
n Compute the Equivalent Air Depth and then enter Table 6-2 to determine
chamber requirement. (Note – OSHA requires a chamber on station for opencircuit NITROX diving for all civilian divers.)
n Safe handling of NITROX mixtures.
NITROX Charging and Mixing Technicians must be trained on the following
topics:
n
n
n
n
10-8

Oxygen handling safety.
Oxygen analysis equipment.
NITROX mixing techniques.
NITROX cleaning requirements (MIL-STD-1330 Series).

NITROX DIVING EQUIPMENT

NITROX diving can be performed using a variety of equipment that can be broken
down into two general categories: surface-supplied or closed- and open-circuit
SCUBA. Closed-circuit UBA apparatus is discussed in Chapter 16.
10-8.1

10‑8.1.1

Open-Circuit SCUBA Systems. Open-circuit SCUBA systems for NITROX
diving are identical to air SCUBA systems with one exception: the SCUBA bottles
are filled with NITROX (nitrogen-oxygen) rather than air. There are specific
regulators authorized for NITROX diving, which are identified on the ANU list.
These regulators have been tested to confirm their compatibility with the higher
oxygen percentages encoun­tered with NITROX diving.
Regulators. SCUBA regulators designated for NITROX use should be cleaned to

the standards of MIL-STD-1330. Once designated for NITROX use and cleaned,
the regulators should be maintained to the level of cleanliness outlined in MILSTD-1330.

CHAPTER 10 — Nitrogen-Oxygen Diving Operations

10-7

10‑8.1.2

Bottles. SCUBA bottles designated for

use with NITROX should be oxygen
cleaned and maintained to that level.
The bottles should have a NITROX
label in large yellow letters on a green
background. Once a bottle is cleaned
and designated for NITROX diving, it
should not be used for any other type of
diving (Fig­ure 10‑2).
10-8.2

10-8.3

All high-pressure flasks,
SCUBA cyl­inders, and all highpressure NITROX charging equipment
that comes in con­tact with 100 percent
oxygen during NI­
TROX diving,
mixing, or charging evolutions must be
cleaned and main­tained for NITROX
service in accordance with the current
MIL-STD-1330 series.

Yellow
Yellow Lettering

Green
Yellow

General.

Figure 10‑2. NITROX SCUBA Bottle
Markings.

Surface-Supplied NITROX Diving. Surface-supplied NITROX diving systems

must be modified to make them compatible with the higher percentage of oxygen
found in NITROX mixtures. A request to convert the system to NITROX must
be forwarded to NAVSEA 00C for review and approval. The request must be
accompanied by the proposed changes to the Pre-survey Outline Booklet (PSOB)
permitting system use with NITROX. Once the system is designated for NITROX,
it shall be labeled NITROX with large yellow letters on a green background. MILSTD-1330D outlines the cleanli­ness requirements to which a surface-supplied
NITROX system must be maintained.
Once a system has been cleaned and designated for NITROX use, only air meeting
the requirements of Table 10‑2 shall be used to charge the system gas flasks. Air
diving, using a NITROX designated system, is authorized if the air meets the purity
requirements of Table 10‑2.
The EGS used in surface-supplied NITROX diving shall be filled with the same
mixture that is being supplied to the diver ± 0.5 percent.
10-9

EQUIPMENT CLEANLINESS

Cleanliness and the procedures used to obtain cleanliness are a concern with
NITROX systems. MIL-STD-1330 is applicable to anything with an oxygen level
higher than 25 percent by volume. Therefore, MIL-STD-1330 must be followed
when dealing with NITROX systems. Personnel involved in the maintenance and
repair of NITROX equipment shall complete an oxygen clean worker course, as
described in MIL-STD-1330. Even with oxygen levels of 25 to 40 percent, there
is still a greater risk of fire than with compressed air. Materials that would not

10-8

U.S. Navy Diving Manual — Volume 2

normally burn in air may burn at these higher O2 levels. Normally combustible
materials require less energy to ignite and will burn faster. The energy required
for ignition can come from different sources, for example adiabatic compression
or particle impact/spark. Another concern is that if improper cleaning agents or
processes are used, the agents themselves can become fire or toxic hazards. It is
therefore important to adhere to MIL-STD-1330 to reduce the risk of damage or
loss of equipment and injury or death of personnel.
10-10

BREATHING GAS PURITY

It is essential that all gases used in producing a NITROX mixture meet the breathing
gas purity standards for oxygen (Table 4‑2) and nitrogen (Table 4‑4). If air is to
be used to produce a mixture, it must be compressed using an oil free NITROX
approved compressor or meet the purity requirements of oil free air (Table 10‑2).
Prior to diving, all NITROX gases shall be analyzed using an ANU approved O2
analyzer accurate to within ± 0.5 percent.
10-11

NITROX MIXING

NITROX mixing can be accomplished by a variety of techniques to produce a final
predetermined nitrogen-oxygen mixture. The techniques for mixing NITROX are
listed as follows:
1. Continuous Flow Mixing. There are two techniques for continuous flow mixing:

A mix-maker uses a precalibrated mixing system that pro­
portions the amount of each gas in the mixture as it is delivered to a
common mixing chamber. A mix-maker performs a series of functions
that ensures accurate mixtures. The gases are regulated to the same
temperature and pressure before they are sent through precision meter­
ing valves. The valves are precalibrated to provide the desired mixing
pressure. The final mixture can be provided directly to the divers or be
compressed using an oil-free compressor into storage banks.

a. Mix-maker.

b. Oxygen Induction. Oxygen

induction uses a system where low pressure
oxygen is delivered to the intake header of an oil-free compressor, where
it is mixed with the air being drawn into the compressor. Oxygen flow
is adjusted and the compressor output is monitored for oxygen content.
When the desired NITROX mixture is attained the gas is diverted to
the storage banks for diver use while being continually monitored for
oxygen content (Figure 10‑3).

2. Mixing by Partial Pressure. Partial pressure mixing techniques are similar to

those used in helium-oxygen mixed gas diving and are discussed in Chapter 16.

CHAPTER 10 — Nitrogen-Oxygen Diving Operations

10-9

Figure 10‑3. NITROX O2 Injection System.

Oil-free air can be used as a Nitrogen
source for the partial pressure mixing of NITROX using the following
procedures:

a. Partial Pressure Mixing with Air.

n Prior to charging air into a NITROX bottle, the NITROX mixing
technician shall smell, taste, and feel the oil-free air coming from the
compressor for signs of oil, mist, or particulates, or for any unusual
smell. If any signs of compressor malfunction are found, the system
must not be used until a satisfactory air sample has been completed.
n Prior to charging with oxygen, to produce a NITROX mix, the
NITROX-charging technician shall charge the bottle to at least 100
psi with oil-free air. This will reduce the risk of adiabatic compres­
sion temperature increase. Once 100 psi of oil-free air has been
added to the charging vessel, the required amount of oxygen should
then be added. The remaining necessary amount of oil-free air can
then be safely charged into the bottle. The charging rate for NITROX
mixing shall not exceed 200 psi per minute.
WARNING

Mixing contaminated or non-oil free air with 100% oxygen can result in a
catastrophic fire and explosion.

n Compressed air for NITROX mixing shall meet the purity stan­dards

10-10

U.S. Navy Diving Manual — Volume 2

for “Oil Free Air,” (Table 10‑2). All compressors producing air for
NITROX mixing shall have a filtration system designed to produce
oil-free air that has been approved by NAVSEA 00C3. In addition,
all compressors producing oil-free air for NITROX charging shall
have an air sample taken within 90 days prior to use.
Table 10‑2. Oil Free Air.
Constituent

Specification

Oxygen (percent by volume)

20-22%

Carbon dioxide (by volume)

500 ppm (max)

Carbon monoxide (by volume)

2 ppm (max)

Total hydrocarbons [as Methane (CH4) by volume]

25 ppm (max)

Odor

Not objectionable

Oil, mist, particulates

0.1 mg/m3 (max)

Separated Water

None

Total Water

0.02 mg/l (max)

Halogenated Compounds (by volume):
Solvents

0.2 ppm (max)

3. Mixing Using a Membrane System. Membrane systems selectively separate

gas molecules of different sizes such as nitrogen or oxygen from the air. By
removing the nitrogen from the air in a NITROX membrane system the oxygen
percent is increased. The resulting mixture is NITROX. Air is fed into an inline filter canister system that removes hydrocarbons and other contaminants.
It is then passed into the membrane canister containing thousands of hollow
membrane fibers. Oxygen permeates across the membrane at a controlled
rate. The amount of nitrogen removed is determined by a needle valve. Once
the desired nitrogen-oxygen ratio is achieved, the gas is diverted through a
NITROX approved compressor and sent to the storage banks (see Figure 10‑4
and Figure 10‑5). Membrane systems can also concentrate CO2 and argon.

4. Mixing Using Molecular Sieves. Molecular sieves are columns of solid, highly

selective chemical absorbent which perform a similar function to membrane
systems, and are used in a similar fashion. Molecular sieves have the added
advantage of absorbing CO2 and moisture from the feed gas.

5. Purchasing Premixed NITROX. Purchasing premixed NITROX is an acceptable

way of obtaining a NITROX mixture. When purchasing premixed NITROX
it is requisite that the gases used in the mixture meet the minimum purity
standards for oxygen (Table 4‑2) and nitrogen (Table 4‑4).

CHAPTER 10 — Nitrogen-Oxygen Diving Operations

10-11

10-12

NITROX MIXING, BLENDING, AND STORAGE SYSTEMS

NITROX mixing, blending, and storage systems shall be designed for oxygen
service and constructed using oxygen-compatible material following accepted
military and commercial practices in accordance with either ASTM G-88, G-63,
G-94, or MIL-STD-438 and -777. Commands should contact NAVSEA 00C for
specific guidance on developing NITROX mixing, blending, or storage systems.
Commands are not authorized to build or use a NITROX system without prior
NAVSEA 00C review and approval.

Figure 10‑4. LP Air Supply NITROX Membrane Configuration.

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U.S. Navy Diving Manual — Volume 2

Figure 10‑5. HP Air Supply NITROX Membrane Configuration.

CHAPTER 10 — Nitrogen-Oxygen Diving Operations

10-13

PAGE LEFT BLANK INTENTIONALLY

10-14

U.S. Navy Diving Manual — Volume 2

CHAPTER 11

Ice and Cold Water
Diving Operations
11-1

INTRODUCTION
11-1.1

Purpose. This chapter explains the special requirements for ice and cold water

diving.

11-1.2

11-1.3

Scope. Polar regions and other cold weather environments are uniquely hostile
to divers, topside support personnel, and equipment. Diving where ice cover is
present can be extremely hazardous and requires special equipment as well as
appropriate operating and support procedures. Awareness of environmental
conditions, personnel and equipment selection, and adequate logistical support are
vital to mission success and dive team safety.
References. References cited in this chapter:

n A Guide to Extreme Cold Weather Operations (Naval Safety Center, July 1986)
n Polar Operations Manual S0300-A5-MAN-010 (Naval Coastal Systems
Center) (NCSC)
n Guide to Polar Diving (Office of Naval Research, June 1976)
n UCT Arctic Operation Manual NAVFAC P-992 (To obtain a copy of this
manual, contact NAVFAC Ocean Facilities Programs.)
n FM 21-305- Manual for the Wheeled Vehicle Driver Chapter 21
n Field Manual for the U.S. Antarctic Program Chapter 1 Extreme Cold Weather
Clothing
n Rescue and Survival Systems Manual, (COMDTINST M10470.10 series)
11-2

OPERATIONS PLANNING

Normal diving procedures generally apply to diving in extremely cold environ­
ments. However, there are a number of significant equipment and procedural
differences that enhance the diver’s safety.
11-2.1

Planning Guidelines. The following special planning considerations relate to

diving under/near ice cover or in water 37°F and colder:

n The task and requirement for ice diving should be reviewed to ascertain that it
is operationally essential.

CHAPTER 11 — Ice and Cold Water Diving Operations

11-1

n Environmental conditions such as ice thickness, water depth, temperature,
wind velocity, current, visibility, and light conditions should be determined.
Ideally, a reconnaissance of the proposed dive site is performed by the Diving
Supervisor or a person with ice-covered or cold water diving experience.
n The type of dive equipment chosen must be suited for the operation.
n Logistical planning must include transportation, ancillary equipment, provi­
sioning, fuel, tools, clothing and bedding, medical evacuation procedures,
communications, etc.
n Due to the unique dangers of ice diving and special considerations when
conducting cold weather operations, all personnel shall complete formal
training, such as the USCG Cold Water Ice Diving Course (CWID), or conduct
ice diving specific Unit Level Training (ULT) to ensure mission safety and
success.
NOTE

11-2.2

The water temperature of 37°F was set as a limit as a result of Naval
Experimental Diving Unit’s regulator freeze-up testing. For planning
purposes, the guidance above may also be used for diving where the
water temperature is 38°F and above.
Navigational Considerations. Conditions in cold and ice-covered water affect
diver underwater navigation in the following ways:

n The proximity of the magnetic pole in polar regions makes the magnetic com­
pass useless.
n The life of batteries in homing beacons, strobes, and communication equip­
ment is shortened when used in cold water.
n Surface light is so diffused by ice cover that it is nearly impossible to deter­mine
its source.
n Direct ascent to the surface is impossible when under the ice and determining
return direction is often hindered.
n In shallow ice-covered waters, detours are often required to circumvent keels
or pressure ridges beneath the ice.
n With an ice cover, there are no waves and therefore no ripple patterns on the
bottom to use for general orientation.
11-2.3

SCUBA Considerations. SCUBA equipment has advantages and disadvantages

that should be considered when planning a cold water dive.
The advantages of using SCUBA are:

11-2

U.S. Navy Diving Manual — Volume 2

Figure 11‑1. Two SCUBA cylinders fitted with two actual redundant first-stage regulators
with GLO-TOOB attached.

n Portability
n Quick deployment
n Minimal surface-support requirements
The disadvantages of using SCUBA are:
n Susceptibility of regulator to freezing
n Depth limitations
n Limited communications
n Severely limited ability to employ decompression diving techniques
n Duration limitations of CO2 removal systems in closed-circuit UBA
11-2.4

SCUBA Regulators. When diving in cold water, the diver should avoid purging
the second stage regulator or using the power inflator excessively. If a regulator
is allowed to free-flow at depth for as little as five seconds, or if a BC or dry suit
power inflator is used excessively, freeze-up may occur.

Therefore, the following precautions specific to ANU approved cold water SCUBA
regulators shall be taken:
n Single-hose regulators should be kept in a warm place before diving.
n Test the regulator in a warm place, then refrain from breathing it until
submerging.

CHAPTER 11 — Ice and Cold Water Diving Operations

11-3

n While on the surface, the regulator should remain submerged and the diver
should refrain from breathing from the regulator until submerged.
n The diver’s time on the surface should be kept to a minimum.
n If water needs to be purged from the mouthpiece, the diver should do so by
exhaling into it.
11‑2.4.1

Special Precautions. A full face mask fitted with a demand mode regulator and

ambient breathing valve (ABV) is highly recommended to increase diver comfort
and safety. It is extremely important that extra scrutiny is given to regulator
maintenance used for cold water diving, including over bottom pressure settings.
Extra precautions must also be taken to make sure that SCUBA cylinders are
completely dry inside, that moisture-free air is used, and that the regulator is
thoroughly dried prior to use.

11‑2.4.2

Redundant Air Sources. Where water temperature is 37 degrees and colder, one

of the following three configurations shall be used:

1. Two single SCUBA bottles, each with its own K or J¬valve and first stage

regulator. Each first stage regulator will supply a harness mounted non-return
manifold block. The manifold block will supply an ANU approved FFM and
cold water second stage regulator.
The non-return manifold block will prevent a backflow of air in the event of
an air loss. The affected cylinder valve must be secured as quickly as possible.
Only in the event of FFM regulator freeze up will the diver have to remove the
FFM to breathe from the second stage regulator.

2. Twin SCUBA bottles fitted with a dual outlet common manifold containing

an interconnecting isolation valve and two separate first stage regulators. One
first stage regulator will supply the FFM and the other will supply an ANU cold
water approved second stage regulator. (Figure 11-1)

In the event of the FFM freeze up the diver will remove the FFM and shift to
the second stage regulator. The affected cylinder valve and the interconnecting
isolation valve should be secured as quickly as possible, if applicable.
3. Interspiro Divator Products (DP) using an HP surface-supplied air source

with diver-worn SCUBA providing air to the MK II or MK III regulator. In
this configuration, the diver will not have to remove the FFM to breathe from
the secondary air source. The transition from the primary air source to the
secondary air source is automatic in the event of a loss of primary air. A loss
of functional use of the FFM will require the diver to shift to the second stage
regulator.

Ensure air duration is calculated based on one cylinder only when planning dives
with configurations one or two.

11-4

U.S. Navy Diving Manual — Volume 2

11-2.5

Life Preserver. The use of life preservers with CO2 actuation is prohibited only

when diving under ice. The accidental inflation of a life preserver will force the
diver upward and may cause a collision with the undersurface of the ice. Should the
diver be caught behind a pressure ridge or other subsurface ice structure, recovery
may be difficult even with tending lines. Also, the exhaust and inlet valves of the
variable volume dry suit (VVDS) will be covered if a life preserver is worn. In the
event of a dry suit blow-up, the inability to reach the exhaust dump valve could
cause rapid ascent and collision with the surface ice.
11-2.6

Face Mask. The diver’s mask may show an increased tendency to fog in cold

water. An antifog solution should be used to prevent this from occurring. Saliva
will not prevent cold water fogging.

11-2.7

SCUBA Equipment. The minimum equipment required by every Navy SCUBA

diver for under-ice opera­tions consists of:
n Wet suit/variable volume dry suit

n Approved cold water open-circuit SCUBA or closed-circuit UBA, see ANU
n Face mask or approved Full Faced Mask, see ANU (Mask fitted with ABV is
preferred)
n Weights as required
n Life Preserver or BC if not wearing a VVDS.
n Knife and scabbard
n Swim fins
n Wrist watch
n Depth gauge
n Submersible SCUBA bottle pressure gauge
n ANU approved harness
n Lifelines/tending line/communication rope
n Stainless Steel Ice Screws
n Strobe Light /GLO-TOOB
A variety of special equipment, such as underwater cameras and lift bags, is avail­
able to divers. However, the effect of extreme cold on the operation of special
equipment must be ascertained prior to use.
11-2.8

Surface-Supplied Diving System (SSDS) Considerations. SSDS may be

required because of prolonged bottom times, depth requirements, and complex
communications between topside and diver. Using SSDS in ice-covered or cold
water requires detailed operations planning. Extensive logistics to support an
elaborate dive station include vital considerations such as; thermal protection for
personnel and the recompression chamber, hot water heating equipment, SSDS

CHAPTER 11 — Ice and Cold Water Diving Operations

11-5

cold climate modification, and personnel increases. The hot water shroud shall be
used with KM-37 for cold water diving. Consult the applicable technical manual
for necessary information on the use of the hot water shroud.
11‑2.8.1

Advantages and Disadvantages of SSDS.

The advantages of using SSDS are:
n Configuration supports bottom-oriented work.
n Hot water suit and VVDS offer diver maximum thermal and environmental
protection.
n Gas supply allows maximum duration to the maximum depth limits of diving.
The disadvantages of using SSDS are:
n Air console may freeze up.
n Low-pressure compressors do not efficiently remove moisture from the air
which may freeze and clog filters or fracture equipment. This is more likely
when the water is very cold and the air is warm. Banks of high-pressure cylin­
ders may have to be used.
n Buildup of air or gas under the ice cover could weaken and fracture thin ice,
endangering tenders, other topside personnel, and equipment.
n Movement of ice could foul or drag diver’s umbilical.
n Battery life of electronic gear is severely reduced.
n Carbon dioxide removal recirculator components may have to be heated.
n Decompression under extreme cold conditions may be dangerous due to water
temperature, ice movement, etc.
n Umbilicals are rigid and difficult to maneuver.
n Failure of hot water heater during in-water decompression must be considered
during operational planning.
11‑2.8.2

11-6

Effect of Ice Conditions on SSDS. Ice conditions can prevent or severely affect
surface-supplied diving. In general, the ice field must be stationary and thick
enough to support the dive station and support equipment. If the dive must be
accomplished through an ice floe, the floe must be firmly attached to land or a
stable ice field. Severe ice conditions seriously restrict or prohibit surface-supplied
diving through the ice (i.e., moving, unstable ice or pack ice and bergs, and deep
or jagged pressure ridges could obstruct or trap the diver). In cases where a diver

U.S. Navy Diving Manual — Volume 2

is deployed from a boat in a fixed mooring, the boat, divers, and divers’ umbilicals
must not be threatened by moving ice floes.
11-2.9

Suit Selection. Custom wet suits designed for cold water diving, VVDS, and

hot water suits have all been used effectively for diving in extremely cold water.
Each has advantages and disadvantages that must be considered when planning a
particular dive mission. All suits must be inspected before use to ensure they are in
good condition with no seam separations or fabric cuts.
11‑2.9.1

Wet Suits. Custom wet suits have the advantages of wide availability, simplicity

and less danger of catastrophic failure than dry suits. Although the wet suit is not
the equip­ment of choice, if used the following should be considered:
n The wet suit should be maintained in the best possible condition to reduce
water flushing in and out of the suit.
n Wearing heavy insulating socks under the boots in a wet suit will help keep feet
warm.
CAUTION

11‑2.9.2

The wet suit is only a marginally effective thermal protective measure,
and its use exposes the diver to hypothermia and restricts available
bottom time. The use of alternative thermal protective equipment should
be considered in these circumstances.
Variable Volume Dry Suits. Variable volume dry suits provide superior thermal

protection to the surface­-supplied or SCUBA diver in the water and on the surface.
They are constructed so the entry zipper or seal and all wrist and neck seals are
waterproof, keeping the interior dry. They can be inflated from a low-pressure air
source via an inlet valve. Air can be exhausted from the suit via a second valve,
allowing excellent buoyancy control. The level of thermal protection can be varied
through careful selection of the type and thickness of long underwear. However,
too much underwear is bulky and can cause overheating, sweating, and subsequent
chilling of the standby diver.
Dry suit disadvantages are increased swimmer fatigue due to suit bulk, possible
malfunction of inlet and exhaust valves, and the need for additional weights for
neutral buoyancy. Furthermore, blow-up may occur while the diver is horizontal
or if the diver inverts in the water column as air migrates to the lower extremities.
Use of ankle weights can somewhat mitigate this hazard. A parting seam or zipper
could result in a dramatic loss of buoyancy control and thermal shock.
The dry suit is an essential component of cold water diving because of its superior
thermal protection. When using a VVDS, a BC or life preserver is not required
because of the ability to control buoyancy with the dry suit. However, use of a
pony bottle for suit inflation is highly recommended when diving SCUBA due to
the limited air supply.

CHAPTER 11 — Ice and Cold Water Diving Operations

11-7

Figure 11‑2. Ice Diving with SCUBA in Dry Suits and AGA Divator FFM SCUBA.

CAUTION

11‑2.9.3

Prior to the use of variable volume dry suits and hot water suits in cold and
ice-covered waters, divers shall be trained in their use and be thoroughly
familiar with the operation of these suits.
Extreme Exposure Suits/Hot Water Suits. Hot water suits provide excellent
thermal protection. If their use can be supported logistically, they are an excellent
choice whenever bottom times are lengthy. They are impractical for use by standby
divers exposed on the surface if the flow of hot water flowing through the suit
cannot be regulated.

A hot water system failure can be catastrophic for a diver in very cold water since
the hot water is a life support system under such conditions. Hot water temperature
must be carefully monitored to ensure that the water is delivered at the proper
temperature. When using the hot water suit, wet suit liners must be worn. The hose
on the surface must be monitored to ensure it does not melt into the ice. When
not in use, the heater and hoses must be thoroughly drained and dried to prevent
freezing and rupture.
11-2.10

Clothing. Proper planning must include protecting tenders and topside support

personnel from the environment. However, bulky clothing and heavy mittens
make even routine tasks difficult for topside personnel. Waterproof outer gloves
and boots may also be considered. Regardless of the type of clothing selected,
the clothing must be properly fitted (loosely worn), and kept clean and dry to
maximize insula­tion. In planning operations for such conditions, reduced efficiency
resulting in longer on-site time must be considered. Refer to the Polar Operations
Manual for complete information on thermal protection of support personnel and
equipment.

11-8

U.S. Navy Diving Manual — Volume 2

Figure 11‑3. DRASH Brand 10-man tent erected over dive hole cut in ice.
11-2.11

Ancillary Equipment. A detailed reconnaissance of the dive site will provide the

planner with informa­tion that is helpful in deciding what ancillary equipment is
required. Diving under ice will require special accessory equipment such as a line
with lights/strobes for under­water navigation, ice-cutting tools, platforms, engine
protection kits, and stainless steel ice screws, quick draw, and carabineers.
The method of cutting the hole through the ice depends on ice thickness and avail­
ability of equipment. Normally, two or more of the following tools are used: hand
ice chipper, ice handsaw, ice auger, chain saw, thermal ice cutter or blasting equip­
ment. In addition, equipment to lift the ice block, remove the slush, and mark the
hole is required. Sandbags, burlap bags, or pallets for the tenders to stand on are
also needed. Personal flotation devices should be worn when in close proximity of
an ice hole.
If there is a possibility of surface support personnel falling through the ice, float­
able work platforms, such as an inflated Zodiac boat, should be used. With such
flotation equipment, the operation could be continued or safely concluded if the ice
breaks up.
Gasoline and diesel engines must be cold-weather modified to prevent engine
freeze-up. Vibrations of engines running on the ice can be a problem and vibration
dampening platforms may be required.
11-2.12

Dive Site Shelter. The use of dive shelters is dependent on the severity of

the climate, remoteness of the site, and duration of the mission. Shelters can
range from small to large tents to steel sea­land vans, or elaborate insulated huts
transported to the site and erected from kits. Shelters should have storage areas for
dry items, a place for drying equipment, diver’s benches, flooring for insulation,

CHAPTER 11 — Ice and Cold Water Diving Operations

11-9

and heating and lighting. In an extremely cold and dry climate, fire and carbon
monoxide poisoning are ever present dangers. Periodic checks of all living and
working spaces with a carbon monoxide detector should be performed and fire
extinguishers shall be available in each shelter containing combustible material.
WARNING		

11-3

Use of kerosene or propane heaters not designated for indoor use or
internal combustion engines inside of shelters may lead to carbon
monoxide poisoning and death.

PREDIVE PROCEDURES
11-3.1

Personnel Considerations. The Dive Supervisor shall ensure all personnel are

properly trained in ice diving techniques and are familiar with this Chapter. The
Diving Supervisor shall restrict any person from diving who is not physically
fit or who is suffering from psychological stress (anxiety, claustrophobia, or
recklessness) of an ice dive.
11-3.2

Dive Site Selection Considerations. The selection of the dive site will depend

upon the purpose of the dive and the geographical environment of the area (ice
thickness, ice surface conditions, etc.). Additionally, the diving method chosen,
safe access routes, shelter location, emer­gency holes, and exposure of divers and
required support personnel will also have a bearing on site selection.
11-3.3

11-3.4

11-10

Shelter. When ice diving is conducted, a shelter should be erected as close as
possible to the diving site to reduce the probability of frostbite and equipment
freeze up as the diving scenario dictates (Figure 11-3). Normally a shelter/tent
of sufficient size as to not restrict the movement of tenders and placement of the
standby diver is placed directly over the dive hole, at a minimum, a windbreak
should be constructed. A shelter of modular tents and space heaters is ideal;
although precautions must be taken to ensure the ice beneath the shelter is not
weakened. Extreme caution must be used when diving for objects, such as downed
aircraft, that have fallen through the ice; the area around the original hole may be
dangerously weakened.
Entry Hole. Proper equipment should be used to cut a suitable hole or holes through
the ice in order to leave a clean edge around the hole. Using a sledgehammer to
break through the ice is not recommended as it will weaken the surrounding ice.
The hole should be a rectangle 6 feet by 3 feet, or a triangle with six-foot sides as
shown in Figure 11-2. The triangular hole is easier to cut and is large enough to
allow simultaneous exit by two divers. Slush and ice must be removed from the
hole, not pushed under the ice surface, as it could slip back and block the hole.
To assist exiting divers and improve footing for other team members on the ice
surface, sand, wooden pallets, and/or heavy duty burlap bags/matting should be
placed on the ice around the hole. Upon completing the dive, the hole must be
clearly marked to prevent anyone from falling in accidentally. When possible
(especially in populated areas), the pieces cut from the ice should be replaced to
speed up the refreezing process. Branches, sticks or something similar should be
placed protruding up from the ice to mark the hole.

U.S. Navy Diving Manual — Volume 2

Figure 11-4. Typical Ice Diving Worksite.

CHAPTER 11 — Ice and Cold Water Diving Operations

11-11

11-3.5

Escape Holes. Escape holes provide alternative exit points and aid in searching

for a lost diver. Downstream escape holes (at least a 3 foot by 3 foot square) or
emergency exit holes must be cut in the ice when diving in a river or bay where
there is a current or tidal stream.

11-3.6

Navigation Lines. A weighted line should be hung through the hole to aid the diver

in retaining his bearing and sense of direction. Suspending a light or preferably a
GLO-TOOB at the end of the line may be helpful, as well as attaching a series of
strobe lights to indicate depth. After locating the work site, a distance line should
be laid from the weighted line to the work site. Another method of aiding the diver
in keeping his bearings in clear water is to shovel off the snow cover on the ice
around the dive site in the form of a spoked wheel (see Figure 11-4). When the ice
and snow cover is less than 2 feet thick, the diver should be able to see the spokes
leading to the dive hole located at the center of the wheel. The wheel should be
appropriate for the work site; if conditions permit, a 60 - 100 foot diameter wheel
is recommended, also the addition of directional arrows in the spokes (pointing
towards the hole) have proven to be effective.

11-3.7

Lifelines. Tending lines are mandatory when diving under ice. A braided or

twisted polypropylene line has an advantage of floating up and away from the
diver and is available in yellow, white, and orange for high visibility. It is highly
recommended that the lifeline be marked at 10-foot intervals to allow the tender
and Diving Supervisor to estimate the diver’s position. Secure the ends of lifelines
topside (preferably with a stainless steel ice screw in the ice) but not to a vehicle,
shovel, first-aid box, or other portable equipment. Keep wet lifelines off bare ice to
prevent them from freezing to the surface (see Figure 11-2).
The lifeline is to be held by the tender at all times. However, the diver’s radial
position can only be roughly estimated. The dive team must be thoroughly familiar
with the procedures for lifeline tending in Chapter 8. The tender shall send and
receive line-pull signals from the diver in intervals not to exceed two minutes to
ensure lifeline is free and clear to the diver and still attached.

11-3.8

Equipment Preparation. The diver must wear a distress light or GLO-TOOB that

should be turned on upon entering the water. Divers should not be encumbered
with unnecessary equipment during cold water dives. Snorkels should be removed
and knives worn on the inside of the leg to help prevent the lifeline from snagging
on the diver’s equipment. Personnel, divers, and tenders must handle rubber
accessories such as masks and fins care­fully; extreme cold causes them to become
brittle.

11-4

OPERATING PRECAUTIONS

Normal diving procedures generally apply to diving in extremely cold environments.
However, the hazard of regulator freeze-up prescribes the use of a redundant air
source and mastery of buddy breathing procedures as described in Chapter 7. This
section outlines some of the precautions for operating in cold and ice-covered water.
11-12

U.S. Navy Diving Manual — Volume 2

11-4.1

General Precautions. General precautions for ice and cold water diving operations

include:

n Divers should be well rested, have a meal high in carbohydrates and protein,
and should not consume any alcohol. Alcohol dilates the blood vessels in the
skin, thus increasing body heat loss.
n Bathing is an important health measure to prevent infectious diseases preva­
lent in cold environments. If necessary, the body can be sponge-bathed under
clothing.
n After bathing, a soothing ointment or lotion should be applied to the skin to
keep it soft and protect it against evaporation caused by the dry air.
n Shaving and washing the face should be done in the evening because shaving
removes protective oils from the skin. Shaving too close can also remove some
of the protective layer of the skin, promoting frostbite.
n Paired dive partners are required when diving under ice. When diving
through the ice, the pair shall always be surface tended. The life-threatening
consequences of suit failure, regulator freeze-up or other equip­ment problems
make a solitary tended SCUBA diver particularly vulnerable.
n Divers must practice buddy breathing prior to the operation at the dive site
because of the increased possibility that buddy breathing will be required.
Proficiency in the process will minimize loss of valuable time during an
emergency.
n The standby diver should be kept warm until the Diving Supervisor determines
that the standby diver is needed. The life­line of the standby diver shall be twice
the length of the diver’s lifeline in order to perform a thorough circular search.
11-4.2

Ice Conditions. The inconsistency and dynamics of ice conditions in any particular
area can make diving operations extremely hazardous. The movement of ice floes
can be very significant over a relatively short period of time, requiring frequent
relocation of dive sites and the opening of new access holes in order to work a
fixed site on the sea floor. Diving from drifting ice or in the midst of broken free
ice is dangerous and should be conducted only if absolutely necessary.

Differential movement of surface and subsurface pressure ridges or icebergs could
close an access hole, sever a diving umbilical, and isolate or crush a diver. The
opening of a rift in the ice near a dive site could result in loss of support facilities
on the ice, as well as diver casualties.
11-4.3

Dressing Precautions. With a properly fitting suit and all seals in place, the diver
can usually be kept warm and dry for short periods in even the coldest water. When
dressing for an ice or cold water dive:

CHAPTER 11 — Ice and Cold Water Diving Operations

11-13

n Thermal protection suits should be checked carefully for fabric cuts and sepa­
rations. Thermal protection suits should expose only a minimum of facial area.
n Mittens, boots, and seals should prevent water entry, while causing no restric­
tion of circulation. Wearing a knitted watchcap under the hood of a dry suit
is effective in conserving body heat. With the cap pushed back far enough to
per­mit the suit’s face seal to seat properly, the head will be relatively dry and
comfortable.
11-4.4

On-Surface Precautions. While on the surface:

n Suited divers should be protected from overheating and associated perspiring
before entering the water. Overheating easily occurs when operating from a
heated hut, especially if diver exertion is required to get to the dive site. The
divers’ comfort can be improved and sweating delayed before entering the
water by cooling the divers face with a damp cloth and fanning every few min­
utes. Perspiration will dampen undergarments, greatly reducing their thermal
insulating capabilities.
n While waiting to enter the water, divers should avoid sitting on or resting their
feet on the ice or cold floor of a hut. Even in an insulated hut, the temperature
at the floor may be near freezing.
n Time on the surface with the diver suited, but relatively inactive, should be
minimized to prevent chilling of the diver. Surface time can also cool metal
components of the diving gear, such as suit valves and SCUBA regulators,
below the freezing point and cause the parts to ice up when the diver enters the
water. Dressing rehearsals prior to diving will help minimize surface delays.
n When operating from an open boat, heavy parkas or windbreakers should be
worn over the exposure suits.
n When operating at the surface in newly formed ice, care should be taken to
avoid cutting exposed facial skin. Such wounds occur easily and, although
painless because of the numbness of the skin, usually bleed profusely.
n Diving from a beach and without a support vessel should be limited to a dis­
tance that allows the divers to return to the beach if the suit floods.
n Extreme caution must be exercised when diving near ice keels in polar regions
as they will often move with tidal action, wind, or current. In doing so, they can
foul umbilicals and jeopardize the divers’ safety.
11-4.5

In-Water Precautions.

n Because severe chilling can result in impaired judgment, the tasks to be per­
formed under water must be clearly identified, practiced, and kept simple.
n A dive should be terminated upon the onset of involuntary shivering or severe
impairment of manual dexterity.
11-14

U.S. Navy Diving Manual — Volume 2

n If the exposure suit tears or floods, the diver should surface immediately,
regardless of the degree of flooding. The extreme chilling effect of frigid water
can cause thermal shock within minutes, depending on the extent of flooding.
n Divers and Diving Supervisors must be aware of the cumulative thermal effect
of repetitive diving. A thermal debt can accumulate over successive diving
days, resulting in increased fatigue and reduced performance. The progressive
hypothermia associated with long, slow cooling of the body appears to cause
significant core temperature drop before shivering and heat production begins.
n Lifelines contacting protrusions and projections from the ice bottom can imitate
line-pull signals and the tender must be able to distinguish the difference.
11-4.6

Postdive Precautions. Upon exiting cold water, a diver will probably be fatigued

and greatly susceptible to additional chilling:

n If a wet suit was worn, immediate flushing with warm water upon surfacing
will have a comforting, heat-replacing effect.
n Facilities must be provided to allow the diver to dry off in a comfortable, dry
and relatively warm environment to regain lost body heat.
n The diver should remove any wet dress, dry off, and don warm protective
clothing as soon as possible. Personnel should have warm, dry clothing,
blankets, and hot non­alcoholic, non-caffeine beverages containing sugar, i.e.,
warm lemonade or warm kool-aid available to them; the sugar can cause the
body to warm more rapidly.
11-5

EMERGENCY PROCEDURES
11-5.1

Lost Diver. A diver who becomes detached from the lifeline and cannot locate the

entrance hole should:

1. Ascend to the underside of the ice.
2. Remove weight belt and allow it to drop.
3. Thread an ice screw into underside of the ice (clip in with a quick-draw,

carabineer or similar device if available) to maintain position and prevent
fatigue.

4. Remain in a vertical position, to maximize vertical profile and thereby snag the

searching standby diver’s lifeline.

5. Watch for lifeline, and the lifeline of the standby diver and wait for the standby

diver to arrive. The lost diver SHALL NOT attempt to relocate the hole. The
diver must remain calm and watch for the standby diver.

11-5.2

Searching for a Lost Diver. As soon as the tender fails to get a response from the
diver, the tender must notify the Diving Supervisor immediately. These procedures
are to be implemented at once:

CHAPTER 11 — Ice and Cold Water Diving Operations

11-15

1. The Diving Supervisor shall immediately recall all other divers.
2. The Diving Supervisor must estimate the probable location of the lost diver by

assessing the diver’s speed and direction of travel.

3. As directed by the Diving Supervisor, the standby diver enters the water and

swims in the indicated direction, a distance equal to twice that believed to be
covered by the lost diver. The distance may be the full extent of the standby
diver’s lifeline since it is twice as long as the lost diver’s lifeline.

4. The tender must keep the standby diver’s lifeline taut.
5. The standby diver conducts a circular sweep.
6. When the lifeline snags on the lost diver, the standby diver swims toward the

diver signaling the tender to take up slack.

7. Upon locating the lost diver, the standby diver assists the diver back to the hole.
8. If the first sweep fails, it should be repeated only once before moving the search

to the most likely emergency hole, typically downstream from the primary
insertion location.

11-5.3

Hypothermia. When diving in cold water, hypothermia may predispose the

diver to decompression sickness. Hypothermia is an ever present danger in cold
climates and easily diagnosed. A thorough review of Section 3-10, Thermal
problems in diving, shall be conducted prior to cold weather operations. Profound
hypothermia may suppress the heartbeat and respiration to the point that the victim
appears dead. Resuscitation efforts should continue until the diver is re-warmed
and revives, the rescuers are unable to continue, or a physician has pronounced the
victim dead.

11-16

U.S. Navy Diving Manual — Volume 2

APPENDIX 2A

Optional Shallow Water Diving Tables
2A-1

Introduction. At the shallow depths typical of ship husbandry diving, a small
change in the diver’s maximum depth can make a significant difference in the
allowable no-decompression time. For example, at 35 fsw the no-decompression
time on air is 232 minutes; at 40 fsw it is only 163 minutes, more than an hour
less. When the diver’s maximum depth is accurately known at the beginning of the
dive, e.g., in ballast tank dives, or when continuous electronic depth recording is
available, e.g., with a decompression computer, use of a decompression table with
depth listed in one-foot increments rather than five-foot increments may result in a
significant gain in no-decompression time.

Shallow Water Diving Tables covering the depth range of 30–50 fsw in onefoot increments are given in Tables 2A-1 and 2A-2. These tables are simply an
expansion of Tables 9-7 and 9-8 and the rules for using Tables 2A-1 and 2A-2 are
identical to the rules for using Tables 9-7 and 9-8. These Shallow Water Diving
Tables are optional. They may be used instead of Tables 9-7 and 9-8 if they offer
a gain in no-decompression time. The Optional Shallow Water Diving Tables are
most suited to ship husbandry diving, but can be used in other shallow air diving
applications as well.

APPENDIX 2A — Optional Shallow Water Diving Tables

2A-1

Table 2A‑1. No-Decompression Limits and Repetitive Group Designators for Shallow Water Air NoDecompression Dives.
Repetitive Group Designation

Depth
(fsw)

No-Stop
Limit (min)

A

B

C

D

E

F

G

H

I

J

K

L

M

N

O

Z

30

371

17

27

38

50

62

76

91

107

125

145

167

193

223

260

307

371

31

334

16

26

37

48

60

73

87

102

119

138

158

182

209

242

282

334

32

304

15

25

35

46

58

70

83

98

114

131

150

172

197

226

261

304

33

281

15

24

34

45

56

67

80

94

109

125

143

163

186

212

243

281

34

256

14

23

33

43

54

65

77

90

104

120

137

155

176

200

228

256

35

232

14

23

32

42

52

63

74

87

100

115

131

148

168

190

215

232

36

212

14

22

31

40

50

61

72

84

97

110

125

142

160

180

204

212

37

197

13

21

30

39

49

59

69

81

93

106

120

136

153

172

193

197

38

184

13

21

29

38

47

57

67

78

90

102

116

131

147

164

184

39

173

12

20

28

37

46

55

65

76

87

99

112

126

141

157

173

40

163

12

20

27

36

44

53

63

73

84

95

108

121

135

151

163

41

155

12

19

27

35

43

52

61

71

81

92

104

117

130

145

155

42

147

11

19

26

34

42

50

59

69

79

89

101

113

126

140

147

43

140

11

18

25

33

41

49

58

67

76

87

98

109

122

135

140

44

134

11

18

25

32

40

48

56

65

74

84

95

106

118

130

134

45

125

11

17

24

31

39

46

55

63

72

82

92

102

114

125

46

116

10

17

23

30

38

45

53

61

70

79

89

99

110

116

47

109

10

16

23

30

37

44

52

60

68

77

87

97

107

109

48

102

10

16

22

29

36

43

51

58

67

75

84

94

102

49

97

10

16

22

28

35

42

49

57

65

73

82

91

97

50

92

9

15

21

28

34

41

48

56

63

71

80

89

92

2A-2

U.S. Navy Diving Manual — Volume 2

Table 2A‑2. Residual Nitrogen Time Table for Repetitive Shallow Water Air Dives.
Locate the diver’s repetitive group designation from his previous dive along the diagonal line
above the table. Read horizontally to the interval in which the diver’s surface interval
lies.

* Dives following surface intervals longer than
this are not repetitive dives. Use actual
bottom times in the Air Decompression
Tables to compute decompression
for such dives.

ng

up

ive

o
Gr
K

:10
:52
:53
1:44
1:45
2:37
2:38
3:29
3:30
4:21
4:22
5:13

:10
:52
:53
1:44
1:45
2:37
2:38
3:29
3:30
4:21
4:22
5:13
5:14
6:06

:10
:52
:53
1:44
1:45
2:37
2:38
3:29
3:30
4:21
4:22
5:13
5:14
6:06
6:07
6:58

r
te

D

n

eI

c
rfa

E
F

G
H

I
J

it
et

p

Re

Be

l

va

Su

i
nn

gi

at

of

:10
:52
:53
1:44
1:45
2:37
2:38
3:29
3:30
4:21
4:22
5:13
5:14
6:06
6:07
6:58
6:59
7:50

:10
:52
:53
1:44
1:45
2:37
2:38
3:29
3:30
4:21
4:22
5:13
5:14
6:06
6:07
6:58
6:59
7:50
7:51
8:42

:10
:52
:53
1:44
1:45
2:37
2:38
3:29
3:30
4:21
4:22
5:13
5:14
6:06
6:07
6:58
6:59
7:50
7:51
8:42
8:43
9:34

:10
:52
:53
1:44

:10
:52
:53
1:44
1:45
2:37

:10
:52
:53
1:44
1:45
2:37
2:38
3:29

:10
:52
:53
1:44
1:45
2:37
2:38
3:29
3:30
4:21

Z

O

N

M

L

30

372

308

261

224

194

168

146

126

108

92

77

31

334

282

243

210

183

159

139

120

103

88

74

32

305

262

227

198

173

151

132

115

99

85

33

282

244

213

187

164

144

126

110

95

34

262

229

201

177

156

138

121

105

35

245

216

191

169

149

132

116

36

231

204

181

161

143

126

37

218

194

173

154

137

38

207

185

165

148

39

197

177

158

40

188

169

41

180

42

L
M
N
O
Z

:10
:52

B
C

Next, read vertically downward to the new repetitive group designation.
Continue downward in this same column to the row that represents
the depth of the repetitive dive. The time given at the intersection
is residual nitrogen time, in minutes, to be applied to the
repetitive dive.

:10
1:16
:56
2:11
1:48
3:03
2:40
3:55
3:32
4:48
4:24
5:40
5:17
6:32
6:09
7:24
7:01
8:16
7:53
9:09
8:45
10:01
9:38
10:53
10:30
11:45
11:22
12:37
12:14
13:30

:10
2:20 *
1:17
3:36 *
2:12
4:31 *
3:04
5:23 *
3:56
6:15 *
4:49
7:08 *
5:41
8:00 *
6:33
8:52 *
7:25
9:44 *
8:17
10:36 *
9:10
11:29 *
10:02
12:21 *
10:54
13:13 *
11:46
14:05 *
12:38
14:58 *
13:31
15:50 *

A

:10
:52
:53
1:44
1:45
2:37
2:38
3:29
3:30
4:21
4:22
5:13
5:14
6:06
6:07
6:58
6:59
7:50
7:51
8:42
8:43
9:34
9:35
10:27

D

C

B

A

63

51

39

28

18

61

49

38

27

17

71

59

47

36

26

17

81

69

57

46

35

25

16

91

78

66

55

44

34

25

16

101

88

75

64

53

43

33

24

15

111

98

85

73

62

51

41

32

23

15

122

107

94

82

70

60

50

40

31

23

14

132

117

103

91

79

68

58

48

39

30

22

14

142

127

113

100

88

77

66

56

47

38

29

21

14

152

136

122

109

97

85

74

64

55

45

37

29

21

13

163

146

132

118

105

93

82

72

62

53

44

36

28

20

13

173

156

141

127

114

102

91

80

70

61

52

43

35

27

20

13

43

166

150

136

123

110

99

88

78

68

59

50

42

34

26

19

12

44

160

145

131

119

107

96

85

75

66

57

49

41

33

26

19

12

45

154

140

127

115

104

93

83

73

64

56

48

40

32

25

18

12

46

149

136

123

111

101

90

81

71

63

54

46

39

32

25

18

12

47

144

131

119

108

98

88

78

70

61

53

45

38

31

24

18

11

48

139

127

116

105

95

85

76

68

60

52

44

37

30

24

17

11

49

135

123

112

102

92

83

74

66

58

51

43

36

30

23

17

11

50

131

120

109

99

90

81

73

65

57

49

42

35

29

23

17

11

Dive
Depth

K
J
I
H
G
F
E
Repetitive Group at the End of the Surface Interval

:10
:52
:53
1:44
1:45
2:37
2:38
3:29
3:30
4:21
4:22
5:13
5:14
6:06
6:07
6:58
6:59
7:50
7:51
8:42
8:43
9:34
9:35
10:27
10:28
11:19

:10
:55
:53
1:47
1:45
2:39
2:38
3:31
3:30
4:23
4:22
5:16
5:14
6:08
6:07
7:00
6:59
7:52
7:51
8:44
8:43
9:37
9:35
10:29
10:28
11:21
11:20
12:13

Residual Nitrogen Times (Minutes)

APPENDIX 2A — Optional Shallow Water Diving Tables

2A-3

PAGE LEFT BLANK INTENTIONALLY

2A-4

U.S. Navy Diving Manual — Volume 2

APPENDIX 2B

U.S. Navy Dive Computer
2B-1

INTRODUCTION

Navy Dive Computers (NDCs) are wrist
or lanyard mounted devices that provide
real-time decompression guidance to the
user based on the user’s preceding dive
history. NDC use allows great flexibility in
diving, increasing the amount of available
bottom time by compensating for time spent
at depths shallower than the maximum
achieved depth, the depth that must be used
to apply traditional decompression tables for
square dives. Five distinct NDC variants,
one of which is shown in Figure 2B-1, are
currently authorized on the ANU for use in
different types of diving ranging from open
circuit air (N2-O2) to closed circuit N2-O2 and
He-O2.
2B-1.1

Purpose. This appendix provides general

guidelines and procedures for NDC diving
operations. For detailed physical operation
and maintenance instructions, see the
associated NDC’s approved Technical
Manual. For operational planning, refer to
Chapter 6.

2B-1.2

Figure 2B-1. Navy Dive Computer.

Scope. This chapter covers NDC general characteristics, dive procedures, and

unique decompression aspects for the use of the NDC in lieu of standard tables for
various UBAs. The specific NDC characteristics and set points are contained in
the respective O&M manual. Multi-Level diving unique to Naval Special Warfare
under its own procedural guidance is exempt from the requirements of this chapter.
2B-2

PRINCIPLES OF OPERATION

The NDC provides real time decompression guidance to the diver underwater and
displays the following vital information:
n Depth
n Temperature
n No-decompression time remaining before incurring stops

APPENDIX 2B — U.S. Navy Dive Computer

2B-1

n Decompression stop depth and time at stop
n Total remaining decompression time
n TBT from left surface
n Ascent rate bar graph with warnings
n Current set point
2B-2.1

Definitions:
1. Set point: The prevailing diver inspired oxygen fraction or oxygen partial

pressure assumed by the NDC. The NDC set point matches the specific
performance parameters of the UBA which the NDC supports. Some NDC
variants incorporate automatic depth-dependent transition set points. The NDC
set point is displayed in terms of the following set point designators:

n f21: set point designator for constant inspired O2 fraction of 0.21 (21% O2).
The designator for open circuit air is f21.
n p0.7 or p1.3: set point designators for constant inspired O2 partial pressures
(ppO2)of 0.7 or 1.3 atm, respectively. Used with NDCs for EC-UBA diving.
2. Ceiling: The deepest depth of any required decompression stop indicated by a

NDC. The prescribed decompression stop must not be violated, hence the term
“ceiling”.

3. Desaturation Time: Remaining time on surface before a subsequent dive is no

longer considered a repetitive dive; time before an allowed ascent to altitude.
Varies from 1 to 24 hours depending on the residual inert gas loading upon
surfacing from the last dive and the time elapsed since surfacing from the last
dive.

4. Governing NDC: The NDC with the most conservative indication of the

prevailing decompression obligation in a buddy pair or group of divers that
must follow the same decompression schedule. Example: the computer with
the shortest remaining no-stop time if all computers are no-stop or the computer
with the longest indicated remaining decompression stop time; in post-dive
surface mode, the computer with the longest desaturation time.

2B-2.2

Function. All NDC variants operate the Thalmann Exponential-Linear MK

15/16 Decompression Model (EL-MK 15/16 DCM), but the different variants are
configured with different factory software settings to tailor algorithm operation for
the type of diving supported by the NDC. The NDCs have no user configurable
settings with the exception of the AIR III-79. This variant has programming mode
enabled, which allows divers access to the pre-dive prediction mode. Refer to the
AIR III-79 O&M Manual for further information on programming mode function.
Each NDC updates the algorithm with a depth and time sample every second and
uses the algorithm output to support a variety of functions including countdown
of time remaining in No-Decompression status or countdown of time required at
decompression stops.

2B-2

U.S. Navy Diving Manual — Volume 2

2B-2.3

Safety. It is critical divers monitor their NDCs every two to three minutes

throughout the dive. Divers must ensure they are breathing the appropriate gas for
the set point indicatedon the NDC.
After ascent to a depth shallower than a prescribed decompression stop depth, the
NDC will count down the omitted stop time faster than at the omitted stop depth
because the inert gas partial pressure at the shallower depth is less than at the
missed stop depth. The NDC will not apply the required penalty to compensate for
omitted decompression. Diving supervisors must check NDC status for omitted
decompression immediately upon diver surfacing.
Example: A diver on open circuit air surfaces by omitting a :04 stop at 10 fsw.

After two minutes on the surface, the stop clears, and all warnings disappear.

Warning		

The NDC variant used must match the rig/diluent/dive method being
performed. Catastrophic decompression sickness could result if the
wrong NDC is selected.

Each diver must use the same NDC throughout any given series of dives. A clean
diver who replaces a diver unable to make a repetitive dive should use the NDC of
the diver that he is replacing. This NDC will prescribe unnecessarily conservative
decompression guidance for the clean diver, but will serve as a backup for the
repetitive diver should that diver’s NDC fail (see paragraph 2B-4.1). Any diver that
loses the data on his NDC before desaturation is complete shall not dive within 24
hours of his last reached surface time (His inert gas level is unknown).
2B-2.4

Advantages. The NDC credits the diver for time spent at depths shallower than

the maximum depth of the dive. This greatly increases bottom time.

Example 1. A ships husbandry diver after :120 at 25 fsw drops a tool to the bottom

at 58 fsw. The standard table would not allow the diver to descend to retrieve the
tool since the table would be a 60 fsw for :120, a prohibited exceptional exposure
dive. An NDC, however, would show almost unlimited no-decompression time
remaining after :120 at 25 fsw, and allow the diver to descend, retrieve the tool,
and return to work at the 25 fsw worksite. NDC use would eliminate a need to swap
divers to retrieve the tool.

Example 2. A diver inspecting a submerged buoy must examine the anchor system
at 130 fsw, then perform :30 of maintenance on the buoy itself at 50 fsw. A typical
square air table would give the diver a total of :10 of no-decompression bottom
time, including time at the 50 fsw worksite. In comparison, after a :10 anchor
inspection at 130 fsw, the NDC would allow the diver almost an hour of remaining
no-decompression time upon ascent to the 50 fsw worksite.
2B-2.5

Disadvantages. The diving supervisor is not in direct control of the diver’s

decompression status.

APPENDIX 2B — U.S. Navy Dive Computer

2B-3

2B-2.6

Use. Table 2B-1 contains the operational characteristics of the currently approved

NDCs.

Table 2B-1. NDC Characteristics.

NDC / Color
(Note 1)

NSW III
Black

NSW III 50/12 1.3 Air
Black

Inert Gas /
UBA

N2O2
-EC-UBA
-Air

N2O2
-EC-UBA
-Air

Depth Limit

Total
Decompression
Time Limit
(Note 2)

f21, D < 78 fsw
p0.7, D ≥ 78 fsw

150 fsw

15 minutes

during descent:
f21, D < 50 fsw;
p1.3, D ≥ 50 fsw
during ascent;
p1.3, D > 12 fsw
f21, D ≤ 12 fsw

150 fsw

Note 3

150 fsw

40 minutes

Set Point, Depth (D)

EOD III
Grey

N2O2
-EC-UBA

during descent:
p0.7, D < 34 fsw;
p1.3, D ≥ 34 fsw
during ascent;
p1.3, D > 12 fsw
p0.7, D ≤ 12 fsw

AIR III-79
Yellow (Note 4)

N2O2
-Air

f21 throughout

190 fsw

15 minutes

HeO2
-EC-UBA

during descent:
p0.7, D < 32 fsw;
p1.3, D ≥ 32 fsw
during ascent;
p1.3, D > 12 fsw
p0.7, D ≤ 12 fsw

200 fsw

Note 3

NSW HE III 200-1.3
Blue

Notes:
1.

A dive series started on an NDC variant and breathing medium (N2-O2 or He-O2) must stay on that
variant until the Desaturation time from that dive/series of dives is expired.

2.

Limits are based on the exceptional exposure lines from standard tables, oxygen exposure limits, or
limits imposed by other approved procedures. Most NDC dives have much longer in-water times than
table dives, therefore increasing the overall risk of the dive. The goal of the NDC is to significantly
reduce or remove the need for in water decompression stops by using its flexibility to stay NoDecompression.

3.

In accord with approved NSW multi-level diving procedures.

4.

Legacy NDCs designated “AIR III” are governed by AIR III-79 procedures.

2B-4

U.S. Navy Diving Manual — Volume 2

2B-3

DIVING
2B-3.1

Pre-Dive. Maintenance and pre-dive checks should be completed IAW the

appropriate NDC O&M manual. Dive supervisors should check for the following:
n Correct NDC for dive method being performed
n NDC is paired to the diver if performing a repetitive dive
n NDC is on
n Battery status is within O&M recommendations
n NDC is in surface mode

n NDC is attached to the diver or a piece of equipment that would not be
ditched
n If programming mode is enabled (AIR III-79 only) verify conservatism is set
to zero.
2B-3.2

Dive. General bottom time planning for single dives may be undertaken using the

Air tables in Chapter 9 or EC-UBA tables in Chapter 16. Once the NDC dive
starts, however, the dive supervisor will not know the diver’s remaining nodecompression or decompression time unless in communication with the diver.
For ease of dive planning, dive supervisors may elect to limit the maximum depth
and remaining no-decompression time, or the maximum time at a specific ceiling.
This allows the divers flexibility in conducting underwater tasks throughout the
water column rather than being held to an arbitrary square table. For buddy pair, or
group diving, the governing NDC sets the limitations.

Example: A dive supervisor for a square table dive would brief, “no deeper than

60 fsw, no longer than 50 minutes”. A dive supervisor for an NDC dive would
brief, “no deeper than 60 fsw, no less than 3 minutes remaining no-decompression
time,”or alternatively, “leave bottom after incurring no more than :05 of total
decompression time”.
Most NDCs do not transition to dive mode until a depth of 2-5 fsw is reached. If
the NDC does not transition by 10 fsw, the diver must abort the dive and surface.
If the faulty NDC is a repetitive NDC, the diver assigned that NDC shall not dive
until a minimum of 24 hours has elapsed following his last reached surface time.
Divers must ensure they are breathing the mix displayed by the NDC to avert
omitting significant decompression or being directed to perform an unnecessarily
long decompression. NDCs are designed to transition set points within 2 fsw of
their respective transition depths. A diver with an NDC that does not transition shall
follow the same EP and abort criteria as a diver with a UBA that fails to transition

APPENDIX 2B — U.S. Navy Dive Computer

2B-5

2B-3.3

Ascent. Prior to leaving bottom, determine the governing NDC.

Divers shall monitor the NDC ascent rate indicator to ensure they do not exceed the
30 fpm ascent rate limit. The NDC ascent rate indicator is a bar graph as illustrated
in Figure 2B-2. At any point in time, the graph is filled to a level that indicates the
current ascent rate. The bars of the graph flash as a warning when the ascent rate
exceeds 30 fpm. In the event of such a warning, the ascent rate should be slowed
until the warning flashes cease.

A
S
C
E
N
T
.

50 TO 60 FEET PER MINUTE
40 TO 49 FEET PER MINUTE
30 TO 39 FEET PER MINUTE
20 TO 29 FEET PER MINUTE
10 TO 19 FEET PER MINUTE

Figure 2B-2. NDC Ascent Rate Bar Graph showing ascent
rate of greater than 30 fpm. Text included here for explanatory
purposes is not included in the actual NDC display.

2B-3.4

Decompression. Each NDC variant is designed to accommodate the set points of

a particular UBA.

The governing NDC shall be used to determine decompression. It is possible that a
different NDC can become the governing NDC at a shallower stop. All NDCs must
be checked upon reaching and before leaving any stop.
n Ascend to the governing NDC ceiling and complete the required stop time.
n Check all NDCs cleared the ceiling.
n Ascend to the next ceiling. Determine governing NDC.
n Prior to leaving last stop, ensure all NDCs are back to No-Decompression.
n Divers pass NDC information to dive supervisor upon surfacing.
Caution		
2B-3.5

Divers should avoid strenuous exercise during decompression.
Post-Dive. Any diver who has exceeded the limits of the NDC or had significant

UBA issues that caused inspired ppO2 to fall more than 0.15 atm below pO2 set
points shall be observed for signs of DCS. Such a diver requires observation after
surfacing, but need not be treated unless symptoms of decompression sickness
occur.

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U.S. Navy Diving Manual — Volume 2

NDC post dive maintenance is performed IAW the NDC operation and maintenance
manual. Divers shall keep their NDCs with them or in a marked place to prevent
their use by different divers before desaturation time is complete.
2B-3.6

Time to Fly/Ascent to Altitude. The NDC displays desaturation time. This is the

time until algorithm compartments are back to baseline. Any diver that loses the
data on his NDC before desaturation is complete shall not fly until a minimum of
24 hours has elapsed following his last reached surface time.

2B-3.7

Repetitive Diving. The NDC desaturation time applies to repetitive dives. A dive

undertaken with an NDC showing remaining desaturation time is considered to
be a repetitive dive. Only no-decompression repetitive dives are authorized. A
diver may make an unlimited number of dives provided that all dives in the series
remain no-decompression. A diver planning to conduct an NDC decompression
dive must wait until the desaturation time on their NDC is clear prior to making
the dive.
A diver conducting an NDC repetitive dive may dive with a clean NDC diver
provided they are diving the same rig/mix/NDC variant. In this case, the repetitive
NDC would be the governing NDC.

2B-4

DIVING ISSUES/EPs

UBA specific EPs must be followed. The following EPs pertain only to the
decompression requirements in NDC dives that differ from those for dives
undertaken with standard square tables.
2B-4.1

Loss of NDC:
1. Abort dive.
2. Use the buddy diver NDC as the governing NDC.
3. In the event of a single diver losing his NDC, or both NDCs failing, the

diver(s) must weigh the risk of DCS from immediately surfacing. Obviously
if the diver(s) know they are well inside no-decompression limits, they should
abort the dive and ascend following the slowest bubble. The diver(s) should be
observed for one hour after surfacing.

2B-4.2

Asymptomatic Omitted Decompression. Procedures

for management of
asymptomatic omitted decompression are summarized in Table 2B-2. More
detailed procedures for specific types of cases are given in Sections 2B-4.2.1
through 2B-4.2.3.

APPENDIX 2B — U.S. Navy Dive Computer

2B-7

Table 2B-2. Initial Management of Asymptomatic Omitted Decompression for NDC Dives.

Deepest
Decompression
Stop Omitted

Any

Inadvertent
Surfacing from
Last Stop

Action
In-water
Status

Diver in
water

Surface
Interval

Without
surfacing

Chamber Available

No Chamber
Available

Descend 10 fsw deeper
than missed stop; perform
stops every 10 fsw for the
longer of :10 or the time
required to remain 10 fsw
deeper than ceiling
(note 1)

Descend 10 fsw deeper
than missed stop; perform
stops every 10 fsw for the
longer of :10 or the time
required to remain 10 fsw
deeper than ceiling
(note 1)

Descend to missed stop;
manually double stop
time
Surfaced

Any

-or-

Descend to missed stop;
manually double stop
time

TT5 for SI <:05
TT6 for SI >:05

Inadvertent
Surfacing from
Deeper than 20
fsw with Multiple
Stops Missed

TT5 for <:30 missed
Surfaced

Any
TT6 for >:30 missed

Descend 10 fsw deeper
than missed stop;
perform stops every 10
fsw for the longer of :10
or the time required to
remain 10 fsw deeper
than ceiling (note 1)

Notes:
1.

When diving p1.3 EC-UBA, the diver may elect to descend to re-transition the EC-UBA and/or NDC to
1.3 ppO2 before returning to the missed stop.

2B-4.2.1

In water stops missed without surfacing:
1. Descend as necessary to transition EC-UBA or NDC set points to match.
2. Travel to a depth 10 fsw deeper than the depth of the missed stop and stop for

a minimum of :10.

3. Continue decompression to surface with a stop every 10 fsw for the longer of

:10 or the time required to remain 10 fsw deeper than the indicated ceiling.

4. Observe diver for one hour after surfacing.
2B-4.2.2

Inadvertent surfacing with missed last or only stop:
1. Stay on EC-UBA if applicable, while on surface.
2. Note remaining stop time indicated on NDC.
3. Descend as necessary to transition EC-UBA or NDC set points to match.

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U.S. Navy Diving Manual — Volume 2

4. Travel to missed stop and stop for double the previously noted remaining stop

time.

5. Observe diver for one hour after surfacing.
2B-4.2.3

Inadvertent surfacing with multiple missed stops:
1. Stay on EC-UBA, if applicable, while on surface.
2. Descend as necessary to transition EC-UBA or NDC set points to match.
3. Travel to depth 10 fsw deeper than the depth of the missed stop and stop for a

minimum of :10.

4. Continue decompression to surface with a stop every 10 fsw for the longer of

:10 or the time required to remain 10 fsw deeper than the indicated ceiling.

5. Observe diver for one hour after surfacing.
2B-4.3

In-Water DCS. If chamber immediately available, surface and treat on a minimum

of TT6 IAW Chapter 18.

If a chamber is not immediately available:
1. If diving a p1.3 UBA and the afflicted diver’s UBA or NDC has transitioned to

p0.7 mode at its shallow transition depth, descend deep enough to transition the
UBA and NDC to p1.3 mode. Travel to a depth 10 fsw deeper than the current
stop depth and assess the afflicted diver for relief of symptoms. Descent to a
maximum depth 20 fsw deeper than the current stop depth may be completed
if symptoms are not relieved.

2. Remain at depth of relief for :10.
3. Take a stop every 10 fsw for :10 or the displayed stop time, whichever is longer.

Stops may be lengthened beyond :10 as necessary to control symptoms.

4. Complete the last stop at 20 fsw for a minimum of :10 or the displayed stop

time, whichever is longer.

5. Transport to recompression chamber. If diver remains asymptomatic, administer

a TT5. If diver is symptomatic, administer a TT6 IAW Chapter 18.

2B-4.4

Exceeded limits (unplanned exceptional exposure). The NDCs were designed

and limited to different depth parameters based on the estimated risks of DCS
associated with dive profiles allowed within the limits. Exceeding the set
limitations of the NDC given in Table 2B-1 may cause the diver to incur a much
higher risk of DCS than is acceptable. If the limits are exceeded:

1. Follow decompression as prescribed by the NDC.
2. Observe the diver on the surface for one hour.
3. The diver should be accompanied by a person with knowledge of diving-related

illnesses for a period of six hours after the dive.

4. Treat any symptoms as original symptoms IAW Chapter 18.

APPENDIX 2B — U.S. Navy Dive Computer

2B-9

PAGE LEFT BLANK INTENTIONALLY

2B-10

U.S. Navy Diving Manual — Volume 2

APPENDIX 2C

Environmental and Operational Hazards
2C-1

ENVIRONMENTAL HAZARDS
1. Weather. Surface conditions affect both the divers and topside team members.

Completing the Environmental Assessment Worksheet (Figure 2C-2) helps
ensure that environmental factors are not overlooked during planning. Table
2C-1 provides windchill equivalents varying temperatures and wind speeds.
For an extensive dive mission, a meteorological detachment may be requested
from the local or regional meteorological support activity.

Conditions for the area of operations can be determined from special charts
that show seasonal variations in temperature and wind. Weather reports and
long range weather forecasts should be studied to determine likely conditions.
Extreme conditions are generally a greater problem for topside personnel
than for the diver. Any reduction in the effectiveness of the topside personnel
may endanger the safety of the diver. Personnel shall guard against: sunburn,
windburn, hypothermia, frostbite, and heat exhaustion. Eyewear should be worn
to protect against damaging effects of ultraviolet light from the sun. Weather
reports shall be continually monitored while an operation is in progress.
2. Sea State. Divers are not particularly affected by the action of surface waves

unless operating in surf or shallow waters, or if the waves are exceptionally
large. Surface waves may become a serious problem when the diver enters
or leaves the water and during decompression stops. Wave action can affect
everything from the stability of the moor or the Dynamic Positioning of the
ship to the vulnerability of the crew to seasickness or injury. Unless properly
moored, a ship or boat may drift, swing, or drag in the moor and endanger
divers. Table 2C-2 provides Sea state conditions.

NOTE

Shifts in winds or tides may cause wild swings of the mooring and
endanger divers working on the bottom. Diving supervisors must maintain
situational awareness of weather and sea state and monitor changes
that may adversely affect the operation. Diving shall be discontinued if
sudden squalls, electrical storms, heavy seas, unusual tide or any other
condition exists that, in the opinion of the Diving Supervisor, jeopardizes
the safety of the divers or topside personnel.
3. Surface Visibility. Diver and support crew safety is the prime consideration

when determining if surface visibility is adequate. Reduced visibility may
seriously hinder, or force postponement of, diving operations and the diving
schedule should allow for delays when operating in a known fog belt. For
example, a surfacing diver might not be able to find the support craft, or a
diver on the surface or the craft itself might be in danger of being hit by surface
traffic. A proper radar reflector for small craft should be considered in low
visibility conditions.

APPENDIX 2C — Environmental and Operational Hazards

2C-1

Table 2C‑1. Equivalent Wind Chill Temperature Chart.

4. Underwater Visibility. Underwater visibility varies with depth and turbidity.

Horizontal visibility is usually quite good in tropical waters; a diver may be
able to see more than 100 feet at a depth of 180fsw. Horizontal visibility is
almost always less than vertical visibility. Visibility is poorest in harbor areas
because of river silt, sewage, and industrial wastes flowing into the harbor.
Agitation of the bottom caused by strong currents and the passage of large
ships can also affect visibility. The degree of underwater visibility influences
selection of dive technique and can greatly increase the time required for a
diver to complete a given task. For example, a diving team preparing for harbor
operations should plan for extremely limited visibility, possibly resulting in an
increase in bottom time, a longer period on station for the diving unit, and a
need for additional divers on the team.

5. Depth. Risk increases with depth and planning can help mitigate the increased

risk. Surface supplied diving methods and/or remotely operated vehicles (ROV)
should be used whenever possible where depth poses a significant hazard.

Decompression profiles at deeper depths have shorter bottom times that
influence the time available for divers to work and may contribute to divers
rushing through tasks on the bottom. The onset of nitrogen narcosis varies from
one diver to the next and must be considered as dive profiles exceed 100fsw.
Work up dives (in the water, or a chamber) to increasingly deeper depths are an
2C-2

U.S. Navy Diving Manual — Volume 2

effective way to expose divers to the effects of nitrogen narcosis and mitigate
risk.
Increased depth represents a higher risk for divers in self-contained apparatus
due to their limited gas supply and isolation from surface assistance. The
deeper the dive, the more important it is to compute air supply durations with
sufficient allowances for the effects of water temperature and work rate.
Depth must be carefully measured and plotted over the general area of the
operation to get an accurate depth profile of the dive site. Depth readings taken
from a chart should only be used as an indication of probable depth.
6. Bottom type. The type of bottom may have a significant effect upon a diver’s

ability to move and work efficiently and safely. Advance knowledge of bottom
conditions is important in scheduling work, selecting dive technique and
equipment, and anticipating possible hazards. The type of bottom is often
noted on charts for the area, but conditions can change within just a few feet.
Verification of the type of bottom should be obtained by sample or observation.
Various underwater obstacles, such as wrecks or discarded munitions, may
pose serious hazards to diving. Wrecks and dumping grounds are often noted
on charts, but the actual presence of obstacles might not be discovered until an
operation begins. This is a good reason for scheduling a preliminary inspection
dive. Table 2C-3 outlines the basic types of bottoms and the characteristics of
each.

7. Tides and Currents. Tides and currents can significantly impact diving

operations. Information and tables on tides and currents are available from
a U.S. Navy Meteorlogical Detachment (METOC) or National Oceanic and
Atmospheric Administration (NOAA) website. The types of currents that affect
diving operations are:
(a) River or Major Ocean Currents. The direction and velocity of normal river,

ocean, and tidal currents will vary with time of the year, phase of the tide,
configuration of the bottom, water depth, and weather. Tide and current
tables show the conditions at the surface only and should be used with
caution when planning diving operations. The direction and velocity of the
current beneath the surface may be quite different than that observed on the
surface.

(b) Ebb Tides. Current produced by the ebb and flow of the tides may add to or

subtract from any existing current. The greater the difference in high and
low tides, the greater the generated current. These effects are not limited
to restricted bodies of water, but can also be experienced in large and
(relatively) shallow seas.

APPENDIX 2C — Environmental and Operational Hazards

2C-3

Sea
State

Description

Wind Force
(Beaufort)

Wind
Descrip­tion

Wind
Range
(knots)

Wind
Velocity
(knots)

Average
Wave
Height
(ft)

0

Sea like a mirror.

0

Calm

<1

0

0

Ripples with the appearance of scales are formed,
but without foam crests.

1

Light Air

5-3

2

0.05

1

Small wavelets still short but more pronounced;
crests have a glassy appearance but do not
break.

2

Light Breeze

4-6

5

0.18

2

Large wavelets, crests begin to break. Foam
of glassy appearance, perhaps scattered
whitecaps.

3

Gentle
Breeze

7-10

8.5
10

0.6
0.88

3

Small waves, becoming longer; fairly frequent
whitecaps.

4

Moderate
Breeze

15-16

12
13.5
14
16

1.4
1.8
2.0
2.9

4

Moderate waves, taking a more pronounced long
form; many whitecaps are formed. Chance of
some spray.

5

Fresh
Breeze

17-21

18
19
20

3.8
4.3
5.0

5

Large waves begin to form; white foam crests are
more extensive everywhere. Some spray.

6

Strong
Breeze

22-27

22
24
24.5
26

6.4
7.9
8.2
9.6

6

Sea heaps up and white foam from breaking waves
begins to be blown in streaks along the direction
of the wind. Spindrift begins.

7

Moderate
Gale

28-33

28
30
30.5
32

11
14
14
16

7

Moderately high waves of greater length; edges
of crests break into spindrift. The foam is blown
in well marked streaks along the direction of the
wind. Spray affects visibility.

8

Fresh Gale

34-40

34
36
37
38
40

19
21
23
25
28

8

High waves. Dense streaks of foam along the
direction of the wind. Sea begins to roll. Visibility
affected.

9

Strong Gale

45-47

42
44
46

31
36
40

9

Very high waves with long overhanging crests.
Foam is in great patches and is blown in dense
white streaks along the direction of the wind. The
surface of the sea takes on a white appearance.
The rolling of the sea becomes heavy and shocklike. Visibility is affected.

10

Whole Gale

48-55

48
50
51.5
52
54

44
49
52
54
59

Exceptionally high waves. The sea is completely
covered with long white patches of foam along
the direction of the wind. Everywhere the edges
of the wave crests are blown into froth. Visibility
seriously affected.

11

Storm

56-63

56
59.5

64
73

Air filled with foam and spray. Sea completely white
with driving spray. Visibility seriously affected.

12

Hurricane

64-71

>64

>80

Table 2C-2. Sea State Chart.

2C-4

U.S. Navy Diving Manual — Volume 2

(c) Undertow or Rip Current. Undertow or rip currents are caused by the rush

of water returning to the sea from waves breaking along a shoreline. Rip
currents will vary with the weather, the state of the tide, and the slope of
the bottom. These currents may run as fast as two knots and may extend
as far as one-half mile from shore. Rip currents, not usually identified
in published tables, can vary significantly from day to day in force and
location.

(d) Surface Current. Wind­
-generated surface currents are temporary and

depend on the force, duration, and fetch of the wind. If the wind has
been blowing steadily for some time, this current should be taken into
consideration especially when using free swimming dive methods.

A diver in surface supplied gear with heavy weights can usually work in currents
up to 1.5 knots without undue difficulty. A diver supplied with an additional
weighted belt may be able to accomplish useful work in currents as strong as
2.5 knots. Free swimming divers are severely handicapped by currents greater
than 1.0 knot and may deplete limited gas supplies more rapidly due to exertion
against currents. It may be necessary to schedule work during periods of slack
water to minimize the tidal effect.
8. Water Temperature. Figure 2C-1 illustrates how water temperature can affect

a diver’s performance, and is intended as a planning guide. A diver’s physical
condition, amount of body fat, and thermal protection equipment determine
how long exposure to extreme temperatures can be safely endured. Mitigations
for temperature may bring about additional hazards and divers must be fully
trained on the implications of diving in hot and cold water. Mission planning
should include recognition and management of thermal stress injuries and
should be part of pre­mission training and briefs as well as seasonal refresher
training. Personnel shall remain alert for the symptoms of heat/cold related
injuries in divers and topside support personnel.
(a) Cold water diving. Cold water diving is defined as those diving operations

that occur in water temperatures 37 degrees F and colder. Diving in cold
water is a serious endeavor and should not be taken lightly. Even in relatively
warm water, thermoclines may expose divers to temperatures they are not
prepared to cope with. Temperature readings should be taken to determine
the water temperature at the surface and on the bottom prior to performing
air calculations or determining thermal protection requirements.

The ability to concentrate and work efficiently will decrease rapidly in cold water.
Exertion against heavy suits may increase air consumption and poses an increased
hazard to divers in self-contained equipment. The loss of body heat to the water,
and higher exertion levels can quickly bring on diver exhaustion. Additionally, the
use of hot water suits can expose divers to a greater risk of DCS and heat exhaustion
if they are too hot while working on the bottom. For this reason, divers should
adjust their hot water bypass valve to remain comfortably cool while working on
the bottom and then readjust the hot water bypass to a maintain warmth while on
ascent and during decompression.

APPENDIX 2C — Environmental and Operational Hazards

2C-5

Dehydration increases the risk of DCS and is just as likely in cold weather due to
immersion diuresis. Additionally, winter climates typically have lower humidity
levels which cause the body to lose water through normal breathing. Further
information is available in paragraph 3-10.2 (Hypothermia), paragraph 3-10.3
(Other Physiological Effects of Exposure to Cold Water), paragraph 3-12.1
(Dehydration), Figure 3-6 (Oxygen Consumption and RMV), and in Chapter 11
(Ice and Cold Water Diving).
TYPE

CHARACTERISTICS

VISIBILITY

DIVER MOBILITY ON BOTTOM

Rock

Smooth or jagged,
minimum sediment

Generally unrestricted by dive
movement

Good, exercise care to prevent line
snagging and falls from ledges

Coral

Solid, sharp and jagged,
found in tropical waters
only

Generally unrestricted by diver
movement

Good, exercise care to prevent line
snagging and falls from ledges

Relatively smooth,
granular base

Generally unrestricted by diver
movement

Good, occasional sloping bottoms
of loose gravel impair walking and
cause instability

Composed principally of
broken shells mixed with
sand or mud

Shell-sand mix does not impair
visibility when moving over
bottom. Shell-mud mix does
impair visibility. With higher
mud concentrations, visibility is
increasingly impaired.

Shell-sand mix provides good
stability. High mud content can
cause sinking and impaired
movement

Common type of bottom,
packs hard

Generally unrestricted by diver
movement

Good

Common type of bottom,
composed of varying
amounts of silt and clay,
commonly encountered
in river and harbor areas

Poor to zero. Work into the
current to carry silt away from
job site, minimize bottom
disturbance. Increased hazard
presented by unseen wreckage,
pilings, and other obstacles.

Poor, can readily cause diver
entrapment. Crawling may be
required to prevent excessive
penetration, fatiguing to diver.

Gravel

Shell

Sand

Mud
and
Silt

Table 2C‑3. Bottom Conditions and Effects Chart.

(b) Warm Water Diving. Warm water diving is defined as those diving operations

that occur in water temperatures exceeding 88° F. Diving in water temperatures
above 99°F should not be attempted without first contacting NAVSEA 00C.

(c) Conditions that contribute to thermal loading such as heavy work rates,

significant pre/post dive activities, and various diver dress (dive skins/wetsuits/
dry suits) can reduce exposure limits appreciably. The following precautions
apply to all warm water diving operations above 88°F:

n Divers should hydrate fully (approximately 500 ml or 17 oz) two hours before
diving. Fluid loading in excess of the recommended 500 ml may cause lifethreatening pulmonary edema and should not be attempted. Weight losses up
to 15 lbs (or 6-8% of body weight) due to fluid loss may occur and mental
and physical performance can be affected.
n Hydrating with water or a glucose/electrolyte beverage should occur as soon
as possible after diving. Approximately 500 ml should be replaced for each
hour of diving.

2C-6

U.S. Navy Diving Manual — Volume 2

n Divers should be hydrated and calorically replete to baseline weight, rested,
and kept in a cool environment for at least 12 hours before a repeat exposure
to warm water is deemed safe. These exposure limits represent maximum
cumulative exposure over a 12 hour period.
NOTE

The following are the general guidelines for warm water diving. Specific
UBAs may have restrictions greater than the ones listed below; refer to
the appropriate UBA Operations and Maintenance manual. The maximum
warm water dive time exposure limit shall be the lesser of the approved
UBA operational limits, canister duration limits, oxygen bottle duration or
the diver physiological exposure limit.

n A diver working at a moderate rate e.g. swimming at 0.8 kts or less:
88°–94°F ­limited to canister/O2 bottle duration or diver aerobic endurance
>94°–97°F - limited to three hours based on physiological limits.
>97°–99°F - limited to one hour based on physiological limits.
n A resting diver e.g. during decompression:
88°–97°F - limited to canister duration.
>97°–99°F - limited to two hours based on physiological limits.
Mission Planning Factors. The following mission planning factors may mitigate
thermal loading and allow greatest utilization of the exposure limits:
n Conduct diving operations at night, dusk, or dawn to reduce heat stress
incurred from sun exposure and high air temperatures.
n Avoid wearing a hood with a dive skin to allow evaporative cooling.
n Wearing dive skin or anti­chafing dress may increase thermal loading.
Although the effect of various diver dress is not known, it is expected that
safe exposure durations at temperatures above 96°F will be less.
n Follow the guidelines in paragraph 3-10.4.4 regarding acclimatization.
Reduce the intensity of acclimatization dives for five days immediately prior
to the diving operation.
n Ensure divers maintain physical conditioning during periods of warm water
diving.
n Methods of cooling the diver should be employed whenever possible. These
include using hot water suits to supply cold water to the diver and the use of
ice vests.
Further guidance is contained in paragraph 3-10.4.4 (Hyperthermia), paragraph
3-12.1 (Dehydration), and Figure 3-6 (Oxygen Consumption and RMV).
APPENDIX 2C — Environmental and Operational Hazards

2C-7

WATER TEMPERATURE PROTECTION CHART
Unprotected
Diver

Water Temp
C

32.0

Resting diver
will overheat

90
Working diver may
overheat depending
on workload

29.5
26.5

Dry Suit
Diver

(At shallow
(<20fsw) depths)

F

35.0

Wet Suit
Diver

80

Resting diver
chills in 1-2
hours

Thermal protection usually needed
below 80 F water

24.0
21.0

70
Thermal protection
usually not the limiting
factor in a wet suit

18.5
15.5

60

13.0
10.0

01.5
Freezing point
Fresh water
-01.0
Freezing point
Salt water
-04.0

Thermal protection
usually not the limiting
factor in a dry suit

3 hours

5 hours

1 hour

3 hours

50

07.0
04.5

5 hours

40

30

* Below 40 F,
hot water suit or
dry suit is reccommended
for surface-supplied
diving

This chart can be used as a guide for planning dives in cold water. The dive durations listed for
each suit are not rules or limits. Instead they represent dive times that will challenge the average
diver wearing the thermal protection listed, but will have a minimal chance of producing
significant hypothermia. Acutal dive durations may be longer or shorter than those listed, due to
operational considerations and/or individual tolerance.

Figure 2C‑1. Water Temperature Protection Chart.

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U.S. Navy Diving Manual — Volume 2

9. Contaminated Water. Medical personnel should be consulted when planning

for diving in contaminated water to ensure proper precautions are taken and
post-dive monitoring of divers is conducted. When planning for operations in
contaminated waters, personnel protective equipment (PPE) and appropriate
preventative medical procedures shall be taken. Diving equipment shall be
selected that gives the diver maximum protection consistent with the risk.
Resources and technical advice for dealing with contaminated water diving
conditions are available in the Guidance for Diving in Contaminated Waters,
SS521-AJ-PRO-010, and from NAVSEA 00C3.

10. Altitude. Dives may be required in bodies of water higher than sea level

and planning must address the effects of the lower atmospheric pressures
encountered. Air Decompression Tables and Surface-Supplied Helium-Oxygen
Tables are authorized for use at altitudes up to 300 feet above sea level without
corrections and electronically controlled UBA tables may be used at altitudes
up to 1000 feet above sea level without modification.

Transporting divers post-dive, may include movement into higher elevations,
either overland or by plane, and requires special consideration and planning.
The Diving Supervisor shall be especially alert for symptoms of hypoxia and
decompression sickness after the dive due to the lower oxygen partial pressure
and atmospheric pressure. Additional guidance for diving at altitude may be
found in paragraph 9-13 for air diving, paragraph 12-7 for surface supplier
HEO2 diving, and section 15-10 for MK-16 diving. Contact NAVSEA 00C for
further guidance.
11. Marine Life. Certain marine life, because of its aggressive or venomous

nature, may be hazardous to man. Some species of marine life are extremely
dangerous, while some are merely an uncomfortable annoyance. Most hazards
from marine life are largely overrated because most underwater animals leave
man alone. All divers should be able to identify the hazardous species that are
likely found in the area of operation and should know how to deal with each.
Refer to Appendix 5C for specific information about hazardous marine life,
including identification factors, hazardous characteristics, injury prevention,
and treatment methods.

APPENDIX 2C — Environmental and Operational Hazards

2C-9

ENVIRONMENTAL CHECKLIST
Date:
Surface
Sea Surface
Sea State
Wave Action:
Height
Length
Direction
Current:
Direction
Velocity
Type
Surf. Visibility
Surf. Water Temp.
Local Characteristics

Atmosphere
Visibility
Sunrise (set)
Moonrise (set)
Temperature (air)
Humidity
Barometer
Precipitation
Cloud Description
Percent Cover
Wind Direction
Wind Force (knots)
Other:

Subsurface
Underwater & Bottom
Depth
Water Temperature:
depth
depth
depth
bottom
Thermoclines

Visibility
Underwater
ft
ft
ft
Bottom
ft
Bottom Type:

Curent:
Direction
Source
Velocity
Pattern
Tides:
High Water
Low Water
Ebb Dir.
Flood Dir.

Obstructions:

at
at
at

depth
depth
depth

at

depth

Marine Life:
Time
Time
Vel.
Vel.

Other Data:

NOTE: A meteorological detachment may be requested from the local meteorological support activity.

Figure 2C‑2. Environmental Assessment Worksheet. The

Environmental Assessment Worksheet
indicates categories of data that might be gathered for an operation. The data collected is vital for
effective operations planning, and is also of value when filing Post Salvage Reports.

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U.S. Navy Diving Manual — Volume 2

2C-2

OPERATIONAL HAZARDS
1. Fouling and Entrapment. Divers are often required to work in enclosed or

confined spaces or in and around areas that subject them to being fouled.
Fouling can be a serious hazard, or a momentary inconvenience, depending
on the diver’s and dive team’s reaction to the condition. Some dive tasks
expose divers to fouling more than others and adverse bottom type/conditions
contribute to the hazard. Inexperienced divers may be more prone to fouling
than experienced divers.
The surface-supplied diver may become fouled more easily, but will usually
have an ample air supply while working to get free. A non-surface supplied
diver may have no other recourse but to remove the gear and make a free
ascent. If trapped, the non-surface supplied diver must face the possibility of
running out of air before being able to work free.
Divers must maintain awareness of the tend of their umbilical or tending line
as they progress in and around obstructions such as pier pilings. Tenders must
pay attention to the direction of the umbilical tend to prevent the diver’s air
supply from being cut off due to the umbilical being caught between a ship or
submarine and a separator.
Divers may become trapped on active ship or submarine sea suctions.
Diving within 50 feet of an active sea suction (located on the same side of the
keel) that is maintaining a suction of 50 gpm or more, is not authorized unless
considered as an emergency repair and is authorized by the Commanding
Officers of both the repair activity and tended vessel.
The Diving Supervisor shall determine if a sea suction is a safety hazard to the
divers prior to conducting any diving operation when:

n A sea suction is maintaining a suction of less than 50 gpm and is less than 50
feet from the dive site.
n A sea suction is more than 50 gpm and is less than 50 feet but on the opposite
side of the keel.
Diving on SSN 688, SSN 774, SSN 21 (SEAWOLF), SSBN, and SSGN class
submarines does not present a hazard to divers when ASW and MSW pumps are
operating in slow or super slow modes.
In all cases the Diving Supervisor shall be aware of the tend of the diver’s umbilical
to ensure that it will not cross over or become entrapped by an active sea suction.
Diver tag‑out procedures must be completed in accordance with the TUMS and
SORM to ensure ASW and MSW pumps are not operated in fast mode. Divers
must be properly briefed on location of suctions and current status of equipment.
(a) The first and most important action that a trapped diver can take is to stop and

think. The diver shall remain calm, analyze the situation, and carefully try to

APPENDIX 2C — Environmental and Operational Hazards

2C-11

work free. Panic and overexertion are the greatest dangers to the trapped diver.
If the situation cannot be readily resolved, help should be obtained. Emergency
procedures for specific diving modes may be found in their applicable chapters.
(b) When diving on the opposite side of the keel from the dive platform, divers

may become trapped on the opposite side of the ship when a tide goes out. A
minimum positive clearance of the keel to the bottom at mean low water of
six feet must be established when diving below bilge keel on surface ships or
below the maximum beam on submarines. Additionally, a minimum positive
clearance of four feet between the pier and the vessel should be established and
maintained in order to provide an egress path for divers.

2. Enclosed Space Diving. Divers may enter submarine ballast tanks, mud tanks,

or cofferdams, which may be in either a flooded or dry condition. Access to
these spaces is normally restrictive, making it difficult for the diver to enter and
exit. The interior of sunken ships, barges, submarine ballast tanks, mud tanks,
sonar domes, and cofferdams is hazardous due to limited access, poor visibility,
slippery surfaces and potentially contaminated atmosphere. Planned routine
diving in these spaces shall be supported by a surface-supplied air source.

(a) With the exception of submarine ballast tanks, when a diver is working in an

enclosed or confined space, the Diving Supervisor shall have the diver tended
by another diver at the access opening. Ultimately, the number of tending divers
deployed depends on the situation and the good judgment of the dive planners
and the Dive Supervisor.

WARNING

All enclosed space divers shall be outfitted with a KM-37 NS or MK 20 MOD
0/1 that includes a diver-to- diver and diver-to-topside communications
system and an EGS for the diver inside the space.

WARNING		

Divers in submarine ballast tanks shall not remove their diving equipment
until the atmosphere has been flushed twice with air from a compressed
air source meeting the requirements of Chapter 4, or the submarine
L.P. blower, and tests confirm that the atmosphere is safe for breathing.
Testing shall be done in accordance with NSTM 074, Volume 3, Gas Free
Engineering (S9086-CH-STM-030/CH-074) for forces afloat, and NAVSEA
S-6470-AA-SAF-010 for shore-based facilities and repeated hourly.

WARNING		

If divers smell any unusual odors, or if the diving equipment should fail,
the diver shall immediately switch to the EGS and abort the dive.
(b) Enclosed Space SCUBA. Under normal circumstances enclosed space diving

in SCUBA is not recommended due to the likelihood of loss of orientation,
fouling/entrapment, and limited air supply. However, emergent situations
may arise where SCUBA is the only option, or is the most viable option, for
an enclosed space dive. Enclosed space diving in SCUBA is a very high risk
evolution and is strictly limited to saving human life, or saving/recovering
items of such importance to warrant the risk of potential loss of life. The use
of SCUBA for enclosed space diving may only be considered in a time critical
situation where a Surface Supplied Diving System or Surface Supplied Diving
Apparatus (DP 2) is unavailable or cannot be obtained in time.

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U.S. Navy Diving Manual — Volume 2

Not all enclosed space SCUBA diving situations or conditions can be covered in
this paragraph. Ultimately, the extent of penetration into the space depends on
the situation and the judgment of the Dive Supervisor. The following guidance is
provided:
n A minimum of two divers tended from the surface are required with one
diver tending the other diver from the access opening.
n The stability and integrity of the enclosed space shall be assessed prior to
entry.
n Each diver will have a strong, working dive light.
n Full face mask, voice communications, chafing gear, and head protection
(PROTEC) are recommended to mitigate hazardous conditions.
The Dive Supervisor must assume higher than normal workrates and worst case
conditions when calculating duration of air supply for an enclosed space SCUBA
dive (i.e. poor visibility and potential for disorientation, extent of penetration,
likelihood of fouling /entrapment and, difficulty of required tasks), Careful
consideration shall be given to planned bottom times.
3. Electrical Shock Hazards. Electrical shock may occur when using any electric

or electronic equipment or as a result of an objective hazard in the environment
(damaged underwater cables, auxiliary power systems within wreckage, etc).
All electrical equipment shall be in good repair and be inspected before diving
and safety precautions must be understood and followed. Dive planners must
be attentive to any potential objective electrical hazards to personnel and ensure
risk management controls are applied where they exist.

(a) Although equipped with test buttons, electrical Grounds Fault Interrupters

(GFI) often do not provide any indication when the unit has experienced an
internal component failure in the fault circuitry. Therefore, GFI component
failure during operation (subsequent to testing the unit) may go unnoticed.
Although this failure alone will not put the diver at risk, the GFI will not protect
the diver if he is placed in contact with a sufficiently high fault current. GFIs
are required when line voltage is above 7.5 VAC or 30 VDC. And GFIs shall
be capable of tripping within 20 milliseconds (ms) after detecting a maximum
leakage current of 30 milliamps (ma).

CAUTION		

GFIs require an established reference ground in order to function properly.
Cascading GFIs could result in loss of reference ground; therefore, GFIs
or equipment containing built-in GFIs should not be plugged into an
existing GFI circuit.

In general, three independent actions must occur simultaneously to electrically
shock a diver:
n The GFI must fail.

APPENDIX 2C — Environmental and Operational Hazards

2C-13

n The electrical equipment which the diver is operating must experience a
ground fault.
n The diver must place himself in the path between the fault and earth ground.
(b) Reducing Electrical Shock Hazards. The only effective means of reducing

electrical shock hazards are to ensure:

n Electrical equipment is properly maintained.
n All electrical devices and umbilicals are inspected carefully before all
operations.
n Electrical cables are adequately protected to reduce the risk of being abraded
or cut when pulled over rough or sharp objects.
n Personnel are offered additional protection through the use of rubber suits
(wet, dry, or hot-water) and rubber gloves.
n GFI circuits are tested at regular intervals throughout the operation using
built- in test circuits.
Divers operating with remotely operated vehicles (ROVs) should take similar
precautions to ensure the ROV electrical system offers the required protection.
Many new ROVs use extremely high voltages which make these protective actions
even more critical to diver safety.
(c) Securing Electrical Equipment. The Ship Repair Safety Checklist for Diving

requires underwater electrical equipment to be secured while divers are working
over the side. While divers are in the water:

n Ship impressed current cathodic protection (ICCP) systems must be secured,
tagged out, and confirmed secured before divers may work on an ICCP
device such as an anode, dielectric shield, or reference cell.
n When divers are required to work close to an active ICCP anode and there is
risk of contact with the anode, the system must also be secured.
n In situations other than those described above, the ICCP should remain
active.
n Divers working within 15 feet of active systems must wear a full dry suit,
unisuit, or wet suit with hood and gloves.
n All other underwater electrical equipment shall be secured while divers are
working over the side.
4. Explosions. Explosions may be set off intentionally or accidentally. Accidental

explosions may be a result of welding or cutting in gas filled spaces,
inappropriate application of cutting equipment, or accidental contact or
handling of unexploded munitions or explosives or ejection seats on downed
aircraft. Only EOD divers shall clear old or damaged munitions.

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U.S. Navy Diving Manual — Volume 2

Divers remove man-made structures such as barriers, sunken naval craft, and
damaged piers by blasting, freeing, flattening, or cutting with explosives.
Divers may also be tasked to destroy natural formations, such as reefs, bars, and
rock structures that interfere with transportation routes. Divers should exit the
water when an explosion is imminent. Paragraph 2-7.3 provides information
regarding underwater explosions. See paragraph 3-12.6 for more information
on blast injury.
The Demolitions Operation Supervisor (DOS) is responsible for providing
the Diving Supervisor with a comprehensive, written demolitions plan. All
demolition operations shall be conducted using approved procedures and
qualified demolition personnel shall ensure the operation does not proceed
until receiving specific approval from the Diving Supervisor. The DOS shall
take charge of all misfires and handle them in accordance with the approved
demolitions plan.
The Dive Supervisor shall be wary of post-blast secondary effects when
conducting post-blast investigation dives. Significant changes to the
environment may occur as a result of the underwater explosions.
5. Sonar. Appendix 1A provides guidance regarding safe diving distances and

exposure times for divers operating in the vicinity of ships transmitting with
sonar.

6. Nuclear Radiation. Radiation may be encountered as the result of an accident,

proximity to weapons or propulsion systems, weapons testing, or naturally
occurring conditions. Radiation exposure can cause serious injury and illness.
Safe exposure levels may be found in the Radiological Control Manual for
Ships, NAVSEA S9123-33-MMA-000-V, or Shipyard Radiological Control
Manual, 389-0288 and these levels shall not be exceeded. All divers shall be
knowledgeable of local command radiological control requirements prior to
diving. Divers shall wear a Thermal Luminescence Dosimeter (TLD) or similar
device when required and be apprised of the locations of items such as the
reactor compartment, discharges, etc.

APPENDIX 2C — Environmental and Operational Hazards

2C-15

IN: “I require a diver.”

IO: “I have no diver.”

IN1: “I require a diver to clear my propeller.”

IP: “A diver will be sent as soon as possible or at time indicated.”

IN2: “I require a diver to examine bottom.”

IQ: “Diver has been attacked by diver’s
disease and requires decompression
chamber treatment.”

IN3: “I require a diver to place collision mat.”

IR: “I am engaged in submarine survey
work (underwater operations). Keep
clear of me and go slow.”

IN4: “I require a diver to clear my anchor.”

A: “I have a diver down; keep well clear at
slow speed.”

Code Flag (Note 1)

Sport Diver (Unofficial)

General Note: Rule 27 of Navigation Rules-International-Inland of March 1999 states the lights
and shapes that must be displayed when engaged in diving operations.
Note 1: International Signal Code – All signals must be preceded by the code flag to signify that they
are international signals. (Do not use code flag in inland waters.)

Figure 2C‑3. International Code Signal Flags.

Figure 6-12. International Code Signal Flags.

2C-16
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U.S. Navy Diving Manual — Volume 2
U.S. Navy Diving Manual—Volume 2

7. Surface Traffic. The presence of other ships is often a serious problem. Any

time diving operations are conducted in the vicinity of other ships a local
Notice to Mariners should be issued and proper signal flags and shapes shall
be hoisted (Figure 2C-3). Rigid flags, or flags with an extension device to fully
display the symbol shall be used. It may be necessary to close off an area or
limit the movement of other ships, by posting a picket boat, or by keeping the
dive boat between the divers and any surface traffic.
An operation may have to be conducted in an area with many small boats
operated by people with varied levels of seamanship and knowledge of Nautical
Rules of the Road. The dive team should assume that these operators are not
acquainted with diving signals and take the precautions required to ensure that
these vessels remain clear of the diving area. Hazards associated with vessel
traffic are intensified under conditions of reduced visibility and use of radar
reflectors should be considered.

8. Equipment Failure. With well-maintained and thoroughly inspected and tested

equipment, operational failure is rarely a problem. When a failure does occur,
the correct procedures will depend upon the type of equipment and specifics of
the situation. The training, experience, and discipline of the diver and the dive
team will be the most important factor in resolving the situation safely. Each
type of dive equipment has its own unique hazards and emergency procedures.
Proficiency with the equipment and thorough knowledge of the procedures
found in the operation and maintenance manual is imperative to preventing,
and dealing with, equipment failure. Maintaining sufficient operational spares
and adherence to maintenance procedures and schedules prevents equipment
failure from compromising safety and the mission.

9. Loss of Depth Control. Loss of depth control includes uncontrolled ascent and

decent and may result in POIS, squeeze, or physical injury from impact with
hard objects (underside of a boat or rocks/debris on the bottom).

(a) Uncontrolled ascent (Blow up). Blow up is most common when diving with

variable volume dry suits (VVDS) and in SCUBA. Divers should be wary of
a dive plan that involves increasing diver buoyancy to carry heavy objects to
the surface. Sending down a lift line or utilizing a lift balloon is a much safer
method to bring objects to the surface. Divers must ensure they do not become
fouled in or on buoyant lifting devices. Thorough work up dives that mimic
working conditions while in VVDS results in divers experienced and confident
with work tasks to be performed. Divers experiencing a blow up should be
aware that a failure of vent valves may result in rupture of the suit or buoyancy
vest and result in a fall.

(b) Uncontrolled decent (falling). Falling can affect a free swimming or surface

supplied diver. The greatest change of pressure in the water column occurs
within the first 30fsw and rapid changes in buoyancy can occur in this range in
the water column. When working in the water column, the surface supplied diver
should keep a hand on the stage or rigging to keep from falling. Divers working
in dry suits should avoid putting a hand over head as air leakage around the
edges of the cuffs may change the suit buoyancy and increase the possibility of
a fall in the water column. Diver experiencing a uncontrolled descent while in
SCUBA or diving with a VVDS may result in over compensation of buoyancy
by the diver and lead to blow up.

APPENDIX 2C — Environmental and Operational Hazards

2C-17

PAGE LEFT BLANK INTENTIONALLY

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U.S. Navy Diving Manual — Volume 2

APPENDIX 2D

Guidance for U.S. Navy Diving on a
Dynamic Positioning Vessel
2D-1

INTRODUCTION

Dynamic Positioning is a shipboard computer controlled system integrating
position, heading and other sensors with onboard thrusters to hold a vessel in a
fixed position and heading for a prolonged period of time so that work may be
safely accomplished.
NOTE:

2D-2

All Navy commands shall contact NAVSEA 00C3 prior to conducting
diving operations from a DP vessel to obtain specific guidance and
authorization. DP diving will be authorized for Surface Supplied Air,
Mixed Gas and Saturation diving only. SCUBA and DP-2 diving are not
authorized from a DP vessel.

DYNAMIC POSITIONING (DP) CAPABILITY

Some vessels possess dynamic positioning (DP) capability, see Figure 2D-1.
DP uses the ship’s propulsion systems (thrusters, main propulsion, and rudders)
to maintain a fixed position. Surface-supplied diving and saturation diving,
dynamic positioning (DP) ships shall meet International Maritime Organization
(IMO) Class 2 or 3 standards. IMO Equipment Class 2 will maintain automatic

Figure 2D‑1. DP Diving Vessel.

APPENDIX 2D — Guidance For U.S. Navy Diving on a Dynamic Positioning Vessel

2D-1

or manual position and heading control under specified maximum environmental
conditions, during and following any single-point failure of the DP system. IMO
Equipment Class 2 excludes the loss of a compartment. IMO Equipment Class 3
will maintain automatic or manual position and heading control under specified
maximum environmental conditions, during and following any single-point failure
including the loss of a compartment. Both Class 2 and 3 require two independent
computer systems, but Class 3 requires them to be separated by a bulkhead capable
of preventing the passage of smoke and flame.
2D-2.1

DP Advantages. DP advantages include:

n Vessel is fully self-propelled; no tugs are required at any stage of the
operation.
n Setting-up on location is quick and easy.
n Vessel is very maneuverable.
n Rapid response to weather changes.
n Rapid response to changes in the requirements of the operation.
n Versatility within system (i.e. track-follow, ROV-follow and other specialist
functions).
n Ability to work in any water depth.
n Ability to complete short tasks quicker, thus more economically.
n Avoidance of risk of damaging seabed hardware by mooring lines and
anchors.
n Avoidance of cross-mooring with other vessels or fixed platforms.
n Ability to move to new location rapidly.
2D-2.2

DP Disadvantages. DP disadvantages include:

n Failure to keep position (drift off) due to equipment failure, if adequate
system redundancy does not exist.
n Failure to keep position if erroneous inputs are received by the sensors such
as helicopter wash on wind sensors. The DP vessel will drive off trying to
overcome what the computer thinks is a strong wind.
n Higher long term day rates than comparable moored systems.
n Higher fuel consumption.

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U.S. Navy Diving Manual — Volume 2

n Thrusters, main propellers and independent rudder movement could be a
hazard to divers.
n Loss of position in extreme weather or in shallow waters and strong currents.
n Position control is active and relies on human operator input (as well as
equipment).
n More personnel required to operate and maintain equipment.
2D-2.3

DP Classification. DP vessels come with one of several classifications depending

on capability, redundancy, and classification society class notations. Using the
American Board of Shipping (ABS) notation DP0 is the least capable, DP3 is the
most capable. Diving operations may only be conducted from vessels classified
DP2 or DP3.

2D-2.3.1

Classification Societies. There are numerous marine classification societies
around the world that classify DP vessels. All use the standards established by
the International Maritime Organization (IMO), which falls under the United
Nations. IMO Circular 645 “Guidelines for Vessels with DP Systems, is the
governing document and has been in existence for over 20 years. However, each
classification society has their own specific set of rules for classifying ships under
their organization. Major classification societies include:

n ABS (American Bureau of Shipping), Houston, Texas
n DNV GL (Det Norske Veritas - Germanisher Llyod), Oslo, Norway
n Class NK, Tokyo, Japan
n Lloyds Register, UK
A vessel is classified by its classification society to meet a DP classification when
first put into service, every five years thereafter, and upon major changes.
2D-2.4

DP System Components. The DP system components can be broken down into

the following:

n Position Reference Systems: Differential GPS, laser, hydro acoustic, taut
wire, and microwave.
n Environmental Reference Systems: wind sensors, vertical reference, and
motion reference.
n DP Operator Control Elements: bridge consoles and computers.
n Heading Reference: gyro compasses (at least 2 or 3 for DP2 or DP3).

APPENDIX 2D — Guidance For U.S. Navy Diving on a Dynamic Positioning Vessel

2D-3

n Thrusters and Propulsion Systems: main propulsion, rudders (operate
independently from one another), tunnel thrusters/azimuth thrusters, and
thruster control.
n Power Generation: diesel engines or generators, alternators, switchboards,
power management, power distribution, Uninterruptible Power Supplies
(UPS).
2D-2.4.1

Sensors. DP2/3 vessels must possess the following sensors/systems each with
redundant power supplies:
1. At least two/three independent Position Reference Systems. These systems are

normally accurate within three meters, often better. Sample position reference
systems are:

n Differential Global Positioning System (DGPS) and GLONASS (Global
Navigation Satellite System), a Russian satellite navigation system. It
provides an alternative to GPS and is the second alternative navigational
system in operation with global coverage and of comparable precision.
n Taut wire
n Hydro acoustic
n Fanbeam laser based system
n Artemis microwave based system
n Cyscan laser based system
2. At least two gyrocompasses for heading reference.
3. At least two wind sensors, mechanical or ultrasonic.
4. Heave, pitch and roll sensors for the applicable position reference systems.
5. At least two Uninterruptible Power Supplies, (Split Bus).
2D-2.4.2

Thrusters. Multiple thrusters are required to hold the DP vessel in the desired

position on the desired heading in any anticipated wind, sea and current conditions
(Figure 2D-2). There must be enough redundancy in thrusters and their power
sources so that the vessel can maintain position even with the loss of the most
critical thruster. Many DP vessels use diesel electric propulsion to achieve
the needed level of redundancy and capability. A DP vessel must have a power
management system capable of automatically starting additional thrusters or
generators when loads reach 80% of capacity. Types of thrusters include:
1. Main Propellers.
2. Rudders ( independently controlled).
3. Tunnel thrusters (typically two in the bow and one in the stern).

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U.S. Navy Diving Manual — Volume 2

4. Azimuthing thrusters (if used it will be in the bow along with tunnel thrusters).

The azimuth thruster is typically capable of be retracted into the hull.

Figure 2D‑2. DP Component Terminology.
2D-2.4.3

Control Stations. The DP2/3 vessel must have at least two independent control

stations. The control stations allow simple input of desired heading, position,
changes to either and the rate of that change.

NOTE:

While dive operations are in progress, the vessel shall not be moved
without consultation with the Dive Supervisor. All movements will be
at slow speed. Heading changes will not exceed five degrees at a time.
Movements will not exceed 32 feet (10 meters). The center of rotation for
any move will be the dive side/moon-pool unless otherwise agreed. The
divers will be notified and brought back to
the stage before any planned move begins.

Control stations (Figure 2D-3) are often located
on the bridge or nearby location where the DP
operators have the following:
1. A view of the working deck, dive side, cranes

and other structures and vessels in the vicinity.
Remote camera displays are often used.

2. Indicators for all sensors, alarms, generators,

thrusters and power supplies.

3. A visual and audible alarm panel actuator with

various sites including the dive side.

Figure 2D‑3. DP Pilot Seat.

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2D-5

4. Redundant powered communication with all critical parties including the Dive

Supervisor.

5. Manual thruster controls and joystick control.
6. Emergency stop controls for all thrusters.
2D-2.4.4

Computers and Software. There must be sufficient redundancy such that the loss

of one system does not result in a loss of heading or position. The DP control
system is the set of computers that combines automatic computation with
instructions from operators, enabled through its interfaces. The DP control system
allows simple inputs from the operator such as a wanted position or heading, and
rates of change.

2D-2.4.5

Failure Modes and Effects Analysis. A critical document for the classification of a

DP system is the Failure Modes and Effects Analysis, stamped by the classification
society. A FMEA is prepared on the DP system during design. A separate FMEA
is prepared for the DP vessel that includes all systems that could affect DP
operations. This can include ventilation systems, emergency engine shut downs,
electrical switchboard layout, and engine cooling systems. Once a DP vessel is
ready to go into service, an FMEA Proving Trial is conducted to ensure the vessel
can reliably maintain position and heading even with critical items of different
systems experiencing casualties. The goal is a system with no single point failures.

2D-2.4.6

DP Trials. There are numerous trials conducted to ensure the DP system can meet

all operational requirements. The FMEA Proving Trial mentioned in the section
above is conducted to ensure the actual operation meets the design capabilities,
even during various failure situations. DP capability plots are developed to find the
maximum conditions of wind, waves and current, from various relative directions,
that the vessel may withstand and still maintain heading and position. Some form
of DP trials are conducted frequently, and especially before diving operations, to
ensure the DP system is fully capable of safely supporting the mission. DP trials
include:
n DP Capability Plot (calculated)
n DP Footprint Plot (actual based on trials)
n Annual DP Trials
n DP 500 Meter Checks just prior
to any DP operations
n DP 500 Meter Checks after any
DP casualty
2D-2.4.7

DP Status Lights and Alarms. There

must be DP status lights and audible
alarms at all critical stations (Figure
2D-4), including the dive side. There

2D-6

Figure 2D‑4. Alarm Panel.

U.S. Navy Diving Manual — Volume 2

must be a means to silence the alarm at the dive side. The meaning of lights and
alarms are as follows:
n Steady green light: Normal Operations.
n Flashing yellow or steady yellow light: Reduced status of DP system. Bring
divers back to the bell or stage and conduct a risk assessment. Determine
whether to recover the divers or resume operations.
n Flashing or solid red light with audible alarm: Emergency status. Probable
loss of position and or heading. Immediately recover the divers to the safest
location.
2D-2.4.8

DP Vessel Communications. There must be powered voice communications

between the DP Control Station, the Dive Site, the bridge, the Master’s Cabin, the
Engineering Control Station, the Remote Operated Vehicle Station (if applicable),
and the crane operator (if applicable). Redundant voice communications shall be
available between DP control and critical stations such as the Dive Supervisor.
To protect the safety of divers, the alarm and communication systems above are
critical. An additional consideration during operations planning is to ensure that the
divers or vessel are not endangered in the event the vessel loses all power and drifts
off station. This is normally accomplished by placing the DP vessel down-wind/
down-current of any structures or other vessels. In the event the vessel loses power,
it will drift away from danger.
2D-2.4.9

Operations Plot and Emergency Plans. A plot displaying the relative positions
of the vessel, the bell/dive stage, divers, the worksite and any known obstruction
(e.g., sunken objects, other vessels, mooring wires, etc.) together with ship’s
heading and wind direction and speed should be maintained at all times at the
DP control position. The DP watch-keepers should ensure that this plot is always
kept up-to-date and that planned emergency procedures have been approved by
the diving supervisor to provide for the action to be taken in case of DP or other
emergency. These plans should be produced in advance of any diving operations
and be reviewed and modified as appropriate.

2D-2.4.10

Authority and Responsibility.
1. The Master of a vessel is ultimately responsible for the safety of the vessel

and all personnel working on or from it. He can veto the start, or order the
termination, of a diving operation through the diving supervisor.

2. DP Operators in charge of the DP system must be suitably trained and

experienced. The DP operator is responsible for the station-keeping of the
vessel, and must keep the other relevant control centers of the vessel informed
of changes in operational conditions and circumstances.

3. Master Diver/Dive Supervisors maintain control of all dive operations and

related activities. They maintain immediate communications with the DP

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2D-7

Operators. The Master Diver/Diving Supervisor is the only person who may
order the start of a diving operation. The Master Diver/Diving Supervisor is
also responsible for advising the DP operator of any status change in the diving
operation.
2D-2.4.11

2D-3

DP Casualties. A DP casualty occurs when the vessel is not able to maintain
desired heading and/or position, or when the DP system is degraded such that a
single point of failure could result in failure to maintain heading or position. The
most common causes of DP casualties are loss of position reference systems or
operator error. The most common results of DP casualties are drive off (when the
DP system mistakenly moves from the desired position or heading) or drift off
(dark ship, loss of thruster power).

GUIDELINES TO DETERMINE THE SUITABILITY OF A DP VESSEL

U.S. Navy personnel shall ensure that operational environmental conditions will
not exceed the vessel’s or the DP system’s capabilities. Embarked Navy personnel
must understand the DP vessel’s capabilities and identify the status of the DP
system by including indications provided when predetermined limits are being
approached. Indications shall be at the dive control station and on the bridge of the
Vessel of Opportunity (VOO).
2D-3.1

2D-3.1.1

VOO Selection. Prior to the vessel of opportunity (VOO) being selected, a Navy
team should test the ship’s functions, including the DP system underway to ensure
the systems are in good working condition. This allows Navy personnel to check
the condition of the ship and the proficiency of the crew. After a VOO has been
selected, all foreseeable emergencies relating to the diving operation shall be
identified and contingency plans established.
Vessel Suitability. The following is provided as a guide to ensure a DP vessel is

suitable for U.S. Navy diving operations:

1. A Failure Modes and Effects Analysis (FMEA) is required by Classification

Societies and accomplished during the classification/certification process and
should be available for review by U.S. Navy personnel. The FMEA should
include the following:

n Identification of back up or compensating equipment for each failure (i.e.
does it cover emergency situations that could occur during the mission?).
n A description of the major components of the DP system, including whether
individual thrusters/propellers can be taken off-line from the whole system.
n Identification of any significant failure modes that will affect the mission. If
so, are procedures are in place to mitigate the failures and have the procedures
been used and shown to be satisfactory.
n The method of detecting a failure or an impending failure.
n Effect of the failure on the ship’s station keeping ability.

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U.S. Navy Diving Manual — Volume 2

n Capability of position references for depth of water at dive site.
2. Review the FMEA for which components are most critical and check with the

ship’s Captain to see if there are any maintenance issues with them.

3. A risk assessment shall compare the planned operation against the FMEA to

ensure the system is compatible with the mission (i.e. water depth, currents,
waves/ swells, winds, etc.).

4. Technical evaluation of the DP Vessel. Conduct a general inspection of the

overall DP system including the Uninterrupted Power Supply (UPS) system to
verify adequacy for the dive mission.

5. Identify the position references that will be used in the DP system: Will subsea

position references and/or surface position references be required (i.e. taut
wire, hydro acoustic, GPS, or DGPS)?

NOTE:

Wire and depressor of taut wire system may interfere with diving
operations since a vertical wire and depressor are used to establish the
set point for the ship. If possible, inspect them and the lifting appliance
to ensure they are in good working order.
6. Review the DP capability plot to identify any positioning and heading

constraints for the DP vessel.

7. Will the diver be working on or near the bottom or a fixed structure?
8. What is the diver deployment and recovery location with respect to thrusters

and/or main propulsion?

9. Do the diver underwater communications interfere with acoustic positioning

systems?
10. Do satellite communication systems interfere with GPS/DGPS signals?
11. Are there any operation related external forces that could reduce station

keeping capabilities (i.e., salvage recovery or heavy lifts, helicopter wash on
wind sensors, etc.)?

12. Verify that there is documentation that shows that the DP vessel has the

appropriate Class Notation in accordance with a Classification Society and Flag
State. Ensure vessel is maintained in class and has no outstanding liabilities
against it.

13. Verify that appropriate authorities (Classification Society and owner) have

approved deck and supporting structure modifications for foundation loads
from the diving system, if modifications were made.

14. Review vessel DP history and crew qualifications/experience.
15. Review for reliability and proficiency (i.e. has the system experienced

significant down time and have there been operator errors?).

16. Test and operate the system while assessing the DP vessel’s ability to hold

position in depth of water at mission site (i.e. do all the alarms, monitors, and
displays operate properly?).

APPENDIX 2D — Guidance For U.S. Navy Diving on a Dynamic Positioning Vessel

2D-9

2D-4

GUIDELINES FOR ESTABLISHING AN OPERATIONAL PLAN FOR THE DP VESSEL

Operational planning is essential with agreement reached on all aspects of the
mission, including emergency procedures for any foreseeable contingencies. Both
the DP vessel crew and the U.S. Navy personnel need to be aware of the effects
of each other’s operations and emergency procedures and how they affect their
respective systems. The vessel crew and Navy personnel shall work together to
establish clear lines of communications and command and control. The responsibility
and authority of all personnel involved in the management of the diving operation
shall be clearly defined. Key DP vessel personnel include the Master, Chief Mate,
Chief Engineer, bridge watch standers, and DP operators. Key US Navy personnel
include the Officer in Charge, Master Diver, Diving Supervisor, Safety Officer, and
dive system operators.
Operational planning should include the following factors at a minimum:
1. Is the position of the work site close to the ocean bottom, surface hazards or

other obstructions?
2. Vessels maneuverability while in DP mode and requirement to move vessel

while Divers are deployed.

3. Expected weather conditions while on the dive site.
4. Predicted tide and current conditions while on the dive site.
5. Expected sea state and swells at dive site.
6. How to optimize vessel position over dive site.
7. Power of the DP vessel and thruster configuration for the dive mission.
8. Depth of water at and around the dive site. Identify if water is too deep or

shallow for proper operation of position references.

9. Location of position reference sensors on vessel. Are there any factors that

can affect their input/output while on station? (e.g., helicopter blade affecting
anemometer or obstruction on bottom interfering with taut wire depressor
location).

10. Time required to recover divers back to a safe location or the vessel and are

escape routes to get out of a hazardous condition impeded by subsea or surface
objects.

2D-5

SPECIFIC GUIDELINES FOR SURFACE SUPPLIED DIVING WHILE OPERATING
FROM A VESSEL IN THE DP MODE

“DP Mode” is defined as being the use of motive power (thrusters or propellers)
to position the ship over a dive site. The requirements are based on the premise
that at no time should the length of umbilical from the tending point to the diver
allow the diver to come into within 15 feet of the nearest thruster or propeller
that is in an operating mode. Great care is needed in the planning and execution
of shallow and surface oriented diving operations to minimize the effect of thrust
units on the divers. The effects of thrust unit wash or suction should be carefully
considered and precautions taken to guard against them particularly when the
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U.S. Navy Diving Manual — Volume 2

divers pass the potential wash zone. The use of thrust diagrams when planning
dives can also help. Inhibiting or deselecting certain thrusters may be necessary
and the resulting reduction in the vessel’s operational limitations should be taken
into account. Divers’ umbilical lengths and the manner of deploying them (i.e. over
the side, from a stage, etc.) should be so chosen that divers and their umbilical are
physically restrained from going to positions where they or their equipment could
come into contact with thrust units or be adversely affected by their wash. There is
no simple approach to the problem due to the differences encountered in the vessels
and worksites.
2D-5.1

Surface Supplied Diving. Surface supplied diving can be performed from a DP

vessel in the DP mode whether over the side or through the moon pool, if the
following conditions are met:

1. A diagram showing any hazards to the divers (such as thrusters, propellers,

rudders, and suctions) specific to each vessel shall be provided in both DP and
dive control to enable the DP operator and the Diving Supervisor to visualize
the relative position of the vessel, the deployment device, the divers in relation
to the worksite, and to plan operations accordingly. See Figure 2D-5.

2. Written procedures shall be prepared for emergency situations (i.e. changes in

alert level status, alarms, loss of communications, moving the vessel, etc.).

3. The Dive Team must be familiar with the vessel’s overall design and operating

characteristics (i.e., position of thrusters, propellers, intakes, obstructions, etc.)
with respect to the location of the dive station.

4. Divers’ umbilical’s shall be tended at all times. The tending point is defined as

the surface or in-water point from which the diver’s umbilical can be securely
tended. Where the planned excursion is such that the diver could be brought
within range of any of the physical hazards identified by the risk assessment
(such as vessel thrusters, propellers, suctions, etc.), his umbilical shall be
physically restrained at the tending point to prevent it from coming with 15
feet of such hazards for the primary divers and 10’ for the standby diver. Use
of a stage is required. The umbilical should be attached along the stage wire at
intervals of no greater than 50’.

5. Divers’ umbilical’s shall be marked every 25’ and at a point to identify distance

to closest hazard based on the planned depth of the dive.

6. The diver and standby diver shall be in direct communication with the Dive

Supervisor at all times.

7. The Dive Supervisor shall be provided with relevant DP alarms and

communications systems to the bridge and/or DP control station.

8. The topside tenders shall be able to listen to all communications between the

divers and the Dive Supervisor and shall be able to talk directly to the Dive
Supervisor.

2D-5.2

Umbilical Management. Tending rules shall follow the guidance of the USN Dive

Manual. Divers may be tended from the DP vessel or from the waterline via small
boat or stage. In the event the divers are tended from the DP vessel, ensure the
divers tending line remains outboard of the DP vessel’s hull and well clear of all

APPENDIX 2D — Guidance For U.S. Navy Diving on a Dynamic Positioning Vessel

2D-11

forms of motive power throughout the dive. Constant communication with the DP
vessel’s Master or helmsman shall be maintained throughout the dive, and the DP
vessel shall secure all forms of motive power in the event of divers inadvertent
surfacing within the 50 foot exclusion zone.

Figure 2D‑5. Safe Distance Chart.

Due to the danger of divers or their umbilical becoming drawn into the active
thrusters on a DP vessel, strict safety precautions must be maintained regarding
umbilical’s. The required precautions include marking the umbilical’s for length,
and ensuring a positive tend so that a primary diver cannot get closer than 15
feet to an active thruster or rudder, and the standby diver no closer than 10 feet.
This allows the standby diver to assist the diver if he becomes incapacitated or
fouled. Figures 2D-6 and 2D-7 provides an illustration to help determine maximum
umbilical lengths. When necessary for diver safety, non-critical thrusters may be
taken out of service.
2D-5.3

Surface Diving Requirements. The following conditions must be met to perform
surface diving from a DP vessel in the DP mode whether over the side or through
the moon pool:

In conjunction with the Vessel Master and DP operator completing the DP pre-dive
checklist (Figure 2D-8) checklist, the Dive Supervisor and or Diving Officer shall
complete the DP diving checklist (Figure 2D-9) for the vessel at the beginning of
each diving day, or each time the vessel moves location between diving operations.
At a minimum the following must be established and agreed upon:
1. The ships position for diving over the work site must be meticulously worked

out taking into account the drift pattern, currents, wind and the desired work
site with relation to the wreckage or underwater obstructions.

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U.S. Navy Diving Manual — Volume 2

2. Specific attention shall be placed on recovering the divers in the event of a drift

off or failure causing a loss of DP. Developing a DP failure “Escape Plan” is
critical. Most DP vessels rely on the main propulsion system, ships propellers
to maintain position in the event of a DP failure.

3. Always place the vessel in a position that will prevent the following should a

DP failure occur:

n Divers, stage or clump to drift under the ships propellers.
n Divers, stage or clump to be drug across the wreckage or debris field.
4. Ensure all parties completely understand and are in agreement of the DP failure

escape plan.

5. Utilization of an open-bottom bell with emergency on-board gas. A stage with

may be substituted for an open-bottom bell.

6. A tending point on the surface or in-water from which the diver’s umbilical

can be securely tended. Allowable tending methods need to be addressed in the
mission ORM and may include the following items:

n Tenders located on the vessel.
n A tender located in a stage above the surface.
n An unmanned in water tending point (e.g. open-bell, divers stage, divers
hoop, golden gate).
n An in-water tender.
n The tending point, stage or open bell must be able to maintain relative
position with the vessel should DP failure occur. (hanging off the bottom).
n Divers (and, if utilized, in-water tender) to have access to surface.
n The bell umbilical and/or diver’s umbilical supplying the wet bell and/or
divers with appropriate services must be secured to the main lift wire (or
secondary lift wire) using quick connecting clips every 25-50’depending on
location of hazards.
n The Diver’s (excursion) umbilical is secured to the wet bell or stage so that
it is at least 15 feet shorter than the distance to the closest hazard.
n The umbilical must be appropriately marked.
n Bell umbilical and surface umbilical management plan (should be filed with
ORM).
n The diving supervisor must be provided with relevant DP alarms and
communications systems to the bridge and/or DP control station.

APPENDIX 2D — Guidance For U.S. Navy Diving on a Dynamic Positioning Vessel

2D-13

n The topside tenders must be able to hear all communications between the
divers and the supervisor and must be able to talk directly to the supervisor.
n Standby diver’s umbilical requirements are the same as those for the divers.
7. Umbilical Shackle Discussion. There are several ways to set up the umbilical

shackles in order to maintain diver safety. At a minimum, there must be a
“first shackle,” a “max working shackle,” and shackles past the “first shackle”
every 50 feet. It is recommended to place shackles every 25 feet past the “first
shackle” for marking the length of the umbilical and for greater control over
the amount of umbilical off the stage wire at depth.

n The “first shackle” is placed on the umbilical to ensure the primary divers
will not get closer than 15 ft to the nearest hazard when the divers are at the
waterline, and the standby diver will not get closer than 10 feet to the nearest
hazard when the standby diver is at the waterline. A “short stay” does not
fulfill this requirement.
n The “max working shackle” is placed on the umbilical to ensure the primary
divers will not get closer than 15 ft to the nearest hazard when the stage or
bell is at the working depth, and the standby diver will not get closer than
10 feet to the nearest hazard when considering the distance from the stage
or bell. It is recommended that the “max working shackle” be marked in
such a way to distinguish it from all other shackles and be clearly visible, i.e.
painted international orange.
n Standby diver’s umbilical must be a minimum of 5 feet longer than the
primary diver’s umbilical in order to provide assistance in the case of an
emergency. There are many diving situations (i.e. large sunken debris or
wreckage) where it may be prudent to shorten the primary diver’s umbilical.
This will give standby diver more distance to work with, so there is less of a
chance that standby will be unable to reach the primary divers. For example,
the primary diver’s umbilical can be set so that the primary divers will not
get closer than 25 ft to the nearest hazard, while standby diver’s umbilical
will stay set at 10 ft away from the nearest hazard. This gives standby diver
15 ft, vice 5 ft, to provide assistance.
n A “short stay” is an optional way to ensure divers stay on the stage and is
recommended when diving in strong current. The “short stay” is a shackle
placed 6-8 feet from the end of the umbilical. The diver is able to clip into
the stage to ensure he remains on the stage while traveling through the water
column.
n The shackles can be clipped and unclipped from the stage wire as the divers
are traveling, or the divers can coil the length of umbilical between the “short
stay” and “max working shackle.” In the later method, the diver will unclip
his short stay once the stage or bell is at the working depth, and have the
length of the coil available to conduct work out to either the “first shackle”
or “max working shackle.”

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U.S. Navy Diving Manual — Volume 2

WARNING:

The divers and dive supervisor shall clearly communicate when removing
and attaching shackles.
8. Recommended ways to mark an umbilical. Utilize shackles every 25 feet past

the “first shackle” and place a piece of tape on the shackle displaying the length.
This method allows the umbilical to be set up for a particular vessel, without
much alteration to the umbilical required when the planned depth is changed.

NOTE:

Standby launch and recovery procedures shall be documented and
addressed during the pre-dive briefings.

n Standby diver can be launched from the surface to free swim down to the
divers stage as long as he is clipped into the primary or secondary lift wire
for the working divers.
n Standby diver shall pass thru the bail of the working divers stage before
proceeding out to recover the affected diver/s.
n Written procedures must be prepared for emergency situations (e.g. changes
in alert-level status, alarms, loss of communications, moving the vessel,
etc.).
n The dive crew must be familiar with the vessel’s overall design and operating
characteristics (e.g. position of thrusters, propellers, intakes, obstructions)
with respect to the location of the dive station.
WARNING:

2D-5.3.1

During diving operations at no time shall the open bell, diver’s stage or
clump be allowed to come in contact with the sea floor. The open bell,
divers stage and clump shall be located above all underwater structures
or debris located in the proximity of the diving operations to prevent
fouling in the event of a run-off or black ship event.
Additional Requirements. The following additional requirements for surface
supplied and saturation diving operations conducted from a vessel are in effect only
when the vessel is operating in the DP mode. “DP mode” is defined as whenever
there is any form of motive power in operation, e.g. thrusters or propellers, which
automatically maintains the vessel’s position (fixed or a predetermined track) by
means of thruster force.
1. The requirements are based on the premise that at no time should the length

of umbilical from the tending point to the diver allow the diver to come into
contact with the nearest thruster or propeller or rudder that is in operating mode.
Extreme care is needed in the planning and execution of shallow and surfaceoriented diving operations to minimize the effect of thrust units on the divers.
The effects of thrust unit wash or suction should be carefully considered, and
precautions should be taken to guard against them, particularly when the bell
or divers pass the potential wash zone.

2. The use of thrust diagrams when planning dives can also help. Inhibiting or

deselecting certain thrusters may be necessary, and the resulting reduction

APPENDIX 2D — Guidance For U.S. Navy Diving on a Dynamic Positioning Vessel

2D-15

in the vessel’s operational limitations should be taken into account. Divers’
umbilical lengths and the manner of deploying them (e.g. over the side, from
the bell, etc.) should be so chosen that divers and their umbilical are physically
restrained from going to positions where they or their equipment could come
into contact with the thrust units or be adversely affected by their wash
(Figure 2D-5). Furthermore, care should always be taken to prevent umbilical
developing a bight, and to respond at once to any indications of a diver being in
difficulty, such as unusual tension on or at the angle of the umbilical.

Safe Distance 150 fsw

Figure 2D‑6. Illustration of Maximum Umbilical Lengths.

2D-5.4

Selection of DP Vessels of Opportunity for Diving Operations. The following
references and check list are provided to assist in determining if a DP vessel is
suitable for conducting Navy surface supplied diving operations.

n International Marine Contractors Association (IMCA) D 035 September
2004, Guidance on the Selection of Vessels of Opportunity for Diving
Operations (www.imca-int.com).
n IMO Maritime Safety Committee Circular 645 Guidelines for Vessels with
Dynamic Positioning Systems.
n IMCA M 103 Guidelines for the Design and Operation of Dynamically
Positioned Vessels (www.imca-int.com).
n IMCA M 109 Rev. 1 A Guide to DP-related documentation for DP Vessels.
n ABS Pub 191 Guide for Dynamic Positioning Systems, July 2014 (http://
ww2.eagle.org/content/dam/eagle/rules-and-guides/current/other/191_
dpsguide/DPS_Guide_e-July14.pdf).
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U.S. Navy Diving Manual — Volume 2

n IMCA M 134 Comparison of Moored versus Dynamically Positioned Diving
Support Vessels.
n Association Of Diving Contractors International (ADCI) International
Consensus Standards For Commercial Diving And underwater Operations,
6.1 Edition, Chapter 8.
n Department Of Homeland Security, U. S. Coast Guard [Docket No.
USCG–2011–1106] Dynamic Positioning Operations Guidance for Vessels
Other Than Mobile Offshore Drilling Units Operating on the U.S. Outer
Continental Shelf.
n DNV-RP-E307, Dynamic Positioning Systems -Operation Guidance January
2011.

APPENDIX 2D — Guidance For U.S. Navy Diving on a Dynamic Positioning Vessel

2D-17

Safe Distance 100 fsw

Figure 2D‑7. Illustration of Maximum Umbilical Lengths (1 of 3).
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U.S. Navy Diving Manual — Volume 2

Safe Distance 150 fsw

Figure 2D‑7. Illustration of Maximum Umbilical Lengths (2 of 3).
APPENDIX 2D — Guidance For U.S. Navy Diving on a Dynamic Positioning Vessel

2D-19

Safe Distance 200 fsw

Figure 2D‑7. Illustration of Maximum Umbilical Lengths (3 of 3).
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U.S. Navy Diving Manual — Volume 2

Vessel Section Checklist for Navy Surface Supplied Diving Operations
from a Dynamically Positioned Vessel
#

ACTION

1.

Is the vessel classed DP2 or DP3 by a member of the International Association of Classification Societies (IACS)?
Classification Society: __________________
Classification: _________________________
Date: _________
Date of most recent DP Trials: ____________

2.

Verify the most recent Failure Modes and Effects Analysis is
complete and reviewed by the classification society.
Date: __________________

3.

Is the vessel capable of performing the desired mission based
on DP Capability Plots and Footprint Plots?

4.

If feasible, conduct underway DP Sea Trials

5.

Review the DP Operations Manual.

6.

Obtain a copy of the thruster and sea-suction position diagrams
for the vessel.

7.

Are DP Operators and the Master of the vessel qualified and
experienced with the DP system? Review certificates.

8.

Review the DP casualty reports. Is the system reliable? Are all
identified discrepancies corrected?

9.

Check the DP alarm system: Green, yellow and red (flashing)
alarms visible at Dive Side? Audible alarms for yellow and red
loud and clear? Capable of being silenced?

10.

Check the primary and secondary voice communication system
between DP Control and the Dive Site. (ROV operator and
crane operator also if applicable)

11.

Is sufficient deck space available to the dive system and mission?

YES

NO

NA

COMMENTS

12.. Is sufficient electrical power of required voltage, cycles, amperage available for the mission equipment?
13.. Is sufficient hydraulic power, water pressure and pressurized
air available for the mission?
14.. Is there sufficient sewage capacity for the anticipated personnel onboard and mission duration?
15.. Is there sufficient potable water storage capacity and distilling
capacity for the anticipated personnel onboard and mission
duration?
16.. Is there a Moon Pool for diver entry?
Dimensions? ____________________
17.

Are diver stage/bell davits available/classified for at sea personnel lifts?

18.

Is there an onboard crane suitable for the operation? If not, can
a crane be loaded/installed for the mission?
Capacity? _____________
Depth hook can be deployed? _______________
Heave compensated? ______

19.

What are the helicopter capabilities of the vessel?

20.

Is there a Fast Rescue Craft with qualified operators onboard?

21.

What other small craft are available or can be loaded, launched
and recovered?

22.

Is the adequate ship to ship and ship to shore communications,
both radio and satellite, including broadband internet?

Figure 2D‑8. Vessel Section Checklist for Navy Surface Supplied Diving Operations from a DP Vessel.
APPENDIX 2D — Guidance For U.S. Navy Diving on a Dynamic Positioning Vessel

2D-21

Pre Dive Check List for Navy Surface Supplied Diving Operations
from a Dynamically Positioned Vessel
Vessel Name: _________________________________ Date: ________________________
#

ACTION

X

COMMENTS

NOTE: Conduct this checklist during the vessels DP Field Arrival Checklist/500m Checks
1.

See Figure 2D-5. Refer to thruster/sea suction diagrams. Determine distance from
stage or bell to closest sea suctions and thrusters.
• Primary dive umbilical lengths cannot allow divers to get closer than 15 feet from
the closest hazard.
• Standby dive umbilical length cannot allow diver to get closer than 10 feet from
the closest hazard.

2.

Verify vessel conducts satisfactory Drift Test.

3.

Determine position and heading requirements for dive operations.

4.

Review/verify the Position Plot, (box move) Figure (1)

5.

Verify that the DP Parameters are satisfactory to support diving operations.
a.

Speed setting: ___________________; (.28 knots maximum recommended)

b.

Turn rate setting__________________; (15 degrees maximum recommended)

c.

Position warning and alarm setting (recommended):
• Warning: 2 meters;
• Alarm: 4 meters

d.

Heading warning and alarm setting (recommended)
• Warning: 3 degrees
• Alarm: 5 degrees

6.

Review the DP Capabilities Plot to ensure the position and heading are well
within the capability of the DP system in the current and anticipated environmental conditions (wind, current, weather forecast, etc.) Average thruster power required:________________ (15-30% recommended to hold station) Figure (2)

7.

Develop Operations Plot displaying the relative positions of the vessel, the bell/dive
stage, divers, the worksite and any known obstruction (e.g., sunken objects, other vessels, mooring wires, etc.) together with vessels heading and wind direction and speed
up to date at the DP control position. Figure (3)

8.

Dive station should be located at or near the vessels center of rotation. To preform
heading changes while divers are in the water, ensure the pivot point is programed for
the stage location over the side of the vessel.

9.

Test DP alarm systems at all stations:
a.

Verify Steady Green light.

b.

Verify Yellow light.

c.

Verify Red light with audible alarm capable of being silenced.

10.

Test primary and secondary communications between the Dive Supervisor and DP
Operator. If possible or available test tertiary communications.

11.

Vessel satisfactory completed Field Arrival/500 meter checks on the DP system and
moves to desired position and heading.

12.. Verify vessel is set in DP mode and stable, holding position on location.

NOTE: If vessel is using 65% power sustained to maintain position on station discontinue diving
operations.
Retain a copy of the following ships DP documents each time DP Field Arrival checks are conducted:
• DP Field Arrival Checks
• DP Position Plot
• DP Capabilities Plot
• DP Operations Plot
Dive Supervisor/Dive Officer: _________________________________________Date:_____________

Figure 2D‑9. Pre Dive Check List for Navy Surface Supplied Diving Operations from a DP Vessel (1 of 2).
2D-22

U.S. Navy Diving Manual — Volume 2

Figure 1

Figure 2

Figure 3

Figure 2D‑9. Pre Dive Check List for Navy Surface Supplied Diving Operations
from a DP Vessel (2 of 2).
APPENDIX 2D — Guidance For U.S. Navy Diving on a Dynamic Positioning Vessel

2D-23

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2D-24

U.S. Navy Diving Manual — Volume 2

VOLUME 3

Mixed Gas
Surface Supplied
Diving Operations
12

Surface-Supplied
Mixed Gas Diving

13

Saturation Diving

14

Breathing Gas Mixing
Procedures

U.S. NAVY DIVING MANUAL

PAGE LEFT BLANK INTENTIONALLY

Volume 3 - Table of Contents
Chap/Para
12

Page
SURFACE-SUPPLIED MIXED-GAS DIVING DIVING

12-1 INTRODUCTION.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 12-1
12-1.1

Purpose. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 12-1

12-1.2

Scope .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 12-1

12-2 OPERATIONAL CONSIDERATIONS.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 12-1
12-2.1

Limits. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 12-1

12-2.2

Personnel .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 12-2

12-2.3

Additional Considerations.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 12-2
12‑2.3.1 Emergency Gas Supply.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 12-3
12‑2.3.2 Water Temperature. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 12-3
12‑2.3.3 Diver Training.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 12-3
12‑2.3.4 Diver Fatigue .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 12-3
12‑2.3.5 Ascent to Altitude.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 12-3

12-3 MIXED GAS DIVING EQUIPMENT/SYSTEMS .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 12-3
12-3.1

Gas Mixtures.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 12-4

12-3.2

Flyaway Dive System (FADS) III Mixed Gas System (FMGS) .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 12-4

12-4 SURFACE-SUPPLIED HELIUM-OXYGEN DESCENT AND ASCENT PROCEDURES.  .  .  .  .  . 12-4
12-4.1

Selecting the Bottom Mix .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 12-6

12-4.2

Selecting the Decompression Schedule.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 12-6

12-4.3

Travel Rates and Stop Times.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 12-7

12-4.4

Decompression Breathing Gases.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 12-7

12-4.5

Special Procedures for Descent with Less than 16 Percent Oxygen.  .  .  .  .  .  .  .  .  .  .  .  .  . 12-7

12-4.6

Aborting Dive During Descent. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 12-8

12-4.7

Procedures for Shifting to 50 Percent Helium/50 Percent Oxygen at 90 fsw.  .  .  .  .  .  .  . 12-9

12-4.8

Procedures for Shifting to 100 Percent Oxygen at 30 fsw .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 12-9

12-4.9

Air Breaks at 30 and 20 fsw .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 12-9

12-4.10 Ascent from the 20-fsw Water Stop .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 12-10
12-4.11 Surface Decompression on Oxygen (SurDO2).  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 12-10
12-4.12 Variation in Rate of Ascent .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 12-11
12‑4.12.1 Early Arrival at the First Stop.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 12-11
12‑4.12.2 Delays in Arriving at the First Stop.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 12-11
12‑4.12.3 Delays in Leaving a Stop or Arrival at the Next Stop.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 12-11
12‑4.12.4 Delays in Travel from 40 fsw to the Surface for Surface Decompression..  12-12

Table of Contents­—Volume 3

3–i

Chap/Para

Page

12-5 SURFACE-SUPPLIED HELIUM-OXYGEN EMERGENCY PROCEDURES .  .  .  .  .  .  .  .  .  .  .  .  .  . 12-12
12-5.1

Bottom Time in Excess of the Table .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 12-12

12-5.2

Loss of Helium-Oxygen Supply on the Bottom.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 12-13

12-5.3

Loss of 50 Percent Oxygen Supply During In-Water Decompression .  .  .  .  .  .  .  .  .  .  .  . 12-13

12-5.4

Loss of Oxygen Supply During In-Water Decompression. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 12-13

12-5.5

Loss of Oxygen Supply in the Chamber During Surface Decompression. . . . . . . . . . 12-14

12-5.6

Decompression Gas Supply Contamination.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 12-15

12-5.7

CNS Oxygen Toxicity Symptoms (Nonconvulsive) at the 90-60 fsw Water Stops .  .  . 12-15

12-5.8

Oxygen Convulsion at the 90-60 fsw Water Stop. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 12-16

12-5.9

CNS Toxicity Symptoms (Nonconvulsive) at 50-and 40-fsw Water Stops... . . . . . . . . 12-17

12-5.10 Oxygen Convulsion at the 50-40 fsw Water Stop.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 12-18
12-5.11 CNS Oxygen Toxicity Symptoms (Nonconvulsive) at 30- and 20-fsw Water Stops....  12-18
12-5.12 Oxygen Convulsion at the 30- and 20-fsw Water Stop.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 12-19
12-5.13 Oxygen Toxicity Symptoms in the Chamber.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 12-19
12-5.14 Surface Interval Greater than 5 Minutes. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 12-19
12-5.15 Asymptomatic Omitted Decompression..  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 12-20
12‑5.15.1 Omitted Decompression Stop Deeper Than 50 fsw.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 12-21
12-5.16 Symptomatic Omitted Decompression.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 12-22
12-5.17 Light Headed or Dizzy Diver on the Bottom .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 12-22
12‑5.17.1 Initial Management.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 12-22
12‑5.17.2 Vertigo .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 12-22
12-5.18 Unconscious Diver on the Bottom. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 12-23
12-5.19 Decompression Sickness in the Water.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 12-24
12‑5.19.1 Decompression Sickness Deeper than 30 fsw. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 12-24
12‑5.19.2 Decompression Sickness at 30 fsw and Shallower.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 12-24
12-5.20 Decompression Sickness During the Surface Interval .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 12-25
12-6 CHARTING SURFACE SUPPLIED HELIUM OXYGEN DIVES.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 12-25
12-6.1

Charting an HeO2 Dive.. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 12-25

12-7 DIVING AT ALTITUDE .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 12-26

13

SATURATION DIVING

13-1 INTRODUCTION.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-1
13-1.1

Purpose. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-1

13-1.2

Scope .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-1

13-2 DEEP DIVING SYSTEMS.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-1

3–ii

U.S. Navy Diving Manual—Volume 3

Chap/Para

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13-2.1

Applications. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-1

13-3 BASIC COMPONENTS OF THE U.S. NAVY FLY AWAY SATURATION DIVE SYSTEM .  .  .  .  . 13-2
13-3.1

Dive Bell .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-2
13‑3.1.1
13‑3.1.2
13‑3.1.3
13‑3.1.4
13‑3.1.5
13‑3.1.6
13‑3.1.7

13-3.2

13-3
13-3
13-3
13-3
13-4
13-5
13-5

Deck Decompression Chamber (DDC).  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-5
13‑3.2.1
13‑3.2.2
13‑3.2.3
13‑3.2.4
13‑3.2.5

13-3.3

Gas Supplies .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Dive Bell Pressurization/Depressurization System .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Dive Bell Life-Support System.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Electrical System.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Communications System.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Dive Bell Umbilical.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Diver Hot Water System. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .

DDC Life-Support System (LSS).  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Potable Water/Sanitary System.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Fire Suppression System.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Control Van (Control).  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Gas Supply Mixing and Storage. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .

13-5
13-5
13-5
13-5
13-6

Dive Bell Launch and Recovery System (LARS) .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-6
13‑3.3.1 SAT FADS LARS Characteristics.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-6

13-3.4

Saturation Mixed-Gas Diving Equipment .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-7

13-4 U.S. NAVY SHORE BASED SATURATION FACILITIES.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-7
13-4.1

Navy Experimental Diving Unit (NEDU), Panama City, FL.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-7

13-5 DIVER LIFE-SUPPORT SYSTEMS .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-8
13-5.1

Introduction.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-8

13-6 THERMAL PROTECTION SYSTEM. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-10
13-6.1

Diver Heating .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-10

13-6.2

Inspired Gas Heating .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-10

13-7 SATURATION DIVING UNDERWATER BREATHING APPARATUS. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-11
13-7.1

Commercial Off-the-Shelf Closed-Circuit UBA.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-11

13-8 UBA GAS USAGE .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-12
13-8.1

Specific Dives.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-12

13-8.2

Emergency Gas Supply Duration.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-13

13-8.3

Gas Composition. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-14

13-9 SATURATION DIVING OPERATIONS.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-15
13-9.1

Introduction.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-15

13-10 OPERATIONAL CONSIDERATIONS.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-15
13-10.1 Dive Team Selection.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-15
13-10.2 Mission Training .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-15

Table of Contents­—Volume 3

3–iii

Chap/Para

Page

13-11 SELECTION OF STORAGE DEPTH .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-16
13-12 RECORDS. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-16
13-12.1 Command Diving Log.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-16
13-12.2 Master Protocol.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-17
13‑12.2.1 Modifications .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-17
13‑12.2.2 Elements .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-17
13-12.3 Chamber Atmosphere Data Sheet .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-17
13-12.4 Service Lock.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-17
13-12.5 Machinery Log/Gas Status Report .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-17
13-12.6 Operational Procedures (OPs).. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-18
13-12.7 Emergency Procedures (EPs). .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-18
13-12.8 Individual Dive Record .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-18
13-13 LOGISTICS.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-18
13-14 DDC AND PTC ATMOSPHERE CONTROL.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-18
13-15 GAS SUPPLY REQUIREMENTS . .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-19
13-15.1 UBA Gas.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-19
13-15.2 Emergency Gas .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-19
13-15.3 Treatment Gases .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-20
13-16 ENVIRONMENTAL CONTROL. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-20
13-17 FIRE ZONE CONSIDERATIONS .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-21
13-18 HYGIENE .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-22
13-18.1 Personal Hygiene.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-22
13-18.2 Prevention of External Ear Infections.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-22
13-18.3 Chamber Cleanliness.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-22
13-18.4 Food Preparation and Handling .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-23
13-19 ATMOSPHERE QUALITY CONTROL.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-23
13-19.1 Gaseous Contaminants. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-23
13-19.2 Initial Unmanned Screening Procedures. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-23
13-20 COMPRESSION PHASE .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-24
13-20.1 Establishing Chamber Oxygen Partial Pressure.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-25
13-20.2 Compression to Storage Depth. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-26
13-20.3 Precautions During Compression.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-27
13-20.4 Abort Procedures During Compression .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-27
13-21 STORAGE DEPTH.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-27
13-21.1 Excursion Table Examples .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-31

3–iv

U.S. Navy Diving Manual—Volume 3

Chap/Para

Page
13-21.2 Dive Bell Diving Procedures.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-32
13‑21.2.1 Dive Bell Deployment Procedures.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-32

13-22 DEEP DIVING SYSTEM (DDS) EMERGENCY PROCEDURES .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-33
13-22.1 Loss of Chamber Atmosphere Control .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-34
13‑22.1.1
13‑22.1.2
13‑22.1.3
13‑22.1.4
13‑22.1.5

Loss of Oxygen Control.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Loss of Carbon Dioxide Control.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Atmosphere Contamination.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Interpretation of the Analysis .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Loss of Temperature Control .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .

13-34
13-34
13-34
13-34
13-35

13-22.2 Loss of Depth Control.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-35
13-22.3 Fire in the DDC.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-35
13-22.4 Dive Bell Emergencies .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-36
13-23 SATURATION DECOMPRESSION .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-36
13-23.1 Upward Excursion Depth .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-36
13-23.2 Travel Rate.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-36
13-23.3 Post-Excursion Hold.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-36
13-23.4 Rest Stops. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-36
13-23.5 Saturation Decompression Rates .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-36
13-23.6 Atmosphere Control at Shallow Depths .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-37
13-23.7 Saturation Dive Mission Abort.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-38
13‑23.7.1 Emergency Cases .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-38
13‑23.7.2 Emergency Abort Procedure .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-39
13-23.8 Decompression Sickness (DCS). .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-40
13‑23.8.1 Type I Decompression Sickness .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-40
13‑23.8.2 Type II Decompression Sickness.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-40
13-24 POSTDIVE PROCEDURES .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-41

14

BREATHING GAS MIXING PROCEDURES

14-1 INTRODUCTION.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 14-1
14-1.1

Purpose. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 14-1

14-1.2

Scope .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 14-1

14-2 MIXING PROCEDURES.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 14-1
14-2.1

Mixing by Partial Pressure .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 14-1

14-2.2

Ideal-Gas Method Mixing Procedure. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14-2

14-2.3

Adjustment of Oxygen Percentage.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 14-5
14‑2.3.1 Increasing the Oxygen Percentage .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 14-5
14‑2.3.2 Reducing the Oxygen Percentage.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 14-6

14-2.4

Continuous-Flow Mixing.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 14-7

Table of Contents­—Volume 3

3–v

Chap/Para

Page
14-2.5

Mixing by Volume .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 14-7

14-2.6

Mixing by Weight. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 14-8

14-3 GAS ANALYSIS .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 14-8

3–vi

14-3.1

Instrument Selection.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 14-9

14-3.2

Techniques for Analyzing Constituents of a Gas. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 14-9

U.S. Navy Diving Manual—Volume 3

Volume 3 - List of Illustrations
Figure

Page

12-1

FADS III Mixed Gas System (FMGS) .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 12-5

12-2

FMGS Control Console Assembly.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 12-5

12-3

Dive Team Brief for Divers. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 12-6

12-4

Diving Chart. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 12-27

12-5

Completed HeO2 Diving Chart: Surface Decompression Dive .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 12-28

12-6

Completed HeO2 Diving Chart: In-water Decompression Dive.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 12-29

12‑7

Completed HeO2 Diving Chart: Surface Decompression Dive with Hold
on Descent and Delay on Ascent .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 12-30

13-1

SAT FADS System .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-1

13-2

SAT FADS Dive Bell Exterior. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-2

13-3

SAT FADS DDC Interior .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-3

13-4

SAT FADS Control Van.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-6

13-5

DIVEX SLS MK-4 Helmet with Backpack .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-7

13-6

MK 22 MOD 0 with Hot Water Suit, Hot Water Shroud, and ComeHome Bottle.  .  .  .  .  .  .  .  .  .  .  .  . 13-7

13-7

NEDU’s Ocean Simulation Facility (OSF).  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-8

13-8

NEDU’s Ocean Simulation Facility Saturation Diving Chamber Complex. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-9

13-9

NEDU’s Ocean Simulation Facility Control Room.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-9

13-10

Dive Bell and LARS System .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-18

13-11

Inside Dive Bell.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-28

13-12

PTC Placement Relative to Excursion Limits .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-33

13‑13

Saturation Decompression Sickness Treatment Flow Chart.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-41

14‑1

Mixing by Cascading.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 14-3

14‑2

Mixing with Gas Transfer System .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 14-4

List of Illustrations—Volume 3

3–vii

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U.S. Navy Diving Manual—Volume 3

Volume 3 - List of Tables
Table

Page

12‑1

Surface Supplied Mixed Gas Dive Team.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 12-2

12‑2

Pneumofathometer Correction Factors.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 12-6

12‑3

Management of Asymptomatic Omitted Decompression. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-21

12‑4

Surface-Supplied Helium-Oxygen Decompression Table.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 12-31

13‑1

Guidelines for Minimum Inspired HeO2 Temperatures for Saturation Depths
Between 350 and 1,500 fsw .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-11

13‑2

Typical Saturation Diving Watch Stations.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-16

13‑3

Chamber Oxygen Exposure Time Limits.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-19

13‑4

Treatment Gases. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-20

13‑5

Limits for Selected Gaseous Contaminants in Saturation Diving Systems.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-24

13‑6

Saturation Diving Compression Rates. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-26

13‑7

Unlimited Duration Downward Excursion Limits.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-29

13‑8

Unlimited Duration Upward Excursion Limits .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-30

13‑9

Saturation Decompression Rates.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-36

13‑10

Emergency Abort Decompression Times and Oxygen Partial Pressures.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-39

List of Tables—Volume 3

3–ix

Chap/Para

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U.S. Navy Diving Manual—Volume 3

CHAPTER 12

Surface-Supplied Mixed Gas Diving
12-1

INTRODUCTION
12-1.1

Purpose. The purpose of this chapter is to familiarize divers with the U.S. Navy

surface-supplied mixed gas diving procedures.

12-1.2

Scope. Surface-supplied, open-circuit mixed gas diving is conducted with helium-

oxygen mixtures supplied from the surface by a flexible hose. Surface-supplied
mixed gas diving is particularly suited for operations beyond the depth limits of
air diving, yet short of the depths and times requiring the use of a saturation diving
system. Surface-supplied mixed gas diving is also useful in the air diving range
when freedom from nitrogen narcosis is required.

12-2

OPERATIONAL CONSIDERATIONS

Due to extended decompression obligations, mixed gas diving can be hazardous
if not properly planned and executed. Seemingly minor problems can quickly
escalate into emergency situations, leaving limited time to research dive protocols
or operational orders to resolve the situation. Planning aspects that are unique
to surface-supplied mixed gas diving include the logistics of providing several
different gas mixtures to the diver, providing for the harsh and physically demanding
environment of deep water diving, and repetitive diving limitations as discussed
below.
12-2.1

Limits. The normal operational limit for surface-supplied mixed gas diving is 300

fsw for 30 minutes. The maximum working limit is 380 fsw. These limitations
are based on a number of interrelated factors such as decompression obligations,
duration of gas supply, oxygen tolerance, and the possibility of nitrogen narcosis
when using emergency gas (air).

Within each decompression table (Table 12-4), an exceptional exposure limit
line separates normal working dives from dives that are considered exceptional
exposure. Excep­
tional exposure dives require lengthy decompression and are
associated with an increased risk of decompression sickness and exposure to the
elements. Excep­tional exposures should be undertaken only at the Commanding
Officer’s discretion in an emergency. Planned exceptional exposure dives require
prior approval in accordance with OPNAVINST 3150.27 (series).
Repetitive diving is not allowed in surface-supplied helium-oxygen diving, except
as outlined in paragraph 12‑4.6. Following a “no-decompression dive” the diver
must wait 12 hours before making a second dive. Following a decompression dive,
the diver must wait 18 hours. To minimize pulmonary oxygen toxicity effects, a
diver should take a one day break after four consecutive days of diving.

CHAPTER 12 — Surface-Supplied Mixed Gas Diving

12-1

Table 12‑1. Surface Supplied Mixed Gas Dive Team.
Deep-Sea (KM-37 NS)
Designation

One Diver

Two Divers

Diving Officer

1
(Note 1)

1
(Note 1)

Master Diver

1
(Notes 1 and 2)

1
(Notes 1 and 2)

Diving Supervisor

1
(Note 1)

1
(Note 1)

Diving Medical Officer

(Note 5)

(Note 5)

1

1

Diver

1
(Note 3)

2
(Note 3)

Standby Diver

1
(Note 3)

1
(Note 3)

Tender

2
(Note 4)

3
(Note 4)

Timekeeper/Recorder

1
(Note 3)

1
(Note 3)

Rack Operator

1
(Note 3)

1
(Note 3)

Winch Operator

1
(Note 4)

1
(Note 4)

Console Operator

1
(Note 3)

1
(Note 3)

12

14

Diving Medical Technician

Total Personnel Required

Notes:
1.

This station shall be manned by a formally trained (NDSTC) mixed gas diver.

2.

A Master Diver shall be on station for all mixed gas diving. A Master Diver may serve as the Diving Officer (if
designated in writing by the Commanding Officer) . However, no one person may serve in more than one position.

3.

This station shall be manned by a formally trained (NDSTC) surface supplied diver.

4.

When circumstances require the use of a non-diver, the Diving Supervisor shall ensure the assigned personnel are
thoroughly instructed in the required duties.

5.

A Diving Medical Officer should be on the dive station for all mixed gas diving. A Diving Medical Officer is required
on dive station for all planned exceptional exposure dives and dives planned to exceed normal working limits.

6.

When conducting no-decompression dives for training a Diving Officer is not required.

12-2.2

Personnel. Due to the size and complexity of deep dive systems and the increased

risk of deep diving, selecting a properly trained team is critical. Table 12-1 lists
the minimum manning required for surface supplied mixed gas diving. Increases

12-2

U.S. Navy Diving Manual — Volume 3

in the minimum may be required for safe and effective diving based on ORM
and specific mission requirements. It is critical to ensure that formally qualified
personnel are assigned. The Diving Supervisor must verify the qualification level
of each team member. A detailed and comprehensive watch station qualification
program is paramount for successful mixed gas diving.
12-2.3

Additional Considerations

12-2.3.1

Emergency Gas Supply. The EGS shall meet the requirements listed in chapter
8 with the following exceptions: All divers shall be equipped with an EGS. The
EGS shall be charged with bottom mixture unless the bottom mixture contains less
than 16 percent oxygen. In this case the EGS gas mixture shall range from 15 to 17
percent oxygen.

12-2.3.2

Water Temperature. Hypothermia is an ever present concern during long, deep

dives. Mixed gas diving operations often involve prolonged dives requiring
lengthy decompression. Divers must be prepared to work at low temperatures and
for long periods of time. A hot water suit is preferred for surface-supplied dives in
cold water. When diving mixed gas in water below 40 degrees Fahrenheit keeping
the diver warm is a life support consideration. Two water heaters should be setup
to supply a common manifold that allows shifting between a primary and a backup
water heater. (A salvage air manifold works well for this purpose).
Exposure to extreme surface conditions prior to a mixed gas dive may leave the
diver in a thermally compromised state. A diver who has been exposed to adverse
environmental conditions should not be considered for mixed gas diving until
normal core temperature is returned.

12-2.3.3

Diver Training. Training must be given the highest command priority. The
command that dives infrequently, or with insufficient training and few workup dives between operations, will be ill prepared in the event of an emergency.
The dive team must be exercised on a regular diving schedule with challenging
emergency drills to remain proficient not only in the water but on topside support
tasks as well. Cross-training ensures that divers are qualified to substitute for one
another when circumstances warrant.

12-2.3.4

Diver Fatigue. Mixed gas dives shall not be conducted using fatigued divers.
Fatigue will predispose a diver to decompression sickness and a tired diver is not
mentally alert. The Diving Supervisor must ensure that all mixed gas divers have
at least 8 hours of sleep within the last 24 hours before diving. See paragraph
6-6.3.3 for more information on fatigue.

12-2.3.5

Ascent to Altitude. Following a no-decompression dive, the diver must wait 12
hours before ascent to altitude. Following a decompression dive, the diver must
wait 24 hours.

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12-3

MIXED GAS DIVING EQUIPMENT / SYSTEMS

Mixed gas diving requires a predetermined supply of breathing gases and carbon
dioxide absorbent material. Operations must be planned thoroughly to determine
usage requirements in order to effectively obtain required supplies in port or at sea
prior to the start of the mission. Logistic requirements may include planning for
on-site resupply of mixed gases and other supplies and for relief of diving teams.
12-3.1

Gas Mixtures. Four gas mixtures are required to dive the surface-supplied mixed

gas tables over their full range:

n Bottom Mixture - The bottom mixture may vary from 90% helium 10% oxygen
to 60% helium 40% oxygen depending on the diver’s depth. The allowable
range of bottom mixtures for each depth is shown in Table 12‑4.
n 50% Helium 50% Oxygen - This mixture is used from 90 fsw to 40 fsw during
decompression. Oxygen concentration in the mixture may range from 49 to 51
percent.
n 100% Oxygen - Oxygen is used at the 30-fsw and 20-fsw water stops during
inwater decompression and at 50, 40 and 30 fsw in the chamber during surface
decompression.
n Air - Air is used as an emergency backup gas throughout the dive and to provide
air breaks during oxygen breathing.
Instruments used to measure oxygen content in helium-oxygen mixtures shall be
accurate to 0.5 percent.
12-3.2

Flyaway Dive System (FADS) III Mixed Gas System (FMGS). The FADS III Mixed
Gas System (FMGS) is a portable, self contained, surface supplied diver life
support system designed to support mixed gas dive missions to 300 fsw (Figure
12-2 and Figure 12-3). The FMGS consists of five gas rack assemblies:

n One (1) Air Supply Rack Assembly (ASRA)
n One (1) Oxygen Supply Rack Assembly (OSRA)
n Three (3) Helium-Oxygen Supply Rack Assemblies (HOSRA)
Compressed air is provided by a 5000 psi air compressor assembly, which includes
an air purification system. The FMGS also includes a mixed gas control console
assembly (MGCCA) and two gas booster pump assemblies to charge the OSRA
and HOSRA. Set-up and operating procedures for the FMGS are found in the
Operating and Maintenance Technical Manual for Fly Away Dive System (FADS)
III Mixed Gas System, S9592-B2-OMI-010.

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U.S. Navy Diving Manual — Volume 3

Figure 12-1. FADS III Mixed Gas System (FMGS).

Figure 12-2. FMGS Control Console Assembly.

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12-5

12-4

SURFACE-SUPPLIED HELIUM-OXYGEN DESCENT AND ASCENT PROCEDURES

The Surface-Supplied Helium-Oxygen Decompression Table (Table 12‑4) is used
to decompress divers from surface-supplied helium-oxygen dives. The table is in
a depth time format similar to the U.S. Navy Air Decompression Table and is used
in a similar fashion.

Figure 12-3. Dive Team Brief for Divers.
12-4.1

12-4.2

12-6

Selecting the Bottom Mix. The Surface-Supplied Helium-Oxygen Decompression
Table (Table 12-4) speci­fies maximum and minimum concentrations of oxygen
allowable in the helium-oxygen mixture at depth. The maximum oxygen
concentration is set so the diver never exceeds an oxygen partial pressure of 1.3
ata while on the bottom. The minimum oxygen percentage allowed in the mixture
is 14 percent for depths to 200 fsw and 10 percent for depths in excess of 200
fsw. Diving with a mixture near maximum oxygen percentage is encouraged as it
offers a decompres­sion advantage to the diver. For operational planning, the range
of possible depths should be established and a mixture selected that will meet the
maximum/minimum specification across the depth range.
Selecting the Decompression Schedule. To select a proper decompression table
and schedule, measure the deepest depth reached by the diver and enter the table
at the exact or next greater depth. When using a pneumofathometer to measure
depth, correct the observed depth reading as shown in Table 12-2. Ensure the
pneumofathometer is located at mid-chest level.

U.S. Navy Diving Manual — Volume 3

Table 12‑2. Pneumofathometer Correction Factors.
Pneumofathometer
Depth Reading

Correction Factor

0-100 fsw

+1 fsw

101-200 fsw

+2 fsw

201-300 fsw

+4 fsw

301-400 fsw

+7 fsw

Example: The diver’s pneumofathometer reads 250 fsw. In the depth range of
201-300 fsw, the pneumofathometer underestimates the diver’s depth by 4 fsw. To
determine a diver’s depth, add 4 fsw to the pneumofathometer reading giving the
diver’s depth as 254 fsw.

Bottom time is measured as the time from leaving the surface to leaving the bottom,
rounded up to the next whole minute, except as noted in paragraph 12‑4.5. Enter
the table at the exact or next greater bottom time.
12-4.3

Travel Rates and Stop Times. The descent rate is not critical, but in general should

not exceed 75 fsw/min. The ascent rate from the bottom to the first decompression
stop, between decompression stops, and from the last decompression stop to the
surface is 30 fsw/min. Minor variations in the rate of ascent between 20 and 40
fsw/min are acceptable. For surface decompression, the ascent rate from the 40
fsw water stop to the surface is 40 fsw/min.
The time at the first decompression stop begins when the diver arrives at the stop
and ends when he leaves the stop. For all subsequent stops, the stop time begins
when the diver leaves the previous stop and ends when he leaves the stop. In other
words, ascent time between stops is included in the subsequent stop time. The
single exception is the first oxygen stop at 30 fsw. The 30-fsw oxygen stop begins
when the divers are confirmed to be on oxygen at 30 fsw and ends when the divers
leave 30 fsw. The ascent time from the 30- to the 20-fsw oxygen stop is included in
the 20-fsw oxygen stop time.

12-4.4

Decompression Breathing Gases. Decompress on bottom mixture to 90 fsw, then

shift the diver to a 50% helium 50% oxygen mixture. Upon arrival at the 30 fsw
stop, shift the diver to 100% oxygen.

For all dives, surface decompression may be used after completing the 40 fsw
water stop as described in paragraph 12‑4.11. During surface decompression, the
diver surfaces while breathing 50% helium 50% oxygen.
12-4.5

Special Procedures for Descent with Less than 16 Percent Oxygen. To prevent

hypoxia, a special descent procedure is required when the bottom mixture contains
less than 16% oxygen:

1. Place the diver on air on the surface.

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12-7

2. Make the appropriate predive checks.
3. Have the diver descend to 20 fsw.
4. At 20 fsw, shift the diver to the bottom mix and ventilate the diver for 20

seconds.

5. Confirm the diver is on bottom mix, then perform a final leak check. The diver

is allowed 5 minutes to descend to 20 fsw, shift to the bottom mixture and per­
form equipment checks.

6. Have the diver begin descent.
7. Start bottom time.

n If the diver spends 5 minutes or less performing above procedures,
bottom time starts when the diver leaves 20 fsw.
n If the diver spends more than 5 minutes performing above procedures,
bottom time starts at the 5 minute mark.
8. If it is necessary to bring the diver back to the surface from 20 fsw to correct a

problem:

n Shift the diver from the bottom mixture back to air.
n Ventilate the diver.
n Confirm the diver is on air.
n Have the diver begin ascent.
n When the diver reenters the water, the 5 minute grace period begins
again. No adjustment of bottom time is required for the previous
exposure at 20 fsw.
12-4.6

Aborting Dive During Descent. Inability to equalize the ears or sinuses may force

the dive to be aborted during descent.

1. If it is necessary to bring the diver back to the surface from depths of 100 fsw

and shallower:

n Ensure the diver is in a no-decompression status.
n If the bottom mixture is 16% oxygen or greater, ascend directly to the
sur­face at 30 fsw/min.
n If the bottom mixture is less than 16% oxygen, ascend to 20 fsw at
30 fsw/min.
n Shift the diver from the bottom mixture back to air.
n Ventilate the diver.
n Confirm the diver is on air.
n Complete ascent to the surface on air.
n If desired, another dive may be performed following a dive aborted 100

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U.S. Navy Diving Manual — Volume 3

fsw and shallower. Add the bottom time of all the dives to the bottom
time of the new dive and use the deepest depth when calculating a table
and schedule for the new dive.
2. If it is necessary to abort a dive deeper than 100 fsw:

n Follow the normal decompression schedule to the surface.
n Repetitive diving is not allowed following a dive aborted deeper than
100 fsw.
12-4.7

Procedures for Shifting to 50 Percent Helium/50 Percent Oxygen at 90 fsw. All
dives except no-decompression dives require a shift from bottom mixture to 50%
helium 50% oxygen at 90 fsw during decompression. Follow these steps:
1. Shift the console to 50% helium 50% oxygen when the diver reaches 90 fsw.
2. If there is a decompression stop at 90 fsw, ventilate each diver for 20 seconds

at 90 fsw.

3. Confirm the divers are on 50% helium 50% oxygen.
4. If there is no decompression stop at 90 fsw, delay ventilation until arrival at the

next shallower stop.

Gas shift time is included in the stop time.
12-4.8

Procedures for Shifting to 100 Percent Oxygen at 30 fsw. All in-water
decompression dives require a shift to 100 percent oxygen at the 30-fsw stop.
Upon arrival at the stop, ventilate each diver with oxygen following these steps:
1. Shift the console to 100% oxygen when the diver reaches 30 fsw.
2. Ventilate each diver for 20 seconds.
3. Verify the diver’s voice change.

Time at the 30-fsw stop begins when the divers are confirmed to be on oxygen.
12-4.9

Air Breaks at 30 and 20 fsw. At the 30-fsw and 20-fsw water stops, the diver
breathes oxygen for 30-minute periods separated by 5-minute air breaks. The
air breaks do not count toward required decompression time. When an air break
is required, shift the console to air for 5 minutes then back to 100% oxygen.
Ventilation of the divers is not required. For purposes of timing air breaks, begin
clocking oxygen time when all divers are confirmed on oxygen. If the total oxygen
stop time is 35 minutes or less, an air break is not required at 30 minutes. If the
final oxygen period is 35 minutes or less, a final air break at the 30-minute mark is
not required. In either case, surface the diver on 100% oxygen upon completion of
the oxygen time.
Example

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12-9

1. Divers are decompressing in the water on a 220 fsw for 20 minute decompression

schedule. The schedule calls for 23 minutes on oxygen at 30 fsw and 41 minutes
on oxygen at 20 fsw.

2. Divers start their 23 minute 30 fsw stop time when confirmed to be on oxygen

at 30 fsw.

3. After 23 minute on oxygen at 30 fsw, divers travel to 20 fsw to complete their

41 minute 20 fsw stop. The 20 second travel time from 30 to 20 fsw on oxygen
is included in the 41 minute stop time.

4. Seven minutes from the time the divers left their 30 fsw stop, the console is

shifted to air. This is due to the divers having completed a total of 30 minutes
on oxygen. No ventilation of the divers is required.

5. After five minutes on air, the console is shifted back to oxygen. No

ventilation is required. The five-minute period is considered dead time from
the decompression standpoint. A total of 34 minutes on oxygen remain to be
completed at 20 fsw.

6. Since the remaining oxygen time is less than 35 minutes, the divers breathe

oxygen for the last 34 minutes prior to ascent to the surface without taking an
additional air break. Divers remain on oxygen for ascent to the surface.

12-4.10

12-4.11

WARNING

Ascent from the 20-fsw Water Stop. For normal in-water decompression, the diver
surfaces from 20 fsw on oxygen. Ascent rate is 30 fsw/min.
Surface Decompression on Oxygen (SurDO2). Surface decompression on oxygen
is preferred over in-water decompression on oxygen for routine operations.
SurDO2 procedures improve the diver’s comfort and safety. A diver is eligible for
surface decompression when he has completed the 40-fsw water stop. To initiate
surface decompression:

The interval from leaving 40-fsw in the water to arriving at 50-fsw in the
chamber cannot exceed 5 minutes without incurring a penalty. (See
paragraph 12-5.14)
1. Bring the diver to the surface at 40 fsw/min and undress him.
2. Place the diver in the recompression chamber. Use of an inside tender when

two divers undergo surface decompression is at the discretion of the Dive
Supervisor. If an inside tender is not used, both divers will carefully monitor
each other in addition to being closely observed by topside personnel.

3. Compress the diver on air to 50 fsw at a maximum compression rate of 100

fsw/min. The surface interval is the elapsed time from the time the diver leaves
the 40-fsw water stop to the time the diver arrives at 50 fsw in the chamber. A
normal surface interval should not exceed 5 minutes.

4. Upon arrival at 50 fsw, place the diver on 100 percent oxygen by mask. The

mask will be strapped on both divers to ensure a good oxygen seal.

5. In the chamber, have the divers breathe oxygen for 30-minute periods separated

by 5-minute air breaks. The number of oxygen periods required is indicated

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U.S. Navy Diving Manual — Volume 3

in Table 12-3. The first period consists of 15 minutes on oxygen at 50 fsw
followed by 15 minutes on oxygen at 40 fsw. Periods 2, 3, and 4 are spent at 40
fsw. Periods 5, 6, 7 and 8 are spent at 30 fsw. Ascent from 50 to 40 and from
40 to 30 fsw is at 30 fsw/min. Ascent time is included in the oxygen/air time.
Ascent from 40 to 30 fsw, if required, should take place during the air break.
6. When the last oxygen breathing period has been completed, return the diver to

breathing chamber air.

7. Ascend to the surface at a rate of 30 fsw/min.

The diving supervisor can initiate surface decompression at any point during inwater oxygen decompression at 30 or 20 fsw, if desired. Surface decompression
may become desirable if sea conditions are deteriorating, the diver feels ill, or some
other contingency arises. Once in the chamber, the diver should receive the full
number of chamber oxygen periods prescribed by the tables. Unlike in air diving,
no credit is allowed for time already spent on oxygen in the water.
12-4.12

Variation in Rate of Ascent. The rate of ascent to the first stop and between

subsequent stops is 30 fsw/minute. Minor variations in the rate of travel between
20 and 40 fsw/minute are acceptable.

12‑4.12.1

Early Arrival at the First Stop. If the divers arrive early at the first stop:
1. Begin timing the first stop when the required travel time has been completed.
2. If the first stop requires a gas shift, initiate the gas shift and ventilation upon

arrival at the stop, but begin the stop time only when the required travel time
has been completed.

12‑4.12.2

Delays in Arriving at the First Stop.
1. Delay less than 1 minute. Delays in arrival at the first stop of less than 1 minute

may be ignored.

2. Delay greater than 1 minute. Round up the delay time to the next whole minute

and add it to the bottom time. Recompute the decompression schedule. If no
change in schedule is required, continue on the planned decompression. If a
change in schedule is required and the new schedule calls for a decompression
stop deeper than the diver’s current depth, perform any missed deeper stops at
the diver’s current depth. Do not go deeper.

Example: If the delay time to arrival at the first stop is 3 minutes and 25 seconds,

round up to the next whole minute and add 4 minutes to the bottom time. Recheck the
decom­pression table to see if the decompression stop depths or times have changed.
12‑4.12.3

Delays in Leaving a Stop or Arrival at the Next Stop.

n Delays Deeper than 90 fsw.
1. Delays less than 1 minute may be ignored.

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12-11

2. Greater than 1 minute. Add the delay to the bottom time and recalculate

the required decompression. If a new schedule is required, pick up the new
schedule at the present stop or subsequent stop if the delay occurs between
stops. Ignore any missed stops or time deeper than the depth at which the
delay occurred. If a delay occurs between stops, restart subsequent stop
time at completion of the delay.

n Delays 90 fsw and shallower:
1. Delays less than 1 minute may be ignored.
2. Delays greater than 1 minute require no special action except as described

below under special considerations when decompressing with high oxygen
partial pressure. Resume the normal decompression schedule at the comple­
tion of the delay. If a delay occurs between stops, restart subsequent stop
time at completion of the delay.

n Special considerations when decompressing with high oxygen partial pressure:
1. Delays greater than 5 minutes between 90 and 70 fsw. Shift the diver to air

to avoid the risk of CNS oxygen toxicity. At the completion of the delay,
return the diver to 50% helium 50% oxygen. Add the time on air to the bot­
tom time and recalculate the required decompression. If a new schedule is
required, pick up the new schedule at the present stop or subsequent stop
if delay occurs between stops. Ignore any missed stops or time deeper than
the depth at which the delay occurred.

2. Delays leaving the 30-fsw stop. Delays greater than 1 minute leaving the

30-fsw stop shall be subtracted from the 20-fsw stop time.

12‑4.12.4

12-5

Delays in Travel from 40 fsw to the Surface for Surface Decompression.

Disregard any delays in travel from 40 fsw to the surface during surface decompression unless the diver exceeds the 5-minute surface interval. If the diver exceeds the 5-minute surface interval, follow the guidance in paragraph 12-5.14.

SURFACE-SUPPLIED HELIUM-OXYGEN EMERGENCY PROCEDURES

In surface-supplied mixed gas diving, specific procedures are used in emergency
situations. The following paragraphs detail these procedures. Other medical/
physiological factors that surface-supplied mixed gas divers need to consider are
covered in detail in Chapter 3. The U.S. Navy Treatment Tables are presented in
Chapter 17.
12-5.1

Bottom Time in Excess of the Table.

In the rare instance of diver entrapment or umbilical fouling, bottom times may
exceed 120 minutes, the longest value shown in the table. When it is foreseen that
bottom time will exceed 120 minutes, immediately contact the Navy Experimental
Diving Unit for advice on which decompression procedure to follow. If advice
cannot be obtained in time:
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U.S. Navy Diving Manual — Volume 3

1. Decompress the diver using the 120-minute schedule for the deepest depth

attained.

2. Shift to 100 percent oxygen at 40 fsw.
3. Surface the diver after completing 30 minutes on oxygen at 40 fsw. Oxygen

time at 40 fsw starts when divers are confirmed on oxygen.

4. Compress the diver to 60 fsw in the chamber as fast as possible not to exceed

100 fsw/min.

5. Treat the diver on an extended Treatment Table 6. Extend Treatment Table 6 for

two oxygen breathing periods at 60 fsw (20 minutes on oxygen, then 5 minutes
on air, then 20 minutes on oxygen) and two oxygen breathing periods at 30 fsw
(60 minutes on oxygen, then 15 minutes on air, then 60 minutes on oxygen).

12-5.2

Loss of Helium-Oxygen Supply on the Bottom. Follow this procedure if the

umbilical helium-oxygen supply is lost on the bottom:

1. Shift the diver to the emergency gas system (EGS).
2. Abort the dive.
3. Remain on the EGS until arrival at 90 fsw.
4. At 90 fsw, shift the diver to 50% helium 50% oxygen and complete the decom­

pression as planned.

5. If the EGS becomes exhausted before 90 fsw is reached, shift the diver to air,

complete decompression to 90 fsw, shift the diver to 50% helium 50% oxygen,
and continue the decompression as planned.

12-5.3

Loss of 50 Percent Oxygen Supply During In-Water Decompression. If the diver

cannot be shifted to 50% helium 50% oxygen at 90 fsw or the 50% helium 50%
oxygen supply is lost during decompression:

1. Shift the diver to air and continue the decompression as planned while trying to

correct the problem.

2. Shift the diver to 50% helium 50% oxygen once the problem is corrected. Time

spent on air counts toward decompression.

3. If the problem cannot be corrected:

n Continue the planned decompression on air.
n Shift the diver from air to oxygen upon arrival at the 50-fsw stop.
n Breathe oxygen at 50 and 40 fsw for the decompression times indicated
in Table 12‑4, but not to exceed 16 minutes at 50 fsw. Oxygen time at
50 fsw starts when divers are confirmed on oxygen. If the 50-fsw stop
exceeds 16 minutes, travel divers to 40 fsw and add remaining 50-fsw
stop time to the 40-fsw stop time on oxygen.

CHAPTER 12 — Surface-Supplied Mixed Gas Diving

12-13

n Surface decompress per paragraph 12‑4.11 following completion of the
40-fsw stop.
12-5.4

Loss of Oxygen Supply During In-Water Decompression. If the diver cannot be

shifted to oxygen at 30 fsw or the oxygen supply is lost during the 30- or 20-fsw
water stops:
1. Switch back to 50% helium 50% oxygen. If a switch to 50% helium 50% oxy­

gen is not possible, switch the diver to air.

2. If the problem can be quickly remedied, reventilate the diver with oxygen and

resume the schedule at the point of interruption. Consider any time on heliumoxygen or air as dead time.

3. If the problem cannot be remedied, initiate surface decompression. Ignore any

time already spent on oxygen at 30 or 20 fsw. The five minute surface interval
requirement for surface decompression begins upon leaving the 30- or 20-fsw
stop.

4. If the problem cannot be remedied and surface decompression is not feasible,

complete the decompression on 50% helium 50% oxygen or air. For 50%
helium 50% oxygen, double the remaining oxygen time at each water stop. For
air, triple the remaining oxygen time.

Example: A diver loses oxygen 15 minutes into the 30-fsw water stop and is switched

back to the 50% helium 50% oxygen decompression mixture. The problem cannot
be corrected. The divers original schedule called for 32 minutes of oxygen at 30
fsw and 58 minutes of oxygen at 20 fsw.

Seventeen minutes of oxygen time (32 - 15) remain at 30 fsw. Fifty-eight minutes
remain at 20 fsw. The diver should spend an additional 34 minutes (17 x 2) at 30
fsw on the 50/50 mixture, followed by 116 minutes (58 x 2) at 20 fsw. Surface the
diver upon completion of the 20-fsw stop.
Example: A diver loses oxygen 10 minutes into the 30-fsw water stop and is

switched to air. The problem cannot be corrected. The diver’s original schedule
called for 28 minutes of oxygen at 30 fsw and 50 minutes of oxygen at 20 fsw.
Eighteen minutes of oxygen time (28 - 10) remain at 30 fsw. Fifty minutes remain
at 20 fsw. The diver should spend an additional 54 minutes (18 x 3) at 30 fsw
on air followed by 150 minutes (50 x 3) on air at 20 fsw. Surface the diver upon
completion of the 20-fsw stop.

12-5.5

Loss of Oxygen Supply in the Chamber During Surface Decompression. If the

oxygen supply in the chamber is lost during surface decompression, have the diver
breathe chamber air.
n Temporary Loss. Return the diver to oxygen breathing. Consider any time on
air as dead time.

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U.S. Navy Diving Manual — Volume 3

n Permanent Loss. Multiply the remaining oxygen time by three to obtain the
equivalent chamber decompression time on air. If 50% helium 50% oxygen is
available, multiply the remaining oxygen time by two to obtain the equivalent
chamber decompression time on 50/50. If the loss occurred at 50 or 40 fsw,
allocate 10% of the equivalent air or helium-oxygen time to the 40-fsw stop,
20% to the 30-fsw stop, and 70% to the 20-fsw stop. If the diver is at 50 fsw,
ascend to 40 fsw to begin the stop time. If the loss occurred at 30 fsw, allocate
30% of the equivalent air or helium-oxygen time to the 30-fsw stop and 70%
to the 20-fsw stop. Round the stop times to the nearest whole minute. Surface
upon completion of the 20-fsw stop.
Example: The oxygen supply to the chamber is lost 10 minutes into the first

30-minute period on oxygen. Helium-oxygen is not available. The original surface
decom­pression schedule called for three 30-min oxygen breathing periods (total of
90 minutes of oxygen). The diver is at 50 fsw.
The remaining oxygen time is 80 minutes (90-10). The equivalent chamber
decompression time on air is 240 minutes (3 x 80). The 240 minutes of air stop
time should be allocated as follows: Twenty-four minutes at 40 fsw (240 x 0.1), 48
minutes at 30 fsw (240 x 0.2), and 168 minutes at 20 fsw (240 x 0.7). As addressed
above, the diver should ascend from 50 to 40 fsw and begin the 24 minute stop time
at 40 fsw.
12-5.6

Decompression Gas Supply Contamination. If the decompression gas supply be-

comes contaminated with the bottom mixture, 50/50 mix, air, or oxygen:

1. Find the source of the contamination and correct the problem. Probable sources

include:

n An improper valve line-up on the console. This can be verified by
checking oxygen percentage on console oxygen analyzer.
n Accidental opening of the emergency gas supply (EGS) valve.
2. When the problem is corrected:

n Ventilate each diver for 20 seconds and confirm divers are on decompres­
sion gas.
n Continue decompression as planned. Do not lengthen stop times to com­
pensate for the time spent correcting the problem.
12-5.7

CNS Oxygen Toxicity Symptoms (Nonconvulsive) at the 90-60 fsw Water Stops.

CNS oxygen toxicity symptoms are unlikely but possible while the diver is
breathing 50% helium 50% oxygen in the water at depths 60 fsw and deeper. If
symptoms of oxygen toxicity do appear, take the following actions:
1. Bring the divers up 10 feet and shift to air to reduce the partial pressure of oxy-

gen. Shift the console as the divers are traveling.

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12-15

2. Ventilate both divers upon arrival at the shallower stop. Ventilate the stricken

diver first.

3. Remain at the shallower stop until the missed time at the previous stop is

made up.

4. Resume the planned decompression breathing air.
5. Upon arrival at the next shallower stop, return the divers to the 50% helium

50% oxygen mixture. Ignore any missed time on the 50/50 mixture. A recur­
rence of symptoms is highly unlikely because of the reduced oxygen partial
pressure at the shallower depth.

Example: Red Diver has an oxygen toxicity symptom 5 minutes into his scheduled

9-minute 80-fsw stop. The stage with both divers travels to 70 fsw and the console
is shifted to air. Upon arrival at 70 fsw, Red diver is ventilated for 20 seconds
followed by Green diver. The divers remain at 70 fsw for the remaining 4 minutes
left from their 80-fsw stop and then start their 10 minute scheduled 70-fsw stop
time at the completion of the 4 minutes. Upon reaching 60 fsw, the console is
shifted back to their 50/50 mixture and both divers are ventilated. The normal
decompression schedule is resumed at 60 fsw.
12-5.8

Oxygen Convulsion at the 90-60 fsw Water Stop. If symptoms of oxygen toxicity

progress to an oxygen convulsion at 90-60 fsw despite the measures taken above,
a serious emergency has developed. Only general management guidelines can be
presented here. Topside supervisory personnel must take whatever action they
deem necessary to bring the casualty under control.
Follow these procedures when the diver is convulsing at the 90-60 fsw water stops:

1. Shift both divers to air if this action has not already been taken.
2. Have the unaffected diver ventilate himself and then ventilate the stricken

diver.

3. If only one diver is in the water, launch the standby diver immediately and have

him ventilate the stricken diver.

4. Hold the divers at depth until the tonic-clonic phase of the convulsion has sub­

sided. The tonic-clonic phase of a convulsion generally lasts 1 to 2 minutes.

5. At the end of the tonic-clonic phase, have the dive partner or standby diver

ascertain whether the diver is breathing. The presence or absence of breath
sounds will also be audible over the intercom.

6. If the diver appears not to be breathing, have the dive partner or standby diver

attempt to reposition the head to open the airway. Airway obstruction will be
the most common reason why an unconscious diver fails to breathe.

7. If the affected diver is breathing, have the dive partner or standby diver tend

the stricken diver and decompress both divers on air following the original
schedule. Shift the divers to 50% helium 50% oxygen upon arrival at 50 fsw.
Surface decompress upon completion of the 40-fsw water stop.

12-16

U.S. Navy Diving Manual — Volume 3

8. If it is not possible to verify that the affected diver is breathing, leave the unaf­

fected diver at the stop to complete decompression, and surface the affected
diver and the standby diver at 30 fsw/min. Shift the unaffected diver back to
his 50/50 mixture for completion of decompression. The standby diver should
maintain an open airway on the stricken diver during ascent. On the surface the
affected diver should receive any necessary airway support and be imme­diately
recompressed and treated for arterial gas embolism and missed decompression
in accordance with Figure17-1.

12-5.9

CNS Toxicity Symptoms (Nonconvulsive) at 50- and 40-fsw Water Stops. It is

very unlikely that a diver will develop symptoms of CNS oxygen toxicity while
breathing 50% helium 50% oxygen at the 50- and 40-fsw water stops. Symp­toms
are much more likely if the diver is breathing 100% oxygen in accordance with
paragraph 12-5.3. If the diver does experience symptoms of CNS oxygen toxicity
at 50 or 40 fsw while breathing either 50% helium 50% oxygen or 100% oxygen,
take the following actions:
1. Bring the divers up 10 feet and shift to air to reduce the partial pressure of oxy­

gen. Shift the console as the divers are traveling to the shallower stop.

2. Ventilate both divers upon arrival at the shallower stop. Ventilate the stricken

diver first.

3. Remain on air at the shallower depth for double the missed time from 50-

and 40-fsw water stops, then surface decompress the diver in accordance with
paragraph 12-4.11. If the diver was on 100% oxygen in accordance with para­
graph 12-5.3, triple the missed time from the 50- and 40-fsw water stops, then
surface decompress.
Example: A diver on 50% helium 50% oxygen experiences an oxygen symp­

tom five minutes into his 10 min stop at 50 fsw. He immediately ascends to
40 fsw and begins breathing air. The decompression schedule calls for a 10
min stop at 40 fsw. The diver missed 5 min of helium-oxygen at 50 fsw and
will miss 10 min more at 40 fsw by virtue of the fact that he is on air. The total
missed helium-oxygen time is 15 min. The diver should remain at 40 fsw for
30 min, then surface decompress.
Example: A diver on 100% oxygen experiences an oxygen symptom five min­

utes into his 10 min stop at 40 fsw. He immediately ascends to 30 fsw and
begins breathing air. The missed oxygen time at 40 fsw is 5 min. The diver
should remain on air at 30 fsw for 15 min, then surface decompress.
4. If surface decompression is not feasible, continue decompression in the water

on either air or oxygen depending on the diver’s condition:

n To continue on oxygen, ascend to 30 fsw (or remain at 30 fsw if already
there). Take a 10 min period on air (Time on air does not count toward
decompression). Then shift the diver to oxygen and complete decompression
in the water according to the schedule.

CHAPTER 12 — Surface-Supplied Mixed Gas Diving

12-17

n To continue on air, ascend to 30 fsw (or remain at 30 fsw if already there).
Compute the remaining 30- and 20-fsw air stop times by tripling the oxygen
time given in the original schedule. Surface upon completion of the 20-fsw
stop.
n Alternatively, the diver may complete the 30-fsw stop on air by tripling the
oxygen stop time, then switch to oxygen upon arrival at 20 fsw. Remain at
20 fsw for the oxygen time indicated in the original schedule. Surface upon
completion of the 20-fsw stop.
12-5.10

Oxygen Convulsion at the 50-40 fsw Water Stop. If oxygen symptoms progress

to an oxygen convulsion despite the measures described above or if a convulsion
occurs suddenly without warning at 50 or 40 fsw, take the following actions:

1. Shift both divers to air if this action has not already been taken. Have the unaf­

fected diver ventilate himself then ventilate the stricken diver.

2. Follow the guidance given in paragraph 12-5.8 for stabilizing the stricken diver

and determining whether he is breathing. If the diver is breathing, hold him at
his current depth until he is stable, then take one of the following actions:
n If the diver missed helium-oxygen or oxygen decompression time at 50 fsw,
hold the diver at depth until the total elapsed time on air is at least double
the missed time on helium-oxygen, then surface decompress following the
steps in paragraph 12-4.11. If the diver was on 100% oxygen in accordance
with paragraph 12-5.3, remain at depth until the total elapsed time on air
is at least triple the missed time on oxygen, then surface decompress. In
either case, add the 40-fsw water stop time to the 50-fsw chamber oxygen
stop time.
n If the diver did not miss any helium-oxygen or oxygen decompression time
at 50 fsw, surface decompress following the steps in paragraph 12-4.11.
Add any missed oxygen or helium-oxygen time at 40 fsw to the 50-fsw
chamber oxygen stop time.

3. If surface decompression is not feasible, complete decompression in the water

on air. Compute the remaining stop times on air by doubling the remaining
helium-oxygen time, or tripling the remaining oxygen time at each stop.

4. If the diver is not breathing, surface the diver at 30 fsw/min while maintaining

an open airway. Treat the diver for arterial gas embolism (Figure 17-1).

12-5.11

CNS Oxygen Toxicity Symptoms (Nonconvulsive) at 30- and 20-fsw Water Stops.

If the diver develops symptoms of CNS toxicity at the 30- or 20-fsw water stops,
take the following action:
1. If a recompression chamber is available on the dive station, initiate surface

decompression. Shift the console to air during travel to the surface. Once in
the chamber, take the full number of chamber oxygen periods prescribed by
the tables. Unlike in air diving, no credit is allowed for time already spent on
oxygen in the water.

12-18

U.S. Navy Diving Manual — Volume 3

2. If a recompression chamber is not available on the dive station and the event

occurs at 30 fsw, bring the divers up 10 fsw and shift to air to reduce the partial
pressure of oxygen. Shift the console as the divers are traveling to 20 fsw.
Ventilate both divers with air upon arrival at 20 fsw. Ventilate the affected diver
first. Complete the decompression on air in the water at 20 fsw. Compute the
required air time at 20 fsw by tripling the sum of the missed oxygen time at 30
and 20 fsw.

3. If a recompression chamber is not available on the dive station and the event

occurs at 20 fsw, shift the console to air, ventilate both divers, affected diver
first, and complete the decompression in the water at 20 fsw on air. Compute
the required air time at 20 fsw by tripling the missed oxygen time at 20 fsw.

12-5.12

Oxygen Convulsion at the 30- and 20-fsw Water Stop. If symptoms progress
to an oxygen convulsion despite the above measures, a serious emergency has
developed and the following actions must be taken.
1. Shift both divers to air and follow the guidance given in paragraph 12-5.8 for

stabilizing the diver and determining whether he is breathing.

2. If the diver is breathing, hold him at depth until he is stable, then surface

decompress.

3. If surface decompression is not feasible, ventilate both divers with air and

complete decompression in the water on air. Compute the remaining stop times
on air by tripling the remaining oxygen time at each stop. See paragraph 12-5.4
for example.

4. If the diver is not breathing, surface the diver at 30 fsw/min while maintaining

an open airway and treat the diver for arterial gas embolism (Figure 18-1).

12-5.13

Oxygen Toxicity Symptoms in the Chamber. At the first sign of CNS oxygen

toxicity, the patient should be removed from oxygen and allowed to breathe
chamber air. Fifteen minutes after all symptoms have completely subsided, resume
oxygen breathing at the point of interruption. If symptoms of CNS oxygen toxicity
develop again or if the first symptom is a convulsion, take the following action:

1. Remove the mask.
2. After all symptoms have completely subsided, decompress 10 feet at a rate of

1 fsw/min. For a convulsion, begin travel when the patient is fully relaxed and
breathing normally.

3. Resume oxygen breathing at the shallower depth at the point of interruption.
4. If another oxygen symptom occurs, complete decompression on chamber air.

Follow the guidance given in paragraph 12‑5.5 for permanent loss of chamber
oxygen supply to compute the air decompression schedule.

12-5.14

Surface Interval Greater than 5 Minutes. If the time from leaving 40 fsw in the
water to the time of arrival at 50 fsw in the chamber during surface decompression
exceeds 5 minutes, take the following action:

CHAPTER 12 — Surface-Supplied Mixed Gas Diving

12-19

1. If the surface interval is less than or equal to 7 minutes, add one-half oxygen

period to the total number of chamber periods required by increasing the time
on oxygen at 50 fsw from 15 to 30 minutes. Ascend to 40 fsw during the
subsequent air break. The 15-min penalty is considered a part of the normal
surface decompression procedure, not an emergency procedure.

2. If the surface interval is greater than 7 minutes, continue compression to a depth

of 60 fsw. Treat the divers on Treatment Table 5 if the original schedule required
2 or fewer oxygen periods in the chamber. Treat the divers on Treatment Table
6 if the original schedule required 3 or more oxygen periods in the chamber.

3. On rare occasions a diver may be unable to reach 50 fsw in the chamber due

to difficulty equalizing middle ear pressure. In this situation, an alternative
procedure for surface decompression on oxygen may be used:
n Begin oxygen breathing at the initially attained depth - presumed to be
less than 20 fsw.
n If surface decompression was initiated while the diver was decompressing
on oxygen in the water at 20 fsw, attempt to gradually compress the
diver to 20 fsw.
n If surface decompression was initiated from deeper than 20 fsw, attempt
to gradually compress the diver to 30 fsw.
n In either case, double the number of chamber oxygen periods indicated
in the table and take these periods at the deepest depth the diver is able
to attain. Oxygen time starts when the diver initially goes on oxygen.
n Interrupt oxygen breathing every 60 minutes with a 15-min air break.
The air break does not count toward the total oxygen time.
n Surface the diver at 30 fsw/min upon completion of the oxygen breathing
periods and carefully observe the diver for the onset of decompression
sickness.

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U.S. Navy Diving Manual — Volume 3

This “safe way out” procedure is not intended to be used in place of normal surface
decompression procedures. Divers that experienced ear difficulty on descent in the
water column may not be good candidates for surface decompression.
12-5.15

Asymptomatic Omitted Decompression. Certain emergencies may interrupt or

prevent required decompression. Unex­
pected surfacing, exhausted gas supply
and bodily injury are examples of such emergencies. Table 12-3 shows the initial
management steps to be taken when the diver has an uncontrolled ascent.
Table 12‑3. Management of Asymptomatic Omitted Decompression.
Deepest
Decompression
Stop Omitted

Decompression
Status

Surface
Interval
(Note 1)

ACTION

None

No-D

Any

Observe on surface for one hour

Less than 1 min

Return to depth of stop. Increase stop
time by 1 min. Resume decompression
according to original schedule

1–7 min

Use Surface Decompression Procedure
(Note 2)

20 or 30 fsw

Stops Required
Greater than
7 min

40 or 50 fsw

Deeper than 50 fsw

Treatment Table 5 if 2 or fewer SurDO2
periods
Treatment Table 6 if 3 or more SurDO2
periods

Stops Required

Any

Treatment Table 6

Stops Required:
Less than 60 min
missed

Any

Treatment Table 6A

Stops Required:
More than 60 min
missed

Compress to depth of dive not to
exceed 225 fsw. Use Treatment Table 8
Any

For saturation systems: Compress to
depth of dive. Saturate two hours. Use
saturation decompression without an
initial upward excursion

Notes:
1. Surface interval is the time from leaving the stop to arriving at depth in the chamber.
2. Using a recompression chamber is strongly preferred over in-water recompression for returning a
diver to pressure. Compress to depth as fast as possible not to exceed 100 fsw/min.
3. For surface intervals greater than 5 minutes but less than or equal to 7 minutes, increase the oxygen
time at 50 fsw from 15 to 30 minutes.

12‑5.15.1

Omitted Decompression Stop Deeper Than 50 fsw. An omitted decompression

stop deeper than 50 fsw when more than 60 minutes of decompression are missed
is an extreme emergency. The diver shall be returned as rapidly as possible to
the full depth of the dive or the deepest depth of which the chamber is capable,
whichever is shallower.

For nonsaturation systems, the diver shall be rapidly
compressed on air to the depth of the dive or to 225 feet, whichever is shallower.

12‑5.15.1.1 For Nonsaturation Systems.

CHAPTER 12 — Surface-Supplied Mixed Gas Diving

12-21

For compressions deeper than 165 feet, remain at depth for 30 minutes. For
compressions to 165 feet and shallower, remain at depth for a minimum of two
hours. Decompress on USN Treatment Table 8. While deeper than 165 feet, a
helium-oxygen mixture with 16 percent to 21 percent oxygen, if available, may be
breathed by mask to reduce narcosis.
For saturation systems, the diver should be rapidly
compressed on air to 60 fsw, followed by compression on pure helium to the full
depth of the dive or deeper if symptom onset warrants. The diver shall breathe
84% helium/16% oxygen by mask during the compression (if possible) to avoid
the possibility of hypoxia as a result of gas pocketing in the chamber. Once at the
saturation depth, the length of time spent can be dictated by the circumstances
of the diver, but should not be less than 2 hours. During this 2 hours, treatment
gas should be administered to the diver as outlined in paragraph 13‑23.8.2. The
chamber oxygen partial pressure should be allowed to fall passively to 0.44-0.48
ata. Begin saturation decompres­sion without an upward excursion.

12‑5.15.1.2 For Saturation Systems.

12-5.16

Symptomatic Omitted Decompression. If the diver develops symptoms of

decompression sickness or gas embolism before recompression for omitted
decompression can be accomplished, immediate treatment using the appropriate
oxygen or air recompression table is essential. Guidance for table selection and
use is given in Chapter 17. If the depth of the deepest stop omitted was greater
than 50 fsw and more than 60 minutes of decom­pression have been missed, use
of Treatment Table 8 (Figure 17-9) or saturation treatment is indicated. See USN
Treatment Table 4 and Treatment Table 7 (Chapter 17) for guidance on oxygen
breathing.
In all cases of deep blowup, the services of a Diving Medical Officer shall be
sought at the earliest possible moment.

12-5.17

12‑5.17.1

12-22

Light Headed or Dizzy Diver on the Bottom. Dizziness is a common term used to

describe a number of feelings, including lightheadedness, unsteadiness, vertigo (a
sense of spinning), or the feeling that one might pass out. There are a number of
potential causes of dizziness in surface-supplied diving, including hypoxia, a gas
supply contaminated with toxic gases such as methylchloroform, and trauma to
the inner ear caused by difficult clearing of the ear. At the low levels of oxygen
percentage specified for surface-supplied diving, oxygen toxicity is an unlikely
cause unless the wrong gas has been supplied to the diver.

Initial Management. The first step to take is to have the diver stop work and
ventilate the rig while topside checks the oxygen content of the supply gas. These
actions should elimi­nate hypoxia and hypercapnia as a cause. If ventilation does
not improve symptoms, the cause may be a contaminated gas supply. Shift banks
to the standby helium-oxygen supply and continue ventilation. If the condition
clears, isolate the contaminated bank for future analysis and abort the dive on the
standby gas supply. If the entire gas supply is suspect, place the diver on the EGS
and abort the dive. Follow the guidance of paragraph 12‑4 for ascents.

U.S. Navy Diving Manual — Volume 3

12‑5.17.2

12-5.18

Vertigo. Vertigo due to inner ear problems will not respond to ventilation and

in fact may worsen. One form of vertigo, however, alternobaric vertigo, may be
so short lived that it will disappear during ventilation. Alternobaric vertigo will
usually occur just as the diver arrives on the bottom and often can be related to a
difficult clearing of the ear. It would be unusual for alternobaric vertigo to occur
after the diver has been on the bottom for more than a few minutes. Longer lasting
vertigo due to inner ear barotrauma will not respond to ventilation and will be
accompa­nied by an intense sensation of spinning and marked nausea. Also, it is
usually accompanied by a history of difficult clearing during the descent. These
character­istic symptoms may allow the diagnosis to be made. A wide variety of
ordinary medical conditions may also lead to dizziness. These conditions may
occur while the diver is on the bottom. If symptoms of dizziness are not cleared
by ventilation and/or shifting to alternate gas supplies, have the dive partner or
standby diver assist the diver(s) and abort the dive.
Unconscious Diver on the Bottom. An unconscious diver on the bottom constitutes a serious emergency. Only general guidance can be given here. Management
decisions must be made on site, taking into account all known factors. The advice
of a Diving Medical Officer shall be obtained at the earliest possible moment.

If the diver becomes unconscious on the bottom:
1. Make sure that the breathing medium is adequate and that the diver is breath-

ing. Verify manifold pressure and oxygen percentage.

2. Check the status of any other divers.
3. Have the dive partner or standby diver ventilate the afflicted diver to remove

any accumulated carbon dioxide in the helmet and ensure the correct oxygen
concentration.

4. If there is any reason to suspect gas contamination, shift to the standby helium-

oxygen supply and ventilate both divers, ventilating the non-affected diver first.

5. When ventilation is complete, have the dive partner or standby diver ascertain

whether the diver is breathing. The presence or absence of breath sounds will
be audible over the intercom.

6. If the diver appears not to be breathing, the dive partner/standby diver should

attempt to reposition the diver’s head to open the airway. Airway obstruction
will be the most common reason why an unconscious diver fails to breathe.

7. Check afflicted diver for signs of consciousness:

n If the diver has regained consciousness, allow a short period for stabilization and then abort the dive.
n If the diver remains unresponsive but is breathing, have the dive partner or
standby diver move the afflicted diver to the stage. This action need not be
rushed.
n If the diver appears not to be breathing, maintain an open airway while
moving the diver rapidly to the stage.

CHAPTER 12 — Surface-Supplied Mixed Gas Diving

12-23

8. Once the diver is on the stage, observe again briefly for the return of

consciousness.

n If consciousness returns, allow a period for stabilization, then begin
decompression.
n If consciousness does not return, bring the diver to the first decompression stop at a rate of 30 fsw/min (or to the surface if the diver is in a nodecompression status).
9. At the first decompression stop:

n If consciousness returns, decompress the diver on the standard decompression schedule using surface decompression.
n If the diver remains unconscious but is breathing, decompress on the stan­
dard decompression schedule using surface decompression.
n If the diver remains unconscious and breathing cannot be detected in spite
of repeated attempts to position the head and open the airway, an extreme
emergency exists. One must weigh the risk of catastrophic, even fatal,
decompression sickness if the diver is brought to the surface, versus the risk
of asphyxiation if the diver remains in the water. As a general rule, if there
is any doubt about the diver’s breathing status, assume he is breathing and
continue normal decompression in the water. If it is abso­lutely certain that the
diver is not breathing, leave the unaffected diver at his first decompression
stop to complete decompression and surface the affected diver at 30 fsw/
minute, deploying the standby diver as required. Recompress the diver
immediately and treat for omitted decompression according to Table 12‑3.
12-5.19

Decompression Sickness in the Water. Decompression sickness may develop in

the water during surface-supplied diving. This possibility is one of the principal
reasons for limiting dives to 300 fsw and allowing exceptional exposures only
under emergency circumstances. The symp­toms of decompression sickness may
be joint pain or more serious manifestations such as numbness, loss of muscular
function, or vertigo.
Management of decompression sickness in the water will be difficult under the
best of circumstances. Only general guidance can be presented here. Management
decisions must be made on site taking into account all known factors. The advice of
a Diving Medical Officer shall be obtained at the earliest possible moment.

12‑5.19.1

12-24

Decompression Sickness Deeper than 30 fsw. If symptoms of decompression

sickness occur deeper than 30 fsw, recompress the diver 10 fsw. The diver may
remain on 50% helium 50% oxygen during recom­pression from 90 to 100 fsw.
Remain at the deeper stop for 1.5 times the stop time called for in the decompression
table. If no stop time is indicated in the table, use the next shallower stop time
to make the calculation. If symptoms resolve or stabi­lize at an acceptable level,
decompress the diver to the 40-fsw water stop by multiplying each intervening
stop time by 1.5 or more as needed to control the symptoms. Shift to 50% helium

U.S. Navy Diving Manual — Volume 3

50% oxygen at 90 fsw if the diver is not already on this mixture. Shift to 100
percent oxygen at 40 fsw and complete a 30 minute stop, then surface decompress
and treat on Treatment Table 6. If during this scenario, symptoms worsen to the
point that it is no longer practical for the diver to remain in the water, surface the
diver and follow the guidelines for treatment of decompression sickness outlined
in Chapter 17.
12‑5.19.2

12-5.20

Decompression Sickness at 30 fsw and Shallower. If symptoms of decompression

sickness occur at 30 fsw or shallower, remain on oxygen and recompress the
diver 10 fsw. Remain at the deeper stop for 30 minutes. If symptoms resolve,
surface decompress the diver at the end of the 30 minute period and treat on
Treatment Table 6. If symptoms do not resolve, but stabilize at an acceptable level,
decompress the diver to the surface on oxygen by multiplying each intervening
stop time by 1.5 or more as needed to control symp­toms. Treat on Treatment
Table 6 upon reaching the surface. If during this scenario symptoms worsen to the
point that it is no longer practical for the diver to remain in the water, surface the
diver and follow guidelines for treatment of decompression sickness outlined in
Chapter 17.
Decompression Sickness During the Surface Interval. If symptoms of Type
I decompression sickness occur during travel from 40 fsw to the surface during
surface decompression or during the surface undress phase, compress the diver to
50 fsw following normal surface decompression procedures. Delay neurological
exam until the diver reaches the 50-fsw stop and is on oxygen. If Type I symptoms
resolve during the 15-minute 50-fsw stop, the surface interval was 5 minutes or
less, and no neurological signs are found, increase the oxygen time at 50 fsw from
15 to 30 minutes, then continue normal decompression for the schedule of the
dive. Ascend from 50 to 40 fsw during the subsequent air break.

If Type I symptoms do not resolve during the 15-minute 50-fsw stop or symptoms
resolve but the surface interval was greater than 5 minutes, compress the diver to
60 fsw on oxygen. Treat the diver on Treatment Table 5 if the original schedule
required 2 or fewer oxygen periods in the chamber. Treat the diver on Treatment
Table 6 if the original schedule required 3 or more oxygen periods in the chamber.
Treatment table time starts upon arrival at 60 fsw. Follow the guidelines for
treatment of decompression sickness given in Chapter 17.
If symptoms of Type II decompression sickness occur during travel from 40 fsw
to the surface, during the surface undress phase, or the neurological examination
at 50 fsw is abnormal, compress the diver to 60 fsw on oxygen. Treat the diver on
Treatment Table 6. Treatment table time starts upon arrival at 60 fsw. Follow the
guidelines for treatment of decompression sickness given in Chapter 17.
If DCS symptoms appear while the diver is undergoing decompression at 50, 40
or 30 fsw in the chamber, treat the symptoms as a recurrence in accordance with
Figure 17-3.

CHAPTER 12 — Surface-Supplied Mixed Gas Diving

12-25

12-6

CHARTING SURFACE SUPPLIED HELIUM OXYGEN DIVES

Chapter 5 provides information for maintaining a Command Diving Log and
personal diving log and for reporting individual dives to the Naval Safety Center.
In addition to these records, every Navy HeO2 dive shall be recorded on a diving
chart similar to Figure 12‑4. The diving chart is a convenient means of collecting
the dive data, which in turn will be transcribed in the dive log. It is also useful in
completing a mishap report for a diving related accident.
12-6.1

Charting an HeO2 Dive. Figure 12-4 is a blank HeO2 diving chart. Figure 12-5 is

an example of a Surface Decompression dive. Figure 12-6 is an example of an Inwater Decompression dive. Figure 12-7 is an example of a Surface Decompression
dive with a hold on descent and delay on ascent.
When logging times on an HeO2 diving chart, times will be recorded in a minute
and second format. Clock time, however, will be logged in hours and minutes. All
ascent times are rounded up to the next whole minute.

12-7

DIVING AT ALTITUDE

Surface-supplied helium-oxygen dives can be performed at altitude. The procedures
for measuring water depth, obtaining the Sea Level Equivalent Depth and correcting
in-water decompression stop depths are identical to the procedures for air diving
(see paragraph 9-13). The procedures for performing surface decompression are
also identical. The chamber stop depths during surface decompression are not
adjusted for the altitude. Table 12-4 gives the maximum and minimum percentage
of oxygen allowed in the bottom mixture at each depth. When diving at altitude, the
maximum and minimum percentage of oxygen associated with the diver’s actual
depth rather than his Sea Level Equivalent Depth should be used. There are two
important differences between diving helium-oxygen and diving air at altitude:
n Table 9-5 and Figure 9-15 cannot be used to correct the bottom time of a diver
who is not fully equilibrated at altitude. The diver should wait 12 hours after
arrival at altitude before making the first dive.
n Repetitive diving is not allowed during surface-supplied helium-oxygen diving
at altitude. Following a no-decompression dive, the diver must wait 12 hours
before making a another dive. Following a decompression dive, the diver must
wait 18 hours before making another dive. A second dive is allowed following
an abort during descent at depth of 100 fsw or less. Follow the guidance given
in paragraph 12-4.6. Substitute the diver’s maximum Sea Level Equivalent
Depth for the diver’s maximum depth when computing the table and schedule
for the second dive.

12-26

U.S. Navy Diving Manual — Volume 3

Date:

Type of Dive:

Diver 1:

AIR

HeO2

Diver 2:

Rig:

PSIG:

O2%:

Diving Supervisor:
EVENT

Rig:

Standby:
PSIG:

O2%:

Rig:

Chartman:
STOP TIME

CLOCK TIME

LS or 20 fsw

PSIG:

O2%:

Bottom Mix:
EVENT

TIME/DEPTH

Descent Time (Water)

RB

Stage Depth (fsw)

LB

Maximum Depth (fsw)

st

Total Bottom Time

R 1 Stop
190 fsw

Table/Schedule

180 fsw

Time to 1st Stop (Actual)

170 fsw

Time to 1st Stop (Planned)

160 fsw

Delay to 1st Stop

150 fsw

Travel/Shift/Vent Time

140 fsw

Ascent Time-Water/SurD (Actual)

130 fsw

Undress Time-SurD (Actual)

120 fsw

Descent Chamber-SurD (Actual)

110 fsw

Total SurD Surface Interval

100 fsw

Ascent Time–Chamber (Actual)

90 fsw

HOLDS ON DESCENT

80 fsw

DEPTH

PROBLEM

70 fsw
60 fsw
50 fsw
40 fsw

DELAYS ON ASCENT

30 fsw

DEPTH

PROBLEM

20 fsw
RS
RB CHAMBER
50 fsw chamber

DECOMPRESSION PROCEDURES USED

40 fsw chamber

AIR

30 fsw chamber
RS CHAMBER
TDT

TTD

HeO2

o In-water Air decompression
o In-water Air/O2 decompression
o SurDO2
o In-water HeO2/O2 decompression
o SurDO2

REPETITIVE GROUP:
Remarks:

Figure 12-4. Diving Chart.

CHAPTER 12 — Surface-Supplied Mixed Gas Diving

12-27

1210
Date: 4 Sept 07

Type of Dive:

AIR

Diver 1: NDC Credle

HeO2

Diver 2: ND1 Hopkins

Standby: NDC Fleming

Rig: KM 37 PSIG: 3000 O2%: 16.2

Rig: KM 37 PSIG: 3000 O2%: 16.2

Rig: KM 37 PSIG: 3000 O2%:16.2

Diving Supervisor: NDCM Boyd

Chartman: EN2 Golden

Bottom Mix: 15.2

EVENT

STOP TIME

CLOCK TIME

EVENT

TIME/DEPTH

LS or 20 fsw

0800

Descent Time (Water)

:04

RB

0804

Stage Depth (fsw)

212

LB

0839

Maximum Depth (fsw)

st

0843

R 1 Stop

222+4=226

Total Bottom Time

:39

190 fsw

Table/Schedule

230/40

180 fsw

Time to 1st Stop ( Actual)

:03::49

170 fsw

Time to 1

160 fsw

Delay to 1 Stop

150 fsw

Travel/Shift/Vent Time

140 fsw

Ascent Time-Water/SurD (Actual)

:01::03

130 fsw

Undress Time-SurD (Actual)

:02::15

Stop (Planned)

:03::24
::25

st

120 fsw
110 fsw

st

Descent Chamber-SurD (Actual)
0850

:07

100 fsw
90 fsw

:03

0853

80 fsw

:07

0900

70 fsw

:09

0909

60 fsw

:13

0922

50 fsw

:13

0935

40 fsw

:13

0948

30 fsw

::58

Total SurD Surface Interval

:04::16

Ascent Time–Chamber (Actual)

:01::20

HOLDS ON DESCENT
DEPTH

PROBLEM

DELAYS ON ASCENT
DEPTH

PROBLEM

20 fsw
0950

RS
RB CHAMBER

0953

50 fsw chamber

:15

1008

40 fsw chamber

:15+:5+:30+:5+:30
:5+:30

1208

DECOMPRESSION PROCEDURES USED
AIR

30 fsw chamber
RS CHAMBER
TDT
3:31

1210
TTD
4:10

HeO2

o In-water Air decompression
o In-water Air/O2 decompression
o SurDO2
o In-water HeO2/O2 decompression
 SurDO2

REPETITIVE GROUP:

Remarks:

Figure 12-5. Completed HeO2 Diving Chart: Surface Decompression Dive.

12-28

U.S. Navy Diving Manual — Volume 3

1139
Date: 4 Sept 07

Type of Dive:

AIR

HeO2

Diver 1: NDC Allred

Diver 2: ND1 Wittman

Standby: ND1 Schlabach

Rig: KM-37 NS PSIG: 2950 O2%:16.2

Rig: KM-37 NS PSIG: 2950 O2%:16.2

Rig: KM-37 NS PSIG:2950 O2%:16.2

Diving Supervisor: NDCM Van
Horn

Chartman: NDC Parsons

Bottom Mix: 15.2

EVENT

STOP TIME

CLOCK TIME

EVENT

TIME/DEPTH

LS or 20 fsw

0800

Descent Time (Water)

:04

RB

0804

Stage Depth (fsw)

212

LB

0839

Maximum Depth (fsw)

st

0843

R 1 Stop

222+4=226

Total Bottom Time

:39

190 fsw

Table/Schedule

230/40

180 fsw

Time to 1st Stop ( Actual)

:03::49

170 fsw

Time to 1

st

Stop (Planned)

:03::24

160 fsw

st

Delay to 1 Stop

::25

150 fsw

Travel/Shift/Vent Time

:02

140 fsw

Ascent Time-Water/SurD (Actual)

::40

130 fsw

Undress Time-SurD (Actual)

120 fsw
110 fsw

Descent Chamber-SurD (Actual)
:07

0850

100 fsw

Total SurD Surface Interval
Ascent Time–Chamber (Actual)

90 fsw

:03

0853

80 fsw

:07

0900

70 fsw

:09

0909

60 fsw

:13

0922

50 fsw

:13

0935

40 fsw

:13

0948

30 fsw

:2+:30+:5+:4

1029

20 fsw

:26+:5+:30+:5+:8

1143

HOLDS ON DESCENT
DEPTH

PROBLEM

DELAYS ON ASCENT
DEPTH

PROBLEM

1144

RS
RB CHAMBER
50 fsw chamber

DECOMPRESSION PROCEDURES USED

40 fsw chamber

AIR

30 fsw chamber
RS CHAMBER
TDT
3:05

TTD
3:44

HeO2

o In-water Air decompression
o In-water Air/O2 decompression
o SurDO2
 In-water HeO2/O2 decompression
o SurDO2

REPETITIVE GROUP:

Remarks:

Figure 12-6. Completed HeO2 Diving Chart: In-water Decompression Dive.

CHAPTER 12 — Surface-Supplied Mixed Gas Diving

12-29

1210
Date: 4 Sept 07

Type of Dive:

AIR

HeO2

Diver 1: ND2 Costin

Diver 2: ND1 Hatter

Standby: NDC Keller

Rig: KM-37 NS PSIG: 2950 O2%:16.2

Rig: KM-37 NS PSIG: 2950 O2%:16.2

Rig: KM-37 NS PSIG:2950 O2%:16.2

Diving Supervisor: NDCM
Pratschner

Chartman: ND2 Juarez

Bottom Mix: 15.2

EVENT

STOP TIME

CLOCK TIME

EVENT

TIME/DEPTH

LS or 20 fsw

0800

Descent Time (Water)

:07

RB

0807

Stage Depth (fsw)

212

LB

0838

Maximum Depth (fsw)

st

0843

222+4=226

Total Bottom Time

:38 + :02 = :40

190 fsw

Table/Schedule

230/40 Sur D

180 fsw

R 1 Stop

Time to 1

st

Stop ( Actual)

:04::47

170 fsw

Time to 1

st

Stop (Planned)

:03::24

160 fsw

Delay to 1 Stop

150 fsw

Travel/Shift/Vent Time

140 fsw

Ascent Time-Water/SurD (Actual)

:01::03

130 fsw

Undress Time-SurD (Actual)

:02::05

120 fsw
110 fsw

:07

0850

100 fsw

Descent Chamber-SurD (Actual)

:01::25

Total SurD Surface Interval

:04::33

Ascent Time–Chamber (Actual)

:01::20

90 fsw

:03

0853

80 fsw

:07

0900

DEPTH

70 fsw

:09

0909

32'

60 fsw

:13

0922

50 fsw

:13

0935

40 fsw

:13

0948

HOLDS ON DESCENT

DEPTH

20 fsw

150'

RB CHAMBER

30 fsw chamber

3:32

Winch wire (fixed)

0953
:15

1008

:15+:5+:30+:5+
:30+:5+:30

1208

RS CHAMBER
TDT

PROBLEM

0950

RS

40 fsw chamber

PROBLEM
Red—right ear

DELAYS ON ASCENT

30 fsw

50 fsw chamber

:01::23

st

DECOMPRESSION PROCEDURES USED
AIR

1210
TTD
4:10

HeO2

o In-water Air decompression
o In-water Air/O2 decompression
o SurDO2
o In-water HeO2/O2 decompression
 SurDO2

REPETITIVE GROUP:

Remarks: 1. Delay on Ascent. Added :02 to bottom time. Did not change schedule.
2. Red diver had trouble clearing due to position of nose clearing device. DMT checked ears post dive. No
barotrauma noted.
Figure 12‑7. Completed HeO2 Diving Chart: Surface Decompression Dive with Hold on Descent and Delay
on Ascent.
12-30

U.S. Navy Diving Manual — Volume 3

CHAPTER 12 — Surface-Supplied Mixed Gas Diving

12-31

Max O2=34.9%
Min O2=14.0%

90

Max O2=38.0%
Min O2=14.0%

80

Max O2=40.0%
Min O2=14.0%

70

Max O2=40.0%
Min O2=14.0%

60

Depth (fsw)

60

50

40

BOTTOM MIX

50% O2

10
10
10
10
10
10

70

3:00
3:00
1:40
1:40
1:40
1:40
1:40
1:40

80

10
20
30
40
60
80
100
120

90

10
10
10
10
10
10

100

2:40
2:40
2:40
1:20
1:20
1:20
1:20
1:20
1:20

110

10
20
25
30
40
60
80
100
120

120

10
10
10
10
10

130

2:20
2:20
2:20
1:00
1:00
1:00
1:00
1:00

140

10
20
30
40
60
80
100
120

150

10
10
10
10

160

2:00
2:00
2:00
2:00
0:40
0:40
0:40
0:40

170

10
20
30
40
60
80
100
120

180

Time to
First Stop
(min:sec)

Bottom
Time
(min.)

190

Stop times (min) include travel time, except first HeO2 and first O2 stop

Decompression Stops (fsw)

(DESCENT RATE 75 FPM—ASCENT RATE 30 FPM)

Table 12‑4. Surface-Supplied Helium-Oxygen Decompression Table

20

13
16
21
25
28
29

11
13
18
21
24
25

10
14
18
19
21

11
13
16
17

0
0
21
26
38
45
50
52

0
0
0
16
21
32
38
42
45

0
0
0
16
24
30
34
37

0
0
0
0
16
22
27
28

100% O2

30

0
0
2
2
2
3
3
3

0
0
0
1
2
2
2
3
3

0
0
0
1
2
2
2
2

0
0
0
0
1
2
2
2

Chamber
O2
Periods

12-32

U.S. Navy Diving Manual — Volume 3

Max O2=26.3%
Min O2=14.0%

130

Max O2=28.0%
Min O2=14.0%

120

Max O2=30.0%
Min O2=14.0%

110

Max O2=32.3%
Min O2=14.0%

100

Depth (fsw)
3:20
3:20
2:00
2:00
2:00
2:00
2:00
2:00
2:00

10
15
20
30
40
60
80
100
120

190

180
170

160

140

BOTTOM MIX

150

130
120

110

100

90

80
60

50% O2

70

50

10
10
10
10
10
10
10

40
20

11
15
18
25
28
31
32

0
0
17
24
32
44
52
56
58

100% O2

30

10
2:40
10
10
6
8
20
2:40
10
10
12
19
30
2:40
10
10
18
30
40
2:20
7
10
10
22
40
60
2:20
7
10
10
29
52
80
2:20
7
10
10
33
60
Exceptional Exposure ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------35
64
100
2:20
7
10
10
120
2:20
7
11
11
35
66

10
2:40
10
9
13
20
2:40
10
14
23
30
2:40
10
19
33
40
2:40
10
23
42
60
2:40
10
30
55
80
2:40
10
34
63
100
2:40
10
36
66
Exceptional Exposure ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------120
2:20
10
10
35
65

4
4

1
1
2
3
3
3

4

1
2
2
3
3
4
4

4

1
1
2
2
3
3
4

0
0
1
2
2
3
3
3
3

Chamber
O2
Periods

10
2:20
10
8
11
20
2:20
10
12
20
30
2:20
10
17
28
40
2:20
10
20
36
60
2:20
10
27
49
80
2:20
10
31
58
100
2:20
10
33
62
Exceptional Exposure ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------120
2:20
10
35
64

Time to
First Stop
(min:sec)

Bottom
Time
(min.)

Stop times (min) include travel time, except first HeO2 and first O2 stop

Decompression Stops (fsw)

(DESCENT RATE 75 FPM—ASCENT RATE 30 FPM)

Table 12‑4. Surface-Supplied Helium-Oxygen Decompression Table (Continued).

CHAPTER 12 — Surface-Supplied Mixed Gas Diving

12-33

Max O2=21.1%
Min O2=14.0%

170

Max O2=22.2%
Min O2=14.0%

160

Max O2=23.4%
Min O2=14.0%

150

Max O2=24.8%
Min O2=14.0%

140

Depth (fsw)

Time to
First Stop
(min:sec)

190

180
170

160

140

BOTTOM MIX

150

130
120

110

100

90

80
60

50% O2

70

50

40

20

100% O2

30

10
3:20
7
0
10
10
8
12
7
0
10
10
16
28
20
3:20
30
3:20
7
1
10
10
23
42
40
3:20
7
4
10
10
28
52
60
3:20
7
10
10
10
33
62
Exceptional Exposure ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------80
3:20
9
14
14
14
35
66
100
3:00
7
5
18
18
18
36
66
120
3:00
7
9
21
21
21
36
66

10
3:20
7
10
10
8
10
20
3:20
7
10
10
15
24
30
3:20
7
10
10
21
37
40
3:20
7
10
10
26
47
60
3:00
7
6
10
10
30
56
Exceptional Exposure ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------80
3:00
7
9
10
10
35
66
100
3:00
7
13
14
14
35
66
120
3:00
7
17
17
17
36
66

10
3:20
10
10
7
8
20
3:00
7
10
10
14
22
30
3:00
7
10
10
19
34
3:00
7
10
10
24
44
40
60
3:00
7
10
10
31
56
80
3:00
7
10
10
35
64
Exceptional Exposure ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------100
3:00
7
13
13
36
66
120
3:00
9
16
16
36
66

4
5
5

1
2
3
3
4

4
5
5

1
2
2
3
3

4
5

1
2
2
3
3
4

4
4

1
1
2
2
3
3

Chamber
O2
Periods

10
3:00
10
10
6
8
20
3:00
10
10
12
19
30
3:00
10
10
18
30
40
2:40
7
10
10
22
40
60
2:40
7
10
10
29
52
80
2:40
7
10
10
33
60
Exceptional Exposure ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------100
2:40
7
10
10
35
64
120
2:40
7
11
11
35
66

Bottom
Time
(min.)

Stop times (min) include travel time, except first HeO2 and first O2 stop

Decompression Stops (fsw)

(DESCENT RATE 75 FPM—ASCENT RATE 30 FPM)

Table 12‑4. Surface-Supplied Helium-Oxygen Decompression Table (Continued).

12-34

U.S. Navy Diving Manual — Volume 3

Max O2=21.1%
Min O2=14.0%

170

Max O2=22.2%
Min O2=14.0%

160

Max O2=23.4%
Min O2=14.0%

150

Max O2=24.8%
Min O2=14.0%

140

Depth (fsw)

Time to
First Stop
(min:sec)

190

180
170

160

140

BOTTOM MIX

150

130
120

110

100

90

80
60

50% O2

70

50

40
20

100% O2

30

10
3:20
7
0
10
10
8
12
7
0
10
10
16
28
20
3:20
30
3:20
7
1
10
10
23
42
40
3:20
7
4
10
10
28
52
60
3:20
7
10
10
10
33
62
Exceptional Exposure ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------80
3:20
9
14
14
14
35
66
100
3:00
7
5
18
18
18
36
66
120
3:00
7
9
21
21
21
36
66

10
3:20
7
10
10
8
10
20
3:20
7
10
10
15
24
30
3:20
7
10
10
21
37
40
3:20
7
10
10
26
47
60
3:00
7
6
10
10
30
56
Exceptional Exposure ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------80
3:00
7
9
10
10
35
66
100
3:00
7
13
14
14
35
66
120
3:00
7
17
17
17
36
66

10
3:20
10
10
7
8
20
3:00
7
10
10
14
22
30
3:00
7
10
10
19
34
3:00
7
10
10
24
44
40
60
3:00
7
10
10
31
56
80
3:00
7
10
10
35
64
Exceptional Exposure ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------100
3:00
7
13
13
36
66
120
3:00
9
16
16
36
66

4
5
5

1
2
3
3
4

4
5
5

1
2
2
3
3

4
5

1
2
2
3
3
4

4
4

1
1
2
2
3
3

Chamber
O2
Periods

10
3:00
10
10
6
8
20
3:00
10
10
12
19
30
3:00
10
10
18
30
40
2:40
7
10
10
22
40
60
2:40
7
10
10
29
52
80
2:40
7
10
10
33
60
Exceptional Exposure ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------100
2:40
7
10
10
35
64
120
2:40
7
11
11
35
66

Bottom
Time
(min.)

Stop times (min) include travel time, except first HeO2 and first O2 stop

Decompression Stops (fsw)

(DESCENT RATE 75 FPM—ASCENT RATE 30 FPM)

Table 12‑4. Surface-Supplied Helium-Oxygen Decompression Table (Continued).

CHAPTER 12 — Surface-Supplied Mixed Gas Diving

12-35

Max O2=17.7%
Min O2=10.0%

210

Max O2=18.4%
Min O2=14.0%

200

Max O2=19.2%
Min O2=14.0%

190

Max O2=20.1%
Min O2=14.0%

180

Depth (fsw)

Time to
First Stop
(min:sec)

190

180
170

160

140

BOTTOM MIX

150

130
120

110

100

90

80
60

50% O2

70

50

40

20

100% O2

30

10
4:20
7
0
0
10
10
12
19
20
4:00
7
0
1
6
10
10
22
38
30
4:00
7
0
6
7
10
10
29
53
40
4:00
7
3
9
10
10
10
33
60
Exceptional Exposure ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------60
3:40
7
0
9
11
17
17
17
35
66
80
3:40
7
3
11
15
20
20
20
36
66
100
3:40
7
6
14
19
23
23
23
36
66
23
23
23
36
66
120
3:40
7
8
18
23

10
4:00
7
0
0
10
10
11
17
20
4:00
7
0
4
10
10
20
36
30
3:40
7
0
3
7
10
10
27
50
40
3:40
7
0
7
10
10
10
31
58
Exceptional Exposure ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------4
10
14
14
14
35
66
60
3:40
7
80
3:40
7
8
14
18
18
18
36
66
100
3:40
7
12
17
23
23
23
36
66
120
3:40
8
15
21
23
23
23
36
66

10
4:00
7
0
10
10
10
15
20
3:40
7
0
2
10
10
19
34
30
3:40
7
0
7
10
10
26
46
40
3:40
7
4
9
10
10
31
56
Exceptional Exposure ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------60
3:40
7
9
13
13
13
34
62
80
3:20
7
3
13
18
18
18
36
66
100
3:20
7
6
16
21
21
21
36
66
120
3:20
7
8
20
23
23
23
36
66

5
6
7
7

1
2
3
3

4
5
6
7

1
2
3
3

4
5
6
7

1
2
3
3

4
5
6

1
2
3
3
4

Chamber
O2
Periods

10
3:40
7
0
10
10
9
14
20
3:40
7
0
10
10
17
30
30
3:40
7
4
10
10
25
45
40
3:20
7
0
8
10
10
30
54
60
3:20
7
5
11
11
11
35
64
Exceptional Exposure ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------80
3:20
7
9
15
15
15
36
66
100
3:20
7
13
19
19
19
36
66
120
3:20
7
17
23
23
23
36
66

Bottom
Time
(min.)

Stop times (min) include travel time, except first HeO2 and first O2 stop

Decompression Stops (fsw)

(DESCENT RATE 75 FPM—ASCENT RATE 30 FPM)

Table 12‑4. Surface-Supplied Helium-Oxygen Decompression Table (Continued).

12-36

U.S. Navy Diving Manual — Volume 3

Max O2=15.2%
Min O2=10.0%

250

Max O2=15.7%
Min O2=10.0%

240

Max O2=16.3%
Min O2=10.0%

230

Max O2=17.0%
Min O2=10.0%

220

Depth (fsw)

Time to
First Stop
(min:sec)

190

180
170

160

140

BOTTOM MIX

150

130
120

110

100

90

80
60

50% O2

70

50

40
20

100% O2

30

10
5:00
7
0
0
3
4
10
10
15
25
20
4:40
7
0
0
3
7
7
10
10
26
47
30
4:40
7
0
4
6
8
10
10
10
32
60
4:40
7
2
5
9
9
14
14
14
35
64
40
Exceptional Exposure ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------60
4:20
7
0
7
9
12
16
21
21
21
36
66
80
4:20
7
3
9
13
15
21
23
23
23
36
66
100
4:20
7
6
11
14
19
23
23
23
23
36
66
120
4:20
7
8
13
19
20
23
23
23
23
36
66

10
4:40
7
0
0
3
4
10
10
14
24
5
7
10
10
25
46
20
4:40
7
0
3
30
4:20
7
0
3
6
7
10
10
10
32
58
40
4:20
7
0
5
8
9
14
14
14
35
64
Exceptional Exposure ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------60
4:20
7
4
8
11
14
19
19
19
36
66
80
4:20
7
7
11
16
18
23
23
23
36
66
100
4:20
7
10
14
19
23
23
23
23
36
66
120
4:00
7
3
12
17
19
23
23
23
23
36
66

10
4:40
7
0
0
3
10
10
14
22
20
4:20
7
0
3
4
7
10
10
24
44
30
4:20
7
0
5
7
10
10
10
31
57
40
4:00
7
0
3
7
9
13
13
13
34
64
Exceptional Exposure ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------60
4:00
7
0
8
10
14
18
18
18
36
66
80
4:00
7
3
10
14
18
23
23
23
36
66
100
4:00
7
6
12
17
23
23
23
23
36
66
120
4:00
7
7
16
19
23
23
23
23
36
66

6
7
8
8

2
3
4
4

6
7
8
8

2
3
3
4

6
7
8
8

2
3
3
4

5
6
7
8

1
3
3
4

Chamber
O2
Periods

10
4:40
7
0
2
10
10
13
20
20
4:20
7
0
3
7
10
10
23
41
30
4:20
7
2
6
9
10
10
30
54
40
4:00
7
0
6
9
11
11
11
34
62
Exceptional Exposure ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------60
4:00
7
4
9
12
18
18
18
36
66
80
4:00
7
8
12
17
21
21
21
36
66
100
4:00
7
12
15
20
23
23
23
36
66
23
23
23
23
36
66
120
4:00
8
14
19

Bottom
Time
(min.)

Stop times (min) include travel time, except first HeO2 and first O2 stop

Decompression Stops (fsw)

(DESCENT RATE 75 FPM—ASCENT RATE 30 FPM)

Table 12‑4. Surface-Supplied Helium-Oxygen Decompression Table (Continued).

CHAPTER 12 — Surface-Supplied Mixed Gas Diving

12-37

Max O2=13.3%
Min O2=10.0%

290

Max O2=13.7%
Min O2=10.0%

280

Max O2=14.2%
Min O2=10.0%

270

Max O2=14.6%
Min O2=10.0%

260

Depth (fsw)

Time to
First Stop
(min:sec)

190

180
170

160

140

BOTTOM MIX

150

130
120

110

100

90

80
60

50% O2

70

50

40

20
100% O2

30

10
5:40
7
0
0
0
4
3
4
10
10
19
33
20
5:20
7
0
0
2
6
6
6
9
10
10
30
56
30
5:20
7
0
2
5
5
9
9
14
14
14
34
63
Exceptional Exposure ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------40
5:20
7
0
5
7
8
11
13
17
17
17
35
66
60
5:00
7
0
6
7
9
12
15
20
23
23
23
36
66
80
5:00
7
2
8
10
12
16
19
23
23
23
23
36
66
100
5:00
7
5
10
12
15
19
20
23
23
23
23
36
66
16
17
19
20
23
23
23
23
36
66
120
5:00
7
8
11

10
5:40
7
0
0
3
3
4
10
10
18
31
20
5:20
7
0
0
4
6
7
7
10
10
30
54
30
5:00
7
0
1
5
5
9
9
12
12
12
35
64
Exceptional Exposure ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------40
5:00
7
0
4
6
8
9
12
17
17
17
35
66
60
5:00
7
4
6
8
12
15
18
23
23
23
36
66
80
4:40
7
0
7
9
11
15
17
23
23
23
23
36
66
100
4:40
7
2
9
11
15
17
20
23
23
23
23
36
66
4
11
13
16
19
20
23
23
23
23
36
66
120
4:40
7

10
5:20
7
0
0
3
3
4
10
10
17
28
20
5:00
7
0
0
3
6
6
8
10
10
29
52
30
5:00
7
0
3
6
6
9
13
13
13
34
62
Exceptional Exposure ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------40
4:40
7
0
2
5
8
8
12
16
16
16
35
66
60
4:40
7
0
6
8
10
14
19
23
23
23
36
66
80
4:40
7
3
8
11
14
17
23
23
23
23
36
66
36
66
100
4:40
7
5
11
13
16
20
23
23
23
23
120
4:40
7
8
12
16
19
20
23
23
23
23
36
66

5
7
8
8
8

2
3
5

5
7
8
8
8

2
3
4

5
6
7
8
8

2
3
4

6
7
8
8

2
3
4
5

Chamber
O2
Periods

10
5:00
7
0
0
0
4
4
10
10
16
27
20
5:00
7
0
3
4
6
7
10
10
27
50
30
4:40
7
0
2
5
6
9
10
10
10
33
62
40
4:40
7
0
3
8
9
10
15
15
15
35
64
Exceptional Exposure ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------60
4:40
7
3
7
10
14
16
21
21
21
36
66
80
4:40
7
6
10
13
17
23
23
23
23
36
66
2
9
13
16
20
23
23
23
23
36
66
100
4:20
7
120
4:20
7
4
11
14
19
20
23
23
23
23
36
66

Bottom
Time
(min.)

Stop times (min) include travel time, except first HeO2 and first O2 stop

Decompression Stops (fsw)

(DESCENT RATE 75 FPM—ASCENT RATE 30 FPM)

Table 12‑4. Surface-Supplied Helium-Oxygen Decompression Table (Continued).

12-38

U.S. Navy Diving Manual — Volume 3

Max O2=11.8%
Min O2=10.0%

330

Max O2=12.2%
Min O2=10.0%

320

Max O2=12.5%
Min O2=10.0%

310

Max O2=12.9%
Min O2=10.0%

300

Depth (fsw)

140
120

110

100

90

80
60

50% O2

70

50

40
20

100% O2

30

2
3
5

Chamber
O2
Periods

2
4
6
7
8
8
8
8

130

Exceptional Exposure ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------10
6:20
7
0
0
0
2
3
3
4
7
10
10
22
40
20
6:00
7
0
0
2
3
4
6
5
10
10
10
10
33
60
30
6:00
7
0
1
4
5
6
8
8
13
17
17
17
35
66
40
5:40
7
0
1
4
5
7
7
10
12
17
22
22
22
36
66
60
5:40
7
0
5
6
8
9
11
15
20
23
23
23
23
36
66
80
5:40
7
2
7
8
10
13
15
19
20
23
23
23
23
36
66
100
5:40
7
5
9
9
13
16
17
19
20
23
23
23
23
36
66
120
5:20
7
1
7
10
13
15
16
17
19
20
23
23
23
23
36
66

BOTTOM MIX

150

2
4
5
6
8
8
8
8

160

Exceptional Exposure ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------10
6:20
7
0
0
0
4
3
3
7
10
10
21
38
20
6:00
7
0
0
3
5
5
6
8
10
10
10
32
59
30
5:40
7
0
0
4
4
6
7
9
11
17
17
17
35
66
40
5:40
7
0
4
4
6
7
9
12
16
20
20
20
36
66
36
66
60
5:20
7
0
2
6
8
9
11
14
17
23
23
23
23
80
5:20
7
0
6
8
8
13
14
19
20
23
23
23
23
36
66
100
5:20
7
2
7
10
13
16
17
19
20
23
23
23
23
36
66
120
5:20
7
4
9
12
13
16
17
19
20
23
23
23
23
36
66

170

2
4
5
7
8
8
8
8

180

Exceptional Exposure ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------10
6:00
7
0
0
0
3
3
3
7
10
10
21
36
20
5:40
7
0
0
2
4
5
6
7
10
10
10
31
57
30
5:40
7
0
2
4
5
7
8
11
15
15
15
35
66
40
5:20
7
0
1
4
6
7
8
12
15
19
19
19
36
66
60
5:20
7
0
5
6
9
11
13
17
20
23
23
23
36
66
11
13
17
20
23
23
23
23
36
66
80
5:20
7
3
7
9
100
5:20
7
5
9
11
13
17
19
20
23
23
23
23
36
66
120
5:20
7
7
12
13
16
17
19
20
23
23
23
23
36
66

190

6
7
8
8
8

Time to
First Stop
(min:sec)

10
6:00
7
0
0
0
4
3
4
10
10
19
33
20
5:40
7
0
0
2
6
6
6
9
10
10
30
56
30
5:40
7
0
2
5
5
9
9
14
14
14
34
63
Exceptional Exposure ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------40
5:40
7
0
5
7
8
11
13
17
17
17
35
66
60
5:20
7
0
6
7
9
12
15
20
23
23
23
36
66
23
23
23
36
66
80
5:20
7
2
8
10
12
16
19
23
100
5:20
7
5
10
12
15
19
20
23
23
23
23
36
66
120
5:20
7
8
11
16
17
19
20
23
23
23
23
36
66

Bottom
Time
(min.)

Stop times (min) include travel time, except first HeO2 and first O2 stop

Decompression Stops (fsw)

(DESCENT RATE 75 FPM—ASCENT RATE 30 FPM)

Table 12‑4. Surface-Supplied Helium-Oxygen Decompression Table (Continued).

CHAPTER 12 — Surface-Supplied Mixed Gas Diving

12-39

Max O2=10.9%
Min O2=10.0%

360

Max O2=11.2%
Min O2=10.0%

350

Max O2=11.5%
Min O2=10.0%

340

Depth (fsw)

140

BOTTOM MIX

150

130
120

110

100

90

80
60

50% O2

70

50

40

20

100% O2

30

Chamber
O2 Periods

3
5
7
8
8
8
8
8

160

Exceptional Exposure ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------10
7:00
7
0
0
0
2
2
3
3
7
7
10
10
25
44
20
6:40
7
0
0
2
3
4
5
5
8
10
13
13
13
34
63
13
19
19
19
36
66
30
6:20
7
0
0
3
3
5
6
7
8
11
40
6:20
7
0
2
4
5
7
7
9
10
14
20
23
23
23
36
66
60
6:20
7
2
5
6
7
9
11
14
16
19
23
23
23
23
36
66
80
6:00
7
0
6
6
8
11
12
14
16
19
20
23
23
23
23
36
66
100
6:00
7
2
7
8
11
13
13
16
17
19
20
23
23
23
23
36
66
120
6:00
7
4
8
10
12
14
15
16
17
19
20
23
23
23
23
36
66

170

3
5
6
7
8
8
8
8

180

Exceptional Exposure ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------10
6:40
7
0
0
0
2
2
3
3
5
7
10
10
24
43
20
6:20
7
0
0
0
4
4
5
5
7
9
13
13
13
33
63
30
6:20
7
0
1
4
4
5
7
8
11
13
18
18
18
36
66
40
6:00
7
0
1
3
5
6
7
8
11
14
17
23
23
23
36
66
60
6:00
7
0
5
5
8
8
11
12
16
19
23
23
23
23
36
66
80
6:00
7
2
7
7
10
11
13
17
19
20
23
23
23
23
36
66
100
5:40
7
0
6
8
9
11
15
16
17
19
20
23
23
23
23
36
66
120
5:40
7
1
7
9
12
14
15
16
17
19
20
23
23
23
23
36
66

190

3
5
6
7
8
8
8
8

Time to
First Stop
(min:sec)

Exceptional Exposure ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------10
6:40
7
0
0
0
3
3
3
4
7
10
10
23
41
20
6:20
7
0
0
2
4
5
7
8
9
10
10
10
33
60
30
6:00
7
0
0
3
5
5
6
8
9
13
18
18
18
35
66
40
6:00
7
0
2
4
6
7
8
10
13
16
22
22
22
36
66
60
5:40
7
0
3
5
6
9
10
13
16
18
21
23
23
23
36
66
80
5:40
7
0
7
7
8
11
13
15
19
20
23
23
23
23
36
66
100
5:40
7
2
8
8
12
13
16
17
19
20
23
23
23
23
36
66
120
5:40
7
4
9
11
13
15
16
17
19
20
23
23
23
23
36
66

Bottom
Time
(min.)

Stop times (min) include travel time, except first HeO2 and first O2 stop

Decompression Stops (fsw)

(DESCENT RATE 75 FPM—ASCENT RATE 30 FPM)

Table 12‑4. Surface-Supplied Helium-Oxygen Decompression Table (Continued).

12-40

U.S. Navy Diving Manual — Volume 3

Max O2=10.4%
Min O2=10.0%

380

Max O2=10.6%
Min O2=10.0%

370

Depth (fsw)

170

160

140

BOTTOM MIX

150

130
120

110

100

90

80
60

50% O2

70

50

40
20

100% O2

30

Chamber
O2 Periods

3
6
7
8
8
8
8
8

180

Exceptional Exposure ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------10
7:20
7
0
0
0
0
3
3
3
3
7
7
10
10
25
46
20
7:00
7
0
0
0
3
4
4
5
5
8
10
13
13
13
34
63
30
6:40
7
0
0
2
3
4
4
7
7
8
11
16
19
19
19
36
66
40
6:40
7
0
0
4
4
5
6
8
10
11
14
20
23
23
23
36
66
60
6:40
7
0
4
5
7
8
9
11
13
17
20
23
23
23
23
36
66
80
6:20
7
0
3
6
7
9
10
12
15
17
19
20
23
23
23
23
36
66
100
6:20
7
0
6
7
9
10
14
15
16
17
19
20
23
23
23
23
36
66
120
6:20
7
1
7
9
11
13
14
15
16
17
19
20
23
23
23
23
36
66

190

3
5
7
8
8
8
8
8

Time to
First Stop
(min:sec)

Exceptional Exposure ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------10
7:00
7
0
0
0
0
3
3
3
3
7
7
10
10
25
46
20
6:40
7
0
0
0
3
4
4
5
5
8
10
13
13
13
34
63
30
6:20
7
0
0
2
3
4
4
7
7
8
11
16
19
19
19
36
66
40
6:20
7
0
0
4
4
5
6
8
10
11
14
20
23
23
23
36
66
9
11
13
17
20
23
23
23
23
36
66
60
6:20
7
0
4
5
7
8
80
6:00
7
0
3
6
7
9
10
12
15
17
19
20
23
23
23
23
36
66
100
6:00
7
0
6
7
9
10
14
15
16
17
19
20
23
23
23
23
36
66
120
6:00
7
1
7
9
11
13
14
15
16
17
19
20
23
23
23
23
36
66

Bottom
Time
(min.)

Stop times (min) include travel time, except first HeO2 and first O2 stop

Decompression Stops (fsw)

(DESCENT RATE 75 FPM—ASCENT RATE 30 FPM)

Table 12‑4. Surface-Supplied Helium-Oxygen Decompression Table (Continued).

CHAPTER 13

Saturation Diving

Figure 13-1. SAT FADS System.

13-1

INTRODUCTION
13-1.1

Purpose. The purpose of this chapter is to familiarize divers with U.S. Navy

saturation diving systems and deep diving equipment.

13-1.2

Scope. Saturation diving is used for deep salvage or recovery using U.S. Navy

deep diving systems or equipment. These systems and equipment are designed to
support personnel at depths to 1000 fsw for extended periods of time.

13-2

DEEP DIVING SYSTEMS
13-2.1

APPLICATIONS

The Deep Diving System (DDS) is a versatile tool in diving and its application
is extensive. The Navy currently operates the Fly Away Saturation Dive System,
(SAT FADS) which has a 1000 fsw capability and employs a multilock Deck
Decompression Chamber (DDC) and a Dive Bell (DB).
n Non-Saturation Diving. Non-saturation diving can be accomplished with the
system pressurized to a planned depth. This mode of operation has limited real
time application and therefore is seldom used operationally in the U.S. Navy
but is used extensively for training.
n Saturation Diving. Deep Ocean underwater projects that demand extensive
bottom time (i.e. large construction projects, submarine rescue, and salvage)
are best conducted with a DDS in the saturation mode.
n Conventional Diving Support. The DDC portion of a saturation system can
be employed as a recompression chamber in support of conventional, surfacesupplied diving operations.
CHAPTER 13 — Saturation Diving

13-1

Bell Unbilical
Guide Wire

Bell Side Hatch

HEOX Bank

Oxygen
Banks

Bumper Ring
Lower Hatch
Figure 13-2. SAT FADS Dive Bell Exterior.

13-3

BASIC COMPONENTS OF THE U.S. NAVY FLY AWAY SATURATION DIVE SYSTEM,
(SAT FADS)

The configuration and the specific equipment composing the SAT FADS diving
system can vary based primarily on the type mission for which it is being deployed
and the capability of the support vessel. Major components include a Dive Bell, a
Launch and Recovery handling system (LARS), and a DDC (Figure 13-1).
13-3.1

Dive Bell. (Figure 13-2 and 13-11) is a spherical, submersible pressure vessel

designed to transfer divers in full diving dress, along with work tools and
associated operating equipment, from the deck of the surface vessel to their
designated working depth.

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U.S. Navy Diving Manual — Volume 3

Figure 13-3. SAT FADS DDC Interior.

13‑3.1.1

Gas Supplies. During normal diving operations, the divers’ breathing and Dive

Bell gas are supplied from the surface through a gas supply hose. In addition, the
Dive Bell carries emergency supplies of helium-oxygen, and oxygen in externally
mounted flasks. Internal Dive Bell pressure, gas supply pressures, and water depth
are continuously monitored from the Dive Bell.
The helium-oxygen mixed-gas system consists of an internal built-in breathing
system (BIBS) with associated valves, piping, and fittings. The mixed-gas system
supplies emergency breathing gas to the diver umbilical when the topside
supply is interrupted, and supplies the BIBS if the internal Bell atmosphere is
contaminated.

13‑3.1.2

Dive Bell Pressurization/Depressurization System. The gas supply and exhaust

system control and regulate internal Bell pressure. Relief valves and manual
vent valves prevent over pressurization of the Bell in case a line rupture causes
a full flask to discharge into the Bell. Needle valves are employed to control
depressurization. Depth gauges, calibrated in feet of seawater, monitor internal
and external Bell depth. Equalization and vent valves are also provided for the
access trunk.

13‑3.1.3

Dive Bell Life-Support System. The life-support equipment for the Dive Bell

includes carbon dioxide scrubber, oxygen for metabolic make-up, internal Bell
heater, BIBS and carbon dioxide/02 analyzers.

13‑3.1.4

Electrical System. The electrical system uses DC power for internal and external
lighting, instrumentation, and communications. Power for normal Bell operation

CHAPTER 13 — Saturation Diving

13-3

is surface-supplied and is transmitted through the main Dive Bell Umbilical.
Externally mounted emergency batteries supply critical loads such as atmosphere
monitoring, CO2 scrubber operation, emergency lighting and communications if
the surface-supplied power is interrupted or lost.
13‑3.1.5

Communications System. The SAT FADS Communication System is located in
the Control Van (CV) and is made up of five (5) independent systems:

n Amron Control Communication System-Full Duplex: The Control
Communication System-Full Duplex allows the Diving Supervisor to talk to
the Outer Lock (OL), Living Chamber (LC), Bell Tender, Divers and Bell
Handlers.
n Intercom: The Intercom System allows communication between the Diving
Supervisor/Master Diver and 7 external stations: Auxiliary (AUX) Van 1, AUX
Van 2, Vessel of Opportunity (VOO), Service Lock, Deck Station 1, Deck
Station 2 and Secondary Site.
n Surveillance: The Surveillance System provides continuous communication in
the OL, LC and Bell with Dive Watch Supervisor/Master Diver at all times.
n Through Water Communications: Through Water Communications provides
communication between the Dive Bell and Control Van in the event of primary
communications failure or total loss of umbilical, (Lost Bell).
n Sound Powered Phones: Sound Powered Phones provide back-up
communication between the Diving Supervisor, OL, LC, Bell Tender, Service
Lock and deck stations.
13-3.1.5.1

Helium Speech Unscrambler. Divers in a hyperbaric environment, either in
the water or in chambers, breathe a mixture of helium and oxygen making their
speech distorted. A contributing factor to helium speech distortion is the increased
atmospheric pressure encountered in deep dives. Helium Speech Unscrambler
HSUs are used to convert a diver’s helium voice to near normal for understanding.
The SAT FADs utilizes 4 HSUs:

n Surveillance
n OL 1&2 and LC 1&2
n Bell Tender and Diver 1
n Diver 2 and Standby Diver
13-3.1.5.2

Closed-Circuit Television (CCTV). The CCTV consists of video cameras located in

and outside the Dive Bell, DDC and locations outside viewing the Bell Handling
stations. Video monitors are located in the Control Van.

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U.S. Navy Diving Manual — Volume 3

13‑3.1.6

Dive Bell Umbilical. The Bell Umbilical provides electrical power, wired

communications, instrumentation signals, breathing-gas supply hose, a hot water
hose, and a pneumofathometer.

13‑3.1.7

Diver Hot Water System. Hot water is necessary when conducting saturation

dives. The surface support vessel supplies hot water from two DHB-690 Divers
Hot Water Heaters via the Bell main umbilical thru the Bell to the diver’s suit
and breathing gas heater. The Bell operator monitors the water temperature and
ensures that the flow is adequate.

13-3.2

Deck Decompression Chamber (DDC). The DDC furnishes a dry environment for

accomplishing decompression and, if necessary, recompression (Figure 13-3). The
DDC is a multi-compartment, horizontal pressure vessel mounted on the surfacesupport vessel. The DDC is equipped with living, sanitary, and resting facilities for
the dive team. A service lock provides for the passage of food, medical supplies,
and other articles between the diving crew inside the chamber and topside support
personnel.
13‑3.2.1

13‑3.2.2

DDC Life-Support System (LSS). The DDC Life Support-System maintains the
chamber environment within acceptable limits for the comfort and safety of the
divers. The typical system consists of temperature and humidity control, carbon
dioxide removal, and equipment monitoring. Processing consists of filtering
particulate matter, removing carbon dioxide and gaseous odors, and controlling
temperature and humidity.
Potable Water/Sanitary System. The system consists of hot and cold water

supplies for operating the wash basin, shower, and head. Waste from the head and
shower/wash basin are discharged into a separate holding tanks for proper disposal
through the support vessels collection, holding, and transfer system.
13‑3.2.3

Fire Suppression System. The DDCs has fire-fighting provisions consisting

of an installed, automatic fresh water deluge system. DDCs and recompression
chambers have similar hyperbaric flammability hazards. Ignition sources and
combustion materials should be minimized during critical fire zone times.
13‑3.2.4

Control Van (Control). The Control Van is a central control and monitoring

area (Figure 13-4). The Control Van houses the controls for the gas supply and
atmosphere analysis for the DDC, atmosphere monitoring for the Dive Bell,
pressure gauges for gas banks, clocks, communications systems controls,
recorders, power supplies, and video monitors and switches for the DDC and Dive
Bell.

CHAPTER 13 — Saturation Diving

13-5

Figure 13-4. SAT FADS Control Van.

13‑3.2.5

Gas Supply Mixing and Storage. The DDC gas system provides oxygen, heliumoxygen mixtures, helium, and air for pressurization and diver life support. BIBS
are installed in every lock for emergency breathing in contaminated atmospheres,
as well as for administering treatment gas during recompression treatment. Normal
pressurizing or depressurizing of the DDC is done from the Control Van. A means
of sampling the internal atmosphere is provided for monitoring carbon dioxide
and oxygen partial pressure. An oxygen-addition system maintains oxygen partial
pressure at required levels. A pressure-relief system prevents overpressurization of
the chamber.

The SAT FADS DDS is outfitted with a gas-mixing component, commonly referred
to as a “Mixmaker,” which provides additional flexibility when conducting deep
saturation diving. The Mixmaker can provide mixed gas at precise percentages
and quantities needed for any given dive. If necessary, the gas coming from the
Mixmaker can be sent directly to the divers for consumption.
13-3.3

13‑3.3.1

Dive Bell Launch and Recovery System (LARS). Launch and recovery of the Dive
Bell presents significant hazards to the divers during heavy weather and are major
factors in configuring and operating the handling system.
SAT FADS LARS Characteristics. The SATFADS LARS handling systems has the
following characteristics (Figure 13-10):

n The System is designed and maintained to withstand the elements and dynamic
loads imposed by heavy weather.
n Has the ability to control the Bell through the air-sea interface at sufficient
speed to avoid excessive wave action.
n Keeps the Bell clear of the superstructure of the surface-support platform to
avoid impact damage.
n Has lifting capability of sufficient power to permit fast retrieval of the Bell, and
controls and brakes that permit precision control for Bell mating and approach
to the seafloor.

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U.S. Navy Diving Manual — Volume 3

n Includes a handling system to move the suspended Bell to and from the launch/
retrieval position to the DDC.
n Has a method of restraining Bell movement during mating to the DDC.
13-3.4

Saturation Mixed-Gas Diving Equipment. The DIVEX SLS MK-4 reclaim system
is a closed circuit, demand-regulated diving helmet designed for saturation, mixedgas diving to depths in excess of 1000 fsw (Figure 13-5). The system employs
a semi-closed circuit backpack with internal HP gas bottles and a C02 scrubber
connected to the helmet used in the event of diver’s primary umbilical failure.

The UBA MK 22 MOD 0 is an open circuit, demand-regulated, band-mask version
of the UBA MK 21 MOD 0 (Figure 13-6). It is used for the standby diver for
saturation, mixed-gas diving at depths as deep as 1000 fsw. It is provided with a
hood and head harness instead of the helmet shell to present a smaller profile for
storage and allow for rapid donning by the standby diver.

Figure 13-5. DIVEX SLS MK-4 Helmet with Backpack.

13-4

Figure 13-6. MK 22 MOD
0 with Hot Water Suit, Hot
Water Shroud, and ComeHome Bottle.

U.S. NAVY SHORE BASED SATURATION FACILITIES
13-4.1

Navy Experimental Diving Unit (NEDU), Panama City, FL. NEDU’s mission is to

test and evaluate diving, hyperbaric, and other life-support systems and procedures,
and to conduct research and development in biomedical and environmental
physiology. NEDU then provides technical recommendations to Commander,
Naval Sea Systems Command to support operational requirements for the U.S.
Armed Forces.
NEDU houses the Ocean Simulation Facility (OSF), one of the world’s largest
man-rated hyperbaric facilities. The OSF consists of five chambers with a wet
pot and transfer trunk. The wet pot holds 55,000 gallons of water. The OSF can

CHAPTER 13 — Saturation Diving

13-7

simulate depths to 2,250 fsw and can accommodate a wide range of experiments in
its dry and wet chambers see (Figure 13-7, Figure 13-8, and Figure 13-9).
13-5

DIVER LIFE-SUPPORT SYSTEMS
13-5.1

Introduction. Saturation diver life-support systems must provide adequate

respiratory and thermal protection to allow work in the water at extreme depths
and temperatures. Because of the increased stresses placed upon the diver by
deep saturation dives, this equipment must be carefully designed and tested in its
operating environment. The diver life-support system consists of two components:
an underwater breathing apparatus (UBA) and a thermal protection system. The
actual in-water time a diver can work effectively depends on the adequacy of his
life-support apparatus and his physical conditioning. Important considerations in
the duration of effective in- water time are the rate of gas consumption for the
system and the degree of thermal protection. Present U.S. Navy saturation diving
UBAs are designed to operate effectively underwater for at least 4 hours. Although
a given diving apparatus may be able to provide longer diver life support,
experience has shown that cumulative dive time at deep depths will progressively
reduce diver effectiveness after a 4-hour in-water exposure.

Figure 13-7. NEDU’s Ocean Simulation Facility (OSF).

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U.S. Navy Diving Manual — Volume 3

Figure 13-8. NEDU’s Ocean Simulation Facility Saturation Diving Chamber Complex.

Figure 13-9. NEDU’s Ocean Simulation Facility Control Room.

CHAPTER 13 — Saturation Diving

13-9

13-6

THERMAL PROTECTION SYSTEM

All saturation diver life-support systems include diver thermal protection consisting
of a hot water suit and a breathing gas heater. The thermal protection is designed
to minimize the diver’s heat loss caused by helium’s high thermal conductivity.
Helium conducts heat away from the body rapidly and causes a significant heat loss
via the diver’s breathing gas. The diver’s metabolic rate may not be great enough to
compensate for the heat loss when breathing cold gas, resulting in a drop in body
temperature and increasing the chance of hypothermia.
13-6.1

Diver Heating. Because of the high thermal conductivity of helium and depths

attained, most conventional diving suits (i.e., wet suits/dry suits) provide inadequate
insulation in a helium environment. As a result, thermal protection garments for
helium-oxygen saturation diving must employ active heating. The most successful
thermal protection currently used is the hot water suit using circulating hot water as
the heat source. The typical hot water suit is constructed from closed-cell, precrushed neoprene with an outer layer of tough canvas-type nylon. The interior
is lined with a softer nylon with perforated hot water hoses along the limbs, chest,
and backbone. Divers are required to wear Polartec Dive skins or Neoprene liners
under their Hot Water suits. The liners or Dive skins offer almost no protection
from cold water. The liners or Dive skins keep the divers from getting burned by
hot water discharge from the hot water suit and minimize chafing of skin.
The effectiveness of the hot water suit in keeping the divers warm is dependent
upon maintaining an adequate flow of water at the proper temperature. A four
gallon per minute (gpm) (3 gpm to the suit and 1 gpm to the back pack) hot water
flow rate with the suit inlet temperature adjusted to diver’s comfort generally
provides adequate protection. During normal operation, hot water is distributed
through the hot water suit and is then discharged to the sea. If there is a diver
heating system failure, the diver returns to the Dive Bell. To prevent burn injury
to the diver, the water temperature at the suit inlet should not exceed 110°F. Hot
water thermal protection systems should be designed to provide individual control
of water temperature and rate of flow supplied to each diver.

13-6.2

Inspired Gas Heating. The thermal protection system includes a breathing-gas

heater to warm the gas to a temperature sufficient to minimize respiratory heat
loss. A typical breathing-gas heater is a hot water heat exchanger that can raise
the breathing-gas temperature by 30–50°F. Breathing cold helium-oxygen at deep
saturation diving depths can cause incapacitating nasal and trachea-bronchial
secretions, breathing difficulties, chest pain, headache, and severe shivering. These
symptoms may begin within minutes of starting the dive excursion. Breathing
apparently comfortable but low-temperature helium-oxygen at deep depths can
rapidly lower body temperature through respiratory heat loss, even though the
skin is kept warm by the hot water suit. The diver usually remains unaware of
respiratory heat loss, has no symptoms, and will not begin to shiver until his
core temperature has fallen. Metabolic heat production may not compensate for
continuing respiratory heat loss. Table 13-1 contains guidelines for the minimum
allowable temperatures for helium-oxygen breathing gas. These limits are based

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U.S. Navy Diving Manual — Volume 3

on a 4-hour excursion with a maximum core body temperature drop of 1.8°F
(1.0°C) in a diver wearing a properly fitted and functioning hot water suit.
Table 13‑1. Guidelines for Minimum Inspired HeO2 Temperatures for Saturation
Depths Between 350 and 1,500 fsw.*
Minimum Inspired Gas Temperature
Depth (fsw)

°C

°F

350

-3.1

26.4

400

1.2

34.2

500

7.5

45.5

600

11.7

53.1

700

14.9

58.8

800

17.3

63.1

900

19.2

66.6

1000

20.7

69.3

1100

22.0

71.6

1200

23.0

73.4

1300

23.9

75.0

1400

24.7

76.5

1500

25.4

77.72

* Ref: C. A. Piantadosi, “Respiratory Heat Loss Limits in Helium Oxygen Saturation Diving,” Navy
Experimental Diving Unit Report NR 10-80 Revised 1982 (ADA 094132).

13-7

SATURATION DIVING UNDERWATER BREATHING APPARATUS

The rate of gas consumption and the composition of the gas supply depend in
part upon the design of the UBA. Three types of underwater breathing apparatus
have been used successfully to support saturation diving operations: demand opencircuit, semi closed-circuit, and closed-circuit.
UBA systems should be designed to support saturation diving excursions of at least
4 hours duration in temperatures as low as 29°F. Specific information on U.S. Navy
certified diving equipment can be found in the applicable system-specific technical
manuals.
The standby divers umbilical should be 10’ longer than the primary diver’s
umbilical.
13-7.1

Commercial Off-the-Shelf Closed-Circuit UBA. The SLS System Diving

Assembly is comprised of the Divex Ultrajewel 601 Reclaim Diving helmet which
has additional interface hoses allowing it to be connected to the SLS System
Backpack.

CHAPTER 13 — Saturation Diving

13-11

The Helmet utilizes a Kirby Morgan Dive Systems Superlite 17C Diving Helmet
which is extensively modified for use in commercial saturation diving operations.
The Diving Support Vessel (DSV) will have a Divex Gasmizer Diver Gas Recovery
System fitted on-board to control the primary breathing gas supply and exhaust to/
from the Helmet.
The Gasmizer System allows the breathing gases supplied to the Helmet to be
recycled and ultimately re-breathed by the diver. This greatly reduces the cost of
the HELIOX gases used during saturation diving operations. Up to 98% of the
exhaled gas can be reclaimed.
Should failure of the diver’s primary gas supply ever occur, the SLS System Helmet
is connected to the SLS System Backpack which is a self-contained, semi-closed
circuit breathing system and will provide the diver with an alternate breathing gas
supply of a minimum of 10 minutes duration, allowing divers to return safely to
the Dive Bell.
13-8

UBA GAS USAGE

Gas usage can be the controlling factor in the planning for a mission and determining
appropriate excursions. However, gas usage is UBA- and platform-specific.
13-8.1

Specific Dives. For a specific dive, storage of gas to support the mission may be
the controlling parameter. The following formulas may be used to calculate gas
usage by divers:

ata =

D + 33
33

scfm (for one diver at depth) = ata × acfm
total scfm = scfm × number of divers
scf required = scfm × minutes
D = depth of diver
ata = atmosphere absolute
acfm = actual cubic feet per minute required by specific UBA being used (refer to
the tech manual)
number of divers = total number of divers making excursion
minutes = duration of excursion
scf required = standard cubic feet of gas required to support the divers

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U.S. Navy Diving Manual — Volume 3

Example. Two divers and one standby diver using open circuit UBAs at 300 fsw

are deployed for a 15-minute excursion. Determine the gas usage.

1. Convert the depth to atmospheres:

300 fsw + 33 fsw
= 10.09 ata
33 fsw
2. Calculate gas usage for 1 diver:

10.09 ata
x 1.4 acfm for MK21 MOD 0
14.13 scfm for 1 divver at 300 fsw
3. Calculate gas usage for 3 divers:

14.13 scfm for 1 diver at 300 fsw
x 3 divers (2) and standbyy (1)
42.39 scfm for 3 divers at 300 fsw
4. Calculate the total gas usage requirement:

42.39 scfm
x 15 minutes excursion time
635.85 scf (round up to 636 scf)
A gas usage requirement of 636 Standard Cubic Feet of helium-oxygen can be
expected for this two-diver excursion.
NOTE

13-8.2

Usage for three divers is computed even though the standby would not
normally be using gas for the entire 15 minutes.
Emergency Gas Supply Duration. The gas computation in paragraph 13-8.1 is used
to determine excursion limits based on diver’s gas storage. The diver’s emergency
gas supply (EGS) duration should also be calculated using the following formulas:

mmp = (D × .445) + psi (obp)
psi available for use = psi (cylinder) - mmp

scf gas available =
scfm = acfm × ata

psi (Available)
x fv
14.7

duration in minutes =

scf
scfm

D = depth of diver

CHAPTER 13 — Saturation Diving

13-13

psi (obp) = over-bottom pressure required for specific UBA
mmp = minimum manifold pressure
fv = floodable volume of cylinder
acfm = actual cubic feet per minute at excursion depth required by specific UBA
being used
scfm = standard cubic feet per minute required to deliver acfm
Example. Using an 80-cubic-foot aluminum cylinder (floodable volume = .399 cu.

ft.) filled to 3,000 psig, calculate the diver’s EGS duration at 300 fsw.

1. Calculate the psi available for use:

185.0 overbottom psi
+ 133.5 psi (300 fsw conveerted to psi)
318.5 psi (round up to 319 psi)
2. Calculate the psig available for use:

3,000 - 319 psig = 2,681 psig available for use
3. Calculate the scf of gas available:

2681
x 0.399 = 72.7 scf of gas available
14.7
4. Calculate the standard cubic feet per minute required:

1.4 acfm × 10.09 ata = 14.13 scfm
5. Calculate the duration of the gas supply:
72.7 scf
= 5.15 minutes
14.13 scfm

The duration of the emergency gas supply is very short, especially at greater depths.
13-8.3

Gas Composition. The percentage of oxygen in the mix depends on diver depth

and can be calculated as follows:

1.

13-14

% decimal equivalent =

ppO 2 desired
ata

U.S. Navy Diving Manual — Volume 3

2. % decimal equivalent × 100 = % of O2 required to maintain desired ppO2
Example. Calculate the minimum and maximum percentage of O2 required to

sustain a .44 to 1.25 ppO2 range at 300 fsw.

1. Calculate the minimum percentage of O2 required to sustain the lower value of

the range:

0.44 ata
= 0.0436 × 100 = 4.36%
10.09 ata
4.36% O2 in He provides the minimum ppO2.
2. Calculate the maximum percentage of O2 required to sustain the upper value of

the range:

1.25 ata
= 0.1239 ×100 = 12.39%
10.09 ata
12.39% O2 in He provides the maximum ppO2.
13-9

SATURATION DIVING OPERATIONS
13-9.1

Introduction. Saturation diving is the mode of choice for diving operations

requiring long bottom times or diving operations deeper than surface-supplied
tables permit. Saturation diving allows divers to remain at working depths without
concern for decompression. The Unlimited Duration Excursion Tables (Table 13-7
and Table 13-8) allow a large vertical range of working depths without time limits.

13-10

OPERATIONAL CONSIDERATIONS

Saturation diving requires complex saturation diving systems designed to
precisely control depth, atmosphere composition, and temperature. Commanding
Officers, Diving Officers, and Master Divers must consider personnel and training
requirements, the physiological stress imposed by depth and dive duration, logistics,
and gas supply requirements. Refer to Table 13-2 for the personnel requirements
for saturation diving.
13-10.1

13-10.2

Dive Team Selection. All candidates for a saturation dive shall be physically
qualified to make the dive as determined by a Saturation Diving Medical Officer.
With the exceptions of authorized research, testing of equipment, or training
purposes, all divers shall be qualified and experienced with the UBA being used
and in the particular dive system to which they are assigned. Depending on
mission requirements, divers may need to have special skills that are required for
the operation.
Mission Training. When the schedule permits, training in preparation for a specific

saturation diving mission shall be conducted. This training provides an opportunity

CHAPTER 13 — Saturation Diving

13-15

to ensure that all personnel are in optimal physical condition and facilitates the
development of special skills required for the operation. Training also provides
an opportunity for individuals to function as a team and to identify an individual
with leadership skills necessary to fill the role of dive team leader. Alternate divers
should be identified and trained with the team in the event of illness or injury to a
primary diver.
13-11

SELECTION OF STORAGE DEPTH

The selection of the storage depth for the deck decompression chamber (DDC) is
based on the approximate planned diver working depth. This can be achieved by
comparing the storage depth and planned diver working depth with the descent and
ascent limits of the Unlimited Duration Excursion Tables (Table 13-7 and Table 138). When the diver’s working depth range is small, the DDC should be compressed
to approximately the middle of the range. This minimizes the amount of gas used
in pressurizing or depressurizing the Dive Bell.
When the expected diver work range is large or multiple objectives at different
depths are to be accomplished, several different storage depths will be required.
The unlimited excursion procedures may be used at several progressively shallower storage depths to accomplish the objective.
Table 13‑2. Typical Saturation Diving Watch Stations.
Watch Station
n Dive Watch Officer

n Communication Technician

n Diving Medical Officer (Note 1)

n Surface-Support Divers

n Master Diver

n Gas King

n Dive Watch Supervisor

n PTC Operators

n Atmosphere Analysis Operator
(AAO)

n PTC Divers

n Chamber Support Operator
(CSO)

n Main Deck Supervisors

n Life-Support Operator
Note:
1.

13-12

A Diving Medical Officer is required to be available in support of all Saturation Diving Operations.
Available is defined as continuously accessible by voice communications and able to be physically
present on the Saturation Diving Watch Station within 30 minutes by available transportation.

RECORDS

This section covers the records required to be maintained during the conduct of a
saturation dive.
13-12.1

Command Diving Log. An official diving log shall be maintained at all times

throughout the dive. It shall contain a chronological record of the dive procedure
in addition to any significant events. A narrative of significant events is to be

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U.S. Navy Diving Manual — Volume 3

recorded by the Diving Officer (or Diving Supervisor) and Saturation Diving
Medical Officer (as necessary). This log shall be retained for 3 years.
13-12.2

Master Protocol. Each diving operation shall have a master protocol submitted

by the Master Diver, reviewed by the Saturation Diving Medical Officer and
Diving Officer, and approved by the Commanding Officer. This master protocol
shall contain all the information needed to ensure that the dive follows a program
consistent with the requirements for saturation diving as defined in this manual
and shall include the necessary information to carry out these procedures on the
specific operational platform.
A copy of the protocol shall be maintained as the master copy at the Main Control
Station. No alterations except those made by the Diving Officer and approved
by the Commanding Officer are permitted. Any changes to this protocol shall be
signed and dated.
13‑12.2.1

Modifications. Because saturation dives generally follow a predictable pattern,

only a few elements of protocol need to be modified from mission to mission.
Consequently, once a complete and carefully written protocol is available, only
minor modifications will be needed to support future missions.

13‑12.2.2

Elements. The dive protocol shall include, but is not limited to, the following:

n A detailed gas-usage plan, including projected gas supply requirements
(paragraph 13-15). The required mixtures for supplying emergency, treatment,
and excursion gas shall be specified for the depth ranges expected with specific
depths to shift mixes indicated.
n A compression schedule, including planned rate of travel with rest stops, if
applicable.
n Manning requirements, including a watchbill.
n Predive and postdive procedures.
13-12.3

Chamber Atmosphere Data Sheet. Hourly readings of chamber pressure,

temperature, humidity, oxygen, and carbon dioxide concentrations shall be
recorded. In addition, time of operation of the carbon dioxide scrubbers and time
of carbon dioxide absorbent replenishment shall be recorded.

13-12.4

13-12.5

Service Lock. The following information shall be recorded: date, depth, clock
time upon leaving the surface or leaving the bottom, and items locked in or out of
the chamber. This information is useful in controlling the spread of contaminants
and in minimizing the combustibles in the chamber while in the fire zone.

A record of the status of all gas banks,
including their pressure and mixture, and of the status of all DDS gas delivery
equipment, shall be maintained. This log shall be reviewed by each oncoming Dive
Machinery Log/Gas Status Report.

CHAPTER 13 — Saturation Diving

13-17

Watch Supervisor prior to assuming
the watch and daily by the Dive Watch
Officer and Master Diver.
13-12.6

Operational

Procedures

(OPs).

Currently
approved
operational
procedure are to be properly completed
and signed by the operator and then
reviewed and signed by the Diving
Supervisor and Dive Watch Officer and
logged in the Command Smooth Log.
13-12.7

13-13

A
set of currently approved emergency
procedures with each individual
watch station’s responsibilities shall
be separately bound and available at
each watch station and in main control
throughout a saturation dive. The
convenience of having emergency
procedures on station does not relieve
Figure 13-10. Dive Bell and LARS
any diver or any saturation diving watch System
team member from being sufficiently
knowledgeable, thoroughly trained, and fully qualified to react efficiently
and instantaneously to any emergency. Constant training in these emergency
procedures is necessary to maintain watch standing proficiency.
Emergency

Procedures

(EPs).

LOGISTICS

In planning an extended diving operation, care must be taken to ensure that sufficient
supplies and power to support a diving mission are available. When operating at
remote sites, the Commanding Officer and Diving Officer must carefully evaluate
the availability of shore-based support. Loss of steam and/or electrical power at sea
is an emergency situation. The loss of either of these vital services to the saturation
dive system with a dive team committed to lengthy decompression constitutes a
major emergency that must be acted upon quickly. Accordingly, transit times and
contingency plans must be made prior to commencing saturation diving operations
at remote sites in case support services for the dive complex are threatened or lost.
13-14

DDC AND DIVE BELL ATMOSPHERE CONTROL

The hyperbaric atmosphere within the DDC and Dive Bell is controlled to maintain
the gaseous components as follows:

13-18

Oxygen Partial Pressure

.44 – .48 ata

Carbon Dioxide Partial Pressure

Less than 0.005 ppCO2 (.5% SEV) (3.8 millimeters of mercury)

Helium and Nitrogen

Balance of total pressure

U.S. Navy Diving Manual — Volume 3

Oxygen levels and time limits are presented in Table 13-3.
These levels, particularly that of oxygen, are essential for safe decompression and
the use of the Unlimited Duration Excursion Tables. Increases in the oxygen partial
pressure above 0.6 ata for extended periods (greater than 24 hours) risk pulmonary
oxygen toxicity and should only be used in emergency situations. A ppO2 below
0.42 ata may result in inadequate decompression, and a ppO2 below 0.16 ata will
result in hypoxia. Once carbon dioxide concentration reaches 0.5 percent surface
equivalent (3.8 millimeters of mercury) for 1 hour, the scrubber canister should be
changed, because carbon dioxide levels tend to rise rapidly thereafter. An inspired
carbon dioxide level of 2 percent surface equivalent (15.2 millimeters of mercury)
can be tolerated for periods of up to 4 hours at depth. Nitrogen concentration
tends to decrease with time at depth, due to purging by helium during service lock
operation.
Table 13‑3. Chamber Oxygen Exposure Time Limits.
Oxygen Level (ata)

Time

Storage

.44 – .48

Unlimited

Excursion

.40 – .60

4 hours (6 hours)***

Excursion associated with
decompression

.42 – .48*

Unlimited

Emergency

.60**

24 hours

Notes:
* This level may be exceeded prior to starting the upward excursion for decompression.
** If oxygen levels exceed this limit, switch to emergency gas.
*** Diver performance exponentially decreases between 4 and 6 hours of an in-water excursion.

NOTE

WARNING

13-15

Discharging UBA gas into the Dive Bell during diving operations may
make it difficult to control the oxygen level.
Dive Bell can see spikes in CO2 well above .5%sev CO2 for short periods
while divers are dressing out for egress. These levels will drop rapidly
once CO2 scrubbers catch up.

GAS SUPPLY REQUIREMENTS

The following gases shall be available for use in a UBA, for emergency supply, and
for the treatment of decompression sickness.
13-15.1

UBA Gas. An adequate quantity of gas within an oxygen partial pressure range of

0.44–1.25 ata shall be available for use.

13-15.2

Emergency Gas. Emergency gas is used as a backup breathing supply in the

event of DDC or Dive Bell atmosphere contamination. An emergency gas with
an oxygen partial pressure of 0.16 to 1.25 ata shall be immediately available to
the built- in breathing system (BIBS). The volume of emergency breathing gas

CHAPTER 13 — Saturation Diving

13-19

shall be sufficient to supply the divers for the time needed to correct the DDC
atmosphere.
Upward excursions of the Dive Bell or DDC or decompression shall not be started
during emergency gas breathing unless the oxygen partial pressure of the diver’s
inspired gas is 0.42 ata or above.
Example. An emergency gas schedule for a dive to 850 fsw is:

13-15.3

Bank Mix

Allowable Depth Range (fsw)

Shift Depth (fsw)

#1 84/16 HeO2

0–224

200

#2 96/4 HeO2

99–998

Treatment Gases. Treatment gases having an oxygen partial pressure range of 1.5

to 2.8 shall be available in the event of decompression sickness. The premixed
gases shown in Table 13-4 may be used over the depth range of 0 – 1,600 fsw. A
source of treatment gas shall be available as soon as treatment depth is reached.
The source shall be able to supply a sufficient volume of breathing gas to treat
each chamber occupant.

Table 13‑4. Treatment Gases.

13-16

Depth (fsw)

Mix

0–60

100% O2

60–100

40/60% HeO2

100–200

64/36% HeO2

200–350

79/21% HeO2

350–600

87/13% HeO2

600–1000

92/08% HeO2

1000–1600

95/05% HeO2

ENVIRONMENTAL CONTROL

Helium-oxygen gas mixtures conduct heat away from the diver very rapidly. As a
result, temperatures higher than those required in an air environment are necessary
to keep a diver comfortable. As depth increases, the temperature necessary to
achieve comfort may increase to the 85–93°F range.
As a general guideline to achieve optimum comfort for all divers, the temperature
should be kept low enough for the warmest diver to be comfortable. Cooler divers
can add clothing as needed. All divers should be questioned frequently about their
comfort.

13-20

U.S. Navy Diving Manual — Volume 3

The relative humidity should be maintained between 30 and 80 percent with 50
to 70 percent being the most desirable range for diver comfort, carbon dioxide
scrubber performance, and fire protection.
13-17

FIRE ZONE CONSIDERATIONS

Every effort shall be made to eliminate any fire hazard within a chamber. When
oxygen percentages are elevated as during the later stages of decompression, a
fire will burn rapidly once started, perhaps uncontrollably. As a result, special
precautions are necessary to protect the diver’s safety when in the fire zone. The
fire zone is where the oxygen concentration in the chamber is 6 percent or greater.
Using standard saturation diving procedures (oxygen partial pressure between 0.44
and 0.48 ata), fire is possible at depths less than 231 fsw. Thus, during a saturation
dive the divers will be in the fire zone during initial compression to depth and
during the final stages of decompression.
Example. The chamber atmosphere is 0.48 ata ppO2. The minimum oxygen

percentage for combustion is 6 percent. Compute the fire zone depth.
The fire zone depth is computed as follows:

Although the design of the DDS minimizes fire potential, personnel must
remain vigilant at all times to prevent fires. Appropriate precautions for fire
prevention include:
n Fire-suppression systems, if available, must be operational at all times when in
the fire zone.
n Chamber clothing, bed linen, and towels shall be made of 100% cotton. Diver
swim trunks made of a 65% polyester–35% cotton material is acceptable.
n Mattresses and pillows shall be made of fire-retardant material when in the fire
zone.
n Limit combustible personal effects to essential items.
n Limit reading material, notebooks, etc., in the fire zone.
n All potential combustibles shall be locked in only with the permission of the
Diving Supervisor.

CHAPTER 13 — Saturation Diving

13-21

n Whenever possible, stow all combustibles, including trash, in fire-retardant
containers, and lock out trash as soon as possible.
n Being thoroughly familiar with all emergency procedures (EPs) regarding fire
inside and outside the Deep Diving System.
13-18

HYGIENE

Once a saturation dive begins, any illness that develops is likely to affect the entire
team, reducing their efficiency and perhaps requiring the dive to be aborted. To
minimize this possibility, the Saturation Diving Medical Officer should conduct a
brief review of the diver’s physical condition within 24 hours of compression. If
an infectious process or illness is suspected, it shall be carefully evaluated by the
Saturation Diving Medical Officer for possible replacement of the diver with a
previously designated alternate diver. Strict attention to personal hygiene, chamber
cleanliness, and food-handling procedures should be maintained once the dive
begins to minimize the development and spread of infection.
13-18.1

Personal Hygiene. Personal hygiene and cleanliness is the most important factor in

preventing infections, especially skin and ear infections. All divers should wash at
least daily, and as soon as possible after wet excursions. Fresh linens and clothing
should be locked into the complex every day. To prevent foot injury, clean, dry
footwear should be worn at all times except while showering, sleeping, or in diving
dress. Feet must be thoroughly dry, especially between the toes, to minimize local
infections. A personal toiletry bag shall be maintained by each chamber occupant.
These bags shall be inspected by the Dive Watch Supervisor or Dive Watch Officer
prior to commencing the dive to prevent potential contaminants or fire hazards
from being carried into the chamber.

13-18.2

Prevention of External Ear Infections. Severe ear infections can develop unless
preventative measures are taken. An effective preventative regime includes
irrigating each ear with 2 percent acetic acid in aluminum acetate solution (i.e.,
DOMEBORO) for 5 minutes once each day. Irrigation shall be observed by the
Diving Supervisor, timed by the clock, and logged.

After a week or so, even with the ear prophylaxis regimen, the ear canals may
become occluded with debris. Once this happens, an ear infection may develop
rapidly. In order to prevent this occurrence, all divers should be trained to detect and
treat blockage. Before beginning a dive, all divers should be trained by qualified
medical personnel to use an otoscope to view the ear drum. Also, they should be
trained to use an ear syringe. At least weekly during a dive, divers should examine
each other’s ear canals. If the ear drum cannot be viewed because of a blockage,
then the canal should be gently irrigated with the ear syringe until the canal is
unplugged.
13-18.3

13-22

Chamber Cleanliness. Strict attention shall be paid to chamber cleanliness at
all times, particularly in the area of the toilet, wash basin, shower, and service
locks. Only approved compounds shall be used to clean the chamber, components,
and clothing used in the pressurized environment. During wet excursions, close

U.S. Navy Diving Manual — Volume 3

attention shall be paid to routine postdive cleaning of the diver-worn equipment to
prevent rashes and skin infections.
Upon completing a saturation dive, the chamber should be well ventilated, emptied,
and liberally washed down with non-ionic detergent (MIL-D-16791) and water
and then closed. Additionally, all chamber bedding, linens, and clothing shall be
washed.
13-18.4

13-19

Food Preparation and Handling. All food provided to the divers during a saturation
diving evolution should be inspected by the Dive Watch Supervisor.

ATMOSPHERE QUALITY CONTROL

Preventing chamber atmosphere contamination by toxic gases is extremely
important to the health of the divers. Once introduced into the chambers, gaseous
contaminants are difficult to remove and may result in prolonged diver exposure.
13-19.1

Gaseous Contaminants. Gaseous contaminants can be introduced into the

chamber through a contaminated gas supply, through chamber piping and/or gas
flasks containing residual lubricants or solvents, or by the divers or maintenance
personnel.
The hazard of atmospheric contamination can be reduced by ensuring that only gases
that meet the appropriate federal specifications are used and that appropriate gas
transfer procedures are used. All gas flasks and chamber piping used with helium,
oxygen, or mixed gases shall be cleaned using approved cleaning procedures to
remove substances that may become chamber contaminants. Once cleaned, care
shall be taken to prevent introduction of contaminants back into these systems
during maintenance by marking and bagging openings into the piping system.
Finally, inadvertent chamber contamination can be prevented by limiting the
items that may be taken inside. Only approved paints, lubricants, solvents, glues,
equipment, and other materials known not to off-gas potential toxic contaminants
are allowed in the chamber. Strict control of all substances entering the chamber is
an essential element in preventing chamber contamination.

13-19.2

Initial Unmanned Screening Procedures. To ensure that chamber systems are
free of gaseous contaminants, the chamber atmosphere shall be screened for
the presence of the common contaminants found in hyperbaric systems when
contamination of the chamber and/or gas supply is suspected, or after any major
chamber repair or overhaul has been completed. Only NAVFAC or NAVSEA
approved procedures may be used to collect screening samples.

Table 13-5 lists a few selected contaminants that may be present in hyperbaric
complexes, with their 90-day continuous exposure limits (or 7-day limits where a
90-day limit is not available). In the absence of specific guidelines for hyperbaric
exposures, these limits shall be used as safe limits for saturation diving systems.
When any one of these contaminants is reported in chamber samples, the calculated
Surface Equivalent Value (SEV) shall be compared to the limit on this list. If the

CHAPTER 13 — Saturation Diving

13-23

calculated SEV exceeds this limit, the chamber shall be cleaned and retested.
Assistance with any contamination identification and resolution can be obtained by
contacting NEDU or the system certification authority for guidance.
Table 13‑5. Limits for Selected Gaseous Contaminants in Saturation Diving Systems.
Contaminant

Limit

Acetone

200 ppm (Note 1) (Note 3: Same limit)

Benzene

1 ppm (Note 3)

Chloroform

1 ppm (Note 1)

Ethanol

100 ppm (Note 3)

Freon 113

100 ppm (Note 1)

Freon 11

100 ppm (Note 1)

Freon 12

100 ppm (Note 1) (Note 3: Same limit)

Freon 114

100 ppm (Note 1)

Isopropyl Alcohol

1 ppm (Note 1)

Methanol

10 ppm (Note 3)

Methyl Chloroform

30 ppm (Note 2) (Note 3: 90-day limit =
2.5 ppm, 24-hour limit = 10 ppm)

Methyl Ethyl Ketone

20 ppm (Note 2)

Methyl Isobutyl Ketone

20 ppm (Note 2)

Methylene Chloride

25 ppm (Note 2)

Toulene

20 ppm (Note 1) (Note 3: Same limit)

Trimethyl Benzenes

3 ppm (Note 2)

Xylenes

50 ppm (Note 1) (Note 3: Same limit)

Notes:

13-20

1.

90-day continuous exposure limit. National Research Council Committee on Toxicology
Emergency and Continuous Exposure Limits for Selected Airborne Contaminants, Vols.
1-8, Washington, D.C., National Academy Press, 1984–1988.

2.

7-day maximum allowable concentration in manned spacecraft. National Aeronautics and
Space Administration, Office of Space Transportation Systems. Flammability, Odor, and
Offgassing Requirements and Test Procedures for Materials in Environments that Support
Combustion, NHB 8060, 1B, Washington, D.C., U.S. Government Printing Office, 1981.

3.

90-day limit. U.S. Naval Sea Systems Command Nuclear Powered Submarine Atmosphere
Control Manual, NAVSEA S9510-AB-ATM-010 (U), Vol. 1, Revision 2, 30 July 1992.

COMPRESSION PHASE

The initial phase of the dive is the compression of the dive team to the selected
storage depth. This phase includes establishing the chamber oxygen partial pressure
at a value between 0.44 and 0.48 ata, instrument and systems checkouts, and the
actual compression of the divers to storage depth.

13-24

U.S. Navy Diving Manual — Volume 3

13-20.1

Establishing Chamber Oxygen Partial Pressure. Prior to compression to storage

depth, the chamber oxygen partial pressure should be raised from 0.21 ata to
0.44–0.48 ata. There are two methods of raising the oxygen partial pressure to the
desired level.
n Air Method. Compress the chamber with air at a moderate rate to 36 fsw. This
will raise the chamber ppO2 to 0.44 ata. If desired, further elevation of the
chamber ppO2 system.
n Helium-Oxygen Method. Compress the chamber at a moderate rate with a
helium-oxygen mixture containing less than 21 percent oxygen. There are 3
methods that can be utilized depending on the oxygen content of the heliumoxygen mixture:

Method 1: Compress the chamber with helium-oxygen mixture to an intermediate

depth at which a ppO2 of 0.44-0.48 ata is achieved. Complete compressions to
storage depth with 100% helium. The intermediate depth can be calculated with the
equation below.

Intermediate Compression Depth (fsw) = 33 x (ppO2 - 0.21)
Oc

Where:
ppO2 = desired chamber ppO2

Oc = Oxygen % (decimal form) of compression gas
If a 20 percent mixture of helium-oxygen is used and the desired ppO2
is 0.44 ata, calculate the intermediate compression depth.
Example.

Intermediate Compression Depth (fsw) = 33 x (0.44 - 0.21)
0.20
= 37.95 fsw
Method 2: When the oxygen content is too low to reach 0.44-0.48 ata prior to

reaching storage depth, compress the chamber with air to an intermediate depth
to establish an intermediate ppO2. Complete compression to storage depth with
helium-oxygen mixture to achieve a final ppO2 of 0.44-0.48 ata. The intermediate
depth is dependent on the desired storage depth and the oxygen content of heliumoxygen mixture. Calculations are below.

P1 =

CHAPTER 13 — Saturation Diving

ppO2 - (P2xOc )
(0.21-Oc )

13-25

Where:
P1 = Chamber pressure at intermediate depth (ata)
P2 = Chamber pressure at storage depth (ata)
Oc = Oxygen % (decimal form) of compression gas
ppO2 = desired chamber ppO2
A saturation dive is planned for final storage depth of 198 fsw. What is
the intermediate depth to which one must compress on air to achieve a final ppO2
of 0.46 ata when the ensuing compression to the 198 fsw storage depth is to be
completed with a 98% helium/2% oxygen mixture?
Example.

 Depth   198 
+ 1 = 7 ata
+ 1 = 
Chamber Pressure at storage depth = 

 33
  33

P1 =

ppO2 - (P2xOc )
(0.21-Oc )

=

0.46-7x0.02
0.21-0.02

= 1.68ata

Then convert to depth (fsw):
Intermediate Depth = (P1-1)x33 = (1.68-1)x33 = 22.6 fsw
Method 3: Alternatively, when the oxygen content is too low to reach 0.44-0.48

ata prior to reaching storage depth, compress the chamber from the surface to
storage depth with the helium-oxygen mixture. Then add 100% oxygen to increase
the ppO2 to an acceptable range.
CAUTION:

13-20.2

During compression ensure an adequate ppO2 (0.16 - 1.25 ata) is
maintained. Be prepared to don BIBS or slow travel rates as required.
Compression to Storage Depth. Rapid compression to saturation storage depth

may provoke symptoms of High-Pressure Nervous Syndrome (HPNS) and may
intensify compression joint pains. To avoid these complications, the slowest rate
of compression consistent with operational requirements should be used. Table
13-6 shows the range of allowable compression rates.

Table 13‑6. Saturation Diving Compression Rates.

13-26

Depth Range

Compression Rate

0 – 60 fsw

0.5 – 30 fsw/min

60 – 250 fsw

0.5 – 10 fsw/min

250 – 750 fsw

0.5 – 3 fsw/min

750 – 1000 fsw

0.5 – 2 fsw/min

U.S. Navy Diving Manual — Volume 3

If operational necessity dictates, compression to storage depth of 400 fsw or shallower can be made at the maximum rates indicated in Table 13-6 with little risk of
HPNS. Direct compression at maximum rates to deeper storage depths, however,
may produce symptoms of HPNS in some divers. These divers may be unable to
perform effectively for a period of 24 to 48 hours. Experience has shown that the
appearance of such symptoms can be minimized by slowing compression rates or
introducing holds during compression.
The depth and time duration of holds, if used, may be adjusted to suit operational
requirements and diver comfort.
13-20.3

13-20.4

Precautions During Compression. During compression the chamber atmosphere
shall be monitored carefully. The chamber atmosphere may not mix well during
rapid compression, resulting in areas of low oxygen concentration.
Abort Procedures During Compression. The following abort procedure is

authorized if a casualty occurs during compression. Consult with a Saturation
Diving Medical Officer prior to committing to this procedure. This procedure is
normally used for shallow aborts where the maximum depth and bottom time do
not exceed the limits of the table.
Using the Surface Supplied HeO2 Tables, the following procedure applies:

n Depth. Use the actual chamber depth.
n Bottom Time. If the initial compression uses air, time spent shallower than
40 fsw, up to a maximum of 60 minutes, is not counted as bottom time. If the
initial compression uses helium, time starts when leaving the surface.
n BIBS Gas. Maintain BIBS between 1.5 – 2.8 ppO2.
n Stops. Follow the scheduled stops of the Surface Supplied HeO2 Tables.
n 02 Breaks. For every 25 minutes of breathing BIBS gas, take a 5-minute break
breathing a gas between 0.16 to 1.25 ata ppO2. The 5-minute break counts as a
stop time. The lower oxygen percentage shall not be less than 0.16 ata ppO2.
Upon completing abort decompression, all divers shall be closely monitored and
observed for a minimum of 24 hours. For deeper emergency aborts beyond the
limits of the surface-supplied HeO2 Tables, refer to paragraph 13-23.7.2.
13-21

STORAGE DEPTH

The Unlimited Duration Excursion Tables (Table 13-7 and Table 13-8) allow
multiple diver excursions to be conducted during the course of a saturation dive.
When using these excursion procedures, the diving supervisor need only be
concerned with the depth of the divers. To use these tables when planning the dive,
select a chamber storage depth in a range that allows diver excursions shallower or

CHAPTER 13 — Saturation Diving

13-27

deeper than the storage depth. The actual depth of the work site or Dive Bell may
be significantly different from the storage depth.
When using Table 13-8, enter the table at the deepest depth attained at any time
within the last 48 hours. While the DDC may be at 400 fsw, if one diver had
reached a depth of 460 fsw during an in-water excursion, the maximum upward
excursion depth for the divers is 360 fsw instead of 307 fsw. After completing
work at one depth and then compressing DDC to a deeper storage depth, unlimited
downward or upward excursions are permitted immediately upon reaching the new
storage depth. When decompressing the DDC from a deeper depth using standard
saturation decompression procedures, unlimited downward excursions, as defined
in Table 13-7, may begin immediately upon reaching the new chamber storage
depth. A minimum of 48 hours shall elapse at the new storage depth before any
upward excursions may be made.

Figure 13-11. Inside Dive Bell.

13-28

U.S. Navy Diving Manual — Volume 3

Table 13‑7. Unlimited Duration Downward Excursion Limits.
Storage
Depth (fsw)

Deepest
Excursion
Distance (ft)

Deepest
Excursion
Depth (fsw)

0
10
20
30
40
50
60
70
80
90
100
110
120
130
140
150
160
170
180
190
200
210
220
230
240
250
260
270
280
290
300
310
320
330
340
350
360
370
380
390
400

29
33
37
40
43
46
48
51
53
56
58
60
62
64
66
68
70
72
73
75
77
78
80
82
83
85
86
88
89
90
92
93
95
96
97
98
100
101
102
103
105

29
43
57
70
83
96
108
121
133
146
158
170
182
194
206
218
230
242
253
265
277
288
300
312
323
335
346
358
369
380
392
403
415
426
437
448
460
471
482
493
505

CHAPTER 13 — Saturation Diving

Storage
Depth (fsw)

Deepest
Excursion
Distance (ft)

410
420
430
440
450
460
470
480
490
500
510
520
530
540
550
560
570
580
590
600
610
620
630
640
650
660
670
680
690
700
710
720
730
740
750
760
770
780
790
800
810
820
830
840
850

106
107
108
109
111
112
113
114
115
116
117
118
119
120
122
123
124
125
126
127
128
129
130
131
132
133
133
134
135
136
137
138
139
140
141
142
143
144
144
145
146
147
148
149
150

Deepest
Excursion
Depth (fsw)
516
527
538
549
561
572
583
594
605
616
627
638
649
660
672
683
694
705
716
727
738
749
760
771
782
793
803
814
825
836
847
858
869
880
891
902
913
924
934
945
956
967
978
989
1000

13-29

Table 13‑8. Unlimited Duration Upward Excursion Limits.
Storage
Depth (fsw)

Shallowest
Excursion
Distance (ft)

Shallowest
Excursion
Depth (fsw)

29
30
40
50
60
70
80
90
100
110
120
130
140
150
160
170
180
190
200
210
220
230
240
250
260
270
280
290
300
310
320
330
340
350
360
370
380
390
400
410
420
430
440
450
460
470
480
490
500

29
29
32
35
37
40
42
44
47
49
51
53
55
56
58
60
62
63
65
67
68
70
71
73
74
76
77
79
80
81
83
84
85
87
88
89
90
92
93
94
95
96
97
99
100
101
102
103
104

0
1
8
15
23
30
38
46
53
61
69
77
85
94
102
110
118
127
135
143
152
160
169
177
186
194
203
211
220
229
237
246
255
263
272
281
290
298
307
316
325
334
343
351
360
369
378
387
396

13-30

Storage
Depth (fsw)
510
520
530
540
550
560
570
580
590
600
610
620
630
640
650
660
670
680
690
700
710
720
730
740
750
760
770
780
790
800
810
820
830
840
850
860
870
880
890
900
910
920
730
940
950
960
970
980
990
1000

Shallowest
Excursion
Distance (ft)

Shallowest
Excursion
Depth (fsw)

105
106
107
108
110
111
112
113
114
115
116
117
118
119
119
120
121
122
123
124
125
126
127
128
129
130
131
131
132
133
134
135
136
137
137
138
139
140
141
142
142
143
144
145
146
146
147
148
149
150

405
414
423
432
440
449
458
467
476
485
494
503
512
521
531
540
549
558
567
576
585
594
603
612
621
630
639
649
658
667
676
685
694
703
713
722
731
740
749
758
768
777
786
795
804
814
823
832
841
850

U.S. Navy Diving Manual — Volume 3

Example. After decompression from 1,000 fsw to 400 fsw, the maximum downward

excursion is 105 fsw. After 48 hours have elapsed at 400 fsw, a full upward excursion
of 93 fsw to 307 fsw is permitted.

If less than 48 hours is spent at the new storage depth, the maximum upward
excursion is based on the deepest depth attained in the preceding 48 hours.
Example. Decompression from a 1,000 fsw dive has been conducted to the 400 fsw
depth. Twenty-four hours have been spent at 400 fsw. The dive log shows that the
deepest depth attained in the preceding 48 hours is 496 fsw. The maximum upward
excursion from Table 13-8, based on a 496 fsw depth, is to 396 fsw (500 – 104)
allowing a maximum of a 4 fsw upward excursion. After 36 hours have elapsed
at 400 fsw, the dive log shows that the deepest depth attained in the preceding 48
hours was 448 fsw. From Table 13-8, the shallowest excursion depth is now 351
fsw.

The ascent rate should not exceed 60 fsw/min during an excursion. When it is
detected that a diver is ascending faster than 60 fsw/min, the diver shall immediately
stop and wait until enough time has elapsed to return to the 60 fsw/min schedule.
The diver may then resume ascent at a rate not to exceed 60 fsw/min from that
depth.
If storage depth falls between the depths listed in Table 13-7, use the next shallower
depth (e.g., if the storage depth is 295 fsw, enter Table 13-7 at 290 fsw). If storage
depth falls between the depths listed in Table 13-8, use the next deeper depth (e.g.,
if the storage depth is 295 fsw, enter Table 13-8 at 300 fsw).
13-21.1

Excursion Table Examples.
Example 1. The chamber was compressed to 400 fsw from the surface. The initial
depth in Table 13-7 is 400 fsw. The maximum downward excursion for an unlimited
period not requiring decompression is 105 fsw, allowing a maximum diver depth
of 505 fsw. If the diver descends to 450 fsw, the maximum depth achieved from
the 400 fsw storage depth will be 450 fsw. Table 13-8 at 450 fsw allows a 99
fsw upward excursion to a depth of 351 fsw. Thus, these divers may move freely
between the depths of 351 and 450 fsw while at a storage depth of 400 fsw.
Example 2. At a storage depth of 600 fsw, during which dives were made to

650 fsw, the maximum upward excursion that may by made to begin saturation
decompression is:
n If less than 48 hours have elapsed since the 650 fsw excursion, Table 13-8
allows a maximum upward excursion of 119 fsw from a deepest depth of 650
fsw to a depth of 531 fsw.
n If more than 48 hours have elapsed since the excursion, the maximum upward
excursion allowed is 115 fsw from 600 fsw to 485 fsw.

CHAPTER 13 — Saturation Diving

13-31

Example 3. At the new shallower storage depth of 350 fsw, divers conduct an

excursion to 400 fsw. Using the deepest depth of 400 fsw achieved during storage
at 350 fsw, a maximum upward ascent from Table 13-8 of 93 fsw to a depth of 307
fsw is allowed, provided the chamber and the divers have been at the storage depth
of 350 fsw for at least 48 hours. Otherwise, no upward excursion is permitted.
13-21.2

13‑21.2.1

Dive Bell Diving Procedures. Actual Dive Bell diving operations are dictated
by the Unit’s operating instructions. In conducting these operations, experience
indicates that a maximum in-water time of 4 hours is optimal for diver efficiency.
Longer dive times result in a loss of diver effectiveness because of fatigue and
exposure, while shorter dives will significantly increase the time at depth for the
completion of operations. Standard practice is to rotate in-water divers with the
Dive Bell operators, allowing two 4-hour dives to be conducted during a single
Dive Bell excursion to the work site. Proper positioning of the Dive Bell near the
objective is important in ensuring that the diver does not exceed the maximum
permitted excursion limits (Figure 13-12).
Dive Bell Deployment Procedures. A brief overview of Dive Bell deployment

procedures follows:

1. For initial pressurization, the Dive Bell, with internal hatch open, is usually

mated to the DDC. Divers enter the DDC and secure the hatches.

2. The DDC and Dive Bell are pressurized to bottom depth. The divers transfer

to the Personnel Transfer Capsule (PTC) and secure the DDC and Dive Bell
hatches after them.

3. The trunk space is vented to the atmosphere and then the Dive Bell is deployed

and lowered to working depth. The hatch is opened when seawater and internal
Dive Bell pressures are equal. The divers don diving equipment and deploy
from the Dive Bell.

4. Divers return to the Dive Bell and secure the hatch. The Dive Bell is raised

and mated to the DDC, and the divers transfer to the DDC. Until they are
decompressed in the DDC, the divers rotate between periods of living in
the DDC and working on the bottom. Deep underwater projects requiring
moderate bottom time or diver activities involving work at various depths
are conducted in the saturation mode with excursion dives. The Dive Bell
and DDC are pressurized to a storage depth within the ascent and descent
limits of the Unlimited Duration Excursion Tables (Table 13-7 and Table
13-8), maximizing diving efficiency for deep, long dives. Once tissue
saturation is reached, decompression requirements no longer increase.

13-32

U.S. Navy Diving Manual — Volume 3

220’

Diver in
Blowup

Diver in
Blowup

Shallowest Excursion
Depth Permissible

Case 3
Working Area Limited by
Umbilical Least Desirable

300’

Shallowest Excursion Distance 80 Feet

Diver in
Blowup
Diver’s
80 Foot
Umbilical

Diver’s
80 Foot
Umbilical

Case 2
Working Area Limited
by Umbilical

Diver’s
40 Foot
Umbilical

Case 1
Working Area of 80-Foot
Radius Most Desirable

Excursion Depth

Figure 13‑12. PTC Placement Relative to Excursion Limits.

13-22

DEEP DIVING SYSTEM (DDS) EMERGENCY PROCEDURES

Major DDS emergencies include loss of atmosphere control, loss of depth control
and fire in the DDC. Emergencies will be covered by locally prepared and NAVSEAor NAVFAC-approved emergency procedures. The following are guidelines for
establishing these procedures.

CHAPTER 13 — Saturation Diving

13-33

13-22.1

Loss of Chamber Atmosphere Control. Loss of chamber atmosphere control

includes loss of oxygen control, high carbon dioxide level, chamber atmosphere
contamination and loss of temperature control.

13‑22.1.1

13‑22.1.2

Loss of Oxygen Control. Divers can be safely exposed to chamber oxygen partial
pressures between 0.16 and 1.25 ata; however, efforts should be implemented
immediately to correct the problem and reestablish normal oxygen levels. For an
oxygen partial pressure from 0.16 to 0.48 ata, the normal oxygen addition system
can be used to increase the oxygen level slowly over time. For an oxygen partial
pressure above 0.48, it may be necessary to secure the oxygen addition system and
allow the divers to breathe down the chamber oxygen to a normal level. Table 13-3
lists the chamber oxygen exposure time limits. If these limits are exceeded, the
divers should be placed on BIBS and the chamber ventilated to reduce the oxygen
level.
Loss of Carbon Dioxide Control. When the DDC’s life-support system loses its

ability to absorb carbon dioxide, the level of carbon dioxide within the chamber
will rise at a rate depending on the chamber size and the combined carbon dioxide
production rate of the divers. An increasing carbon dioxide level may be the result
of exhaustion of the carbon dioxide absorbent or inadequate gas flow through the
carbon dioxide absorbent canister. If, after the carbon dioxide absorbent canister
is changed, chamber carbon dioxide level still cannot be brought under 0.005 ata
(3.8 mmhg), the flow through the canister may be inadequate. Divers shall don
BIBS when the chamber carbon dioxide level exceeds 0.06 ata (45.6 mmhg).

13‑22.1.3

13‑22.1.4

Atmosphere Contamination. If an abnormal odor is detected or if several divers
report symptoms of eye or lung irritation, coughing, headache, or impaired
performance, contamination of the chamber atmosphere should be suspected. The
divers shall be placed on BIBS and emergency procedures executed. The divers
should be isolated in the part of the complex thought to be least contaminated.
Test the chamber atmosphere by collecting a gas sample for analysis on the
surface, as described in paragraph 13-19.2. If atmosphere contamination is found,
the divers should be moved to the chamber or Dive Bell with the least level of
contamination and this chamber isolated from the rest of the complex.
Interpretation of the Analysis. The allowable contaminant limits within a diving

system are based upon the Threshold Limit Values (TLV) for Chemical Substances
and Physical Agents guidelines published by the American Conference of
Governmental Industrial Hygienists (ACGIH). TLVs are the time-weighted average
concentration for an 8-hour work day and a 40-hour work week, to which nearly
all workers can be repeatedly exposed day after day without adverse effect. These
guidelines are published yearly and should be used to determine acceptability.
Because the partial pressure of a gas generally causes its physiological effects,
the published limits must be corrected for the expected maximum operating depth
(ata) of the diving system.
The solution to an atmosphere contamination problem centers around identifying
the source of contamination and correcting it. Gas samples from suspected sources

13-34

U.S. Navy Diving Manual — Volume 3

must be checked for contaminants. Special attention should be given to recently
changed and cleaned piping sections, gas hoses, and diver umbilicals, any of which
may contain residual cleaning solvents. Surfaced chambers should be thoroughly
ventilated with air or a breathable helium-oxygen mixture (to prevent hypoxia
in maintenance personnel), inspected, and thoroughly scrubbed down to remove
residual contaminants. These chambers can then be compressed to depth using a
gas bank that is free of contaminants, the divers can be transferred to this chamber,
and the surface cleaning process can be repeated on the remaining chamber(s). After
cleaning and compression to depth, the chamber should be checked periodically for
recurrence of the contamination.
13‑22.1.5

Loss of Temperature Control. Loss of temperature control of more than 2–3°F

above or below the comfort level may lead to severe thermal stress in the divers.
Studies have shown that heat loss by perspiring is less effective in a hyperbaric
atmosphere. Heating a chamber to warm up cold divers may result in the divers
rapidly becoming overheated. Heat stroke may then become a possibility. The
potential for uncontrolled chamber heating occurs when chambers and Dive Bells
are exposed to direct sunlight.
When the chamber temperature falls, the divers begin intense shivering and
hypothermia develops unless rapid and aggressive measures are taken to correct the
problem. Divers may be provided with insulated clothing, blankets, and sleeping
bags. The best of these insulators are of limited effectiveness within the heliumoxygen environment and will provide marginal protection until the problem can
be corrected. Special thermal protection systems have been designed for the use
within DDCs. These systems include thermal protection garments, insulating deck
pads or hammocks, and combination carbon dioxide absorbent and respiratoryheat regenerator systems.

13-22.2

Loss of Depth Control. Loss of depth control is defined as a pressure loss or gain

that cannot be controlled within the normal capabilities of the system. When loss
of depth control is encountered, all deployed divers shall be recovered immediately
and all divers placed on BIBS. Attempt to control depth by exhausting excess
gas or adding helium to minimize depth loss until the cause can be found and
corrected. If the depth change is in excess of that allowed by the Unlimited
Duration Excursion Tables, the divers should be returned to the original storage
depth immediately and the Diving Medical Officer notified.
13-22.3

Fire in the DDC. Because fire within a DDC may progress rapidly, the divers and

watchstanders must immediately activate the fire suppression system and secure
the oxygen system as soon as a fire is suspected. When the fire suppression system
is activated, all divers shall immediately go on BIBS. Watchstanders should
monitor depth carefully because an extensive fire will cause an increase in depth.
If the fire suppression system fails to extinguish the fire, rapid compression of the
chamber with helium may extinguish the fire, in that helium lowers the oxygen
concentration and promotes heat transfer. After the fire is extinguished, chamber
atmosphere contaminant emergency procedures shall be followed.

CHAPTER 13 — Saturation Diving

13-35

13-22.4

Dive Bell Emergencies. Dive Bell emergencies, like DDC emergencies, require

specific, timely, and uniform responses in order to prevent injury or casualty to
divers, watchstanders, and equipment.
13-23

SATURATION DECOMPRESSION

Saturation decompression may be initiated by an upward excursion as long as the
excursion remains within the limits permitted by the Unlimited Duration Excursion
Tables. The alternative is to begin travel at the appropriate decompression rate
without the upward excursion. Decompression travel rates are found on Table 13-9.
Table 13‑9. Saturation Decompression Rates.

13-23.1

13-23.2

13-23.3

13-23.4

13-23.5

13-36

Depth

Rate

1,600 – 200 fsw

6 feet per hour

200 – 100 fsw

5 feet per hour

100 – 50 fsw

4 feet per hour

50 – 0 fsw

3 feet per hour

Upward Excursion Depth. The minimum depth to which the upward excursion
may be made is found by entering Table 13-8 with the deepest depth attained by
any diver in the preceding 48 hours. The total upward excursion actually chosen is
determined by the Dive Watch Supervisor and Dive Watch Officer, and approved
by the Commanding Officer, taking into consideration environmental factors, the
diver’s workload, and the diver’s physical condition.
Travel Rate. The travel rate for the upward excursion is 2 fsw/min. Beginning
decompression with an upward excursion will save considerable time and may be
used whenever practical.

Due to the increased risk of decompression sickness
following an upward excursion for dives with a storage depth of 200 fsw or less, a
2-hour post-excursion hold should be utilized. The 2-hour hold begins upon arrival
at upward excursion depth.

Post-Excursion Hold.

Rest Stops. During decompression, traveling stops for a total of 8 hours out of
every 24 hours. The 8 hours should be divided into at least two periods known
as “Rest Stops.” At what hours these rest stops occur are determined by the
daily routine and operations schedule. The 2-hour post-excursion hold may be
considered as one of the rest stops.
Saturation Decompression Rates. Table 13-9 shows saturation decompression
rates. Saturation decompression is executed by decompressing the DDC in 1foot increments not to exceed 1 fsw per minute. For example, using a travel rate
of 6 feet per hour will decompress the chamber 1 foot every 10 minutes. The
last decompression stop before surfacing may be taken at 4 fsw to ensure early
surfacing does not occur and that gas flow to atmosphere monitoring instruments

U.S. Navy Diving Manual — Volume 3

remains adequate. This last stop would be 80 minutes, followed by direct ascent to
the surface at 1 fsw/min.
Traveling is conducted for 16 hours in each 24-hour period. A 16-hour daily travel/
rest outline example consistent with a normal day/night cycle is:
Daily Routine Schedule
2400–0600
Rest Stop
0600–1400
Travel
1400–1600
Rest Stop
1600–2400
Travel
This schedule minimizes travel when the divers are normally sleeping. Such a
daily routine is not, however, mandatory. Other 16-hour periods of travel per 24hour routines are acceptable, although they shall include at least two stop periods
dispersed throughout the 24-hour period and travel may continue while the divers
sleep. An example of an alternate schedule is:
Alternate Sample Schedule
2300–0500
Travel
0500–0700
Rest Stop
0700–0900
Travel
0900–1500
Rest Stop
1500–2300
Travel
The timing of the stop is dependent upon operational requirements.
13-23.6

Atmosphere Control at Shallow Depths. As previously stated, the partial pressure

of oxygen in the chamber shall be maintained between 0.44 and 0.48 ata, with two
exceptions. The first is just before making the initial Upward Excursion and the
second during the terminal portion of saturation decompression. Approximately
1 hour before beginning an Upward Excursion, the chamber ppO2 may be
increased up to a maximum of 0.6 ata to ensure that the ppO2 after excursion
does not fall excessively. The ppO2 should be raised just enough so the postexcursion ppO2 does not exceed 0.48 ata. However, when excursions begin
from depths of 200 fsw or shallower, a pre-excursion ppO2 of 0.6 ata will result
in a post-excursion ppO2 of less than 0.44 ata. In these cases, the pre-excursion
ppO2 should not exceed 0.6 ata, but the post-excursion ppO2 should be increased
as rapidly as possible.
The second exception is at shallow chamber depth. As chamber depth decreases,
the fractional concentration of oxygen necessary to maintain a given partial
pressure increases. If the chamber ppO2 were maintained at 0.44–0.48 ata all the
way to the surface, the chamber oxygen percentage would rise to 44–48 percent.
Accordingly, for the terminal portion of saturation decompression, the allowable
oxygen percentage is between 19 and 23 percent. The maximum oxygen percentage

CHAPTER 13 — Saturation Diving

13-37

for the terminal portion of the decompression shall not exceed 23 percent, based
upon fire-risk considerations.
13-23.7

Saturation Dive Mission Abort. If it is necessary to terminate a saturation dive

after exceeding the abort limits (see paragraph 13-20.4), standard saturation
decompression procedures shall be followed.

13‑23.7.1

Emergency Cases. In exceptional cases it could be necessary to execute a mission

abort and not be able to adhere to standard saturation decompression procedures.
The emergency abort procedures should only be conducted for grave, unforeseen
casualties that require deviation from the standard decompression procedures such
as:
n An unrepairable failure of key primary and related backup equipment in the
dive system that would prevent following standard decompression procedures.
n Unrepairable damage to the diving support vessel or diving support facility.
n A life-threatening medical emergency where the risk of not getting the patient
to a more specialized medical care facility outweighs the increased risk of
pulmonary oxygen toxicity and increased risk of decompression sickness
imposed upon the patient by not following standard saturation decompression
procedures.
An Emergency Abort Procedure was developed and has received limited testing.
It enables the divers to surface earlier than would be allowed normally. However,
the time saved may be insignificant to the total decompression time still required,
especially if the divers have been under pressure for 12 hours or more. In
addition, executing the Emergency Abort Procedure increases the diver’s risk for
decompression sickness and complications from pulmonary oxygen toxicity.
Before executing a mission abort procedure that does not follow standard
decompression procedures or the abort procedures contained in paragraph 13-20.4,
the Commanding Officer must carefully weigh the risk of the action, relying on
the advice and recommendations of the Master Diver, Dive Watch Supervisor,
Dive Watch Officer, and Saturation Diving Medical Officer. Specifically, it must be
determined if the time saved will benefit the diver’s life despite the increased risks,
and whether the Emergency Abort Procedure can be supported logistically.
NOTE

13-38

USN dive system design incorporates separate primary, secondary, and
treatment gas supplies and redundancy of key equipment. It is neither the
intent of this section nor a requirement that saturation dive systems be
configured with additional gas stores specifically dedicated to execution
of an emergency abort procedure. Augmentation gas supplies if required
will be gained by returning to port or receiving additional supplies on
site.

U.S. Navy Diving Manual — Volume 3

Except in situations where the nature or time sensitivity of the emergency does not
allow, technical and medical assistance should be sought from the Navy Experimental
Diving Unit prior to deviating from standard saturation decompression procedures.
13‑23.7.2

Emergency Abort Procedure. Emergency Abort Procedures should only be
conducted for grave casualties that are time critical. Decompression times and
chamber oxygen partial pressures for emergency aborts from helium-oxygen
saturation are shown in Table 13-10.
Table 13‑10. Emergency Abort Decompression Times and Oxygen Partial Pressures.
One-Foot Stop Time (min)
Post Excursion Depth
(fsw)

ppO2 (ata)

1000–200 fsw

200–0 fsw

0–203

0.8

11

18

204–272

0.7

11

19

273–1000

0.6

12

21

Emergency Abort decompression is begun by making the maximum Upward
Excursion allowed by Table 13-8. Rate of travel should not exceed 2 fsw/min. The
upward excursion includes a 2-hour hold at the upward excursion limit. Travel
time is included as part of the 2-hour hold. Following the Upward Excursion,
the chamber oxygen partial pressure is raised to the value shown in Table 13-10.
Decompression is begun in 1-foot increments using the times indicated in Table 1310. Rate of travel between stops is not to exceed 1 fsw/min. Travel time is included
in the next stop time. The partial pressure of oxygen is controlled at the value
indicated until the chamber oxygen concentration reaches 23 percent. The oxygen
concentration is then controlled between 19 and 23 percent for the remainder of the
decompression. Stop travel at 4 fsw until total decompression time has elapsed and
then travel to the surface at 1 fsw/min.
For example, the maximum depth of the diver in the last 48 hours was 400 fsw,
and the Commanding Officer approves using the Emergency Abort Procedure.
From the Upward Excursion Table, the complex travels to 307 fsw at a rate not to
exceed 2 fsw/min. It takes 46.5 minutes to travel. This time is part of a 2-hour hold
requirement as part of the upward excursion for emergency aborts.
Because the post-excursion depth is between 273–1,000 fsw, the chamber oxygen
partial pressure is raised to 0.6 ata. Once the atmosphere is established and the
remainder of the 2-hour hold completed, begin decompression in 1-foot increments
with stop times of 12 minutes from 307 to 200 fsw. The travel rate between stops
should not exceed 1 fsw/min. Travel time is included in the stop time. It will
take 21.4 hours to arrive at 200 fsw.
At 200 fsw the 1-foot stop time changes to 21 minutes. It will take 70 hours to
reach the surface. The total decompression time is 93.4 hours (3 days, 21 hours, 21
minutes, 36 seconds). By contrast, standard saturation decompression would take
approximately 4 days and 3 hours to complete.
CHAPTER 13 — Saturation Diving

13-39

During and following the dive, the divers should be monitored closely for signs
of decompression sickness and for signs of pulmonary oxygen toxicity. The latter
includes burning chest pain and coughing. The divers should be kept under close
observation for at least 24 hours following the dive.
If the emergency ceases to exist during the decompression, hold for a minimum
of 2 hours, revert to standard decompression rates, and allow the oxygen partial
pressure to fall to normal control values as divers consume the oxygen. Venting to
reduce the oxygen level is not necessary.
13-23.8

Decompression Sickness (DCS). Decompression sickness may occur during

a saturation dive as a result of an Upward Excursion or as a result of standard
saturation decompression. The decompression sickness may manifest itself as
musculoskeletal pain (Type I) or as involvement of the central nervous system and
organs of special sense (Type II). Due to the subtleness of decompression sickness
pain, all divers should be questioned about symptoms when it is determined that
one diver is suffering from decompression sickness. For treatment, refer to Figure
13-13.
13‑23.8.1

Type I Decompression Sickness. Type I Decompression Sickness may result

from an Upward Excursion or as the result of standard saturation decompression.
It is usually manifested as the gradual onset of musculoskeletal pain most often
involving the knee. Divers report that it begins as knee stiffness that is relieved
by motion but which increases to pain over a period of several hours. Care must
be taken to distinguish knee pain arising from compression arthralgia or injury
incurred during the dive from pain due to decompression sickness. This can
usually be done by obtaining a clear history of the onset of symptoms and their
progression. Pain or soreness present prior to decompression and unchanged after
ascent is unlikely to be decompression sickness. Type I Decompression Sickness
that occurs during an Upward Excursion or within 60 minutes immediately
after an Upward Excursion shall be treated in the same manner as Type II
Decompression Sickness, as it may herald the onset of more severe symptoms.
Type I Decompression Sickness occurring more than 60 minutes after an Upward
Excursion or during saturation decompression should be treated by recompressing
in increments of 5 fsw at 5 fsw/ min until distinct improvement of symptoms
is indicated. Recompression of more than 30 fsw is usually unnecessary. Once
treatment depth is reached, the stricken diver is given a treatment gas, by BIBS
mask, with an oxygen partial pressure between 1.5 and 2.8 ata. Interrupt treatment
gas breathing every 25 minutes with 5 minutes of breathing chamber atmosphere.
Divers should remain at treatment depth for at least 2 hours on treatment gas
following resolution of symptoms.
Decompression can then be resumed using standard saturation decompression
rates. Further Upward Excursions are not permitted.

13-40

U.S. Navy Diving Manual — Volume 3

ANNEX A2
SATURATION DECOMPRESSION SICKNESS
TREATMENT FLOW CHART
DIAGNOSIS DCS

Excursion
Within Past
60 MIN

No

TYPE
1

No

Recompress at
5 FPM in 5 FSW
Increments to
Depth of Distinct
Improvement

Recompress at
5 FPM to Depth
of Distinct
Improvement

No
Continue
Recompression
at Direction of
DMO Until Relief
is Obtained

Start RX Gas 1.5
to 2.8 ATA PPO2
:25 ON/:05 OFF

Recompress to
Storage Depth
at 30 FPM

TYPE
2
Yes

Yes

Yes

Significant
Improvement
Within 10
MIN

Yes

Continue RX Gas
TIL SX Resolved
Start RX Gas 1.5 to
2.8 ATA PPO2 :25 ON/
:05 OFF
Remain at RX
Depth at Least
2 HRS
Following
Resolution of
SX

Remain at RX
Depth at Least
12 HRS
Following
Resolution of
SX

Continue/Resume
RX Gas at Least 2
HRS

Resume Standard Saturation Decompression
No Further Upward Excursions Authorized
Figure 13‑13. Saturation Decompression Sickness Treatment Flow Chart.

CHAPTER 13 — Saturation Diving

13-41

13‑23.8.2

Type II Decompression Sickness. Type II Decompression Sickness in saturation

diving most often occurs as a result of an Upward Excursion. The onset of
symptoms is usually rapid, occurring during the Upward Excursion or within
the first hour following an excursion ascent. Inner ear decompression sickness
manifests itself as nausea and vomiting, vertigo, loss of equilibrium, ringing in
the ears and hearing loss. Central nervous system (CNS) decompression sickness
may present itself as weakness, muscular paralysis, or loss of mental alertness and
memory. Type II Decompression Sickness resulting from an Upward Excursion
is a medical emergency and shall be treated by immediate recompression at 30
fsw/min to the depth from which the Upward Excursion originated. When Type II
Decompression Sickness symptoms do not occur in association with an Upward
Excursion, compression at 5 fsw/min to the depth where distinct improvement is
noted should take place. Upon reaching treatment depth, symptoms usually begin
to abate rapidly. If symptoms are not significantly improved within 5 to 10 minutes
at the initial treatment depth, deeper recompression at the recommendation of
a Saturation Diving Medical Officer should be started until significant relief is
obtained. After reaching the final treatment depth, treatment gas having an oxygen
partial pressure of 1.5 to 2.8 ata shall be administered to the stricken diver for
25-minute periods interspersed with 5 minutes of breathing chamber atmosphere.
Treatment gas shall be administered for at least 2 hours and the divers shall remain
at the final treatment depth for at least 12 hours following resolution of symptoms.
Decompression can then be resumed using standard saturation decompression
using rates shown in Table 13-9. Further Upward Excursions are not permitted.
13-24

POSTDIVE PROCEDURES

After surfacing from the dive, the divers are still at risk from decompression sickness. Divers shall remain in the immediate vicinity of a chamber for 2 hours and
within 30 minutes travel of a chamber for 48 hours after the dive. Divers shall not
fly for 72 hours after the dive surfaces.

13-42

U.S. Navy Diving Manual — Volume 3

CHAPTER 14

Breathing Gas Mixing Procedures
14-1

INTRODUCTION
14-1.1

Purpose. The purpose of this chapter is to familiarize divers with the techniques

used to mix divers’ breathing gas.
14-1.2

Scope. This chapter outlines the procedures used in mixing divers’ breathing and

treat­ment gas.
14-2

MIXING PROCEDURES

Two or more pure gases, or gas mixtures, may be combined by a variety of tech­
niques to form a final mixture of predetermined composition. This section discusses
the techniques for mixing gases. Aboard ships, where space is limited and motion
can affect the accuracy of precision scales, gases are normally mixed by partial
pressure or by continuous-flow mixing systems. The methods of mixing by volume
or weight are most suitable for use in shore-based facilities because the procedure
requires large, gas-tight holding tanks and precision scales.
14-2.1

Mixing by Partial Pressure. Mixing gases in proportion to their partial pressures in
the final mixture is the method commonly used at most Navy facilities. The basic
principle behind this method is Dalton’s Law of Partial Pressures, which states
that the total pressure of a mixture is equal to the sum of the partial pressures of all
the gases in the mixture.

The partial pressure of a gas in a mixture can be calculated using the ideal-gas
(perfect-gas) method or the real-gas method. The ideal-gas method assumes that
pressure is directly proportional to the temperature and density of a gas. The realgas method additionally accounts for the fact that some gases will compress more
or less than other gases.
Compressibility is a physical property of every gas. Helium does not compress as
much as oxygen.
If two cylinders with the same internal volume are filled to the same pressure, one
with oxygen and the other with helium, the oxygen cylinder will hold more cubic
feet of gas than the helium cylinder. As pressure is increased, and/or as tempera­ture
is decreased in both cylinders, the relative difference in the amount of gas in each
cylinder increases accordingly. The same phenomenon results when two gases are
mixed in one cylinder. If an empty cylinder is filled to 1,000 psia with oxygen and
topped off to 2,000 psia with helium, the resulting mixture contains more oxygen
than helium.
Being aware of the differences in the compressibility of various gases is usually
sufficient to avoid the problems that are often encountered when mixing gases.

CHAPTER 14 — Breathing Gas Mixing Procedures

14-1

When using the ideal-gas procedures, a diver should add less oxygen than is called
for, analyze the resulting mixture, and compensate as required. These procedures
take into consideration the compressibility of the gases being mixed. Regardless
of the basis of the calculations used to deter­mine the final partial pressures of the
constituent gases, the mixture shall always be analyzed for oxygen content prior
to use.
14-2.2

Ideal-Gas Method Mixing Procedure. Gas mixing may be prepared one cylinder

at a time or to and from multiple cylin­ders. The required equipment is inert gas,
oxygen, mix cylinders or flasks, an oxygen analyzer, and a mixing manifold. A gas
transfer system may or may not be used. Typical mixing arrangements are shown
in Figure 14-1 and Figure 14-2. To mix gas using the idea-gas method:
1. Measure the pressure in the inert-gas cylinder(s) PI.

2. Calculate the pressure in the mixed-gas cylinder(s) after mixing, using the fol­

lowing equation:
PF =

PI + 14.7
− 14.7
A

Where:
=
PF
PI
=
A 		 =

Final mix cylinder pressure, psig*
Inert gas cylinder pressure, psig
Decimal percent of inert gas in the final mixture

* PF cannot exceed the working pressure of the inert gas cylinder.
3. Measure the pressure in the oxygen cylinder(s), PO.
4. Determine if there is sufficient pressure in the oxygen cylinder(s) to accom­

plish mixing with or without an oxygen transfer pump.

PO ≥ (2PF - PI) + 50
Where:
PO		 = Pressure in the oxygen cylinder, psig
50		 = Required minimum over pressure, psi
≥ means greater than or equal to
5. Connect the inert-gas and oxygen cylinder(s) using an arrangement shown in

Figure 14‑1 or Figure 14‑2.

6. Open the mix gas cylinders valve(s).
7. Open the oxygen cylinders valve. Bleed oxygen into the mix gas cylinders at a

maximum rate of 70 psi minute until the desired PF is reached.

14-2

U.S. Navy Diving Manual — Volume 3

Ox
yg
en
B

an
k

Ba
Sto nk
ps

Mi
Ve
nt
Nit

rog
en
/He
liu
m

xS

tor
ag
eC

ylin
de
rs

Ba
nk

He/N2 Bank

Bank Stop
Vent

O2 Bank

Mixed Gas
Banks

Figure 14‑1. Mixing by Cascading.

CHAPTER 14 — Breathing Gas Mixing Procedures

14-3

He/N2 Bank
Mixed Gas
Banks
Gas Transfer System
Bank Stop
Vent

Drive
Inlet

Receiver

O2

Diluent

Outlet

Control
Drive
Control

O2 Bank

Figure 14‑2. Mixing with Gas Transfer System.

14-4

U.S. Navy Diving Manual — Volume 3

8. Close the oxygen and mixed-gas cylinder valves. The heat of compression will

have increased the temperature of the mixed-gas cylinders and will give a false
indication of the pressure in the cylinder. The calculation requires the PF to be
taken at the same temperature as PI. However, because of the compressibility
effects, more oxygen will normally have to be bled into the mixed-gas cylin­
ders than expected. Therefore, allow the cylinders to stand for at least six hours
to permit the gases to mix homogeneously, or if equipment is available, roll the
cylinder for at least one hour. Analyze the gas mixture to determine its oxygen
percentage. The percentage of oxygen should be near or slightly below the
desired percentage.

9. Add oxygen as necessary and reanalyze the mixture. Repeat this step until the

desired mixture is attained.

14-2.3

14‑2.3.1

Adjustment of Oxygen Percentage. After filling a mixed-gas cylinder, it may be
necessary to increase or decrease the percentage of oxygen in the cylinder.
Increasing the Oxygen Percentage. To increase the oxygen percentage:
1. Subtract the known percentage of oxygen from 100 to obtain the existing per­

centage of helium.

2. Multiply the helium percentage by the cylinder pressure to obtain the pressure

of helium in the cylinder.

3. Subtract the desired oxygen percentage from 100 to obtain the desired percent­

age of helium.

4. Divide the existing helium pressure (Step 2) by the desired helium percentage

(Step 3) in decimal form. (This step gives the cylinder pressure that will exist
when enough oxygen has been added to yield the desired percentage.)

5. Add oxygen until this pressure is reached.
6. Allow temperature and pressure to stabilize and add more oxygen, if necessary.

The following formula sums up the computation:
F =

P × (1.00 − O O )
(1.00 − O f )

CHAPTER 14 — Breathing Gas Mixing Procedures

14-5

Where:
F
P
Oo
Of

=
=
=
=

Final cylinder pressure
Original Cylinder pressure
Original oxygen % (decimal form)
Final oxygen % (decimal form)

Sample Problem. An oxygen cylinder contains 1,000 psi of a 16 percent oxygen

mixture, and a 20 percent oxygen mixture is desired.
1, 000 × (1.00 − 0.16 )
1.00 − 0.20
1, 000 × 84
=
0.80
840
=
0.80
= 1, 050 psi

F=

Add 50 psi of oxygen to obtain a cylinder pressure of 1,050 psi.
14‑2.3.2

Reducing the Oxygen Percentage. To reduce the oxygen percentage, use the

following procedure:

1. Multiply oxygen percentage (decimal form) by the cylinder pressure to obtain

the psi of oxygen pressure.

2. Divide this figure by the desired oxygen percentage (decimal form). This yields

the final pressure to be obtained by adding helium.

3. Add helium until this pressure is reached.
4. Allow temperature and pressure to stabilize and add more helium, if

necessary.

The following formula sums up the computation:
F=

P × OO
Of

Where:
F
P
Oo
Of

14-6

=
=
=
=

Final cylinder pressure
Original Cylinder pressure
Original oxygen % (decimal form)
Final oxygen % (decimal form)

U.S. Navy Diving Manual — Volume 3

Sample Problem. For a cylinder containing 1,000 psi of a 20 percent oxygen

mixture and a 16 percent oxygen mixture is desired.
1,000 × 0.20
0.16
200
=
0.16
= 1, 250 psi

F=

Add 250 psi of helium to obtain a cylinder pressure of 1,250 psi.
These mixing procedures also apply to mixing by means of an oxygen-transfer
pump. Instead of being bled directly from an oxygen cylinder into a helium cylinder,
oxygen may be drawn from a cylinder at low pressure by the oxygen-transfer pump
until the proper cylinder pressure is reached. This allows most of the oxygen in the
cylinder to be used, and it also conserves gas.
14-2.4

Continuous-Flow Mixing. Continuous-flow mixing is a precalibrated mixing

system that proportions the amounts of each gas in a mixture by controlling the
flow of each gas as it is deliv­ered to a common mixing chamber. Continuous-flow
gas mixing systems perform a series of functions that ensure extremely accurate
mixtures. Constituent gases are regulated to the same pressure and temperature
before they are metered through precision micro-metering valves. The valve
settings are precalibrated and displayed on curves that are provided with every
system and relate final mixture percentages with valve settings. After mixing,
the mixture is analyzed on-line to provide a continuous history of the oxygen
percentage. Many systems have feed­back controls that automatically adjust the
valve settings when the oxygen percentage of the mixture varies from preset
tolerance limits. The final mixture may be supplied directly to a diver or a chamber
or be compressed into storage tanks for later use.
14-2.5

Mixing by Volume. Mixing by volume is a technique where known volumes of each

gas are delivered to a constant-pressure gas holder at near-atmospheric pressure.
The final mixture is subsequently compressed into high-pressure cylinders.
Mixing by volume requires accurate gas meters for measuring the volume of each
gas added to the mixture. When preparing mixtures with this technique, the gases
being mixed shall be at the same temperature unless the gas meters are temperature
compensated.
The volumes of each of the constituent gases are calculated based on their desired
percentages in the final mixture. For example, if 1,000 scf of a 90 percent helium/10
percent oxygen mixture is needed, 900 scf of helium will be added to 100 scf of
oxygen. Normally, an inflatable bag large enough to contain the required volume
of gas at near-atmospheric pressure is used as the mixing chamber. The pure
gases, which are initially contained in high-pressure cylinders, are regulated at
atmospheric pressure, metered, and then piped into the mixing chamber. Finally,
the mixture is compressed and stored in high-pressure flasks or cylinders.

CHAPTER 14 — Breathing Gas Mixing Procedures

14-7

Provided that the temperatures of the constituent gases are essentially the same,
extremely accurate mixtures are possible by using the volume technique of mixing.
Additionally, care must be taken to ensure that the mixing chamber is either
completely empty or has been filled with a known mixture of uncontami­nated gas
before mixing.
14-2.6

Mixing by Weight. Mixing by weight is most often employed where small,

portable cylinders are used. This proportions the gases in the final mixture by the
weight that each gas adds to the initial weight of the container. When mixing by
weight, the empty weight of the container must be known as well as the weight
of any gases already inside the container. Although the accuracy of the mixture
when using this technique is not affected by variations in gas temperature, it is
directly dependent on the accuracy of the scale being used to weigh the gases.
This accuracy shall be known and the operator must be aware of its effect on the
accuracy of the composition of the final mixture. As a safeguard, the final mixture
must be analyzed for composition using an accurate method of analysis.
14-3

GAS ANALYSIS

The precise determination of the type and concentration of the constituents of
breathing gas is of vital importance in many diving operations. Adverse physio­
logical reactions can occur when exposure time and concentrations of various
components in the breathing atmosphere vary from prescribed limits. Analysis
of oxygen content of helium-oxygen mixtures shall be accurate to within ± 0.5
percent.
The quality of the breathing gas is important in both air and mixed-gas diving.
In air diving, the basic gas composition is fixed, and the primary consideration is
directed toward determining if gaseous impurities are present in the air supply (i.e.
carbon monoxide, hydrocarbons) and the effects of inadequate ventilation (carbon
dioxide). Using analytical equipment in air diving is not routine practice. Analyt­
ical equipment is generally employed only when it is suspected that the air supply
is not functioning properly or when evaluating new equipment.
Gas analysis is essential in mixed-gas diving. Because of the potential hazards
presented by anoxia and by CNS and pulmonary oxygen toxicity, it is mandatory
that the oxygen content of the gas supply be determined before a dive. Oxygen
analysis is the most common, but not the only type of analytical measurement that
is performed in mixed-gas diving. In deep diving systems, scrubbing equipment
performance must be monitored by carbon dioxide analysis of the atmosphere.
Long-term maintenance of personnel under hyperbaric conditions often necessi­
tates the use of a range of analytical procedures. Analyses are required to determine
the presence and concentration of minor quantities of potentially toxic impurities
resulting from the off-gassing of materials, metabolic processes, and other sources.

14-8

U.S. Navy Diving Manual — Volume 3

14-3.1

Instrument Selection. Selecting an instrument for analyzing hyperbaric

atmospheric constituents shall be determined on an individual command basis.
Two important characteristics are accuracy and response time. Accuracy within
the range of expected concentration must be adequate to determine the true value
of the constituent being studied. This characteristic is of particular importance
when a sample must be taken at elevated pressure and expanded to permit analysis.
The instrument’s response time to changes in concentration is important when
measuring constituents that may rapidly change and result in quick development
of toxic conditions.
Response times of up to 10 seconds are adequate for monitoring gas concentra­
tions such as oxygen and carbon dioxide in a diving apparatus. When monitoring
hyperbaric chamber atmospheres, response times of up to 30 seconds are accept­
able. The instruments used should accurately measure concentrations to within
1/10 of the maximum allowable concentration. Thus, to analyze for carbon dioxide
with a maximum permissible concentration of 5,000 ppm (SEV), an instrument
with an accuracy of at least 500 ppm (SEV) must be used.
In addition to accuracy and response time, portability is a factor in choosing the
correct instrument. While large, permanently-mounted instruments are acceptable
for installation on fixed-chamber facilities, small hand-carried instruments are
better suited for emergency use inside a chamber or at remote dive sites.
14-3.2

Techniques for Analyzing Constituents of a Gas. The constituents of a gas may
be analyzed both qualitatively (type determination) and quantitatively (type and
amount) using many different techniques and instru­ments. Guidance regarding
instrument selection can be obtained from NAVSEA, NEDU, or from instrument
manufacturer technical representatives. Although each technique is not discussed,
the major types are listed below as a reference for those who desire to study them
in detail.









Mass spectrometry
Colorimetric detection
Ultraviolet spectrophotometry
Infrared spectrophotometry
Gas chromatography
Electrolysis
Paramagnetism

CHAPTER 14 — Breathing Gas Mixing Procedures

14-9

PAGE LEFT BLANK INTENTIONALLY

14-10

U.S. Navy Diving Manual — Volume 3

VOLUME 4

Closed Circuit and
Semiclosed Circuit
Diving Operations
15

Electronically
Controlled ClosedCircuit Underwater
Breathing Apparatus
(EC-UBA) Diving

16

Closed Circuit Oxygen
UBA (CC-UBA) Diving

U.S. NAVY DIVING MANUAL

PAGE LEFT BLANK INTENTIONALLY

Volume 4 - Table of Contents
Chap/Para
15

Page
ELECTRONICALLY CONTROLLED CLOSED-CIRCUIT UNDERWATER BREATHING
APPARATUS (EC-UBA) DIVING

15-1 INTRODUCTION.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-1
15-1.1

Purpose. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-1

15-1.2

Scope .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-1

15-2 PRINCIPLES OF OPERATION. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-1
15-2.1

Diving Safety.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-2

15-2.2

Advantages of EC-UBA..  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-3

15-2.3

Recirculation and Carbon Dioxide Removal. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-3
15‑2.3.1 Recirculating Gas.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-3
15‑2.3.2 Full Face Mask.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-3
15‑2.3.3 Carbon Dioxide Scrubber.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-3
15‑2.3.4 Diaphragm Assembly.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-4
15‑2.3.5 Recirculation System.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-4
15‑2.3.6 Gas Addition, Exhaust, and Monitoring .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-5

15-3 OPERATIONAL PLANNING. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-5
15-3.1

Operational Limitations.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-7
15‑3.1.1 Oxygen Flask Endurance.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-8
15‑3.1.2 Effect of Cold Water Immersion on Flask Pressure.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-8
15‑3.1.3 Diluent Flask Endurance .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-8
15‑3.1.4 Canister Duration.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-9
15‑3.1.5 Human Physiological Limits.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-9

15-3.2

Equipment Requirements.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-9
15-3.2.1
15-3.2.2
15-3.2.3
15-3.2.4
15-3.2.5
15-3.2.6
15-3.2.7
15-3.2.8
15-3.2.9
15-3.2.10
15-3.2.11
15-3.2.12

Safety Boat. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-9
Buddy Lines.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-9
Distance Line.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-9
Standby Diver. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-9
Tending Lines.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-10
Marking of Lines.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-10
Diver Marker Buoy.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-10
Depth Gauge/Wrist Watch.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-10
NDC.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-11
Thermal Protection. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-11
Full Face Mask (FFM) .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-11
Emergency Breathing System (EBS).  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-11

15-3.3

Recompression Chamber Requirements .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-11

15-3.4

Diving Procedures for EC-UBA.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-13

Table of Contents­—Volume 4

4–i

Chap/Para

Page
15-3.4.1 Diving Methods. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-13
15-3.5

Diving in Contaminated Water .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-15

15-3.6

Special Diving Situations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-15

15-4 PREDIVE PROCEDURES .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-15
15-4.1

Diving Supervisor Brief.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-15

15-4.2

Diving Supervisor Check. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-15

15-5 DESCENT.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-17
15-6 UNDERWATER PROCEDURES. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-17
15-6.1

General Guidelines.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-17

15-6.2

At Depthf.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-18

15-7 ASCENT PROCEDURES.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-18
15-8 DECOMPRESSION PROCEDURES .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-18
15-8.1

Monitoring ppO2.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-18

15-8.2

Rules for Using EC-UBA Decompression Tables.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-19

15-8.3

PPO2 Variances. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-22

15-8.4

Emergency Breathing System (EBS) .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-22
15-8.4.1 EBS Deployment Procedures. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-22
15-8.4.2 EBS Ascent Procedures.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-23

15-9 MULTI-DAY DIVING FOR 1.3 ATA PPO2 EC-UBA .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-23
15-10 ALTITUDE DIVING PROCEDURES AND FLYING AFTER DIVING .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-23
15-11 POSTDIVE PROCEDURES .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-24
15-12 MEDICAL ASPECTS OF CLOSED-CIRCUIT MIXED-GAS UBA .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-24
15-12.1 Central Nervous System (CNS) Oxygen Toxicity .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-24
15-12.1.1 Causes of CNS Oxygen Toxicity .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-24
15-12.1.2 Symptoms of CNS Oxygen Toxicity.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-25
15-12.1.3 Treatment of Nonconvulsive Symptoms. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-25
15-12.1.4 Treatment of Underwater Convulsion. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-25
15‑12.1.5 Prevention of CNS Oxygen Toxicity.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-26
15‑12.1.6 Off-Effect .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-26
15-12.2 Pulmonary Oxygen Toxicity. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-26
15-12.3 Oxygen Deficiency (Hypoxia).  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-26
15‑12.3.1 Causes of Hypoxia.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-26
15‑12.3.2 Symptoms of Hypoxia .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-27
15‑12.3.3 Treating Hypoxia .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-27

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Chap/Para

Page
15‑12.3.4 Treatment of Hypoxic Divers Requiring Decompression.  .  .  .  .  .  .  .  .  .  .  .  .  . 15-27
15-12.4 Carbon Dioxide Toxicity (Hypercapnia).  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-27
15‑12.4.1 Causes of Hypercapnia .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-27
15‑12.4.2 Symptoms of Hypercapnia.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-27
15‑12.4.3 Treating Hypercapnia.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-28
15‑12.4.4 Prevention of Hypercapnia.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-28
15-12.5 Chemical Injury .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-29
15‑12.5.1 Causes of Chemical Injury.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-29
15‑12.5.2 Symptoms of Chemical Injury. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-29
15‑12.5.3 Management of a Chemical Incident.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-29
15‑12.5.4 Prevention of Chemical Injury .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-30
15-12.6 Omitted Decompression.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-30
15‑12.6.1 At 20 fsw. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-30
15‑12.6.2 Deeper than 20 fsw .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-30
15‑12.6.3 Deeper than 20 fsw Recompression Chamber not Available Within 60min.15-31
15‑12.6.4 Evidence of Decompression Sickness or Arterial Gas Embolismin.  .  .  .  .  . 15-32
15-12.7 Decompression Sickness in the Water.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-32
15‑12.7.1 Diver Remaining in Water .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-32
15‑12.7.2 Diver Leaving the Water. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-32

15-13 EC-UBA DIVING EQUIPMENT REFERENCE DATA.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-32

16

CLOSED-CIRCUIT OXYGEN UBA (CC-UBA) DIVING

16-1 INTRODUCTION.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 16-1
16-1.1

Purpose. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 16-1

16-1.2

Scope .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 16-1

16-2 MEDICAL ASPECTS OF CLOSED-CIRCUIT OXYGEN DIVING. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 16-1
16-2.1

Central Nervous System (CNS) Oxygen Toxicity .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 16-2
16‑2.1.1 Symptoms of CNS Oxygen Toxicity.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 16-2
16‑2.1.2 Treatment of Nonconvulsive Symptoms. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 16-2
16‑2.1.3 Treatment of Underwater Convulsion. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 16-2
16‑2.1.4 Off-Effect .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 16-3

16-2.2

Pulmonary Oxygen Toxicity. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 16-3

16-2.3

Oxygen Deficiency (Hypoxia).  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 16-3
16‑2.3.1
16‑2.3.2
16‑2.3.3
16‑2.3.4
16‑2.3.5

16-2.4

Causes of Hypoxia.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
UBA Purge Procedures .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Underwater Purge .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Symptoms of Hypoxia .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Treatment of Hypoxia.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .

16-3
16-3
16-4
16-4
16-4

Carbon Dioxide Toxicity (Hypercapnia).  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 16-4

Table of Contents­—Volume 4

4–iii

Chap/Para

Page
16‑2.4.1 Treating Hypercapnia.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 16-4
16‑2.4.2 Prevention of Hypercapnia.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 16-5
16-2.5

Chemical Injury.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 16-5
16‑2.5.1 Causes of Chemical Injury.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 16-5
16‑2.5.2 Symptoms of Chemical Injury. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 16-5
16‑2.5.3 Treatment of a Chemical Incident .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 16-6
16‑2.5.4 Prevention of Chemical Injury .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 16-6

16-2.6

Middle Ear Oxygen Absorption Syndrome .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 16-6
16‑2.6.1 Causes of Middle Ear Oxygen Absorption Syndrome .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 16-6
16‑2.6.2 Symptoms of Middle Ear Oxygen Absorption Syndrome.  .  .  .  .  .  .  .  .  .  .  .  .  .  . 16-6
16‑2.6.3 Treating Middle Ear Oxygen Absorption Syndrome.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 16-7
16‑2.6.4 Prevention of Middle Ear Oxygen Absorption Syndrome.  .  .  .  .  .  .  .  .  .  .  .  .  .  . 16-7

16-3 CLOSED-CIRCUIT OXYGEN EXPOSURE LIMITS.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 16-7
16-3.1

Transit with Excursion Limits. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 16-7
16‑3.1.1 Transit with Excursion Limits Table .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 16-7
16‑3.1.2 Transit with Excursion Limits Definitions .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 16-8
16‑3.1.3 Transit with Excursion Rules .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 16-9
16‑3.1.4 Inadvertent Excursions. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 16-9

16-3.2

Single-Depth Limits.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 16-10
16‑3.2.1 Single-Depth Oxygen Exposure Limits Table.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 16-10
16‑3.2.2 Single-Depth Limits Definitions .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 16-10
16‑3.2.3 Depth/Time Limits .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 16-10

16-3.3

Lock Out/In from Excursion Depth .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 16-10

16-3.4

Exposure Limits for Successive Oxygen Dives. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 16-11
16‑3.4.1 Definitions for Successive Oxygen Dives. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 16-11
16‑3.4.2 Off-Oxygen Exposure Limit Adjustments.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 16-11

16-3.5

Exposure Limits for Successive Oxygen Dives. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 16-12
16‑3.5.1 Mixed-Gas to Oxygen Rule .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 16-12
16‑3.5.2 Oxygen to Mixed-Gas Rule .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 16-12

16-3.6

Oxygen Diving at High Elevations. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 16-13

16-3.7

Flying After Oxygen Diving.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 16-13

16-3.8

Combat Operations.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 16-13

16-4 OPERATIONS PLANNING.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 16-13

4–iv

16-4.1

Operating Limitations .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 16-13

16-4.2

Maximizing Operational Range.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 16-13

16-4.3

Training.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 16-14

16-4.4

Personnel Requirements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-14

16-4.5

Equipment Requirements.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 16-15

U.S. Navy Diving Manual—Volume 4

Chap/Para

Page
16-4.6

Predive Precautions .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 16-16

16-5 PREDIVE PROCEDURES .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 16-17
16-5.1

Equipment Preparation.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 16-17

16-5.2

Diving Supervisor Brief.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 16-17

16-5.3

Diving Supervisor Check. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 16-17
16‑5.3.1 First Phase.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 16-17
16‑5.3.2 Second Phase .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 16-17

16-6 WATER ENTRY AND DESCENT .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 16-18
16-6.1

Purge Procedure.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 16-18

16-6.2

Avoiding Purge Procedure Errors.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 16-18

16-7 UNDERWATER PROCEDURES. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 16-19
16-7.1

General Guidelines.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 16-19

16-7.2

UBA Malfunction Procedures .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 16-20

16-8 ASCENT PROCEDURES.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 16-20
16-9 POSTDIVE PROCEDURES AND DIVE DOCUMENTATION.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 16-20
16-10 MK-25.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 16-21

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U.S. Navy Diving Manual—Volume 4

Volume 4 - List of Illustrations
Figure

Page

15-1

MK 16 MOD 1 Closed-Circuit Mixed-Gas UBA.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-1

15-2

Typical EC-UBA Functional Diagram. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-2

15‑3

UBA Breathing Bag Acts to Maintain the Diver’s Constant Buoyancy
by Responding Counter to Lung Displacement.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-4

15-4

EC-UBA Dive Record Sheet .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-14

15-5

Typical EC-UBA Emergency Breathing System .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-21

15-6

MK 16 MOD 1 UBA General Characteristics.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-33

15‑7

MK 16 MOD 0 General Characteristics.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-34

15-8

Repetitive Dive Worksheet for 1.3 ata ppO2N202. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-38

15-9

Repetitive Dive Worksheet for 1.3 ata ppO2 HeO2 Dives. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-50

15-10

Dive Worksheet for Repetitive 0.75 ata ppO2N202 Dives.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-68

16-1

Diver in MK-25 CC-UBA .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 16-1

16-2

Example of Transit with Excursion. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-8

16‑3

MK 25 MOD 2 Operational Characteristics.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 16-21

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U.S. Navy Diving Manual—Volume 4

Volume 4 - List of Tables
Table

Page

15-1

EC-UBA Operational Characteristics. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-6

15-2

Personnel Requirements Chart for EC-UBA Diving. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-8

15-3

EC-UBA Diving Equipment Requirements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-10

15-4

MK 16 MOD 1 Recompression Chamber Requirements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-12

15-5

EC-UBA Dive Briefing.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-16

15-6

EC-UBA Line-Pull Signals.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-16

15-7

Initial Management of Asymptomatic Omitted Decompression EC-UBA Diver.  .  .  .  .  .  .  .  .  .  .  .  . 15-31

15-8

No Decompression Limits and Repetitive Group Designators for 1.3 ata ppO2N2O2 Dives .  .  . 15-36

15-9

Residual Nitrogen Timetable for 1.3 ata ppO2N2O2 Dives.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-37

15-10

1.3 ata ppO2N2O2 Decompression Tables.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-39

15-11

No Decompression Limits and Repetitive Group Designators for 1.3 ata ppO2 HeO2 Dives.  .  . 15-48

15-12

Residual Helium Timetable for 1.3 ata ppO2 HeO2 Dives .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-49

15-13

1.3 ata ppO2 HeO2 Decompression Tables .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-51

15-14

No Decompression Limits and Repetitive Group Designation Table for 0.75 ata Constant ppO2
N2O2 Dives. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-66

15-15

Residual Nitrogen Timetable for Repetitive 0.75 ata Constant ppO2N2O2 Dives.  .  .  .  .  .  .  .  .  .  .  . 15-67

15-16

Closed-Circuit Mixed-Gas UBA Decompression Table Using 0.75 ata Constant ppO2N2O2 .  . 15-69

15-17

Closed-Circuit Mixed-Gas UBA Decompression Table Using 0.75 ata Constant Partial Pressure
Oxygen in Helium. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-77

16‑1

Excursion Limits .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 16-8

16‑2

Single-Depth Oxygen Exposure Limits.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 16-10

16‑3

Adjusted Oxygen Exposure Limits for Successive Oxygen Dives. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 16-12

16‑4

CC-UBA Diving Equipment.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 16-16

16‑5

Diving Supervisor Brief .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 16-18

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U.S. Navy Diving Manual—Volume 4

CHAPTER 15

Electronically Controlled Closed-Circuit
Underwater Breathing Apparatus
(EC-UBA) Diving
15-1

INTRODUCTION

The U.S. Navy’s use of EC-UBA is primarily used to
satisfy the operational requirements of EOD divers,
SPECWAR combat divers, and NECC divers (Figure
15-1). This equipment combines the mobility of a
free-swimming diver with the depth advantages of
mixed gas. The term EC-UBA refers to a UBA using
ppO2 monitoring to control O2 addition at a constant
set-point with recirculation of 100 percent of the
breathing loop. This results in bubble-free operation,
except during ascent or inadvertent gas release.
This capability makes EC-UBA’s well-suited for
EOD and SPECWAR operations and for light work
applications requiring a longer bottom time than open
circuit SCUBA could provide. Improvements in gas
usage, dive duration, and depth capabilities provided
by the EC-UBA greatly increase the effectiveness of
the divers. Dives to 150 feet of seawater (fsw) can Figure 15-1. MK 16 MOD
be made when N2O2 (air) is used as a diluent and 300 1 Closed Circuit Mixed Gas
UBA.
fsw when using HeO2 (88/12) as a diluent, see Table
15-1 for EC-UBA data sheets. Due to the increased
breathing resistance, and concerns about carbon dioxide retention and CNS O2
toxicity, planned N2O2 dives deeper than 150 fsw are considered exceptional
exposure dives and require prior approval in accordance with OPNAVINST
3150.27 (series).
15-1.1

Purpose. This chapter provides general guidelines for EC-UBA diving, operations

and procedures. For detailed operation and maintenance instructions, see the
associated EC-UBA’s approved Technical Manual.

15-1.2

Scope. This chapter covers EC-UBA operational planning, general characteristics,

dive procedures, and unique medical aspects. Refer to Chapter 3 for the
comprehensive medical aspects in diving. The specific EC-UBA characteristics
and limitations are contained in the respective O&M manual.

15-2

PRINCIPLES OF OPERATION

EC-UBAs efficiently use the available gas supply to extend underwater duration by
recirculating the breathing gas. To do this efficiently an EC-UBA must be able to:
CHAPTER 15 — EC-UBA Diving

15-1

n Remove carbon dioxide produced by metabolic action of the body.
n Monitor the ppO2 and add oxygen in order to replace the oxygen consumed by
metabolic action of the body.

EXHALATION
HOSE

TO CENTER
SECTION

MOUTHPIECE
ASSEMBLY

INHALATION
HOSE
OXYGEN
SENSORS

ABSORBENT
CANISTER

TO SECONDARY
DISPLAY
DILUENT
ADDITION VALUE

DIAPHRAGM
ASSEMBLY

TO PRIMARY
DISPLAY
DIAPHRAGM
DUMP VALVE
OXYGEN
ADDITION VALVE
CHECK VALVE
DILUENT
BYPASS VALVE

OXYGEN
BYPASS VALVE
OXYGEN
INLINE FILTER

DILUENT
INLINE FILTER

OXYGEN HIGH
PRESSURE INDICATOR

DILUENT HIGH
PRESSURE INDICATOR

OXYGEN
BOTTLE

DILUENT
BOTTLE VALVE

OXYGEN
BOTTLE VALVE
OXYGEN
REGULATOR

DILUENT
REGULATOR
DILUENT
BOTTLE

PRIMARY
BATTERY

PRIMARY
ELECTRONICS

Figure 15‑2. Typical EC-UBA Functional Diagram.

15-2.1

Diving Safety. EC-UBAs are more complex than open- circuit SCUBA and require
a high level of diver training and situational awareness. Careful dive planning is
essential. Diving safety is achieved only when:

n The diver has been thoroughly trained and qualified in the proper use of the
UBA.
n All equipment has been prepared for the specific diving conditions expected.
n The dive is conducted within specified depth and duration limits.

15-2

U.S. Navy Diving Manual — Volume 4

n The diver strictly adheres to and immediately implements all operational and
emergency procedures.
15-2.2

Advantages of EC-UBA. While functionally simpler in principle, the EC-UBA

tends to be more complex than the semi-closed UBA because of the oxygen
analysis and control circuits required. Offsetting this complexity, however, are
several inherent advantages:
n Aside from mixed or diluent gas addition during descent, the only gas required
at depth is oxygen to make up for metabolic consumption.
n The partial pressure of oxygen in the system is automatically controlled
throughout the dive to a preset value. No adjustment is required during a dive
for variations in depth and work rate.
n No inert gas leaves the system except by accident or during ascent, making
the closed circuit UBA relatively bubble-free and well suited for EOD and
SPECWAR operations.
15-2.3

15-2.3.1

Recirculation and Carbon Dioxide Removal. The diver’s breathing medium is
recirculated in a closed circuit UBA to remove carbon dioxide and permit reuse of
the inert diluent and unused oxygen in the mixture. The basic recirculation system
consists of a closed loop that incorporates inhalation and exhalation hoses and
associated check valves, a mouthpiece or full face mask (FFM), a carbon dioxide
removal unit, and a diaphragm assembly (Figure 15-2).
Recirculating Gas. Recirculating gas is normally moved through the circuit by the

natural inhalation-exhalation action of the diver’s lungs. Because the lungs can
produce only small pressure differences, the entire circuit must be designed for
minimum flow restriction.

15-2.3.2

Full Face Mask. The FFM uses an integral oral-nasal mask or T-bit to reduce dead

space and the possibility of rebreathing carbon dioxide-rich gas. Similarly, check
valves used to ensure one-way flow of gas through the circuit must be close to the
diver’s mouth and nose to minimize dead space. All breathing hoses in the system
must be of relatively large diameter to minimize breathing resistance.

15-2.3.3

Carbon Dioxide Scrubber. Carbon dioxide is removed from the breathing circuit

in a watertight canister filled with an approved carbon dioxide-absorbent material.
The bed of carbon dioxide-absorbent material chemically combines with the
diver’s exhaled carbon dioxide, while allowing the unused oxygen and diluent
to pass through it. If the canister is improperly filled, channels may form in the
absorbent granules permitting gas to bypass the absorbent material and allow the
build up of carbon dioxide in the UBA. The canister design must also provide a
low flow resistance for the gas while ensuring maximum contact between the gas
and the absorbent.

CHAPTER 15 — EC-UBA Diving

15-3

15-2.3.4

Diaphragm Assembly. A diaphragm assembly or counter lung is used in all closed

circuit UBAs to permit free breathing in the circuit. The need for such devices can
be readily demonstrated by attempting to exhale and inhale into an empty bottle.

The bottle, similar to the recirculation system without a bag, is unyielding and
presents extreme back pressure. In order to compensate, flexible diaphragms or a
breathing bag must be placed in the UBA circuit with a maximum displacement
equal to the combined volume of both lungs.
Constant buoyancy is inherent in the system because the gas reservoir acts counter
to normal lung action. In open-circuit scuba, diver buoyancy decreases during
exhalation due to a decrease in lung volume. In closed-circuit scuba, expansion of
the breathing bag keeps buoyancy constant. On inhalation, the process is reversed.
This cycle is shown in Figure 15-3.
The flexible gas reservoir must be located as close to the diver’s chest as possible
to minimize hydrostatic pressure differences between the lungs and the reservoir as
the diver changes attitude in the water.

Figure 15‑3. UBA Breathing Bag Acts to Maintain the Diver’s Constant Buoyancy by
Responding Counter to Lung Displacement.

15-2.3.5

Recirculation System. Optimal performance of the recirculation system depends

on proper maintenance of equipment, proper filling with fresh absorbent, and
accurate metering of oxygen input. To ensure efficient carbon dioxide removal
throughout the dive, personnel must carefully limit dive time to the specified
canister duration. Any factor that reduces the efficiency of carbon dioxide removal
increases the risk of carbon dioxide poisoning.

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U.S. Navy Diving Manual — Volume 4

WARNING		

15-2.3.6

The typical EC-UBA provides no visual warning of excess CO2 problems.
The diver should be aware of CO2 toxicity symptoms.
Gas Addition, Exhaust, and Monitoring. In addition to the danger of carbon

dioxide toxicity, the EC-UBA diver encounters the potential hazards of hypoxia
and central nervous system (CNS) oxygen toxicity. The EC-UBA must control the
ppO2 in the breathing medium within narrow limits for safe operation and must be
monitored frequently by the diver.
Hypoxia can occur when there is insufficient oxygen in the recirculation circuit to
meet metabolic requirements. If oxygen is not added to the breathing circuit, the
oxygen in the loop will be gradually consumed over a period of 2-5 minutes, at
which point the oxygen in the mixture is incapable of sustaining life.
CNS oxygen toxicity can occur whenever the oxygen partial pressure in the diver’s
breathing medium exceeds specified concentration and exposure time limits.
Consequently, the EC-UBA must function to limit the level to the appropriate ppO2
value.
The EC-UBA uses a direct control method of maintaining oxygen concentration in
the system, rather than the indirect method of a preset mass flow, common to semiclosed apparatus.
15-3

OPERATIONAL PLANNING

Table 15-1 lists the operational characteristics of the approved dive profiles for
the two pO2 set-points. Because the EC-UBA maintains a constant ppO2 and only
adds oxygen or diluent gas as needed, dives of long duration are possible. Mission
capabilities, dive procedures, and decompression procedures are radically different
from other diving methods. This requires a high level of diver training and awareness
and necessitates careful dive planning. Chapter 6 provides general guidelines for
operational planning. The information provided in this section is supplemental to
the EC-UBA O&M manual and provides specific guidelines for EC-UBA dive
planning. In addition to any other requirements, at least half of all dive training
should be at night or in conditions of restricted visibility. As per OPNAVINST
3150. 27 (series), units should allow frequent opportunity for training, ensuring
diver familiarity with equipment and procedures. If divers have been inactive and
operating conditions permit, workup dives are strongly recommended.

CHAPTER 15 — EC-UBA Diving

15-5

Table 15-1. EC-UBA Operational Characteristics.
Configuration

Characteristics

p0.75

Maintains a constant 0.75 pO2 throughout the dive regardless of
depth. (Note 1)

p1.3

Shifts from 0.75 pO2 to 1.3 pO2 at 33 fsw during descent, and from
1.3 pO2 to 0.75 pO2 at 13 fsw during ascent. (Note 2)

Limits

p0.75

p1.3

Normal

150 fsw N2O2

150 fsw N2O2

200 fsw HeO2

300 fsw HeO2

150 fsw N2O2

190 fsw N2O2

200 fsw HeO2

300 fsw HeO2

p0.75 / p1.3

Dive #1

Repet

N2O2 Dive Rules

No-Decompression

Unlimited No-Decompression

Decompression Dive

x3 No-Decompression (Note 3)

Decompression Dive

x1 Decompression

Dive #1

Repet

0-200 fsw
No-Decompression

0-200 fsw Unlimited
No-Decompression

0-200 fsw
Decompression Dive

0-200 fsw
x3 No-Decompression (Note 3)

0-200 fsw
Decompression Dive

0-200 fsw
x1 Decompression

201-300 fsw
Any Dive

None

Maximum

p1.3 HeO2 Dive Rules

Notes:
1. p0.75 Dives deeper than 80 fsw on N2O2 Diluent will have a higher level of nitrogen
narcosis than air dives to the same depth. Risk factors of nitrogen narcosis and overly long
decompression schedules vs. the 1.3 pO2 EC-UBA must be properly weighed and addressed.
2. The last decompression stop must be taken at 20 fsw to prevent inadvertent rig transition and
maintain the higher ppO2.
3. No-decompression dives may precede, follow, or bracket the decompression dive.
4. Within each decompression table, exceptional exposure dives are separated by a dashed line.
These tables are designed to be dived to the exceptional exposure line. Exceptional exposure
schedules are provided in case of unforeseen circumstances. Planned exceptional exposure
dives require prior CNO approval.
5. Switching diluents between dives is NOT authorized. There are no procedures for performing
a repetitive dive on helium following a dive on nitrogen or for performing a repetitive dive on
nitrogen following a dive on helium
6. Repetive dives between air and any EC-UBA using N2 diluent is authorized. See paragraph 9-9.3
for guidance.

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U.S. Navy Diving Manual — Volume 4

Initial EC-UBA diver qualifications may be obtained only by completion of a
formal course approved through their respective Learning Center under the Naval
Education and Training Command (NETC). EC-UBA qualifications remain
in effect as long as diver qualifications are maintained in accordance with their
respective Military Personnel Manual article.
Because of the similarities between EC-UBA’s, a diver qualified on one will be
considered qualified on the other provided the following conditions are met:
n Demonstrate knowledge of configuration differences and ppO2 setpoints
n Demonstrate knowledge of respective EPs and OPs
n Complete a full set of pre-mission, pre-dives, post-dives
n Conduct at least one open water training dive to a minimum of 40 fsw
Formal documentation will be signed by the Commanding Officer and retained in
the member’s training record.
A diver who has not made an EC-UBA dive in the previous six months must
re-familiarize himself with the respective EPs and OPs and must complete an
EC-UBA training dive prior to making an operational dive. Prior to conducting
EC-UBA decompression diving, a diver who has not conducted an EC-UBA
decompression dive within the previous six months must complete open water
decompression training dives consisting of a no decompression dive with short,
simulated decompression stops.
Workup dives for all members of the dive side are vital to success. All members in
all positions should be assessed for performance of their duties during workups, to
include standby diver being launched to the actual work depth.
Refer to Table 15-2 for the personnel requirements for EC-UBA diving.
15-3.1

Operating Limitations. Diving Supervisors must also consider the limiting factors

when planning EC- UBA operations. Overall dive limitations primarily consist of
these four factors:
n Oxygen Flask Endurance
n Diluent Flask Endurance
n Canister Duration
n Human physiological limits
All four factors must be assessed and taken into account during dive planning. The
shortest limiting factor shall be used for determining the dive plan.

CHAPTER 15 — EC-UBA Diving

15-7

Table 15-2. Personnel Requirements Chart for EC-UBA Diving.
EC-UBA Dive Team
Minimum Manning Requirements
Designation
Diving Supervisor
Diver
Standby Diver
Diver Tender
Standby Diver Tender
Timekeeper/Recorder
EBS Operator
Total Personnel Required

One
1
1
1
1

4

Diver
(Note 1)
(Note 2)
(Note 3)
(Note 1)
(Note 1)
(Note 4)

Two
1
2
1
1

Divers

(Note 2)
(Note 3)
(Note 1)
(Note 1)
(Note 4)

5

Notes:
1. Diving Supervisor may act as time keeper/recorder, standby tender.
2. At the Diving Supervisor’s discretion, the standby diver shall be fully dressed
with the exception of SCUBA or EC-UBA, mask, and fins. These items shall
be ready to don.
3. One tender per diver when divers are surface tended. If using a buddy line, one
tender is required for each buddy pair.
4. EBS Operator is required for EC-UBA decompression dives.

Oxygen Flask Endurance is typically the primary
limiting factor for EC-UBA dives. The respective O&M Manual contain the
calculations and guidelines for oxygen usage and should be used when planning
maximum dive times for EC-UBA dives.

15-3.1.1

Oxygen Flask Endurance.

15-3.1.2

Effect of Cold Water Immersion on Flask Pressure. Immersion in cold water will

reduce the flask pressure and actual cubic feet (acf) of gas available for the diver, in
accordance with Charles’/Gay-Lussac’s gas law. Based upon direct measurement,
available data, or experience, the coldest temperature expected during the dive is
used.

15-3.1.3

Diluent Flask Endurance. Under normal conditions the anticipated duration of the

diluent flask will exceed that of the oxygen flask. Diluent gas is used to maintain
the required gas volume in the breathing loop and is not depleted by metabolic
consumption. As the diver descends, diluent is added to maintain the total pressure
within the recirculation system at ambient water pressure. Loss of EC-UBA gas
due to leakage at depth requires the addition of diluent gas to the breathing loop
either automatically through the diluent addition valve or manually through the
diluent bypass valve to make up lost volume. Excessive gas loss caused by face
mask leaks, frequent depth changes, or improper UBA assembly will deplete the
diluent gas supply rapidly. The respective O&M Manual contain the calculations

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U.S. Navy Diving Manual — Volume 4

and guidelines for diluent and should be used when planning maximum dive times
for EC-UBA dives.
15-3.1.4

Canister Duration. The respective O&M Manual contain the calculations and

guidelines for CO2 absorbant useage and should be used when planning maximum
dive times for EC-UBA dives.
Absorbent duration is directly affected by work rate, environmental operating
temperature, and depth. Absorbent duration decreases as temperature decreases
and as depth increases.
15-3.1.5

Diver thermal considerations must be given a
higher consideration given the extended bottom times and personnel isolation that
EC-UBA’s provide. During decompression stops, a cold diver has a greater risk
of DCS than a comfortably warm diver. For warm water diving (temperatures
above 94°F) the primary concern limiting the dive duration is diver physiological
considerations vice any other factor.

Human Physiological Limits.

The EC-UBA carries a greater risk of CNS and Pulmonary oxygen toxicity than
open circuit diving. Follow the guidance in Section 15-9 for maximum oxygen
exposure times.
15-3.2

15-3.2.1

Equipment Requirements. The minimum equipment requirements for EC-UBA
dives are provided in Table 15-3 and explained in the following paragraphs.
Safety Boat. A minimum of one motorized safety boat must be present for all

open-water dives. A safety boat is also recommended for tended pier dives or
diving from shore. Safe diving practice in many situations, however, will require
the presence of more than one safety boat. The Diving Supervisor must determine
the number of boats required based on the diving area, medical evacuation plan,
night operations, and the number of personnel participating in the dive operation.

15-3.2.2

Buddy Lines. Buddy lines and the buddy system are the single greatest safety factor

for any closed- circuit UBA dives. The Diving Supervisor shall only conduct dives
without buddy lines in situations where their use is not feasible or where their use
will pose a greater hazard to the divers than diving without them, and only with
the approval of the CO or OIC where this authority has been delegated to him in
writing from the CO. Buddy lines shall be securely attached to both divers.

15-3.2.3

Distance Line. Special work situations may require divers to be spaced farther

apart than the typical buddy line length of 10 feet. Any buddy line over 10 feet
in length is referred to as a distance line. The length of the distance line shall not
exceed 100 feet. Distance lines shall be securely attached to both divers. Dive
Supervisors must thoroughly assess the risk and weigh the benefits associated with
divers being separated with a distance line.

15-3.2.4

Standby Diver. The standby diver shall be outfitted with the same capability as

the primary diver(s). This includes all ancillary equipment required for safe and
effective underwater work or rescue (ie, lights, weight, dive dress, fin type, etc.).

CHAPTER 15 — EC-UBA Diving

15-9

When appropriate during training and non-influence diving operations open circuit
SCUBA may be used. When open circuit SCUBA is used, the dive limitations shall
be IAW Chapter 7, as SCUBA is now the limiting factor.
When conducting decompression diving, the standby diver shall be outfitted with
an EC-UBA with the same capabilities as the primary diver(s).
Standby divers in EC-UBA are reminded to strictly adhere to the EC-UBA descent/
ascent rates.
Table 15‑3. EC-UBA Diving Equipment Requirements.
General

Diving Supervisor

Divers

Standby Diver

1. Motorized safety boat

1. Dive watch

1. Dive watch

1. Dive watch

2. Radio (communications
with parent
unit, chamber,
communication
between safety boats
when feasible)

2. Dive Bill list

2. Face mask

2. Face mask

3. Appropriate
Decompression
Tables

3. Fins

3. Fins

4. Dive knife

4. Dive knife

4. Recall device

5. Approved life
preserver or
Buoyancy Control
Device (BCD)

5. Approved life
preserver or
Buoyancy Control
Device (BCD)

6. Appropriate thermal
protection

6. Appropriate thermal
protection

7. EC-UBA

7. UBA with same depth
capability. For noninfluence ordnance
diving and training
dives, standby diver
may use SCUBA.

3. High-intensity, widebeam light (night
operations)
4. Dive flags and/or
special operations
lights as required
5. Sufficient (2 quarts)
fresh water in case of
chemical injury
6. Emergency Breathing
System for planned
decompression dives.

8. Depth Gauge or
NDC
9. Weight belt (as
needed)
10. Buddy lines /
Distance lines
11. Tending lines

8. Depth gauge or NDC
9. Weight belt (as
needed)
10. Tending line

15-3.2.5

15-3.2.6

15-3.2.7

15-3.2.8

15-10

Tending Lines. Diver tending lines should be manufactured from any light line
that is buoyant and easily marked as directed in paragraph 15-3.2.6 (one-quarter
inch polypropylene is quite suitable).
Marking of Lines. Lines used for controlling the depth of the diver(s) for
decompression diving shall be marked. This includes tending lines, marker lines,
and lazy-shot lines. Lines shall be marked with red and yellow or black bands
starting at the diver(s) or clump end. Red bands will indicate 50 feet and yellow or
black bands will mark every 10 feet.
Diver Marker Buoy. Diver marker buoys will be constructed to provide adequate
visual reference to monitor the diver’s location. Additionally, the amount of line
will be of sufficient length for the planned dive profile.
Depth Gauge/Wrist Watch. Each diver must have a depth gauge and wrist watch.

U.S. Navy Diving Manual — Volume 4

15-3.2.9

NDC. An NDC may be used in place of a depth gauge. See Appendix 2B for

specific guidance.

15-3.2.10

Thermal Protection. Divers must be equipped with adequate thermal protection to

perform effectively and safely. A cold diver will either begin to shiver or increase
his exercise rate, both of which will increase oxygen consumption and decrease
oxygen supply duration and canister duration. Refer to Appendix 2C for guidance
on warm water diving and Chapter 11 for guidance on cold water diving.

15-3.2.11

Full Face Mask (FFM). An authorized full face mask shall be used when deploying

a single untended diver, single marked diver, paired marked diver, and when using
an approved BC.

15-3.2.12

Emergency Breathing System (EBS). The Emergency Breathing System provides

an alternate breathing source for decompressing diver(s) in the event of a EC-UBA
failure. The EBS consists of an EC-UBA mounted on the EBS frame assembly and
charged with the same diluent gas as for the planned dive.

15-3.3

Recompression Chamber Requirements. Matching the availability of the
recompression chamber to the risk of the dive is critical to the diver’s safety.
The greater the risk of the dive, the more rigor is required in assessing chamber
requirements and the speed of available transport to get to the chamber. Table 15-4
provides guidance on selecting the appropriate level chamber for the dive mission.
Full guidance and information of the recompression chamber requirement levels
can be found in paragraph 6-5.1.3 and Table 6-1. Two types of EC-UBA diving
involving different levels of risk should be discussed:
1. Actual MCM or SPECWAR operations with live ordnance, or where a

specific clandestine operation set would incur a greater risk of discovery with
having a topside recompression chamber. The diving supervisor must weigh
the operational risk against the dive profile risk to determine which is the
determining factor.

2. All other operations that do not present imminent danger such as exercises,

training and qualification dives. In many cases, training dives by their nature have
a higher risk than operational dives. Divers in workups may be inexperienced
and the risk of diving related injuries are higher than in experienced divers.

CHAPTER 15 — EC-UBA Diving

15-11

Table 15-4. MK 16 MOD 1 Recompression Chamber Requirements
Chamber
Level

Type of Diving
MCM Operations

Exercises, Training, Qualification,
and Other
All dives deeper than 200 fsw.

Level 1

Not Required

All dives with decompression stops deeper
than 20 fsw.
or
Total decompression time exceeding 30
minutes. (Notes 1, 2, 3)
All exceptional exposure dives.
(Note 5)

Level II

All decompression dives with
stops deeper than 20 fsw.
or
Total decompression time
exceeding 30 minutes. (Note 3)
All exceptional exposure dives.
(Note 5)

Level III

All no-decompression dives.
All decompression dives with a
single stop at 20 fsw.
and
Total decompression time of 30
minutes or less. (Note 4, 6)

All decompression dives 200 fsw and
shallower with a single stop at 20 fsw.
and
Total decompression time of 30 minutes or
less. (Notes 1, 3)

All no-decompression dives 200 fsw and
shallower. (Note 1)

Note 1. All dives deeper than 150 fsw require Commanding Officer’s approval.
Note 2. Based on space constraints at the site, the Commanding Officer may authorize
extension of the surface interval to a maximum of 7 minutes.
Note 3. A non-Navy chamber may be used to satisfy this requirement if authorized in
writing by the first Flag Officer (FO) in the chain of command, and must include a NAVSEA
00C hazard analysis.
Note 4. A non-Navy chamber may be used if it is evaluated utilizing the NAVSEA nonNavy recompression chamber check sheet, and authorized in writing by the Commanding
Officer.
Note 5. All planned exceptional exposure dives require approval in accordance with
OPNAVINST 3150.27 (series).
Note 6. During extreme circumstances when a chamber cannot be reached within 6 hours
the Commanding Officer (or designated individual) can give authorization to use the
nearest recompression facility.

Use of a U.S. Navy certified chamber should be planned whenever possible.
U.S. Navy chambers are engineered to provide the maximum degree of safety
and reliability to ensure that the chamber is capable of delivering the full range
of treatments. A non-U.S. Navy chamber may be used to meet requirements, as

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U.S. Navy Diving Manual — Volume 4

specified in Table 15-4, provided it has been inspected, deemed to offer comparable
treatment capability, safety, accessibility and authorized by the Commanding
Officer or first Flag Officer. A check sheet for evaluating a non-Navy Level III
recompression chamber is provided on the secure supsalv.org website under 00C3
publications.
Medical/Critical Care Facility. It is important for planners to determine the location
of the closest facility and what its capabilities are. Not all medical facilities may
be capable of dealing with the most serious emergencies. The closest critical care
facility also must be determined if the nearest medical facility is deemed inadequate.
A recompression chamber, Diving Medical Officer, and approval in accordance
with OPNAVINST 3150.27 (series) are required prior to any planned dive which
exceeds the maximum working limits.
15-3.4

Diving Procedures for EC-UBA.

15-3.4.1

Diving Methods. EC-UBA Diving methods include:

15-3.4.1.1

Single Marked Diving. Consists of a single diver with FFM marked with a
lightweight buoyant line attached to a surface float. Upon completion of a dive
requiring decompression, the diver will signal the diving supervisor that he is
ready to surface. The diving boat will then approach the surface float and recover
the diver.

15-3.4.1.2

Paired Marked Diving. Procedures for paired marked diving are identical to the
procedures for a single marked diver, but with the addition of the second diver
connected by a buddy/distance line.

NOTE:

Marked diving greatly decreases effective communication between the
diver(s) and topside support personnel.

15-3.4.1.3

Tended Diving. Tended diving consists of a single surface-tended diver or a pair

of divers using a buddy/distance line, with one diver wearing a depth-marked line
that is continuously tended at the surface.
15-3.4.1.4

Diver Training Scenarios. Multiple lines (tending lines, reference buoys, marker
floats, witness floats, detonation cord, etc.) increase the risk of entanglement and
safety while conducting EC-UBA training dive operations. To minimize this risk,
the use of a single diver in open circuit SCUBA connected to a single or buddy
lined pair of EC-UBA divers via a buddy line is authorized with no witness float
attached to either diver (ie, one instructor in SCUBA with two students in ECUBA). The visible bubbles from the single SCUBA diver will suffice for marking
or tracking the divers’ location. The use of through-water communications further
enhance safety and effectiveness of training dives. The dive limitations shall be
IAW Chapter 7, as SCUBA is now the limiting factor.

Training scenarios do not constitute a real threat. Single untended divers shall not
be used. The diver(s) shall be surface tended or marked by a buoy

CHAPTER 15 — EC-UBA Diving

15-13

EC-UBA DIVE RECORD SHEET
Diving Supervisor

Date

Water Temp

Air Temp

Table

Depth (FSW)

Schedule

EBS Oxygen Bottle Pressure

Planned Bottom Time
EBS Diluent Bottle Pressure

p0.75 / p1.3
(circle type)

Name

Repet
Group

Rig
No.

O2
Pressure

Diluent
Pressure

BATT
Percent

LS

LB

RS

TBT

Diver 1
Diver 2
Standby
Diver

Descent
Rate

Schedule Time
at Stop
Diver

Stop Depth

Standby

Actual time at Stop
Diver

Travel
Time

Remarks

Standby

20
30
40
50
60
70
80
90
100
110
120
130
140
150

Figure 15-4. EC-UBA Dive Record Sheet.

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U.S. Navy Diving Manual — Volume 4

15-3.5

Diving in Contaminated Water. Although EC-UBA’s are not designed specifically

for diving in contaminated water, as a rebreather set it does reduce the risk of
exposure through exhaust valve reflux and with a FFM it is suitable for diving in
Category 3 contaminated water. A thorough ORM analysis should be completed
to assess the level of risk associated with diving in contaminated water. Refer to
the technical manual, Guidance for Diving in Contaminated Waters (SS521-AJPRO-010) for further guidance.
15-3.6

15-4

Special diving situations by their nature require
deviations from the above configurations (ie, single untended diver, buoy-less
swimming). Mine Counter Measure (MCM) and Combat Diver operations are
unique and require specific tactics that should be maintained at the unit level.
Local instructions or directives for special diving situations shall be documented
in writing and approved by the first major command over the unit. The major
command shall review the tactics at a minimum of bi-annually, or more frequently
as during the unit’s combat certification, whichever is shorter, and documented by
cover letter.

Special Diving Situations.

PREDIVE PROCEDURES
15-4.1

Diving Supervisor Brief. A thorough, well-prepared dive briefing reinforces the

confidence level of the divers and increases safety, and is an important factor in
successful mission accomplishment. It should normally be given by the Diving
Supervisor, who will be in charge of all diving operations on the scene. The
briefing shall be given separately from the overall mission briefing and shall focus
on the diving portion of the operation, with special attention to the items shown
in Table 15-5. EC-UBA line-pull dive signals are listed in Table 15-6. Use the
specific checks in the respective EC-UBA O&M Manual. Figure 15-4 provides
a dive data sheet as an example to be used by Diving Supervisors for typical ECUBA diving.
15-4.2

Diving Supervisor Check. Prior to the dive, the Diving Supervisor must ensure

each UBA is setup properly and a predive checklist is completed. The second
phase of the Diving Supervisor check is a predive inspection conducted after the
divers are dressed (refer to the EC-UBA O & M manual). The Diving Supervisor
ensures that the UBA and related gear (life preserver, weight belt, etc.) are properly
donned, that mission-related equipment (compass, depth gauge, dive watch, buddy
lines, tactical equipment, etc.) are available, and that the UBA functions properly
before allowing the divers to enter the water. Appropriate check lists to confirm
proper functioning of the UBA are provided in the respective EC-UBA O&M
manual.

CHAPTER 15 — EC-UBA Diving

15-15

Table 15‑5. EC-UBA Dive Briefing.
A.

B.

C.

D.

Dive Plan

E.

Review of Dive Signals

1.

Operating depth

1.

2.

Dive times

2.

3.

CSMD tables or decompression tables

4.

Distance, bearing, and transit times

5.

All known obstacles or hazards

Hand signals
EC-UBA Line-Pull Dive Signals
(Table 15-5)

F.

Environment
G.

Communications
1.

Frequencies, primary/secondary

2.

Call signs

1.

Weather conditions

Emergency Procedures

2.

Water/air temperatures

1.

Symptoms of CNS O2 toxicity and CO2 buildup

3.

Water visibility

2.

4.

Tides/currents

5.

Depth of water

Review of management of CNS O2 toxicity, CO2
toxicity, hypoxia, chemical injury, unconscious
diver

6.

Bottom type

3.

UBA malfunction (refer to maintenance manual
for detailed discussion)

7.

Geographic location

4.

Lost swim pair procedures

Personnel Assignments

5.

Omitted decompression plan

1.

Dive pairs

6.

Medical evacuation plan

2.

Diving Supervisor

3.

Diving Officer

4.

Standby diver

5.

Diving medical personnel

6.

Base of operations support personnel

Special Equipment for:
1.

Divers (include thermal garments)

2.

Diving Supervisor

3.

Standby diver

4.

Medical personnel

n

Nearest appropriate chamber

n

Nearest Diving Medical Officer

n

Transportation plan

n

Recovery of other swim pairs

H.

Times for Operations

I.

Time Check

Table 15-6. EC-UBA Line-Pull Signals.

15-16

Signal

From

To

Meaning

1 Pull

Diver

Tender

Arrived at lazy shot (given on lazy shot)

7 Pulls

Diver

Tender

I have started, found, or completed work

2-3 Pulls

Diver

Tender

I have decompression symptoms.

3-2 Pulls

Diver

Tender

Breathing from EBS
(EBS UBA is functioning properly)

4-2 Pulls

Diver

Tender

Rig malfunction

2-1 Pulls

Diver
Tender

Tender
Diver

Unshackle from the lazy shot

5 Pulls

Diver

Tender

I have exceeded the planned depth of the dive.
(This is followed by 1 pull for every 5 fsw of
depth the planned depth was exceeded)

U.S. Navy Diving Manual — Volume 4

15-5

DESCENT

The maximum descent rate is 60 feet per minute. During descent, the UBA will
automatically compensate for increased water pressure and provide an adequate
volume of gas for breathing. During descent the oxygen partial pressure will increase
as oxygen is added to the breathing mixture as a portion of the diluent. It may take
from 2 to 5 minutes to consume the additional oxygen added by the diluent during
descent. While breathing down the ppO2, the diver should continuously monitor the
primary and secondary displays until the ppO2 returns to the control setpoint level.
CAUTION		

There is an increased risk of CNS oxygen toxicity when diving a 1.3 pO2
EC-UBA compared to diving a 0.75 pO2 EC-UBA, especially during the
descent phase of the dive. Diving supervisors and divers should be aware
that oxygen partial pressures of 1.6 ata or higher may be temporarily
experienced during descent on N2O2 dives deeper than 120 fsw (21%
oxygen diluent) and on HeO2 dives deeper than 200 fsw (12% oxygen
diluent) Refer to Chapter 3 for more information on recognizing and
preventing CNS oxygen toxicity.

The 1.3 pO2 EC-UBA should transition from 0.75 pO2 to 1.3 pO2 at 33 fsw during
descent. The diver should verify this transition by monitoring his secondary
display. If there is no indication of this transition with continued descent past 40
fsw, the dive should be terminated and the diver should ascend to the surface in
accordance with the appropriate decompression schedule.
15-6

UNDERWATER PROCEDURES
15-6.1

General Guidelines. The divers should adhere to the following guidelines as the

dive is conducted:
WARNING		

Failure to adhere to these guidelines could result in serious injury or
death.

n Monitor primary and secondary display frequently.
n The diver should not add oxygen on descent, except as part of an emergency
procedure, or at any time while on the bottom due to the increased risk of CNS
oxygen toxicity.
n Wear adequate thermal protection.
n Know and use the proper amount of weights for the thermal protection worn
and the equipment carried.
n Check each other’s equipment carefully for leaks.
n Do not exceed the briefed limitations for the dive.
n Minimize gas loss from the UBA (avoid mask leaks and frequent depth changes,
if possible).
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15-17

n Maintain frequent visual or touch checks with buddy.
n Be alert for symptoms suggestive of a medical disorder.
n Use tides and currents to maximum advantage.
15-6.2

At Depth. If the EC-UBA is operating properly at depth, no adjustments will be

required.

The ppO2 control system will add oxygen as necessary to ensure the oxygen level
remains at the set-point. Monitor the following displays in accordance with the
respective EC-UBA O&M manual:
n Primary Display. Check the primary display frequently to ensure that the oxygen
level remains at the set-point during normal activity at a constant depth.
n Secondary Display. Check the secondary display every 2-3 minutes to ensure
that all sensors are consistent with the primary display and the battery voltages
are properly indicating.
n High-Pressure Indicators. Check the oxygen and diluent pressure indicators
frequently to ensure the gas supply is adequate to complete the dive.
15-7

ASCENT PROCEDURES

The maximum ascent rate for any EC-UBA is 30 feet per minute (fpm). During
ascent, when water pressure decreases, the ppO2 in the breathing gas mixture may
decrease faster than O2 can be added via the O2 addition valve. This is a normal
reaction to the decrease in partial pressure and is an indication that the UBA is
functioning correctly.
n Upon arrival at the first decompression stop allow the EC-UBA to stabilize. If
after four minutes of arrival at the first stop the EC-UBA has not stabilized, the
diver should initiate the appropriate emergency procedure for low ppO2.
15-8

DECOMPRESSION PROCEDURES

Standard U.S. Navy decompression tables cannot be used with a closed-circuit
UBA since the ppO2 remains constant at a preset level regardless of depth. The
decompression Tables 15-8 through 15-17 have been specifically developed and
tested for the EC-UBA.
15-8.1

Monitoring ppO2. During decompression, it is very important to constantly

monitor the secondary display and ensure ppO2 is maintained as closely as
possible. Always use the appropriate decompression table when surfacing, even if
UBA malfunction has significantly altered the ppO2.

NOTE

15-18

Surface decompression is not authorized for EC-UBA operations.
Appropriate surface decompression tables have not been developed for
constant EC-UBA closed-circuit diving.
U.S. Navy Diving Manual — Volume 4

15-8.2

Rules for Using EC-UBA Decompression Tables.

WARNING		

The diving supervisor must ensure selection of both the proper EC-UBA
set-point table, and proper diluent table for the dive being conducted.

NOTE

The rules for using the decompression tables are the same for any
set-point on both nitrogen and helium; however, the tables are NOT
interchangeable.

These tables are designed to be used with the EC-UBA.
n For HeO2 dives, flush the UBA well with helium-oxygen using the purge
procedure given in the respective O&M manual.
n Tables are grouped by depth and within each depth group is an exceptional
exposure line. These tables are designed to be dived to the exceptional
exposure line. Schedules below the exceptional exposure line are provided
for unforeseen circumstances when a diver might experience an inadvertent
downward excursion or for an unforeseen reason overstay the planned bottom
time.
n Tables/schedules are selected according to the maximum depth obtained during
the dive and the bottom time (time from leaving the surface to leaving the
bottom).
n General rules for using these tables are the same as for air decompression
tables, and include the use of the Residual Nitrogen Time (RNT) and Residual
Helium Time (RHT) exception rules when calculating the table and schedule
for repetitive dives.
NOTE

The repetitive group designators are not interchangeable between the
nitrogen and helium decompression tables. There are no procedures
for performing repetitive dives when the inert gas in the diluent mixture
changes between dives.
1. Enter the table at the listed depth that is exactly equal to or is next greater than

the maximum depth attained during the dive.

2. Select the bottom time from those listed for the selected depth that is exactly

equal to or is next greater than the bottom time of the dive.

3. Never attempt to interpolate between decompression schedules.
4. Use the decompression stops listed for the selected bottom time.
5. Ensure that the diver’s chest is maintained as close as possible to each

decompression depth for the number of minutes listed.

6. Maximum ascent rate is 30 feet per minute. The rules for compensating for

variations in the rate of ascent are identical to those for air diving (see Chapter
9).

CHAPTER 15 — EC-UBA Diving

15-19

7. Begin timing the first stop when the diver arrives at the stop. For all subsequent

stops, begin timing the stop when the diver leaves the previous stop. Ascent
time between stops is included in the subsequent stop time.

8. When diving a 1.3 ata ppO2 set-point EC-UBA, the last stop taken will be at 20

fsw. There are no stops shallower than 20 fsw allowed for 1.3 ata ppO2 diving
as the primary electronics will switch from 1.3 ata ppO2 to 0.75 ata ppO2 upon
ascent above 13 fsw.

9. Always use the appropriate decompression table when surfacing even if UBA

malfunction has significantly altered ppO .

10. In emergency situations (e.g., UBA flood-out or failure), immediately ascend to

the first decompression stop according to the original decompression schedule
if deeper than the first stop, and shift to the Emergency Breathing System
(EBS).

11. When selecting the proper decompression table, all dives within the past 18

hours must be considered. Repetitive dives are allowed provided the same
diluent is used as the previous dives. Refer to the following tables and figures.

n Table 15-8 for No Decompression Limits and Repetitive Group Designators
for 1.3 ata ppO2 N2O2 Dives.
n Table 15-9 for Residual Nitrogen Timetable for 1.3 ata ppO2 N2O2 Dives.
n Figure 15-8 for Repetitive Dive Worksheet for 1.3 ata ppO2 N2O2 Dives.
n Table 15-10 for 1.3 ata ppO2 N2O2 Decompression Tables.
n Table 15-11 for No Decompression Limits and Repetitive Group Designators
for 1.3 ata ppO2 HeO2 Dives.
n Table 15-12 for Residual Helium Timetable for 1.3 ata ppO2 HeO Dives.
2

n Figure 15-9 for Repetitive Dive Worksheet for 1.3 ata ppO2 HeO Dives.
2

n Table 15-13 for 1.3 ata ppO2 HeO Decompression Tables.
2

n Table 15‑14 for No-Decompression Limits and Repetitive Group
Designation Table for 0.75 ata ppO2 N2O2 Dives.
n Table 15‑15 for Residual Nitrogen Timetable for Repetitive 0.75 ata ppO2
N2O2 Dives.
n Figure 15‑10 for Dive Worksheet for Repetitive 0.75 ata ppO2 N2O2 Dives.
n Table 15‑16 for 0.75 ata ppO2 in N2O2 Decompression Tables.
n Table 15-17 for 0.75 ata ppO2 in HeO2 Decompression Tables.

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U.S. Navy Diving Manual — Volume 4

Figure 15-5. Typical EC-UBA Emergency Breathing System.

12. The partial pressure of inert gas (nitrogen or helium) in the EC-UBA at depths

down to 15 fsw could be lower than the partial pressure of nitrogen in air at the
surface. A diver diving to these depths, therefore, will lose rather than gain inert
gas during the dive. Accordingly, the diver does not acquire a repetitive group
designator when making these shallow dives. If the dive is a repetitive dive to
15 fsw or shallower, the diver will lose more inert gas during the repetitive dive
than if he remained on the surface. The dive can be considered the equivalent
of remaining on the surface for the duration of the dive. The repetitive group
designator at the end of the repetitive dive can be determined by adding the
bottom time of the repetitive dive to the preceding surface interval, then using
the surface interval credit table to determine the ending repetitive group.

13. The RNT and RHT exception rules apply to repetitive EC-UBA diving. The

RNT and RHT exception rules read identically. The only difference is the table
to which the rule refers: Tables 15-9 and 15-15 for the RNT exception rule and
Table 15-12 for the RHT exception rule. Determine the table and schedule for
the repetitive dive by adding the bottom times and taking the deepest depth of
all the EC-UBA dives in the series, including the planned repetitive dive. If
the resultant table and schedule require less decompression than the table and
schedule obtained using the repetitive dive worksheet, it may be used instead
of the worksheet table and schedule.

During descent, the 1.3 ppO2 EC-UBA switches from the 0.75 ata mode to
the 1.3 ata mode at 33 fsw ± 2 fsw. The decompression tables assume that
the diver is in the 0.75 ata mode up to a depth of 35 fsw. The RNT and RHT
exception rules can be used as written above when all the dives in the series are
to 35 fsw and shallower (PO2 = 0.75 ata) or when all the dives in the series are

CHAPTER 15 — EC-UBA Diving

15-21

deeper than 35 fsw (PO2 = 1.3 ata). However, when some dives are shallower
than 35 fsw and others are deeper, the shallow 0.75 ata dives must first be
converted to their 1.3 ata equivalent depth before the deepest depth in the series
is determined. The equivalent depth on 1.3 ata can be obtained by adding 20
fsw to the depth of the dive on 0.75 ata.
14. Repetitive nitrogen-oxygen dives between EC-UBA and open circuit air dives,

and vice versa, follow the same rules for determining RNT. Using the RNT
designator from the dive method just completed, enter the new dive method
surface interval table and complete the new repet designator steps.
The RNT exception rule does apply to Air-1.3 ata ppO2 EC-UBA repetitive
diving. If all the 1.3 ata ppO2 EC-UBA dives in the series, including the
repetitive dive, are to 35 fsw or shallower, convert the depth(s) of the air dive(s)
in the series to the equivalent depth on 0.75 ata before taking the deepest depth
in the series. If any of the 1.3 ata ppO2 EC-UBA dives in the series, including
the repetitive dive, are to a depth greater than 35 fsw, convert the depth(s) of
the air dive(s) in the series to the equivalent depth on 1.3 ata before taking the
deepest depth in the series. Equivalent Depth on 0.75 ata = (0.79 x Depth on
Air) + 18 fsw. Equivalent Depth on 1.3 ata = (0.79 x Depth on Air) + 36 fsw.

WARNING:		

These procedures cannot be used to make repetitive dives on air
following EC-UBA helium-oxygen dives.
15. Navy Dive Computer (NDC) use is authorized and encouraged with the EC-

UBA. Use with EC-UBA shall follow the guidance in Appendix 2B, or other
NAVSEA authorized diving procedures.

15-8.3

PPO2 Variances. The ppO2 in the EC-UBA is expected to vary slightly +/- 0.15 ata

from set-point for irregular brief intervals. This does not constitute a malfunction.
When addition of oxygen to the UBA is manually controlled, ppO2 should be
maintained in accordance with techniques and emergency procedures listed in the
respective O&M manual.
The Diving Supervisor and medical personnel should recognize that a diver who
has been breathing a mixture with ppO2 lower than -0.15 ata from current set
point for any length of time may have a greater risk of developing decompression
sickness. Such a diver requires observation after surfacing, but need not be treated
unless symptoms of decompression sickness occur.

15-8.4

Emergency Breathing System (EBS). The Emergency Breathing System

(Figure 15-5) provides an alternate breathing source for decompressing diver(s)
in the event of a EC-UBA failure. The EBS consists of an EC-UBA in the same
configuration mounted on the Emergency Breathing System frame assembly and
charged with the same diluent gas as for the planned dive.

15-8.4.1

EBS Deployment Procedures. Regardless of the depth of the first decompression

stop dives using the 1.3 ata ppO2 EC-UBA must lower the EBS to at least 40 fsw
to allow the hydrostatic switch in the primary electronics to switch from 0.75 ata
ppO2 to 1.3 ata ppO2 . The EBS can then be raised or lowered to ten feet below the
first decompression stop. Refer to O&M Manual for detailed EBS procedures. It is

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U.S. Navy Diving Manual — Volume 4

recommended to lower EBS to 50 fsw if the first decompression stop is shallower
than 40 fsw. This allows for topside personnel to track delays in ascent deeper than
50 fsw.
When diving in excessive currents, attach a tag line to the EBS frame on the side
facing current, lower EBS maintaining slight tension. Once EBS is at correct depth,
ensure tag line tends into the current and secure at opposite end of dive boat from
EBS winch. Tag line will prevent EBS from spinning and maintain a straight up
and down position. The tag line may also be used for line-pull signals.
15-8.4.2

EBS Ascent Procedures. As a diver prepares to leave bottom, diver movement

should be in the direction of the tend. When tend is straight up and down, topside
will marry EBS and tending line with weighted carabineer or other appropriate
attachment device and allow to drop to EBS. When diver is directed to leave
bottom, he will be able to follow the tend directly to EBS.
15-9

MULTI-DAY DIVING FOR 1.3 ATA PPO2 EC-UBA

Repetitive exposure to an oxygen partial pressure of over 1.0 ata over a multi-day
period may result in the gradual development of pulmonary oxygen toxicity and/
or changes in visual acuity. To minimize the possibility of adverse effects from
oxygen toxicity during multi-day diving with the EC-UBA, the diver shall adhere
to the following rules:
n Limit total 1.3 ata ppO2 dive time to a maximum of 4 hours per day.
n Limit total 1.3 ata ppO2 dive time to a maximum of 16 hours per week.
n EC-UBA 0.75 ata mode is excluded from the above totals.
n If symptoms of pulmonary or visual oxygen toxicity develop at any time during
a multi-day mission, stop diving until all symptoms have resolved and the diver
remains symptom-free for a minimum of 24 hours.
n If more dive time is required to accomplish a specific mission, contact NAVSEA
00C3 for additional guidance.
15-10 ALTITUDE DIVING PROCEDURES AND FLYING AFTER DIVING

Ascent to altitude following any dive at sea level will increase the risk of
decompression sickness if the interval on the surface before ascent is not long
enough to permit excess nitrogen or helium to be eliminated from the body. To
determine the safe surface interval before ascent, take the following steps:
n Nitrogen-Oxygen Dives
1. Determine the highest repetitive group designator obtained in the previous 24-

hour period using either Table 15-9 or Table 15-15.

CHAPTER 15 — EC-UBA Diving

15-23

2. Using the highest repetitive group designator, enter Table 9-6 in Chapter 9.

Read across the row to the altitude that is exactly equal to or next higher than
the planned change in altitude to obtain the safe surface interval.

n Helium-Oxygen Dives
1. For no-decompression dives with total bottom times, including repetitive dives,

less than 2 hours, wait 12 hours on the surface before ascending to altitude.

2. For no-decompression dives with bottom times, including repetitive dives,

greater than 2 hours or for decompression dives, wait 24 hours on the surface
before ascending to altitude.

The EC-UBA decompression procedures may be used for diving at altitudes up to
1000 feet without modification. For diving at altitudes above 1000 feet, contact
NAVSEA 00C3 for guidance.
15-11

POSTDIVE PROCEDURES

Postdive procedures shall be completed in accordance with the appropriate postdive
checklists in the EC-UBA O&M manual.
15-12

MEDICAL ASPECTS OF CLOSED-CIRCUIT MIXED-GAS UBA

When using an EC-UBA, the diver is susceptible to the usual diving-related
illnesses (i.e., decompression sickness, arterial gas embolism, barotraumas, etc.).
Only the diving disorders that merit special attention for EC-UBA divers are
addressed in this chapter. Refer to Chapter 3 for a detailed discussion of diving
related physiology and related disorders.
15-12.1

Central Nervous System (CNS) Oxygen Toxicity. High pressure oxygen poison-

ing is known as CNS oxygen toxicity. CNS oxygen toxicity is not likely to occur at
oxygen partial pressures below 1.3 ata, though relatively brief exposure to partial
pressures above this, when it occurs at depth or in a pressurized chamber, can
result in CNS oxygen toxicity causing CNS-related symptoms.

15-12.1.1

Causes of CNS Oxygen Toxicity. Factors that increase the likelihood of CNS

oxygen toxicity specific to the EC-UBA are:
n Increased partial pressure of oxygen
n Increased time of exposure
n Prolonged immersion
n Stress from strenuous physical exercise

n Carbon dioxide buildup. The increased risk for CNS oxygen toxicity may occur
even before the diver is aware of any symptoms of carbon dioxide buildup.

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U.S. Navy Diving Manual — Volume 4

Rapid descent in an EC-UBA may not allow the oxygen already in the circuit to
be consumed fast enough resulting in a high ppO2. When high levels of oxygen
are displayed, the descent must be slowed. If the diver is in less than 20 fsw, little
danger of oxygen toxicity exists. If the diver is deeper than 20 fsw, and an ppO2 of
1.45 ata or higher persists within the UBA for a period of 15 consecutive minutes
this condition should be treated as a malfunction of the UBA and the appropriate
emergency procedures should be followed.
15-12.1.2

Symptoms of CNS Oxygen Toxicity. Refer to Chapter 3.

15-12.1.3

Treatment of Nonconvulsive Symptoms. If non-convulsive symptoms of CNS

oxygen toxicity occur, action must be taken immediately to lower the oxygen
partial pressure. Such actions include:
n Ascend. Dalton’s law will lower the oxygen partial pressure.
n Add diluent to the breathing loop.
n Secure the oxygen cylinder if oxygen addition is uncontrolled.

Though an ascent from depth will lower the partial pressure of oxygen, the diver
may still suffer other or worsening symptoms. The divers should notify the Diving
Supervisor and terminate the dive.
15-12.1.4

Treatment of Underwater Convulsion. The following steps should be taken when

treating a convulsing diver:

1. Assume a position behind the convulsing diver. Release the victim’s weight

belt only as a last resort if progress to the surface is significantly impeded.

2. Ensure the FFM is on and clear of water. If using a mouthpiece, leave it in

the victim’s mouth. If the FFM is off, or the mouthpiece is not in his mouth,
do not attempt to replace it; however, if time permits, ensure that the FFM
or mouthpiece is switched to the SURFACE position to prevent unnecessary
negative buoyancy from a flooded UBA.

3. Grasp the victim around his chest above the UBA or between the UBA and

his body. If difficulty is encountered in gaining control of the victim in this
manner, the rescuer should use the best method possible to obtain control.

4. Ventilate the UBA with diluent to lower the ppO2 convulsion subsides. Monitor

secondary for ppO2 drop.

5. Make a controlled ascent to the first decompression stop, maintaining a slight

pressure on the diver’s chest to assist exhalation.

n If the diver regains consciousness, continue with appropriate decompression.
n If the diver remains incapacitated, surface at a moderate rate, establish an
airway, and treat for symptomatic omitted decompression as outlined in
paragraph 15-12.6.

CHAPTER 15 — EC-UBA Diving

15-25

n Frequent monitoring of the primary and secondary displays as well as the
oxygen and diluent-bottle pressure gauges will keep the diver well informed
of his breathing gas and rig status.
6. If additional buoyancy is required, activate the victim’s life jacket. The rescuer

should not release his own weight belt or inflate his life jacket.

7. Upon reaching the surface, inflate the victim’s life jacket if not previously

done.

8. Remove the victim’s FFM or mouthpiece and switch the valve to SURFACE to

prevent the possibility of the rig flooding and weighing down the victim.

9. Signal for emergency pickup.
10. Ensure the victim is breathing. Mouth-to-mouth breathing may be initiated if

necessary.

11. If the diver surfaces in an unconscious state, follow the guidance in Section

17-3.

12. If an upward excursion occurred during the actual convulsion, transport to the

nearest appropriate chamber and have the victim evaluated by an individual
trained to recognize and treat diving-related illness.

15-12.1.5

Prevention of CNS Oxygen Toxicity. All predive checks must be performed to

ensure proper functioning of the oxygen sensors and the oxygen-addition valve.
Frequent monitoring of both the primary and secondary displays will help ensure
that the proper ppO2 is maintained.
15-12.1.6

Off-Effect. The off-effect, a hazard associated with CNS oxygen toxicity, may

occur several minutes after the diver comes off gas or experiences a reduction of
oxygen partial pressure. The off-effect is manifested by the onset or worsening of
CNS oxygen toxicity symptoms. Whether this paradoxical effect is truly caused
by the reduction in partial pressure or whether the association is coincidental is
unknown.

15-12.2

15-12.3

15-12.3.1

Pulmonary Oxygen Toxicity. Pulmonary oxygen toxicity can result from prolonged
exposure to elevated partial pressures of oxygen. Follow the guidance in paragraph
15-9 for multi- day exposures to oxygen. Chapter 3 provides a detailed description
of pulmonary oxygen toxicity.
Oxygen Deficiency (Hypoxia). Hypoxia is an abnormal deficiency of oxygen in
the arterial blood in which the partial pressure of oxygen is too low to meet the
metabolic needs of the body. Chapter 3 contains an in-depth description of this
disorder. Although all cells in the body need oxygen, the initial symptoms of
hypoxia are a manifestation of central nervous system dysfunction.
Causes of Hypoxia. The primary cause of hypoxia for an EC-UBA diver is failure

of the oxygen addition valve or primary electronics. However, during a rapid
ascent Dalton’s law may cause the ppO2 to fall faster than can be compensated
for by the oxygen-addition system. If, during ascent, low levels of oxygen are

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U.S. Navy Diving Manual — Volume 4

displayed, slow the ascent and add oxygen if necessary. Depletion of the oxygen
supply or malfunctioning oxygen sensors can also lead to a hypoxic gas mixture.
15-12.3.2

Symptoms of Hypoxia. Hypoxia may have no warning symptoms prior to loss

of consciousness. Other symptoms that may appear include confusion, loss of
coordination, dizziness, and convulsion. It is important to note that if symptoms
of unconsciousness or convulsion occur at the beginning of a closed-circuit dive,
hypoxia, not oxygen toxicity, is the most likely cause.
15-12.3.3

15-12.3.4

Treating Hypoxia. If symptoms of hypoxia develop, the diver must take immediate
action to raise the oxygen partial pressure. If unconsciousness occurs, the buddy
diver should add oxygen to the rig while monitoring the secondary display. If the
diver does not require decompression, the buddy diver should bring the afflicted
diver to the surface at a moderate rate, remove the mouthpiece or mask, and have
him breathe air. If the event was clearly related to hypoxia and the diver recovers
fully with normal neurological function shortly after breathing surface air, the
diver does not require treatment for arterial gas embolism.
Treatment of Hypoxic Divers Requiring Decompression. If the divers require
decompression, the buddy diver should bring the afflicted diver to the first
decompression stop.

n If consciousness is regained, continue with normal decompression.
n If consciousness is not regained, ascend to the surface at a moderate rate (not to
exceed 30 fpm), establish an airway, administer 100-percent oxygen, and treat
for symptomatic omitted decompression as outlined in paragraph 15-12.6. If
possible, immediate assistance from the standby diver should be obtained and
the unaffected diver should continue normal decompression.
15-12.4

Carbon Dioxide Toxicity (Hypercapnia). Carbon dioxide toxicity, or hypercapnia,

is an abnormally high level of carbon dioxide in the blood and body tissues.
15-12.4.1

Causes of Hypercapnia. Hypercapnia is generally a result of the failure of the

carbon dioxide-absorbent material. The failure may be a result of channeling,
flooding or saturation of the absorbent material. Skip breathing or controlled
ventilation by the diver, which results in an insufficient removal of CO2 from the
diver’s body, may also cause hypercapnia.
An excessive work rate can also cause a buildup of CO2. Unlike open circuit
diving where a diver can ventilate the rig, the only recourse is to decrease workload
until symptoms subside.
15-12.4.2

Symptoms of Hypercapnia. Symptoms of hypercapnia are:

n Increased rate and depth of breathing
n Labored breathing (similar to that seen with heavy exercise)

CHAPTER 15 — EC-UBA Diving

15-27

n Headache
n Confusion
n Unconsciousness
WARNING		

Hypoxia and hypercapnia may give the diver little or no warning prior to
onset of unconsciousness.

Symptoms are dependent on the partial pressure of carbon dioxide, which is a
function of both the fraction of carbon dioxide and the absolute pressure. Thus,
symptoms would be expected to increase as depth increases. The presence of a high
partial pressure of oxygen may also reduce the early symptoms of hypercapnia.
Elevated levels of carbon dioxide may result in an episode of CNS oxygen toxicity
on a normally safe dive profile.
15-12.4.3

Treating Hypercapnia. If symptoms of hypercapnia develop, the diver should:

n Immediately stop work and take several deep breaths.
n Increase lung ventilation if skip-breathing is a possible cause.
n Ascend. This will reduce the partial pressure of carbon dioxide both in the rig
and the lungs, and also increase the ease of breathing as gas density decreases.
n If symptoms do not rapidly abate, the diver should abort the dive.
n During ascent, while maintaining a vertical position, the diver should activate
his bypass valve, adding fresh gas to his UBA. If the symptoms are a result of
canister floodout, an upright position decreases the likelihood that the diver
will sustain chemical injury.
n If unconsciousness occurs at depth, the same principles of management for
underwater convulsion as described in paragraph 15-12.1.4 apply.
15-12.4.4

Prevention of Hypercapnia. To minimize the risk of hypercapnia:

n Use only an approved carbon dioxide absorbent in the UBA canister.
n Follow the prescribed canister-filling procedure to ensure that the canister is
correctly packed with carbon dioxide absorbent.
n Dip test the UBA carefully before the dive. Watch for leaks that may result in
canister floodout.
n Do not exceed canister duration limits for the water temperature.
n Ensure that the one-way valves in the supply and exhaust hoses are installed
and working properly.

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n Swim and work at a relaxed, comfortable pace. Avoid excessive work rates.
n Avoid skip-breathing. There is no advantage to this type of breathing in a
closed-circuit rig and it may cause elevated blood carbon dioxide levels even
with a properly functioning canister.
15-12.5

Chemical Injury. The term chemical injury refers to the introduction of a caustic

solution from the carbon dioxide scrubber of the UBA into the upper airway of a
diver.
15-12.5.1

Causes of Chemical Injury. A caustic alkaline solution results when water

leaking into the canister comes in contact with the carbon dioxide absorbent. The
water may enter through a leak in the breathing loop or incorrect position of the
mouthpiece rotary valve during a leak check. When the diver is in a horizontal
or head down position, this solution may travel through the inhalation hose and
irritate or injure the upper airway.
15-12.5.2

15-12.5.3

Symptoms of Chemical Injury. Before actually inhaling the caustic solution, the
diver may experience labored breathing or headache, which are symptoms of
carbon dioxide buildup in the breathing gas. This occurs because an accumulation
of the caustic solution in the canister may be impairing carbon dioxide absorption.
If the problem is not corrected promptly, the alkaline solution may travel into the
breathing hoses and consequently be inhaled or swallowed. Choking, gagging, foul
taste, and burning of the mouth and throat may begin immediately. This condition
is sometimes referred to as a “caustic cocktail.” The extent of the injury depends
on the amount and distribution of the solution.
Management of a Chemical Incident. If the caustic solution enters the mouth,

nose, or face mask, the diver must take the following steps:
n Immediately assume an upright position in the water.
n Depress the manual diluent bypass valve continuously.

n If the dive is a no-decompression dive, make a controlled ascent to the surface,
exhaling through the nose to prevent over pressurization.
n If the dive requires decompression, shift to the EBS or another alternative
breathing supply. If it is not possible to complete the planned decompression,
surface the diver and treat for omitted decompression as outlined in paragraph
15-12.6.
Using fresh water, rinse the mouth several times. Several mouthfuls should then be
swallowed. If only sea water is available, rinse the mouth but do not swallow. Other
fluids may be substituted if available, but the use of weak acid solutions (vinegar or
lemon juice) is not recommended. Do not attempt to induce vomiting.
A chemical injury may cause the diver to have difficulty breathing properly on
ascent. He should be observed for signs of an arterial gas embolism and should

CHAPTER 15 — EC-UBA Diving

15-29

be treated if necessary. A victim of a chemical injury should be evaluated by a
physician as soon as possible. Respiratory distress which may result from the
chemical trauma to the air passages requires immediate hospitalization.
15-12.5.4

15-12.6

15-12.6.1

Prevention of Chemical Injury. Chemical injuries are best prevented by the
performance of a careful dip test during predive set-up to detect any system leaks.
Special attention should also be paid to the position of the mouthpiece rotary valve
upon water entry and exit to prevent the entry of water into the breathing loop.
Additionally, dive buddies should perform a careful leak check on each other
before leaving the surface at the start of a dive.
Omitted Decompression. Certain emergencies may interrupt or prevent specified
decompression. UBA failure, exhausted diluent or oxygen gas supply, and bodily
injury are examples that constitute such emergencies. Omitted decompression
must be made up to avoid later difficulty. Table 15-7 contains specific guidance for
the initial management of omitted decompression in an asymptomatic EC-UBA
diver.
At 20 fsw. If the deepest decompression stop omitted is 20 fsw, the diver may be
returned to the water stop at which the omission occurred.

n If the surface interval was less than 1 minute, add 1 minute to the stop time and
resume the planned decompression at the point of interruption.
n If the surface interval was greater than 1 minute and less than 5 minutes,
compute a new decompression schedule by multiplying the 20-foot stop time
by 1.5.
n If the surface interval is greater than 5 minutes and a chamber is available within
60 minutes treat on Treatment Table 6. In instances where a recompression
chamber is not available within 60 minutes return to 20 fsw and multiply 20
fsw stop time by 1.5 and resume decompression.
15-12.6.2

Deeper than 20 fsw. If the deepest decompression stop omitted is deeper than 20

fsw, a more serious situation exists. The use of a recompression chamber available
within 60 minutes is mandatory.

n If less than 30 minutes of decompression were missed and the surface interval
is less than 5 minutes, treat the diver on Treatment Table 5.
n If less than 30 minutes of decompression were missed but the surface interval
exceeds 5 minutes, treat the diver on Treatment Table 6.
n If more than 30 minutes of decompression were missed, treat the diver on
Treatment Table 6 regardless of the length of the surface interval.

15-30

U.S. Navy Diving Manual — Volume 4

Table 15-7. Initial Management of Asymptomatic Omitted Decompression EC-UBA Diver.
Action

Deepest
Decompression
Stop Omitted

Decompression
Status

Surface
Interval

None

No Decompression
stops required

NA

Observe on surface for 1 hour.

<1 min.

Return to 20 fsw. Increase 20 fsw stop time by
1 minute. Resume planned decompression at
the point of schedule interruption.

1-5 min.

Return to 20 fsw. Multiply 20 fsw stop time by
1.5. Resume decompression. (Note 2)

>5 min.

Treatment Table 6

0-5 min.

Treatment Table 5

20 fsw (Note 1)

Deeper than 20
fsw (Note 1)

Decompression stop
required

Decompression stop
required
(<30 min. missed)
Decompression stop
required
(>30 min. missed)

Chamber Available
within 60 minutes

>5 min

Treatment Table 6

Any

Treatment Table 6

Chamber Not Available
within 60 minutes

Return to 20 fsw. Multiply
20 fsw stop time by 1.5.
Resume decompression.
Descend to the deepest
stop omitted. Multiply all
stops 40 fsw and
shallower by 1.5. Resume decompression.

Note 1: When diving 1.3 ata ppO2 EC-UBA, ff the diver is returned to an omitted decompression stop that
is shallower than 33 feet, then the diver must manually add oxygen to his UBA to maintain 1.3 ata ppO2.
Alternately, the diver may elect to descend to a maximum of 40 fsw to re-transition the EC-UBA to 1.3
ppO2 before returning to the missed stop.
Note 2: If a recompression chamber is immediately available on the dive station, recompress the diver to
20 fsw in the chamber rather than in the water. Place the diver on 100% oxygen upon arrival at 20 fsw.
Multiply the 20 fsw stop time by 1.5 and resume decompression.

15-12.6.3

Deeper than 20 fsw Recompression Chamber Not Available Within 60 Minutes. If
the deepest decompression stop omitted is deeper than 20 fsw and a recompression
chamber is not available within 60 minutes, recompression in the water is
required. Recompress the diver in the water using the appropriate decompression
table. Descend to the deepest decompression stop omitted and repeat this stop in
its entirety. Complete all decompression on the original schedule, lengthening all
stops 40 fsw and shallower by multiplying the stop time by 1.5. If the deepest
stop was 40 fsw or shallower, this stop should also be multiplied by 1.5. When
recompression in the water is required, keep the surface interval as short as
possible. The diver’s UBA must be checked to ensure that it will sustain the diver
for the additional decompression obligation. Switching to a standby UBA may be
necessary so that the decompression time will not be compromised by depletion of
gas supplies or carbon dioxide-absorbent failure. Maintain depth control, keep the
diver at rest, and provide a buddy diver.

CHAPTER 15 — EC-UBA Diving

15-31

15-12.6.4

Evidence of Decompression Sickness or Arterial Gas Embolism. If the diver

shows evidence of decompression sickness or arterial gas embolism before
recompression for omitted decompression can be carried out, immediate treatment
using the appropriate oxygen or air treatment table is essential. Guidance for table
selection and use is given in Chapter 17. Symptoms that develop during treatment
of omitted decompression should be managed in the same manner as recurrences
during treatment.
15-12.7

Decompression Sickness in the Water. Decompression sickness may develop in

the water during EC-UBA diving. The symptoms of decompression sickness may
be joint pain or may be more serious manifestations such as numbness, loss of
muscular function, or vertigo.
Managing decompression sickness in the water will be difficult in the best of
circumstances. Only general guidance can be presented here. Management
decisions must be made on site, taking into account all known factors. The advice
of a Diving Medical Officer should be sought whenever possible.

15-12.7.1

Diver Remaining in Water. If prior to surfacing the diver signals that he has

decompression sickness but feels that he can remain in the water:

1. Dispatch the standby diver to assist.
2. Have the diver descend to the depth of relief of symptoms in 10-fsw increments,

but no deeper than two increments (i.e., 20 fsw).

3. Compute a new decompression profile by multiplying all stops by 1.5. If

recompression went deeper than the depth of the first stop on the original
decompression schedule, use a stop time equal to 1.5 times the first stop in
the original decompression schedule for the one or two stops deeper than the
original first stop.

4. Ascend on the new profile.
5. Lengthen stops as needed to control symptoms.
6. Upon surfacing, transport the diver to the nearest appropriate chamber. If he

is asymptomatic, treat on Treatment Table 5. If he is symptomatic, treat in
accordance with the guidance given in Chapter 17.

15-12.7.2

Diver Leaving the Water. If the diver indicates that he has decompression sickness
and feels he cannot safely remain in the water:
1. Surface the diver at a moderate rate (not to exceed 30 fsw/min).
2. Recompress the diver immediately at the closest available chamber and treat in

accordance with Chapter 17.

15-13 EC-UBA Diving Equipment Reference Data

Figures 15-6 and 15-7 outlines the capabilities and logistical requirements of the
two currently approved EC-UBA, the MK 16 MOD1 UBA and MK 16 MOD0.
Minimum required equipment for the pool phase of diving conducted at Navy
diving schools and EC-UBA RDT&E commands may be modified as necessary.
15-32

U.S. Navy Diving Manual — Volume 4

Any modification to the minimum required equipment listed herein must be noted
in approved lesson training guides or SOPs.

MK 16 MOD 1 UBA General
Characteristics

Disadvantages:
1.

Extended decompression requirement for
long bottom times or deep dives.

Principle of Operation:

2.

Limited physical and thermal protection

Self-contained closed-circuit constant 1.3 ppO2
system

3.

No voice communications (unless FFM
used)

4.

Extensive predive/postdive procedures

Minimum Equipment:
Restrictions:
1.

An approved Life Preserver or Buoyancy
Compensator (BC). When using an approved
BC, a Full Face Mask is required.

2.		

Dive knife

3.		

Swim fins

4.		

Face mask or full face mask (FFM)

5.		

Weight (as required)

6.		

Dive watch or Dive Timer/Depth Gauge (DT/
DG) (as required)

7.		

Depth gauge or DT/DG (as required)

8.

NDC (as required)

Principal Applications:
1.

EOD operations

2.

Search and inspection

3.

Light repair and recovery

4.

Special Warfare

Working Limit:
150 fsw N2O2
300 fsw HeO2

Operational Considerations:
1.

Dive team (Table 15-2)

2.

Safety boat(s) required

3.

1.3 ppO2 decompression schedule must
be used or p1.3 NDC.
Due to the hydrostatic effects that are
inherent with a back mounted counter
lung, use is restricted to an oxygen
consumption rate of 1.2 l/min.

4.

Advantages:
1.

Minimal surface bubbles

2.

Optimum efficiency of gas supply

3.

Portability

4.

Excellent mobility

5.

Communications (when used with FFM)

6.

Modularized assembly

7.

Low magnetic signature (lo-mu)
(EOD version)

8.

Low acoustic signature

Figure 15-6. MK 16 MOD 1 UBA General Characteristics.

CHAPTER 15 — EC-UBA Diving

15-33

MK 16 MOD 0 UBA General
Characteristics

Disadvantages:

Principle of Operation:

2.
3.

1.

Extended decompression requirement for
long bottom times or deep dives.
Limited physical and thermal protection
No voice communications (unless FFM
used)
Extensive predive/postdive procedures

Self-contained closed-circuit constant 0.75 ppO2
system

4.

Minimum Equipment:

Restrictions:

1.

Working Limit:
150 fsw N2O2

2.
3.
4.
5.
6.
7.

An approved Life Preserver or Buoyancy
Compensator (BC). When using an approved
BC, a Full Face Mask is required.
Dive knife
Swim fins
Face mask or full face mask (FFM)
Weight (as required)
Dive watch or NDC (as required)
Depth gauge or NDC (as required)

200 fsw HeO2

Operational Considerations:
1.
2.
3.

Principal Applications:
1.
2.
3.

Special warfare
Search and inspection
Light repair and recovery

Advantages:
1.
2.
3.
4.
5.
6.
7.

4.

Dive team
Safety boat(s) required
0.75 ppO2 decompression schedule
must be used (unless using NSWIII NDC,
CSMD procedure 110 fsw and shallower,
or air decompression procedures 70 fsw
and shallower)
Due to the hydrostatic effects that are
inherent with a back mounted counter
lung, use is restricted to an oxygen
consumption rate of 1.2 l/min.

Minimal surface bubbles
Optimum efficiency of gas supply
Portability
Excellent mobility
Communications (when used with an
approved FFM)
Modularized assembly
Low acoustic signature

Figure 15‑7. MK 16 MOD 0 General Characteristics.

15-34

U.S. Navy Diving Manual — Volume 4

1.3 ata ppO2 N2O2 Tables

CHAPTER 15 — EC-UBA Diving

15-35

No Decompression Limits and Repetitive Group Designators
for 1.3 ata ppO2 N2O2 Dives
Repetitive Group Designator

No Decompression Limits and Repetitive Group Designators for 1.3 ata ppO2 N2O2 Dives

Depth
(fsw)

No-Stop Limit

10

Unlimited

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

15

Unlimited

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

20

Unlimited

153

420

*

25

Unlimited

51

87

133

196

296

557

*

30

Unlimited

31

50

72

98

128

164

210

273

372

629

*

35

Unlimited

22

35

50

66

84

103

126

151

181

217

263

326

425

680

*

40

Unlimited

89

168

318

*

50

Unlimited

27

44

63

84

108

136

169

210

265

344

496

*

60

297

16

25

36

46

58

70

83

97

113

130

149

170

194

222

255

70

130

11

18

25

32

39

47

55

64

73

83

93

103

115

127

130

80

70

9

14

19

24

30

36

42

48

54

61

68

70

90

50

7

11

15

20

24

29

33

38

43

48

50

100

39

6

9

13

16

20

24

28

32

36

39

110

32

5

8

11

14

17

20

24

27

30

32

120

27

4

7

9

12

15

18

20

23

26

27

130

23

3

6

8

11

13

16

18

21

23

140

21

3

5

7

9

12

14

16

18

21

150

17

3

5

6

8

10

12

15

17

A

B

C

D

E

F

G

H

I

J

K

L

M

N

O

Z

297

Exceptional Exposure ------------------------------------------------------------------------------------------------------------------------------------------

160

15

3

4

6

8

9

11

13

170

13

4

5

7

9

10

12

13

180

12

3

5

6

8

9

11

190

10

4

6

7

9

10

15

12

– Diver does not acquire a repetitive group designator during dives to these depths.
* Highest repetitive group that can be achieved at this depth regardless of bottom time.

Table 15-8. No Decompression Limits and Repetitive Group Designators for 1.3 ata ppO2 N2O2 Dives.

15-36

U.S. Navy Diving Manual — Volume 4

Residual Nitrogen Timetable for 1.3 ata ppO2 N2O2 Dives

Locate the diver’s repetitive group designation from his previous dive along the diagonal line
above the table. Read horizontally to the interval in which the diver’s surface interval
lies.

up

ive

0:10
0:52

0:10
0:52
0:53
1:44

0:10
0:52
0:53
1:44
1:45
2:37

0:10
0:52
0:53
1:44
1:45
2:37
2:38
3:29

0:10
0:52
0:53
1:44
1:45
2:37
2:38
3:29
3:30
4:21

Z

O

N

M

L

M
N
O
Z

Be

Dive
Depth

0:10
0:52
0:53
1:44
1:45
2:37
2:38
3:29
3:30
4:21
4:22
5:13

0:10
0:52
0:53
1:44
1:45
2:37
2:38
3:29
3:30
4:21
4:22
5:13
5:14
6:06

0:10
0:52
0:53
1:44
1:45
2:37
2:38
3:29
3:30
4:21
4:22
5:13
5:14
6:06
6:07
6:58

r
te

D

n

eI

c
rfa

E
F

G
H

I
J

K
L

at

l

va

Su

i
nn

gi

o
Gr

it
et

p

Re

ng

of

B
C

Next, read vertically downward to the new repetitive group designation.
Continue downward in this same column to the row that represents
the depth of the repetitive dive. The time given at the intersection
is residual nitrogen time, in minutes, to be applied to the
repetitive dive.
* Dives following surface intervals longer than
this are not repetitive dives. Use actual
bottom times in the Tables 15-8 and 1510 to compute decompression for
such dives.

A

0:10
0:52
0:53
1:44
1:45
2:37
2:38
3:29
3:30
4:21
4:22
5:13
5:14
6:06
6:07
6:58
6:59
7:50

0:10
0:52
0:53
1:44
1:45
2:37
2:38
3:29
3:30
4:21
4:22
5:13
5:14
6:06
6:07
6:58
6:59
7:50
7:51
8:42

0:10
0:52
0:53
1:44
1:45
2:37
2:38
3:29
3:30
4:21
4:22
5:13
5:14
6:06
6:07
6:58
6:59
7:50
7:51
8:42
8:43
9:34

0:10
0:52
0:53
1:44
1:45
2:37
2:38
3:29
3:30
4:21
4:22
5:13
5:14
6:06
6:07
6:58
6:59
7:50
7:51
8:42
8:43
9:34
9:35
10:27

K
J
I
H
G
F
E
Repetitive Group at the End of the Surface Interval

0:10
0:52
0:53
1:44
1:45
2:37
2:38
3:29
3:30
4:21
4:22
5:13
5:14
6:06
6:07
6:58
6:59
7:50
7:51
8:42
8:43
9:34
9:35
10:27
10:28
11:19
D

0:10
0:55
0:53
1:47
1:45
2:39
2:38
3:31
3:30
4:23
4:22
5:16
5:14
6:08
6:07
7:00
6:59
7:52
7:51
8:44
8:43
9:37
9:35
10:29
10:28
11:21
11:20
12:13
C

0:10
1:16
0:56
2:11
1:48
3:03
2:40
3:55
3:32
4:48
4:24
5:40
5:17
6:32
6:09
7:24
7:01
8:16
7:53
9:09
8:45
10:01
9:38
10:53
10:30
11:45
11:22
12:37
12:14
13:30

0:10
2:20 *
1:17
3:36 *
2:12
4:31 *
3:04
5:23 *
3:56
6:15 *
4:49
7:08 *
5:41
8:00 *
6:33
8:52 *
7:25
9:44 *
8:17
10:36 *
9:10
11:29 *
10:02
12:21 *
10:54
13:13 *
11:46
14:05 *
12:38
14:58 *
13:31
15:50 *

B

A

10

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

15

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–
–

20

**

**

**

**

**

**

**

**

**

**

**

**

**

**

420

153

25

**

**

**

**

**

**

**

**

**

**

556

296

196

134

88

51

30

**

**

**

**

**

**

626

372

273

211

165

129

99

73

51

31

35

**

**

671

423

325

263

218

181

152

126

104

84

67

51

36

22

40

**

**

**

**

**

**

**

**

**

**

**

**

**

311

166

88

50

**

**

**

**

**

481

339

262

209

168

135

107

84

63

44

27

60

293

252

220

192

168

148

129

112

97

83

70

58

46

36

26

16

70

153

139

126

114

103

92

82

73

64

56

47

40

32

25

18

12

80

107

98

90

82

75

68

61

54

48

42

36

30

25

19

14

9

90

82

76

70

64

59

54

48

43

38

34

29

25

20

16

12

8

100

67

62

58

53

49

44

40

36

32

28

24

21

17

13

10

7

110

57

53

49

45

41

38

34

31

28

24

21

18

15

12

9

6

120

49

46

42

39

36

33

30

27

24

21

19

16

13

10

8

5

130

43

40

38

35

32

29

27

24

22

19

17

14

12

9

7

5

140

39

36

34

31

29

26

24

22

19

17

15

13

11

8

6

4

150

35

33

31

28

26

24

22

20

18

16

14

12

10

8

6

4

160

32

30

28

26

24

22

20

18

16

14

13

11

9

7

5

4

170

30

28

26

24

22

20

19

17

15

13

12

10

8

7

5

3

180

27

26

24

22

21

19

17

16

14

12

11

9

8

6

5

3

190

25

24

22

21

19

18
16
15
13
12
10
9
7
6
4
Residual Nitrogen Time (Minutes)
–	Repetitive dives to these depths are equivalent to remaining on the surface. Add the bottom time of the dive to the preceding surface
interval. Use the Surface Interval Credit Table (SICT) to determine the repetitive group at the end of the dive.

3

**	Residual Nitrogen Time cannot be determined using this table. See paragraph 9-9.1 subparagraph 8 for guidance. Substitute the ** depths
in this table for those in the instructions.

CHAPTER 15 — EC-UBA Diving

15-37

Residual Nitrogen Timetable for 1.3 ata ppO2 N2O2 Dives

Table 15-9. Residual Nitrogen Timetable for 1.3 ata ppO2 N2O2 Dives.

Repetitive Dive Worksheet for 1.3 ata ppO2 N2O2 Dives

REPETITIVE DIVE WORKSHEET FOR
1.3 ata ppO2 N2O2 DIVES
Part 1. Previous Dive
		
		

______________ minutes
______________ feet
______________ repetitive group designator from Table 15-8
if the dive was a no-decompression dive, or
Table 15-10 if the dive was a decompression dive.

Part 2. Surface Interval:

REPETITIVE DIVE WORKSHEET FOR 1.3 ata ppO2 N2O2 DIVES

Enter the top section of Table 15-9 at the row for the repetitive group designator from Part 1
and move horizontally to the column in which the actual or planned surface interval time lies.
Read the final repetitive group designator from the bottom of this column.
_________ hours ______ minutes on the surface
_________ final repetitive group from Table 15-9
Part 3. Equivalent Single Dive Time for the Repetitive Dive:
Enter the bottom section of Table 15-9 at the row for the maximum depth of the planned
repetitive dive. Move horizontally to the column of the final repetitive group designator from
Part 2 to find the Residual Nitrogen Time (RNT). Add this RNT to the planned bottom time for
the repetitive dive to obtain the equivalent single dive time.
_____ minutes: RNT
+_____ minutes: planned bottom time
=_____ minutes: equivalent single dive time
Part 4. Decompression Schedule for the Repetitive Dive:
Locate the row for the depth of the planned repetitive dive in Table 15-8. Move horizontally to
the column with bottom time equal to or just greater than the equivalent single dive time and
read the surfacing repetitive group for the repetitive dive from the top of the column. If the
equivalent single dive time exceeds the no-decompression limit, locate the row for the depth
and equivalent single dive time in Table 15-10. Read the required decompression stops and
surfacing repetitive group from the columns to the right along this row.
_____ minutes: equivalent single dive time from Part 3
_____ feet: depth of the repetitive dive.
_____ Schedule (depth/bottom time) from Table 15-8 or Table 15-10.
Ensure RNT Exception Rule does not apply.
Verify allowable repet from Table 15-1.
Figure 15-8. Repetitive Dive Worksheet for 1.3 ata ppO2 N2O2.
15-38

U.S. Navy Diving Manual — Volume 4

1.3 ata ppO2 N2O2 Decompression Tables
Table 15-10. 1.3 ata ppO2 N2O2 Decompression Tables.
(DESCENT RATE 60 FPM­—ASCENT RATE 30 FPM)

Bottom Time
(min)

Time to
First Stop
(M:S)

DECOMPRESSION STOPS (fsw)
Stop times (min) include travel time, except first stop
80

70

60

50

40

30

20

Total Ascent
Time
(M:S)

Repet
Group

60 FSW
297

2:00

0

2:00

Z

300

1:20

1

3:00

Z

310

1:20

2

4:00

Z

320

1:20

3

5:00

Z

330

1:20

4

6:00

Z

340

1:20

5

7:00

350

1:20

6

8:00

360

1:20

7

9:00

370

1:20

8

10:00

380

1:20

9

11:00

390

1:20

10

12:00

130

2:20

0

2:20

O

140

1:40

3

5:20

O

150

1:40

6

8:20

O

160

1:40

8

10:20

Z

170

1:40

10

12:20

Z

180

1:40

12

14:20

Z

190

1:40

14

16:20

Z

200

1:40

16

18:20

Z

210

1:40

19

21:20

Z

220

1:40

22

24:20

Z

230

1:40

24

26:20

Z

1.3 ata ppO2 N2O2 Decompression Tables

Exceptional Exposure --------------------------------------------------------------------------------------------

70 FSW

Exceptional Exposure -------------------------------------------------------------------------------------------240

1:40

26

28:20

250

1:40

29

31:20

260

1:40

31

33:20

270

1:40

33

35:20

280

1:40

35

37:20

290

1:40

37

39:20

300

1:40

38

40:20

310

1:40

40

42:20

320

1:40

42

44:20

340

1:40

47

49:20

350

1:40

49

51:20

CHAPTER 15 — EC-UBA Diving

15-39

1.3 ata ppO2 N2O2 Decompression Tables
Table 15-10. 1.3 ata ppO2 N2O2 Decompression Tables (Continued).
(DESCENT RATE 60 FPM­—ASCENT RATE 30 FPM)

Bottom Time
(min)

Time to
First Stop
(M:S)

DECOMPRESSION STOPS (fsw)
Stop times (min) include travel time, except first stop
80

70

60

50

40

30

20

Total Ascent
Time
(M:S)

Repet
Group

80 FSW
70

2:40

0

2:40

L

75

2:00

2

4:40

L

80

2:00

4

6:40

M

85

2:00

5

7:40

M

90

2:00

6

8:40

N

95

2:00

7

9:40

N

100

2:00

9

11:40

N

1.3 ata ppO2 N2O2 Decompression Tables (Continued)

110

2:00

12

14:40

O

120

2:00

16

18:40

O

130

2:00

20

22:40

Z

140

2:00

24

26:40

Z

150

2:00

27

29:40

Z

160

2:00

30

32:40

Z

170

2:00

34

36:40

Z

Exceptional Exposure --------------------------------------------------------------------------------------------

15-40

180

2:00

39

41:40

190

2:00

43

45:40

200

2:00

47

49:40

210

2:00

50

52:40

220

2:00

54

56:40

230

2:00

57

59:40

240

2:00

60

62:40

250

2:00

63

65:40

260

2:00

67

69:40

270

2:00

70

72:40

280

2:00

74

76:40

290

2:00

77

79:40

300

2:00

81

83:40

310

2:00

84

86:40

320

2:00

87

89:40

U.S. Navy Diving Manual — Volume 4

1.3 ata ppO2 N2O2 Decompression Tables
Table 15-10. 1.3 ata ppO2 N2O2 Decompression Tables (Continued).
(DESCENT RATE 60 FPM­—ASCENT RATE 30 FPM)

Bottom Time
(min)

Time to
First Stop
(M:S)

DECOMPRESSION STOPS (fsw)
Stop times (min) include travel time, except first stop
80

70

60

50

40

30

20

Total Ascent
Time
(M:S)

Repet
Group

50

3:00

0

3:00

K

55

2:20

3

6:00

K

60

2:20

6

9:00

L

65

2:20

8

11:00

L

70

2:20

11

14:00

M

75

2:20

13

16:00

M

80

2:20

14

17:00

N

85

2:20

16

19:00

N

90

2:20

18

21:00

O

95

2:20

21

24:00

O

100

2:20

24

27:00

O

110

2:20

30

33:00

O

120

2:20

35

38:00

Z

130

2:20

40

43:00

Z

1.3 ata ppO2 N2O2 Decompression Tables (Continued)

90 FSW

Exceptional Exposure -------------------------------------------------------------------------------------------140

2:20

45

48:00

150

2:20

51

54:00

160

2:20

57

60:00

170

2:00

1

62

65:40

180

2:00

2

66

70:40

190

2:00

2

71

75:40

100 FSW
39

3:20

0

3:20

J

40

2:40

1

4:20

J

45

2:40

5

8:20

K

50

2:40

9

12:20

L

55

2:40

12

15:20

L

60

2:40

15

18:20

M

65

2:40

18

21:20

M

70

2:40

21

24:20

N

75

2:40

23

26:20

N

80

2:40

26

29:20

O

85

2:40

30

33:20

O

90

2:40

34

37:20

O

95

2:20

1

37

41:00

O

100

2:20

3

39

45:00

O

Exceptional Exposure -------------------------------------------------------------------------------------------110

2:20

6

43

52:00

120

2:20

8

47

58:00

CHAPTER 15 — EC-UBA Diving

15-41

1.3 ata ppO2 N2O2 Decompression Tables
Table 15-10. 1.3 ata ppO2 N2O2 Decompression Tables (Continued).
(DESCENT RATE 60 FPM­—ASCENT RATE 30 FPM)

Bottom Time
(min)

Time to
First Stop
(M:S)

DECOMPRESSION STOPS (fsw)
Stop times (min) include travel time, except first stop
80

70

60

50

40

30

20

Total Ascent
Time
(M:S)

Repet
Group

110 FSW

1.3 ata ppO2 N2O2 Decompression Tables (Continued)

32

3:40

0

3:40

J

35

3:00

3

6:40

J

40

3:00

8

11:40

K

45

3:00

13

16:40

L

50

3:00

17

20:40

L

55

3:00

21

24:40

M

60

3:00

25

28:40

M

65

3:00

28

31:40

N

70

2:40

1

30

34:20

O

75

2:40

4

32

39:20

O

80

2:40

7

34

44:20

O

Exceptional Exposure -------------------------------------------------------------------------------------------85

2:40

9

37

49:20

90
95

2:40

11

39

53:20

2:40

13

42

58:20

100

2:40

15

44

62:20

110

2:20

3

15

49

70:00

120

2:20

6

15

56

80:00

0

4:00

120 FSW
27

4:00

J

30

3:20

4

8:00

J

35

3:20

10

14:00

K

40

3:20

16

20:00

L

45

3:20

21

25:00

L

50

3:20

26

30:00

M

55

3:20

30

34:00

M

60

3:00

4

31

38:40

N

65

3:00

8

30

41:40

O

Exceptional Exposure --------------------------------------------------------------------------------------------

15-42

70

3:00

12

32

47:40

75

3:00

15

35

53:40

80

2:40

3

15

38

59:20

85

2:40

6

15

41

65:20

90

2:40

8

15

44

70:20

95

2:40

10

15

47

75:20

100

2:40

12

15

51

81:20

U.S. Navy Diving Manual — Volume 4

1.3 ata ppO2 N2O2 Decompression Tables
Table 15-10. 1.3 ata ppO2 N2O2 Decompression Tables (Continued).
(DESCENT RATE 60 FPM­—ASCENT RATE 30 FPM)

Bottom Time
(min)

Time to
First Stop
(M:S)

DECOMPRESSION STOPS (fsw)
Stop times (min) include travel time, except first stop
80

70

60

50

40

30

20

Total Ascent
Time
(M:S)

Repet
Group

23

4:20

0

4:20

I

25

3:40

2

6:20

J

30

3:40

10

14:20

K

35

3:40

17

21:20

K

40

3:40

23

27:20

L

45

3:40

29

33:20

M

50

3:20

4

30

38:00

N

55

3:20

9

30

43:00

N

1.3 ata ppO2 N2O2 Decompression Tables (Continued)

130 FSW

Exceptional Exposure -------------------------------------------------------------------------------------------60

3:20

65

3:00

14

30

48:00

3

15

33

54:40

70
75

3:00

7

15

36

61:40

3:00

11

15

39

68:40

80

3:00

14

15

42

74:40

140 FSW
21

4:40

0

4:40

I

25

4:00

7

11:40

J

30

4:00

16

20:40

K

35

4:00

23

27:40

L

40

3:40

2

29

35:20

L

45

3:40

7

30

41:20

M

Exceptional Exposure -------------------------------------------------------------------------------------------50

3:20

1

12

30

47:00

55

3:20

4

15

30

53:00

60

3:20

9

15

33

61:00

65

3:20

13

15

36

68:00

70

3:00

3

15

15

40

76:40

75

3:00

7

15

15

44

84:40

80

3:00

10

15

15

50

93:40

CHAPTER 15 — EC-UBA Diving

15-43

1.3 ata ppO2 N2O2 Decompression Tables
Table 15-10. 1.3 ata ppO2 N2O2 Decompression Tables (Continued).
(DESCENT RATE 60 FPM­—ASCENT RATE 30 FPM)

Bottom Time
(min)

Time to
First Stop
(M:S)

DECOMPRESSION STOPS (fsw)
Stop times (min) include travel time, except first stop
80

70

60

50

40

30

20

Total Ascent
Time
(M:S)

Repet
Group

150 FSW
17

5:00

0

5:00

H

20

4:20

3

8:00

I

25

4:20

13

18:00

J

30

4:20

22

27:00

K

35

4:00

3

27

34:40

L

40

4:00

8

30

42:40

M

Exceptional Exposure --------------------------------------------------------------------------------------------

1.3 ata ppO2 N2O2 Decompression Tables (Continued)

45

3:40

4

11

30

49:20

50

3:40

7

15

30

56:20

55

3:20

2

11

15

33

65:00

60

3:20

4

14

15

37

74:00

65

3:20

8

15

15

40

82:00

70

3:20

13

15

15

46

93:00

75

3:00

2

15

15

15

52

102:40

80

3:00

6

15

15

15

59

113:40

160 FSW
Exceptional Exposure --------------------------------------------------------------------------------------------

15-44

15

5:20

0

5:20

20

4:40

7

12:20

J

25

4:20

17

23:00

K

1

30

4:20

35

4:00

40

4:00

45

3:40

2

50

3:40

55

3:40

60

3:20

65

3:20

70
75
80

3:00

H

3

25

33:00

L

1

8

28

41:40

M

5

10

30

49:40

7

14

30

57:20

5

10

15

33

67:20

8

14

15

36

77:20

3

10

15

15

41

88:00

5

13

15

15

48

100:00

3:20

8

15

15

15

55

112:00

3:20

13

15

15

15

61

123:00

15

15

15

15

68

134:40

3

U.S. Navy Diving Manual — Volume 4

1.3 ata ppO2 N2O2 Decompression Tables
Table 15-10. 1.3 ata ppO2 N2O2 Decompression Tables (Continued).
(DESCENT RATE 60 FPM­—ASCENT RATE 30 FPM)

Bottom Time
(min)

Time to
First Stop
(M:S)

DECOMPRESSION STOPS (fsw)
Stop times (min) include travel time, except first stop
80

70

60

50

40

30

20

Total Ascent
Time
(M:S)

Repet
Group

H

170 FSW
13

5:40

0

5:40

15

5:00

2

7:40

I

20

5:00

12

17:40

J

25

4:40

3

20

28:20

K

30

4:20

5

26

39:00

L

35

4:00

1

5

8

30

48:40

40

4:00

4

7

12

30

57:40

45

4:00

50

3:40

55

3:40

60

3:20

3

8

8

15

32

67:40

7

13

15

36

79:20

7

9

15

15

41

91:20

7

14

15

15

48

105:00

4

2

1.3 ata ppO2 N2O2 Decompression Tables (Continued)

Exceptional Exposure --------------------------------------------------------------------------------------------

180 FSW
Exceptional Exposure -------------------------------------------------------------------------------------------12

6:00

0

6:00

H

15

5:20

4

10:00

I

20

5:00

25

4:40

30

4:20

35

4:00

1

40

4:00

45

4:00

50

3:40

55

3:40

60

3:20

2

14

21:40

K

3

3

23

34:20

L

2

4

7

27

45:00

3

8

9

30

55:40

2

7

8

14

30

65:40

6

7

11

15

35

78:40

8

8

15

15

40

92:20

5

8

12

15

15

49

108:20

7

9

15

15

15

57

123:00

2

1

190 FSW
Exceptional Exposure -------------------------------------------------------------------------------------------10

6:20

0

6:20

G

15

5:40

6

12:20

J

20

5:00

25

4:40

30

4:20

35

4:20

40

4:00

45

4:00

50

3:40

55
60

1

4

16

26:40

K

2

4

4

24

39:20

L

2

3

5

8

29

52:00

4

5

8

11

30

63:00

2

5

8

8

15

34

76:40

4

8

7

14

15

39

91:40

1

7

8

11

15

15

47

108:20

3:40

4

8

8

15

15

15

56

125:20

3:40

7

7

13

15

15

15

65

141:20

CHAPTER 15 — EC-UBA Diving

15-45

PAGE LEFT BLANK INTENTIONALLY

15-46

U.S. Navy Diving Manual — Volume 4

1.3 ata ppO2 HeO2 Tables

CHAPTER 15 — EC-UBA Diving

15-47

No Decompression Limits and Repetitive Group Designators
for 1.3 ata ppO2 HeO2 Dives
Repetitive Group Designator

No Decompression Limits and Repetitive Group Designators for 1.3 ata ppO2 HeO2 Dives

Depth
(fsw)

No-Stop Limit

10

Unlimited

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

15

Unlimited

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

20

Unlimited

129

269

*

25

Unlimited

45

72

106

146

200

278

425

*

30

332

27

43

60

78

100

124

152

185

227

281

332

35

190

19

30

41

54

67

81

97

114

133

154

178

40

Unlimited

122

246

*

50

325

27

43

59

78

99

123

150

183

223

276

325

60

134

15

23

32

41

51

61

71

83

95

108

123

134

70

86

11

16

22

28

34

41

47

54

61

69

77

85

86

80

63

8

12

17

21

26

30

35

40

45

51

56

62

63

90

44

6

10

13

17

20

24

28

32

36

40

44

100

31

5

8

11

14

17

20

23

26

30

31

110

24

4

7

9

12

14

17

20

22

24

120

20

4

6

8

10

13

15

17

19

20

130

17

3

5

7

9

11

13

15

17

140

15

3

4

6

8

10

12

13

15

150

13

3

4

6

7

9

10

12

13

160

12

3

5

6

8

9

11

12

170

11

3

4

6

7

9

10

11

180

10

3

4

5

6

8

9

10

190

9

4

5

6

7

8

9

200

8

4

5

7

8

A

B

C

D

E

F

G

H

I

J

K

L

M

N

O

Z

190

– Diver does not acquire a repetitive group designator during dives to these depths.
* Highest repetitive group that can be achieved at this depth regardless of bottom time.

Table 15-11. No Decompression Limits and Repetitive Group Designators for 1.3 ata ppO2 HeO2 Dives.

15-48

U.S. Navy Diving Manual — Volume 4

Residual Helium Timetable for 1.3 ata ppO2 HeO2 Dives

Locate the diver’s repetitive group designation from his previous dive along the diagonal line
above the table. Read horizontally to the interval in which the diver’s surface interval
lies.

up

ive

0:10
0:42

0:10
0:42
0:43
1:25

0:10
0:42
0:43
1:25
1:26
2:07

0:10
0:42
0:43
1:25
1:26
2:07
2:08
2:49

0:10
0:42
0:43
1:25
1:26
2:07
2:08
2:49
2:50
3:32

Z

O

N

M

L

–
–
**
**
†
420
**
†
217
122
86
67
55
46
40
35
32
29
26
24
22
21
20

–
–
**
**
†
338
**
†
194
112
80
62
51
43
37
33
30
27
25
23
21
20
18

–
–
**
**
†
283
**
†
173
102
73
57
47
40
35
31
28
25
23
21
20
18
17

–
–
**
**
†
241
**
†
154
93
68
53
44
37
32
29
26
23
21
20
18
17
16

–
–
**
**
515
207
**
474
137
85
62
49
40
34
30
27
24
22
20
18
17
16
15

M
N
O
Z

Dive
Depth
10
15
20
25
30
35
40
50
60
70
80
90
100
110
120
130
140
150
160
170
180
190
200

Be

0:10
0:42
0:43
1:25
1:26
2:07
2:08
2:49
2:50
3:32
3:33
4:14

0:10
0:42
0:43
1:25
1:26
2:07
2:08
2:49
2:50
3:32
3:33
4:14
4:15
4:56

0:10
0:42
0:43
1:25
1:26
2:07
2:08
2:49
2:50
3:32
3:33
4:14
4:15
4:56
4:57
5:39

r
te

D

n

eI

c
rfa

E
F

G
H

I
J

K
L

at

l

va

Su

i
nn

gi

o
Gr

it
et

p

Re

ng

of

B
C

Next, read vertically downward to the new repetitive group designation.
Continue downward in this same column to the row that represents
the depth of the repetitive dive. The time given at the intersection
is residual helium time, in minutes, to be applied to the
repetitive dive.
* Dives following surface intervals longer than
this are not repetitive dives. Use actual
bottom times in the Tables 15-11 and
15-13 to compute decompression
for such dives.

A

0:10
0:42
0:43
1:25
1:26
2:07
2:08
2:49
2:50
3:32
3:33
4:14
4:15
4:56
4:57
5:39
5:40
6:21

0:10
0:42
0:43
1:25
1:26
2:07
2:08
2:49
2:50
3:32
3:33
4:14
4:15
4:56
4:57
5:39
5:40
6:21
6:22
7:03

0:10
0:42
0:43
1:25
1:26
2:07
2:08
2:49
2:50
3:32
3:33
4:14
4:15
4:56
4:57
5:39
5:40
6:21
6:22
7:03
7:04
7:46

0:10
0:42
0:43
1:25
1:26
2:07
2:08
2:49
2:50
3:32
3:33
4:14
4:15
4:56
4:57
5:39
5:40
6:21
6:22
7:03
7:04
7:46
7:47
8:28

K
J
I
H
G
F
E
Repetitive Group at the End of the Surface Interval
–
–
–
–
–
–
–
–
–
–
**
**
**
**
**
**
**
**
**
425
361
281
227
186
152
179
155
133
114
97
**
**
**
**
**
345
272
220
181
149
122
108
95
83
71
77
69
61
54
47
56
51
46
40
36
44
40
36
32
29
37
33
30
27
24
31
29
26
23
20
27
25
23
20
18
24
22
20
18
16
22
20
18
16
14
20
18
17
15
13
18
17
15
14
12
17
15
14
13
11
16
14
13
12
10
15
13
12
11
10
14
13
11
10
9
Residual Helium Time (Minutes)

–
–
**
279
124
82
**
122
61
41
31
25
21
18
16
14
13
12
11
10
9
9
8

–
–
**
201
100
68
**
98
51
34
26
21
18
15
13
12
11
10
9
8
8
7
7

0:10
0:42
0:43
1:25
1:26
2:07
2:08
2:49
2:50
3:32
3:33
4:14
4:15
4:56
4:57
5:39
5:40
6:21
6:22
7:03
7:04
7:46
7:47
8:28
8:29
9:10

0:10
0:50
0:43
1:32
1:26
2:15
2:08
2:57
2:50
3:39
3:33
4:22
4:15
5:04
4:57
5:46
5:40
6:29
6:22
7:11
7:04
7:53
7:47
8:36
8:29
9:18
9:11
10:00

0:10
1:10
0:51
2:00
1:33
2:43
2:16
3:25
2:58
4:08
3:40
4:50
4:23
5:32
5:05
6:15
5:47
6:57
6:30
7:39
7:12
8:22
7:54
9:04
8:37
9:46
9:19
10:29
10:01
11:11

0:10
2:01 *
1:11
3:11 *
2:01
4:01 *
2:44
4:44 *
3:26
5:26 *
4:09
6:08 *
4:51
6:51 *
5:33
7:33 *
6:16
8:15 *
6:58
8:58 *
7:40
9:40 *
8:23
10:22 *
9:05
11:05 *
9:47
11:47 *
10:30
12:29 *
11:12
13:12 *

D

C

B

A

–
–
**
147
79
54
**
78
41
28
22
17
15
13
11
10
9
8
8
7
7
6
6

–
–
**
106
60
42
**
59
32
22
17
14
12
10
9
8
7
7
6
6
5
5
5

–
–
269
73
43
31
240
42
24
17
13
10
9
8
7
6
6
5
5
4
4
4
4

–
–
129
45
28
20
120
27
16
11
9
7
6
5
5
4
4
4
3
3
3
3
3

–	
Repetitive dives to these depths are equivalent to remaining on the surface. Add the bottom time of the dive to the preceding surface
interval. Use the Surface Interval Credit Table (SICT) to determine the repetitive group at the end of the dive.
**	Residual Helium Time cannot be determined using this table. See paragraph 9-9.1 subparagraph 8 for guidance. Substitute the ** depths
in this table for those in the instructions.
† Read vertically down to the 35 or 60 fsw repetitive dive depth to obtain the RHT. Decompress on the 35 or 60 fsw table.

CHAPTER 15 — EC-UBA Diving

15-49

Residual Helium Timetable for 1.3 ata ppO2 HeO2 Dives

Table 15-12. Residual Helium Timetable for 1.3 ata ppO2 HeO2 Dives.

Repetitive Dive Worksheet for 1.3 ata ppO2 HeO2 Dives

REPETITIVE DIVE WORKSHEET FOR
1.3 ata ppO2 HeO2 DIVES
Part 1. Previous Dive
		
		

______________ minutes
______________ feet
______________ repetitive group designator from Table 15-11
if the dive was a no-decompression dive, or
Table 15-13 if the dive was a decompression dive.

Part 2. Surface Interval:

REPETITIVE DIVE WORKSHEET FOR 1.3 ata ppO2 HeO2 DIVES

Enter the top section of Table 15-12 at the row for the repetitive group designator from Part 1
and move horizontally to the column in which the actual or planned surface interval time lies.
Read the final repetitive group designator from the bottom of this column.
_________ hours ______ minutes on the surface
_________ final repetitive group from Table 15-12
Part 3. Equivalent Single Dive Time for the Repetitive Dive:
Enter the bottom section of Table 15-12 at the row for the maximum depth of the planned
repetitive dive. Move horizontally to the column of the final repetitive group designator from
Part 2 to find the Residual Helium Time (RHT). Add this RHT to the planned bottom time for
the repetitive dive to obtain the equivalent single dive time.
_____ minutes: RHT
+_____ minutes: planned bottom time
=_____ minutes: equivalent single dive time
Part 4. Decompression Schedule for the Repetitive Dive:
Locate the row for the depth of the planned repetitive dive in Table 15-11. Move horizontally
to the column with bottom time equal to or just greater than the equivalent single dive time
and read the surfacing repetitive group for the repetitive dive from the top of the column. If the
equivalent single dive time exceeds the no-decompression limit, locate the row for the depth
and equivalent single dive time in Table 15-13. Read the required decompression stops and
surfacing repetitive group from the columns to the right along this row.
_____ minutes: equivalent single dive time from Part 3
_____ feet: depth of the repetitive dive.
_____ Schedule (depth/bottom time) from Table 15-11 or Table 15-13.
Ensure RHT Exception Rule does not apply.
Verify allowable repet from Table 15-1.
Figure 15-9. Repetitive Dive Worksheet for 1.3 ata ppO2 HeO2 Dives.
15-50

U.S. Navy Diving Manual — Volume 4

1.3 ata ppO2 HeO2 Decompression Tables
Table 15-13. 1.3 ata ppO2 HeO2 Decompression Tables.
(DESCENT RATE 60 FPM­—ASCENT RATE 30 FPM)

Time
DECOMPRESSION STOPS (fsw)
Bottom to First
Stop times (min) include travel time, except first stop
Time
Stop
(min)
(M:S) 170 160 150 140 130 120 110 100 90
80
70
60
50

40

30

20

Total
Ascent
Time Repet
(M:S) Group

30 FSW
1:00

0

1:00

340

0:20

4

5:00

360

0:20

13

14:00

420

0:20

34

35:00

480

0:20

48

49:00

540

0:20

59

60:00

600

0:20

70

71:00

660

0:20

87

88:00

720

0:20

101 102:00

35 FSW
190

1:10

0

1:10

L

200

0:30

12

13:10

L

210

0:30

23

24:10

220

0:30

33

34:10

230

0:30

42

43:10

240

0:30

50

51:10

270

0:30

71

72:10

300

0:30

89

90:10

330

0:30

360

0:30

103 104:10
115

390

0:30

126 127:10

116:10

420

0:30

145 146:10

450

0:30

162 163:10

480

0:30

177 178:10

50 FSW
325

1:40

0

1:40

K

330

1:00

1

2:40

K

340

1:00

2

3:40

K

350

1:00

3

4:40

K
K

360

1:00

5

6:40

420

1:00

11

12:40

480

1:00

15

16:40

540

1:00

18

19:40

600

1:00

21

22:40

660

1:00

25

26:40

720

1:00

29

30:40

CHAPTER 15 — EC-UBA Diving

15-51

1.3 ata ppO2 HeO2 Decompression Tables

332

1.3 ata ppO2 HeO2 Decompression Tables
Table 15-13. 1.3 ata ppO2 HeO2 Decompression Tables (Continued).
(DESCENT RATE 60 FPM­—ASCENT RATE 30 FPM)
Time
DECOMPRESSION STOPS (fsw)
Bottom to First
Stop times (min) include travel time, except first stop
Time
Stop
(min)
(M:S) 170 160 150 140 130 120 110 100 90
80
70
60
50

40

30

20

Total
Ascent
Time Repet
(M:S) Group

60 FSW
134

2:00

0

2:00

L

140

1:20

3

5:00

L

150

1:20

8

10:00

L

1.3 ata ppO2 HeO2 Decompression Tables (Continued)

160

1:20

12

14:00

L

170

1:20

16

18:00

L

180

1:20

20

22:00

190

1:20

24

26:00

200

1:20

27

29:00

210

1:20

31

33:00

220

1:20

34

36:00

230

1:20

37

39:00

240

1:20

40

42:00

250

1:20

42

44:00

260

1:20

45

47:00

270

1:20

47

49:00

280

1:20

49

51:00

290

1:20

51

53:00

300

1:20

53

55:00

310

1:20

55

57:00

320

1:20

57

59:00

330

1:20

59

61:00

340

1:20

61

63:00

350

1:20

64

66:00

360

1:20

66

68:00

70 FSW
86

2:20

0

2:20

M

90

1:40

3

5:20

M

95

1:40

8

10:20

100

1:40

12

14:20

110

1:40

19

21:20

120

1:40

26

28:20

130

1:40

33

35:20

140

1:40

39

41:20

150

1:40

45

47:20

160

1:40

50

52:20

170

1:40

55

57:20

180

1:40

60

62:20

190

1:40

64

66:20

200

1:40

68

70:20

210

1:40

72

74:20

220

1:40

76

78:20

15-52

U.S. Navy Diving Manual — Volume 4

1.3 ata ppO2 HeO2 Decompression Tables
Table 15-13. 1.3 ata ppO2 HeO2 Decompression Tables (Continued).
(DESCENT RATE 60 FPM­—ASCENT RATE 30 FPM)
Time
DECOMPRESSION STOPS (fsw)
Bottom to First
Stop times (min) include travel time, except first stop
Time
Stop
(min)
(M:S) 170 160 150 140 130 120 110 100 90
80
70
60
50

40

30

20

Total
Ascent
Time Repet
(M:S) Group

63

2:40

0

2:40

M
M

65

2:00

2

4:40

70

2:00

8

10:40

75

2:00

14

16:40

80

2:00

19

21:40

85

2:00

24

26:40

90

2:00

29

31:40

95

2:00

34

36:40

100

2:00

39

41:40

110

2:00

48

50:40

120

2:00

56

58:40

130

2:00

63

65:40

140

2:00

70

72:40

150

2:00

76

78:40

160

2:00

82

84:40

170

2:00

88

90:40

180

2:00

93

95:40

190

2:00

98 100:40

90 FSW
44

3:00

0

3:00

K

45

2:20

1

4:00

K

50

2:20

2

5:00

L

55

2:20

7

10:00

M

60

2:20

15

18:00

65

2:20

22

25:00

70

2:20

29

32:00

75

2:20

35

38:00

80

2:20

41

44:00

85

2:20

47

50:00

90

2:20

53

56:00

95

2:20

58

61:00

100

2:20

63

66:00

110

2:20

73

76:00

120

2:20

82

85:00

130

2:20

90

93:00

140

2:20

97 100:00

150

2:20

105 108:00

160

2:20

112

CHAPTER 15 — EC-UBA Diving

115:00

15-53

1.3 ata ppO2 HeO2 Decompression Tables (Continued)

80 FSW

1.3 ata ppO2 HeO2 Decompression Tables
Table 15-13. 1.3 ata ppO2 HeO2 Decompression Tables (Continued).
(DESCENT RATE 60 FPM­—ASCENT RATE 30 FPM)

Time
DECOMPRESSION STOPS (fsw)
Bottom to First
Stop times (min) include travel time, except first stop
Time
Stop
(min)
(M:S) 170 160 150 140 130 120 110 100 90
80
70
60
50

40

30

20

Total
Ascent
Time Repet
(M:S) Group

100 FSW
31

3:20

0

3:20

J

35

2:40

2

5:20

K

40

2:40

4

7:20

L
M

1.3 ata ppO2 HeO2 Decompression Tables (Continued)

45

2:40

6

9:20

50

2:40

16

19:20

55

2:40

24

27:20

60

2:40

33

36:20

65

2:40

41

44:20

70

2:40

48

51:20

75

2:40

55

58:20

80

2:40

62

65:20

85

2:40

68

71:20

90

2:40

74

77:20

95

2:40

80

83:20

100

2:40

85

88:20

110

2:40

96

99:20

120

2:40

130

2:20

1

140

2:20

1 124 128:00

105 108:20
114

118:00

110 FSW
24

3:40

0

3:40

I

25

3:00

1

4:40

I

30

3:00

4

7:40

J

35

3:00

7

10:40

L

40

3:00

10

13:40

M

45

3:00

21

24:40

50

3:00

31

34:40

55

3:00

40

43:40

60

2:40

1

49

53:20

65

2:40

2

57

62:20

70

2:40

3

64

70:20

75

2:40

4

71

78:20

80

2:40

5

77

85:20

85

2:40

5

84

92:20

90

2:40

6

89

98:20

95

2:40

6

95 104:20

100

2:40

6 101

110

2:40

7

110:20

112 122:20

EXCEPTIONAL EXPOSURE ----------------------------------------------------------------------------------------------------------------------120

2:40

7 123 133:20

130

2:40

7 136 146:20

140

2:20

15-54

1

7 149 160:00

U.S. Navy Diving Manual — Volume 4

1.3 ata ppO2 HeO2 Decompression Tables
Table 15-13. 1.3 ata ppO2 HeO2 Decompression Tables (Continued).
(DESCENT RATE 60 FPM­—ASCENT RATE 30 FPM)

Time
DECOMPRESSION STOPS (fsw)
Bottom to First
Stop times (min) include travel time, except first stop
Time
Stop
(min)
(M:S) 170 160 150 140 130 120 110 100 90
80
70
60
50

40

30

20

Total
Ascent
Time Repet
(M:S) Group

20

4:00

0

4:00

I

25

3:20

4

8:00

J

30

3:20

8

12:00

K
M

35

3:20

12

16:00

40

3:20

23

27:00

45

3:00

2

34

39:40

50

3:00

4

43

50:40

55

3:00

6

52

61:40

60

3:00

7

60

70:40

65

2:40

2

7

68

80:20

70

2:40

3

7

76

89:20

75

2:40

3

8

83

97:20

80

2:40

4

7

91 105:20

85

2:40

5

7

97

112:20

90

2:40

5

8 103

119:20

95

2:40

6

7

110 126:20

EXCEPTIONAL EXPOSURE ----------------------------------------------------------------------------------------------------------------------100

2:40

6

7

110

2:40

7

7 131 148:20

117 133:20

120

2:40

7

7 145 162:20

130 FSW
17

4:20

0

4:20

20

3:40

3

7:20

I

25

3:40

8

12:20

K

30

3:40

35

3:20

H

13

17:20

L

2

21

27:00

L

40

3:20

5

32

41:00

L

45

3:00

1

7

43

54:40

L

50

3:00

3

7

53

66:40

55

3:00

5

7

63

78:40

60

3:00

6

8

71

88:40

65

2:40

1

7

7

81

99:20

70

2:40

2

7

7

89 108:20

75

2:40

3

7

7

97

80

2:40

3

8

7 104 125:20

85

2:40

4

8

7

117:20

111 133:20

EXCEPTIONAL EXPOSURE ----------------------------------------------------------------------------------------------------------------------90

2:40

5

7

7

95

2:40

5

8

7 127 150:20

100

2:40

6

7

7 136 159:20

110

2:40

6

8

7 152 176:20

120

2:40

7

7

18 159 194:20

CHAPTER 15 — EC-UBA Diving

119 141:20

15-55

1.3 ata ppO2 HeO2 Decompression Tables (Continued)

120 FSW

1.3 ata ppO2 HeO2 Decompression Tables
Table 15-13. 1.3 ata ppO2 HeO2 Decompression Tables (Continued).
(DESCENT RATE 60 FPM­—ASCENT RATE 30 FPM)

Time
DECOMPRESSION STOPS (fsw)
Bottom to First
Stop times (min) include travel time, except first stop
Time
Stop
(min)
(M:S) 170 160 150 140 130 120 110 100 90
80
70
60
50

40

30

20

Total
Ascent
Time Repet
(M:S) Group

140 FSW

1.3 ata ppO2 HeO2 Decompression Tables (Continued)

15

4:40

0

4:40

H

20

4:00

7

11:40

J

25

4:00

12

16:40

K

30

3:40

3

16

23:20

M

35

3:40

7

29

40:20

40

3:20

3

7

42

56:00

45

3:20

6

7

53

70:00

50

3:00

1

8

7

64

83:40

55

3:00

3

8

7

74

95:40

60

3:00

5

8

7

84 107:40

65

3:00

7

7

7

93

70

2:40

1

7

8

7 101 127:20

75

2:40

2

7

8

7

117:40

110 137:20

EXCEPTIONAL EXPOSURE ----------------------------------------------------------------------------------------------------------------------80

2:40

3

7

8

7

85

2:40

4

7

7

8 127 156:20

118 146:20

90

2:40

4

8

7

7 137 166:20

95

2:40

5

7

7

8 146 176:20

100

2:40

5

8

7

8 155 186:20

150 FSW
13

5:00

15

4:20

20

4:20

0

5:00

H

3

8:00

H

10

15:00

J

25

4:00

2

14

20:40

L

30

4:00

7

24

35:40

L

35

3:40

4

8

37

53:20

L

40

3:20

1

7

8

50

70:00

45

3:20

4

8

7

63

86:00

50

3:20

7

7

8

74 100:00

55

3:00

2

8

7

7

86

60

3:00

4

8

7

7

96 125:40

65

3:00

6

7

7

8 105 136:40

70

3:00

7

7

8

7

113:40

114 146:40

EXCEPTIONAL EXPOSURE ----------------------------------------------------------------------------------------------------------------------75

2:40

1

8

7

7

8 124 158:20

80

2:40

2

8

7

7

8 135 170:20

85

2:40

3

7

8

7

7 146 181:20

90

2:40

4

7

7

8

9 155 193:20

15-56

U.S. Navy Diving Manual — Volume 4

1.3 ata ppO2 HeO2 Decompression Tables
Table 15-13. 1.3 ata ppO2 HeO2 Decompression Tables (Continued).
(DESCENT RATE 60 FPM­—ASCENT RATE 30 FPM)

Time
DECOMPRESSION STOPS (fsw)
Bottom to First
Stop times (min) include travel time, except first stop
Time
Stop
(min)
(M:S) 170 160 150 140 130 120 110 100 90
80
70
60
50

40

30

20

Total
Ascent
Time Repet
(M:S) Group

160 FSW
5:20

0

15

4:40

5

10:20

I

20

4:40

13

18:20

K
M

25

4:20

30

4:00

35

3:40

40

3:40

45

3:20

50

3:20

55

3:00

1

60

3:00

3

5:20

6

16

27:00

4

8

31

47:40

2

7

8

46

67:20
85:20

6

8

7

60

3

7

7

8

73 102:00

6

7

7

8

85

7

8

7

7

97 130:40

7

8

7

8 107 143:40

H

117:00

EXCEPTIONAL EXPOSURE ----------------------------------------------------------------------------------------------------------------------65

3:00

5

7

8

7

7

70

3:00

6

8

7

7

8 130 169:40

118 155:40

75

3:00

8

7

7

8

7 142 182:40

80

2:40

2

7

7

8

7

7 154 195:20

85

2:40

2

8

7

8

7

16 158 209:20

90

2:40

3

8

7

7

8

25 161 222:20

170 FSW
11

5:40

0

5:40

H

15

5:00

8

13:40

I

20

4:40

25

4:20

2

15

22:20

K

2

8

22

37:00

L

30

4:00

35

4:00

2

7

7

39

59:40

L

7

7

8

55

81:40

40

3:40

45

3:20

1

4

8

7

7

70 100:20

7

8

7

7

84

50

3:20

55

3:20

4

7

8

7

8

96 134:00

7

7

7

8

7 108 148:00

118:00

EXCEPTIONAL EXPOSURE ----------------------------------------------------------------------------------------------------------------------60

3:00

2

7

8

7

7

8 120 162:40

65

3:00

4

7

8

7

7

8 134 178:40

70

3:00

5

8

7

8

7

7 148 193:40

75

3:00

7

7

8

7

7

12 157 208:40

80

2:40

7

8

7

7

8

22 160 223:20

CHAPTER 15 — EC-UBA Diving

1

15-57

1.3 ata ppO2 HeO2 Decompression Tables (Continued)

12

1.3 ata ppO2 HeO2 Decompression Tables
Table 15-13. 1.3 ata ppO2 HeO2 Decompression Tables (Continued).
(DESCENT RATE 60 FPM­—ASCENT RATE 30 FPM)

Time
DECOMPRESSION STOPS (fsw)
Bottom to First
Stop times (min) include travel time, except first stop
Time
Stop
(min)
(M:S) 170 160 150 140 130 120 110 100 90
80
70
60
50

40

30

20

Total
Ascent
Time Repet
(M:S) Group

180 FSW

1.3 ata ppO2 HeO2 Decompression Tables (Continued)

10

6:00

15

5:20

20

5:00

25

4:40

30

4:20

35

4:00

40

3:40

45

3:40

50

3:20

3

0

6:00

H

11

17:00

J

6

14

25:40

L
L

6

8

29

48:20

6

7

8

47

73:00

4

8

7

8

64

95:40

2

8

7

7

8

80

116:20

6

8

7

7

8

94 134:20

7

7

8

7

7 108 151:00

EXCEPTIONAL EXPOSURE ----------------------------------------------------------------------------------------------------------------------55

3:20

60

3:00

1

5

8

7

8

7

7 121 167:00

7

8

7

7

8

7 136 184:40

65

3:00

3

7

8

7

7

8

7 151 201:40

70

3:00

5

7

7

8

7

7

16 158 218:40

190 FSW
9

6:20

0

10

5:40

15

5:40

20

4:40

25

3:20

30

3:00

35

2:40

40

2:20

1

45

2:20

50

2:20

6:20

H

2

8:20

H

14

20:20

J
M

1

1

8

16

31:20

1

0

0

0

4

7

7

38

61:00

1

0

0

2

2

7

7

8

57

87:40

1

0

0

2

0

8

7

8

7

75

111:20

0

0

0

2

6

8

7

7

8

91 133:00

1

0

0

0

5

7

8

7

7

8 105 151:00

1

0

0

0

8

8

7

8

7

7 120 169:00

EXCEPTIONAL EXPOSURE ----------------------------------------------------------------------------------------------------------------------55

2:20

1

0

0

4

8

7

7

8

7

7 138 190:00

60

2:20

1

0

0

7

7

8

7

7

8

7 153 208:00

65

2:20

1

0

2

7

7

8

7

7

8

19 159 228:00

70

2:20

1

0

3

8

7

8

7

7

8

31 164 247:00

15-58

U.S. Navy Diving Manual — Volume 4

1.3 ata ppO2 HeO2 Decompression Tables
Table 15-13. 1.3 ata ppO2 HeO2 Decompression Tables (Continued).
(DESCENT RATE 60 FPM­—ASCENT RATE 30 FPM)

Time
DECOMPRESSION STOPS (fsw)
Bottom to First
Stop times (min) include travel time, except first stop
Time
Stop
(min)
(M:S) 170 160 150 140 130 120 110 100 90
80
70
60
50

40

30

20

Total
Ascent
Time Repet
(M:S) Group

200 FSW
6:40

10

6:00

15

5:20

0

1

20

3:20

25

2:00

30

1:20

35

1:20

40

1:00

1

45

1:00

1

1

6:40

G

5

11:40

H

15

23:00

K

1

0

0

2

0

0

5

7

25

44:00

L

1

0

0

0

2

0

1

0

1

7

7

7

47

75:40

L

1

0

0

2

0

0

0

2

0

1

7

7

8

7

69 106:00

1

0

1

1

0

0

2

0

0

7

7

7

8

7

87 130:00

0

1

1

0

0

2

0

0

5

8

7

7

8

7 104 152:40

0

1

1

0

0

2

0

2

7

8

7

8

7

7 120 172:40

1.3 ata ppO2 HeO2 Decompression Tables (Continued)

8

EXCEPTIONAL EXPOSURE ----------------------------------------------------------------------------------------------------------------------50

1:00

1

0

1

1

0

1

0

1

6

7

7

8

7

8

7 139 195:40

55

1:00

1

0

1

1

0

1

0

2

8

7

7

8

7

8

8 155 215:40

60

1:00

1

0

1

1

0

1

0

5

7

8

7

7

8

7

22 161 237:40

210 FSW
5

7:00

0

7:00

10

6:20

5

12:00

15

6:00

7

5

18:40

20

5:00

2

28

45:40

25

4:20

3

30

4:20

6

35

3:40

40

3:20

3

5

3

2

3

3

2

3

3

57

79:00

3

2

2

6

12

76

112:00

3

3

3

2

3

5

12

12

95 142:20

2

3

2

3

5

12

11

12

113 170:00

EXCEPTIONAL EXPOSURE ----------------------------------------------------------------------------------------------------------------------45

3:20

4

2

3

2

4

11

12

12

11 131 196:00

50

3:20

4

3

2

3

10

11

12

12

11 149 221:00

55

3:00

2

3

2

7

11

11

12

11

12 165 242:40

60

3:20

5

3

2

11

12

11

11

12

21 173 265:00

CHAPTER 15 — EC-UBA Diving

3

15-59

1.3 ata ppO2 HeO2 Decompression Tables
Table 15-13. 1.3 ata ppO2 HeO2 Decompression Tables (Continued).
(DESCENT RATE 60 FPM­—ASCENT RATE 30 FPM)

Time
DECOMPRESSION STOPS (fsw)
Bottom to First
Stop times (min) include travel time, except first stop
Time
Stop
(min)
(M:S) 170 160 150 140 130 120 110 100 90
80
70
60
50

40

30

20

Total
Ascent
Time Repet
(M:S) Group

220 FSW

1.3 ata ppO2 HeO2 Decompression Tables (Continued)

5

7:20

10

6:40

15

5:40

20

5:00

4

25

5:00

7

30

4:00

35
40

3

0

7:20

5

12:20

4

3

2

6

21:20

3

2

3

2

37

56:40

3

3

2

8

65

93:40

3

3

10

12

3

2

3

84 127:40

4:20

8

2

3

2

12

12

11 106 161:00

4:20

9

3

2

12

11

12

11 126 191:00

EXCEPTIONAL EXPOSURE ----------------------------------------------------------------------------------------------------------------------45

3:40

50
55

6

2

3

2

10

12

11

12

4:00

8

4:00

9

11 144 217:20

3

8

11

12

11

11

12 164 244:40

4

12

11

12

11

11

18 177 269:40

230 FSW
5

7:40

10

7:00

15

6:00

20

5:00

25

4:40

30

4:00

3

35

4:00

5

5

3

0

7:40

6

13:40

2

9

25:40

46

67:40

3

3

2

3

3

2

5

2

3

3

2

3

12

3

2

3

2

3

6

12

12

93 143:40

3

2

3

2

8

12

12

11

116 178:40

71 106:20

EXCEPTIONAL EXPOSURE ----------------------------------------------------------------------------------------------------------------------40

3:20

45

4:00

50

3:20

55

3:00

2

2

3

2

3

2

3

8

12

11

12

11 137 210:00

8

2

3

7

12

11

11

12

11 159 240:40

4

3

2

3

5

11

13

11

11

11

16 174 268:00

3

2

4

2

12

11

11

11

11

11

38 172 293:40

240 FSW
5

8:00

10

7:20

15

6:00

20

5:20

5

25

5:20

9

30

4:20

5

3

2

2

35

4:20

7

3

2

3

0

8:00

8

16:00

4

15

34:40

3

3

54

78:00

8

12

4

3

2

2

3

2

3

2

2

3

3

11

12

12 103 161:00

4

12

11

12

12 127 198:00

80 122:00

EXCEPTIONAL EXPOSURE ----------------------------------------------------------------------------------------------------------------------40

4:20

8

3

3

4

12

12

11

12

12 150 232:00

45

4:20

10

2

4

12

12

11

12

11

12 173 264:00

50

3:40

2

3

12

11

11

12

11

11

32 174 292:20

15-60

6

3

U.S. Navy Diving Manual — Volume 4

1.3 ata ppO2 HeO2 Decompression Tables
Table 15-13. 1.3 ata ppO2 HeO2 Decompression Tables (Continued).
(DESCENT RATE 60 FPM­—ASCENT RATE 30 FPM)

Time
DECOMPRESSION STOPS (fsw)
Bottom to First
Stop times (min) include travel time, except first stop
Time
Stop
(min)
(M:S) 170 160 150 140 130 120 110 100 90
80
70
60
50

40

30

20

Total
Ascent
Time Repet
(M:S) Group

250 FSW
5

8:20

10

7:40

15

6:20

20

5:40

25

5:00

30

4:20

4

3

5

3

3

0

8:20

9

17:20

2

24

44:00

61

90:20

6

3

2

3

3

6

6

3

2

2

3

3

12

12

87 135:40

3

2

3

2

8

11

12

12

112 177:00

35

4:40

40

4:20

45

4:00

50

3:40

6

9

2

3

2

10

12

12

11

1.3 ata ppO2 HeO2 Decompression Tables (Continued)

EXCEPTIONAL EXPOSURE ----------------------------------------------------------------------------------------------------------------------12 139 217:20

8

3

2

3

11

12

11

11

12

11 164 253:00

7

3

3

2

11

11

12

11

11

12

25 175 287:40

2

3

3

9

12

11

11

12

11

11

49 175 319:20

260 FSW
5

8:40

0

8:40

10

8:00

11

19:40

15

6:20

31

53:00

20

5:40

25

5:20

30

4:40

6

3

4

3

3

2

3

5

3

3

2

3

3

10

67 102:20

8

3

2

2

3

7

13

12

96 152:00

2

3

2

3

12

12

13

11 123 195:20

EXCEPTIONAL EXPOSURE ----------------------------------------------------------------------------------------------------------------------35

4:40

40

4:20

45

4:00

7

8

3

3

2

6

12

12

11

12

11 151 236:20

8

3

2

3

7

12

12

11

11

12

14 175 275:00

3

2

3

8

12

11

11

11

12

11

42 173 310:40

270 FSW
5

8:20

5

14:00

10

8:20

13

22:00

15

6:20

3

3

3

2

3

3

39

63:00

20

6:20

9

3

2

3

5

12

75

116:00

25

5:40

2

3

3

12

11

9

3

12 105 166:20

EXCEPTIONAL EXPOSURE ----------------------------------------------------------------------------------------------------------------------30

5:00

35

4:40

40

4:20

45

4:20

CHAPTER 15 — EC-UBA Diving

8

3

2

3

2

9

11

12

11

12 134 212:40

8

3

2

3

3

11

12

12

11

11

12 163 256:20

8

3

3

1

5

12

12

11

11

11

12

30 174 298:00

9

3

2

5

12

13

10

11

11

12

11

56 176 336:00

15-61

1.3 ata ppO2 HeO2 Decompression Tables
Table 15-13. 1.3 ata ppO2 HeO2 Decompression Tables (Continued).
(DESCENT RATE 60 FPM­—ASCENT RATE 30 FPM)

Time
DECOMPRESSION STOPS (fsw)
Bottom to First
Stop times (min) include travel time, except first stop
Time
Stop
(min)
(M:S) 170 160 150 140 130 120 110 100 90
80
70
60
50

40

30

20

Total
Ascent
Time Repet
(M:S) Group

280 FSW
5

8:40

10

8:40

15

7:00

20

6:20

25

5:20

6

3

3

7

3

2

3

3

5

14:20

14

23:20

47

72:40

9

2

3

2

3

9

12

82 129:00

2

3

2

7

12

12

12

114 182:00

EXCEPTIONAL EXPOSURE -----------------------------------------------------------------------------------------------------------------------

1.3 ata ppO2 HeO2 Decompression Tables (Continued)

30

5:20

10

3

2

3

3

12

12

11

12

12 145 231:00

35

4:40

8

2

3

2

3

8

12

12

11

11

11

13 176 277:20

40

4:40

10

2

3

2

11

12

11

12

12

10

12

45 174 321:20

45

4:40

11

3

3

11

11

12

11

11

11

12

11

72 178 362:20

290 FSW
5

9:00

10

8:00

15

7:00

20

6:20

25

5:40

8

3

6

3

2

5

14:40

4

4

2

6

24:40

3

3

2

55

81:40

8

2

3

2

3

4

12

12

2

3

3

2

12

12

11

12 122 196:20

88 141:00

EXCEPTIONAL EXPOSURE ----------------------------------------------------------------------------------------------------------------------30

5:00

7

3

2

3

3

2

35

5:00

10

2

3

40

5:00

12

2

3

45

5:00

13

3

9

9

12

12

11

11

12 156 248:40

2

5

7

12

12

11

12

11

11

12

28 176 300:40

11

12

11

11

11

12

11

12

59 177 345:40

11

11

11

11

11

18

82 180 388:40

6

3

2

9

29:00

2

3

5

61

91:40

300 FSW
5

9:20

10

8:20

15

7:00

20

6:20

25

5:20

5

5

3

2

5

3

2

3

15:00

7

3

2

3

2

4

6

12

12

3

3

2

3

7

12

11

12

11 132 212:00

96 154:00

EXCEPTIONAL EXPOSURE ----------------------------------------------------------------------------------------------------------------------30

5:20

9

3

2

35

5:20

12

2

40

5:20

14

2

15-62

3

2

5

12

12

11

11

12

12 169 269:00

3

2

10

12

11

12

11

11

12

41 176 321:00

4

12

12

11

11

12

11

11

11

74 180 371:00

U.S. Navy Diving Manual — Volume 4

1.3 ata ppO2 HeO2 Decompression Tables
Table 15-13. 1.3 ata ppO2 HeO2 Decompression Tables (Continued).
(DESCENT RATE 60 FPM­—ASCENT RATE 30 FPM)

Time
DECOMPRESSION STOPS (fsw)
Bottom to First
Stop times (min) include travel time, except first stop
Time
Stop
(min)
(M:S) 170 160 150 140 130 120 110 100 90
80
70
60
50

40

30

20

Total
Ascent
Time Repet
(M:S) Group

310 FSW
EXCEPTIONAL EXPOSURE ----------------------------------------------------------------------------------------------------------------------8:20

15

7:20

20

6:20

25

6:00

30

5:40

35
40

6

3

3

5

2

3

3

14

2

3

2

9

66 102:00

36:00

6

3

2

3

2

3

3

12

11

9

3

2

3

3

2

12

11

12

12

12 103 167:00
11 142 228:40

11

3

2

2

3

10

12

11

11

12

12

17 176 288:20

5:40

14

2

3

6

12

11

12

11

11

11

12

55 178 344:20

5:40

16

2

10

12

11

12

11

11

11

11

19

83 182 397:20

1.3 ata ppO2 HeO2 Decompression Tables (Continued)

10

320 FSW
EXCEPTIONAL EXPOSURE ----------------------------------------------------------------------------------------------------------------------10

8:20

15

7:40

20

6:20

6

2

3

25

6:20

11

3

2

30

6:00

13

2

3

35

6:00

15

3

3

40

6:00

18

7

11

12

CHAPTER 15 — EC-UBA Diving

8

3

2

3

2

2

3

7

2

6

12

11

11

12

11

12

11

11

11

4

2

3

3

2

21

44:00

2

3

2

3

12

71

112:20

4

5

12

12

12

12

11

12

11

12 153 246:00

12

11

11

12

30 177 308:40

11

11

11

12

68 182 368:40

12

11

11

35

83 185 424:40

111 181:00

15-63

PAGE LEFT BLANK INTENTIONALLY

15-64

U.S. Navy Diving Manual — Volume 4

0.75 ata ppO2 N2O2 Tables

CHAPTER 15 — EC-UBA Diving

15-65

No-Decompression Limits and Repetitive Group Designation Table
for 0.75 ata ppO2 N2O2 Dives
Table 15‑14. No-Decompression Limits and Repetitive Group Designation Table for 0.75 ata Constant
ppO2 N2O2 Dives.
Repetitive Group Designator

No-Decompression Limits and Repetitive Group Designation Table for 0.75 ata ppO2 N2O2 Dives

Depth
(fsw)

No-Stop Limit

10

Unlimited

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

15

Unlimited

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

20

Unlimited

154

425

*

30

Unlimited

31

50

73

98

128

165

211

274

375

643

*

40

369

17

27

38

50

63

76

91

107

125

144

167

192

223

259

305

369

50

143

12

19

26

33

41

50

59

68

78

88

99

111

123

137

143

60

74

9

14

19

25

31

37

43

50

56

63

71

74

70

51

7

11

15

20

25

29

34

39

44

50

51

80

40

6

9

13

16

20

24

28

32

36

40

90

32

5

8

11

14

17

20

24

27

31

32

100

27

4

7

9

12

15

18

21

24

27

110

23

3

6

8

11

13

16

18

21

23

120

20

3

5

7

9

12

14

16

18

20

130

16

4

6

8

10

12

14

16

140

14

4

6

7

9

11

13

14

150

11

3

5

7

8

10

11

A

B

C

D

E

F

G

H

I

J

K

L

M

N

O

Z

Exceptional Exposure ------------------------------------------------------------------------------------------------------------------------------------------

160

10

3

4

6

8

9

10

170

9

3

4

5

7

8

9

– Diver does not acquire a repetitive group designator during dives to these depths.
* Highest repetitive group that can be achieved at this depth regardless of bottom time.

15-66

U.S. Navy Diving Manual — Volume 4

Residual Nitrogen Timetable for Repetitive 0.75 ata ppO2 N2O2 Dives

Locate the diver’s repetitive group designation from his previous dive along the diagonal line
above the table. Read horizontally to the interval in which the diver’s surface interval
lies.

ng

up

ive

0:10
0:52

0:10
0:52
0:53
1:44

0:10
0:52
0:53
1:44
1:45
2:37

0:10
0:52
0:53
1:44
1:45
2:37
2:38
3:29

0:10
0:52
0:53
1:44
1:45
2:37
2:38
3:29
3:30
4:21

Z

O

N

M

L

M
N
O

Dive
Depth

0:10
0:52
0:53
1:44
1:45
2:37
2:38
3:29
3:30
4:21
4:22
5:13

0:10
0:52
0:53
1:44
1:45
2:37
2:38
3:29
3:30
4:21
4:22
5:13
5:14
6:06

ce

0:10
0:52
0:53
1:44
1:45
2:37
2:38
3:29
3:30
4:21
4:22
5:13
5:14
6:06
6:07
6:58

e
nt

I

F

0:10
0:52
0:53
1:44
1:45
2:37
2:38
3:29
3:30
4:21
4:22
5:13
5:14
6:06
6:07
6:58
6:59
7:50

D
E

rfa
G

H
I

J
K

L

Z

o
Gr

it
et

p

Re

Be

al

rv

Su

i
nn

gi

at

of

B
C

Next, read vertically downward to the new repetitive group designation.
Continue downward in this same column to the row that represents
the depth of the repetitive dive. The time given at the intersection
is residual nitrogen time, in minutes, to be applied to the
repetitive dive.
* Dives following surface intervals longer than
this are not repetitive dives. Use actual
bottom times in the Tables 15-14 and
15-16 to compute decompression
for such dives.

A

0:10
0:52
0:53
1:44
1:45
2:37
2:38
3:29
3:30
4:21
4:22
5:13
5:14
6:06
6:07
6:58
6:59
7:50
7:51
8:42

0:10
0:52
0:53
1:44
1:45
2:37
2:38
3:29
3:30
4:21
4:22
5:13
5:14
6:06
6:07
6:58
6:59
7:50
7:51
8:42
8:43
9:34

0:10
0:52
0:53
1:44
1:45
2:37
2:38
3:29
3:30
4:21
4:22
5:13
5:14
6:06
6:07
6:58
6:59
7:50
7:51
8:42
8:43
9:34
9:35
10:27

K
J
I
H
G
F
E
Repetitive Group at the End of the Surface Interval

0:10
0:52
0:53
1:44
1:45
2:37
2:38
3:29
3:30
4:21
4:22
5:13
5:14
6:06
6:07
6:58
6:59
7:50
7:51
8:42
8:43
9:34
9:35
10:27
10:28
11:19
D

0:10
0:55
0:53
1:47
1:45
2:39
2:38
3:31
3:30
4:23
4:22
5:16
5:14
6:08
6:07
7:00
6:59
7:52
7:51
8:44
8:43
9:37
9:35
10:29
10:28
11:21
11:20
12:13
C

0:10
1:16
0:56
2:11
1:48
3:03
2:40
3:55
3:32
4:48
4:24
5:40
5:17
6:32
6:09
7:24
7:01
8:16
7:53
9:09
8:45
10:01
9:38
10:53
10:30
11:45
11:22
12:37
12:14
13:30

0:10
2:20 *
1:17
3:36 *
2:12
4:31 *
3:04
5:23 *
3:56
6:15 *
4:49
7:08 *
5:41
8:00 *
6:33
8:52 *
7:25
9:44 *
8:17
10:36 *
9:10
11:29 *
10:02
12:21 *
10:54
13:13 *
11:46
14:05 *
12:38
14:58 *
13:31
15:50 *

B

A

10

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

15

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–
–

20

**

**

**

**

**

**

**

**

**

**

**

**

**

**

420

153

30

**

**

**

**

**

**

626

372

273

211

165

129

99

73

51

31

40

365

303

258

222

192

167

144

125

107

91

77

63

51

39

28

18

50

167

151

137

123

111

99

88

78

68

59

50

42

34

27

19

12

60

113

104

95

87

79

71

64

57

50

44

38

32

26

20

15

10

70

86

79

73

67

61

56

50

45

40

35

30

25

21

16

12

8

80

69

64

60

55

50

46

41

37

33

29

25

21

18

14

10

7

90

58

54

50

46

43

39

35

32

28

25

22

18

15

12

9

6

100

50

47

44

40

37

34

31

28

25

22

19

16

13

11

8

5

110

44

41

38

36

33

30

27

25

22

19

17

14

12

9

7

5

120

39

37

34

32

29

27

25

22

20

18

15

13

11

9

6

4

130

36

33

31

29

27

24

22

20

18

16

14

12

10

8

6

4

140

33

30

28

26

24

22

20

18

17

15

13

11

9

7

5

4

150

30

28

26

24

22

21

19

17

15

14

12

10

8

7

5

3

160

28

26

24

23

21

19

18

16

14

13

11

9

8

6

5

3

170

26

24

23

21

19

18

16

15

13

12

10

9

7

6

4

3

Residual Nitrogen Times (Minutes)
–	Repetitive dives to these depths are equivalent to remaining on the surface. Add the bottom time of the dive to the preceding surface
interval. Use the Surface Interval Credit Table (SICT) to determine the repetitive group at the end of the dive.
**	Residual Nitrogen Time cannot be determined using this table. See paragraph 9-9.1 subparagraph 8 for guidance. Substitute the ** depths
in this table for those in the instructions.

CHAPTER 15 — EC-UBA Diving

15-67

Residual Nitrogen Timetable for Repetitive 0.75 ata ppO2 N2O2 Dives

Table 15‑15. Residual Nitrogen Timetable for Repetitive 0.75 ata Constant ppO2 N2O2 Dives.

Repetitive Dive Worksheet for 0.75 ATA N O Dives
2

2

REPETITIVE DIVE WORKSHEET FOR
0.75 ata ppO2 N2O2 DIVES
Part 1. Previous Dive
		
		

______________ minutes
______________ feet
______________ repetitive group designator from Table 15-14
if the dive was a no-decompression dive, or
Table 15-16 if the dive was a decompression dive.

Part 2. Surface Interval:

REPETITIVE DIVE WORKSHEET FOR 0.75 ATA N2O2 DIVES5

Enter the top section of Table 15-15 at the row for the repetitive group designator from Part 1
and move horizontally to the column in which the actual or planned surface interval time lies.
Read the final repetitive group designator from the bottom of this column.
_________ hours ______ minutes on the surface
_________ final repetitive group from Table 15-15
Part 3. Equivalent Single Dive Time for the Repetitive Dive:
Enter the bottom section of Table 15-15 at the row for the maximum depth of the planned
repetitive dive. Move horizontally to the column of the final repetitive group designator from
Part 2 to find the Residual Nitrogen Time (RNT). Add this RNT to the planned bottom time for
the repetitive dive to obtain the equivalent single dive time.
_____ minutes: RNT
+_____ minutes: planned bottom time
=_____ minutes: equivalent single dive time
Part 4. Decompression Schedule for the Repetitive Dive:
Locate the row for the depth of the planned repetitive dive in Table 15-14. Move horizontally
to the column with bottom time equal to or just greater than the equivalent single dive time
and read the surfacing repetitive group for the repetitive dive from the top of the column. If the
equivalent single dive time exceeds the no-decompression limit, locate the row for the depth
and equivalent single dive time in Table 15-16. Read the required decompression stops and
surfacing repetitive group from the columns to the right along this row.
_____ minutes: equivalent single dive time from Part 3
_____ feet: depth of the repetitive dive.
_____ Schedule (depth/bottom time) from Table 15-14 or Table 15-16.
Ensure RNT Exception Rule does not apply.
Verify allowable repet from Table 15-1.
Figure 15‑10. Dive Worksheet for Repetitive 0.75 ata ppO2 N2O2 Dives.
15-68

U.S. Navy Diving Manual — Volume 4

Closed-Circuit Mixed-Gas UBA Decompression Table Using 0.75 ata
ppO2 N2O2
Table 15‑16. Closed-Circuit Mixed-Gas UBA Decompression Table Using 0.75 ata ppO2 N2O2
(DESCENT RATE 60 FPM­—ASCENT RATE 30 FPM)

Bottom Time
(min)

Time
to First
Stop
(M:S)

DECOMPRESSION STOPS (FSW)
Stop times (min) include travel time,
except first stop
80

70

60

50

40

30

20

10

Total
Ascent
Time
(M:S)

Repet
Group

369

1:20

0

1:20

Z

370

1:00

1

2:20

Z

380

1:00

2

3:20

Z

390

1:00

3

4:20

Z

143

1:40

0

1:40

O

150

1:20

3

4:40

O

160

1:20

8

9:40

O

170

1:20

12

13:40

O

180

1:20

15

16:40

Z

190

1:20

19

20:40

Z

200

1:20

22

23:40

Z

210

1:20

25

26:40

Z

220

1:20

29

30:40

Z

230

1:20

33

34:40

Z

240

1:20

37

38:40

Z

250

1:20

42

43:40

Z

260

1:20

45

46:40

Z

270

1:20

49

50:40

Z

280

1:20

52

53:40

Z

290

1:20

56

57:40

Z

300

1:20

59

60:40

Z

310

1:20

61

62:40

Z

320

1:20

64

65:40

Z

330

1:20

67

68:40

Z

50 FSW

Exceptional Exposure ----------------------------------------------------------------------------------------------------------------340

1:20

69

70:40

350

1:20

73

74:40

360

1:20

77

78:40

370

1:20

80

81:40

380

1:20

83

84:40

390

1:20

87

88:40

CHAPTER 15 — EC-UBA Diving

15-69

Closed-Circuit Mixed-Gas UBA Decompression Table Using 0.75 ata ppO2 N2O2

40 FSW

Closed-Circuit Mixed-Gas UBA Decompression Table Using 0.75 ata
ppO2 N2O2
Table 15‑16. Closed-Circuit Mixed-Gas UBA Decompression Table Using 0.75 ata ppO2 N2O2
(Continued).
(DESCENT RATE 60 FPM­—ASCENT RATE 30 FPM)

Bottom Time
(min)

Time
to First
Stop
(M:S)

DECOMPRESSION STOPS (FSW)
Stop times (min) include travel time,
except first stop
80

70

60

50

40

30

20

10

Total
Ascent
Time
(M:S)

Repet
Group

Closed-Circuit Mixed-Gas UBA Decompression Table Using 0.75 ata ppO2 N2O2 (Continued)

60 FSW
74

2:00

0

2:00

L

75

1:40

1

3:00

L

80

1:40

3

5:00

L

90

1:40

8

10:00

M

100

1:40

12

14:00

N

110

1:40

16

18:00

O

120

1:40

24

26:00

O

130

1:40

32

34:00

O

140

1:40

38

40:00

Z

150

1:40

44

46:00

Z

160

1:40

50

52:00

Z

170

1:40

55

57:00

Z

180

1:20

3

60

64:40

Z

190

1:20

8

62

71:40

Z

200

1:20

12

65

78:40

Z

210

1:20

15

69

85:40

Z

220

1:20

19

71

91:40

Z

230

1:20

22

74

97:40

Z

240

1:20

25

76

102:40

Z

250

1:20

27

80

108:40

Z

Exceptional Exposure ----------------------------------------------------------------------------------------------------------------260

1:20

30

82

113:40

270

1:20

32

85

118:40

280

1:20

35

88

124:40

290

1:20

40

90

131:40

300

1:20

43

93

137:40

310

1:20

47

94

142:40

320

1:20

51

96

148:40

330

1:20

54

98

153:40

340

1:20

57

100

158:40

350

1:20

60

102

163:40

360

1:20

63

105

169:40

370

1:20

65

109

175:40

380

1:20

68

112

181:40

390

1:20

70

115

186:40

15-70

U.S. Navy Diving Manual — Volume 4

Closed-Circuit Mixed-Gas UBA Decompression Table Using 0.75 ata
ppO2 N2O2
Table 15‑16. Closed-Circuit Mixed-Gas UBA Decompression Table Using 0.75 ata ppO2 N2O2
(Continued).
(DESCENT RATE 60 FPM­—ASCENT RATE 30 FPM)
DECOMPRESSION STOPS (FSW)
Stop times (min) include travel time,
except first stop
80

70

60

50

40

30

20

10

Total
Ascent
Time
(M:S)

2:20

K

Repet
Group

70 FSW
51

2:20

0

55

2:00

4

6:20

K

60

2:00

9

11:20

K

70

2:00

17

19:20

L

80

2:00

90

1:40

24

26:20

M

2

29

33:00

N

100
110

1:40

7

34

43:00

O

1:40

12

39

53:00

O

120

1:40

15

46

63:00

O

130

1:40

18

52

72:00

Z

140

1:40

21

57

80:00

Z

150

1:40

29

58

89:00

Z

160

1:40

36

62

100:00

Z

170

1:40

42

66

110:00

Z

180

1:40

48

70

120:00

Z

Exceptional Exposure ----------------------------------------------------------------------------------------------------------------190

1:20

1

53

73

128:40

200

1:20

2

57

77

137:40

210

1:20

6

57

81

145:40

220

1:20

10

57

84

152:40

230

1:20

14

59

87

161:40

240

1:20

18

62

89

170:40

250

1:20

21

66

91

179:40

260

1:20

24

69

94

188:40

270

1:20

26

72

97

196:40

280

1:20

29

75

99

204:40

290

1:20

31

78

102

212:40

300

1:20

33

81

105

220:40

310

1:20

35

83

110

229:40

320

1:20

37

86

113

237:40

330

1:20

41

86

118

246:40

340

1:20

45

86

124

256:40

350

1:20

49

88

127

265:40

CHAPTER 15 — EC-UBA Diving

15-71

Closed-Circuit Mixed-Gas UBA Decompression Table Using 0.75 ata ppO2 N2O2 (Continued)

Bottom Time
(min)

Time
to First
Stop
(M:S)

Closed-Circuit Mixed-Gas UBA Decompression Table Using 0.75 ata
ppO2 N2O2
Table 15‑16. Closed-Circuit Mixed-Gas UBA Decompression Table Using 0.75 ata ppO2 N2O2
(Continued).
(DESCENT RATE 60 FPM­—ASCENT RATE 30 FPM)

Bottom Time
(min)

Time
to First
Stop
(M:S)

DECOMPRESSION STOPS (FSW)
Stop times (min) include travel time,
except first stop
80

70

60

50

40

30

20

Closed-Circuit Mixed-Gas UBA Decompression Table Using 0.75 ata ppO2 N2O2 (Continued)

10

Total
Ascent
Time
(M:S)

0

2:40

Repet
Group

80 FSW
40

2:40

45

2:20

8

10:40

K

50

2:20

15

17:40

K

55

2:20

21

23:40

L

27

29:40

L

28

39:20

M

60

2:20

70

2:00

9

J

80

2:00

17

29

48:20

N

90

2:00

24

36

62:20

O

100

1:40

2

29

43

76:00

O

110

1:40

7

29

50

88:00

Z

120

1:40

12

29

57

100:00

Z

Exceptional Exposure ----------------------------------------------------------------------------------------------------------------130

1:40

15

37

58

112:00

140

1:40

18

43

62

125:00

150

1:40

21

49

67

139:00

160

1:40

23

56

70

151:00

170

1:40

29

57

75

163:00

180

1:40

36

57

80

175:00

190

1:40

42

57

85

186:00

200

1:20

1

48

60

86

196:40

210

1:20

2

52

64

90

209:40

220

1:20

2

57

68

93

221:40

230

1:20

6

57

73

96

233:40

240

1:20

10

57

77

100

245:40

250

1:20

14

57

81

104

257:40

260

1:20

18

56

85

110

270:40

270

1:20

21

59

86

116

283:40

280

1:20

24

63

85

124

297:40

290

1:20

26

67

86

129

309:40

300

1:20

29

70

88

134

322:40

310

1:20

31

73

92

137

334:40

320

1:20

33

76

95

141

346:40

15-72

U.S. Navy Diving Manual — Volume 4

Closed-Circuit Mixed-Gas UBA Decompression Table Using 0.75 ata
ppO2 N2O2
Table 15‑16. Closed-Circuit Mixed-Gas UBA Decompression Table Using 0.75 ata ppO2 N2O2
(Continued).
(DESCENT RATE 60 FPM­—ASCENT RATE 30 FPM)
DECOMPRESSION STOPS (FSW)
Stop times (min) include travel time,
except first stop
80

70

60

50

40

30

20

10

Total
Ascent
Time
(M:S)

0

3:00

Repet
Group

90 FSW
32

3:00

J

35

2:40

5

8:00

J

40

2:40

14

17:00

K

45

2:40

23

26:00

K

50

2:20

3

28

33:40

L

55

2:20

10

28

40:40

L

60

2:20

17

28

47:40

M

70

2:20

28

29

59:40

N

80

2:00

10

29

34

75:20

O

90

2:00

18

29

44

93:20

Z

Exceptional Exposure ----------------------------------------------------------------------------------------------------------------100

2:00

25

29

52

108:20

110

1:40

3

29

33

56

123:00

120

1:40

8

29

41

62

142:00

130

1:40

12

29

49

67

159:00

140

1:40

16

29

56

73

176:00

150

1:40

19

36

57

76

190:00

160

1:40

21

43

57

81

204:00

170

1:40

23

50

57

89

221:00

180

1:40

25

56

62

91

236:00

190

1:40

31

57

67

95

252:00

0

3:20

100 FSW
27

3:20

30

3:00

6

9:20

J

35

3:00

18

21:20

J

28

31:20

K

28

41:00

L

40

3:00

45

2:40

10

I

50

2:40

19

28

50:00

M

55

2:40

27

29

59:00

M

60

2:20

7

28

28

65:40

N

65

2:20

14

28

28

72:40

O

Exceptional Exposure ----------------------------------------------------------------------------------------------------------------70

2:20

20

28

32

82:40

75

2:20

26

28

37

93:40

80

2:00

3

28

29

42

104:20

90

2:00

12

29

28

53

124:20

100

2:00

20

29

34

61

146:20

110

2:00

27

28

44

66

167:20

CHAPTER 15 — EC-UBA Diving

15-73

Closed-Circuit Mixed-Gas UBA Decompression Table Using 0.75 ata ppO2 N2O2 (Continued)

Bottom Time
(min)

Time
to First
Stop
(M:S)

Closed-Circuit Mixed-Gas UBA Decompression Table Using 0.75 ata
ppO2 N2O2
Table 15‑16. Closed-Circuit Mixed-Gas UBA Decompression Table Using 0.75 ata ppO2 N2O2
(Continued).
(DESCENT RATE 60 FPM­—ASCENT RATE 30 FPM)

Bottom Time
(min)

Time
to First
Stop
(M:S)

DECOMPRESSION STOPS (FSW)
Stop times (min) include travel time,
except first stop
80

70

60

50

40

30

20

Closed-Circuit Mixed-Gas UBA Decompression Table Using 0.75 ata ppO2 N2O2 (Continued)

10

Total
Ascent
Time
(M:S)

0

3:40

Repet
Group

110 FSW
23

3:40

25

3:20

4

7:40

J

30

3:20

18

21:40

J

35

3:00

28

34:20

K

3

I

40

3:00

14

29

46:20

L

45

3:00

25

29

57:20

L

50

2:40

7

29

28

67:00

M

55

2:40

16

29

28

76:00

N

Exceptional Exposure ----------------------------------------------------------------------------------------------------------------60

2:40

65

2:20

4

29

28

33

96:40

70

2:20

11

29

28

40

110:40

24

28

29

52

135:40

29

28

34

65

164:20

0

4:00

I

80

2:20

90

2:00

25

6

28

29

85:00

120 FSW
20

4:00

25

3:40

30

3:20

14

18:00

J

3

27

33:40

J
K

35

3:20

15

29

47:40

40

3:00

4

25

28

60:20

L

45

3:00

12

29

28

72:20

M

Exceptional Exposure -----------------------------------------------------------------------------------------------------------------

15-74

50

2:40

1

23

28

28

83:00

55

2:40

5

29

28

29

94:00

60

2:40

15

28

28

35

109:00

70

2:20

3

28

29

28

50

140:40

80

2:20

17

28

29

31

68

175:40

U.S. Navy Diving Manual — Volume 4

Closed-Circuit Mixed-Gas UBA Decompression Table Using 0.75 ata
ppO2 N2O2
Table 15‑16. Closed-Circuit Mixed-Gas UBA Decompression Table Using 0.75 ata ppO2 N2O2
(Continued).
(DESCENT RATE 60 FPM­—ASCENT RATE 30 FPM)
DECOMPRESSION STOPS (FSW)
Stop times (min) include travel time,
except first stop
80

70

60

50

40

30

20

10

Total
Ascent
Time
(M:S)

0

4:20

Repet
Group

130 FSW
16

4:20

20

4:00

25

3:40

30

3:20

35

3:20

H

5

9:20

I

4

20

28:00

J

2

11

28

44:40

K

7

21

29

60:40

L

Exceptional Exposure ----------------------------------------------------------------------------------------------------------------40

3:00

1

14

28

28

74:20

45

3:00

7

21

28

29

88:20

12

28

28

29

100:20

20

28

29

34

117:00

50

3:00

55

2:40

60

2:40

7

26

28

29

43

136:00

70

2:40

23

28

28

29

67

178:00

0

4:40

H

3

140 FSW
14

4:40

15

4:20

20

4:00

25

3:40

30

3:20

1

1

5:40

H

3

11

18:20

J

3

7

24

38:00

K

7

17

28

56:40

L

Exceptional Exposure ----------------------------------------------------------------------------------------------------------------35

3:20

4

13

24

29

73:40

40

3:20

11

18

28

28

88:40

45

3:00

4

14

25

29

28

103:20

50

3:00

10

18

28

29

35

123:20

60

2:40

5

18

28

29

28

61

172:00

70

2:40

14

28

29

28

36

80

218:00

CHAPTER 15 — EC-UBA Diving

15-75

Closed-Circuit Mixed-Gas UBA Decompression Table Using 0.75 ata ppO2 N2O2 (Continued)

Bottom Time
(min)

Time
to First
Stop
(M:S)

Closed-Circuit Mixed-Gas UBA Decompression Table Using 0.75 ata
ppO2 N2O2
Table 15‑16. Closed-Circuit Mixed-Gas UBA Decompression Table Using 0.75 ata ppO2 N2O2
(Continued).
(DESCENT RATE 60 FPM­—ASCENT RATE 30 FPM)

Bottom Time
(min)

Time
to First
Stop
(M:S)

DECOMPRESSION STOPS (FSW)
Stop times (min) include travel time,
except first stop
80

70

60

50

40

30

20

Closed-Circuit Mixed-Gas UBA Decompression Table Using 0.75 ata ppO2 N2O2 (Continued)

10

Total
Ascent
Time
(M:S)

0

5:00

G
H

Repet
Group

150 FSW
11

5:00

15

4:40

20

4:00

25

3:40

30

3:40

6

11:00

2

7

14

27:20

J

2

7

9

27

49:00

K

7

9

20

28

68:00

M

Exceptional Exposure ----------------------------------------------------------------------------------------------------------------35

3:20

3

10

14

28

28

86:40

40

3:20

7

14

22

28

29

103:40

45

3:00

1

14

15

29

28

35

125:20

50

3:00

7

14

23

29

28

49

153:20

60

2:40

3

14

24

29

28

32

76

209:00

70

2:40

10

24

28

29

28

52

91

265:00

160 FSW
Exceptional Exposure ----------------------------------------------------------------------------------------------------------------10

5:20

15

4:40

20

4:20

25

4:00

30

3:40

35

3:20

3

40

3:20

45

3:20

50

3:00

3

4

0

5:20

7

15:00

6

8

17

35:40

7

7

12

29

59:20

6

7

12

23

28

80:00

7

12

17

29

28

99:40

5

13

14

25

29

35

124:40

12

14

19

29

28

49

154:40

15

14

28

28

29

65

186:20

170 FSW
Exceptional Exposure -----------------------------------------------------------------------------------------------------------------

15-76

9

5:40

0

5:40

10

5:20

2

7:40

15

4:40

20

4:20

25

4:00

30

3:40

35

3:20

2

7

9

14

21

28

35

119:40

40

3:20

5

9

14

15

28

29

46

149:40

45

3:20

50

3:00

5

5

2

2

6

7

20:00

7

7

21

44:40

6

7

7

17

28

69:20

7

8

14

26

29

93:00

8

15

14

24

28

29

65

186:40

14

14

19

28

29

36

76

221:20

U.S. Navy Diving Manual — Volume 4

0.75 ata ppO2 HeO2 Tables

CHAPTER 15 — EC-UBA Diving

15-77

Closed-Circuit Mixed-Gas UBA Decompression Table Using 0.75 ata
Constant Partial Pressure Oxygen in Helium
Table 15-17. Closed-Circuit Mixed-Gas UBA Decompression Table Using 0.75 ata Constant Partial
Pressure Oxygen in Helium.
(DESCENT RATE 60 FPM­—ASCENT RATE 30 FPM)

10

Total
Ascent
Time
(M:S)

1:20

0

1:20

205

1:40

0

1:40

210

1:20

3

4:40

220

1:20

9

10:40

230

1:20

14

15:40

240

1:20

20

21:40

250

1:20

24

25:40

Bottom
Time
(min)

Time
DECOMPRESSION STOPS (fsw)
to First
Stop times (min) include travel time, except first stop
Stop
(M:S) 190 180 170 160 150 140 130 120 110 100 90 80 70 60 50 40

30

20

40 FSW
390

Closed-Circuit Mixed-Gas UBA Decompression Table Using 0.75 ata ppO2 HeO2

50 FSW

Exceptional Exposure -------------------------------------------------------------------------------------------------------------------------------260

1:20

29

30:40

270

1:20

33

34:40

280

1:20

37

38:40

290

1:20

41

42:40

300

1:20

45

46:40

310

1:20

48

49:40

320

1:20

52

53:40

330

1:20

55

56:40

340

1:20

58

59:40

350

1:20

60

61:40

360

1:20

63

64:40

370

1:20

65

66:40

380

1:20

68

69:40

390

1:20

70

71:40

133

2:00

0

2:00

140

1:40

8

10:00

150

1:40

20

22:00

160

1:40

30

32:00

170

1:40

40

42:00

60 FSW

Exceptional Exposure -------------------------------------------------------------------------------------------------------------------------------180

1:40

50

52:00

190

1:40

59

61:00

200

1:40

67

69:00

210

1:40

75

77:00

220

1:40

82

84:00

230

1:40

90

92:00

240

1:40

96

98:00

250

1:40

103

105:00

260

1:40

109

111:00

270

1:20

1 113

115:40

15-78

U.S. Navy Diving Manual — Volume 4

Closed-Circuit Mixed-Gas UBA Decompression Table Using 0.75 ata
Constant Partial Pressure Oxygen in Helium
Table 15-17. Closed-Circuit Mixed-Gas UBA Decompression Table Using 0.75 ata Constant Partial
Pressure Oxygen in Helium (Continued).

Bottom
Time
(min)

Time
DECOMPRESSION STOPS (fsw)
to First
Stop times (min) include travel time, except first stop
Stop
(M:S) 190 180 170 160 150 140 130 120 110 100 90 80 70 60 50 40

30

20

10

Total
Ascent
Time
(M:S)

60 FSW Continued
280

1:20

7 113

121:40

290

1:20

12 113

126:40

300

1:20

16 114

131:40

310

1:20

21 113

135:40

320

1:20

25 113

139:40

330

1:20

29 113

143:40

340

1:20

33 113

147:40

350

1:20

36 113

150:40

360

1:20

40 113

154:40

370

1:20

43 113

157:40

380

1:20

46 113

160:40

390

1:20

49 113

163:40

82

2:20

0

2:20

85

2:00

2

4:20

90

2:00

6

8:20

95

2:00

9

11:20

100

2:00

12

14:20

110

2:00

19

21:20

120

2:00

35

37:20

130

2:00

51

53:20

140

2:00

65

67:20

70 FSW

Exceptional Exposure -------------------------------------------------------------------------------------------------------------------------------150

2:00

160

2:00

92

94:20

170

2:00

104

106:20

180

1:40

7 109

118:00

190

1:40

14 113

129:00

200

1:40

24 113

139:00

210

1:40

34 113

149:00

220

1:40

43 113

158:00

230

1:40

52 113

167:00

240

1:40

60 113

175:00

250

1:40

68 113

183:00

260

1:40

75 113

190:00

270

1:40

82 113

197:00

CHAPTER 15 — EC-UBA Diving

79

81:20

15-79

Closed-Circuit Mixed-Gas UBA Decompression Table Using 0.75 ata ppO2 HeO2 (Continued)

(DESCENT RATE 60 FPM—ASCENT RATE 30 FPM)

Closed-Circuit Mixed-Gas UBA Decompression Table Using 0.75 ata
Constant Partial Pressure Oxygen in Helium
Table 15-17. Closed-Circuit Mixed-Gas UBA Decompression Table Using 0.75 ata Constant Partial
Pressure Oxygen in Helium (Continued).
(DESCENT RATE 60 FPM—ASCENT RATE 30 FPM)

Bottom
Time
(min)

Time
DECOMPRESSION STOPS (fsw)
to First
Stop times (min) include travel time, except first stop
Stop
(M:S) 190 180 170 160 150 140 130 120 110 100 90 80 70 60 50 40

30

20

10

Total
Ascent
Time
(M:S)

80 FSW
Closed-Circuit Mixed-Gas UBA Decompression Table Using 0.75 ata ppO2 HeO2 (Continued)

52

2:40

0

2:40

55

2:20

2

4:40

60

2:20

5

7:40

65

2:20

8

10:40

70

2:20

14

16:40

75

2:20

19

21:40

80

2:20

24

26:40

85

2:20

29

31:40

90

2:20

33

35:40

95

2:20

36

38:40

100

2:00

3

44

49:20

110

2:00

9

58

69:20

120

2:00

14

73

89:20

Exceptional Exposure -------------------------------------------------------------------------------------------------------------------------------130

2:00

18

87

107:20

140

2:00

22 100

124:20

150

2:00

33 105

140:20

160

2:00

43 111

156:20

170

2:00

55 113

170:20

180

2:00

69 113

184:20

190

2:00

82 113

197:20

37

3:00

0

3:00

40

2:40

4

7:00

45

2:40

10

13:00

50

2:40

15

18:00

55

2:40

19

22:00

60

2:20

1

23

26:40

65

2:20

4

27

33:40

70

2:20

6

32

40:40

75

2:20

8

36

46:40

80

2:20

12

38

52:40

85

2:20

17

38

57:40

90

2:20

22

44

68:40

95

2:20

26

53

81:40

100

2:20

30

61

93:40

110

2:20

38

77

117:40

120

2:00

38

94

140:20

90 FSW

6

Exceptional Exposure -------------------------------------------------------------------------------------------------------------------------------130

2:00

11

46 102

161:20

140

2:00

15

55 109

181:20

150

2:00

19

66 113

200:20

160

2:00

22

81 113

218:20

15-80

U.S. Navy Diving Manual — Volume 4

Closed-Circuit Mixed-Gas UBA Decompression Table Using 0.75 ata
Constant Partial Pressure Oxygen in Helium
Table 15-17. Closed-Circuit Mixed-Gas UBA Decompression Table Using 0.75 ata Constant Partial
Pressure Oxygen in Helium (Continued).
(DESCENT RATE 60 FPM—ASCENT RATE 30 FPM)

Bottom
Time
(min)

Time
DECOMPRESSION STOPS (fsw)
to First
Stop times (min) include travel time, except first stop
Stop
(M:S) 190 180 170 160 150 140 130 120 110 100 90 80 70 60 50 40

30

20

10

Total
Ascent
Time
(M:S)

3:20

29

3:20

0

30

3:00

1

4:20

35

3:00

11

14:20

40

3:00

19

22:20

50

2:40

9

22

34:00

60

2:40

18

27

48:00

70

2:20

2

22

38

64:40

80

2:20

7

31

41

81:40

90

2:20

11

38

59

110:40

100

2:20

21

38

78

139:40

Exceptional Exposure -------------------------------------------------------------------------------------------------------------------------------110

2:20

29

39

96

166:40

120

2:20

36

50 103

191:40

130

2:00

4

38

61 111

216:20

140

2:00

9

38

76 113

238:20

3:40

110 FSW
23

3:40

0

25

3:20

2

5:40

30

3:20

14

17:40

35

3:00

3

22

28:20

40

3:00

11

22

36:20

50

2:40

3

22

22

50:00

60

2:40

13

22

33

71:00

70

2:40

20

28

37

88:00

80

2:20

3

23

37

55

120:40

90

2:20

7

31

38

76

154:40

100

2:20

11

38

39

96

186:40

Exceptional Exposure -------------------------------------------------------------------------------------------------------------------------------110

2:20

20

38

52 103

215:40

120

2:20

28

38

64 111

243:40

130

2:20

34

40

80 113

269:40

140

2:00

38

51

89 113

295:20

CHAPTER 15 — EC-UBA Diving

2

15-81

Closed-Circuit Mixed-Gas UBA Decompression Table Using 0.75 ata ppO2 HeO2 (Continued)

100 FSW

Closed-Circuit Mixed-Gas UBA Decompression Table Using 0.75 ata
Constant Partial Pressure Oxygen in Helium
Table 15-17. Closed-Circuit Mixed-Gas UBA Decompression Table Using 0.75 ata Constant Partial
Pressure Oxygen in Helium (Continued).
(DESCENT RATE 60 FPM—ASCENT RATE 30 FPM)

Bottom
Time
(min)

Time
DECOMPRESSION STOPS (fsw)
to First
Stop times (min) include travel time, except first stop
Stop
(M:S) 190 180 170 160 150 140 130 120 110 100 90 80 70 60 50 40

30

20

10

Total
Ascent
Time
(M:S)

4:00

120 FSW
Closed-Circuit Mixed-Gas UBA Decompression Table Using 0.75 ata ppO2 HeO2 (Continued)

18

4:00

0

20

3:40

2

6:00

25

3:40

13

17:00

30

3:20

5

22

30:40

35

3:20

16

22

41:40

40

3:00

4

22

22

51:20

50

3:00

19

23

24

69:20

60

2:40

9

22

22

37

93:00

70

2:40

16

22

34

52

127:00

80

2:40

22

29

38

72

164:00

Exceptional Exposure -------------------------------------------------------------------------------------------------------------------------------90

2:20

4

24

37

38

95

200:40

100

2:20

7

32

38

50 104

233:40

110

2:20

12

37

38

65 112

266:40

120

2:20

20

38

41

83 113

297:40

130 FSW
15

4:20

0

4:20

20

4:00

8

12:20

25

3:40

6

18

28:00

30

3:20

2

16

22

43:40

35

3:20

8

22

22

55:40

40

3:20

19

22

22

66:40

50

3:00

14

22

22

28

89:20

60

2:40

4

22

22

26

48

125:00

70

2:40

12

22

24

38

70

169:00

Exceptional Exposure -------------------------------------------------------------------------------------------------------------------------------80

2:40

18

22

36

38

93

210:00

90

2:20

1

22

32

37

46 107

247:40

100

2:20

4

26

38

37

64 113

284:40

110

2:20

6

35

38

40

84 113

318:40

120

2:20

12

38

38

55

93 113

351:40

15-82

U.S. Navy Diving Manual — Volume 4

Closed-Circuit Mixed-Gas UBA Decompression Table Using 0.75 ata
Constant Partial Pressure Oxygen in Helium
Table 15-17. Closed-Circuit Mixed-Gas UBA Decompression Table Using 0.75 ata Constant Partial
Pressure Oxygen in Helium (Continued).
(DESCENT RATE 60 FPM—ASCENT RATE 30 FPM)

Bottom
Time
(min)

Time
DECOMPRESSION STOPS (fsw)
to First
Stop times (min) include travel time, except first stop
Stop
(M:S) 190 180 170 160 150 140 130 120 110 100 90 80 70 60 50 40

30

20

10

Total
Ascent
Time
(M:S)

4:40

12

4:40

0

15

4:20

4

8:40

20

4:00

5

12

21:20

25

3:40

4

10

22

40:00

30

3:40

10

20

22

56:00

35

3:20

4

18

22

22

69:40

40

3:20

12

22

22

22

81:40

50

3:00

8

22

22

22

35

112:20

60

3:00

21

22

22

31

66

165:20

70

2:40

22

22

29

38

93

216:00

9

Exceptional Exposure -------------------------------------------------------------------------------------------------------------------------------80

2:40

15

22

27

38

40 113

258:00

90

2:40

20

23

38

38

63 113

298:00

100

2:20

22

35

38

37

88 113

336:40

1

150 FSW
10

5:00

15

4:20

20

4:00

25

3:40

30

3:40

35

3:20

3

40

3:20

6

45

3:20

50

3:00

55
60

0

5:00

2

7

13:40

2

10

15

31:20

2

9

15

22

52:00

7

14

22

22

69:00

11

22

22

22

83:40

21

22

22

22

96:40

15

22

22

22

33

117:40

2

23

22

22

22

56

150:20

3:00

10

22

22

22

27

74

180:20

3:00

16

22

23

22

35

88

209:20

Exceptional Exposure -------------------------------------------------------------------------------------------------------------------------------70

2:40

5

22

22

22

35

40 113

262:00

80

2:40

12

22

22

34

38

65 113

309:00

90

2:40

17

22

31

38

38

90 113

352:00

CHAPTER 15 — EC-UBA Diving

15-83

Closed-Circuit Mixed-Gas UBA Decompression Table Using 0.75 ata ppO2 HeO2 (Continued)

140 FSW

Closed-Circuit Mixed-Gas UBA Decompression Table Using 0.75 ata
Constant Partial Pressure Oxygen in Helium
Table 15-17. Closed-Circuit Mixed-Gas UBA Decompression Table Using 0.75 ata Constant Partial
Pressure Oxygen in Helium (Continued).
(DESCENT RATE 60 FPM—ASCENT RATE 30 FPM)

Bottom
Time
(min)

Time
DECOMPRESSION STOPS (fsw)
to First
Stop times (min) include travel time, except first stop
Stop
(M:S) 190 180 170 160 150 140 130 120 110 100 90 80 70 60 50 40

30

20

10

Total
Ascent
Time
(M:S)

5:10

155 FSW
Closed-Circuit Mixed-Gas UBA Decompression Table Using 0.75 ata ppO2 HeO2 (Continued)

9

5:10

0

10

4:50

1

6:10

15

4:30

3

9

16:50

20

4:10

5

10

17

36:30

25

3:50

5

9

17

22

57:10

30

3:30

2

9

17

22

22

75:50

35

3:30

6

15

22

22

22

90:50

40

3:30

12

22

22

22

22

103:50

45

3:10

3

20

22

22

22

44

136:30

50

3:10

10

23

22

22

22

68

170:30

55

3:10

18

22

22

22

30

84

201:30

60

2:50

22

22

22

22

38 100

232:10

3

Exceptional Exposure -------------------------------------------------------------------------------------------------------------------------------70

2:50

80

2:50

90

2:30

5

14

22

22

22

38

52 113

286:10

21

22

22

38

37

77 113

333:10

22

22

35

38

37 103 113

377:50

160 FSW
9

5:20

0

5:20

10

5:00

2

7:20

15

4:20

1

4

10

19:40

20

4:00

1

8

9

19

41:20

25

4:00

8

10

19

22

63:20

30

3:40

5

10

19

22

22

82:00

35

3:20

1

9

18

22

22

22

97:40

40

3:20

4

15

22

22

23

27

116:40

45

3:20

9

22

22

22

22

55

155:40

50

3:20

18

22

23

22

22

79

189:40

Exceptional Exposure -------------------------------------------------------------------------------------------------------------------------------55

3:00

60

3:00

70

2:40

1

80

2:40

90

2:40

15-84

5

22

22

22

22

31

97

224:20

12

22

22

22

24

38 113

256:20

22

22

22

25

38

64 113

310:00

8

22

23

25

37

38

91 113

360:00

14

22

24

37

38

43 111 113

405:00

U.S. Navy Diving Manual — Volume 4

Closed-Circuit Mixed-Gas UBA Decompression Table Using 0.75 ata
Constant Partial Pressure Oxygen in Helium
Table 15-17. Closed-Circuit Mixed-Gas UBA Decompression Table Using 0.75 ata Constant Partial
Pressure Oxygen in Helium (Continued).
(DESCENT RATE 60 FPM—ASCENT RATE 30 FPM)

Bottom
Time
(min)

Time
DECOMPRESSION STOPS (fsw)
to First
Stop times (min) include travel time, except first stop
Stop
(M:S) 190 180 170 160 150 140 130 120 110 100 90 80 70 60 50 40

30

20

10

Total
Ascent
Time
(M:S)

5:30

8

5:30

0

10

5:10

3

8:30

15

4:30

20

4:10

25

3:50

2

30

3:50

9

35

3:30

5

40

3:30

45

3:10

1

50

3:10

5

22

2

6

9

21:50

10

9

21

46:30

10

9

22

22

69:10

9

22

22

22

88:10

9

21

22

22

22

104:50

8

19

22

22

22

39

135:50

16

22

22

22

22

66

174:30

22

22

22

24

92

212:30

2

Exceptional Exposure -------------------------------------------------------------------------------------------------------------------------------55

3:10

13

22

22

22

22

34 108

60

3:10

20

22

22

22

27

48 113

246:30
277:30

70

2:50

10

22

22

22

28

38

79 113

337:10

80

2:50

18

22

22

28

38

38 105 113

387:10

0

5:40

170 FSW
8

5:40

10

5:00

15

4:40

20

4:20

25

4:00

30

3:40

35

3:40

40

3:20

45
50

1

3

9:20

4

7

9

25:00

5

10

10

22

51:40

6

9

11

22

22

74:20

3

10

12

22

22

22

95:00

8

12

22

22

22

22

112:00

3

9

22

22

22

22

50

153:40

3:20

5

19

22

23

22

22

78

194:40

3:20

13

22

22

22

22

26 104

234:40

Exceptional Exposure -------------------------------------------------------------------------------------------------------------------------------55

3:20

60

3:00

70

3:00

80

2:40

CHAPTER 15 — EC-UBA Diving

5

21

23

22

22

22

42 113

268:40

7

22

22

22

22

29

62 113

302:20

19

22

22

22

31

38

92 113

362:20

22

22

22

32

38

43 113 113

413:00

15-85

Closed-Circuit Mixed-Gas UBA Decompression Table Using 0.75 ata ppO2 HeO2 (Continued)

165 FSW

Closed-Circuit Mixed-Gas UBA Decompression Table Using 0.75 ata
Constant Partial Pressure Oxygen in Helium
Table 15-17. Closed-Circuit Mixed-Gas UBA Decompression Table Using 0.75 ata Constant Partial
Pressure Oxygen in Helium (Continued).
(DESCENT RATE 60 FPM—ASCENT RATE 30 FPM)

Bottom
Time
(min)

Time
DECOMPRESSION STOPS (fsw)
to First
Stop times (min) include travel time, except first stop
Stop
(M:S) 190 180 170 160 150 140 130 120 110 100 90 80 70 60 50 40

30

20

10

Total
Ascent
Time
(M:S)

175 FSW
Closed-Circuit Mixed-Gas UBA Decompression Table Using 0.75 ata ppO2 HeO2 (Continued)

7

5:50

10

5:10

15

4:30

20

4:10

25

4:10

30

3:50

35

3:30

40

3:30

1

0

5:50

2

4

11:30

1

4

8

10

27:50

7

10

12

22

56:30

9

9

14

22

22

80:30

7

9

15

22

22

22

101:10

3

9

15

22

22

22

31

127:50

7

13

22

22

22

22

62

173:50

Exceptional Exposure -------------------------------------------------------------------------------------------------------------------------------45

3:30

10

22

22

22

22

22

91

214:50

50

3:10

2

19

22

22

22

22

30 113

255:30

55

3:10

8

22

22

22

22

22

58 113

292:30

60

3:10

16

22

22

22

22

31

76 113

327:30

65

3:10

22

22

22

22

25

38

90 113

357:30

70

2:50

6

22

22

22

22

34

38 106 113

388:10

75

2:50

10

22

22

23

27

37

45 113 113

415:10

80

2:50

14

22

22

22

36

38

58 113 113

441:10

0

6:00

180 FSW
7

6:00

10

5:20

15

4:40

20

4:20

25

4:00

30

3:40

35

3:40

40

3:20

3

4

12:40

3

4

9

11

32:00

3

8

10

14

22

61:40

3

9

10

16

22

22

86:20

10

9

17

22

22

23

108:00

7

9

17

22

23

22

41

145:00

10

16

22

22

22

22

73

191:40

1
1

Exceptional Exposure -------------------------------------------------------------------------------------------------------------------------------45

3:20

4

14

22

22

22

22

22 105

236:40

50

3:20

7

22

22

22

22

22

44 113

277:40

55

3:20

16

22

22

22

22

24

70 113

314:40

60

3:00

3

22

22

22

22

22

33

90 113

352:20

65

3:00

9

22

22

22

22

28

38 105 113

384:20

70

3:00

15

22

22

22

22

37

45 113 113

414:20

15-86

U.S. Navy Diving Manual — Volume 4

Closed-Circuit Mixed-Gas UBA Decompression Table Using 0.75 ata
Constant Partial Pressure Oxygen in Helium
Table 15-17. Closed-Circuit Mixed-Gas UBA Decompression Table Using 0.75 ata Constant Partial
Pressure Oxygen in Helium (Continued).
(DESCENT RATE 60 FPM—ASCENT RATE 30 FPM)

Bottom
Time
(min)

Time
DECOMPRESSION STOPS (fsw)
to First
Stop times (min) include travel time, except first stop
Stop
(M:S) 190 180 170 160 150 140 130 120 110 100 90 80 70 60 50 40

30

20

10

Total
Ascent
Time
(M:S)

6

6:10

10

5:30

15

4:50

20

4:10

25

4:10

30

3:50

35

3:30

1

40

3:30

5

6:10

4

13:50

4

5

10

12

36:10

10

9

16

22

66:30

10

9

19

22

22

92:30

10

20

22

22

22

114:10

9

21

22

22

22

52

162:50

19

22

22

22

22

86

211:50

1

4

6
9

10
10

5

0
4

Exceptional Exposure -------------------------------------------------------------------------------------------------------------------------------45

3:30

8

18

22

22

22

22

28 113

50

3:10

1

14

22

22

22

22

22

58 113

299:30

55

3:10

3

22

22

22

22

22

26

84 113

339:30

60

3:10

11

22

22

22

22

22

36 103 113

376:30

65

3:10

18

22

22

22

22

30

44 113 113

409:30

70

2:50

22

22

22

22

24

38

60 113 113

441:10

2

258:50

190 FSW
6

6:20

10

5:20

15

4:40

20

4:20

25

4:00

1

30

4:00

8

35

3:40

5

40

3:40

9

0

6:20

1

4

5

15:40

6

9

15

41:00
71:40

2

4

2

6

10

9

18

22

9

9

10

20

23

22

98:20

10

10

22

22

22

27

125:20

9

11

22

22

22

22

63

180:00

11

22

22

22

22

22

99

233:00

Exceptional Exposure -------------------------------------------------------------------------------------------------------------------------------45

3:20

3

9

22

22

22

22

22

41 113

50

3:20

5

18

22

22

22

22

22

73 113

322:40

55

3:20

11

22

22

22

22

22

28

99 113

364:40

60

3:20

20

22

22

22

22

22

42 114 113

402:40

65

3:00

5

22

22

22

22

22

33

59 113 113

436:20

70

3:00

11

22

22

22

22

27

38

76 113 113

469:20

CHAPTER 15 — EC-UBA Diving

279:40

15-87

Closed-Circuit Mixed-Gas UBA Decompression Table Using 0.75 ata ppO2 HeO2 (Continued)

185 FSW

Closed-Circuit Mixed-Gas UBA Decompression Table Using 0.75 ata
Constant Partial Pressure Oxygen in Helium
Table 15-17. Closed-Circuit Mixed-Gas UBA Decompression Table Using 0.75 ata Constant Partial
Pressure Oxygen in Helium (Continued).
(DESCENT RATE 60 FPM—ASCENT RATE 30 FPM)

Bottom
Time
(min)

Time
DECOMPRESSION STOPS (fsw)
to First
Stop times (min) include travel time, except first stop
Stop
(M:S) 190 180 170 160 150 140 130 120 110 100 90 80 70 60 50 40

30

20

10

Total
Ascent
Time
(M:S)

195 FSW
Closed-Circuit Mixed-Gas UBA Decompression Table Using 0.75 ata ppO2 HeO2 (Continued)

6
6:30
0
10
5:30
3
3
6
15
4:50
3
4
8
9 16
20
4:30
4
7 10
9 20 22
25
4:10
4
9 10 10 22 22 22
30
3:50
3
9 10 12 22 23 22 37
35
3:50
9
9 14 22 22 22 22 75
40
3:30
4
9 14 22 22 22 22 22 112
Exceptional Exposure -------------------------------------------------------------------------------------------------------------------------------45
3:30
7 12 22 22 22 22 22 55 113
50
3:30
9 22 22 22 22 22 22 88 113
55
3:10
1 19 22 22 22 22 22 30 113 113
60
3:10
6 22 22 22 22 22 26 55 113 113

6:30
17:50
45:10
76:50
103:30
142:10
199:10
252:50
300:50
345:50
389:30
426:30

200 FSW
6
6:40
0
10
5:40
4
4
6
15
4:40
1
4
4
8 10 17
20
4:20
2
4
9
9
9 22 22
25
4:20
7 10
9 13 22 22 22
30
4:00
6 10
9 16 22 22 22 48
35
3:40
3 10
9 17 22 22 22 22 87
Exceptional Exposure -------------------------------------------------------------------------------------------------------------------------------40
3:40
7 10 17 22 22 22 22 34 113
45
3:20
1 10 16 22 22 22 22 22 70 113
50
3:20
4 14 22 22 22 22 22 22 106 113
55
3:20
6 22 22 22 22 22 22 46 113 113
60
3:20
15 22 22 22 22 22 27 72 113 114

6:40
20:00
49:00
81:40
109:40
159:20
218:00
273:00
323:40
372:40
413:40
454:40

205 FSW
5
6:50
0
6:50
10
5:30
1
4
4
8
22:50
15
4:50
2
4
5
9
9 19
53:10
20
4:30
3
5
9 10 11 22 22
86:50
25
4:10
2
9
9 10 15 22 22 22 115:30
30
3:50
1
9 10
9 18 22 22 22 59 176:10
35
3:50
7
9 10 20 22 22 22 22 100 238:10
Exceptional Exposure -------------------------------------------------------------------------------------------------------------------------------40
3:30
2 10
9 21 22 22 22 22 48 113 294:50
45
3:30
5 10 20 22 22 22 22 22 85 113 346:50
50
3:30
8 18 22 22 22 22 22 30 113 113 395:50
55
3:30
14 22 22 22 22 22 22 62 113 113 437:50
60
3:10
2 22 22 22 22 22 22 30 87 113 113 480:30

15-88

U.S. Navy Diving Manual — Volume 4

Closed-Circuit Mixed-Gas UBA Decompression Table Using 0.75 ata
Constant Partial Pressure Oxygen in Helium
Table 15-17. Closed-Circuit Mixed-Gas UBA Decompression Table Using 0.75 ata Constant Partial
Pressure Oxygen in Helium (Continued).
(DESCENT RATE 60 FPM—ASCENT RATE 30 FPM)

Bottom
Time
(min)

Time
DECOMPRESSION STOPS (fsw)
to First
Stop times (min) include travel time, except first stop
Stop
(M:S) 190 180 170 160 150 140 130 120 110 100 90 80 70 60 50 40

10

Total
Ascent
Time
(M:S)

30

20

0

7:00

2

4

4

9

25:00

5

7:00

10

5:40

15

5:00

20

4:20

25

4:20

30

4:00

35

3:40

1

4

3

6

10

9

20

57:20

1

4

6

10

9

13

22

22

91:40

5

9

9

10

17

22

22

26

124:40

4

10

9

9

21

22

23

22

68

192:20

10

9

11

22

22

22

22

22 112

257:00

Exceptional Exposure -------------------------------------------------------------------------------------------------------------------------------40

3:40

45

3:40

50

3:20

55
60

6

9

12

22

22

22

22

22

61 113

315:00

9

11

22

23

22

22

22

22 100 113

370:00

2

10

22

22

22

22

22

22

45 113 113

418:40

3:20

4

19

22

22

22

22

22

22

81 113 113

465:40

3:20

10

22

22

22

22

22

22

32 103 113 113

506:40

215 FSW
5

7:10

10

5:50

15

4:50

20

4:30

25

4:10

30

4:10

3

0

7:10

4

4

10

27:10
62:10

1

4

4

7

9

10

22

2

4

8

10

9

15

22

22

96:50

1

7

10

9

9

20

22

22

36

140:30

8

9

10

11

22

22

22

22

81

211:30

Exceptional Exposure -------------------------------------------------------------------------------------------------------------------------------35

3:50

5

10

9

14

22

22

22

22

35 113

278:10

40

3:30

1

9

10

15

22

22

22

22

22

77 113

338:50

45

3:30

4

9

15

22

22

22

23

22

24 113 113

392:50

50

3:30

6

14

22

22

22

22

22

22

62 113 114

444:50

55

3:30

9

22

22

22

22

22

22

23

97 113 113

490:50

60

3:30

19

22

22

22

22

22

22

41 112 113 113

533:50

0

7:20
29:00

220 FSW
5

7:20

10

5:40

15

5:00

20

4:40

25

4:20

30

4:00

2

1

4

4

5

9

3

3

4

9

9

11

22

66:20

4

4

9

10

9

17

22

22

102:00

3

8

10

9

10

22

22

22

45

155:40

10

9

9

14

22

22

22

22

93

229:20

Exceptional Exposure -------------------------------------------------------------------------------------------------------------------------------35

4:00

9

9

10

17

22

22

22

22

48 113

40

3:40

5

9

9

19

22

22

22

22

22

92 113

361:00

45

3:40

8

9

19

22

22

22

22

22

41 113 113

417:00

50

3:20

1

10

17

22

22

22

22

22

22

80 113 113

469:40

55

3:20

3

15

22

22

22

22

22

22

30 108 113 113

517:40

CHAPTER 15 — EC-UBA Diving

298:20

15-89

Closed-Circuit Mixed-Gas UBA Decompression Table Using 0.75 ata ppO2 HeO2 (Continued)

210 FSW

Closed-Circuit Mixed-Gas UBA Decompression Table Using 0.75 ata
Constant Partial Pressure Oxygen in Helium
Table 15-17. Closed-Circuit Mixed-Gas UBA Decompression Table Using 0.75 ata Constant Partial
Pressure Oxygen in Helium (Continued).
(DESCENT RATE 60 FPM—ASCENT RATE 30 FPM)

Bottom
Time
(min)

Time
DECOMPRESSION STOPS (fsw)
to First
Stop times (min) include travel time, except first stop
Stop
(M:S) 190 180 170 160 150 140 130 120 110 100 90 80 70 60 50 40

30

20

10

Total
Ascent
Time
(M:S)

7:30

225 FSW
Closed-Circuit Mixed-Gas UBA Decompression Table Using 0.75 ata ppO2 HeO2 (Continued)

4

7:30

0

5

7:10

1

8:30

10

5:50

15

5:10

20

4:30

2

25

4:10

1

5

30

4:10

6

9

2

4

4

6

9

31:10

4

9

10

12

22

70:30

4

4

4

5

10

9

9

19

22

22

106:50

9

9

10

12

22

22

22

56

172:30

9

10

16

22

22

23

22 104

247:30

Exceptional Exposure -------------------------------------------------------------------------------------------------------------------------------35

3:50

3

10

40

3:50

45

3:30

3

50

3:30

55

3:30

9

10

20

8
9

5
7

22

22

22

22

61 113

318:10

10

9

22

22

22

22

22

22 106 113

382:10

10

22

22

22

22

22

22

56 113 113

439:50

10

21

22

22

22

22

22

22

97 113 113

494:50

19

22

22

22

22

22

22

42 113 113 114

543:50

7:40

230 FSW
4

7:40

0

5

7:20

2

9:40

10

6:00

33:20

15

5:00

20

4:40

25

4:20

30

4:20

3

4

4

7

9

2

4

3

6

9

9

14

22

74:20

3

4

7

9

10

9

21

22

22

112:00

2

7

9

10

9

14

22

22

22

66

187:40

9

10

9

9

20

22

22

22

26 113

266:40

Exceptional Exposure -------------------------------------------------------------------------------------------------------------------------------35

4:00

40

3:40

3

7

9

10

10

22

22

22

22

22

74 113

337:20

9

10

13

22

22

22

22

22

31 113 113

406:00

45

3:40

7

9

14

22

22

22

22

22

22

74 113 113

466:00

50

3:40

9

13

22

22

22

22

22

22

27 109 113 113

520:00

55

3:20

10

22

22

22

23

22

22

22

60 113 113 113

569:40

0

7:50

2

235 FSW
4

7:50

5

7:30

10

5:50

15

5:10

20

4:30

1

25

4:30

30

4:10

4

3

10:50

1

4

3

4

8

10

36:10

3

4

4

6

10

9

15

22

78:30

4

4

8

10

9

10

22

22

22

116:50

4

8

9

10

9

17

22

22

22

76

203:50

9

9

10

9

22

22

22

22

38 113

284:30

Exceptional Exposure -------------------------------------------------------------------------------------------------------------------------------35

3:50

2

9

9

10

13

22

22

23

22

22

88 113

359:10

40

3:50

7

9

10

16

22

22

22

22

22

46 113 113

428:10

45

3:30

1

10

9

17

23

22

22

22

22

22

90 113 113

489:50

50

3:30

4

9

17

22

22

22

22

22

22

40 113 113 113

544:50

15-90

U.S. Navy Diving Manual — Volume 4

Closed-Circuit Mixed-Gas UBA Decompression Table Using 0.75 ata
Constant Partial Pressure Oxygen in Helium
Table 15-17. Closed-Circuit Mixed-Gas UBA Decompression Table Using 0.75 ata Constant Partial
Pressure Oxygen in Helium (Continued).
(DESCENT RATE 60 FPM—ASCENT RATE 30 FPM)

Bottom
Time
(min)

Time
DECOMPRESSION STOPS (fsw)
to First
Stop times (min) include travel time, except first stop
Stop
(M:S) 190 180 170 160 150 140 130 120 110 100 90 80 70 60 50 40

30

20

10

Total
Ascent
Time
(M:S)

4

8:00

0

8:00

5

7:40

3

11:00

10

6:00

15

5:00

20

4:40

25

4:20

2

2

4

4

3

9

10

38:20

1

4

4

3

8

9

10

17

22

83:20

3

3

5

9

10

9

12

22

22

32

132:00

4

10

9

9

10

19

22

22

22

87

220:40

Exceptional Exposure -------------------------------------------------------------------------------------------------------------------------------30

4:20

35

4:00

5

7

9

10

9

12

22

22

22

22

51 113

303:40

10

9

10

16

22

22

22

22

22 104 113

381:20

40

3:40

1

10

9

10

19

22

22

22

22

22

60 113 113

449:00

45

3:40

5

10

9

21

22

22

22

22

22

22 107 113 113

514:00

50

3:40

8

9

21

22

22

22

22

22

22

58 113 113 113

571:00

245 FSW
5

7:30

10

6:10

15

5:10

20

4:50

25

4:30

1

3

4

12:50
41:30

3

4

4

4

9

11

2

4

4

4

9

9

9

19

22

87:30

4

4

6

9

10

9

14

22

22

41

146:10

6

10

9

10

9

21

22

22

22

98

236:50

Exceptional Exposure -------------------------------------------------------------------------------------------------------------------------------30

4:10

1

10

9

10

9

15

22

22

22

22

64 113

323:30

35

4:10

9

9

10

9

20

22

22

22

22

27 113 113

402:30

40

3:50

5

10

9

11

22

22

22

22

22

22

77 114 113

475:10

45

3:50

9

10

12

22

22

22

22

22

22

33 113 113 113

539:10

50

3:30

9

12

22

22

22

22

22

23

22

75 113 114 113

597:50

1

4

13:00

4

4

4

5

9

12

44:40

3

250 FSW
5

7:40

10

6:20

15

5:20

20

4:40

25

4:20

1

3

4

4

5

9

9

10

20

22

91:40

2

4

4

7

9

10

9

16

22

22

50

160:00

4

8

9

10

9

11

22

22

22

22 110

254:40

Exceptional Exposure -------------------------------------------------------------------------------------------------------------------------------30

4:20

5

9

10

9

10

17

22

22

22

22

35

4:00

4

9

9

10

10

22

22

22

22

22

41 113 114

424:20

40

4:00

9

9

10

14

22

22

22

22

22

22

94 113 113

498:20

45

3:40

4

9

10

16

22

22

22

22

22

22

51 113 113 113

565:00

50

3:40

7

9

16

22

22

22

22

22

22

22

95 113 113 113

624:00

CHAPTER 15 — EC-UBA Diving

78 113

343:40

15-91

Closed-Circuit Mixed-Gas UBA Decompression Table Using 0.75 ata ppO2 HeO2 (Continued)

240 FSW

Closed-Circuit Mixed-Gas UBA Decompression Table Using 0.75 ata
Constant Partial Pressure Oxygen in Helium
Table 15-17. Closed-Circuit Mixed-Gas UBA Decompression Table Using 0.75 ata Constant Partial
Pressure Oxygen in Helium (Continued).
(DESCENT RATE 60 FPM—ASCENT RATE 30 FPM)

Bottom
Time
(min)

Time
DECOMPRESSION STOPS (fsw)
to First
Stop times (min) include travel time, except first stop
Stop
(M:S) 190 180 170 160 150 140 130 120 110 100 90 80 70 60 50 40

30

20

10

Total
Ascent
Time
(M:S)

255 FSW
Closed-Circuit Mixed-Gas UBA Decompression Table Using 0.75 ata ppO2 HeO2 (Continued)

5

7:50

10

6:10

15

5:10

20

4:50

25

4:30

3

2

4

14:10

1

4

4

4

6

10

12

47:30

1

4

4

4

5

10

9

10

22

22

96:30

3

4

4

9

9

10

9

18

22

22

59

174:10

4

9

10

9

10

13

22

22

22

31 113

272:50

Exceptional Exposure -------------------------------------------------------------------------------------------------------------------------------30

4:10

1

8

9

10

9

9

21

22

22

22

22

35

4:10

7

10

9

9

14

22

22

22

22

22

56 113 113

445:30

40

3:50

9

10

9

17

22

22

22

22

22

25 107 113 113

521:10

45

3:50

8

9

10

19

22

22

22

22

22

22

68 113 113 113

589:10

50

3:30

9

10

20

22

22

22

22

22

22

32 104 113 113 113

651:50

2

4

4

4

4
2

91 113

363:30

260 FSW
5

8:00

10

6:20

15

5:20

20

4:40

25

4:20

1

3

4

15:20

7

10

14

51:40

2

4

4

4

7

9

10

11

22

22

100:40

1

4

4

5

9

10

9

9

20

22

22

69

189:00

4

5

10

9

10

9

16

22

22

22

43 113

290:40

Exceptional Exposure -------------------------------------------------------------------------------------------------------------------------------30

4:20

3

9

10

9

9

11

22

22

22

22

22 105 113

383:40

35

4:00

2

9

10

9

9

17

22

22

22

22

22

72 113 113

468:20

40

4:00

8

9

9

10

20

22

22

23

22

22

34 113 113 113

544:20

45

3:40

9

9

11

22

22

22

22

22

22

22

86 113 113 113

615:00

3

265 FSW
5

8:10

10

6:30

15

5:30

20

4:50

25

4:30

4
2

4

4

16:30

4

3

4

4

8

10

15

54:50

4

3

4

9

9

9

13

22

22

104:50

3

4

3

7

9

10

9

9

22

22

22

78

203:10

4

8

9

10

9

9

18

22

22

22

55 113

307:50

Exceptional Exposure -------------------------------------------------------------------------------------------------------------------------------30

4:30

35

4:10

40

3:50

45

3:50

15-92

6

10

9

9

10

13

22

22

22

22

27 113 113

5

10

9

10

9

19

22

23

22

22

22

87 113 113

402:50
490:30

2

10

9

10

11

22

22

22

22

22

22

52 113 113 113

569:10

7

9

9

15

22

22

22

22

22

22

26 100 113 113 113

641:10

U.S. Navy Diving Manual — Volume 4

Closed-Circuit Mixed-Gas UBA Decompression Table Using 0.75 ata
Constant Partial Pressure Oxygen in Helium
Table 15-17. Closed-Circuit Mixed-Gas UBA Decompression Table Using 0.75 ata Constant Partial
Pressure Oxygen in Helium (Continued).
(DESCENT RATE 60 FPM—ASCENT RATE 30 FPM)

Bottom
Time
(min)

Time
DECOMPRESSION STOPS (fsw)
to First
Stop times (min) include travel time, except first stop
Stop
(M:S) 190 180 170 160 150 140 130 120 110 100 90 80 70 60 50 40

30

20

10

Total
Ascent
Time
(M:S)

17:20

5

8:00

10

6:20

15

5:20

20

5:00

25

4:40

4

1

4

4

1

4

4

4

4

9

9

16

57:40

1

4

4

4

4

9

10

9

15

22

22

109:40

4

4

4

8

9

9

10

11

22

22

22

88

218:20

4

9

9

10

9

10

20

22

22

22

66 113

325:00

Exceptional Exposure -------------------------------------------------------------------------------------------------------------------------------30

4:20

2

8

9

10

9

10

16

22

22

22

22

35

4:20

9

9

10

9

10

22

22

22

22

22

22 102 113 113

511:40

40

4:00

6

9

10

9

15

22

22

22

22

22

22

69 113 113 113

593:20

45

3:40

10

9

10

18

22

22

22

22

22

22

37 107 113 113 113

667:00

2

4

4

18:30

2

4

4

4

4

10

9

18

61:50

1

41 113 113

423:40

275 FSW
5

8:10

10

6:30

15

5:30

20

4:50

2

4

3

4

3

4

5

10

9

10

16

22

24

115:50

4

4

9

9

10

9

14

22

22

22

99

235:10

Exceptional Exposure -------------------------------------------------------------------------------------------------------------------------------25

4:30

2

4

5

9

10

9

10

10

22

22

22

22

79 113

343:50

30

4:30

4

9

10

9

10

9

19

22

22

22

22

55 113 113

443:50

35

4:10

4

9

9

10

9

13

22

22

22

22

22

32 108 113 113

534:30

40

3:50

1

9

10

9

9

19

22

22

22

22

22

22

86 113 113 114

619:10

45

3:50

5

10

9

9

22

22

22

22

22

22

22

48 113 113 113 113

691:10

3

4

4

4

280 FSW
5

8:20

10

6:40

15

5:40

20

5:00

3

4

3

4

3

18:40

5

10

9

19

65:00

4

4

4

4

6

9

10

9

18

22

32

128:00

4

5

10

9

10

9

15

23

22

22 109

250:20

Exceptional Exposure -------------------------------------------------------------------------------------------------------------------------------25

4:40

30

4:20

3

4

7

10

9

10

9

12

22

22

22

22

92 113

362:00

2

6

9

10

9

10

9

21

22

22

22

22

70 113 113

464:40

35

4:20

7

10

9

9

10

16

22

22

22

22

22

43 113 113 113

557:40

40

4:00

4

10

9

10

9

22

22

22

22

22

22

26

99 113 113 113

642:20

45

4:00

9

9

10

13

22

22

22

22

22

22

22

68 113 113 113 113

719:20

CHAPTER 15 — EC-UBA Diving

15-93

Closed-Circuit Mixed-Gas UBA Decompression Table Using 0.75 ata ppO2 HeO2 (Continued)

270 FSW

Closed-Circuit Mixed-Gas UBA Decompression Table Using 0.75 ata
Constant Partial Pressure Oxygen in Helium
Table 15-17. Closed-Circuit Mixed-Gas UBA Decompression Table Using 0.75 ata Constant Partial
Pressure Oxygen in Helium (Continued).
(DESCENT RATE 60 FPM—ASCENT RATE 30 FPM)

Bottom
Time
(min)

Time
DECOMPRESSION STOPS (fsw)
to First
Stop times (min) include travel time, except first stop
Stop
(M:S) 190 180 170 160 150 140 130 120 110 100 90 80 70 60 50 40

30

20

10

Total
Ascent
Time
(M:S)

19:50

285 FSW
Closed-Circuit Mixed-Gas UBA Decompression Table Using 0.75 ata ppO2 HeO2 (Continued)

5

8:30

10

6:30

15

5:30

20

4:50

1

4

3

4

4

1

4

4

3

4

7

9

10

20

68:50

2

4

4

3

4

8

9

10

9

21

22

40

141:50

4

4

7

9

9

10

9

18

22

22

29 113

266:10

Exceptional Exposure -------------------------------------------------------------------------------------------------------------------------------25

4:30

1

4

4

9

9

10

9

10

14

22

22

22

23 104 113

30

4:30

3

8

10

9

10

9

11

22

22

22

22

22

84 113 113

484:50

35

4:10

2

9

10

9

9

10

19

22

22

22

22

22

59 113 113 113

580:30

40

4:10

8

10

9

10

12

22

22

22

22

22

22

38 104 113 113 113

666:30

45

3:50

9

10

9

17

22

22

22

22

22

22

22

87 113 113 113 113

746:10

1

4

3

5

2

4

4

4

3

8

9

10

22

73:00

4

380:50

290 FSW
5

8:20

10

6:40

15

5:40

20

5:00

3

4

21:40

3

4

4

4

4

8

10

9

10

22

22

48

154:00

3

4

9

9

9

10

9

20

22

22

40 113

282:20

Exceptional Exposure -------------------------------------------------------------------------------------------------------------------------------25

4:40

3

4

5

9

9

10

9

10

17

22

22

22

31 109 113

30

4:20

1

5

9

10

9

9

10

14

22

22

22

22

23

99 113 113

400:00
507:40

35

4:20

5

10

9

10

9

10

22

22

22

22

22

22

76 113 113 113

604:40

40

4:00

3

9

10

9

10

15

22

23

22

22

22

22

49 111 113 113 113

692:20

45

4:00

8

9

10

9

20

22

22

22

22

22

22

31

95 113 113 113 113

770:20

3

4

4

4

295 FSW
5

8:30

10

6:50

15

5:30

20

4:50

1

3

1

4

4

5

22:50

3

9

9

11

22

76:10

1

4

4

3

4

5

9

10

9

12

22

22

56

166:50

4

4

4

10

9

10

9

10

22

22

22

50 113

298:10

Exceptional Exposure -------------------------------------------------------------------------------------------------------------------------------25

4:30

1

4

4

6

10

9

9

10

9

20

22

22

22

41 112 113

418:50

30

4:30

3

6

10

9

9

10

9

17

22

22

22

22

33 103 113 113

527:50

35

4:30

40

4:10

45

3:50

15-94

2

9

9

10

9

10

12

22

22

22

22

22

23

91 113 113 113

626:50

7

9

10

9

9

20

22

22

22

22

22

22

66 113 113 113 113

718:30

10

9

10

11

22

22

22

22

22

22

22

43 102 113 113 113 113

797:10

U.S. Navy Diving Manual — Volume 4

Closed-Circuit Mixed-Gas UBA Decompression Table Using 0.75 ata
Constant Partial Pressure Oxygen in Helium
Table 15-17. Closed-Circuit Mixed-Gas UBA Decompression Table Using 0.75 ata Constant Partial
Pressure Oxygen in Helium (Continued).
(DESCENT RATE 60 FPM—ASCENT RATE 30 FPM)

Bottom
Time
(min)

Time
DECOMPRESSION STOPS (fsw)
to First
Stop times (min) include travel time, except first stop
Stop
(M:S) 190 180 170 160 150 140 130 120 110 100 90 80 70 60 50 40

30

20

10

Total
Ascent
Time
(M:S)

25:00

5

8:40

10

7:00

15

5:40

20

5:00

2

4

2

4

4

6

4

4

4

4

4

9

9

12

22

79:20

2

4

4

4

4

5

10

9

10

14

22

22

64

180:00

4

4

5

10

9

10

9

12

22

22

22

62 113

315:20

Exceptional Exposure -------------------------------------------------------------------------------------------------------------------------------25

4:40

2

4

4

8

10

9

10

9

9

22

22

23

22

30

4:20

1

4

8

9

10

9

10

9

20

22

22

22

22

43 108 113 113

549:40

35

4:20

4

9

9

10

9

10

15

22

22

22

22

23

32

97 113 113 113

649:40

40

4:00

10

9

10

9

10

22

22

22

22

22

22

22

83 113 113 113 113

742:20

1

51 113 113

436:00

310 FSW
Exceptional Exposure -------------------------------------------------------------------------------------------------------------------------------6

8:20

10

7:00

15

5:40

20

5:00

1

25

4:40

2

4

30

4:40

4

35

4:20

2

40

4:20

9

1

4

4

4

3

7

6

10

9

10

9

10

1

4

4

4

6

9

2

4

4

4

4

6

9

10

15

22

36:40
87:20

4

8

9

9

10

18

22

22

81

206:00

4

4

4

4

4

8

10

9

10

9

17

22

22

22

85 113

349:20

9

10

9

9

10

14

22

22

22

22

81 113 113

477:00

9

10

9

10

12

22

22

22

22

22

69 113 113 113

593:00

9

9

10

9

22

22

22

22

22

22

54 109 113 113 113

696:40

9

10

16

22

22

22

22

23

22

41

98 113 113 113 113

791:40

320 FSW
Exceptional Exposure -------------------------------------------------------------------------------------------------------------------------------6

8:40

10

7:00

15

6:00

20

5:20

4

4

25

4:40

1

4

4

4

30

4:40

3

5

10

9

35

4:20

1

8

10

9

10

40

4:20

7

10

9

10

9

4

CHAPTER 15 — EC-UBA Diving

3

4

4

4

7

10

1

4

4

4

4

4

7

10

9

19

22

41:00
95:20

4

4

5

10

9

9

10

22

22

22

98

232:20
383:40

3

4

4

4

6

9

10

9

9

10

22

22

22

28 102 113

9

10

9

10

9

10

19

22

22

22

34

96 113 113

516:00

9

10

9

10

18

22

22

22

22

31

91 113 113 113

637:00

9

9

16

22

22

22

22

22

24

84 113 113 113 113

746:40

11

22

22

22

22

22

22

22

66 112 113 113 113 113

844:40

15-95

Closed-Circuit Mixed-Gas UBA Decompression Table Using 0.75 ata ppO2 HeO2 (Continued)

300 FSW

PAGE LEFT BLANK INTENTIONALLY

15-96

U.S. Navy Diving Manual — Volume 4

				

16-1

CHAPTER 16

Closed-Circuit Oxygen UBA
(CC-UBA) Diving

INTRODUCTION

The term closed-circuit oxygen rebreather
describes a specialized underwater breathing
apparatus (CC-UBA) in which the diver
breathes 100% oxygen and all gases are kept
within the UBA (Figure 16-1). The use of
100% oxygen prevents inert gas buildup in
the diver and allows all of the gas carried
by the diver to be used for metabolic needs.
The exhaled gas is carried via the exhalation
hose to a carbon dioxide-absorbent bed,
which removes the carbon dioxide produced
by the diver through a chemical reaction.
Metabolically consumed oxygen is then
replaced through an oxygen addition system.
The gas then travels to the breathing bag
where it is available again to the diver. CCUBAs offer advantages valuable to special
warfare, including stealth (no escaping
bubbles), extended operating duration, and
less weight than open-circuit air SCUBA.
Figure 16-1. Diver in MK-25 CCUBA.
Weighed against these advantages are the
disadvantages of increased hazards to the
diver, greater training requirements, and
greater expense. However, when compared to a EC-UBA, a CC-UBA offers the
advantages of reduced training and maintenance requirements, lower cost, and
reduction in weight and size.
16-1.1

Purpose. This chapter provides general guidance for CC-UBA diving operations

and proce­dures. For detailed operation and maintenance instructions see the UBA
Operation and Maintenance Manual.
16-1.2

Scope. This chapter covers closed-circuit oxygen UBA principles of operations,

operational planning, dive procedures, and medical aspects of closed-circuit
oxygen diving.

16-2

MEDICAL ASPECTS OF CLOSED-CIRCUIT OXYGEN DIVING

Closed-circuit oxygen divers are subject to many of the same medical problems as
other divers. Chapter 3 provides in-depth coverage of all medical considerations of

CHAPTER 16 — Closed-Circuit Oxygen CC-UBA Diving

16-1

diving. Only the diving disorders that merit special attention for CC-UBA divers
are addressed in this chapter.
16-2.1

Central Nervous System (CNS) Oxygen Toxicity. High pressure oxygen poison-

ing is known as CNS oxygen toxicity. High partial pressures of oxygen are
associated with many biochemical changes in the brain, but which specific changes
are responsible for the signs and symptoms of CNS oxygen toxicity is presently
unknown. CNS oxygen toxicity is not likely to occur at oxygen partial pressures
below 1.3 ata, though relatively brief exposure to partial pressures above this,
when it occurs at depth or in a pressurized chamber, can result in CNS oxygen
toxicity causing CNS-related symptoms.

16‑2.1.1

Symptoms of CNS Oxygen Toxicity. In diving, the most serious effects of oxygen

toxicity are CNS symptoms. There may be no warning of an impending convulsion
to provide the diver the opportunity to return to the surface. Therefore, buddy lines
are essen­tial to safe closed-circuit oxygen diving.
16‑2.1.2

Treatment of Nonconvulsive Symptoms. The stricken diver should alert his dive

buddy and make a controlled ascent to the surface. The victim’s life preserver
should be inflated (if necessary) with the dive buddy watching him closely for
progression of symptoms. Though an ascent from depth will lower the partial
pressure of oxygen, the diver may still suffer other or worsening symptoms. The
divers should notify the Diving Supervisor and termi­nate the dive.
16‑2.1.3

Treatment of Underwater Convulsion. The following steps should be taken when

treating a convulsing diver:

1. Assume a position behind the convulsing diver. The weight belt should be left

in place to prevent the diver from assuming a face down position on the surface.
Release the victim’s weight belt only if progress to the surface is significantly
impeded.

2. Leave the victim’s mouthpiece in his mouth. If it is not in his mouth, do not

attempt to replace it; however, if time permits, ensure that the mouthpiece is
switched to the SURFACE position.

3. Grasp the victim around his chest above the UBA or between the UBA and

his body. If difficulty is encountered in gaining control of the victim in this
manner, the rescuer should use the best method possible to obtain control. The
UBA harnesses may be grasped if necessary.

4. Make a controlled ascent to the surface, maintaining a slight pressure on the

diver’s chest to assist exhalation.

5. If additional buoyancy is required, activate the victim’s life jacket. The rescuer

should not release his own weight belt or inflate his own life jacket.

6. Upon reaching the surface, inflate the victim’s life jacket if not previously

done.

7. Remove the victim’s mouthpiece and switch the valve to SURFACE to prevent

the possibility of the rig flooding and weighing down the victim.

8. Signal for emergency pickup.

16-2

U.S. Navy Diving Manual — Volume 4

9. Once the convulsion has subsided, open the victim’s airway by tilting his head

back slightly.

10. Ensure the victim is breathing. Mouth-to-mouth breathing may be initiated if

necessary.

11. If an upward excursion occurred during the actual convulsion, transport to the

nearest appropriate chamber and have the victim evaluated by an individual
trained to recognize and treat diving-related illness.

16‑2.1.4

Off-Effect. The off-effect, a hazard associated with CNS oxygen toxicity, may

occur several minutes after the diver comes off gas or experiences a reduction of
oxygen partial pressure. The off-effect is manifested by the onset or worsening of
CNS oxygen toxicity symptoms. Whether this paradoxical effect is truly caused
by the reduc­tion in partial pressure or whether the association is coincidental is
unknown.
16-2.2

Pulmonary Oxygen Toxicity. Pulmonary oxygen toxicity can result from

prolonged exposure to elevated partial pressures of oxygen. This form of oxygen
toxicity produces lung irritation with symptoms of chest pain, cough, and pain
on inspiration that develop slowly and become increasingly worse as long as the
elevated level of oxygen is breathed. Although hyperbaric oxygen may cause
serious lung damage, if the oxygen expo­sure is discontinued before the symptoms
become too severe, the symptoms will slowly abate. This form of oxygen toxicity
is generally seen during oxygen recom­pression treatment and saturation diving,
and on long, shallow, in-water oxygen exposures.
16-2.3

16‑2.3.1

16‑2.3.2

Oxygen Deficiency (Hypoxia). Hypoxia is an abnormal deficiency of oxygen in
the arterial blood in which the partial pressure of oxygen is too low to meet the
metabolic needs of the body. Chapter 3 contains an in-depth description of this
disorder. Although all cells in the body need oxygen, the initial symptoms of
hypoxia are a manifestation of central nervous system dysfunction.
Causes of Hypoxia. The primary cause of hypoxia in the CC-UBA is inadequate/
incorrect purge of the CC-UBA. The risk of hypoxia is greatest when the diver is
breathing the CC-UBA on the surface. Oxygen is only added on a demand basis as
the breathing bag is emptied on inhalation. On the surface as the diver consumes
oxygen, the oxygen fraction in the breathing loop will begin to decrease, as will
the gas volume in the breathing bag. If there is sufficient nitrogen in the breathing
loop to prevent the breathing bag from being emptied no oxygen will be added
and the oxygen fraction may drop to ten percent or lower. Since there is sufficient
gas volume in the breathing bag for normal inhalation, hypoxia can occur without
warning. Hypoxia on descent or while diving is less likely, because as the diver
descends pure oxygen is added to the breathing loop to maintain volume which
increases both the oxygen fraction in the breathing loop and the oxygen partial
pressure.
UBA Purge Procedures. The detailed purge procedures in the UBA Operation and
Maintenance Manual are designed to remove as much of the inert gas (nitrogen)
from a diver’s lungs as possible prior to the start of a dive and have been thoroughly

CHAPTER 16 — Closed-Circuit Oxygen CC-UBA Diving

16-3

tested. They ensure the oxygen fraction in the breathing loop is sufficiently high
to prevent the occur­rence of hypoxia. The purge procedures should be strictly
followed.
16‑2.3.3

16‑2.3.4

Underwater Purge. If the diver conducts an underwater purge or purge under
pressure, the increase in oxygen fraction caused by volume make up described
above may not occur and the diver may be more susceptible to hypoxia. Therefore,
strict adherence to the under pressure purge procedures prescribed in the operations
and maintenance manual is extremely important.
Symptoms of Hypoxia. Hypoxia may have no warning symptoms prior to loss

of consciousness. Other symptoms that may appear include confusion, loss of
coordination, dizziness, and convulsion. It is important to note that if symptoms of
unconsciousness or convul­sion occur at the beginning of a CC-UBA dive, hypoxia,
not oxygen toxicity, is the most likely cause.
16‑2.3.5

Treatment of Hypoxia. Treatment for a suspected case of hypoxia consists of the

following:

n If the diver becomes unconscious or incoherent at depth, the dive buddy should
add oxygen to the stricken diver’s UBA.
n The diver must be brought to the surface. Remove the mouthpiece and allow the
diver to breathe fresh air. Switch mouth­piece valve to the SURFACE position.
If unconscious, check breathing and circulation, maintain an open airway and
administer 100-percent oxygen.
n If the diver surfaces in an unconscious state, follow the guidance in Section
17-3.
16-2.4

Carbon Dioxide Toxicity (Hypercapnia). Carbon dioxide toxicity, or hypercapnia,
is an abnormally high level of carbon dioxide in the blood and body tissues.
Hypercapnia is generally the result of a buildup of carbon dioxide in the breathing
supply or in the body. Inadequate venti­lation (breathing volume) by the diver or
failure of the carbon dioxide-absorbent canister to remove carbon dioxide from the
exhaled gas will cause a buildup to occur.

It is important to note that the presence of a high partial pressure of oxygen may
reduce the early symptoms of hypercapnia.
16‑2.4.1

Treating Hypercapnia. To treat hypercapnia:

n Increase ventilation if skip-breathing is a possible cause.
n Decrease exertion level.
n Abort the dive. Return to the surface and breathe air.

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U.S. Navy Diving Manual — Volume 4

n During ascent, while maintaining a vertical position, the diver should activate
his bypass valve, adding fresh oxygen to his UBA. If the symptoms are a result
of canister floodout, an upright position decreases the likelihood that the diver
will sustain chemical injury (paragraph 16‑2.5).
n If unconsciousness occurs at depth, the same principles of management for
underwater convulsion as described in paragraph 16‑2.1.3 apply.
16‑2.4.2

Prevention of Hypercapnia. To minimize the risk of hypercapnia:

n Use only an approved carbon dioxide absorbent in the CC-UBA canister.
n Follow the prescribed canister-filling procedure to ensure that the canister is
correctly packed with carbon dioxide absorbent.
n Dip test the UBA carefully before the dive. Watch for leaks that may result in
canister floodout.
n Do not exceed canister duration limits for the water temperature.
n Ensure that the one-way valves in the supply and exhaust hoses are installed
and working properly.
n Swim at a relaxed, comfortable pace.
n Avoid skip-breathing. There is no advantage to this type of breathing in a
closed-circuit rig and it may cause elevated blood carbon dioxide levels even
with a properly functioning canister.
16-2.5

16‑2.5.1

16‑2.5.2

Chemical Injury. The term “chemical injury” refers to the introduction of a caustic
solution from the carbon dioxide scrubber of the CC-UBA into the upper airway of
a diver.
Causes of Chemical Injury. The caustic alkaline solution results from water
leaking into the canister and coming in contact with the carbon dioxide absorbent.
When the diver is in a hori­zontal or head-down position, this solution may travel
through the inhalation hose and irritate or injure his upper airway.
Symptoms of Chemical Injury. The diver may experience rapid breathing or

headache, which are symptoms of carbon dioxide buildup in the breathing gas.
This occurs because an accumulation of the caustic solution in the canister may be
impairing carbon dioxide absorption. If the problem is not corrected promptly, the
alkaline solution may travel into the breathing hoses and consequently be inhaled
or swallowed. Choking, gagging, foul taste, and burning of the mouth and throat
may begin immediately. This condition is sometimes referred to as a “caustic
cocktail.” The extent of the injury depends on the amount and distribution of the
solution.

CHAPTER 16 — Closed-Circuit Oxygen CC-UBA Diving

16-5

16‑2.5.3

Treatment of a Chemical Incident. If the caustic solution enters the mouth, nose,

or face mask, the diver must take the following steps:

n Immediately assume an upright position in the water.
n Depress the manual bypass valve continuously and make a controlled ascent to
the surface, exhaling through the nose to prevent overpressurization.
n Should signs of system flooding occur during underwater purging, abort the
dive and return to open-circuit if possible.
Using fresh water, rinse the mouth several times. Several mouthfuls should then
be swallowed. If only sea water is available, rinse the mouth, but do not swallow.
Other fluids may be substituted if available, but the use of weak acid solutions
(vinegar or lemon juice) is not recommended. Do not attempt to induce vomiting.
As a result of the chemical injury, the diver may have difficulty breathing properly
on ascent. He should be observed for signs of an arterial gas embolism and treated
if necessary. A Diving Medical Officer or a Diving Medical Technician/Special
Operations Technician should evaluate a victim of a chemical injury as soon as
possible. Respiratory distress, which may result from the chemical trauma to the
air passages, requires immediate hospitalization.
16‑2.5.4

Prevention of Chemical Injury. Chemical injuries are best prevented by the

performance of a careful dip test during predive set up to detect any system leaks.
Special attention should also be paid to the position of the mouthpiece rotary valve
upon water entry and exit to prevent the entry of water into the breathing loop.
Additionally, dive buddies should perform a careful leak check on each other
before leaving the surface at the start of a dive.
16-2.6

16‑2.6.1

Middle Ear Oxygen Absorption Syndrome. Middle ear oxygen absorption
syndrome refers to the negative pressure that may develop in the middle ear
following a long oxygen dive.
Causes of Middle Ear Oxygen Absorption Syndrome. Gas with a very high

percentage of oxygen enters the middle ear cavity during the course of an
oxygen dive. Following the dive, the oxygen is slowly absorbed by the tissues
of the middle ear. If the Eustachian tube does not open spontaneously, a negative
pressure relative to ambient may result in the middle ear cavity. There may also be
fluid (serous otitis media) present in the middle ear as a result of the differential
pressure.

16‑2.6.2

Symptoms of Middle Ear Oxygen Absorption Syndrome. Symptoms are often

noted the morning after a long oxygen dive and include:

n A sense of pressure or mild discomfort in one or both ears.
n Muffled hearing in one or both ears.

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U.S. Navy Diving Manual — Volume 4

n A moist, crackling sensation in one or both ears as a result of fluid accumulation
in the middle ear.
16‑2.6.3

Treating Middle Ear Oxygen Absorption Syndrome. Equalizing the pressure in the

middle ear using a normal Valsalva maneuver or the diver’s procedure of choice
(e.g., swallowing, yawning) will usually relieve the symptoms. Discomfort and
hearing loss resolve quickly, but the middle ear fluid is absorbed more slowly.
If symptoms persist, a Diving Medical Technician or Diving Medical Officer shall
be consulted.

16‑2.6.4

Prevention of Middle Ear Oxygen Absorption Syndrome. Middle ear oxygen

absorption syndrome is difficult to avoid but usually does not pose a significant
problem because symptoms are generally mild and easily elimi­nated. To prevent
Middle Ear Oxygen Absorption Syndrome the diver should perform several gentle
Valsalva maneuvers throughout the day after a long oxygen dive to ensure the
Eustachian tube remains open.
16-3

CLOSED-CIRCUIT OXYGEN EXPOSURE LIMITS

The U.S. Navy closed-circuit oxygen exposure limits have been extended and
revised to allow greater flexibility in closed-circuit oxygen diving operations. The
revised limits are divided into three categories: Transit with Excursion Limits,
Single Depth Limits, and Lock Out/In from Excursion Depth.
Oxygen Exposure Limit Testing. The Transit with Excursion Limits and SingleDepth Limits have been tested extensively over the entire depth range and are
acceptable for routine diving oper­ations. They are not considered exceptional
exposure. It must be noted that the limits shown in this section apply only to closedcircuit 100-percent oxygen diving and are not applicable to deep mixed-gas diving.
Separate oxygen exposure limits have been established for deep, helium-oxygen
mixed-gas diving.
Individual Oxygen Susceptibility Precautions. Although the limits described
in this section have been thoroughly tested and are safe for the vast majority of
individuals, occasional episodes of CNS oxygen toxicity may occur. This is the
basis for requiring buddy lines on closed-circuit oxygen diving operations.
16-3.1

Transit with Excursion Limits. A 20 foot maximum depth for transit with one

excursion, if necessary, will be the preferred option in most combat swimmer
operations. When operational consider­ations necessitate a descent to deeper than
20 fsw for longer than allowed by the excursion limits, the appropriate singledepth limit should be used (Section 16-3.2).
16-3.1.1

Transit with Excursion Limits Table. The Transit with Excursion Limits (Table
16-1) call for a maximum dive depth of 20 fsw or shallower for the majority of the
dive, but allow the diver to make a brief excursion to depths as great as 50 fsw.
The Transit with Excursion Limits is normally the preferred mode of operation
because maintaining a depth of 20 fsw or shallower minimizes the possibility of

CHAPTER 16 — Closed-Circuit Oxygen CC-UBA Diving

16-7

CNS oxygen toxicity during the majority of the dive, yet allows a brief downward
excursion if needed (see Figure 16-2). Only a single excursion is allowed.
Table 16‑1. Excursion Limits.

16‑3.1.2

Depth

Maximum Time

21-40 fsw

15 minutes

41-50 fsw

5 minutes

Transit with Excursion Limits Definitions. The following definitions are illustrated

in Figure 16‑2:

n Transit is the portion of the dive spent at 20 fsw or shallower.
n Excursion is the portion of the dive deeper than 20 fsw.
n Excursion time is the time between the diver’s initial descent below 20 fsw and
his return to 20 fsw or shallower at the end of the excursion.
n Oxygen time is calculated as the time interval between when the diver
begins breathing from the CC-UBA (on-oxygen time) and the time when he
discontinues breathing from the CC-UBA (off-oxy­gen time).

20

Figure 16-2. Example of Transit with Excursion.

16-8

U.S. Navy Diving Manual — Volume 4

16‑3.1.3

Transit with Excursion Rules. A diver who has maintained a transit depth of 20

fsw or shallower may make one brief downward excursion as long as he observes
these rules:
n Maximum total time of dive (oxygen time) may not exceed 240 minutes.
n A single excursion may be taken at any time during the dive.

n The diver must have returned to 20 fsw or shallower by the end of the pre­
scribed excursion limit.
n The time limit for the excursion is determined by the maximum depth attained
during the excursion (Table 16‑1). Note that the Excursion Limits are different
from the Single-Depth Limits.
Example: Dive Profile Using Transit with Excursion Limits. A dive mission calls

for a swim pair to transit at 15 fsw for 45 minutes, descend to 36 fsw, and complete
their objective. As long as the divers do not exceed a maximum depth of 40 fsw,
they may use the 40-fsw excursion limit of 15 minutes. The time at which they
initially descend below 20 fsw to the time at which they finish the excursion must
be 15 minutes or less.

16‑3.1.4

Inadvertent Excursions. If an inadvertent excursion should occur, one of the

following situations will apply:

n If the depth and/or time of the excursion exceeds the limits in Table 16‑1 or if
an excursion has been taken previously, the dive must be aborted and the diver
must return to the surface.
n If the excursion was within the allowed excursion limits, the dive may be con­
tinued to the maximum allowed oxygen dive time, but no additional excursions
deeper than 20 fsw may be taken.
n The dive may be treated as a single-depth dive applying the maximum depth
and the total oxygen time to the Single-Depth Limits shown in Table 16‑2.
Example 1. A dive pair is having difficulty with a malfunctioning compass. They

have been on oxygen (oxygen time) for 35 minutes when they notice that their
depth gauge reads 55 fsw. Because this exceeds the maximum allowed oxygen
exposure depth, the dive must be aborted and the divers must return to the surface.
Example 2. A diver on a compass swim notes that his depth gauge reads 32 fsw.
He recalls checking his watch 5 minutes earlier and at that time his depth gauge
read 18 fsw. As his excursion time is less than 15 minutes, he has not exceeded
the excursion limit for 40 fsw. He may continue the dive, but he must maintain his
depth at 20 fsw or less and make no additional excursions.

NOTE

If the diver is unsure how long he was below 20 fsw, the dive must be
aborted.

CHAPTER 16 — Closed-Circuit Oxygen CC-UBA Diving

16-9

16-3.2

Single-Depth Limits. The term Single-Depth Limits does not mean that the entire

dive must be spent at one depth, but refers to the time limit applied to the dive
based on the maximum depth attained during the dive.
16-3.2.1

Single-Depth Oxygen Exposure Limits Table. The Single-Depth Limits (Table

16-2) allow maximum exposure at the greatest depth, but have a shorter overall
exposure time and do not allow for excursions. Single-depth limits may, however,
be useful when maximum bottom time is needed deeper than 20 fsw.

Table 16‑2. Single-Depth Oxygen Exposure Limits.

16‑3.2.2

Depth

Maximum Oxygen Time

25 fsw

240 minutes

30 fsw

80 minutes

35 fsw

25 minutes

40 fsw

15 minutes

50 fsw

10 minutes

Single-Depth Limits Definitions. The following definitions apply when using the

Single-Depth Limits:

n Oxygen time is calculated as the time interval between when the diver
begins breathing from the CC-UBA (on-oxygen time) and the time when he
discontinues breathing from the CC-UBA (off-oxy­gen time).
n The depth of the dive used for determining the allowable exposure time is
determined by the maximum depth attained during the dive. For intermediate
depth, the next deeper depth limit will be used.
16‑3.2.3

Depth/Time Limits. The Single-Depth Limits are provided in Table 16‑2. No

excursions are allowed when using these limits.

Example. Twenty-two minutes (oxygen time) into a compass swim, a dive pair

descends to 28 fsw to avoid the propeller of a passing boat. They remain at this
depth for 8 minutes. They now have two choices for calculating their allowed
oxygen time: (1) they may return to 20 fsw or shallower and use the time below
25 fsw as an excursion, allowing them to continue their dive on the Transit with
Excursion Limits to a maximum time of 240 minutes; or (2) they may elect to
remain at 28 fsw and use the 30-fsw Single-Depth Limits to a maximum dive time
of 80 minutes.

16‑3.3

Lock Out/In from Excursion Depth. Unique closed circuit applications may require

a closed circuit oxygen dive starting and ending from depth. The return to lock in
would be considered a second excursion, and single dive limits are not practical in
16-10

U.S. Navy Diving Manual — Volume 4

this setting. For closed circuit oxygen dives that begin and terminate at excursion
depth, the following guidance shall be used:
n The definitions in 16-3.1.2 and 16-3.1.3 apply to Lock Out/In.
n The dive begins on a lock out excursion not to exceed 50 fsw for 5 minutes.
n The diver ascends to 20 fsw or shallower and commences transit.
n No excursions during transit are allowed.
n The dive ends on a lock in excursion not to exceed 50 fsw for 5 minutes.
16-3.4

16‑3.4.1

Exposure Limits for Successive Oxygen Dives. If an oxygen dive is conducted
after a previous closed-circuit oxygen exposure, the effect of the previous dive
on the exposure limit for the subsequent dive is dependent on the Off-Oxygen
Interval.
Definitions for Successive Oxygen Dives. The following definitions apply when
using oxygen exposure limits for successive oxygen dives.

n Off-Oxygen Interval. The interval between off-oxygen time and on-oxygen
time is defined as the time from when the diver discontinues breathing from his
CC-UBA on one dive until he begins breathing from the UBA on the next dive.
n Successive Oxygen Dive. A successive oxygen dive is one that follows a pre­
vious oxygen dive after an Off-Oxygen Interval of less than 2 hours.
16‑3.4.2

NOTE

Off-Oxygen Exposure Limit Adjustments. If an oxygen dive is a successive oxygen
dive, the oxygen exposure limit for the dive must be adjusted as shown in Table
16‑3. If the Off-Oxygen Interval is 2 hours or greater, no adjustment is required
for the subsequent dive. An oxygen dive undertaken after an Off-Oxygen Interval
of more than 2 hours is considered to be the same as an initial oxygen exposure. If
a negative number is obtained when adjusting the single-depth exposure limits as
shown in Table 16‑3, a 2-hour Off-Oxygen Interval must be taken before the next
oxygen dive.

A maximum of 4 hours oxygen time is permitted within a 24-hour period.
Example. Ninety minutes after completing a previous oxygen dive with an oxygen

time of 75 minutes (maximum dive depth 19 fsw), a dive pair will be making
a second dive using the Transit with Excursion Limits. Calculate the amount of
oxygen time for the second dive, and determine whether an excursion is allowed.

CHAPTER 16 — Closed-Circuit Oxygen CC-UBA Diving

16-11

Table 16‑3. Adjusted Oxygen Exposure Limits for Successive Oxygen Dives.
Adjusted Maximum Oxygen Time

Excursion

Transit with
Excursion Limits

Subtract oxygen time on previous
dives from 240 minutes

Allowed if none taken on
previous dives

Single-Depth Limits

1.

No excursion allowed when
using Single-Depth Limits to
compute remaining oxygen
time

2.

Determine maximum oxygen
time for deepest exposure.
Subtract oxygen time on
previous dives from maximum
oxygen time in Step 1 (above)

Solution. The second dive is considered a successive oxygen dive because the Off-

Oxygen Interval was less than 2 hours. The allowed exposure time must be adjusted
as shown in Table 16‑3. The adjusted maximum oxygen time is 165 minutes (240
minutes minus 75 minutes previous oxygen time). A single excur­sion may be taken
because the maximum depth of the previous dive was 19 fsw.
Example. Seventy minutes after completing a previous oxygen dive (maximum

depth 28 fsw) with an oxygen time of 60 minutes, a dive pair will be making a
second oxygen dive. The maximum depth of the second dive is expected to be
25 fsw. Calculate the amount of oxygen time for the second dive, and determine
whether an excursion is allowed.

Solution. First compute the adjusted maximum oxygen time. This is determined

by the Single-Depth Limits for the deeper of the two exposures (30 fsw for 80
minutes), minus the oxygen time from the previous dive. The adjusted maximum
oxygen time for the second dive is 20 minutes (80 minutes minus 60 minutes
previous oxygen time). No excursion is permitted using the Single-Depth Limits.

16-3.5

Exposure Limits for Oxygen Dives Following Mixed-Gas or Air Dives. When a

subsequent dive must be conducted and if the previous exposure was an air or
pO.75 EC-UBA dive, the exposure limits for the subsequent oxygen dive require
no adjustment.

16‑3.5.1

16‑3.5.2

Mixed-Gas to Oxygen Rule. If the previous dive used a mixed-gas breathing mix
having an oxygen partial pressure of 1.0 ata or greater, the previous exposure must
be treated as a closed-circuit oxygen dive. In this case, the Off-Oxygen Interval is
calculated from the time the diver discontinued breathing the previous breathing
mix until he begins breathing from the closed-circuit oxygen rig.
Oxygen to Mixed-Gas Rule. If a diver employs the CC-UBA for a portion
of the dive and another UBA that uses a breathing gas other than oxygen for
another portion of the dive, only the portion of the dive during which the diver
was breathing oxygen is counted as oxygen time. The use of multiple UBAs is
generally restricted to special opera­tions. Decompression procedures for multipleUBA diving must be in accordance with approved procedures.
Example. A dive scenario calls for three swim pairs to be inserted near a harbor

using a SEAL Delivery Vehicle (SDV). The divers will be breathing compressed

16-12

U.S. Navy Diving Manual — Volume 4

air for a total of 3 hours prior to leaving the SDV. No decompression is required
as determined by the Combat Swimmer Multilevel Dive (CSMD) procedures. The
SDV will surface and the divers will purge their oxygen rigs on the surface, take
a compass bearing and begin the oxygen dive. The Transit with Excursion Limits
rules will be used. There would be no adjustment necessary for the oxygen time as
a result of the 3 hour compressed air dive.
16-3.6

Oxygen Diving at High Elevations. The oxygen exposure limits and procedures as

set forth in the preceding para­graphs may be used without adjustment for closedcircuit oxygen diving at altitudes above sea level.

16-3.7

Flying After Oxygen Diving. Flying is permitted immediately after oxygen diving

unless the oxygen dive has been part of a multiple-UBA dive profile in which the
diver was also breathing another breathing mixture (air, N2O2, or HeO2). In this
case, the rules found in the Chapter 9 apply.

16-3.8

Combat Operations. The oxygen exposure limits in this section are the only

limits approved for use by the U.S. Navy and should not be exceeded in a training
or exercise scenario. Should combat operations require a more severe oxygen
exposure, an estimate of the increased risk of CNS oxygen toxicity may be
obtained from a Diving Medical Officer or the Navy Experimental Diving Unit.
The advice of a Diving Medical Officer is essential in such situations and should
be obtained whenever possible.

16-4

OPERATIONS PLANNING

Certain factors must be taken into consideration in the planning of the oxygen dive
operation. The following gives detailed information on specific areas of planning.
16-4.1

Operating Limitations. Diving Officers and Diving Supervisors must consider the

following potential limiting factors when planning CC-UBA operations:
n CC-UBA oxygen supply (O&M Manuals)
n CC-UBA canister duration (O&M Manuals)
n Oxygen exposure limits
n Thermal factors

16-4.2

Maximizing Operational Range. The operational range of the CC-UBA may be
maximized by adhering to these guidelines:

n Whenever possible, plan the operation using the turtleback technique, in which
the diver swims on the surface part of the time, breathing air where feasible.
n Use tides and currents to maximum advantage. Avoid swimming against a cur­
rent when possible.

CHAPTER 16 — Closed-Circuit Oxygen CC-UBA Diving

16-13

n Ensure that oxygen bottles are charged to maximum capacity before the dive.
n Minimize gas loss from the CC-UBA by avoiding leaks and unnecessary depth
changes.
n Maintain a comfortable, relaxed swim pace during the operation. For most
divers, this is a swim speed of approximately 0.8 knot. At high exercise rates,
the faster swim speed is offset by a disproportionately higher oxygen con­
sumption, resulting in a net decrease in operating range. High exercise rates
may reduce the oxygen supply duration below the canister carbon dioxide
scrubbing duration and become the limiting factor for the operation.
n Ensure divers wear adequate thermal protection. A cold diver will begin
shiv­ering or increase his exercise rate, either of which will increase oxygen
consumption and decrease the operating duration of the oxygen supply.
WARNING

16-4.3

Most CC-UBAs do not have a carbon dioxide-monitoring capability.
Failure to adhere to canister duration operations planning could lead to
unconsciousness and/or death.
Training. Training and requalification dives shall be performed with the following

consider­ations in mind:

n Training dives shall be conducted with equipment that reflects what the diver
will be required to use on operations. This should include limpets, demoli­tions,
and weapons as deemed appropriate.
n Periodic classroom refresher training shall be conducted in oxygen diving pro­
cedures, CNS oxygen toxicity and management of diving accidents.
n Develop a simple set of hand signals, including the following signals:

—
—
—
—
—
—

Surface
Emergency Surface
Descend
Ascend
Speed Up
Slow Down

—
—
—
—
—
—

Okay
Feel Strange
Ear Squeeze
Stop
Caution
Excursion

n Match swim pairs according to swim speed.
n If long duration oxygen swims are to be performed, work-up dives of gradu­ally
increasing length are recommended.
16-4.4

Personnel Requirements. The following topside personnel must be present on all

training and exercise closed-circuit oxygen dives:

16-14

U.S. Navy Diving Manual — Volume 4

n Diving Supervisor/Boat Coxswain
n Standby diver/surface swimmer with air (not oxygen) SCUBA
n Diving Medical Technician or other individual specifically trained in diagnosis/
emergency treatment of diving injuries. Must have completed formal training
at a DOD recognized course of instruction (COI).
16-4.5

Equipment Requirements. Equipment requirements for training and exercise

CC-UBA dives are shown in Table 16-4. Several equipment items merit special
consideration as noted below:

n Motorized Chase Boat. A minimum of one motorized chase boat must be
present for the dive. Safe diving practice in many situations, however, would
require the presence of more than one chase boat (e.g., night operations). The
Diving Supervisor must determine the number of boats required based on the
diving area, medical evacuation plan and number of personnel participating in
the dive. When more than one safety craft is used, communications between
support craft should be available.
n Buddy Lines. Because the risk is greater that a diver will become unconscious
or disabled during a CC-UBA dive than during other types of dives, buddy lines
are required equipment for oxygen dives. In a few special diving scenarios,
when their use may hinder or endanger the divers, buddy lines may not be
feasible. The Diving Supervisor must carefully consider each situation and
allow buddy lines to be disconnected only when their use will impede the
performance of the mission.
n Depth Gauge. The importance of maintaining accurate depth control on oxygen
swims mandates that a depth gauge be worn by each diver.
n Witness Float. During CC-UBA training operations divers do not have to be
surface tended to swim under the hull of a vessel. However, they must be marked
by a witness float which must be visible on the surface at all times. After sunset,
the float must be illuminated to be readily visible to topside personnel e.g.
CHEMLITEs. The Diving Supervisor must consider the draft of the vessel and
the appropriate environmental factors, e.g. current and sea state, to determine
the required length of the witness float line.
n Special Diving Situations. Special diving situations by their nature require
deviations from the above configurations (ie, single untended diver, buoy-less
swimming). Mine Counter Measure (MCM) and Combat Diving operations
are unique and require specific tactics that should be maintained at the unit
level. Local instructions or directives for special diving situations shall be
documented in writing and approved by the first major command over the unit.
The major command shall review the tactics at a minimum of bi-annually, or
more frequently as during the unit’s combat certification, whichever is shorter,
and documented by cover letter.

CHAPTER 16 — Closed-Circuit Oxygen CC-UBA Diving

16-15

Table 16‑4. CC-UBA Diving Equipment.
A. General

D. Diving Medical Technician

1.

Motorized chase boat*

1.

2.

Radio (radio communications with parent unit,
chamber, medevac units, and support craft when
feasible)

Self-inflating bag-mask ventilator with medium adult
mask

2.

Oro-pharyngeal airway, adaptable to mask used

3.

First aid kit/portable O2

3.

High-intensity, wide-beam light (night operations)

4.

Two canteens of fresh water for treating chemical injury

4.

Dive flags and/or dive lights as required

B. Diving Supervisor

E. Divers
Required:

1.

Dive watch

1.

Approved life jacket

2.

Dive pair list

2.

Weight belt (Jettisonable)

3.

Recall devices

3.

Face mask

4.

Copy of Oxygen Exposure Limits

4.

Fins

5.

Copy of Air Tables

5.

Dive knife

6.

Flare or Strobe

C. Standby Diver
1.

Compressed-air SCUBA

7.

Dive watch

2.

Weight belt (if needed)

8.

Appropriate thermal protection

3.

Approved life jacket

9.

Whistle

4.

Face mask

10. Buddy line (one per pair)*

5.

Fins

6.

Appropriate thermal protection

11. Depth gauge (large face; accurate at shallow depths;
one per diver)*

7.

Dive knife

8.

Flare

9.

Tending line

12. Compass (one per pair if on compass course)
Optional:

10. Depth gauge
11. Dive watch

1.

Gloves

2.

Buoy (one per pair)

3.

Slate with writing device

* See paragraph 16‑4.5

16-4.6

Predive Precautions. The following items shall be determined prior to the diving

operation:

n Means of communicating with the nearest available Diving Medical Officer.
n Location of the nearest appropriate functional recompression chamber. Positive
confirma­tion of the chamber’s availability must be obtained prior to diving.
n Nearest medical facility for treatment of injuries or medical problems not
requiring recompression therapy.
n Optimal method of transportation to recompression chamber or medical
facil­ity. If coordination with other units for aircraft/boat/vehicle support is
necessary, the Diving Supervisor must know the frequencies, call signs and
contact personnel needed to make transportation available in case of emer­
gency. A medical evacuation plan must be included in the Diving Supervisor
brief.

16-16

U.S. Navy Diving Manual — Volume 4

n The preparation of a checklist similar to that found in Chapter 6 is recommended.
n When operations are to be conducted in the vicinity of ships, the guidelines
provided in the Ship Repair Safety Checklist (Chapter 6) and appropriate Naval
Special Warfare Group instructions shall be followed.
n Notification of intent to conduct diving operations must be sent to the appro­
priate authority in accordance with local directives.
16-5

PREDIVE PROCEDURES

This section provides the predive procedures for closed-circuit oxygen dives.
16-5.1

Equipment Preparation. The predive set up of the UBA is performed using the

appropriate check­
list from the appropriate UBA Operation and Maintenance
Manual.
16-5.2

Diving Supervisor Brief. The Diving Supervisor brief shall be given separately

from the overall mission brief and shall focus on the diving portion of the operation
with special attention to the items shown in Table 16-5.

16-5.3
16‑5.3.1

16‑5.3.2

Diving Supervisor Check
First Phase. The Diving Supervisor check is accomplished in two stages. As the
divers set up their rigs prior to the dive, the Diving Supervisor must ensure that
the steps in the set up procedure are accomplished properly in accordance with the
UBA Operation and Maintenance Manual. The Diving Supervisor signs the UBA
predive checklist, verifying that the procedures were completed correctly.
Second Phase. The second phase of the Diving Supervisor check is done after

the divers are dressed. At this point, the Diving Supervisor must check for the
following items:
n Adequate oxygen pressure
n Proper functioning of hose one-way valves
n UBA harness for proper donning and fit.
n Proper donning of UBA, life jacket and weight belt. The weight belt is worn so
it may be easily released.
n Presence of required items such as compasses, depth gauges, dive watches,
buddy lines, and tactical equipment.

CHAPTER 16 — Closed-Circuit Oxygen CC-UBA Diving

16-17

Table 16‑5. Diving Supervisor Brief.
A.

B.

C.

Dive Plan

F.

Operating depth

1.

Symptoms of O2 Toxicity - review in detail

2.

Distance, bearings, transit lines

2.

Symptoms of CO2 buildup - review in detail

3.

Dive time

3.

4.

Known obstacles or hazards

Review management of underwater convulsion,
nonconvulsive O2 hit, CO2 buildup, hypoxia,
chemical injury, unconscious diver

4.

UBA malfunction

5.

Lost swim-pair procedures

6.

Medical evacuation plan

Environmental
1.

Weather conditions

2.

Water/air temperatures

3.

Water/air visibility

4.

Current/Tides

n

Special Equipment for:
1.

Divers (include thermal garment)

2.

Diving supervisor

3.

Standby Diver

4.

Diving medical technician

D.

Review of Hand Signals

E.

Communications

16-6

Emergency Procedures

1.

1.

Frequencies

2.

Call signs

nearest appropriate chamber

n

nearest Dive Medical Officer (DMO)

n

transportation plan

n

recovery of other swim pairs

G.

Review of Purge Procedure

H.

Times for Operations

WATER ENTRY AND DESCENT

The diver is required to perform a purge procedure prior to or during any dive in
which closed-circuit oxygen UBA is to be used. The purge procedure is designed
to eliminate the nitrogen from the UBA and the diver’s lungs as soon as he begins
breathing from the rig. This procedure prevents the possibility of hypoxia as a
result of excessive nitrogen in the breathing loop. The gas volume from which
this excess nitrogen must be eliminated is comprised of more than just the UBA
breathing bag. The carbon dioxide-absorbent canister, inhalation/exhalation hoses,
and diver’s lungs must also be purged of nitrogen.
16-6.1

Purge Procedure. Immediately prior to entering the water, the divers shall

carry out the appropriate purge procedure. It is both difficult and unnecessary to
eliminate nitrogen completely from the breathing loop. The purge procedure need
only raise the frac­tion of oxygen in the breathing loop to a level high enough to
prevent the diver from becoming hypoxic.

If the dive is part of a tactical scenario that requires a turtleback phase, the purge
must be done in the water after the surface swim, prior to submerging. If the tactical
scenario requires an underwater purge procedure, this will be completed while
submerged after an initial subsurface transit on open-circuit SCUBA or other UBA.
When the purge is done in either manner, the diver must be thoroughly familiar
with the purge procedure and execute it carefully with attention to detail so that it
may be accomplished correctly in this less favorable environment.
16-6.2

16-18

Avoiding Purge Procedure Errors. The following errors may result in a
dangerously low percentage of oxygen in the UBA and should be avoided:

U.S. Navy Diving Manual — Volume 4

n Exhaling back into the bag with the last breath rather than to the atmosphere
while emptying the breathing bag.
n Underinflating the bag during the fill segment of the fill/empty cycle.
n Adjusting the UBA harnesses or adjustment straps of the life jacket too tightly.
Lack of room for bag expansion may result in underinflation of the bag and
inadequate purging.
n Breathing gas volume deficiency caused by failure to turn on the oxygen-sup­
ply valve prior to underwater purge procedures.
16-7

UNDERWATER PROCEDURES
16-7.1

General Guidelines. During the dive, the divers shall adhere to the following

guidelines:

n Know and observe the oxygen exposure limits.
n Observe the UBA canister limit for the expected water temperature, see
respective UBA O&M manuals.
n Wear the appropriate thermal protection.
n Use the proper weights for the thermal protection worn and for equipment
carried.
n Wear a depth gauge to allow precise depth control. The depth for the pair of
divers is the greatest depth attained by either diver.
n Dive partners check each other carefully for leaks at the onset of the dive. This
should be done in the water after purging, but before descending to transit
depth.
n Swim at a relaxed, comfortable pace as established by the slower swimmer of
the pair.
n Maintain frequent visual or touch checks with buddy.
n Be alert for any symptoms suggestive of a medical disorder (CNS oxygen tox­
icity, carbon dioxide buildup, etc.).
n Use tides and currents to maximum advantage.
n Swim at 20 fsw or shallower unless operational requirements dictate otherwise.
n Use the minimum surface checks consistent with operational necessity.

CHAPTER 16 — Closed-Circuit Oxygen CC-UBA Diving

16-19

n Minimize gas loss from the UBA.
n Do not use the UBA breathing bag as a buoyancy compensation device.
n Do not perform additional purges during the dive unless the mouthpiece is
removed and air is breathed.
n If an excursion is taken, the diver not using the compass will note carefully the
starting and ending time of the excursion.
16-7.2

16-8

UBA Malfunction Procedures. The diver shall be thoroughly familiar with the
malfunction procedures unique to his UBA. These procedures are described in the
UBA Operational and Maintenance Manual.

ASCENT PROCEDURES

The ascent rate shall never exceed 30 feet per minute.
16-9

POSTDIVE PROCEDURES AND DIVE DOCUMENTATION

UBA postdive procedures should be accomplished using the Postdive checklist
from the UBA Operation and Maintenance Manual.
All dives and mishap reporting shall be accomplished in accordance with guidance
in Chapter 5.

16-20

U.S. Navy Diving Manual — Volume 4

16-10

MK-25

The CC-UBA currently used by Combat Divers is the MK 25 MOD 2. Figure
16‑3 lists the operational characteristics of the MK 25 MOD 2. For more detailed
description, refer the the MK25 Operation and Maintenance Manual.

MK 25 MOD 2 Characteristics
Principle of Operation:

Advantages:

Combat Diving only, closed-circuit system

1. No Surface Bubbles
2. Minimum Support

Minimum Equipment:

3. Long Duration

1. MK 25 MOD 2 UBA

4. Fast deployment

2. Approved life jacket

5. Good Horizontal Mobility

3. Face mask
4. Weight (as required)

Disadvantages:

5. Dive knife

1. Limited to shallow depths

6. Swim fins

2. CNS Oxygen toxicity hazards

7. Dive watch

3. Limited physical and thermal protection

8. Appropriate thermal protection
9. Whistle
10. Buddy line (one per pair)
11. Depth gauge (large face; accurate at
shallow depths; one per diver)
12. Compass (one per pair if on compass
course)

Restrictions:
1. Normal working limit-25 fsw for 240
minutes
2. Maximum working limit-50 fsw for 10
minutes
3. No excursion allowed when using Single
Depth Diving Limits

Principal Applications:
1. Combat Diving

Operational Considerations:

2. Search

1. Minimum personnel-5

3. Inspection

2. Buddy diver required
3. Chase boat

Figure 16‑3. MK 25 MOD 2 Operational Characteristics.

CHAPTER 16 — Closed-Circuit Oxygen CC-UBA Diving

16-21

PAGE LEFT BLANK INTENTIONALLY

16-22

U.S. Navy Diving Manual — Volume 4

VOLUME 5

Diving Medicine
& Recompression
Chamber
Operations
17

Diagnosis and
Treatment of
Decompression
Sickness and Arterial
Gas Embolism

18

Recompression
Chamber Operation

Appendix 5A

Neurological Examination

Appendix 5B

First Aid

Appendix 5C

Hazardous Marine Creatures

U.S. NAVY DIVING MANUAL
Change A

PAGE LEFT BLANK INTENTIONALLY

Volume 5 - Table of Contents
Chap/Para
17

Page
DIAGNOSIS AND TREATMENT OF DECOMPRESSION SICKNESS AND
ARTERIAL GAS EMBOLISM

17-1 INTRODUCTION.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-1
17-1.1

Purpose. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-1

17-1.2

Scope .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-1

17-2 MANNING REQUIREMENTS.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-1
17-2.1

Recompression Chamber Team.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-1

17-2.2

Diving Officer. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-2

17-2.3

Master Diver.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-3

17-2.4

Chamber Supervisor.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-3

17-2.5

Diving Medical Officer.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-3
17‑2.5.1 Prescribing and Modifying Treatments.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-4

17-2.6

Inside Tender/DMT.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-4

17-2.7

Outside Tender.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-5

17-2.8

Emergency Consultation.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-5

17-3 ARTERIAL GAS EMBOLISM.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-6
17-3.1

Diagnosis of Arterial Gas Embolism.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-6
17‑3.1.1 Symptoms of AGE .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-7

17-3.2

Treating Arterial Gas Embolism .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-7

17-3.3

Resuscitation of a Pulseless Diver.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-7
17‑3.3.1 Evacuation not Feasible.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-8

17-4 DECOMPRESSION SICKNESS.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-8
17-4.1

Diagnosis of Decompression Sickness. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-9

17-4.2

Symptoms of Type I Decompression Sickness.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-9
17‑4.2.1 Musculoskeletal Pain-Only Symptoms.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-9
17‑4.2.2 Cutaneous (Skin) Symptoms.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-11
17‑4.2.3 Lymphatic Symptoms.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-11

17-4.3

Treatment of Type I Decompression Sickness.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-11

17-4.4

Symptoms of Type II Decompression Sickness .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-11
17‑4.4.1
17‑4.4.2
17‑4.4.3
17‑4.4.4

17-4.5

Neurological Symptoms.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-11
Inner Ear Symptoms (“Staggers”) .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-12
Cardiopulmonary Symptoms (“Chokes”) .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-12
Differentiating Between Type II DCS and AGE .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-12

Treatment of Type II Decompression Sickness. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-12

Table of Contents­—Volume 5

5–i

Chap/Para

Page
17-4.6

Decompression Sickness in the Water.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-13

17-4.7

Symptomatic Omitted Decompression.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-13

17-4.8

Altitude Decompression Sickness. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-13
17‑4.8.1 Joint Pain Treatment .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-13
17‑4.8.2 Other Symptoms and Persistent Symptoms .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-13

17-5 RECOMPRESSION TREATMENT FOR DIVING DISORDERS.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-14
17-5.1

Primary Objectives .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-14

17-5.2

Guidance on Recompression Treatment .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-14

17-5.3

Recompression Treatment When Chamber Is Available..  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-14
17‑5.3.1 Recompression Treatment with Oxygen .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-14
17-5.3.2 Recompression Treatments When Oxygen Is Not Available.  .  .  .  .  .  .  .  .  .  . 17-14

17-5.4

Recompression Treatment When No Recompression Chamber is Available .  .  .  .  .  .  . 17-15
17-5.4.1 Transporting the Patient.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-15
17-5.4.2 In-Water Recompression.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-16

17-6 TREATMENT TABLES.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-17
17-6.1

Air Treatment Tables.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-17

17-6.2

Treatment Table 5.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-17

17-6.3

Treatment Table 6. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-18

17-6.4

Treatment Table 6A..  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-18

17-6.5

Treatment Table 4. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-18

17-6.6

Treatment Table 7. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-19
17-6.6.1 Decompression .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-19
17-6.6.2 Tenders. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-20
17-6.6.3 Preventing Inadvertent Early Surfacing.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-20
17-6.6.4 Oxygen Breathing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-20
17-6.6.5 Sleeping, Resting, and Eating .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-20
17-6.6.6 Ancillary Care.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-20
17-6.6.7 Life Support .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-21

17-6.7

Treatment Table 8. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-21

17-6.8

Treatment Table 9. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-21

17-7 RECOMPRESSION TREATMENT FOR NON-DIVING DISORDERS .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-21
17-8 RECOMPRESSION CHAMBER LIFE-SUPPORT CONSIDERATIONS .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-22
17-8.1

Oxygen Control.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-23

17-8.2

Carbon Dioxide Control. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-23
17‑8.2.1 Carbon Dioxide Monitoring. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-23
17‑8.2.2 Carbon Dioxide Scrubbing.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-23
17‑8.2.3 Carbon Dioxide Absorbent.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-23

17-8.3

Temperature Control.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-23
17‑8.3.1 Patient Hydration.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-24

17-8.4

5–ii

Chamber Ventilation.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-25

U.S. Navy Diving Manual—Volume 5

Chap/Para

Page
17-8.5

Access to Chamber Occupants. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-25

17-8.6

Inside Tender Oxygen Breathing. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-25

17-8.7

Tending Frequency.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-25

17-8.8

Equalizing During Descent.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-25

17-8.9

Use of High Oxygen Mixes.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-25

17-8.10 Oxygen Toxicity During Treatment .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-26
17‑8.10.1 Central Nervous System Oxygen Toxicity .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-26
17‑8.10.2 Pulmonary Oxygen Toxicity .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-27
17-8.11 Loss of Oxygen During Treatment .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-27
17‑8.11.1 Compensation .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-28
17‑8.11.2 Switching to Air Treatment Table .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-28
17-8.12 Treatment of Altitude.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-28
17-9 POST-TREATMENT CONSIDERATIONS .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-28
17-9.1

Post-Treatment Observation Period.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-28

17-9.2

Post-Treatment Transfer.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-29

17-9.3

Flying After Treatments.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-29
17‑9.3.1 Emergency Air Evacuation.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-30

17-9.4

Treatment of Residual Symptoms. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-30

17-9.5

Returning to Diving after Recompression Treatment .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-30

17-10 NON-STANDARD TREATMENTS .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-31
17-11 RECOMPRESSION TREATMENT ABORT PROCEDURES.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-31
17-11.1 Death During Treatment.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-31
17-11.2 Impending Natural Disasters or Mechanical Failures.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-32
17-12 ANCILLARY CARE AND ADJUNCTIVE TREATMENTS. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-32
17-12.1 Decompression Sickness.. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-33
17‑12.1.1
17‑12.1.2
17‑12.1.3
17‑12.1.4
17‑12.1.5
17‑12.1.6
17‑12.1.7

Surface Oxygen.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Fluids.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Anticoagulants.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Aspirin and Other Non-Steroidal Anti-Inflammatory Drugs. .  .  .  .  .  .  .  .  .  .  .  .
Steroids .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Lidocaine .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Environmental Temperature.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .

17-33
17-33
17-34
17-34
17-34
17-34
17-34

17-12.2 Arterial Gas Embolism .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-34
17‑12.2.1
17‑12.2.2
17‑12.2.3
17‑12.2.4
17‑12.2.5
17‑12.2.6

Surface Oxygen.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Lidocaine .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Fluids.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Anticoagulants.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Aspirin and Other Non-Steroidal Anti-Inflammatory Drugs. .  .  .  .  .  .  .  .  .  .  .  .
Steroids .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .

17-34
17-34
17-35
17-35
17-35
17-35

17-12.3 Sleeping and Eating .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-35

Table of Contents­—Volume 5

5–iii

Chap/Para

Page

17-13 EMERGENCY MEDICAL EQUIPMENT.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-36
17-13.1 Primary and Secondary Emergency Kits .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-36
17-13.2 Portable Monitor-Defibrillator .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-36
17-13.3 Advanced Cardiac Life Support Drugs.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-40
17-13.4 Use of Emergency Kits.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-41
17-13.4.1 Modification of Emergency Kits .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-41

18

RECOMPRESSION CHAMBER OPERATION

18-1 INTRODUCTION.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 18-1
18-1.1

Purpose. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 18-1

18-1.2

Scope .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 18-1

18-1.3

Chamber Requirements .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 18-1

18-2 DESCRIPTION .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 18-2
18-2.1

Basic Chamber Components .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 18-2

18-2.2

Fleet Modernized Double-Lock Recompression Chamber.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 18-3

18-2.3

Recompression Chamber Facility (RCF) .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 18-3

18-2.4

Standard Navy Double Lock Recompression Chamber System (SNDLRCS) .  .  .  .  .  .  . 18-3

18-2.5

Transportable Recompression Chamber System (TRCS) .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 18-3

18-2.6

Fly Away Recompression Chamber (FARCC) .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 18-4

18-2.7

Emergency Evacuation Hyperbaric Stretcher (EEHS) .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 18-4

18-2.8

Standard Features .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 18-4
18‑2.8.1
18‑2.8.2
18‑2.8.3
18‑2.8.4
18‑2.8.5
18‑2.8.6

Labeling.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Inlet and Exhaust Ports .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Pressure Gauges.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Relief Valves. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Communications System.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Lighting Fixtures.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .

18-4
18-5
18-5
18-5
18-5
18-5

18-3 STATE OF READINESS.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 18-15
18-4 GAS SUPPLY.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 18-15
18-4.1

Capacity .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 18-15

18-5 OPERATION.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 18-17
18-5.1

Predive Checklist .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 18-17

18-5.2

Safety Precautions .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 18-17

18-5.3

General Operating Procedures.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 18-17
18‑5.3.1
18‑5.3.2
18‑5.3.3
18‑5.3.4

5–iv

Tender Change-Out.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Lock-In Operations.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Lock-Out Operations .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Gag Valves.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .

18-20
18-20
18-20
18-20

U.S. Navy Diving Manual—Volume 5

Chap/Para

Page
18-5.4

Ventilation.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 18-20
18‑5.4.1 Chamber Ventilation Bill.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 18-21
18‑5.4.2 Notes on Chamber Ventilation.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 18-22

18-6 CHAMBER MAINTENANCE. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 18-23
18-6.1

Postdive Checklist. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 18-23

18-6.2

Scheduled Maintenance.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 18-23
18‑6.2.1
18‑6.2.2
18‑6.2.3
18‑6.2.4
18‑6.2.5
18‑6.2.6

Inspections.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Corrosion.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Painting Steel Chambers.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Recompression Chamber Paint Process Instruction.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Stainless Steel Chambers .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Fire Hazard Prevention .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .

18-25
18-25
18-25
18-29
18-29
18-29

18-7 DIVER CANDIDATE PRESSURE TEST. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 18-30
18-7.1

Candidate Requirements .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 18-30
18‑7.1.1 Aviation Duty Personnel. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 18-30

18-7.2

Procedure. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 18-31
18‑7.2.1 References. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 18-31

5A

NEUROLOGICAL EXAMINATION

5A-1 INTRODUCTION.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5A-1
5A-2 INITIAL ASSESSMENT OF DIVING INJURIES.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5A-1
5A-3 NEUROLOGICAL ASSESSMENT.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5A-2
5A-3.1

Mental Status .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5A-5

5A-3.2

Coordination (Cerebellar/Inner Ear Function).  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5A-5

5A-3.3

Cranial Nerves .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5A-6

5A-3.4

Motor.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5A-7
5A‑3.4.1
5A‑3.4.2
5A‑3.4.3
5A‑3.4.4

5A-3.5

5A-8
5A-8
5A-8
5A-8

Sensory Function .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5A-8
5A‑3.5.1
5A‑3.5.2
5A‑3.5.3
5A‑3.5.4
5A‑3.5.5
5A‑3.5.6
5A‑3.5.7

5A-3.6

Extremity Strength.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Muscle Size .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Muscle Tone.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Involuntary Movements .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .

Sensory Examination.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5A-10
Sensations.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5A-10
Instruments. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5A-10
Testing the Trunk .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5A-10
Testing Limbs.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5A-10
Testing the Hands. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5A-10
Marking Abnormalities .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5A-10

Deep Tendon Reflexes.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5A-10

Table of Contents­—Volume 5

5–v

Chap/Para
5B

Page
FIRST AID

5B-1 INTRODUCTION.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5B-1
5B-2 CARDIOPULMONARY RESUSCITATION.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5B-1
5B-3 CONTROL OF MASSIVE BLEEDING .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5B-1
5B-3.1

External Arterial Hemorrhage.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5B-1

5B-3.2

Direct Pressure.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5B-1

5B-3.3

Pressure Points. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5B-1
5B‑3.3.1
5B‑3.3.2
5B‑3.3.3
5B‑3.3.4
5B‑3.3.5
5B‑3.3.6
5B‑3.3.7
5B‑3.3.8
5B‑3.3.9
5B‑3.3.10
5B‑3.3.11
5B‑3.3.12

5B-3.4

Pressure Point Location on Face.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Pressure Point Location for Shoulder or Upper Arm .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Pressure Point Location for Middle Arm and Hand .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Pressure Point Location for Thigh .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Pressure Point Location for Foot.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Pressure Point Location for Temple or Scalp.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Pressure Point Location for Neck. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Pressure Point Location for Lower Arm.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Pressure Point Location of the Upper Thigh .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Pressure Point Location Between Knee and Foot.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Determining Correct Pressure Point. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
When to Use Pressure Points .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .

5B-2
5B-2
5B-2
5B-2
5B-2
5B-2
5B-2
5B-2
5B-2
5B-4
5B-4
5B-4

Tourniquet.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5B-4
5B‑3.4.1
5B‑3.4.2
5B‑3.4.3
5B‑3.4.4

How to Make a Tourniquet.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Tightness of Tourniquet .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
After Bleeding is Under Control.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
Points to Remember..  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .

5B-4
5B-5
5B-5
5B-5

5B-3.5

External Venous Hemorrhage.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5B-6

5B-3.6

Internal Bleeding.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5B-6
5B‑3.6.1 Treatment of Internal Bleeding.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5B-6

5B-4 SHOCK.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5B-6

5C

5B-4.1

Signs and Symptoms of Shock.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5B-6

5B-4.2

Treatment . .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5B-7

HAZARDOUS MARINE CREATURES

5C-1 INTRODUCTION.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-1
5C-1.1 Purpose. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-1
5C-1.2 Scope .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-1
5C-2 MARINE ANIMALS THAT ATTACK.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-1
5C-2.1 Sharks.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-1
5C‑2.1.1 Shark Pre-Attack Behavior.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-1
5C‑2.1.2 First Aid and Treatment .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-1

5–vi

U.S. Navy Diving Manual—Volume 5

Chap/Para

Page
5C-2.2 Killer Whales.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-3
5C‑2.2.1 Prevention .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-4
5C‑2.2.2 First Aid and Treatment .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-4
5C-2.3 Barracuda.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-4
5C‑2.3.1 Prevention .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-4
5C‑2.3.2 First Aid and Treatment .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-4
5C-2.4 Moray Eels .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-4
5C‑2.4.1 Prevention .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-5
5C‑2.4.2 First Aid and Treatment .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-5
5C-2.5 Sea Lions .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-5
5C‑2.5.1 Prevention .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-5
5C‑2.5.2 First Aid and Treatment .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-5

5C-3 VENOMOUS MARINE ANIMALS.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-6
5C-3.1 Venomous Fish (Excluding Stonefish, Zebrafish, Scorpionfish).  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-6
5C‑3.1.1 Prevention .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-6
5C‑3.1.2 First Aid and Treatment .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-6
5C-3.2 Highly Toxic Fish (Stonefish, Zebrafish, Scorpionfish) .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-7
5C‑3.2.1 Prevention..  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-7
5C‑3.2.2 First Aid and Treatment..  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-7
5C-3.3 Stingrays.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-8
5C‑3.3.1 Prevention .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-9
5C‑3.3.2 First Aid and Treatment .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-9
5C-3.4 Coelenterates.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-9
5C‑3.4.1
5C‑3.4.2
5C‑3.4.3
5C‑3.4.4
5C‑3.4.5
5C‑3.4.6
5C‑3.4.7

Prevention .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-10
Avoidance of Tentacles .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-10
Protection Against Jellyfish. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5C-10
First Aid and Treatment .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-11
Symptomatic Treatment.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-11
Anaphylaxis .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-11
Antivenin. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-11

5C-3.5 Coral.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-11
5C‑3.5.1 Prevention .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-12
5C‑3.5.2 Protection Against Coral. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-12
5C‑3.5.3 First Aid and Treatment .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-12
5C-3.6 Octopuses.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-12
5C‑3.6.1 Prevention .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-13
5C‑3.6.2 First Aid and Treatment .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-13
5C-3.7 Segmented Worms (Annelida) (Examples: Bloodworm, Bristleworm) .  .  .  .  .  .  .  .  .  .  .  . 5C-13
5C‑3.7.1 Prevention .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-14
5C‑3.7.2 First Aid and Treatment .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-14
5C-3.8 Sea Urchins. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-14
5C‑3.8.1 Prevention..  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-14
5C‑3.8.2 First Aid and Treatment .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-14

Table of Contents­—Volume 5

5–vii

Chap/Para

Page
5C-3.9 Cone Snails. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-15
5C‑3.9.1 Prevention .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-15
5C‑3.9.2 First Aid and Treatment .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-15
5C-3.10 Sea Snakes. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-16
5C‑3.10.1 Sea Snake Bite Effects. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-16
5C‑3.10.2 Prevention .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-16
5C‑3.10.3 First Aid and Treatment .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-17
5C-3.11 Sponges .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-17
5C‑3.11.1 Prevention .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-17
5C‑3.11.2 First Aid and Treatment .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-18

5C-4 POISONOUS MARINE ANIMALS .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-18
5C-4.1 Ciguatera Fish Poisoning .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-18
5C‑4.1.1 Prevention .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-18
5C‑4.1.2 First Aid and Treatment .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-18
5C-4.2 Scombroid Fish Poisoning .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-19
5C‑4.2.1 Prevention .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-19
5C‑4.2.2 First Aid and Treatment .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-19
5C-4.3 Puffer (Fugu) Fish Poisoning .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-19
5C‑4.3.1 Prevention .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-19
5C‑4.3.2 First Aid and Treatment .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-19
5C-4.4 Paralytic Shellfish Poisoning (PSP) (Red Tide). . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5C-20
5C‑4.4.1 Symptoms .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-20
5C‑4.4.2 Prevention .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-20
5C‑4.4.3 First Aid and Treatment .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-20
5C-4.5 Bacterial and Viral Diseases from Shellfish .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-21
5C‑4.5.1 Prevention .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-21
5C‑4.5.2 First Aid and Treatment .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-21
5C-4.6 Sea Cucumbers .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-21
5C‑4.6.1 Prevention .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-21
5C‑4.6.2 First Aid and Treatment .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-21
5C-4.7 Parasitic Infestation. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-21
5C‑4.7.1 Prevention .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-21
5C-5 REFERENCES FOR ADDITIONAL INFORMATION .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-22

5–viii

U.S. Navy Diving Manual—Volume 5

Volume 5 - List of Illustrations
Figure

Page

17-1

Treatment of Arterial Gas Embolism or Serious Decompression Sickness. .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-39

17-2

Treatment of Type I Decompression Sickness .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-40

17-3

Treatment of Symptom Recurrence .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-42

17-4

Treatment Table 5.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-43

17-5

Treatment Table 6.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-44

17-6

Treatment Table 6A.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-45

17-7

Treatment Table 4.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-46

17-8

Treatment Table 7.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-47

17-9

Treatment Table 8.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-48

17-10

Treatment Table 9.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-49

17-11

Air Treatment Table 1A .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-50

17-12

Air Treatment Table 2A .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-51

17-13

Air Treatment Table 3 .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-52

18-1

Double-Lock Steel Recompression Chamber.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 18-6

18‑2

Recompression Chamber Facility: RCF 6500.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 18-7

18‑3

Recompression Chamber Facility: RCF 5000.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 18-8

18‑4

Double-Lock Steel Recompression Chamber.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 18-9

18-5

Fleet Modernized Double-Lock Recompression Chamber.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 18-10

18-6

Standard Navy Double-Lock Recompression Chamber System. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 18-11

18-7

Transportable Recompression Chamber System (TRCS).  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 18-12

18‑8

Transportable Recompression Chamber (TRC).  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 18-12

18-9

Transfer Lock (TL).  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 18-13

18-10

Fly Away Recompression Chamber (FARCC). .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 18-13

18-11

Fly Away Recompression Chamber .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 18-14

18-12

Fly Away Recompression Chamber Life Support Skid .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 18-14

18-13

Recompression Chamber Predive Checklist.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 18-18

18-14

Recompression Chamber Postdive Checklist.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 18-24

18-15

Pressure Test for USN Recompression Chambers.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 18-26

5A-1a

Neurological Examination Checklist .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5A-3

5A-2a

Dermatomal Areas Correlated to Spinal Cord Segment.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5A-11

5B‑1

Pressure Points.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5B-3

5B‑2

Applying a Tourniquet .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5B-5

5C-1

Types of Sharks. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-2

List of Illustrations—Volume 5

5–ix

Figure

5–x

Page

5C-2

Killer Whale.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-3

5C-3

Barracuda .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-4

5C-4

Moray Eel .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-5

5C-5

Weeverfish. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-6

5C-6

Highly Toxic Fish.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-8

5C-7

Stingray.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-9

5C-8

Coelenterates .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-10

5C-9

Octopus.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-12

5C-10

Cone Shell.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-15

5C-11

Sea Snake.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-16

U.S. Navy Diving Manual—Volume 5

Volume 5 - List of Tables
Table

Page

17‑1

Minimum Manning Levels for Recompression Treatments.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-2

17-2

Rules for Recompression Treatment.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-10

17‑3

Decompression.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-20

17‑4

Guidelines for Conducting Hyperbaric Oxygen Therapy.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-22

17‑5

Maximum Permissible Recompression Chamber Exposure Times at Various Temperatures..  17-24

17‑6

High Oxygen Treatment Gas Mixtures .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-26

17‑7

Tender Oxygen Breathing Requirements. (Note 1).  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-29

17‑8

Primary Emergency Kit.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-37

17‑9

Secondary Emergency Kit.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-38

18‑1

Navy Recompression Chamber Support Levels.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 18-1

18‑2

Recompression Chamber Line Guide.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 18-5

18‑3

Recompression Chamber Air Supply Requirements.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 18-16

5A‑1

Extremity Strength Tests.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5A-9

5A‑2

Reflexes. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5A-13

List of Tables—Volume 5

5–xi

Chap/Para

Page

PAGE LEFT BLANK INTENTIONALLY

5–xii

U.S. Navy Diving Manual—Volume 5

CHAPTER 17

Diagnosis and Treatment of
Decompression Sickness and
Arterial Gas Embolism
17-1

INTRODUCTION
17-1.1

Purpose. This chapter describes the diagnosis and treatment of diving disorders

with recom­pression therapy and/or hyperbaric oxygen therapy. Recompression
therapy is indicated for treating DCS, AGE, and several other disorders unless
the diver is critically ill or has experienced a drowning episode. In those cases
where diagnosis or treatment are not clear, direct the patient to the highest level
of medical care available and contact the Diving Medical Officers at NEDU or
NDSTC for guidance. The recompression procedures described in this chapter are
designed to handle most situations that will be encountered opera­tionally. They
are applicable to both surface-supplied and open and closed circuit SCUBA diving
as well as recompression chamber operations, whether breathing air, nitrogenoxygen, helium-oxygen, or 100 percent oxygen. Treatment of decompression
sickness during satu­ration dives is covered separately in Chapter 13 of this manual.
Periodic evaluation of U.S. Navy recompression treatment procedures has shown
they are effective in relieving symptoms over 90 percent of the time when used as
published.
17-1.2

Scope. The procedures outlined in this chapter are to be performed only by trained

personnel. Because these procedures are used to treat disorders ranging from mild
pain to life-threatening disorders, the degree of medical expertise necessary to carry
out proper treatment will vary. Certain procedures, such as starting intravenous
(IV) fluid lines and inserting chest tubes, require special training and must not
be attempted by untrained individuals. Treatment tables can be initiated without
consulting a Dive Medical Officer (DMO), however a DMO should always be
contacted at the earliest possible opportunity. A DMO must be contacted prior to
releasing the treated individual.
17-2

MANNING REQUIREMENTS
17-2.1

Recompression Chamber Team. A recompression chamber team is assembled in

two situations; where a recompression chamber is part of a diving operation, and
where a recompression chamber is maintained as an area response requirement.
This section applies to both situations. The designation “Chamber Supervisor”
may be interchanged with “Diving Supervisor” where a recompression chamber
is part of an operation. During a complex recompression treatment, the minimum
manning and emergency manning levels specified in Table 17-1 may not be
adequate to keep up with the surge of activity required at various points during

CHAPTER 17 — Diagnosis and Treatment of Decompression Sickness and Arterial Gas Embolism

17-1

the treatment and additional personnel should be obtained as soon as possible.
A second team may be required to relieve the initial team during prolonged
treatments.
Table 17-1. Minimum Manning Levels for Recompression Treatments.
Minimum Manning Levels for Recompression Treatments
Minimum

Diving Officer
Master Diver
Chamber Supervisor
Diving Medical Officer
Inside Tender/DMT
Log Keeper
Outside Tender
Total

Ideal

Emergency

1
1
1(a)

1

1(a)

1 (b)
1(b,c,d)

1(c,d)

1(b,c,d)

1
1

1

3

7

2

Notes:
(a) The Chamber Supervisor and outside tender must perform the essential tasks of
all other positions while keeping patient care a priority. The Chamber Supervisor
must attempt to obtain additional personnel as soon as possible.
(b) If the patient has symptoms of serious DCS or AGE where Basic Life Support
(BLS) or advanced medical support may be required (e.g., airway management,
or thoracic needle decompression), a Diving Medical Technician (DMT) or DMO
should accompany the patient inside the chamber in addition to the inside tender.
However, recompression treatment must not be delayed while awaiting the arrival
of a DMO or DMT.
(c) The best qualified person available should provide specialized medical care to a
patient in the chamber. The best qualified person may be a non-diving surgeon,
respiratory therapist, Independent Duty Corpsman (IDC), etc. Since these are
emergency exposures, no special medical or physical prerequisites exist. A
qualified Inside Tender is required inside the chamber at all times.
(d) Locking in /out personnel. Inside tenders and additional personnel may be locked
in and out during the course of a treatment. Chamber periods should be kept
within no-decompression limits if possible. However, decompression may be
accomplished in the outerlock utilizing the air decompression schedules in Table
9-9. Once an inside tender exceeds exceptional exposure limits of the applicable
schedule they are committed to the entire treatment table.

17-2.2

17-2

Diving Officer. The Diving Officer is responsible to the Commanding Officer
for the safe conduct of recompression chamber operations and for presenting

U.S. Navy Diving Manual — Volume 5

recommended changes to treatment protocols to the Commanding Officer. The
Diving Officer is responsible for complying with reporting requirements as listed
in Chapter 5 and additional duties as defined in the command dive bill.
17-2.3

Master Diver. The Master Diver is the most qualified person to supervise

recompression treatments. The Master Diver is trained in diagnosing and treating
diving injuries and illnesses and is responsible to the Commanding Officer, via the
Diving Officer, for the safe conduct of all phases of chamber operations.

The Master Diver provides direct oversight of the Chamber Supervisor and
technical expertise. If circumstances warrant, the Master Diver shall relieve the
Chamber Supervisor and assume control of the treatment.
17-2.4

Chamber Supervisor. The Chamber Supervisor is responsible for execution of

treatment protocols, emergency procedures, and supervision of the chamber team.
If the Chamber Supervisor determines the reason for postdive symptoms is firmly
established to be due to causes other than decompression sickness or arterial gas
embolism (e.g. injury, sprain, poorly fitting equipment), then recompression is not
necessary. If the Chamber Supervisor cannot rule out the need for recompression
then the Chamber Supervisor must commence treatment. Additionally, the
Chamber Supervisor is responsible for:
n Communicating with personnel inside the chamber.
n Adhering to the minimum manning levels for conducting recompression
treatment (Table 17-1).
n Ensuring every member of the chamber team is thoroughly familiar with
all recompression procedures.
n Ensuring a Diving Medical Officer is contacted at the earliest opportunity
during treatment and before release of any patient from the treatment
facility.
n Ensuring details related to the assessment and treatment of the patient (e.g.
condition prior to treatment, time and depth of complete relief, patient vital
signs) are thoroughly documented in the recompression chamber log IAW
section 5-5 and the command dive bill.
n Tracking bottom time and the decompression profiles of personnel locking
in and out of the chamber.
n Ensuring the decompression profiles of persons locking in and out of the
chamber are logged in the chamber log.
17-2.5

Diving Medical Officer. The Diving Medical Officer recommends the proper course

of treatment, consults with other medical personnel, and prescribes medications
and treatment adjuncts. The Diving Medical Officer is the only team member who

CHAPTER 17 — Diagnosis and Treatment of Decompression Sickness and Arterial Gas Embolism

17-3

can modify recompression treatment tables, with concurrence of the Commanding
Officer or Officer-in-Charge.
The DMO typically locks in and out of the chamber as the patient’s condition
dictates (e.g., to administer advanced procedures, perform differential diagnosis, or
to verify complete relief of symptoms), and does not commit to the entire treatment
unless absolutely necessary. Once committed to remain in the chamber, the DMO’s
effectiveness in directing the treatment is greatly diminished and consultation with
other medical personnel becomes more difficult.
Recompression treatment for diving related disorders may be initiated without
consulting a DMO, however, a DMO shall be consulted as early as possible, and
should be consulted before committing a patient to a Treatment Table 4 or 7. The
DMO may be on scene or in communication with the Chamber Supervisor.
17-2.5.1

Prescribing and Modifying Treatments. Because all possible outcomes cannot be
anticipated, additional medical expertise should be sought immediately in all cases
of decompression sickness or arterial gas embolism that do not show substantial
improvement on standard treatment tables. Deviation from these protocols shall be
made only with the recommendation of a Diving Medical Officer (DMO).

Not all Medical Officers are DMOs. The DMO shall be a graduate of the Diving
Medical Officer course taught at the Naval Diving and Salvage Training Center
(NDSTC) and have a subspecialty code of 16U0 (Basic Undersea Medical Officer)
or 16U1 (Residency in Undersea Medicine trained Undersea Medical Officer).
Medical Officers who complete only the nine-week diving medicine course at
NDSTC do not receive DMO subspecialty codes, but are considered to have the
same privileges as DMOs, with the exception that they are not granted the privilege
of modifying treatment protocols. Only DMOs with subspecialty codes 16U0 or
16U1 may modify the treatment protocols as warranted by the patient’s condition
with the concurrence of the Commanding Officer or Officer in Charge. Other
physicians may assist and advise treatment and care of diving casualties but may
not modify recompression procedures.
17-2.6

Inside Tender/DMT. When conducting a recompression treatment, at least one

qualified tender shall be inside the chamber at all times. The inside tender should
be a Diving Medical Technician (DMT) if available, however, any qualified diver
or non-diving medical personnel may qualify and perform as an inside tender as
stated below.
Diving Medical Technicians receive special training in hyperbaric medicine and
medical care and operate under the medical license and supervision of a DMO.
DMTs are trained to administer medical treatment adjuncts, handle emergencies
that may arise during treatment, and instruct members of the diving team in first
aid procedures.
Non-diving medical personnel (e.g., U.S. Naval Reserve Corpsmen, and nursing
personnel) may qualify as an Inside Tender via the Military Diver Inside Tender
PQS (NAVEDTRA 43910). Non-diving medical personnel must obtain a current

17-4

U.S. Navy Diving Manual — Volume 5

diving physical exam, conform to Navy physical standards, and pass the diver
candidate pressure test.
The inside tender shall be familiar with all treatment procedures and the signs,
symptoms, and treatment of all diving-related disorders.
During the early phases of treatment, the inside tender must monitor the patient
periodically for signs of relief of symptoms. Observation of the patient, to include
performance of repeat neurological exams, is the principal method of diagnosing
the patient’s illness and the depth and time of their relief helps determine which
treatment table is used.
The inside tender is also responsible for:
n Releasing the door latches (dogs) after a seal is made.
n Communicating with outside personnel.
n Providing first aid as required by the patient.
n Monitoring the patients vital signs.
n Administering treatment gas to the patient at treatment depth.
n Monitoring the patient for signs of oxygen toxicity. (CNS and Pulmonary)
n Ensuring that sound attenuators for ear protection are worn during
compression and ventilation portions of recompression treatments.
n Ensuring that the patient is lying down and positioned to permit free blood
circulation to all extremities.
17-2.7

Outside Tender. The outside tender is responsible for preparing the chamber

system for use and securing from use IAW the system operating procedures
and the chamber pre and post dive checklists. The chamber operator pressurizes
and ventilates the chamber at the required rates as specified by the Chamber
Supervisor. The outside tender operates the chamber medical lock, maintains
the chamber at the required depth, and monitors chamber internal environmental
readings, treatment gas bank, and air supply manifold pressures.

17-2.8

Emergency Consultation. Modern communications allow access to medical

expertise from even the most remote areas. Emergency consultation is available 24
hours a day with:

CHAPTER 17 — Diagnosis and Treatment of Decompression Sickness and Arterial Gas Embolism

17-5

Primary:
Navy Experimental Diving Unit (NEDU)

Commercial (850) 230-3100, DSN 436-4351
Secondary:
Navy Diving Salvage and Training Center (NDSTC)

Commercial (850) 234-4651, DSN 436-4651
17-3

ARTERIAL GAS EMBOLISM

Arterial gas embolism is caused by entry of gas bubbles into the arterial circula­
tion as a result of pulmonary over inflation syndrome (POIS). Gas embolism
can manifest during any dive where compressed gas is breathed under pressure,
even during a brief, shallow dive, or one made in a swimming pool. The onset of
symptoms is usually sudden and dramatic, often occurring within minutes after
arrival on the surface or even before reaching the surface. For this reason, all persons
surfacing from a dive where a compressed gas was breathed, shall remain under the
direct observation of the Dive Supervisor for 10 minutes after surfacing. Because
the supply of blood to the central nervous system is almost always compromised,
arterial gas embolism may result in death or permanent neurological damage unless
treated appropriately.
17-3.1

Diagnosis of Arterial Gas Embolism. As a basic rule, any diver who has
obtained a breath of compressed gas from any source at any depth, whether from
diving apparatus or from a diving bell, and who surfaces unconscious, loses
consciousness, or has any obvious neurological symptoms within 10 minutes of
reaching the surface, must be assumed to be suffering from arterial gas embolism.
Recompression treatment shall be started immediately after airway, breathing, and
circulation (ABCs) have been assessed. If the diver is pulseless and not breathing
establishment of ABCs is a HIGHER PRIORITY THAN RECOMPRESSION.
A diver who surfaces unconscious and recovers when exposed to fresh air shall
receive a neurological evaluation to rule out arterial gas embolism. Victims of
near-drowning incidents who have no neurological symptoms should ALWAYS be
carefully evalu­ated by a DMO, if available, for pulmonary aspiration, or referred
to a higher level of medical care.

The symptoms of AGE may be masked by environmental factors or by other less
significant symptoms. A chilled diver may not be concerned with numbness in an
arm, which may actually be the sign of CNS involvement. Pain from any source
may divert attention from other symptoms. The natural anxiety that accompanies
an emergency situation, such as the failure of the diver’s air supply, might mask a
state of confusion caused by an arterial gas embolism to the brain.
If pain is the only symptom, arterial gas embolism is unlikely and decompression
sickness or one of the other pulmonary overinflation syndromes, or trauma, should
be considered.

17-6

U.S. Navy Diving Manual — Volume 5

17‑3.1.1

Symptoms of AGE. The signs and symptoms of AGE may include near immediate

onset of altered consciousness, dizziness, paralysis or weakness in the extremities,
large areas of abnormal sensation (paresthesias), vision abnormal­ities, convulsions
or personality changes. During ascent, the diver may have noticed a sensation
similar to that of a blow to the chest. The victim may become unconscious without
warning and may stop breathing. Additional symptoms of AGE include:
n Extreme fatigue
n Difficulty in thinking
n Vertigo
n Nausea and/or vomiting
n Hearing abnormalities
n Bloody sputum
n Loss of control of bodily functions
n Tremors
n Loss of coordination
n Numbness
Symptoms of subcutaneous / mediastinal emphysema, pneumothorax and/or pneu­
mopericardium may also be present (see paragraph 3‑8). In all cases of arterial
gas embolism, the possible presence of these associated conditions should not be
overlooked.

17-3.2

Treating Arterial Gas Embolism. Arterial gas embolism is treated in accordance

with Figure 17-1 with initial compression to 60 fsw. If symptoms are improved
within the first oxygen breathing period, then treatment is continued using
Treatment Table 6. If symp­toms are unchanged or worsen, assess the patient upon
descent and compress to depth of relief (or significant improvement), not to exceed
165 fsw and follow Figure 17-1.
17-3.3

Resuscitation of a Pulseless Diver. The following are intended as guidelines. On

scene personnel must make management decisions considering all known factors.
Immediate CPR and application of an Automated External Defibrillator (AED) is
indicated for a diver with no pulse or respirations (cardiopulmonary arrest). Access
to advanced cardiac life support (ACLS) is a higher priority than recompression.
ACLS, which requires special medical training and equipment, is not always
available. Although not a substitute for the full range of interventions of ACLS,
use of an Automated External Defibrillator (AED) can deliver life-saving shocks
when a shockable heart rhythm is detected. CPR, patient monitoring, and drug
administration may be performed at depth, but electrical therapy (defibrillation or
cardioversion) must be performed on the surface.

CHAPTER 17 — Diagnosis and Treatment of Decompression Sickness and Arterial Gas Embolism

17-7

CPR must begin immediately and an AED should be placed on the victim as soon
as possible. All efforts should be made to immediately transport the patient to
the highest level of medical care available while continuing basic life support
measures (BLS) measures. If the pulseless diver regains vital signs continue, or
begin, transport to the nearest critical care facility prior to recompression.
Effective rescue breathing, excellent chest compressions, and immediate evacuation
to a medical facility is the most viable treatment for drowning victims. Delays
in access to a critical care facility will most likely will result in an unfavorable
outcome for the victim.
A pulseless diver should not be recompressed unless there is no possibility of
evacuation. Unless ABCs are restored the diver will likely die, even if adequate
CPR is performed, with or without recompression.
CAUTION

Defibrillation is not currently authorized at depth.

CAUTION

If the tender is outside of no-decompression limits, take appropriate
steps to manage the tender’s decompression obligation.

17-3.3.1

CAUTION:		

17-4

Evacuation not feasible. If an AED is not available and evacuation is not an

option, recompress the patient to 60 feet, continue BLS measures, and contact a
UMO. If an AED becomes available, surface the chamber at 30fpm and apply
the AED. If the diver regains pulse, continue with recompression and monitor the
patient closely.

If tenders are outside of no-decompression limits, take appropriate steps
to manage the tender’s decompression obligation. If the pulseless diver
does not regain a pulse with application of an AED, continue resuscitation
efforts until the diver recovers, the rescuers are unable to continue CPR,
or a physician pronounces the patient dead. Avoid recompressing a
pulseless diver who has failed to regain vital signs after use of an AED.

DECOMPRESSION SICKNESS

While a history of diving (or altitude exposure) is necessary for the diagnosis of
decompression sickness to be made, the depth and duration of the dive are useful
only in establishing if required decompression was missed. Decompression
sick­ness can occur in divers well within no-decompression limits or in divers who
have carefully followed decompression tables. Any decompression sickness that
occurs must be treated by recompression.
For purposes of deciding the appropriate treatment, symptoms of decompression
sickness are generally divided into two categories, Type I and Type II. Because
the treatment of Type I and Type II symptoms may be different, it is important to
distinguish between these two types of decompression sickness. The diver may

17-8

U.S. Navy Diving Manual — Volume 5

exhibit certain signs that only trained observers will identify as decompression
sickness. Some of the symptoms or signs will be so pronounced that there will be
little doubt as to the cause. Others may be subtle and some of the more important
signs could be overlooked in a cursory examination. Type I and Type II symptoms
may or may not be present at the same time.
17-4.1

Diagnosis of Decompression Sickness. Decompression sickness symptoms us-

ually occur shortly following the dive or other pressure exposure. If the controlled
decompression during ascent has been shortened or omitted, the diver could be
suffering from decompression sickness before reaching the surface. In analyzing
several thousand air dives in a database set up by the U.S. Navy for developing
decompression models, the time of onset of symptoms after surfacing was as
follows:
n 42 percent occurred within 1 hour.
n 60 percent occurred within 3 hours.
n 83 percent occurred within 8 hours.
n 98 percent occurred within 24 hours.
Appendix 5A contains a set of guidelines for performing a neurological examina­
tion and an examination checklist to assist trained personnel in evaluating
decompression sickness cases.
17-4.2

Symptoms of Type I Decompression Sickness. Type I decompression sickness

includes joint pain (musculoskeletal or pain-only symptoms) and symptoms
involving the skin (cutaneous symptoms), or swelling and pain in lymph nodes.

17‑4.2.1

Musculoskeletal Pain-Only Symptoms. The most common symptom of

decompression sickness is joint pain. Other types of pain may occur which do not
involve joints. The pain may be mild or excruci­ating. The most common sites of
joint pain are the shoulder, elbow, wrist, hand, knee, and ankle. The characteristic
pain of Type I decompression sickness usually begins gradually, is slight when first
noticed and may be difficult to localize. It may be located in a joint or muscle, may
increase in intensity, and is usually described as a deep, dull ache. The pain may or
may not be increased by movement of the affected joint, and the limb may be held
preferentially in certain positions to reduce the intensity (so-called guarding). The
hallmark of Type I pain is its dull, aching quality and confinement to particular
areas. It is always present at rest and is usually unaffected by movement.
Any pain occurring in the abdominal and thoracic areas, including the hips, should
be considered as symptoms arising from spinal cord involvement and treated as
Type II decompression sickness. The following symptoms may indicate spinal cord
involvement:
n Pain localized to joints between the ribs and spinal column or joints between
the ribs and sternum.

CHAPTER 17 — Diagnosis and Treatment of Decompression Sickness and Arterial Gas Embolism

17-9

Table 17‑2. Rules for Recompression Treatment.
ALWAYS:
1. Follow the treatment tables accurately, unless modified by a Diving Medical
Officer with concurrence of the Commanding Officer or Officer-in-Charge
(OIC).
2. Have a qualified tender in the chamber at all times during treatment.
3. Maintain the normal descent and ascent rates as much as possible.
4. Examine the patient thoroughly at depth of relief or treatment depth.
5. Treat an unconscious patient for arterial gas embolism or serious
decompression sickness unless the possibility of such a condition can be
ruled out without question.
6. Use air treatment tables only if oxygen is unavailable.
7. Be alert for warning signs of oxygen toxicity if oxygen is used.
8. In the event of an oxygen convulsion, remove the oxygen mask and keep
the patient from self-harm. Do not force the mouth open during a convulsion.
9. Maintain oxygen usage within the time and depth limitations prescribed by
the ­treatment table.
10. Check the patient’s condition and vital signs periodically. Check frequently
if the patient’s condition is changing rapidly or the vital signs are unstable.
11. Observe patient after treatment for recurrence of symptoms. Observe
2 hours for pain-only symptoms, 6 hours for serious symptoms. Do not
release patient without consulting a DMO.
12. Maintain accurate timekeeping and recording.
13. Maintain a well-stocked Primary and Secondary Emergency Kit.
NEVER:
1. Permit any shortening or other alteration of the tables, except under the
direction of a Diving Medical Officer.
2. Wait for a bag resuscitator. Use mouth-to-mouth resuscitation with a barrier
device immediately if breathing ceases.
3. Interrupt chest compressions for longer than 10 seconds.
4. Permit the use of 100 percent oxygen below 60 feet in cases of DCS
or AGE.
5. Fail to treat doubtful cases.
6. Allow personnel in the chamber to assume a cramped position that might
interfere with complete blood circulation.

n A shooting-type pain that radiates from the back around the body (radic­ular
or girdle pain).
n A vague, aching pain in the chest or abdomen (visceral pain).
17‑4.2.1.1

17-10

Differentiating Between Type I Pain and Injury. The most difficult differentiation
is between the pain of Type I decompression sickness and the pain resulting from
trauma or other injury such as a muscle strain or bruise. If there is any doubt as
to the cause of the pain, assume the diver is suffering from decompression sick­
ness and treat accordingly. Frequently, pain may mask other more significant

U.S. Navy Diving Manual — Volume 5

symptoms. Pain should not be treated with drugs in an effort to make the patient
more comfortable. The pain may be the only way to localize the problem and
monitor the progress of treatment.
17‑4.2.2

17‑4.2.3

17-4.3

Cutaneous (Skin) Symptoms. The most common skin manifestation of

decompression sickness is itching. Itching by itself is generally transient and does
not require recompression. Faint skin rashes may be present in conjunction with
itching. These rashes also are tran­sient and do not require recompression. Mottling
or marbling of the skin, known as cutis marmorata (marbling), may precede a
symptom of serious decompression sickness and shall be treated by recompression
as Type II decompression sickness. This condition starts as intense itching,
progresses to redness, and then gives way to a patchy, dark-bluish discoloration of
the skin. The skin may feel thickened. In some cases the rash may be raised.
Lymphatic Symptoms. Lymphatic obstruction may occur, creating localized

pain in involved lymph nodes and swelling of the tissues drained by these nodes.
Recompression may provide prompt relief from pain. The swelling, however, may
take longer to resolve completely and may still be present at the completion of
treatment.

Treatment of Type I Decompression Sickness. Type I Decompression Sickness

is treated in accordance with Figure 17-2. If a full neurological exam is not
completed before initial recompression, treat as Type II DCS.

Symptoms of musculoskeletal pain that have shown absolutely no change after the
second oxygen breathing period at 60 feet may be due to orthopedic injury rather
than decompression sickness. If, after reviewing the patient’s history, the Diving
Medical Officer feels that the pain can be related to specific orthopedic trauma or
injury, a Treatment Table 5 may be completed. If a Diving Medical Officer is not
consulted, Treatment Table 6 shall be used.
17-4.4

Symptoms of Type II Decompression Sickness. In the early stages, symptoms of

Type II decompression sickness may not be obvious and the stricken diver may
consider them inconsequential. The diver may feel fatigued or weak and attribute
the condition to overexertion. Even as weak­ness becomes more severe the diver
may not seek treatment until walking, hearing, or urinating becomes difficult.
Initial denial of DCS is common. For this reason, symptoms must be recognized
during the post-dive period and treated before they become too severe. Type II,
or serious, symptoms are divided into three categories: neurological, inner ear
(staggers), and cardiopulmonary (chokes). Type I symptoms may or may not be
present at the same time.
17‑4.4.1

Neurological Symptoms. These symptoms may be the result of involvement of

any level of the nervous system. Numbness, paresthesias (a tingling, pricking,
creeping, “pins and needles,” or “electric” sensation on the skin), decreased
sensation to touch, muscle weakness, paralysis, mental status changes, or motor
performance alterations are the most common symptoms. Disturbances of higher
brain function may result in personality changes, amnesia, bizarre behavior,
lightheadedness, lack of coordina­tion, and tremors. Lower spinal cord involvement

CHAPTER 17 — Diagnosis and Treatment of Decompression Sickness and Arterial Gas Embolism

17-11

can cause disruption of urinary function. Some of these signs may be subtle and
can be overlooked or dismissed by the stricken diver as being of no consequence.
The occurrence of any neurological symptom after a dive is abnormal and should
be considered a symptom of Type II decompression sickness or arterial gas embo­
lism, unless another specific cause can be found. Normal fatigue is not uncommon
after long dives and, by itself, is not usually treated as decompression sickness. If
the fatigue is unusually severe, a complete neurological examination is indicated to
ensure there is no other neurological involvement.
17‑4.4.2

Inner Ear Symptoms (“Staggers”). The symptoms of inner ear decompression

17‑4.4.3

Cardiopulmonary Symptoms (“Chokes”). If profuse intravascular bubbling

17‑4.4.4

Differentiating Between Type II DCS and AGE. Many of the symptoms of Type II
decompression sickness are the same as those of arterial gas embolism, although
the time course is generally different. (AGE usually occurs within 10 minutes
of surfacing.) Since the initial treatment of these two conditions is the same and
since subsequent treatment conditions are based on the response of the patient
to treatment, treatment should not be delayed unneces­sarily in order to make the
diagnosis.

17-4.5

17-12

sickness include: tinnitus (ringing in the ears), hearing loss, vertigo, dizziness,
nausea, and vomiting. Inner ear decom­pression sickness has occurred most often
in helium-oxygen diving and during decompression when the diver switched
from breathing helium-oxygen to air. Inner ear decompression sickness should be
differentiated from inner ear barotrauma, since the treatments are different. The
“Staggers” has been used as another name for inner ear decompression sickness
because of the afflicted diver’s difficulty in walking due to vestibular system
dysfunction. However, symptoms of imbalance may also be due to neurological
decompression sickness involving the cerebellum. Typically, rapid involuntary eye
movement (nystagmus) is not present in cerebellar decompression sickness.
occurs, symptoms of chokes may develop due to congestion of the lung circulation.
Chokes may start as chest pain aggravated by inspiration and/or as an irritating
cough. Increased breathing rate is usually observed. Symptoms of increasing lung
congestion may progress to complete circulatory collapse, loss of consciousness,
and death if recompression is not insti­tuted immediately. Careful examination for
signs of pneumothorax should be performed on patients presenting with shortness
of breath. Recompression is not indicated for pneumothorax if no other signs of
DCS or AGE are present.

Treatment of Type II Decompression Sickness. Type II Decompression Sickness
is treated with initial compression to 60 fsw in accordance with Figure 17-1. If
symptoms are improved within the first oxygen breathing period, then treatment
is continued on a Treatment Table 6. If severe symptoms (e.g. paralysis, major
weakness, memory loss, altered consciousness) are unchanged or worsen within
the first 20 minutes at 60 fsw, assess the patient during descent and compress to
depth of relief (or significant improvement), not to exceed to 165 fsw. Treat on
Treatment Table 6A. To limit recurrence, severe Type II symptoms warrant full

U.S. Navy Diving Manual — Volume 5

extensions at 60 fsw even if symptoms resolve during the first oxygen breathing
period.
17-4.6

Decompression Sickness in the Water. In rare instances, decompression sickness

may develop in the water while the diver is undergoing decompression. The
predominant symptom will usually be joint pain, but more serious manifestations
such as numbness, weakness, hearing loss, and vertigo may also occur.
Decompression sickness is most likely to appear at the shallow decompression
stops just prior to surfacing. Some cases, however, have occurred during ascent
to the first stop or shortly thereafter. Treatment of decompression sickness in
the water will vary depending on the type of diving equipment in use. Specific
guidelines are given in Chapter 9 for air dives, Chapter 12 for surface-supplied
helium-oxygen dives, and Chapter 15 for EC-UBA dives.
17-4.7

Symptomatic Omitted Decompression. If a diver has had an uncontrolled ascent

and has any symptoms, he should be compressed immediately in a recompression
chamber to 60 fsw. Conduct a rapid assessment of the patient and treat accordingly.
priate treatment for symptomatic omitted
Treatment Table 5 is not an appro­
decompression. If the diver surfaced from 50 fsw or shallower, compress to 60
fsw and begin Treatment Table 6. If the diver surfaced from a greater depth,
compress to 60 fsw or the depth where the symp­toms are significantly improved,
not to exceed 165 fsw, and begin Treatment Table 6A. Consultation with a Diving
Medical Officer should be obtained as soon as possible. For uncontrolled ascent
deeper than 165 feet, the diving supervisor may elect to use Treatment Table 8 at
the depth of relief, not to exceed 225 fsw.
Treatment of symptomatic divers who have surfaced unexpectedly is difficult when
no recompression chamber is on the dive station. Immediate transportation, while
receiving 100% surface oxygen, to a recom­pression facility is indicated; if this is
impossible, the guidelines in paragraph 17‑5.4 may be useful.
17-4.8

Altitude Decompression Sickness. Decompression sickness may also occur with

exposure to subatmospheric pres­sures (altitude exposure), as in an altitude chamber
or sudden loss of cabin pressure in an aircraft. Aviators exposed to altitude may
experience symptoms of decompression sickness similar to those experienced by
divers. The only major difference is that symptoms of spinal cord involvement are
less common and symptoms of brain involvement are more frequent in altitude
decompression sick­ness than hyperbaric decompression sickness. Simple pain,
however, still accounts for the majority of symptoms.
17‑4.8.1

Joint Pain Treatment. If only joint pain was present but resolved before reaching
one ata from altitude, then the individual may be treated with two hours of 100
percent oxygen breathing at the surface followed by 24 hours of observation.

17‑4.8.2

Other Symptoms and Persistent Symptoms. For other symptoms or if joint pain
symptoms are present after return to one ata, the stricken individual should be
transferred to a recompression facility and treated on the appropriate treatment
table, even if the symptoms resolve while in transport. Individuals should be kept
on 100 percent oxygen during transfer to the recompression facility.

CHAPTER 17 — Diagnosis and Treatment of Decompression Sickness and Arterial Gas Embolism

17-13

17-5

RECOMPRESSION TREATMENT FOR DIVING DISORDERS
17-5.1

Primary Objectives. Table 17-1 gives the basic rules that shall be followed for all

recompression treat­ments. The primary objectives of recompression treatment are:

n Compress gas bubbles to a small volume, thus relieving local pressure and
restarting blood flow.
n Allow sufficient time for bubble resorption.
n Increase blood oxygen content and thus oxygen delivery to injured tissues.
17-5.2

Guidance on Recompression Treatment. Certain facets of recompression

treatment have been mentioned previously, but are so important that they cannot
be stressed too strongly:
n Treat promptly and adequately.
n The effectiveness of treatment decreases as the length of time between the
onset of symptoms and the treatment increases.
n Do not ignore seemingly minor symptoms. They can quickly become major
symptoms.
n Follow the selected treatment table unless changes are recommended by a
Diving Medical Officer.
n If multiple symptoms occur, treat for the most serious condition.

17-5.3

Recompression Treatment When Chamber Is Available. Oxygen treatment tables

are significantly more effective than air treatment tables. Air treatment tables shall
only be used after oxygen system failure or intolerable patient oxygen toxicity
problems with DMO recommendation. Treatment Table 4 can be used with or
without oxygen but should always be used with oxygen if it is available.

17-14

17‑5.3.1

Recompression Treatment With Oxygen. Use Oxygen Treatment Table 5, 6,
6A, 4, or 7, according to the flowcharts in Figure 17‑1, Figure 17‑2 and Figure
17‑3. The descent rate for all these tables is 20 feet per minute. Upon reaching a
treatment depth of 60 fsw or shallower place the patient on oxygen. For treatment
depths deeper than 60 fsw, use treatment gas if available.

17‑5.3.2

Recompression Treatments When Oxygen Is Not Available. Air Treatment Tables
1A, 2A, and 3 (Figures 17‑11, 17-12, and 17-13) are provided for use only as a last
resort when oxygen is not available. Use Air Treatment Table 1A if pain is relieved
at a depth less than 66 feet. If pain is relieved at a depth greater than 66 feet, use
Treatment Table 2A. Treatment Table 3 is used for treatment of serious symptoms
where oxygen cannot be used. Use Treatment Table 3 if symptoms are relieved

U.S. Navy Diving Manual — Volume 5

within 30 minutes at 165 feet. If symptoms are not relieved in less than 30 minutes
at 165 feet, use Treatment Table 4.
17-5.4

Recompression Treatment When No Recompression Chamber is Available. The

Diving Supervisor has two alternatives for recompression treatment when the
diving facility is not equipped with a recompression chamber. First and foremost,
the patient with suspected DCS or AGE should be administered 100% oxygen
during transport, if available. If recompression of the patient is not immediately
necessary, the diver may be transported to the nearest appropriate recompression
chamber or the Diving Supervisor may elect to complete in-water recompression.
17‑5.4.1

Transporting the Patient. In certain instances, some delay may be unavoidable

17‑5.4.1.1

Medical Treatment During Transport. Always have the patient breathe 100 percent

17‑5.4.1.2

Transport by Unpressurized Aircraft. If the patient is moved by helicopter or
other unpressurized aircraft, the aircraft should be flown as low as safely possible,
preferably less than 1,000 feet. Expo­
sure to altitude results in an additional
reduction in external pressure and possible additional symptom severity or other
complications. If available, always use aircraft that can be pressurized to one
atmosphere. If available, transport using the Emergency Evacuation Hyperbaric
Stretcher should be considered.

17‑5.4.1.3

Communications with Chamber. Call ahead to ensure that the chamber will

while the patient is trans­ported to a recompression chamber. While moving the
patient to a recompression chamber, the patient should be kept supine (lying
horizontally). Do not put the patient head-down. Additionally, the patient should
be kept warm and monitored continuously for signs of obstructed (blocked)
airway, cessation of breathing, cardiac arrest, or shock. Always keep in mind that a
number of conditions may exist at the same time. For example, the victim may be
suffering from both decom­pression sickness and hypothermia.
oxygen during transport, if available. If symptoms of decompression sickness or
arterial gas embolism are relieved or improve after breathing 100 percent oxygen,
the patient should still be recom­pressed as if the original symptom(s) were still
present. Always ensure the patient is adequately hydrated. Give fluids by mouth if
the patient is alert and able to tolerate them. Otherwise, an IV should be inserted
and intravenous fluids should be started before transport. If the patient must
be transported, initial arrangements should have been made well in advance of
the actual diving operations. These arrangements, which would include an alert
notification to the recompression chamber and determination of the most effective
means of transportation, should be posted on the Job Site Emergency Assistant
Checklist for instant referral.

be ready and that qualified medical personnel will be standing by. If two-way

CHAPTER 17 — Diagnosis and Treatment of Decompression Sickness and Arterial Gas Embolism

17-15

communications can be established, consult with the doctor as the patient is being
transported.
17‑5.4.2

In-Water Recompression. Recompression in the water should be considered an

17‑5.4.2.1

In-Water Recompression Using Air. In-water recompression using air is always
less preferable than in-water recompression using oxygen.

option of last resort, to be used only when no recompression facility is on site,
symptoms are significant and there is no prospect of reaching a recompression
facility within a reasonable time­
frame (12–24 hours). In an emergency, an
uncertified chamber may be used if, in the opinion of a qualified Chamber
Supervisor (DSWS Watchstation 305), it is safe to operate. In divers with severe
Type II symptoms, or symptoms of arterial gas embolism (e.g., unconsciousness,
paralysis, vertigo, respiratory distress (chokes), shock, etc.), the risk of increased
harm to the diver from in-water recompression probably outweighs any antici­pated
benefit. Generally, these individuals should not be recompressed in the water, but
should be kept at the surface on 100 percent oxygen, if available, and evacuated
to a recompression facility regardless of the delay. The stricken diver should begin
breathing 100 percent oxygen immediately (if it is available). Continue breathing
oxygen at the surface for 30 minutes before committing to recompress in the
water. If symptoms stabilize, improve, or relief on 100 percent oxygen is noted, do
not attempt in-water recompression unless symptoms reappear with their original
intensity or worsen when oxygen is discontinued. Continue breathing 100 percent
oxygen as long as supplies last, up to a maximum time of 12 hours. The patient
may be given air breaks as necessary. If surface oxygen proves ineffective after 30
minutes, begin in-water recompression. To avoid hypothermia, it is important to
consider water temperature when performing in-water recompression.

n Follow Air Treatment Table 1A as closely as possible.
n Use either a full face mask or, preferably, a surface-supplied helmet UBA.
n Never recompress a diver in the water using a SCUBA with a mouth piece
unless it is the only breathing source available.
n Maintain constant communication.
n Keep at least one diver with the patient at all times.
n Plan carefully for shifting UBAs or cylinders.
n Have an ample number of tenders topside.
n If the depth is too shallow for full treatment according to Air Treatment
Table 1A:
n Recompress the patient to the maximum available depth.
n Remain at maximum depth for 30 minutes.
n Decompress according to Air Treatment Table 1A. Do not use stops shorter
than those of Air Treatment Table 1A.

17-16

U.S. Navy Diving Manual — Volume 5

17‑5.4.2.2

In-Water Recompression Using Oxygen. If 100 percent oxygen is available to the

diver using an oxygen rebreather, an ORCA, or other device, the following inwater recompression procedure should be used instead of Air Treatment Table 1A:
n Put the stricken diver on the UBA and have the diver purge the apparatus at
least three times with oxygen.
n Descend to a depth of 30 feet with a standby diver.

n Remain at 30 feet, at rest, for 60 minutes for Type I symptoms and 90
minutes for Type II symptoms. Ascend to 20 feet even if symptoms are still
present.
n Decompress to the surface by taking 60-minute stops at 20 feet and 10 feet.
n After surfacing, continue breathing 100 percent oxygen for an additional
3 hours.
n If symptoms persist or recur on the surface, arrange for transport to a
recompression facility regardless of the delay.
17‑5.4.2.3

17-6

Symptoms After In-Water Recompression. The occurrence of Type II symptoms

after in-water recompression is an ominous sign and could progress to severe,
debilitating decompression sickness. It should be considered life-threatening.
Operational considerations and remoteness of the dive site will dictate the speed
with which the diver can be evacuated to a recom­pression facility.

TREATMENT TABLES
17-6.1

Air Treatment Tables. Air Treatment Tables 1A, 2A, and 3 (Figures 17-11, 17-12,

and 17-13) are provided for use only as a last resort when oxygen is not available.
Oxygen treatment tables are signifi­cantly more effective than air treatment tables
and shall be used whenever possible.
17-6.2

Treatment Table 5. Treatment Table 5, Figure 17-4, may be used for the following:

n Type I DCS (except for cutis marmorata) symptoms when a complete
neurological examination has revealed no other abnormality. After arrival
at 60 fsw a neurological exam shall be performed to ensure that no overt
neuro­logical symptoms (e.g., weakness, numbness, loss of coordination)
are present. If any abnormalities are found, the stricken diver should be
treated using Treatment Table 6.
n Asymptomatic omitted decompression
n Treatment of resolved symptoms following in-water recompression
n Follow-up treatments for residual symptoms
n Carbon monoxide poisoning
n Gas gangrene

CHAPTER 17 — Diagnosis and Treatment of Decompression Sickness and Arterial Gas Embolism

17-17

17-6.3

Treatment Table 6. Treatment Table 6, Figure 17-5, is used for the following:

n Arterial gas embolism
n Type II DCS symptoms
n Type I DCS symptoms where relief is not complete within 10 minutes
at 60 feet or where pain is severe and immediate recompression must be
instituted before a neurological examination can be performed
n Cutis marmorata
n Severe carbon monoxide poisoning, cyanide poisoning, or smoke inhalation
n Asymptomatic omitted decompression
n Symptomatic uncontrolled ascent
n Recurrence of symptoms shallower than 60 fsw
17-6.4

Treatment Table 6A. Treatment Table 6A, Figure 17-6, is used to treat arterial gas

embolism or decom­pression symptoms when severe symptoms remain unchanged
or worsen within the first 20 minutes at 60 fsw. The patient is compressed to depth
of relief (or signifi­cant improvement), not to exceed 165 fsw. Once at the depth
of relief, begin treatment gas (N2O2, HeO2) if available. Consult with a Diving
Medical Officer at the earliest opportunity. If the severity of the patient’s condition
warrants, the Diving Medical Officer may recommend conversion to a Treatment
Table 4.
NOTE

17-6.5

If deterioration or recurrence of symptoms is noted during ascent to 60
feet, treat as a recurrence of symptoms (Figure 17‑3).
Treatment Table 4. Treatment Table 4, Figure 17-7, is used when it is determined
that the patient would receive additional benefit at depth of significant relief, not
to exceed 165 fsw. The time at depth shall be between 30 to 120 minutes, based
on the patient’s response. If a shift from Treatment Table 6A to Treatment Table 4
is contemplated, a Diving Medical Officer should be consulted before the shift is
made.

If oxygen is available, the patient should begin oxygen breathing periods immedi­
ately upon arrival at the 60-foot stop. Breathing periods of 25 minutes on oxygen,
interrupted by 5 minutes of air, are recommended because each cycle lasts 30
minutes. This simplifies timekeeping. Immediately upon arrival at 60 feet, a
minimum of four oxygen breathing periods (for a total time of 2 hours) should
be administered. After that, oxygen breathing should be administered to suit the
patient’s individual needs and operational conditions. Both the patient and tender
must breathe oxygen for at least 4 hours (eight 25-minute oxygen, 5-minute air
periods), beginning no later than 2 hours before ascent from 30 feet is begun. These
oxygen-breathing periods may be divided up as convenient, but at least 2 hours’
worth of oxygen breathing periods should be completed at 30 feet.
NOTE

17-18

If deterioration or recurrence of symptoms is noted during ascent to 60

U.S. Navy Diving Manual — Volume 5

feet, treat as a recurrence of symptoms (Figure 17‑3).
17-6.6

Treatment Table 7. Treatment Table 7, Figure 17-8, is an extension at 60 feet

of Treatment Table 6, 6A, or 4 (or any other nonstandard treatment table). This
means that considerable treatment has already been administered. Treatment
Table 7 is considered a heroic measure for treating non-responding severe gas
embolism or life-threatening decompression sickness and is not designed to treat
all residual symptoms that do not improve at 60 feet and should never be used
to treat residual pain. Treatment Table 7 should be used only when loss of life
may result if the currently prescribed decompression from 60 feet is undertaken.
Committing a patient to a Treatment Table 7 involves isolating the patient and
having to minister to his medical needs in the recompression chamber for 48 hours
or longer. Experienced diving medical personnel shall be on scene.
A Diving Medical Officer should be consulted before shifting to a Treatment
Table 7 and careful consideration shall be given to life support capability of the
recompression facility. Because it is difficult to judge whether a particular patient’s
condition warrants Treatment Table 7, additional consultation may be obtained
from either NEDU or NDSTC.

When using Treatment Table 7, a minimum of 12 hours should be spent at 60
feet, including time spent at 60 feet from Treatment Table 4, 6, or 6A. Severe
Type II decompression sickness and/or arterial gas embolism cases may continue
to dete­riorate significantly over the first several hours. This should not be cause for
premature changes in depth. Do not begin decompression from 60 feet for at least
12 hours. At completion of the 12-hour stay, the decision must be made whether
to decompress or spend additional time at 60 feet. If no improvement was noted
during the first 12 hours, benefit from additional time at 60 feet is unlikely and
decompression should be started. If the patient is improving but significant residual
symptoms remain (e.g., limb paralysis, abnormal or absent respiration), additional
time at 60 feet may be warranted. While the actual time that can be spent at 60 feet
is unlimited, the actual additional amount of time beyond 12 hours that should be
spent can only be determined by a Diving Medical Officer (in consultation with
on-site supervisory personnel), based on the patient’s response to therapy and
operational factors. When the patient has progressed to the point of consciousness,
can breathe independently, and can move all extremities, decom­
pression can
be started and maintained as long as improvement continues. Solid evidence of
continued benefit should be established for stays longer than 18 hours at 60 feet.
Regardless of the duration at the recompression deeper than 60 feet, at least 12
hours must be spent at 60 feet and then Treatment Table 7 followed to the surface.
Additional recompression below 60 feet in these cases should not be undertaken
unless adequate life support capability is available.
17‑6.6.1

Decompression. Decompres­sion on Treatment Table 7 is begun with an upward
excursion at time zero from 60 to 58 feet. Subsequent 2-foot upward excursions
are made at time intervals listed as appropriate to the rate of decompression:

CHAPTER 17 — Diagnosis and Treatment of Decompression Sickness and Arterial Gas Embolism

17-19

Table 17-3. Decompression
Depth

Ascent Rate

Time Interval

58-40 feet

3 ft/hr

40 min

40-20 feet

2 ft/hr

60 min

20-4 feet

1 ft/hr

120 min

The travel time between stops is considered as part of the time interval for the next
shallower stop. The time intervals shown above begin when ascent to the next
shallower stop has begun.
17-6.6.2

Tenders. When using Treatment Table 7, tenders breathe chamber atmosphere
throughout treatment and decompression.

17‑6.6.3

Preventing Inadvertent Early Surfacing. Upon arrival at 4 feet, decompression

17‑6.6.4

Oxygen Breathing. On a Treatment Table 7, patients should begin oxygen breathing

17‑6.6.5

Sleeping, Resting, and Eating. At least two tenders should be available when

17‑6.6.6

17-20

should be stopped for 4 hours. At the end of 4 hours, decompress to the surface at
1 foot per minute. This procedure prevents inadvertent early surfacing.

periods as soon as possible at 60 feet. Oxygen breathing periods of 25 minutes on
100 percent oxygen, followed by 5 minutes breathing chamber atmosphere, should
be used. Normally, four oxygen breathing periods are alternated with 2 hours of
continuous air breathing. In conscious patients, this cycle should be continued until
a minimum of eight oxygen breathing periods have been administered (previous
100 percent oxygen breathing periods may be counted against these eight periods).
Beyond that, oxygen breathing periods should be continued as recommended by
the Diving Medical Officer, as long as improvement is noted and the oxygen is
tolerated by the patient. If oxygen breathing causes significant pain on inspiration,
it should be discontinued unless it is felt that significant benefit from oxygen
breathing is being obtained. In unconscious patients, oxygen breathing should be
stopped after a maximum of 24 oxygen breathing periods have been administered.
The actual number and length of oxygen breathing periods should be adjusted by
the Diving Medical Officer to suit the individual patient’s clinical condition and
development of pulmonary oxygen toxicity.

using Treatment Table 7, and three may be necessary for severely ill patients. Not
all tenders are required to be in the chamber, and they may be locked in and out
as required following appropriate decompression tables. The patient may sleep
anytime except when breathing oxygen deeper than 30 feet. While asleep, the
patient’s pulse, respiration, and blood pressure should be monitored and recorded
at intervals appropriate to the patient’s condition. Food may be taken at any time
and fluid intake should be maintained.
Ancillary Care. Patients on Treatment Table 7 requiring intravenous fluid and/or

drug therapy should have these administered in accordance with paragraph 17‑12
and associated subparagraphs.

U.S. Navy Diving Manual — Volume 5

17‑6.6.7

Life Support. Before committing to a Treatment Table 7, the life-support consider-

17-6.7

Treatment Table 8. Treatment Table 8, Figure 17-9, is an adaptation of Royal Navy

ations in para­graph 17-7 must be addressed. Do not commit to a Treatment Table 7
if the internal chamber temperature cannot be maintained at 85°F (29°C) or less.

Treatment Table 65 mainly for treating deep uncontrolled ascents (see Chapter
13) when more than 60 minutes of decompression have been missed. Compress
symptomatic patient to depth of relief not to exceed 225 fsw. Initiate Treatment
Table 8 from depth of relief. The schedule for Treatment Table 8 from 60 fsw is
the same as Treatment Table 7. The guidelines for sleeping and eating are the same
as Treatment Table 7.

17-6.8

Treatment Table 9. Treatment Table 9, Figure 17-10, is a hyperbaric oxygen

treatment table providing 90 minutes of oxygen breathing at 45 feet. This table
is used only on the recommendation of a Diving Medical Officer cognizant of the
patient’s medical condition. Treatment Table 9 is used for the following:

1. Residual symptoms remaining after initial treatment of AGE/DCS
2. Selected cases of carbon monoxide or cyanide poisoning
3. Smoke inhalation

This table may also be recommended by the cognizant Diving Medical Officer
when initially treating a severely injured patient whose medical condition precludes
long absences from definitive medical care.
17-7

RECOMPRESSION TREATMENT FOR NON-DIVING DISORDERS

In addition to individuals suffering from diving-related disorders, U.S. Navy
recompres­sion chambers are also permitted to conduct emergent hyperbaric oxygen
(HBO2) therapy to treat individuals suffering from cyanide poisoning, carbon
monoxide poisoning, gas gangrene, smoke inhalation, necrotizing soft-tissue
infections, or arterial gas embolism arising from surgery, diagnostic procedures,
or thoracic trauma. If the chamber is to be used for treatment of non-diving related
medical conditions other than those listed above, authorization from BUMED Code
M95 shall be obtained before treatment begins (BUMEDINST 6320.38 series.)
Any treatment of a non-diving related medical condition shall be done under the
cognizance of a Diving Medical Officer.
The guidelines given in Table 17-4 for conducting HBO2 therapy are taken from the
Undersea and Hyperbaric Medical Society’s Hyperbaric Oxygen (HBO2) Therapy
Committee Report-2014: Approved Indications for Hyperbaric Oxygen Therapy.
For each condition, the guidelines prescribe the recommended Treatment Table,
the frequency of treatment, and the minimum and maximum number of treatments.

CHAPTER 17 — Diagnosis and Treatment of Decompression Sickness and Arterial Gas Embolism

17-21

Table 17‑4. Guidelines for Conducting Hyperbaric Oxygen Therapy.

17-8

Minimum #
Treatments

Maximum #
Treatments

1-3

3

Indication

Treatment Table

Carbon Monoxide
Poisoning, acute

Treatment Table 5 or Table
6 as recommended by the
DMO

Gas Gangrene (Clostridial
Myonecrosis)

Treatment Table 5

3 times in 24 hours
2 times per day for the
next 2-5 days

10

Crush Injury, Compartment
Syndrome, and other
Acute Traumatic Ischemia

Treatment Table 9

2 times per day for 2-7
days

14

Central Retinal Artery
Occlusion

Treatment Table 6

2 times daily to clinical
plateau (typically < 1
week) plus 3 days

3 days after
clinical plateau

Diabetic Foot Ulcer

Treatment Table 9

Daily for 3-4 weeks,
based on healing
response

30

Healing of Other Problem
Wounds

Treatment Table 9

Daily for 3-4 weeks,
based on healing
response

60

Severe Anemia

Treatment Table 5 or Table
9 as recommended by
DMO

3-4 times per day until
blood replacement by
transfusion or regrowth

variable, guided
by clinical
response

Intracranial Abscess

Treatment Table 9

1-2 times daily for up to
3 weeks

20

Necrotizing Soft Tissue
Infection

Treatment Table 9

2 times daily until
stabilization

30

Refractory Osteomyelitis

Treatment Table 5 or Table
9 as recommended by
DMO

20-40 treatments

40

Delayed Radiation Injury,
Soft Tissue Necrosis, Bony
Necrosis

Treatment Table 9

For radiation injury:
30-60 treatments
For prophylaxis: 20 treatments before surgery
in radiated field; 10
sessions after surgery

60

Compromised Grafts and
Flaps

Treatment Table 9

2 times daily up to 30
treatments

20

Acute Thermal Burn Injury

Treatment Table 9

2 times daily up to 30
treatments

30

Idiopathic Sudden
Sensori-neural Hearing
Loss

Treatment Table 9

10-20 treatments

20

RECOMPRESSION CHAMBER LIFE-SUPPORT CONSIDERATIONS

The short treatment tables (Oxygen Treatment Tables 5, 6, 6A, 9; Air Treatment
Tables 1A and 2A) can be accomplished easily without significant strain on either
the recompression chamber facility or support crew. The long treatment tables
(Tables 3, 4, 7, and 8) will require long periods of decompression and may tax both
personnel and hardware severely.

17-22

U.S. Navy Diving Manual — Volume 5

17-8.1

Oxygen Control. All treatment schedules listed in this chapter are usually

performed with a chamber atmosphere of air. To accomplish safe decompression,
the oxygen percentage should not be allowed to fall below 19 percent. Oxygen
may be added to the chamber by ventilating with air or by bleeding in oxygen
from an oxygen breathing system. If a portable oxygen analyzer is available, it
can be used to determine the adequacy of ventilation and/or addition of oxygen.
If no oxygen analyzer is available, ventilation of the chamber in accordance with
paragraph 17-8.4 will ensure adequate oxygenation. Chamber oxygen percentages
as high as 25 percent are permitted. If the chamber is equipped with a life-support
system so that ventilation is not required and an oxygen analyzer is available, the
oxygen level should be maintained between 19 percent and 25 percent. If chamber
oxygen goes above 25 percent, ventilation with air should be used to bring the
oxygen percentage down.
17-8.2

Carbon Dioxide Control. Ventilation of the chamber in accordance with paragraph

17-8.4 will ensure that carbon dioxide produced metabolically does not cause the
chamber carbon dioxide level to exceed 1.5 percent SEV (11.4 mmHg).

17‑8.2.1

17‑8.2.2

17‑8.2.3

17-8.3

Carbon Dioxide Monitoring. Chamber carbon dioxide should be monitored with

electronic carbon dioxide monitors. Monitors generally read CO2 percentage once
chamber air has been exhausted to the surface. The CO2 percent reading at the
surface 1 ata must be corrected for depth. To keep chamber CO2 below 1.5 percent
SEV (11.4 mmHg), the surface CO2 monitor values should remain below 0.78
percent with chamber depth at 30 feet, 0.53 percent with chamber depth at 60 feet,
and 0.25 percent with the chamber at 165 feet. If the CO2 analyzer is within the
chamber, no correction to the CO2 readings is necessary.
Carbon Dioxide Scrubbing. If the chamber is equipped with a carbon dioxide

scrubber, the absorbent should be changed when the partial pressure of carbon dioxide in the chamber reaches 1.5 percent SEV (11.4 mmHg). If absorbent cannot be
changed, supplemental chamber ventilation will be required to maintain chamber
CO2 at acceptable levels. With multiple or working chamber occupants, supplemental ventilation may be necessary to maintain chamber CO2 at acceptable levels.
Carbon Dioxide Absorbent. CO2 absorbent in an opened but resealed bucket may
be used until the expiration date on the bucket is reached. Pre-packed, doublebagged canisters shall be labeled with the expiration date from the absorbent
bucket. Expired CO2 absorbent shall not be used in any recompression chamber.
Temperature Control. Internal chamber temperature should be maintained at a

level comfortable to the occupants whenever possible. Cooling can usually be
accomplished by chamber ventilation. If the chamber is equipped with a heater/
chiller unit, temperature control can usually be maintained for chamber occupant
comfort under any external environmental conditions. Usually, recompression
chambers will become hot and must be cooled continuously. Chambers should
always be shaded from direct sunlight. The maximum durations for chamber
occupants will depend on the internal chamber temperature as listed in Table 175. Never commit to a treatment table that will expose the chamber occupants to

CHAPTER 17 — Diagnosis and Treatment of Decompression Sickness and Arterial Gas Embolism

17-23

greater temperature/time combina­tions than listed in Table 17-5 unless qualified
medical personnel who can evaluate the trade-off between the projected heat stress
and the anticipated treat­ment benefit are consulted. A chamber temperature below
85°F (29°C) is always desirable, no matter which treatment table is used.
For patients with brain or spinal cord damage, the current evidence recommends
aggressive treatment of elevated body temperature. When treating victims of AGE
or severe neurological DCS, hot environments that elevate body temperature above
normal should be avoided, whenever possible. Patient tempera­ture should be a
routinely monitored vital sign.
Table 17‑5. Maximum Permissible Recompression Chamber Exposure Times at
Various Internal Chamber Temperatures.
Internal Temperature

Maximum Tolerance Time

Permissible Treatment Tables

Over 104°F
(40°C)

Intolerable

No treatments

95–104°F
(34.4–40°C)

2 hours

Table 5, 9

85–94°F
(29–34.4°C)

6 hours

Tables 5, 6, 6A, 1A, 9

Under 85°F
(29°C)

Unlimited

All treatments

NOTE:
Internal chamber temperature can be kept considerably below ambient by venting or by using an
installed chiller unit. Internal chamber temperature can be measured using electronic, bimetallic,
alcohol, or liquid crystal thermometers. Never use a mercury thermometer in or around hyperbaric
chambers. Since chamber ventilation will produce temperature swings during ventilation, the above
limits should be used as averages when controlling temperature by ventilation. Always shade chamber
from direct sunlight.

17‑8.3.1

17-24

Patient Hydration. Always ensure patients are adequately hydrated. Fully
conscious patients may be given fluid by mouth to maintain adequate hydration.
One to two liters of water, juice, or non-carbonated drink, over the course of a
Treatment Table 5 or 6, is usually sufficient. Patients with Type II symptoms, or
symptoms of arterial gas embolism, should be considered for IV fluids. Stuporous
or unconscious patients should always be given IV fluids, using large-gauge
plastic catheters. If trained personnel are present, an IV should be started as soon
as possible and kept drip­ping at a rate of 75 to 100 cc/hour, using isotonic fluids
(Lactated Ringer’s Solution, Normal Saline) until specific instructions regarding
the rate and type of fluid administration are given by qualified medical personnel.
Avoid solutions containing glucose (Dextrose) if brain or spinal cord injury is
present. Intravenously administered glucose may worsen the outcome. In some
cases, the bladder may be paralyzed. The victim’s ability to void shall be assessed
as soon as possible. If the patient cannot empty a full bladder, a urinary catheter
shall be inserted as soon as possible by trained personnel. Always inflate catheter
balloons with liquid, not air. Adequate fluid is being given when urine output is at
least 0.5cc/kg/hr. Thirst is an unreliable indi­cator of the water intake to compensate

U.S. Navy Diving Manual — Volume 5

for heavy sweating. A useful indicator of proper hydration is a clear colorless
urine.
17-8.4

Chamber Ventilation. Ventilation is the usual means of controlling oxygen

level, carbon dioxide level, and temperature. Ventilation using air is required
for chambers without carbon dioxide scrubbers and atmospheric analysis. A
ventilation rate of two acfm for each resting occupant, and four acfm for each
active occupant, should be used. These procedures are designed to assure that the
effective concentration of carbon dioxide will not exceed 1.5 percent sev (11.4
mmHg) and that, when oxygen is being used, the percentage of oxygen in the
chamber will not exceed 25 percent.
17-8.5

Access to Chamber Occupants. Recompression treatments usually require access

to occupants for passing in items such as food, water, and drugs and passing out
such items as urine, excrement, and trash. Never attempt a treatment longer than
a Treatment Table 6 unless there is access to inside occupants. When doing a
Treatment Table 4, 7, or 8, a double-lock chamber is mandatory because additional
personnel may have to be locked in and out during treatment.

17‑8.6

Inside Tender Oxygen Breathing. During treatments, all chamber occupants may

breathe 100 percent oxygen at depths of 45 feet or shallower without locking in
additional personnel. Tenders should not fasten the oxygen masks to their heads,
but should hold them on their faces. When deeper than 45 feet, at least one chamber
occupant must breathe air. Tender oxygen breathing requirements are specified in
the figure for each Treat­ment Table.
17‑8.7

Tending Frequency. Normally, tenders should allow a surface interval of at least

18 hours between consecutive treatments on Treatment Tables 1A, 2A, 3, 5, 6, and
6A, and at least 48 hours between consecutive treatments on Tables 4, 7, and 8. If
necessary, however, tenders may repeat Treatment Tables 5, 6, or 6A within this
18-hour surface interval if oxygen is breathed at 30 feet and shallower as outlined
in Table 17-7. Minimum surface intervals for Treatment Tables 1A, 2A, 3, 4, 7,
and 8 shall be strictly observed.

17-8.8

Equalizing During Descent. Descent rates may have to be decreased as necessary

to allow the patient to equalize; however, it is vital to attain treatment depth in a
timely manner for a suspected arterial gas embolism patient.
17-8.9

Use of High Oxygen Mixes. High oxygen N2O2/HeO2 mixtures may be used to

treat patients when recompres­sion deeper than 60 fsw is required. These mixtures
offer significant therapeutic advantages over air. Select a treatment gas that will
produce a ppO2 between 1.5 and 3.0 ata at the treatment depth. The standardized
gas mixtures shown in Table 17-6 are suitable over the depth range of 61-225 fsw.
Decompression sickness following helium dives can be treated with either nitrogen
or helium mixtures. For recompression deeper than 165 fsw, helium mixtures are
preferred to avoid narcosis. The situation is less clear for treatment of decompression
sickness following air or nitrogen-oxygen dives. Experimental studies have shown
both benefit and harm with helium treatment. Until more experience is obtained,
CHAPTER 17 — Diagnosis and Treatment of Decompression Sickness and Arterial Gas Embolism

17-25

high oxygen mixtures with nitrogen as the diluent gas are preferred if available.
High oxygen mixtures may also be substituted for 100% oxygen at 60 fsw and
shallower on Treatment Tables 4, 7, and 8 if the patient is unable to tolerate 100%
oxygen.
Table 17‑6. High Oxygen Treatment Gas Mixtures.

17-8.10

Depth (fsw)

Mix (HeO2 or N2O2)

ppO2

0-60

100%

1.00-2.82

61-165

50/50

1.42-3.00

166-225

64/36 (HeO2 only)

2.17-2.81

Oxygen Toxicity During Treatment. Acute CNS oxygen toxicity may develop on

any oxygen treatment table.

During prolonged treatments on Treatment Tables 4, 7, or 8, and with repeated
Treatment Table 6, pulmonary oxygen toxicity may also develop.
17‑8.10.1

Central Nervous System Oxygen Toxicity. When employing the oxygen treatment

tables, tenders must be particularly alert for the early symptoms of CNS oxygen
toxicity. The symptoms can be remem­
bered readily by using the mnemonic
VENTID-C (Vision, Ears, Nausea, Twitching\Tingling, Irritability, Dizziness,
Convulsions). Unfortunately, a convul­sion may occur without early warning signs
or before the patient can be taken off oxygen in response to the first sign of CNS
oxygen toxicity. CNS oxygen toxicity is unlikely in resting individuals at chamber
depths of 50 feet or shallower and very unlikely at 30 feet or shallower, regardless
of the level of activity. However, patients with severe Type II decompression
sickness or arterial gas embolism symptoms may be abnormally sensitive to CNS
oxygen toxicity. Convulsions unrelated to oxygen toxicity may also occur and may
be impossible to distinguish from oxygen seizures.
At the first sign of CNS
oxygen toxicity, the patient should be removed from oxygen and allowed to
breathe chamber air. Fifteen minutes after all symptoms have subsided, resume
oxygen breathing. For Treatment Tables 5, 6, 6A resume treatment at the point of
interruption. For Treatment Tables 4, 7 and 8 no compen­satory lengthening of the
table is required. If symptoms of CNS oxygen toxicity develop again or if the first
symptom is a convulsion, take the follow action:

17‑8.10.1.1 Procedures in the Event of CNS Oxygen Toxicity.

CAUTION

Inserting an airway device or bite block is not recommended while
the patient is convulsing; it is not only difficult, but may cause harm if
attempted.

For Treatment Tables 5, 6, and 6A:
n Remove the mask.

17-26

U.S. Navy Diving Manual — Volume 5

n After all symptoms have completely subsided, decompress 10 feet at a
rate of 1 fsw/min. For a convulsion, begin travel when the patient is fully
relaxed and breathing normally.
n Resume oxygen breathing at the shallower depth at the point of interruption.
n If another oxygen symptom occurs after ascending 10 fsw, contact a Diving
Medical Officer to recommend appropriate modifications to the treatment
schedule.
For Treatment Tables 4, 7, and 8:
n Remove the mask.
n Consult with a Diving Medical Officer before administering further
oxygen breathing. No compensatory lengthening of the table is required
for interruption in oxygen breathing.
17‑8.10.2

17-8.11

Pulmonary Oxygen Toxicity. Pulmonary oxygen toxicity is unlikely to develop on

single Treatment Tables 5, 6, or 6A. On Treatment Tables 4, 7, or 8 or with repeated
Treatment Tables 5, 6, or 6A (especially with extensions) prolonged exposure to
oxygen may result in end-inspiratory discomfort, progressing to substernal burning
and severe pain on inspi­ration. If a patient who is responding well to treatment
complains of substernal burning, discontinue use of oxygen and consult with a
DMO. However, if a signif­icant neurological deficit remains and improvement
is continuing (or if deterioration occurs when oxygen breathing is interrupted),
oxygen breathing should be continued as long as considered beneficial or until
pain limits inspira­tion. If oxygen breathing must be continued beyond the period
of substernal burning, or if the 2-hour air breaks on Treatment Tables 4, 7, or 8
cannot be used because of deterioration upon the discontinuance of oxygen, the
oxygen breathing periods should be changed to 20 minutes on oxygen, followed
by 10 minutes breathing chamber air or alternative treatment gas mixtures with
a lower percentage of oxygen should be considered. The Diving Medical Officer
may tailor the above guidelines to suit individual patient response to treatment.
Loss of Oxygen During Treatment. Loss of oxygen breathing capability during

oxygen treatments is a rare occurrence. However, should it occur, the following
actions should be taken:
If repair can be completed within 15 minutes:
n Maintain depth until repair is completed.
n After O2 is restored, resume treatment at point of interruption.

If repair can be completed after 15 minutes but before 2 hours:
n Maintain depth until repair is completed.
n After O2 is restored: If original table was Table 5, 6, or 6A, complete treat­
ment with maximum number of O2 extensions.

CHAPTER 17 — Diagnosis and Treatment of Decompression Sickness and Arterial Gas Embolism

17-27

17‑8.11.1

17‑8.11.2

17-8.12

Compensation. If Table 4, 7, or 8 is being used, no compensation in decompression

is needed if oxygen is lost. If decompression must be stopped because of worsening
symptoms in the affected diver, then stop decompression. When oxygen is restored,
continue treatment from where it was stopped.
Switching to Air Treatment Table. If O2 breathing cannot be restored in 2 hours
switch to the comparable air treatment table at current depth for decompression
if 60 fsw or shallower. Rate of ascent must not exceed 1 fpm between stops. If
symptoms worsen and an increase in treatment depth deeper than 60 feet is needed,
use Treatment Table 4.
Treatment at Altitude. Before starting recompression therapy, zero the chamber

depth gauges to adjust for altitude. Then use the depths as specified in the treatment
table. There is no need to “Cross Correct” the treatment table depths. Divers
serving as inside tenders during hyperbaric treatments at altitude are performing
a dive at altitude and therefore require more decompression than at sea level.
Tenders locking into the chamber for brief periods should be managed according
to the Diving At Altitude procedures (paragraph 9-13). Tenders remaining in the
chamber for the full treatment table must breathe oxygen during the terminal
portion of the treatment to satisfy their decompression requirement.

The additional oxygen breathing required at altitude on Treatment Table 5, Treatment Table 6, and Treatment Table 6A is given in Table 17‑6. The requirement
pertains both to tenders equilibrated at altitude and to tenders flown directly from
sea level to the chamber location. Contact NEDU for guidance on tender oxygen
requirements for other treatment tables.
17-9

POST-TREATMENT CONSIDERATIONS

Tenders on Treatment Tables 5, 6, 6A, 1A, 2A, or 3 should have a minimum of
a 18-hour surface interval before no-decompression diving and a minimum of a
24-hour surface interval before dives requiring decompression stops. Tenders on
Treatment Tables 4, 7, and 8 should have a minimum of a 48-hour surface interval
prior to diving.
17-9.1

17-28

Post-Treatment Observation Period. After a treatment, patients treated on a Treatment Table 5 should remain at the recompression chamber facility for 2 hours. Patients who have been treated for Type II decompression sickness or who required
a Treatment Table 6 for Type I symptoms and have had complete relief should remain at the recompression chamber facility for 6 hours. Patients treated on Treatment Tables 6, 6A, 4, 7, 8 or 9 are likely to require a period of hospitalization,
and the Diving Medical Officer will need to determine a post-treatment observation period and location appro­priate to their response to recompression treatment.
These times may be shortened upon the recommendation of a Diving Medical Officer, provided the patient will be with personnel who are experienced at recognizing recurrence of symptoms and can return to the recompression facility within 30
minutes. All patients should remain within 60 minutes travel time of a recompression facility for 24 hours and should be accompanied throughout that period. No
patient shall be released until authorized by a DMO.

U.S. Navy Diving Manual — Volume 5

Treatment table profiles place the inside tender(s) at risk for decompression sick­
ness. After completing treatments, inside tenders should remain in the vicinity of
the recompression chamber for 1 hour. If they were tending for Treatment Table
4, 7, or 8, inside tenders should also remain within 60 minutes travel time of a
recompression facility for 24 hours.
Table 17‑7. Tender Oxygen Breathing Requirements. (Note 1)
Altitude
Treatment Table (TT)
TT5
Note (2)

TT6
Note (2)

TT6A
Note (2)

Surface to 2499 ft

2500 ft. - 7499 ft.

7500 ft. - 10,000 ft.

without extension

:00

:00

:00

with extension @ 30 fsw

:00

:00

:20

up to one extension @
60 fsw or 30 fsw

:30

:60

:90

more than one
extension

:60

:90

:120

up to one extension @
60 fsw or 30 fsw

:60

:120

:150 Note (3)

more than one
extension

:90

:150
Note (3)

:180
Note (3)

Note 1: All tender O2 breathing times in table are conducted at 30 fsw. In addition, tenders will breathe
O2 on ascent from 30 fsw to the surface.
Note 2: If the tender had a previous hyperbaric exposure within 18 hours, use the following guidance for
administering O2:
For TT5, add an additional 20 minute O2 breathing period to the times in the table.
For TT6 or TT6A, add an additional 60 minute O2 breathing period to the times in the table.
For other Treatment tables contact NEDU for guidance.
Note 3: In some instances, tender’s oxygen breathing obligation exceeds the table stay time at 30 fsw.
Extend the time at 30 fsw to meet these obligations if patient’s condition permits. Otherwise,
administer O2 to the tender to the limit allowed by the treatment table and observe the tender on
the surface for 1 hour for symptoms of DCS.

17-9.2

Post-Treatment Transfer. Patients with residual symptoms should be transferred

to appropriate medical facilities as directed by qualified medical personnel.
If ambulatory patients are sent home, they should always be accompanied by
someone familiar with their condition who can return them to the recompression
facility should the need arise. Patients completing treatment do not have to remain
in the vicinity of the chamber if the Diving Medical Officer feels that transferring
them to a medical facility immediately is in their best interest.

17-9.3

Flying After Treatments. Patients with residual symptoms should fly only with

the concurrence of a Diving Medical Officer. Patients who have been treated for
decompression sickness or arterial gas embolism and have complete relief should
not fly for 72 hours after treatment, at a minimum.

Tenders on Treatment Tables 5, 6, 6A, 1A, 2A, or 3 should have a 24-hour surface
interval before flying. Tenders on Treatment Tables 4, 7, and 8 should not fly for
72 hours.

CHAPTER 17 — Diagnosis and Treatment of Decompression Sickness and Arterial Gas Embolism

17-29

17‑9.3.1

Emergency Air Evacuation. Some patients will require air evacuation to another

17-9.4

Treatment of Residual Symptoms. After completion of the initial recompression

treatment or medical facility immediately after surfacing from a treatment. They
will not meet surface interval requirements as described above. Such evacuation is
done only on the recommen­dation of a Diving Medical Officer. Aircraft pressurized
to one ata should be used if possible, or unpressurized aircraft flown as low as
safely possible (no more than 1,000 feet is preferable). Have the patient breathe
100 percent oxygen during transport, if available. If available, an Emergency
Evacuation Hyperbaric Stretcher to maintain the patient at 1ata may be used.

treatment and after a surface interval sufficient to allow complete medical evaluation, additional recompression treat­ments may be instituted. If additional recompression treatments are indicated a Diving Medical Officer must be consulted. Residual symptoms may remain unchanged during the first one or two treatments.
In these cases, the Diving Medical Officer is the best judge as to the number of
recompression treatments. Consultation with NEDU or NDSTC may be appropriate. As the delay time between completion of initial treatment and the beginning
of follow-up hyperbaric treatments increases, the probability of benefit from additional treatments decreases. However, improvement has been noted in patients
who have had delay times of up to 1 week. Therefore, a long delay is not necessarily a reason to preclude follow-up treatments. Once residual symptoms respond
to additional recompression treatments, such treatments should be continued until
no further benefit is noted. In general, treatment may be discontinued if there is no
further sustained improvement after two consecutive treatments.
For persistent Type II symptoms, daily treatment on Table 6 may be used, but
twice-daily treatments on Treatment Tables 5 or 9 may also be used. The treatment
table chosen for re-treatments must be based upon the patient’s medical condition
and the potential for pulmonary oxygen toxicity. Patients surfacing from Treat­ment
Table 6A with extensions, 4, 7, or 8 may have severe pulmonary oxygen toxicity
and may find breathing 100 percent oxygen at 45 or 60 feet to be uncom­fortable
or even intolerable. In these cases, daily treatments at 30 feet may also be used.
As many oxygen breathing periods (25 minutes on oxygen followed by 5 minutes
on air) should be administered as can be tolerated by the patient. Ascent to the
surface is at 20 feet per minute. A minimum oxygen breathing time is 90 minutes.
A prac­tical maximum bottom time is 3 to 4 hours at 30 feet. Treatments should not
be administered on a daily basis for more than 5 days without a break of at least
1 day. These guidelines may have to be modified by the Diving Medical Officer
to suit individual patient circumstances and tolerance to oxygen as measured by
decrements in the patient’s vital capacity.
17-9.5

17-30

Returning to Diving after Recompression Treatment. Divers diagnosed with any
POIS or DCS shall be referred to a DMO for clearance prior to returning to diving.
In most cases, a waiver of the physical standards will be required from BUPERS
via BUMED. Refer to Bureau of Medicine and Surgery Manual (MANMED)
P117 Article 15-102 for guidance.

U.S. Navy Diving Manual — Volume 5

17-10

NON-STANDARD TREATMENTS

The treatment recommendations presented in this chapter should be followed as
closely as possible unless it becomes evident that they are not working. Only a
Diving Medical Officer may then recommend changes to treatment protocols or use
treatment techniques other than those described in this chapter. Any modifica­tions
to treatment tables shall be approved by the Commanding Officer. The standard
treatment procedures in this chapter should be considered minimum treatments.
Treatment procedures should never be shortened unless emergency situations arise
that require chamber occupants to leave the chamber early, or the patient’s medical
condition precludes the use of standard U.S. Navy treatment tables.
17-11

RECOMPRESSION TREATMENT ABORT PROCEDURES

Once recompression therapy is started, it should be completed according to the
procedures in this chapter unless the diver being treated dies or unless continuing
the treatment would place the chamber occupants in mortal danger or in order to
treat another more serious medical condition.
17-11.1

Death During Treatment. If it appears that the diver being treated has died, a
Diving Medical Officer shall be consulted before the treatment is aborted. Once
the decision to abort is made, there are a number of options for decompressing
the tenders depending on the depth at which the death occurred and the preceding
treatment profile.

n If death occurs following initial recompression to 60, 165, or 225 on Treatment
Tables 6, 6A, 4 or 8, decompress the tenders on the Air/Oxygen schedule in
the Air Decompression Table having a depth exactly equal to or deeper than
the maximum depth attained during the treatment and a bottom time equal to
or longer than the total elapsed time since treatment began. The Air/Oxygen
schedule can be used even if gases other than air (i.e., nitrogen-oxygen or
helium-oxygen mixtures) were breathed at depth.
n If death occurs after leaving the initial treatment depth on Treatment Tables 6
or 6A, decompress the tenders at 30 fsw/min to 30 fsw and have them breathe
oxygen at 30 fsw for the times indicated in Table 17-6. Following completion
of the oxygen breathing time at 30 fsw, decompress the tenders on oxygen from
30 fsw to the surface at 1 fsw/min.
n If death occurs after leaving the initial treatment depth on Treatment Tables
4 or 8, or after beginning treatment on Treatment Table 7 at 60 fsw, have the
tenders decompress by continuing on the treatment table as written, or consult
NEDU for a decompression schedule customized for the situation at hand. If
neither option is possible, follow the original treatment table to 60 fsw. At
60 fsw, have the tenders breathe oxygen for 90 min in three 30-min periods
separated by a 5-min air break. Continue decompression at 50, 40 and 30 fsw
by breathing oxygen for 60 min at each depth. Ascend between stops at 30 fsw/
min. At 50 fsw, breathe oxygen in two 30-min periods separated by a 5-min air

CHAPTER 17 — Diagnosis and Treatment of Decompression Sickness and Arterial Gas Embolism

17-31

break. At 40 and 30 fsw, breathe oxygen for the full 60-min period followed by
a 15-min air break. Ascend to 20 fsw at 30 fsw/min and breathe oxygen for 120
min. Divide the oxygen time at 20 fsw into two 60-min periods separated by a
15 min air break. When oxygen breathing time is complete at 20 fsw, ascend to
the surface at 30 fsw/min. Upon surfacing, observe the tenders carefully for the
occurrence of decompression sickness.
17-11.2

Impending Natural Disasters or Mechanical Failures. Impending natural disasters
or mechanical failures may force the treatment to be aborted. For instance, the
ship where the chamber is located may be in imminent danger of sinking or a fire
or explosion may have severely damaged the chamber system to such an extent
that completing the treatment is impossible. In these cases, the abort procedure
described in paragraph 17-11.1 could be used for all chamber occu­pants (including
the stricken diver) if time is available. If time is not available, the following may
be done:
1. If deeper than 60 feet, go immediately to 60 feet.
2. Once the chamber is 60 feet or shallower, put all chamber occupants on

continuous 100 percent oxygen. Select the Air/Oxygen schedule in the Air
Decompression Table corresponding to the maximum depth attained during
treatment and the total elapsed time since treatment began.

3. If at 60 fsw, breathe oxygen for period of time equal to the sum of all the

decompression stops 60 fsw and deeper in the Air/Oxygen schedule, then
continue decompression on the Air/Oxygen schedule, breathing oxygen
continuously. If shallower than 60 fsw, breathe oxygen for a period of time equal
to the sum of all the decompression stops deeper than the divers current depth,
then continue decompression on the Air/Oxygen schedule, breathing oxygen
continuously. Complete as much of the Air/Oxygen schedule as possible.

4. When no more time is available, bring all chamber occupants to the surface (try

not to exceed 10 feet per minute) and keep them on 100 percent oxygen during
evacuation, if possible.

5. Immediately evacuate all chamber occupants to the nearest recompression

facility and treat according to Figure 17‑1. If no symptoms occurred after the
treatment was aborted, follow Treatment Table 6.

17-12

ANCILLARY CARE AND ADJUNCTIVE TREATMENTS

WARNING

Drug therapy shall be administered only after consultation with a Diving
Medical Officer and only by qualified inside tenders adequately trained
and capable of administering prescribed medications.

Most U.S. military diving operations have the unique advantage over most other
diving operations with the ability to provide rapid recompression for the victims of
decompression sickness (DCS) and arterial gas embolism (AGE). When stricken

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U.S. Navy Diving Manual — Volume 5

divers are treated without delay, the success rate of standard recompression therapy
is extremely good.
Some U.S. military divers, such as Special Operations Forces, however, may not
have the benefit of a chamber nearby. Diving missions in Special Operations are
often conducted in remote areas and may entail a lengthy delay to recompression
therapy in the event of a diving accident. Delays to treatment for DCS and AGE
significantly increase the probability of severe or refractory disease. In these
divers, the use of adjunctive therapy (treatments other than recompression on a
treatment table) can be provided while the diver is being transported to a chamber.
Adjunctive therapies may also be useful for divers with severe symptoms or who
have an incomplete response to recompression and hyperbaric oxygen.
Note that the adjunctive therapy guidelines are separated by accident type, with
DCS and AGE covered separately. Although there is some overlap between the
guidelines for these two disorders (as with the recompression phase of therapy),
the best adjunctive therapy for one disorder is not necessarily the best therapy
for the other. Although both DCS and AGE have in common the presence of gas
bubbles in the body and a generally good response to recompression and hyper­
baric oxygen, the underlying pathophysiology is somewhat different.
17-12.1

Decompression Sickness.

17‑12.1.1

Surface Oxygen. Surface oxygen should be used for all cases of DCS until the diver

17‑12.1.2

Fluids. Fluids should be administered to all individuals suffering from DCS unless
suffering from the chokes (pulmonary DCS). Oral fluids (water, Gatorade-like
drinks) are acceptable if the diver is fully conscious, able to tolerate them. If oral
fluids cannot be tolerated by the patient, intravenous fluids should be administered.
There is no data available that demonstrates a superiority of crystalloids (normal
saline or Lactated Ringers solution) over colloids (such as Hetastarch compounds
(Hespan or Hextend)) for DCS, but D5W (dextrose in water without electro­lytes)
should not be used. Since colloids are far more expensive than Lactated Ringers
or normal saline, the latter two agents are the most reasonable choices at this time.
The optimal amount of crystalloids/colloids is likewise not well-estab­lished but
treatment should be directed towards reversing any dehydration that may have
been induced by the dive (immersion diuresis causes divers to lose 250-500 cc of
fluids per hour) or fluid shifts resulting from the DCS. Fluid overloading should be
avoided. Urinary output, in the range of 0.5-1.0cc/kg/hour is evidence of adequate
intravascular volume.

can be recom­pressed. Use of either a high-flow (15 liters/minute) oxygen source
with a reservoir mask or a demand valve can achieve high inspired fractions of
oxygen. One consideration in administering surface oxygen is pulmonary oxygen
toxicity. 100% oxygen can generally be tolerated for up to 12 hours. The patient
may be given air breaks as necessary. If oxygen is being administered beyond this
time, the decision to continue must weigh the perceived benefits against the risk of
pulmonary oxygen toxicity. This risk evaluation must consider the dose of oxygen
anticipated with subsequent recompression therapy as well.

CHAPTER 17 — Diagnosis and Treatment of Decompression Sickness and Arterial Gas Embolism

17-33

Chokes (pulmonary DCS) causes abnormal pulmonary function and leakage of
fluids into the alveolar spaces. Aggressive fluid therapy may make this condition
worse. Consult a DMO (or NEDU) for guidance.
17‑12.1.3

Anticoagulants. Since some types of DCS may increase the likelihood of
hemorrhage into the tissues, anticoagulants should not be used routinely in the
treatment of DCS. One exception to this rule is the case of lower extremity
weakness. Low molecular weight heparin (LMWH) should be used for all patients
with inability to walk due to any degree of lower extremity paralysis caused by
neurological DCS or AGE. Enoxaparin 30 mg, or its equivalent, administered
subcutaneously every 12 hours, should be started as soon as possible after injury to
reduce the risk of deep venous thrombosis (DVT) and pulmonary embolism in any
paralyzed patients. Compression stock­ings or intermittent pneumatic compression
are alternatives, although they are less effective at preventing DVT than LMWH.

17‑12.1.4

Aspirin and Other Non-Steroidal Anti-Inflammatory Drugs. Routine use of anti-

17‑12.1.5

Steroids. Steroids are no longer recommended for the treatment of DCS. No

significant reduction in neurological residuals has been found in clinical studies
for DCS adjunctively treated with steroids and elevated blood glucose levels
associated with steroid administration may actually worsen the outcome of CNS
injury.

17‑12.1.6

Lidocaine. Lidocaine is not currently recommended for the treatment of any type

17‑12.1.7

Environmental Temperature. For patients with evidence of brain or spinal cord

17-12.2

Arterial Gas Embolism.

17‑12.2.1

Surface Oxygen. Surface oxygen should be used for all cases of AGE as it is for

17‑12.2.2

17-34

platelet agents in patients with neurological DCS is not recom­mended, due to
concern about worsening hemorrhage in spinal cord or inner ear decompression
illness. Use of these agents may also be risky in combat divers who may be
required to return to action after treatment of an episode of DCS.

of DCS.

damage, the current evidence recommends aggressive treatment of elevated body
temperature. When treating victims of neurological DCS, whenever practical, hot
environments that may cause elevation of body temperature above normal should
be avoided. The patient’s body temperature and vital signs should be monitored
regularly.

DCS.

Lidocaine. Lidocaine has been shown to be potentially beneficial in the treatment

of AGE. Current recommendations suggests a dosing end-point to achieve serum
concentrations producing an anti-arrhythmic effect. An intravenous initial dose
of 1 mg/kg followed by a continuous infusion of 2-4 mg/minute, will typically
produce therapeutic serum concentrations. If an intravenous infusion is not
estab­lished, intramuscular administration of 4-5 mg/kg will typically produce a
therapeutic plasma concentration 15 minutes after dosing, lasting for around 90

U.S. Navy Diving Manual — Volume 5

minutes. Doses greater than those noted above may be associated with major side
effects, including paresthesias, ataxia, and seizures. Therefore, Lidocaine should
only be administered under the supervision of a DMO or other qualified physician.
17‑12.2.3

Fluids. The fluid replacement recommendations for the treatment of AGE differ
from those of DCS. Fluid replacement recommendations for AGE differ from DCS
because the CNS injury in AGE may be compli­cated by cerebral edema, which may
be worsened by an increased fluid load, thus causing further injury to the diver. If
fluid replacement is conducted, colloids are probably the best choice due to their
mechanism of action in maintaining intra-vascular volume and minimizing extravascular leakage. Particular care must be taken not to fluid overload the injured
diver suffering from AGE by adjusting IV rates to maintain just an adequate urine
output of 0.5cc/kg/hour. A urinary catheter should be inserted in the unconscious
patient and urinary output measured.

17‑12.2.4

Anticoagulants. Anticoagulants should not be used routinely in the treatment

17‑12.2.5

Aspirin and Other Non-Steroidal Anti-Inflammatory Drugs. Routine use of anti-

of AGE. As noted previously in paragraph 17-12.1.3 on anticoagulants in DCS,
Enoxaparin 30 mg, or its equivalent, should be administered subcutaneously every
12 hours, after initial recompression therapy in patients suffering from paralysis to
prevent deep venous thrombosis (DVT) and pulmonary embolism.

platelet agents in patients with AGE is not recommended.

17‑12.2.6

Steroids. Steroids are no longer recommended for the treatment of AGE. No

17-12.2.7

Environmental Temperature. For patients with evidence of brain or spinal cord

17-12.3

significant reduction in neurologic residual has been shown with adjunctive
treatment with steroids for AGE and elevated blood glucose levels associated with
administration of steroids may worsen the outcome of CNS injury.
damage, the current evidence recommends aggressive treatment of elevated body
temperature. When treating victims of neurological DCS, whenever practical, hot
environments that may cause elevation of body temperature above normal should
be avoided. The patient’s body temperature and vital signs should be monitored
regularly.

Sleeping and Eating. The only time the patient should be kept awake during
recompression treatments is during oxygen breathing periods at depths greater
than 30 feet. Travel between decompression stops on Treatment Table 4, 7, and 8
is not a contra-indication to sleeping. While asleep, vital signs (pulse, respiratory
rate, blood pressure) should be monitored as the patient’s condition dictates. Any
significant change would be reason to arouse the patient and ascertain the cause.

CHAPTER 17 — Diagnosis and Treatment of Decompression Sickness and Arterial Gas Embolism

17-35

Food may be taken by chamber occupants at any time. Adequate fluid intake
should be maintained as discussed in paragraph 17-8.3.1.
17-13

EMERGENCY MEDICAL EQUIPMENT

Every diving activity shall maintain emergency medical equipment that will be
available immediately for use in the event of a diving accident. This equipment is
to be in addition to any medical supplies maintained in a medical treatment facility
and shall be kept in a kit small enough to carry into the chamber, or in a locker in
the immediate vicinity of the chamber.
17-13.1

Primary and Secondary Emergency Kits. Because some sterile items may become

contaminated as a result of a hyperbaric exposure, it is desirable to have a primary
kit for immediate use inside the chamber and a secondary kit from which items
that may become contaminated can be locked into the chamber only as needed.
The primary emergency kit contains diagnostic and therapeutic equipment that is
available immediately when required. This kit shall be inside the chamber during
all treatments. The secondary emergency kit contains equipment and medicine that
does not need to be available immediately, but can be locked-in when required.
This kit shall be stored in the vicinity of the chamber.
The contents of the emergency kits presented here are not meant to be restrictive
but are considered the minimum requirement. Additional items may be added to
suit local medical preferences.

The Primary Emergency Kit is described in Table 17‑8. The Secondary Emergency
Kit is described in Table 17‑9.
17-13.2

CAUTION

17-36

Portable Monitor-Defibrillator. All diving activities/commands shall maintain an
automated external defibrillator (AED), preferably with heart rhythm visualization
capability, from an approved Authorized Medical Allowance List (AMAL). Diving
activities with assigned Diving Medical Officer are recommended to augment with
a fully capable monitor defibrillator.

AED’s are not currently approved for use under pressure (hyperbaric
environment) due to electrical safety concerns.

U.S. Navy Diving Manual — Volume 5

Table 17‑8. Primary Emergency Kit.
Diagnostic Equipment
Stethoscope
Otoscope (Ophthalmoscope optional) and batteries
Sphygmomanometer (aneroid type only, case vented for hyperbaric use)
Reflex Hammer
Tuning Fork
Pinwheel
Tongue depressors
Thermometer/temperature measurement capability (non-mercury type)
Disposable exam gloves
Skin Marker
Pocket Eye Chart (Snellen)
Emergency Treatment Primary Survey Equipment and Medications
Oropharyngeal airways (#4 and #5 Guedel-type or equivalent)
Nasal airways (#32F and #34F latex rubber)
Lidocaine jelly (2%)
Self-Inflating Bag-Valve Mask (Disposable BVM)
Suction apparatus with appropriate suction tips
Tension pneumothorax relief kit with 3.25 inch, large-bore catheter on a needle
Cricothyrotomy kit
Adhesive tape (2 inch waterproof)
Elastic-Wrap bandage for a pressure bandage (2 and 4 inch)
Pressure dressing
Appropriate Combat Tourniquet
Trauma Scissors
Sterile 4X4s
Cravats
NOTE: One Primary Emergency Kit is required per chamber system, e.g. TRCS requires one. Additional
Medical Equipment Authorized for Navy Use (ANU) in a chamber can be found in the Medical Equipment
section of the ANU on the NAVSEA website. Contact the Senior Medical Officer at the Navy Experimental
Diving Unit for any questions regarding specific pieces of medical equipment for use in the chamber.

CHAPTER 17 — Diagnosis and Treatment of Decompression Sickness and Arterial Gas Embolism

17-37

Table 17‑9. Secondary Emergency Kit.
Emergency Treatment Secondary Survey Equipment and Medications
Alternative emergency airway device (recommend intubating laryngeal mask airway disposable LMA
Fastrach™kit, size 4 – 5)
Syringe and sterile water for cuff inflation (10 cc)
Sterile lubricant
Qualitative end-tidal CO2 detector (colorimetric indicator)
Chest tube
BD Bard Parker Heimlich Chest Drain Valve (or other device to provide one-way flow of gas out of
the chest)
#11 knife blade and handle
Sterile gloves (size 6 – 8)
Surgical masks (4)
10% povidone-iodine swabs or wipes
1% lidocaine solution
21 gauge. 1 ½ -inch needles on 5 cc syringes (2)
Curved Kelly forceps
Intravenous Infusion Therapy
Catheter on a needle unit, intravenous (16 and 18 gauge - 4 ea)
Adult interosseous infusion device (IO) for rapid vascular access
Intravenous infusion sets (2 standard drip and 2 micro-drip)
Syringes (5, 10 and 30 cc)
Sterile needles (18, 22 and 25 gauge)
Normal saline (1 liter bag (4))
IV Start Kit (10% Povidone-Iodine swabs or wipes, 2 x 2 gauze sponges, Bioclusive dressing, ¾ -inch
adhesive tape, phlebotomy tourniquet)
Band aids
Sam™ Splint
Miscellaneous
Pulse Oximeter (Nonin 9500/8500 series)
Nasogastric tube
60 cc Toomey Syringe (Optional)
Urinary catheterization set with collection bag (appropriate size (12F–14F) Foley-type sterile
catheters)
Assorted suture material (0-silk with and without curved needles)
Sharps disposable box
Disposable Minor Surgical Tray can substitute for items listed below:
Straight and curved hemostats (2 of each)
Blunt straight surgical scissors
Needle driver
Sterile towels
Sterile gauze pads
NOTE 1: Whenever possible, preloaded syringe injection sets should be obtained to avoid the need
to vent multi-dose vials or prevent implosion of ampules. Sufficient quantities should be
maintained to treat one injured diver.
NOTE 2: One Secondary Emergency Kit is required per chamber system (i.e., TRCS requires one).
NOTE 3: A portable oxygen supply with an E cylinder (approximately 669 liters of oxygen) with a
regulator capable of delivering 12 liters of oxygen per minute by mask/reservoir or 2 liters
by nasal canula is recommended whenever possible in the event the patient needs to be
transported to another facility.

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U.S. Navy Diving Manual — Volume 5

Treatment of Arterial Gas Embolism
or Serious Decompression Sickness

Diagnosis Arterial
Gas Embolism or
Decompression
Sickness

Manage IAW
paragrapgh 17-3.3
Pulse
present?

Consider use of
AED or Defibrillator
and Table 6 in
accordance with
paragraph 17-3.3
(Note 4)

Yes

No

Yes
NOTES:

Compress to 60
feet Commence
oxygen breathing
at 60 feet

1. A Diving Medical Officer shall be
consulted before committing to a
Treatment Table 4 or 7.
2. Treatment Table 6A may be
extended if necessary at 60 and/or
30 feet.

Unchanged
or worsening
severe symptoms
(Note 5)

No

3. Cardiac arrest requires early
defibrillation. For the greatest
chance of resuscitation
consultation with a Diving Medical
Officer is required as soon as
possible (see paragraph 17-3.3).

Complete
Treatment
on Table 6

Yes
Compression on
air to depth of
relief or significant
improvement not to
exceed 165 fsw
Remain at
treatment depth
not to exceed
120 min. total

Complete 30 min
period breathing air
or treatment gas on
Table 6A (Note 7)

Yes

More time
needed at depth of
relief (Note 1)

No
Decompress
on Table 4
to 60 feet

Life threatening
symptoms and
more time needed
at 60 feet
(Note 1)

4. Recompression chamber must be
surfaced to perform defibrillation.
5. Assessment of patient must be
made within 20 minutes. If the
stricken diver remains pulseless
after 20 minutes, termination of
resuscitation may be considered.
6. Additional time may be required
according to paragraph 17-6.6.
7 Enter Treatment Table 6A at depth of
relief or significant improvement.

Decompression
to 60 feet not to
exceed 3 ft/min
Complete Treatment
Table 6A (Note 2)

No

Complete
Table 4
(Note 1)

Yes
Remain at 60 ft
at least 12 hours
(Note 6)

Decompress
on Table 7
(Note 1)

Figure 17-1. Treatment of Arterial Gas Embolism or Serious Decompression Sickness.

CHAPTER 17 — Diagnosis and Treatment of Decompression Sickness and Arterial Gas Embolism

17-39

Treatment of Type I Decompression Sickness

Diagnosis:
Decompression
Sickness Type I
(Note 1)

Complete relief
during first 10 min.
at 60 feet?
(Note 3)

No

Complete
Treatment Table 6
(Note 2)

NOTES:
1. If a complete neurological exam
was not completed before
recompression, treat as a Type II
symptom.
2. Treatment Table 6 may be extended
up to four additional oxygenbreathing periods, two at 30 feet
and/or two at 60 feet.

Yes

3. Diving Supervisor may elect to treat
on Treatment Table 6.

Complete
Treatment
on Table 5
(Note 4)

4. Treatment Table 5 may be extended
two oxygen-breathing periods at 30
fsw.

Figure 17-2. Treatment of Type I Decompression Sickness.

17-13.3

Advanced Cardiac Life Support (ACLS) Drugs and Equipment. All commands
with chambers that participate in the local area bends watch shall maintain those
drugs recommended by the American Heart Association for ACLS. These drugs
need to be in sufficient quantities to support an event requiring Advanced Cardiac
Life Support. These drugs are not required to be in every dive kit when multiple
chambers/kits are present in a single command. In addition, medications for the
treatment of anaphylaxis, which can occur related to marine life envenomation,
including Epinephrine 1:1000 solution, Diphenhydramine IM or PO and
Hydrocortisone Sodium Succinate IV will be maintained in adequate quantities to
treat one patient.

Emergency medical equipment in support of ACLS includes cuffed endotracheal
tubes with adapters (7-8 mm), malleable stylet (approx. 12” in length), laryngoscope
with blades (McIntosh #3 and #4, Miller #2 and #3). Additional mechanical devices

17-40

U.S. Navy Diving Manual — Volume 5

for verification of endotracheal tube placement are also authorized, but not required
(Toomey-type or 50cc catheter tip syringe or equivalent).
NOTE

17-13.4

Some vendors supply pre-packed ACLS kits with automated replenishment
programs (examples of which can be found on the Naval Expeditionary
Combat Command (NECC) AMAL).
Use of Emergency Kits. Unless adequately sealed against increased atmospheric

pressure (i.e., vacuum packed), sterile supplies should be re-sterilized after each
pressure exposure; or, if not exposed, to pressure, the sterile supplies should be
replaced at package expiration date. Drugs shall be replaced when their expiration
date is reached. Not all drug ampules will withstand pressure.

NOTE

Stoppered multi-dose vials with large air volumes may need to be vented
with a needle during pressurization and depressurization and then
discarded.

Both kits should be taken to the recompression chamber or scene of the accident.
Each kit is to contain a list of contents and have a tamper evident seal. Each time
the kit is opened, it shall be inventoried and each item checked for proper working
order and then re-sterilized or replaced as necessary. Unopened kits are inventoried
quarterly. Concise instructions for administrating each drug are to be provided in the
kit along with current American Heart Association Advanced Cardiac Life-Support
Protocols. In untrained hands, many of the items can be dangerous. Remember that
as in all treatments YOUR FIRST DUTY IS TO DO NO HARM.
17-13.4.1

Modification of Emergency Kits. Because the available facilities may differ on
board ship, at land-based diving installations, and at diver training or experimental
units, the responsible Diving Medical Officer or Diving Medical Technician are
authorized to augment the emergency kits to suit the local needs.

CHAPTER 17 — Diagnosis and Treatment of Decompression Sickness and Arterial Gas Embolism

17-41

Treatment of Symptom Recurrence
Recurrence During Treatment

Recurrence Following Treatment

Diagnosis:
Recurrence
During
Treatment

Symptom
onset 60 feet
or deeper?

Diagnosis:
Recurrence
Following
Treatment

Diver on oxygen
compress to
60 feet

No

Treat according
to Fig. 17-1

Yes
Deeper
recompression
needed?
(Note 1)

Complete three
20 min. oxygen
breathing periods
at 60 feet

No

Continue and/or
extend Current
Table

Yes

Symptoms
relieved?

Yes

Decompress
on Table 6

No
Compress
to depth of
relief (165 feet
maximum) with
patient off O2

Remain at depth
:30 min. on air or
treatment gas if
available

More time
needed at
treatment depth?
(Note 1)

Yes
NOTES:
1. A Diving Medical Officer
should be consulted
before committing to a
Treatment Table 4 or 7.
2. Treatment Table 6 may
be extended up to
two additional oxygen
breathing periods at 30
and/or 60 feet.
3. Additional time may be
required according to
paragraph 17-6.6.

No

Enter Treatment
Table 6A at
treatment depth
and decompress
accordingly

Yes
Decompress
to 60 feet
on Table 4

Deeper
recompression
needed?

No
Life
threatening
symptoms or
more time needed
at 60 feet?
(Note 2)

No

Decompress
on Table 6
Extended

Yes
Remain at
60 feet at least
12 hours (Note 1
and Note 3)

Decompress
on Table 7
(Note 1)

Yes
Symptoms
still present &
more time needed
at 60 feet?
(Note 1)

No

Complete
Table 4
(Note 1)

Figure 17-3. Treatment of Symptom Recurrence.

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U.S. Navy Diving Manual — Volume 5

Treatment Table 5
1. Descent rate - 20 ft/min.
2. Ascent rate - Not to exceed 1 ft/min. Do not compensate
for slower ascent rates. Compensate for faster rates by
halting the ascent.
3. Time on oxygen begins on arrival at 60 feet.
4. If oxygen breathing must be interrupted because of CNS
Oxygen Toxicity, allow 15 minutes after the reaction
has entirely subsided and resume schedule at point of
interruption (see paragraph 17-8.10.1.1)

5. Treatment Table may be extended two oxygen-breathing
periods at the 30-foot stop. No air break required
between oxygen-breathing periods or prior to ascent.
6. Tender breathes 100 percent O2 during ascent from the
30-foot stop to the surface. If the tender had a previous
hyperbaric exposure in the previous 18 hours, an
additional 20 minutes of oxygen breathing is required
prior to ascent.

Treatment Table 5 Depth/Time Profile
0

15

30
Depth
(FSW)

Ascent Rate
1 Ft/Min.

45
Descent Rate
20 Ft/Min.

Ascent Rate
1 Ft/Min.

60
3

20

5

20

30

5

20

Time at Depth (minutes)

5

30

Total Elapsed Time:
135 Minutes
2 Hours 15 Minutes
(Not Including Descent Time)

Figure 17-4. Treatment Table 5.

CHAPTER 17 — Diagnosis and Treatment of Decompression Sickness and Arterial Gas Embolism

17-43

Treatment Table 6
1. Descent rate - 20 ft/min.

6. Tender breathes 100 percent O2 during the last 30 min.
at 30 fsw and during ascent to the surface for an
unmodified table or where there has been only a single
extension at 30 or 60 feet. If there has been more than
one extension, the O2 breathing at 30 feet is increased
to 60 minutes. If the tender had a hyperbaric exposure
within the past 18 hours an additional 60-minute O2
period is taken at 30 feet.

2. Ascent rate - Not to exceed 1 ft/min. Do not compensate
for slower ascent rates. Compensate for faster rates by
halting the ascent.
3. Time on oxygen begins on arrival at 60 feet.
4. If oxygen breathing must be interrupted because of CNS
Oxygen Toxicity, allow 15 minutes after the reaction
has entirely subsided and resume schedule at point of
interruption (see paragraph 17-8.10.1.1).
5. Table 6 can be lengthened up to 2 additional 25-minute
periods at 60 feet (20 minutes on oxygen and 5 minutes
on air), or up to 2 additional 75-minute periods at 30 feet
(15 minutes on air and 60 minutes on oxygen), or both.

Treatment Table 6 Depth/Time Profile
0

15
Depth
(fsw)

30
Ascent Rate
1 Ft/Min.

45
Descent Rate
20 Ft/Min.

Ascent Rate
1 Ft/Min.

60
3

20

5

20

5

20

5

30

15

60

Time at Depth (minutes)

15

60

30

Total Elapsed Time:
285 Minutes
4 Hours 45 Minutes
(Not Including Descent Time)

Figure 17-5. Treatment Table 6.

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U.S. Navy Diving Manual — Volume 5

Treatment Table 6A
1. Descent rate - 20 ft/min.

6. Deeper than 60 feet, if treatment gas must be interrupted
because of CNS oxygen toxicity, allow 15 minutes after
the reaction has entirely subsided before resuming
treatment gas. The time off treatment gas is counted
as part of the time at treatment depth. If at 60 feet or
shallower and oxygen breathing must be interrupted
because of CNS oxygen toxicity, allow 15 minutes after
the reaction has entirely subsided and resume schedule
at point of interruption (see paragraph 17-8.10.1.1).

2. Ascent rate - 165 fsw to 60 fsw not to exceed 3 ft/min,
60 fsw and shallower, not to exceed 1 ft/min. Do not
compensate for slower ascent rates. Compensate for
faster rates by halting the ascent.
3. Time at treatment depth does not include compression
time.
4. Table begins with initial compression to depth of 60 fsw.
If initial treatment was at 60 feet, up to 20 minutes may
be spent at 60 feet before compression to 165 fsw.
Contact a Diving Medical Officer.

7. Table 6A can be lengthened up to 2 additional 25-minute
periods at 60 feet (20 minutes on oxygen and 5 minutes
on air), or up to 2 additional 75-minute periods at 30 feet
(60 minutes on oxygen and 15 minutes on air), or both.

5. If a chamber is equipped with a high-O2 treatment gas,
it may be administered at 165 fsw and shallower, not
to exceed 3.0 ata O2 in accordance with paragraph
17-8.9. Treatment gas is administered for 25 minutes
interrupted by 5 minutes of air. Treatment gas is
breathed during ascent from the treatment depth to 60
fsw.

8. Tender breathes 100 percent O2 during the last 60
minutes at 30 fsw and during ascent to the surface
for an unmodified table or where there has been only
a single extension at 30 or 60 fsw. If there has been
more than one extension, the O2 breathing at 30 fsw is
increased to 90 minutes. If the tender had a hyperbaric
exposure within the past 18 hours, an additional 60
minute O2 breathing period is taken at 30 fsw.
9. If significant improvement is not obtained within 30
minutes at 165 feet, consult with a Diving Medical
Officer before switching to Treatment Table 4.

Treatment Table 6A Depth/Time Profile
0

30
Ascent Rate 1 Ft/Min.

Depth
(fsw)

60
Ascent Rate 1 Ft/Min.

Ascent Rate 3 Ft/Min.

Descent Rate
20 Ft/Min.

165
25

5 35 20

5

20

5

20

5

30

15

Time at Depth (minutes)

60

15

60

30

Total Elapsed Time:
350 Minutes
5 Hours 50 Minutes
(Not Including Descent Time)

Figure 17-6. Treatment Table 6A.

CHAPTER 17 — Diagnosis and Treatment of Decompression Sickness and Arterial Gas Embolism

17-45

Treatment Table 4
1. Descent rate - 20 ft/min.

6. If oxygen breathing is interrupted, no compensatory
lengthening of the table is required.

2. Ascent rate - 1 ft/min.
3. Time at 165 feet includes compression.
4. If only air is available, decompress on air. If oxygen is
available, patient begins oxygen breathing upon arrival
at 60 feet with appropriate air breaks. Both tender
and patient breathe oxygen beginning 2 hours before
leaving 30 feet. (see paragraph 17-6.5).
5. Ensure life-support considerations can be met before
committing to a Table 4. (see paragraph 17-8.10.1.1)
Internal chamber temperature should be below 85° F.

7. If switching from Treatment Table 6A or 3 at 165
feet, stay a maximum of 2 hours at 165 feet before
decompressing.
8. If the chamber is equipped with a high-O2 treatment gas,
it may be administered at 165 fsw, not to exceed 3.0
ata O2. Treatment gas is administered for 25 minutes
interrupted by 5 minutes of air.

Treatment Table 4 Depth/Time Profile

Depth
(fsw)

0
10
20
30
40
50
60
80

Patient begins oxygen breathing
at 60 Ft. Both patient and tenders
breathe oxygen beginning 2 hours
before leaving 30 Ft.

100
120
140

Ascent Rate 1 Ft/Min.

Descent Rate
20 Ft/Min.

165
0

:30-2
hrs

:30

:30

:30

25 min 20 min 20 min

6 hrs

:30

20 min 20 min

6 hrs
10 min

Time at Depth

12 hrs
10 min

10 min

2 hrs
10 min 10 min

1 min

Total Elapsed Time:
39 Hours 6 Minutes
(30 Minutes at 165 fsw) to
40 Hours 36 Minutes
(2 Hours at 165 fsw)

Figure 17-7. Treatment Table 4.

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U.S. Navy Diving Manual — Volume 5

Treatment Table 7
1. Table begins upon arrival at 60 feet. Arrival at 60 feet is
accomplished by initial treatment on Table 6, 6A or 4.
If initial treatment has progressed to a depth shallower
than 60 feet, compress to 60 feet at 20 ft/min to begin
Table 7.

5. Decompression starts with a 2-foot upward excursion
from 60 to 58 feet. Decompress with stops every 2 feet
for times shown in profile below. Ascent time between
stops is approximately 30 seconds. Stop time begins
with ascent from deeper to next shallower step. Stop at
4 feet for 4 hours and then ascend to the surface at 1 ft/
min.

2. Maximum duration at 60 feet is unlimited. Remain at
60 feet a minimum of 12 hours unless overriding
circumstances dictate earlier decompression.

6. Ensure chamber life-support requirements can be met
before committing to a Treatment Table 7.

3. Patient begins oxygen breathing periods at 60 feet.
Tender need breathe only chamber atmosphere
throughout. If oxygen breathing is interrupted, no
lengthening of the table is required.

7. A Diving Medical Officer should be consulted before
committing to this treatment table.

4. Minimum chamber O2 concentration is 19 percent.
Maximum CO2 concentration is 1.5 percent SEV (11.4
mmHg). Maximum chamber internal temperature is
85°F (paragraph 17-6.5).

Treatment Table 7 Depth/Time Profile
Ascent Rate
1 Ft/Min.)

0
4

20

Ascent Rate = 1 Ft/Hr
(2 Ft every 120 min.)

Descent Rate
20 Ft/Min.
Ascent Rate = 2 Ft/Hr
(2 Ft every 60 min.)

40
Depth
(fsw)

Ascent Rate = 3 Ft/Hr
(2 Ft every 40 min.)

60

12 hrs minimun
No maximum limit

6 hrs

10 hrs

6

16 hrs

16

4 hrs

32

36

Time at Depth (hours)
Figure 17-8. Treatment Table 7.

CHAPTER 17 — Diagnosis and Treatment of Decompression Sickness and Arterial Gas Embolism

17-47

Treatment Table 8
1. Enter the table at the depth which is exactly equal to or
next greater than the deepest depth attained in the
recompression. The descent rate is as fast as tolerable.

5. While deeper than 165 fsw, a helium-oxygen mixture
with 16-36 percent oxygen may be breathed by mask
to reduce narcosis. A 64/36 helium-oxygen mixture is
the preferred treatment gas. At 165 fsw and shallower,
a HeO2 or N2O2 mix with a ppO2 not to exceed 3.0 ata
may be given to the diver as a treatment gas. At 60 fsw
and shallower, pure oxygen may be given to the divers
as a treatment gas. For all treatment gases (HeO2, N2O2,
and O2), a schedule of 25 minutes on gas and 5 minutes
on chamber air should be followed for a total of four
cycles. Additional oxygen may be given at 60 fsw after
a 2-hour interval of chamber air. See Treatment Table
7 for guidance. If high O2 breathing is interrupted, no
lengthening of the table is required.

2. The maximum time that can be spent at the deepest depth
is shown in the second column. The maximum time
for 225 fsw is 30 minutes; for 165 fsw, 3 hours. For an
asymptomatic diver, the maximum time at depth is 30
minutes for depths exceeding 165 fsw and 2 hours for
depths equal to or shallower than 165 fsw.
3. Decompression is begun with a 2-fsw reduction in pressure
if the depth is an even number. Decompression is begun
with a 3-fsw reduction in pressure if the depth is an odd
number. Subsequent stops are carried out every 2 fsw.
Stop times are given in column three. The stop time
begins when leaving the previous depth. Ascend to the
next stop in approximately 30 seconds.

6. To avoid loss of the chamber seal, ascent may be halted
at 4 fsw and the total remaining stop time of 240 minutes
taken at this depth. Ascend directly to the surface upon
completion of the required time.

4. Stop times apply to all stops within the band up to the
next quoted depth. For example, for ascent from 165
fsw, stops for 12 minutes are made at 162 fsw and at
every two-foot interval to 140 fsw. At 140 fsw, the stop
time becomes 15 minutes. When traveling from 225 fsw,
the 166-foot stop is 5 minutes; the 164-foot stop is 12
minutes. Once begun, decompression is continuous. For
example, when decompressing from 225 feet, ascent is
not halted at 165 fsw for 3 hours. However, ascent may
be halted at 60 fsw and shallower for any desired period
of time.

7. Total ascent time from 225 fsw is 56 hours, 29 minutes. For
a 165-fsw recompression, total ascent time is 53 hours,
52 minutes, and for a 60-fsw recompression, 36 hours, 0
minutes.

Depth (fsw)

Max Time at Initial
Treatment Depth (hours)

2-fsw
Stop Times (minutes)

225

0.5

5

165

3

12

140

5

15

120

8

20

100

11

25

80

15

30

60

Unlimited

40

40

Unlimited

60

20

Unlimited

120

Figure 17-9. Treatment Table 8.

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U.S. Navy Diving Manual — Volume 5

Treatment Table 9
1. Descent rate - 20 ft/min.
2. Ascent rate - 20 ft/min. Rate may be slowed to 1 ft/min
depending upon the patient’s medical condition.
3. Time at 45 feet begins on arrival at 45 feet.
4. If oxygen breathing must be interrupted because of CNS
Oxygen Toxicity, oxygen breathing may be restarted
15 minutes after all symptoms have subsided. Resume
schedule at point of interruption (see paragraph 178.10.1.1).

5. Tender breathes 100 percent O2 during last 15 minutes at
45 feet and during ascent to the surface regardless of
ascent rate used.
6. Patient may breathe air or oxygen during ascent.
7. If patient cannot tolerate oxygen at 45 feet, this table can
be modified to allow a treatment depth of 30 feet. The
oxygen breathing time can be extended to a maximum
of 3 to 4 hours.

Treatment Table 9 Depth/Time Profile
0

15
Depth
(FSW)

30

Ascent rate
20 ft/min

Descent rate
20 ft/min

45

2::15

30

5

30

5

Time at Depth (minutes)

30

2::15

Tota Elapsed
Total
ElapsedTime:
Time:
102:15
102:15
(Not Including
Descent Time)
(Not Including Descent Time)

Figure 17-10. Treatment Table 9.

CHAPTER 17 — Diagnosis and Treatment of Decompression Sickness and Arterial Gas Embolism

17-49

Air Treatment Table 1A
1. Descent rate - 20 ft/min.
2. Ascent rate - 1 ft/min.
3. Time at 100 feet includes time from the surface.

Treatment Table 1A Depth/Time Profile
0
10
20
30
40

Depth
(fsw)

50
60

Descent Rate
20 Ft/Min.

80

Ascent Rate 1 Ft/Min.

100
30

12

30

30

30

60

60

120

0
20

20

10

10

10

10

10

Time at Depth (minutes)

10

Total Elapsed Time:
472 Minutes
7 Hours 52 Minutes

Figure 17-11. Air Treatment Table 1A.

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U.S. Navy Diving Manual — Volume 5

Air Treatment Table 2A
1. Descent rate - 20 ft/min.
2. Ascent rate - 1 ft/min.
3. Time at 165 feet includes time from the surface.

Treatment Table 2A Depth/Time Profile
0
10
20
30
40
50
60
Depth
(fsw)

80
100
120
140
Ascent Rate 1 Ft/Min.

Descent Rate
20 Ft/Min.

165
30

12

12

12

30

12

30

30

120

120

240

0
25

20

20

20

20

10

10

10

10

Time at Depth (minutes)

10

10

Total Elapsed Time:
813 Minutes
13 Hours 33 Minutes

Figure 17-12. Air Treatment Table 2A.

CHAPTER 17 — Diagnosis and Treatment of Decompression Sickness and Arterial Gas Embolism

17-51

Air Treatment Table 3
1. Descent rate - 20 ft/min.
2. Ascent rate - 1 ft/min.
3. Time at 165 feet-includes time from the surface.

Treatment Table 3 Depth/Time Profile
0
10
20
30
40
50
60
Depth
(fsw)

80
100
120
140
Ascent Rate 1 Ft/Min.

Descent Rate
20 Ft/Min.

165
30

12

12

12

30

12

30

30

720

120

120

0
25

20

20

20

20

10

10

10

10

Time at Depth (minutes)

10

10

Total Elapsed Time:
1293 Minutes
21 Hours 33 Minutes

Figure 17-13. Air Treatment Table 3.

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U.S. Navy Diving Manual — Volume 5

CHAPTER 18

Recompression Chamber Operation
18-1

INTRODUCTION
18-1.1

18-1.2

Purpose. This chapter will familiarize personnel with the maintenance and
operational requirements for recompression chambers.
Scope. Recompression chambers are used for the treatment of decompression

sickness and arterial gas embolism, for surface decompression, and for
administering pressure tests to prospective divers. Recompression chambers
equipped for hyperbaric administration of oxygen are also used in medical
facilities for hyperbaric treatment of carbon monoxide poisoning, gas gangrene,
and other diseases. Double-lock chambers are used because they permit personnel
and supplies to enter and leave the chamber during treatment.

18-1.3

Chamber Requirements. The requirements for recompression chamber availability

are covered in Chapter 6 and repeated below in Table 18-1.
Table 18-1. Navy Recompression Chamber Support Levels
RCC Support Level

Definition

Level I

A U.S. Navy certified recompression chamber close enough to the
dive site to support surface decompression with a surface interval of 5
minutes. (Note 1, 2)

Level II

A U.S. Navy certified recompression chamber accessible within one
hour of the casualty. (Note 2)

Level III

A U.S. Navy certified recompression chamber accessible within six
hours of the casualty. (Note 3, 4)

Note 1: The Commanding Officer may authorize an extension of the surface interval to a maximum
of 7 minutes (requirements of paragraph 9-12.6 and 12-5.14 apply)
Note 2: A non-Navy chamber may be used if authorized in writing by the first Flag Officer (FO) in
the chain of command, and must include a NAVSEA 00C hazard analysis.
Note 3: A non-Navy chamber may be used if it is evaluated utilizing the NAVSEA non-Navy
recompression chamber check sheet, and authorized in writing by the Commanding Officer.
Note 4: During extreme circumstances when a chamber cannot be reached within 6 hours the
Commanding Officer (or designated individual) can give authorization to use the nearest
recompression facility.

CHAPTER 18 — Recompression Chamber Operation

18-1

18-2

DESCRIPTION

Most chamber-equipped U.S. Navy units will have one of seven commonly
provided chambers. They are:
1. Double-lock, 200-psig, 425-cubic-foot steel chamber (Figure 18‑1).
2. Recompression Chamber Facility: RCF 6500 (Figure 18‑2).
3. Recompression Chamber Facility: RCF 5000 (Figure 18‑3).
4. Double-lock, 100-psig, 202-cubic-foot steel chamber (ARS 50 class and Mod­

ernized) (Figure 18‑4 and Figure 18‑5).

5. Standard Navy Double Lock Recompression Chamber System (SNDLRCS)

(Figure 18‑6).

6. Transportable Recompression Chamber System (TRCS) (Figure 18‑7, Figure

18‑8, Figure 18‑9).

7. Fly-Away Recompression Chamber (FARCC) (Figure 18‑10, Figure 18‑11,

Figure 18‑12).

Select U.S. Navy units have a unique treatment option called the Emergency Evac­
uation Hyperbaric Stretcher (EEHS). The EEHS has a single lock and allows a
patient to be administered oxygen at 60 feet while in transport to a recompression
chamber. However, it does not provide hands-on access to the patient and there­fore
does not qualify as a recompression chamber.
18-2.1

Basic Chamber Components. The basic components of a recompression chamber

are much the same from one model to another. The basic components consist of
the pressure vessel itself, an air supply and exhaust system, a pressure gauge, and
a built-in breathing system (BIBS) to supply oxygen to the patient. Additional
components may include oxygen, carbon dioxide, temperature and humidity
monitors, carbon dioxide scrubbers, additional BIBS systems for air and treatment
gases other than oxygen, a BIBS overboard dump system, and a heating/cooling
system. Collectively these systems must be able to impose and maintain a pressure
equivalent to a depth of 165 fsw (6 ata) on the diver. Double-lock chambers are
used because they permit tending personnel and supplies to enter and leave the
chamber during treatment.
The piping and valving on some chambers is arranged to permit control of the
air supply and the exhaust from either the inside or the outside of the chamber.
Controls on the outside must be able to override the inside controls in the event of
a problem inside the chamber. The usual method for providing this dual-control
capability is through the use of two separate systems. The first, consisting of a
supply line and an exhaust line, can only be controlled by valves that are outside
of the chamber. The second air supply/exhaust system has a double set of valves,
one inside and one outside the chamber. This arrangement permits the tender to

18-2

U.S. Navy Diving Manual — Volume 5

regulate descent or ascent from within the chamber, but always subject to final
control by outside personnel.
18-2.2

Fleet Modernized Double-Lock Recompression Chamber. Modernized chambers

(Figure 18-5) have carbon dioxide and oxygen monitors, a CO2 scrubber system,
a Built-In Breathing System (BIBS), and an oxygen dump system which together
reduce the ventilation requirements. These chambers also include a chamber
environment control system that regulates humidity and temperature.

18-2.3

18-2.4

Recompression Chamber Facility (RCF). The RCF series 6500 and 5000 (Figures
18-2 and 18-3) consists of two sizes of standard double lock steel chambers, each
with a medical lock and easy occupant access. The RCF 6500 is capable of treating
up to 12 occupants while the RCF 5000 is capable of treating 7 occupants. The
systems are installed in a facility to support training, surface decompression,
recompression treatment, and medical treatment operations. Each RCF includes
primary and secondary air supplies comprised of compressors, purification,
and storage for chamber pressurization and ventilation along with oxygen, mix
treatment gas, and emergency air supply to the BIBS system. Each RCF has an
atmospheric conditioning system that provides internal atmospheric scrubbing and
monitoring along with temperature and humidity controls for long term treatment,
gas management, and patient comfort. The RCF includes gas supply monitoring,
a fire extinguishing system, ground fault interruption and emergency power.
The RCF 6500 is equipped with a NATO mating flange. Both series have extra
penetrations for auxiliary equipment such as patient treatment monitoring and
hoods.
Standard Navy Double Lock Recompression Chamber System (SNDLRCS).

The SNDLRCS (Figure 18-6) consists of a Standard Navy Double Lock (SNDL)
recompression chamber and a gas supply system housed within an International
Organization for Standards (ISO) container. The system is capable of supporting
surface decompression, medical treatment, and training operations. Air is supplied
to the system using a Air Flask Rack Assembly (AFRA) which is almost identical
to the Air Supply Rack Assembly (ASRA) used in supporting a FADS 3 DLSS.
Oxygen is provided by four (4) cylinders that are secured to the interior bulkhead
of the ISO container. If an external supply of mixed gas is available it can also be
supplied to the chamber BIBS supply.
The SNDL is a 54” diameter, double lock recompression chamber. It is outfitted
with a stretcher, BIBS, gas monitoring systems, lights, and an environmental
conditioning system. The chamber can comfortably accommodate 4 divers in the
inner lock and 3 divers in the outer lock.
The ISO container houses the gas supply systems and the chamber. It also provides a
shelter from environmental elements for the Outside Tenders and Diving Supervisor
to conduct treatments. The container is both heated and air conditioned as required
and also includes a fold-down desktop, a cabinet, lighting, and a vestibule.
18-2.5

Transportable Recompression Chamber System (TRCS). There are three TRCS

Mods.

CHAPTER 18 — Recompression Chamber Operation

18-3

n TRCS Mod 0 (Figure 18-7) consists of two pressure chambers. One is a
conical-shaped chamber (Figure 18-8) called the Transportable Recompression
Chamber (TRC) and the other is a cylindrical shaped vessel (Figure 18-9) called
the Transfer Lock (TL). The two chambers are capable of being connected by
means of a freely rotating NATO female flange coupling (Figure 18-7).
n TRCS Mod 1 consists of just the TRC.
n TRCS Mod 2 is the TRCS Mod 0 which has had the 5000 psi upgrade ECP
installed allowing it to be used with an Air Supply Rack Assembly (ASRA).
The TRCS is supplied with a Compressed Air and Oxygen System (CAOS)
consisting of lightweight air and oxygen racks of high pressure flasks, as well as a
means of reducing oxygen supply pressure. The TRCS Mod 2 can use the TRCS
Mod 0 lightweight air racks rated at 3000 psi or an ASRA rated at 5000 psi. The
chamber is capable of administering oxygen and mixed gas via BIBS.
An ECP upgrade is available for installing a CO2 Scrubber in the TL. A TRCS Mod
0 or Mod 2 without a TL CO2 Scrubber is limited to one patient and one tender.
When a Level I Recompression Chamber is required or Surface Decompression
dives are planned, a TRCS Mod 0 or Mod 2 (with TL CO2 Scrubber installed) can
be used.
When a Level I Recompression Chamber is not required, any of the three TRCS
Mods can be used.
18-2.6

18-2.7

18-2.8

Fly Away Recompression Chamber (FARCC). This chamber system consists of a
60-inch double lock modernized chamber in a 20’ x 8’ x 8’ milvan (Figure 18-10
and Figure 18-11). The Fly Away Recompres­sion Chamber (FARCC) also includes
a life support skid (Figure 18-12). In addition, a stand-alone generator is provided
for remote site power requirements.
Emergency Evacuation Hyperbaric Stretcher (EEHS). The Emergency Evacuation
Hyperbaric Stretcher (EEHS) is a manually-portable single patient hyperbaric tube
to be used to transport a diving or disabled subma­rine casualty from an accident
site to a treatment facility while under pressure. The EEHS does not replace a
recompression chamber, but is used in conjunction with a chamber. The EEHS is
small enough to allow transfer of a patient, under pressure, into or out of many
shore based recompression chambers owned by both the DOD, and civilian
medical organizations.
Standard Features. Recompression chambers must be equipped with a means for

delivering breathing oxygen to the personnel in the chamber. The inner lock should
be provided with connections for demand-type oxygen inhalators. Oxygen can be
furnished through a pressure reducing manifold connected with supply cylinders
outside the chamber.

18‑2.8.1

18-4

Labeling. All lines should be identified and labeled to indicate function, content

and direc­tion of flow. The color coding in Table 18‑2 should be used.

U.S. Navy Diving Manual — Volume 5

18‑2.8.2

18‑2.8.3

Inlet and Exhaust Ports. Optimum chamber ventilation requires separation of the

inlet and exhaust ports within the chamber. Exhaust ports must be provided with a
guard device to prevent accidental injury when they are open.

Pressure Gauges. Chambers must be fitted with appropriate pressure gauges.
These gauges, marked to read in feet of seawater (fsw), must be calibrated or
compared as described in the applicable Planned Maintenance System (PMS) to
ensure accuracy in accor­dance with the instructions in Chapter 4.
Table 18‑2. Recompression Chamber Line Guide.

18‑2.8.4

Function

Designation

Color Code

Helium

HE

Buff

Oxygen

OX

Green

Helium-Oxygen Mix

HE-OX

Buff & Green

Nitrogen

N

Light Gray

Nitrogen Oxygen Mix

N-OX

Light Gray & Green

Exhaust

E

Silver

Air (Low Pressure)

ALP

Black

Air (High Pressure)

AHP

Black

Chilled Water

CW

Blue & White

Hot Water

HW

Red & White

Potable Water

PW

Blue

Fire Fighting Material

FP

Red

Relief Valves. Recompression chambers should be equipped with pressure relief

valves in each manned lock. Chambers that do not have latches (dogs) on the
doors are not required to have a relief valve on the outer lock. The relief valves
shall be set in accordance with PMS. In addition, all chambers shall be equipped
with a gag valve, located between the chamber pressure hull and each relief valve.
This gag valve shall be a quick acting, ball-type valve, sized to be compatible with
the relief valve and its supply piping. The gag valve shall be safety wired in the
open position.

18‑2.8.5

Communications System. Chamber communications are provided through a

18‑2.8.6

Lighting Fixtures. Consideration should be given to installation of a low-level

diver’s intercommunication system, with the dual microphone/speaker unit in
the chamber and the surface unit outside. The communication system should be
arranged so that personnel inside the chamber need not interrupt their activities to
operate the system. The backup communications system may be provided by a set
of standard sound-powered tele­phones. The press-to-talk button on the set inside
the chamber can be taped down, thus keeping the circuit open.
lighting fixture (on a separate circuit), which can be used to relieve the patient
of the heat and glare of the main lights. Emergency lights for both locks and

CHAPTER 18 — Recompression Chamber Operation

18-5

an external control station are mandatory. No electrical equipment, other than
that authorized within the scope of certification or as listed in the NAVSEA
Authorization for Navy Use (ANU) List, is allowed inside the chamber. Because
of the possibility of fire or explosion when working in an oxygen or compressed
air atmosphere, all electrical wiring and equipment used in a chamber shall meet
required specifications.

Double-Lock Steel Recompression Chamber

1.
2.
3.
4.
5.
6.
7.
8.
9.
10.

Inner Lock
Outer Lock
Air Supply – Two-Valve
Air Supply – One-Valve
Main Lock Pressure Equalizing Valve
Exhaust – Two-Valve
Exhaust – One-Valve
Oxygen Manifold
Relief Gag Valve (1 each lock)
Relief Valve – 110 psig

11.
12.
13.
14.
15.
16.
17.
18.
19.
20.

Medical Lock 18-Inch Diameter
View Port – Inner Lock (4)
View Port – Outer Lock (2)
Lights – Inner Lock 40 Watt (4)
Lights – Outer Lock 40 Watt
Transmitter/Receiver
Berth – 2′6″ × 6′6″
Bench
Pressure Gauge – Outside (2 each lock)
Pressure Gauge – Inside (1 each lock)

Original Design Pressure – 200 psig
Original Hydrostatic Test Pressure – 400 psig
Maximum Operating Pressure – 100 psig

Figure 18-1. Double-Lock Steel Recompression Chamber.

18-6

U.S. Navy Diving Manual — Volume 5

Recompression Chamber Facility: RCF 6500

Design Pressure: 110 psig
Length: 21’ 3”
Height: 7’ 6”
Internal Volume (OL): 144 ft3
Door Opening (OL): 30”

Design Temperature: 0-125°F
Diameter: 6’ 6”
Height: 7’ 6”
Internal Volume (IL): 440 ft3
Door Opening (IL): 48”

Viewports: 6 @ 8” diameter Clear Opening (including 1 video port)
Medlock: 18” diameter X 20” long mounted in console with ASME Quick Actuating Enclosure
Mating Flange: NATO per STANAG 1079
Atmospheric Monitoring: Oxygen, Carbon Dioxide, Temperature
Temperature Monitoring: External Heater/Chiller with internal Blower
Scrubber: Magnetically driven, replaceable canister
BIBS: 8 masks in IL, 4 masks in OL, automatic switching with block & bleed for Oxygen/Nitrox or Heliox/Air, overboard
dump, and Oxygen analysis of supply gas
Principal Communications: AC Powered Speaker/Headset w/battery backup
Secondary Communications: Sound Powered Phone
Furnishing: Two 7’ Bunks, One 5’ 6” Bench, One 18” X 18” Bench
Lighting: 4 Lights in IL, 2 Lights in OL
Gas Pressurization Controls: Primary and secondary air
Air Ventilation Controls: Gross vent and fine vent (with flow meter)
Fire Extinguishing System: 2 Hand Held Hoses in IL, 1 in OL

Figure 18‑2. Recompression Chamber Facility: RCF 6500.

CHAPTER 18 — Recompression Chamber Operation

18-7

Recompression Chamber Facility: RCF 5000

Design Pressure: 110 psig
Length: 14’ 8”
Height: 5’ 7”
Internal Volume (OL): 61 ft3
Door Opening (OL): 30”

Design Temperature: 0-125°F
Diameter: 5’
Weight: 9,300 lbs.
Internal Volume (IL): 162 ft3

Viewports: 6 @ 8” diameter Clear Opening (including 1 video port)
Medlock: 18” diameter X 20” long mounted in console with ASME Quick Actuating Enclosure
Mating Flange: NATO per STANAG 1079
Atmospheric Monitoring: Oxygen, Carbon Dioxide, Temperature
Temperature Monitoring: External Heater/Chiller with internal Blower
Scrubber: Magnetically driven, replaceable canister
BIBS: 4 masks in IL, 3 masks in OL, overboard dump, & Oxygen analysis of supply gas
Principal Communications: AC Powered Speaker/Headset w/battery backup
Secondary Communications: Sound Powered Phone
Furnishing: One Bunks, One Bench
Lighting: 2 Lights in IL, 1 Lights in OL
Gas Pressurization Controls: Primary and secondary air
Air Ventilation Controls: Gross vent and fine vent (with flow meter)
Fire Extinguishing System: Hyperbaric extinguisher

Figure 18‑3. Recompression Chamber Facility: RCF 5000.

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U.S. Navy Diving Manual — Volume 5

ARS 50 Class Double-Lock Recompression Chamber

1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.

Inner Lock
Outer Lock
Air Supply Connection
Air Supply – Inner Lock
Air Supply – Outer Lock
Exhaust – Inner Lock
Exhaust – Outer Lock
BIBS Supply – Inner Lock
BIBS Supply – Outer Lock
BIBS Exhaust – Inner Lock
BIBS Exhaust – Outer Lock
Oxygen Analyzer
Communications
Sound-Powered Phones
External Depth Gauges – Inner Lock (2)
External Depth Gauges – Outer Lock (2)
Telethermometer

Design Pressure – 100 psig
Original Hydrostatic Pressure – 150 psig
Principal Locations – ARS-50 Class Salvage Ships

18. Ground Fault Interrupter
19. Pipe Light Assembly
20. Chiller and Scrubber Panel
23. Inner Lock Comm Panel
24. Outer Lock Comm Panel
25. Bunk Main
26. Bunk Extension
27. View Ports – Inner Lock (4)
28. View Ports – Outer Lock (2)
29. Strongback
30. Relief Valve – 100 psig
30A. Gag Valve
31. Pipe Light Controls
32. Chiller/Scrubber Penetrator

Volume
			
			

–
–
–

Inner Lock = 134 cubic feet
Outer Lock = 68 cubic feet
Total = 202 cubic feet

Figure 18‑4. Double-Lock Steel Recompression Chamber.

CHAPTER 18 — Recompression Chamber Operation

18-9

Fleet Modernized Double-Lock Recompression Chamber

1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.

Inner Lock
Outer Lock
Gas Supply – Inner Lock
Gas Supply – Outer Lock
Gas Exhaust
O2 Analyzer
CO2 Analyzer
Inner-Lock Depth Gauges (2)
Outer-Lock Depth Gauges (2)
Communications Panel
Sound-Powered Phone
Pipe Light Control Panel

13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.

Ground Fault Interrupter
View Ports (5)
Flowmeter
Stopwatch/Timer
Telethermometer
CO2 Scrubber
Fire Extinguisher
Chiller/Conditioner Unit
Gag Valve
Relief Valve – 110 psig
BIBS Overboard Dump Regulator – Outer Lock

Figure 18-5. Fleet Modernized Double-Lock Recompression Chamber.

18-10

U.S. Navy Diving Manual — Volume 5

Figure 18-6. Standard Navy Double-Lock Recompression Chamber System.

CHAPTER 18 — Recompression Chamber Operation

18-11

Figure 18-7. Transportable Recompression Chamber System (TRCS).

Height

52″ with wheels, 48″ without wheels

Width

50.7″

Weight

1,268 lbs.

Internal Volume

45 cu. ft.

Door Opening

26″

View Ports

3 @ 6″ dia. Clear Opening

Medical Lock

5.75″ dia. x 11.8″ long

Mating Flange

Male per NATO STANAG 1079

Life Support Scrubber

Air driven, replaceable scrubber, canister
fits in Med Lock

BIBS

2 masks – oxygen and air supply (with
capability for N2O2 or HeO2) – overboard
dump

Design Pressure

110 psig

Atmospheric Monitoring

Oxygen and Carbon Dioxide Analyzer

Design Temperature

0-125°F

Gas Supply

Primary and secondary air and O2

Length

95.7″

Communications

Battery-powered speaker/headset phone

Furnishing

Patient litter, attendants seat

Figure 18‑8. Transportable Recompression Chamber (TRC).

18-12

U.S. Navy Diving Manual — Volume 5

Height

52.9″

Width

54.8″

Weight

1,367 lbs.

Internal Volume

45.5 cu. ft.

Door Opening

2 doors – 26″

View Ports

2 @ 6″ dia. Clear Opening

Mating Flange

Rotating Female per NATO STANAG
1079

Life Support Scrubber

Air-driven, replaceable scrubber,
canister fits in TRC Med Lock

BIBS

2 masks – oxygen and air supply –
overboard dump

Design Pressure

110 psig

Atmospheric Monitoring

Oxygen and Carbon Dioxide Analyzer

Design Temperature

0-125°F

Gas Supply

Primary and secondary air and O2

Length

69.9″

Communications

Sound-powered phone

Figure 18-9. Transfer Lock (TL).

Figure 18-10. Fly Away Recompression Chamber (FARCC).

CHAPTER 18 — Recompression Chamber Operation

18-13

Figure 18-11. Fly Away Recompression Chamber.

Figure 18-12. Fly Away Recompression Chamber Life Support Skid.

18-14

U.S. Navy Diving Manual — Volume 5

18-3

STATE OF READINESS

Since a recompression chamber is emergency equipment, it must be kept in a state
of readiness. The chamber shall be well maintained and equipped with all neces­
sary accessory equipment. A chamber is not to be used as a storage compartment.
The chamber and the air and oxygen supply systems shall be checked prior to
each use with the Predive Checklist and in accordance with PMS instructions. All
diving personnel shall be trained in the operation of the recompression chamber
equipment and should be able to perform any task required during treatment.
18-4

GAS SUPPLY

A recompression chamber system must have a primary and a secondary air supply
system that satisfies Table 18‑3. The purpose of this requirement is to ensure
the recompression chamber system, at a minimum, is capable of conducting a
Treatment Table 6A (TT6A).
18-4.1

Capacity. Either system may consist of air banks and/or a suitable compressor.

The primary air supply system must have sufficient air to pressurize the inner lock
once to 165 fsw and the outer lock twice to 165 fsw and ventilate the chamber as
specified in Table 18-3.

n Primary System Capacity:
=
(5 x Vil) + (10 x Vol) + RV
Cp
Where:
=
minimum capacity of primary system in SCF
Cp
Vil
=
volume of inner lock
Vol =
volume of outer lock
5
=
atmospheres equivalent to 165 fsw
10
=
twice the atmospheres equivalent to 165 fsw
RV =	required ventilation. See paragraph 18-5.4 for Category A and B
ventilation requirements. Not used for Category C, D, and E.
The secondary air supply system must have sufficient air to pressurize the inner and
outer locks once to 165 fsw plus ventilate the chamber as specified in Table 18-3.
n Secondary System Requirement:
=
(5 x Vil) + (5 x Vol) + RV
Cs
Where:
=
minimum capacity of secondary system in SCF
Cs
Vil
=
volume of inner lock
Vol =
volume of outer lock
5
=
atmospheres equivalent to 165 fsw
RV =	required ventilation. For Category A, B, and C, use 4,224 for ventilation
rate of 70.4 scfm for one hour. For Category D and E, calculate air or
NITROX required for two patients and one tender to breathe BIBS
(when not on O2) during one TT6A with maximum extensions.

CHAPTER 18 — Recompression Chamber Operation

18-15

Table 18‑3. Recompression Chamber Air Supply Requirements.
Recompression Chamber
Configuration

Primary Air Requirement

Secondary Air Requirement

CATEGORY A:
No BIBS overboard dump
No CO2 scrubber
No air BIBS
No O2 and CO2 monitor

Sufficient air to press the IL once and the
OL twice to 165 fsw and vent during one
TT6A for one tender and two patients
with maximum extensions.

Sufficient air to press the IL and OL once
to 165 fsw and vent for one hour at 70.4
scfm.

CATEGORY B:
BIBS overboard dump
No CO2 scrubber
No air BIBS
O2 and CO2 monitors

Sufficient air to press the IL once and
the OL twice to 165 fsw and vent for CO2
during one TT6A for one tender and two
patients with maximum extensions.

Sufficient air to press the IL and OL once
to 165 fsw and vent for one hour at 70.4
scfm.

CATEGORY C:
BIBS overboard dump
CO2 scrubber
No air BIBS
O2 and CO2 monitors

Sufficient air to press the IL once and the
OL twice to 165 fsw.

Sufficient air to press the IL and OL once
to 165 fsw and vent for one hour at 70.4
scfm.

CATEGORY D:
BIBS overboard dump
CO2 scrubber
Air BIBS
O2 and CO2 monitor

Sufficient air to press the IL once and the
OL twice to 165 fsw.
(For TRCS, sufficient air to power CO2
scrubbers must be included)

Sufficient air to press the IL and OL once
to 165 fsw and enough air for one tender
and two patients (when not on O2 ) to
breathe air BIBS during one TT6A with
maximum extensions.

CATEGORY E:
BIBS overboard dump
CO2 scrubber
O2 and CO2 monitor
Spare CO2 scrubber
Secondary power supply
NITROX BIBS
No Air BIBS

Sufficient air to press the IL once and the
OL twice to 165 fsw.

Sufficient air to press the IL and OL
once to 165 fsw and enough air/NITROX
for one tender and two patients (when
not on O2 ) to breathe air/NITROX
BIBS during one TT6A with maximum
extensions.

Notes:
1) Additional air source per PSOB will be required for TT4, 7 or 8.
2) For chambers used to conduct Sur “D” sufficient air is required to conduct a TT6A in addition to any planned Sur “D.”
3) The requirement for BIBS overboard dump can also be satisfied with closed circuit BIBS with CO2 scrubbers.

18-16

U.S. Navy Diving Manual — Volume 5

18-5

OPERATION
18-5.1

18-5.2

Predive Checklist. To ensure each item is operational and ready for use, perform
the equipment checks listed in the Recompression Chamber Predive Checklist,
Figure 18-13.
Safety Precautions.

n Do not use oil on any oxygen fitting, air fitting, or piece of equipment.
n Do not allow oxygen supply tanks to be depleted below 100 psig.
n Ensure dogs are in good operating condition and seals are tight.
n Do not leave doors dogged (if applicable) after pressurization.
n Do not allow open flames, smoking materials, or any flammables to be carried
into the chamber.
n Do not permit electrical appliances to be used in the chamber unless listed in
the Authorization for Navy Use (ANU).
n Do not perform unauthorized repairs or modifications on the chamber support
systems.
n Do not permit products in the chamber that may contaminate or off-gas into the
chamber atmosphere.
18-5.3

General Operating Procedures.
1. Ensure completion of Predive Checklist.
2. Diver and tender enter the chamber together.
3. Diver sits in an uncramped position.
4. Tender closes and dogs (if so equipped) the inner lock door.
5. Pressurize the chamber, at the rate and to the depth specified in the appropriate

decompression or recompression table.

6. As soon as a seal is obtained or upon reaching depth, tender releases the dogs

(if so equipped).

7. Ventilate chamber according to specified rates and energize CO2 scrubber and

chamber conditioning system.

8. Ensure proper decompression of all personnel.
9. Ensure completion of Postdive Checklist.

CHAPTER 18 — Recompression Chamber Operation

18-17

RECOMPRESSION CHAMBER PREDIVE CHECKLIST
Equipment

Initials
Chamber

System certified
Cleared of all extraneous equipment
Clear of noxious odors
Doors and seals undamaged, seals lubricated
Pressure gauges calibrated/compared

Air Supply System
Primary and secondary air supply adequate
One-valve supply: Valve closed
Two-valve supply: Outside valve open, inside valve closed, if applicable
Equalization valve closed, if applicable
Supply regulator set at 250 psig or other appropriate pressure
Fittings tight, filters clean, compressors fueled

Exhaust System
One-valve exhaust: Valve closed and calibrated for ventilation
Two-valve exhaust: Outside valve open, inside valve closed, if applicable

Oxygen Supply System
Cylinders full, marked as BREATHING OXYGEN, cylinder valves open
Replacement cylinders on hand
Built in breathing system (BIBS) masks installed and tested
Supply regulator set in accordance with OPs
Fittings tight, gauges calibrated
Oxygen manifold valves closed
BIBS dump functioning

Figure 18-13. Recompression Chamber Predive Checklist (sheet 1 of 2).

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U.S. Navy Diving Manual — Volume 5

RECOMPRESSION CHAMBER PREDIVE CHECKLIST
Equipment

Initials
Electrical System

Lights
Carbon dioxide analyzer calibrated
Oxygen analyzer calibrated
Temperature indicator calibrated
Carbon dioxide scrubber operational
Chamber conditioning unit operational
Direct Current (DC) power supply
Ground Fault Interrupter (GFI)

Communication System
Primary system tested
Secondary system tested

Fire Prevention System
Tank pressurized for chambers with installed fire suppression systems
Combustible material in metal enclosure
Fire-retardant clothing worn by all chamber occupants
Fire-resistant mattresses and blankets in chamber
Means of extinguishing a fire

Miscellaneous
Inside Chamber:

CO2-absorbent canister with fresh absorbent installed
Urinal
Primary medical kit

	Ear protection sound attenuators/ear protectors (1 set per person)
Must have a 1/16” hole drilled to allow for equalization.
Outside Chamber:

Heater/chiller unit

	Stopwatches for recompression treatment time, decompression time,
personnel leaving chamber time, and cumulative time
Fresh CO2 scrubber canister
U.S. Navy Diving Manual, Volume 5
Ventilation bill
Chamber log
Operating Procedures (OPs) and Emergency Procedures (EPs)
Secondary medical kit
Bedpan (to be locked in as required)

Figure 18-13. Recompression Chamber Predive Checklist (sheet 2 of 2).

CHAPTER 18 — Recompression Chamber Operation

18-19

18‑5.3.1

Tender Change-Out. During extensive treatments, medical personnel may prefer

to lock-in to examine the patient and then lock-out, rather than remain inside
throughout the treatment. Inside tenders may tire and need relief.

18‑5.3.2

Lock-In Operations. Personnel entering the chamber go into the outer lock and

18‑5.3.3

Lock-Out Operations. To exit the chamber, the personnel again enter the outer

18‑5.3.4

close and dog the door (if applicable). The outer lock should be pressurized at a
rate controlled by their ability to equalize, but not to exceed 75 feet per minute.
The outside tender shall record the time pressurization begins to determine the
decompression schedule for the occupants when they are ready to leave the
chamber. When the pressure levels in the outer and inner locks are equal, the inside
door (which was undogged at the beginning of the treatment) should open.

lock and the inside tender closes and dogs the inner door (if so equipped). When
ready to ascend, the Diving Supervisor is notified and the required decompression
schedule is selected and executed. Constant communications are maintained with
the inside tender to ensure that a seal has been made on the inner door. Outer lock
depth is controlled throughout decompression by the outside tender.
Gag Valves. The actuating lever of the chamber gag valves shall be maintained in

the open position at all times, during both normal chamber operations and when
the chamber is secured. The gag valves must be closed only in the event of relief
valve failure during chamber operation. Valves are to be lock-wired in the open
position with light wire that can be easily broken when required. A WARNING
plate, bearing the inscription shown below, shall be affixed to the chamber in the
vicinity of each gag valve and shall be readily viewable by operating personnel.
The WARNING plates shall measure approximately 4 inches by 6 inches and read
as follows:
WARNING
The gag valve must remain open at all times.
Close only if relief valve fails.

18-5.4

Ventilation. The basic rules for ventilation are presented below. These rules

permit rapid computation of the cubic feet of air per minute (acfm) required under
different conditions as measured at chamber pressure (the rules are designed
to ensure that the effective concentration of carbon dioxide will not exceed 1.5
percent (11.4 mmHg) and that when oxygen is being used, the percentage of
oxygen in the chamber will not exceed 25 percent).

1. When air is breathed, provide 2 cubic feet per minute (acfm) for each diver at

rest and 4 cubic feet per minute (acfm) for each diver who is not at rest (i.e., a
tender actively taking care of a patient).

2. When oxygen is breathed from the built-in breathing system (BIBS), provide

12.5 acfm for a diver at rest and 25 acfm for a diver who is not at rest. When
these ventilation rates are used, no additional ventilation is required for
personnel breathing air. These ventilation rates apply only to the number of

18-20

U.S. Navy Diving Manual — Volume 5

people breathing oxygen and are used only when no BIBS dump system is
installed.
3. If ventilation must be interrupted for any reason, the time should not exceed

5 minutes in any 30-minute period. When ventilation is resumed, twice the
volume of ventilation should be used for the time of interruption and then the
basic ventilation rate should be used again.

4. If a BIBS dump system or a closed circuit BIBS is used for oxygen breathing,

the ventilation rate for air breathing may be used.

5. If portable or installed oxygen and carbon dioxide monitoring systems are

available, ventilation may be adjusted to maintain the oxygen level below 25
percent by volume and the carbon dioxide level below 1.5 percent surface
equivalent (sev).

18‑5.4.1

WARNING

Chamber Ventilation Bill. Knowing how much air must be used does not solve

the ventilation problem unless there is some way to determine the volume of air
actually being used for ventilation. The standard procedure is to open the exhaust
valve a given number of turns (or fraction of a turn), which will provide a certain
number of cubic feet of ventilation per minute at a specific chamber depth, and to
use the supply valve to maintain a constant chamber depth during the ventilation
period. Determination of valve settings required for different amounts of
ventilation at different depths is accomplished as follows.

This procedure is to be performed with an unmanned chamber to avoid
exposing occupants to unnecessary risks.
1. Mark the valve handle position so that it is possible to determine accurately the

number of turns and fractions of turns.

2. Check the basic ventilation rules above against probable situations to determine

the rates of ventilation at various depths (chamber pressure) that may be needed.
If the air supply is ample, determination of ventilation rates for a few depths
(30, 60, 100, and 165 feet) may be sufficient. It will be convenient to know the
valve settings for rates such as 6, 12.5, 25, or 37.5 cubic feet per minute (acfm).

3. Determine the necessary valve settings for the selected flows and depths by

using a stopwatch and the chamber as a measuring vessel.

a. Calculate how long it will take to change the chamber pressure by 10
feet if the exhaust valve lets air escape at the desired rate close to the
depth in question. Use the following formula.

CHAPTER 18 — Recompression Chamber Operation

18-21

Where:
T
V

= time in seconds for chamber pressure to change 10 feet
= 	internal volume of chamber (or of lock being used for test) in cubic
feet (cf)
R = 	rate of ventilation desired, in cubic feet per minute as measured at
chamber pressure (acfm)
DP = Change in chamber pressure in fsw
D = depth in fsw (gauge)
Example: Determine how long it will take the pressure to drop from 170

to 160 feet in a 425-cubic-foot chamber if the exhaust valve is releasing 6
cubic feet of air per minute (measured at chamber pressure of 165 feet).

1. List values from example:

T
V
R
DP
D

=
=
=
=
=

unknown
425 cf
6 acfm
10 fsw
165 fsw

2. Substitute values and solve to find how long it will take for the pressure

to drop:

b. Increase the empty chamber pressure to 5 feet beyond the depth in
question. Open the exhaust valve and determine how long it takes to
come up 10 feet (for example, if checking for a depth of 165 fsw, take
chamber pressure to 170 feet and clock the time needed to reach 160
feet). Open the valve to different settings until you can determine what
setting will approximate the desired time. Record the setting. Calculate
the times for other rates and depths and determine the settings for these
times in the same way. Make a chart or table of valve setting versus
ventilation rate and prepare a ventilation bill, using this information and
the ventilation rules.
18‑5.4.2

Notes on Chamber Ventilation.

n The basic ventilation rules are not intended to limit ventilation. Generally, if air
is reasonably plentiful, more air than specified should be used for comfort. This
increase is desirable because it also further lowers the concentrations of carbon
dioxide and oxygen.
18-22

U.S. Navy Diving Manual — Volume 5

n There is seldom any danger of having too little oxygen in the chamber. Even
with no ventilation and a high carbon dioxide level, the oxygen present would
be ample for long periods of time.
n These rules assume that there is good circulation of air in the chamber during
ventilation. If circulation is poor, the rules may be inadequate. Locating the
inlet near one end of the chamber and the outlet near the other end improves
ventilation.
n Coming up to the next stop reduces the standard cubic feet of gas in the cham­ber
and proportionally reduces the quantity (scfm) of air required for ventilation.
n Continuous ventilation is the most efficient method of ventilation in terms of
the amount of air required. However, it has the disadvantage of exposing the
divers in the chamber to continuous noise. At the very high ventilation rates
required for oxygen breathing, this noise can reach the level at which hearing
loss becomes a hazard to the divers in the chamber. If high sound levels do
occur, especially during exceptionally high ventilation rates, the chamber
occupants must wear ear protectors (available as a stock item). A small hole
should be drilled into the central cavity of the protector so that they do not pro­
duce a seal which can cause ear squeeze.
n The size of the chamber does not influence the rate (acfm) of air required for
ventilation.
n Increasing depth increases the actual mass of air required for ventilation; but
when the amount of air is expressed in volumes as measured at chamber pres­
sure, increasing depth does not change the number of actual cubic feet (acfm)
required.
n If high-pressure air banks are being used for the chamber supply, pressure
changes in the cylinders can be used to check the amount of ventilation being
provided.
18-6

CHAMBER MAINTENANCE
18-6.1

Postdive Checklist. To ensure equipment receives proper postdive maintenance

and is returned to operational readiness, perform the equipment checks listed in
the Recompression Chamber Postdive Checklist, Figure 18-14.

18-6.2

Scheduled Maintenance. Every USN recompression chamber shall adhere to

PMS requirements and shall be pressure tested when initially installed, at 2-year
intervals thereafter, and after a major overhaul or repair. This test shall adhere to
PMS requirements and shall be conducted in accordance with Figure 18-15. The
completed test form shall be retained until retest is conducted. For a permanently
installed chamber, removing and reinstalling constitutes a major overhaul and
requires a pressure test. For portable chambers such as the TRCS, SNDLRCS,
and FARCC, follow operating procedures after moving the chamber prior to

CHAPTER 18 — Recompression Chamber Operation

18-23

RECOMPRESSION CHAMBER POSTDIVE CHECKLIST
Equipment

Initials
Air Supply

All valves closed
Air banks recharged, gauged, and pressure recorded
Compressors fueled and maintained per technical manual/PMS requirements

View Ports and Doors
View-ports checked for damage; replaced as necessary
Door seals checked, replaced as necessary
Door seals lightly lubricated with approved lubricant
Door dogs and dogging mechanism checked for proper operation and shaft seals for tight­
ness

Chamber
Inside wiped clean with Nonionic Detergent (NID) and warm fresh water
All unnecessary support items removed from chamber
Blankets cleaned and replaced
All flammable material in chamber encased in fire-resistant containers
Primary medical kit restocked as required
Chamber aired out
Outer door closed
CO2 canister packed
Deckplates lifted, area below deckplates cleaned, deckplates reinstalled

Support Items
Stopwatches checked and reset
U.S. Navy Diving Manual, Operating Procedures (OPs), Emergency Procedures (EPs), ven­
tilation bill and pencil available at control desk
Secondary medical kit restocked as required and stowed
Clothing cleaned and stowed
All entries made in chamber log book
Chamber log book stowed

Figure 18-14. Recompression Chamber Postdive Checklist (sheet 1 of 2).

18-24

U.S. Navy Diving Manual — Volume 5

RECOMPRESSION CHAMBER POSTDIVE CHECKLIST
Equipment

Initials
Oxygen Supply

BIBS mask removed, cleaned per current PMS procedures, reinstalled
All valves closed
System bled
Breathing oxygen cylinders fully pressurized
Spare cylinders available
System free of contamination

Exhaust System
One-valve exhaust: valves closed
Two-valve exhaust: inside valves closed
Two-valve exhaust: outside valves opened

Electrical
All circuits checked
Light bulbs replaced as necessary
Pressure-proof housing of lights checked
All power OFF
Wiring checked for fraying

Figure 18-14. Recompression Chamber Postdive Checklist (sheet 2 of 2).

manned use. Chamber relief valves shall be tested in accordance with the Planned
Maintenance System to verify setting. Each tested relief valve shall be tagged
to indicate the valve set pressure, date of test, and testing activity. After every
use or once a month, whichever comes first, the chamber shall receive routine
maintenance in accordance with the Postdive Checklist. At this time, minor repairs
shall be made and used supplies shall be restocked.
18‑6.2.1

Inspections. At the discretion of the activity, but at least once a year, the chamber
shall be inspected, both inside and outside. Any deposits of grease, dust, or other
dirt shall be removed and, on steel chambers, the affected areas repainted.

18‑6.2.2

Corrosion. Corrosion is removed best by hand or by using a scraper, being careful
not to gouge or otherwise damage the base metal. The corroded area and a small
area around it should then be cleaned to remove any remaining paint and/or
corrosion.

18‑6.2.3

Painting Steel Chambers. Steel Chambers shall be painted utilizing original paint

specifications and in accordance with approved NAVSEA or NAVFAC procedures.
The following paints shall be utilized on NAVSEA carbon steel chambers:

CHAPTER 18 — Recompression Chamber Operation

18-25

PRESSURE TEST FOR USN RECOMPRESSION CHAMBERS
NOTE
All U.S. Navy Standard recompression chambers are restricted to a maximum operating
pressure of 100 psig, regardless of design pressure rating.
A pressure test shall be conducted on every USN recompression chamber:
n

When initially installed

n

After repairs/overhaul

n

At two-year intervals at a given location

Performance of the test and the test results are recorded on a standard U.S. Navy Recompres­sion
Chamber Air Pressure and Leak Test form (Figure 18‑15).
The test is conducted as follows:
1.

Pressurize the innermost lock to 100 fsw (45 psig). Using soapy water or an equivalent solution,
leak test all shell penetration fittings, view-ports, dog seals, door dogs (where applicable), valve
connections, pipe joints, and shell weldments.

2.

Mark all leaks. Depressurize the lock and adjust, repair, or replace components as necessary to
eliminate leaks.
a.

View-Port Leaks. Remove the view-port gasket (replace if necessary), wipe clean.
CAUTION
Acrylic view-ports should not be lubricated or come in contact with any
lubricant. Acrylic view-ports should not come in contact with any volatile
detergent or leak detector (non-ionic detergent is to be used for leak test).
When reinstalling view-port, take up retaining ring bolts until the gasket just
compresses evenly about the view-port. Do not overcompress the gasket.

b.

Weldment Leaks. Contact appropriate NAVSEA technical authority for guidance on
corrective action.

3.

Repeat steps 1 and 2 until all the leaks have been eliminated.

4.

Pressurize lock to 225 fsw (100 psig) and hold for 5 minutes.
WARNING
Do not exceed maximum pressure rating for the pressure vessel.

5.

Depressurize the lock to 165 fsw (73.4 psig). Hold for 1 hour. If pressure drops below 145 fsw
(65 psig), locate and mark leaks. Depressurize chamber and repair leaks in accordance with
Step 2 above and repeat this procedure until final pressure is at least 145 fsw (65 psig).

6.

Repeat Steps 1 through 5 leaving the inner door open and outer door closed. Leak test only
those portions of the chamber not previously tested.

Figure 18-15. Pressure Test for USN Recompression Chambers (sheet 1 of 3).

18-26

U.S. Navy Diving Manual — Volume 5

STANDARD U.S. NAVY RECOMPRESSION CHAMBER
AIR PRESSURE AND LEAK TEST
(Sheet 2 of 3)
Ship/Platform/Facility______________________________________________________________
Type of Chamber:
Recompression Chamber Facility - RCF5000
Recompression Chamber Facility - RCF6500
Transportable Recompression Chamber (TRC)
Fly-Away Recompression Chamber (FARCC)

Double-Lock Steel
Standard Navy Double Lock Recompression
Chamber System (SNDLRCS)
Other*___________________________________

NAME PLATE DATA
Manufacturer____________________________________________________________________
Date of Manufacture_______________________________________________________________
Contract/Drawing No.______________________________________________________________
Maximum Working Pressure________________________________________________________
Date of Last Pressure Test__________________________________________________________
Test Conducted by________________________________________________________________
(Name/Rank)

1.

Conduct visual inspection of chamber to determine if ready for test
Chamber Satisfactory ______________ Initials of Test Conductor _______________________
Discrepancies from fully inoperative chamber equipment:
___________________________________________________________________________
___________________________________________________________________________

2

Close inner door lock. With outer lock door open pressure inner lock to 100 fsw (45 psig) and verify
that the following components do not leak:
(Note: If chamber has medical lock, open inner door and close and secure outer door.)
Inner lock leak checks
A.

Shell penetrations and fittings

______________________

B.

View Ports

______________________

C.

Door Seals

______________________

D.

Door Dog Shaft Seals

______________________

E.

Valve Connections and Stems

______________________

F.

Pipe Joints

______________________

G. Shell Welds
3.

Initials of Test Conductor
Satisfactory
Satisfactory
Satisfactory
Satisfactory
Satisfactory
Satisfactory

______________________
Satisfactory

Increase inner lock pressure to 225 fsw (100 psig) and hold for 5 minutes.
Record Test Pressure ______________________ Satisfactory__________________________
(Note: Disregard small leaks at this pressure).

Figure 18-15. Pressure Test for USN Recompression Chambers (sheet 2 of 3).

CHAPTER 18 — Recompression Chamber Operation

18-27

STANDARD U.S. NAVY RECOMPRESSION CHAMBER
AIR PRESSURE AND LEAK TEST
(Sheet 3 of 3)
4.

Depressurize lock slowly to 165 fsw (73.4 psig). Secure all supply and exhaust valves and hold for one hour.
Start Time ____________________________ Pressure 165 fsw
End Time ____________________________ Pressure _________________ fsw
If pressure drops below 145 fsw (65 psig) locate and mark leaks. Depressurize, repair, and retest inner lock.
Inner Lock Pressure drop test passed ________________ Satisfactory    Initials of Test Conductor.

5.

Depressurize inner lock and open inner lock door. Secure in open position. Close outer door and secure.
(Note: If chamber has medical lock, close and secure inner door and open outer door.)

6.

Repeat tests of sections 2, 3, and 4 above when set up in accordance with section 5. Leak test only those
portions of the chamber not tested in sections 2, 3, and 4.

7.

Outer Lock Checks
A.

Shell penetrations and fittings

______________________

B.

View Ports

______________________

C.

Door Seals

______________________

D.

Door Dog Shaft Seals

______________________

E.

Valve Connections and Stems

______________________

F.

Pipe Joints

______________________

G. Shell Welds
8.

Initials of Test Conductor
Satisfactory
Satisfactory
Satisfactory
Satisfactory
Satisfactory
Satisfactory

______________________
Satisfactory

Maximum Chamber Operating Pressure (100 psig) Test (5 minute hold)
Satisfactory __________________________ Initials of Test Conductor

9.

Inner and Outer Lock Chamber Drop Test
Start Time____________________________ Pressure 165 fsw
End Time ____________________________ Pressure _________________ fsw
Inner and outer lock pressure drop test passed satisfactorily _________ Initials of Test Conductor

10. All above tests have been satisfactorily completed.
			

_______________________________________________

			

_______________________________________________

			

_______________________________________________

Test Director

Date

Diving Officer

Date

Commanding Officer

Date

Figure 18-15. Pressure Test for USN Recompression Chambers (sheet 3 of 3).

18-28

U.S. Navy Diving Manual — Volume 5

n Inside:

— Prime coat NSN 8010-01-302-3608.
— Finish coat white NSN 8010-01-302-3606.
n Outside:

— Prime coat NSN 8010-01-302-3608.
— Exterior coats gray NSN 8010-01-302-6838 or white NSN 8010-01302-3606.
For original paint specification on NAVFAC steel chambers refer to the Operation
and Maintenance Support Information (OMSI) documentation delivered with the
system.
18‑6.2.4

Recompression Chamber Paint Process Instruction. Painting shall be kept to an

18‑6.2.5

Stainless Steel Chambers. Stainless steel chamber such as the TRCS and

18‑6.2.6

Fire Hazard Prevention. The greatest single hazard in the use of a recompression

absolute minimum. Only the coats prescribed above are to be applied. Naval Sea
Systems Command will issue a Recompression Chamber Paint Process Instruction
(NAVSEA-00C3-PI-001) on request.

SNDLRCS do not require surfaces painted for corrosion resistance, only for
cosmetic purposes. Naval Sea Systems Command will provide a Stainless Steel
Recompression Chamber Paint Process Instruction on request.

chamber is from explo­sive fire. Fire may spread two to six times faster in a
pressurized chamber than at atmospheric conditions because of the high partial
pressure of oxygen in the chamber atmosphere. The following precautions shall be
taken to minimize fire hazard:
n Maintain the chamber oxygen percentage as close to 21 percent as possible and
never allow oxygen percentage to exceed 25 percent.
n Remove any fittings or equipment that do not conform with the standard
requirements for the electrical system or that are made of flammable materials.
Permit no wooden deck gratings, benches, or shelving in the chamber.
n Use only mattresses designed for hyperbaric chambers. Use Durett Product or
submarine mattress (NSN 7210-00-275-5878 or 5874). Other mattresses may
cause atmospheric contamination. Mattresses should be enclosed in flame­
proof covers. Use 100% cotton sheets and pillow cases. Put no more bedding
in a chamber than is necessary for the comfort of the patient. Never use blan­
kets of wool or synthetic fibers because of the possibility of sparks from static
electricity.

CHAPTER 18 — Recompression Chamber Operation

18-29

n Clothing worn by chamber occupants shall be made of 100% cotton, or a
flame resistant blend of cotton and polyester for chambers equipped with a fire
extinguisher or fixed hand-held or fire suppression system. Diver swim trunks
made of 65% polyester 35% cotton material are acceptable.
n Keep oil and volatile materials out of the chamber. If any have been used,
ensure that the chamber is thoroughly ventilated before pressurization. Do not
put oil on or in any fittings or high-pressure line. If oil is spilled in the cham­
ber or soaked into any chamber surface or equipment, it must be completely
removed. If lubricants are required, use only those approved and listed in Naval
Ships Technical Manual (NSTM) NAVSEA S9086-H7-STM-000, Chapter
262. Regularly inspect and clean air filters and accumulators in the air supply
lines to protect against the introduction of oil or other vapors into the chamber.
Permit no one to wear oily clothing into the chamber.
n Permit no one to carry smoking materials, matches, lighters or any flammable
materials into a chamber. A WARNING sign should be posted outside the
chamber. Example:
WARNING		 Fire/Explosion Hazard. No matches, lighters, electrical appliances,
or flammable materials permitted in chamber.
18‑6.2.6.1

18-7

Fire Extinguishing. All recompression chambers must have a means of

extinguishing a fire in the inte­rior. Examples of fire protection include wetted
towels, a bucket of water, fire extinguisher, hand-held hose system, or suppression/
deluge system. Refer to U.S. Navy General Specification for the Design,
Construction, and Repair of Diving and Hyperbaric Equipment (TS500-AUSPN-010) for specific requirements of fire protection systems. Only fire extin­
guishers listed on the NAVSEA Authorization for Navy Use (ANU) are to be used.

DIVER CANDIDATE PRESSURE TEST

All U.S. Navy diver candidates shall be physically qualified in accordance with
the Manual of the Medical Department, Art. 15-102. Candidates shall also pass a
pressure test before they are eligible for diver training. This test may be conducted
at any Navy certified recompression chamber, provided it is administered by qual­
ified chamber personnel.
18-7.1

Candidate Requirements. The candidate must demonstrate the ability to equalize

pressure in both ears to a depth of 60 fsw. The candidate shall have also passed the
screening physical readi­ness test in accordance with MILPERSMAN 1220-100,
Exhibit 1.
18-7.1.1

18-30

Aviation Duty Personnel. In accordance with the Manual of the Medical

Department, Art. 15-102, Aviation Duty personnel with documented medical
concerns about their ability to safely tolerate barometric changes, may be
evaluated with a modified Diver Candidate Pressure Test, which shall be medically

U.S. Navy Diving Manual — Volume 5

supervised by a UMO. A modified Diver Candidate Pressure Test does not meet
the requirement of a standard Diver Candidate Pressure Test.
18-7.2

Procedure.
1. Candidates shall undergo a diving physical examination by a Navy Medical

Officer in accordance with the Manual of the Medical Department, Art. 15-102,
and be qualified to undergo the test.

n Aviation Duty personnel requiring pressure testing due to medical concerns
do not require a Diving Duty physical examination, as per MANMED, Art.
15-102.
2. The candidates and the tender enter the recompression chamber and are

pressurized to 60 fsw on air, at a rate of 75 fpm or less as tolerated by the
occupants.
n Descent rates for modified Diver Candidate Pressure Tests administered
for Aviation Duty personnel shall be limited to a maximum of 10 fpm. The
UMO may modify the descent rate to best achieve the clinical evaluation
as long as the modifications are more conservative (i.e. slower) than the
standard Diver Candidate Pressure Test.

3. If a candidate cannot complete the descent, the chamber is stopped and the

candidate is placed in the outer lock for return to the surface.

4. Stay at 60 fsw for at least 10 minutes.
5. Ascend to the surface following standard air decompression procedures.
6. All candidates shall remain at the immediate chamber site for a minimum

of 15 minutes and at the test facility for 1 hour. Candidates or tenders who
must return to their command via air travel must proceed in accordance with
paragraph 9‑14.

18‑7.2.1

References.

n Navy Military Personnel Manual, Art. 1220-100
n Manual of the Medical Department, Art. 15-102

CHAPTER 18 — Recompression Chamber Operation

18-31

PAGE LEFT BLANK INTENTIONALLY

18-32

U.S. Navy Diving Manual — Volume 5

APPENDIX 5A

Neurological Examination
5A-1

INTRODUCTION

This appendix provides guidance on evaluating diving accidents prior to treat­ment.
Figure 5A‑1a is a guide aimed at non-medical personnel for recording essential
details and conducting a neurological examination. Copies of this form should
be readily available. While its use is not mandatory, it provides a useful aid for
gathering information.
5A-2

INITIAL ASSESSMENT OF DIVING INJURIES

When using the form in Figure 5A‑1a, the initial assessment must gather the
necessary information for proper evaluation of the accident.
When a diver reports with a medical complaint, a history of the case shall be
compiled. This history should include facts ranging from the dive profile to
progression of the medical problem. If available, review the diver’s Health Record
and completed Diving Chart or Diving Log to aid in the examination. A few key
questions can help determine a preliminary diagnosis and any immediate treat­ment
needed. If the preliminary diagnosis shows the need for immediate recompression,
proceed with recompression. Complete the examination when the patient stabilizes
at treatment depth. Typical questions should include the following:
1. What is the problem/symptom? If the only symptom is pain:
a. Describe the pain:

n Sharp
n Dull
n Throbbing
b.

Is the pain localized, or hard to pinpoint?

2. Has the patient made a dive recently?
3. What was the dive profile?
a. What was the depth of the dive?
b.

What was the bottom time?

c.

What dive rig was used?

d.

What type of work was performed?

e.

Did anything unusual occur during the dive?

APPENDIX 5A — Neurological Examination

5A-1

4. How many dives has the patient made in the last 24 hours?
a. Chart profile(s) of any other dive(s).
5. Were the symptoms first noted before, during, or after the dive? If after the

dive, how long after surfacing?

6. If during the dive, did the patient notice the symptom while descending, on the

bottom, or during ascent?

7. Has the symptom either increased or decreased in intensity since first noticed?
8. Have any additional symptoms developed since the first one?
9. Has the patient ever had a similar symptom?
10. Has the patient ever suffered from decompression sickness or gas embolism in

the past?

a. Describe this symptom in relation to the prior incident if applicable.
11. Does the patient have any concurrent medical conditions that might explain the

symptoms?

To aid in the evaluation, review the diver’s Health Record, including a baseline
neurological examination, if available, and completed Diving Chart or Diving Log,
if they are readily available.
5A-3

NEUROLOGICAL ASSESSMENT

There are various ways to perform a neurological examination. The quickest infor­
mation pertinent to the diving injury is obtained by directing the initial examination
toward the symptomatic areas of the body. These concentrate on the motor, sensory,
and coordination functions. If this examination is normal, the most productive
information is obtained by performing a complete examination of the following:
1. Mental status
2. Coordination
3. Motor
4. Cranial nerves
5. Sensory
6. Deep tendon reflexes

The following procedures are adequate for preliminary examination. Figure 5A‑1a
can be used to record the results of the examination.

5A-2

U.S. Navy Diving Manual — Volume 5

UPPER BODY
Deltoids

L ______ R ______

Latissimus

L ______ R ______

Biceps

L ______ R ______

Triceps

L ______ R ______

Forearms

L ______ R ______

Hand

L ______ R ______

LOWER BODY
HIPS
Flexion

L ______ R ______

Extension

L ______ R ______

Abduction

L ______ R ______

Adduction

L ______ R ______
KNEES

Flexion

L ______ R ______

Extension

L ______ R ______
ANKLES

Ankles
Dorsiflexion
Dorsiflexion
Plantarfl
exion

Plantarflexion
Toes

L ______ R ______

LL ____
R ____
______
R ______
L ____ R ____
TOES
LL ____
R ____
______
R ______

Figure 5A-1a. Neurological Examination Checklist (sheet 1 of 2).

APPENDIX 5A — Neurological Examination

Change A 5A-3

NEUROLOGICAL EXAMINATION CHECKLIST
(Sheet 2 of 2)

REFLEXES

REFLEXES
(Grade:
Normal,
Hypoactive,
Hyperactive,
Absent)
(Grade:
Normal,
Hypoactive,
Hyperactive,
Absent)
Biceps
L
_____________________________
Biceps
L
R
Triceps
R
TricepsL
L _____________________________
Knees
R
Knees L
L _____________________________
Ankles
L
R
Ankles

L _____________________________

R _____________________________
R _____________________________
R _____________________________
R _____________________________

Sensory Examination for Skin Sensation
(Use diagram to record location of sensory abnormalities – numbness, tingling, etc.)
LOCATION

Indicate results
as follows:
Painful
Area
Decreased
Sensation

COMMENTS

Examination Performed by:

Figure 5A-1b. Neurological Examination Checklist (sheet 2 of 2).

5A-4

Change A

U.S. Navy Diving Manual­— Volume 5

5A-3.1

Mental Status. This is best determined when you first see the patient and is

characterized by his alertness, orientation, and thought process. Obtain a good
history, including the dive profile, present symptoms, and how these symptoms
have changed since onset. The patient’s response to this questioning and that
during the neurological examination will give you a great deal of information
about his mental status. It is important to determine if the patient knows the time
and place, and can recognize familiar people and understands what is happening.
Is the patient’s mood appropriate?
Next the examiner may determine if the patient’s memory is intact by questioning
the patient. The questions asked should be reasonable, and you must know the
answer to the questions you ask. Questions such as the following may be helpful:
n What is your commanding officer’s name?
n What did you have for lunch?

Finally, if a problem does arise in the mental status evaluation, the examiner may
choose to assess the patient’s cognitive function more fully. Cognitive function is
an intellectual process by which one becomes aware of, perceives, or compre­hends
ideas and involves all aspects of perception, thinking, reasoning, and remembering.
Some suggested methods of assessing this function are:
n The patient should be asked to remember something. An example would be
“red ball, green tree, and couch.” Inform him that later in the examination you
will ask him to repeat this information.
n The patient should be asked to spell a word, such as “world,” backwards.
n The patient should be asked to count backwards from 100 by sevens.
n The patient should be asked to recall the information he was asked to remember
at the end of the examination.
5A-3.2

Coordination (Cerebellar/Inner Ear Function). A good indicator of muscle

strength and general coordination is to observe how the patient walks. A normal
gait indicates that many muscle groups and general brain functions are normal.
More thorough examination involves testing that concentrates on the brain and
inner ear. In conducting these tests, both sides of the body shall be tested and the
results shall be compared. These tests include:

1. Heel-to-Toe Test. The tandem walk is the standard “drunk driver” test. While

looking straight ahead, the patient must walk a straight line, placing the heel of
one foot directly in front of the toes of the opposite foot. Signs to look for and
consider deficits include:
a.

Does the patient limp?

b.

Does the patient stagger or fall to one side?

APPENDIX 5A — Neurological Examination

5A-5

2. Romberg Test. With eyes closed, the patient stands with feet together and arms

extended to the front, palms up. Note whether the patient can maintain his
balance or if he immediately falls to one side. Some examiners recommend
giving the patient a small shove from either side with the fingertips.

3. Finger-to-Nose Test. The patient stands with eyes closed and head back, arms

extended to the side. Bending the arm at the elbow, the patient touches his nose
with an extended forefinger, alternating arms. An extension of this test is to
have the patient, with eyes open, alternately touch his nose with his fingertip
and then touch the fingertip of the examiner. The examiner will change the
position of his fingertip each time the patient touches his nose. In this version,
speed is not important, but accuracy is.

4. Heel-Shin Slide Test. While standing, the patient touches the heel of one foot

to the knee of the opposite leg, foot pointing forward. While maintaining this
contact, he runs his heel down the shin to the ankle. Each leg should be tested.

5. Rapid Alternating Movement Test. The patient slaps one hand on the palm

of the other, alternating palm up and then palm down. Any exercise requiring
rapidly changing movement, however, will suffice. Again, both sides should be
tested.

5A-3.3

Cranial Nerves. The cranial nerves are the 12 pairs of nerves emerging from the

cranial cavity through various openings in the skull. Beginning with the most
anterior (front) on the brain stem, they are appointed Roman numerals. An isolated
cranial nerve lesion is an unusual finding in decompression sickness or gas
embolism, but defi­cits occasionally occur and you should test for abnormalities.
The cranial nerves must be quickly assessed as follows:

I.

Olfactory. The olfactory nerve, which provides our sense of smell, is usually

not tested.

II. Optic. The optic nerve is for vision. It functions in the recognition of light and

shade and in the perception of objects. This test should be completed one eye at
a time to determine whether the patient can read. Ask the patient if he has any
blurring of vision, loss of vision, spots in the visual field, or peripheral vision
loss (tunnel vision). More detailed testing can be done by standing in front of
the patient and asking him to cover one eye and look straight at you. In a plane
midway between yourself and the patient, slowly bring your fingertip in turn
from above, below, to the right, and to the left of the direction of gaze until the
patient can see it. Compare this with the earliest that you can see it with the
equivalent eye. If a deficit is present, roughly map out the positions of the blind
spots by passing the finger tip across the visual field.

III. Oculomotor, (IV.) Trochlear, (VI.) Abducens. These three nerves control eye

movements. All three nerves can be tested by having the patient’s eyes follow
the examiner’s finger in all four directions (quadrants) and then in towards the
tip of the nose (giving a “crossed-eyed” look). The oculomotor nerve can be

5A-6

U.S. Navy Diving Manual — Volume 5

further tested by shining a light into one eye at a time. In a normal response, the
pupils of both eyes will constrict.
V. Trigeminal. The Trigeminal Nerve governs sensation of the forehead and face

and the clenching of the jaw. It also supplies the muscle of the ear (tensor
tympani) necessary for normal hearing. Sensation is tested by lightly stroking
the forehead, face, and jaw on each side with a finger or wisp of cotton wool.

VII. Facial. The Facial Nerve controls the face muscles. It stimulates the scalp,

forehead, eyelids, muscles of facial expression, cheeks, and jaw. It is tested
by having the patient smile, show his teeth, whistle, wrinkle his forehead, and
close his eyes tightly. The two sides should perform symmetrically. Symmetry
of the nasolabial folds (lines from nose to outside corners of the mouth) should
be observed.

VIII.Acoustic. The Acoustic Nerve controls hearing and balance. Test this nerve by

whispering to the patient, rubbing your fingers together next to the patient’s
ears, or putting a tuning fork near the patient’s ears. Compare this against the
other ear.

IX. Glossopharyngeal. The Glossopharyngeal Nerves transmit sensation from the

upper mouth and throat area. It supplies the sensory component of the gag
reflex and constriction of the pharyngeal wall when saying “aah.” Test this
nerve by touching the back of the patient’s throat with a tongue depressor. This
should cause a gagging response. This nerve is normally not tested.

X. Vagus. The Vagus Nerve has many functions, including control of the roof

of the mouth and vocal cords. The examiner can test this nerve by having the
patient say “aah” while watching for the palate to rise. Note the tone of the
voice; hoarseness may also indicate vagus nerve involvement.

XI. Spinal Accessory. The Spinal Accessory Nerve controls the turning of the

head from side to side and shoulder shrug against resistance. Test this nerve
by having the patient turn his head from side to side. Resistance is provided by
placing one hand against the side of the patient’s head. The examiner should
note that an injury to the nerve on one side will cause an inability to turn the
head to the opposite side or weakness/absence of the shoulder shrug on the
affected side.

XII. Hypoglossal. The Hypoglossal Nerve governs the muscle activity of the

tongue. An injury to one of the hypoglossal nerves causes the tongue to twist to
that side when stuck out of the mouth.

5A-3.4

Motor. A diver with decompression sickness may experience disturbances in the

muscle system. The range of symptoms can be from a mild twitching of a muscle
to weak­ness and paralysis. No matter how slight the abnormality, symptoms
involving the motor system shall be treated.

APPENDIX 5A — Neurological Examination

5A-7

5A‑3.4.1

Extremity Strength. It is common for a diver with decompression illness to

experience muscle weak­ness. Extremity strength testing is divided into two parts:
upper body and lower body. All muscle groups should be tested and compared
with the corresponding group on the other side, as well as with the examiner. Table
5A‑1 describes the extremity strength tests in more detail. Muscle strength is
graded (0-5) as follows:

(0) Paralysis. No motion possible.
(1) Profound Weakness. Flicker or trace of muscle contraction.
(2) Severe Weakness. Able to contract muscle but cannot move joint against

gravity.

(3) Moderate Weakness. Able to overcome the force of gravity but not the

resistance of the examiner.
(4) Mild Weakness. Able to resist slight force of examiner.
(5) Normal. Equal strength bilaterally (both sides) and able to resist examiner.
5A‑3.4.1.1

Upper Extremities. These muscles are tested with resistance provided by the

examiner. The patient should overcome force applied by the examiner that is
tailored to the patient’s strength. Table 5A‑1 describes the extremity strength tests.
The six muscle groups tested in the upper extremity are:

1. Deltoids.
2. Latissimus.
3. Biceps.
4. Triceps.
5. Forearm muscles.
6. Hand muscles.
5A‑3.4.1.2

Lower Extremities. The lower extremity strength is assessed by watching the

patient walk on his heels for a short distance and then on his toes. The patient
should then walk while squat­ting (“duck walk”). These tests adequately assess
lower extremity strength, as well as balance and coordination. If a more detailed
examination of the lower extremity strength is desired, testing should be
accomplished at each joint as in the upper arm.

5A‑3.4.2

Muscle Size. Muscles are visually inspected and felt, while at rest, for size and

consistency. Look for symmetry of posture and of muscle contours and outlines.
Examine for fine muscle twitching.

5A‑3.4.3

5A‑3.4.4

Muscle Tone. Feel the muscles at rest and the resistance to passive movement.
Look and feel for abnormalities in tone such as spasticity, rigidity, or no tone.
Involuntary Movements. Inspection may reveal slow, irregular, and jerky

movements, rapid contractions, tics, or tremors.

5A-3.5

Sensory Function. Common presentations of decompression sickness in a diver

that may indicate spinal cord dysfunction are:

5A-8

U.S. Navy Diving Manual — Volume 5

Table 5A‑1. Extremity Strength Tests.
Test

Procedure

Deltoid Muscles

The patient raises his arm to the side at the shoulder joint. The examiner places a
hand on the patient’s wrist and exerts a downward force that the patient resists.

Latissimus Group

The patient raises his arm to the side. The examiner places a hand on the underside
of the patient’s wrist and resists the patient’s attempt to lower his arm.

Biceps

The patient bends his arm at the elbow, toward his chest. The examiner then grasps
the patient’s wrist and exerts a force to straighten the patient’s arm.

Triceps

The patient bends his arm at the elbow, toward his chest. The examiner then places
his hand on the patient’s forearm and the patient tries to straighten his arm.

Forearm Muscles

The patient makes a fist. The examiner grips the patient’s fist and resists while the
patient tries to bend his wrist upward and downward.

Hand Muscles

•
•

The patient strongly grips the examiner’s extended fingers.
The patient extends his hand with the fingers widespread. The examiner grips
two of the extended fingers with two of his own fingers and tries to squeeze the
patient’s two fingers together, noting the patient’s strength of resistance.

Lower Extremity Strength

•

The patient walks on his heels for a short distance. The patient then turns around
and walks back on his toes.
The patient walks while squatting (duck walk).

•

These tests adequately assesses lower extremity strength as well as balance and
coordination. If a more detailed examination of lower extremity strength is desired,
testing should be accomplished at each joint as in the upper arm.

In the following tests, the patient sits on a solid surface such as a desk, with feet off the floor.
Hip Flexion

The examiner places his hand on the patient’s thigh to resist as the patient tries to
raise his thigh.

Hip Extension

The examiner places his hand on the underside of the patient’s thigh to resist as the
patient tries to lower his thigh.

Hip Abduction

The patients sits as above, with knees together. The examiner places a hand on the
outside of each of the patient’s knees to provide resistance. The patient tries to open
his knees.

Hip Adduction

The patient sits as above, with knees apart. The examiner places a hand on the
inside of each of the patient’s knees to provide resistance. The patient tries to bring
his knees together.

Knee Extension

The examiner places a hand on the patient’s shin to resist as the patient tries to
straighten his leg.

Knee Flexion

The examiner places a hand on the back of the patient’s lower leg to resist as the
patient tries to pull his lower leg to the rear by flexing his knee.

Ankle Dorsiflexion (ability to flex the foot
toward the rear)

The examiner places a hand on top of the patient’s foot to resist as the patient tries to
raise his foot by flexing it at the ankle.

Ankle Plantarflexion (ability to flex the
foot downward)

The examiner places a hand on the bottom of the patient’s foot to resist as the
patient tries to lower his foot by flexing it at the ankle.

Toes

•
•

The patient stands on tiptoes for 15 seconds
The patient flexes his toes with resistance provided by the examiner.

APPENDIX 5A — Neurological Examination

5A-9

n Pain
n Numbness
n Tingling (“pins-and-needles” feeling; also called paresthesia)
5A‑3.5.1

5A‑3.5.2

Sensory Examination. An examination of the patient’s sensory faculties should be
performed. Figures 5A‑2a and 5A-2b show the dermatomal (sensory) areas of skin
sensations that correlate with each spinal cord segment. Note that the dermatomal
areas of the trunk run in a circular pattern around the trunk. The dermatomal areas
in the arms and legs run in a more lengthwise pattern. In a complete examination,
each spinal segment should be checked for loss of sensation.
Sensations. Sensations easily recognized by most normal people are sharp/

dull discrimination (to perceive as separate) and light touch. It is possible to test
pressure, tempera­ture, and vibration in special cases. The likelihood of DCS
affecting only one sense, however, is very small.

5A‑3.5.3

Instruments. An ideal instrument for testing changes in sensation is a sharp object,

such as the Wartenberg pinwheel or a common safety pin. Either of these objects
must applied at intervals. Avoid scratching or penetrating the skin. It is not the
intent of this test to cause pain.

5A‑3.5.4

5A‑3.5.5

Testing the Trunk. Move the pinwheel or other sharp object from the top of the
shoulder slowly down the front of the torso to the groin area. Another method is
to run it down the rear of the torso to just below the buttocks. The patient should
be asked if he feels a sharp point and if he felt it all the time. Test each dermatome
by going down the trunk on each side of the body. Test the neck area in similar
fashion.
Testing Limbs. In testing the limbs, a circular pattern of testing is best. Test each

limb in at least three locations, and note any difference in sensation on each side
of the body. On the arms, circle the arm at the deltoid, just below the elbow, and
at the wrist. In testing the legs, circle the upper thigh, just below the knee, and the
ankle.
5A‑3.5.6

Testing the Hands. The hand is tested by running the sharp object across the back

and palm of the hand and then across the fingertips.
5A‑3.5.7

5A-3.6

5A-10

Marking Abnormalities. If an area of abnormality is found, mark the area as a
reference point in assess­ment. Some examiners use a marking pen to trace the area
of decreased or increased sensation on the patient’s body. During treatment, these
areas are rechecked to determine whether the area is improving. An example of
improve­ment is an area of numbness getting smaller.
Deep Tendon Reflexes. The purpose of the deep tendon reflexes is to determine if
the patient’s response is normal, nonexistent, hypoactive (deficient), or hyperactive
(excessive). The patient’s response should be compared to responses the examiner
has observed before. Notation should be made of whether the responses are equal
bilaterally (both sides) and if the upper and lower reflexes are similar. If any
difference in the reflexes is noticed, the patient should be asked if there is a prior

U.S. Navy Diving Manual — Volume 5

Occipital
C2

C3

Supraclav

C4
T2

Ax.

C5

T4
Intercostals

T6
Post.
Lat.

T8
T2

Post. Cutan.

Radial

T10

Dorsal Cutan.

C6
T1

T12
Musculo. Cutan.
Med Cutan.
S5
Radial

S3
Median

S2

Ulnar

Post. Cutan.

C7
L4

C8

L3

S1
Femoral-Saphenous
L4

L5

Peroneal
Sciatic
Sural
Tibial
Plantars

Med.
Lat.

S1

Figure 5A-2a. Dermatomal Areas Correlated to Spinal Cord Segment (sheet 1 of 2).

APPENDIX 5A — Neurological Examination

5A-11

Cran 5

C2 C3
Superclav.

C4

Ax.
C5

T3
T4

Intercostal
Post Cutan.

T6
T8

(Radial)

T10
C6

Med. Cutan.
T12

L1

Musculo.
Cutan.
S6
Median

C7
L2
Ulnar
C8
L3
Ant. Cutan.
L4

Femoral
L5
Saphenous
Lat. Cutan.
S
Common
Peroneal
Sup. Peroneal
Sural - Tibal

Deep Peroneal

Figure 5A-2b. Dermatomal Areas Correlated to Spinal Cord Segment (sheet 2 of 2).

5A-12

U.S. Navy Diving Manual — Volume 5

medical condition or injury that would cause the difference. Isolated differences
should not be treated, because it is extremely difficult to get symmetrical
responses bilaterally. To get the best response, strike each tendon with an equal,
light force, and with sharp, quick taps. Usually, if a deep tendon reflex is abnormal
due to decompres­sion sickness, there will be other abnormal signs present. Test
the biceps, triceps, knee, and ankle reflexes by striking the tendon as described in
Table 5A-2.
Table 5A‑2. Reflexes.
Test

Procedure

Biceps

The examiner holds the patient’s elbow with the patient’s hand resting on the examiner’s forearm. The
patient’s elbow should be slightly bent and his arm relaxed. The examiner places his thumb on the
patient’s biceps tendon, located in the bend of the patient’s elbow. The examiner taps his thumb with
the percussion hammer, feeling for the patient’s muscle to contract.

Triceps

The examiner supports the patient’s arm at the biceps. The patient’s arm hangs with the elbow bent.
The examiner taps the back of the patient’s arm just above the elbow with the percussion hammer,
feeling for the muscle to contract.

Knee

The patient sits on a table or bench with his feet off the deck. The examiner taps the patient’s knee
just below the kneecap, on the tendon. The examiner looks for the contraction of the quadriceps (thigh
muscle) and movement of the lower leg.

Ankle

The patient sits as above. The examiner places slight pressure on the patient’s toes to stretch the
Achilles’ tendon, feeling for the toes to contract as the Achilles’ tendon shortens (contracts).

APPENDIX 5A — Neurological Examination

5A-13

PAGE LEFT BLANK INTENTIONALLY

5A-14

U.S. Navy Diving Manual — Volume 5

APPENDIX 5B

First Aid

5B-1

INTRODUCTION

This appendix, covering one-man cardiopulmonary resuscitation, control of
bleeding and shock treatment is intended as a quick reference for individuals
trained in first aid and basic life support. Complete descriptions of all basic life
support techniques are available through your local branch of the American Heart
Association. Further information on the control of bleeding and treatment for shock
is in the Hospital Corpsman 3 & 2 Manual, NAVEDTRA 10669-C.
5B-2

CARDIOPULMONARY RESUSCITATION

All divers must be qualified in cardiopulmonary resuscitation (CPR) in accor­dance
with the procedures of the American Heart Association. Periodic recertification
according to current guidelines in basic life support is mandatory for all Navy
divers. Training can be requested through your local medical command or directly
through your local branch of the American Heart Association.
5B-3

CONTROL OF MASSIVE BLEEDING

Massive bleeding must be controlled immediately. If the victim also requires
resuscitation, the two problems must be handled simultaneously. Bleeding may
involve veins or arteries; the urgency and method of treatment will be determined
in part by the type and extent of the bleeding.
5B-3.1

5B-3.2

External Arterial Hemorrhage. Arterial bleeding can usually be identified by bright
red blood, gushing forth in jets or spurts that are synchronous with the pulse. The
first measure used to control external arterial hemorrhage is direct pressure on the
wound.
Direct Pressure. Pressure is best applied with sterile compresses, placed directly

and firmly over the wound. In a crisis, however, almost any material can be used.
If the material used to apply direct pressure soaks through with blood, apply
additional material on top; do not remove the original pressure bandage. Elevating
the extremity also helps to control bleeding. If direct pressure cannot control
bleeding, it should be used in combination with pressure points.

5B-3.3

Pressure Points. Bleeding can often be temporarily controlled by applying hand

pressure to the appropriate pressure point. A pressure point is a place where the
main artery to the injured part lies near the skin surface and over a bone. Apply
pressure at this point with the fingers (digital pressure) or with the heel of the
hand; no first aid mate­rials are required. The object of the pressure is to compress
the artery against the bone, thus shutting off the flow of blood from the heart to the
wound.

APPENDIX 5B — First Aid

5B-1

5B‑3.3.1

Pressure Point Location on Face. There are 11 principal points on each side of

the body where hand or finger pres­sure can be used to stop hemorrhage. These
points are shown in Figure 5B‑1. If bleeding occurs on the face below the level
of the eyes, apply pressure to the point on the mandible. This is shown in Figure
5B‑1(A). To find this pressure point, start at the angle of the jaw and run your
finger forward along the lower edge of the mandible until you feel a small notch.
The pressure point is in this notch.
5B‑3.3.2

5B‑3.3.3

5B‑3.3.4

5B‑3.3.5

Pressure Point Location for Shoulder or Upper Arm. If bleeding is in the shoulder
or in the upper part of the arm, apply pressure with the fingers behind the clavicle.
You can press down against the first rib or forward against the clavicle—either
kind of pressure will stop the bleeding. This pressure point is shown in Figure
5B‑1(B).
Pressure Point Location for Middle Arm and Hand. Bleeding between the middle
of the upper arm and the elbow should be controlled by applying digital pressure
in the inner (body) side of the arm, about halfway between the shoulder and the
elbow. This compresses the artery against the bone of the arm. The application of
pressure at this point is shown in Figure 5B‑1(C). Bleeding from the hand can be
controlled by pressure at the wrist, as shown in Figure 5B‑1(D). If it is possible to
hold the arm up in the air, the bleeding will be relatively easy to stop.
Pressure Point Location for Thigh. Figure 5B‑1(E) shows how to apply digital
pressure in the middle of the groin to control bleeding from the thigh. The artery
at this point lies over a bone and quite close to the surface, so pressure with your
fingers may be sufficient to stop the bleeding.
Pressure Point Location for Foot. Figure 5B‑1(F) shows the proper position

for controlling bleeding from the foot. As in the case of bleeding from the hand,
elevation is helpful in controlling the bleeding.

5B‑3.3.6

Pressure Point Location for Temple or Scalp. If bleeding is in the region of the

temple or the scalp, use your finger to compress the main artery to the temple
against the skull bone at the pressure point just in front of the ear. Figure 5B‑1(G)
shows the proper position.

5B‑3.3.7

Pressure Point Location for Neck. If the neck is bleeding, apply pressure below

the wound, just in front of the promi­nent neck muscle. Press inward and slightly
backward, compressing the main artery of that side of the neck against the bones
of the spinal column. The applica­tion of pressure at this point is shown in Figure
5B‑1(H). Do not apply pressure at this point unless it is absolutely essential, since
there is a great danger of pressing on the windpipe and thus choking the victim.
5B‑3.3.8

5B‑3.3.9

5B-2

Pressure Point Location for Lower Arm. Bleeding from the lower arm can be
controlled by applying pressure at the elbow, as shown in Figure 5B‑1(I).
Pressure Point Location of the Upper Thigh. As mentioned before, bleeding in the
upper part of the thigh can sometimes be controlled by applying digital pressure
in the middle of the groin, as shown in Figure 5B‑1(E). Sometimes, however, it

U.S. Navy Diving Manual — Volume 5

(A)

TEMPORAL A.

FACIAL A.

POSTERIOR FACIAL V.
EXTERNAL
CARTOID A.

(B)

SUPERFICIAL
TEMPORAL A.

(G)

JUGULAR V.

SUBCLAVIN A.

AUXILIARY A.
SUBCLAVIN V.
CEPHALIC V.

COMMON
CARTOID A.

(H)

BASILIC V.
BRACHIAL A.

VENA CAVA

(C)

BRACHIAL A.

ILIAC V.

(I)

RADIAL ULMAR
A.
A.

FEMORAL A.

(D)
FEMORAL V.
ILIAC A.

(J)

GREAT
SAPHENOUS V.

PERONEAL A.

(E)
DORSAL
VENOUS ARCH

POPLITEAL A.

(K)

ANTERIOR
&
POSTERIOR
TIBIAL A.

(F)

Figure 5B‑1. Pressure Points.

APPENDIX 5B — First Aid

5B-3

is more effective to use the pressure point of the upper thigh as shown in Figure
5B‑1(J). If you use this point, apply pressure with the closed fist of one hand and
use the other hand to give additional pressure. The artery at this point is deeply
buried in some of the heaviest muscle of the body, so a great deal of pressure must
be exerted to compress the artery against the bone.
5B‑3.3.10

Pressure Point Location Between Knee and Foot. Bleeding between the knee and

the foot may be controlled by firm pressure at the knee. If pressure at the side
of the knee does not stop the bleeding, hold the front of the knee with one hand
and thrust your fist hard against the artery behind the knee, as shown in Figure
5B‑1(K). If necessary, you can place a folded compress or bandage behind the
knee, bend the leg back and hold it in place by a firm bandage. This is a most
effective way of controlling bleeding, but it is so uncom­fortable for the victim that
it should be used only as a last resort.
5B‑3.3.11

Determining Correct Pressure Point. You should memorize these pressure points

so that you will know immediately which point to use for controlling hemorrhage
from a particular part of the body. Remember, the correct pressure point is that
which is (1) NEAREST THE WOUND and (2) BETWEEN THE WOUND AND
THE MAIN PART OF THE BODY.

5B‑3.3.12

When to Use Pressure Points. It is very tiring to apply digital pressure and it can

seldom be maintained for more than 15 minutes. Pressure points are recommended
for use while direct pressure is being applied to a serious wound by a second
rescuer, or after a compress, bandage, or dressing has been applied to the wound,
since it will slow the flow of blood to the area, thus giving the direct pressure
technique a better chance to stop the hemorrhage. It is also recommended as a
stopgap measure until a pressure dressing or a tourniquet can be applied.

5B-3.4

5B‑3.4.1

5B-4

Tourniquet. A tourniquet is a constricting band that is used to cut off the supply
of blood to an injured limb. Use a tourniquet only if the control of hemorrhage
by other means proves to be difficult or impossible. A tourniquet must always be
applied ABOVE the wound, i.e., towards the trunk, and it must be applied as close
to the wound as practical.
How to Make a Tourniquet. Basically, a tourniquet consists of a pad, a band and
a device for tightening the band so that the blood vessels will be compressed. It
is best to use a pad, compress or similar pressure object, if one is available. It
goes under the band. It must be placed directly over the artery or it will actually
decrease the pressure on the artery and thus allow a greater flow of blood. If a
tourniquet placed over a pressure object does not stop the bleeding, there is a good
chance that the pressure object is in the wrong place. If this occurs, shift the object
around until the tourniquet, when tightened, will control the bleeding. Any long
flat material may be used as the band. It is important that the band be flat: belts,
stockings, flat strips of rubber or neckerchiefs may be used; but rope, wire, string
or very narrow pieces of cloth should not be used because they cut into the flesh.
A short stick may be used to twist the band tightening the tourniquet. Figure 5B‑2
shows how to apply a tourniquet.

U.S. Navy Diving Manual — Volume 5

Figure 5B‑2. Applying a Tourniquet.

5B‑3.4.2

Tightness of Tourniquet. To be effective, a tourniquet must be tight enough to

stop the arterial blood flow to the limb, so be sure to draw the tourniquet tight
enough to stop the bleeding. However, do not make it any tighter than necessary.

5B‑3.4.3

After Bleeding is Under Control. After you have brought the bleeding under

control with the tourniquet, apply a sterile compress or dressing to the wound and
fasten it in position with a bandage.

5B‑3.4.4

Points to Remember. Here are the points to remember about using a tourniquet:
1. Don’t use a tourniquet unless you can’t control the bleeding by any other

means.

2. Don’t use a tourniquet for bleeding from the head, face, neck or trunk. Use it

only on the limbs.

3. Always apply a tourniquet ABOVE THE WOUND and as close to the wound

as possible. As a general rule, do not place a tourniquet below the knee or
elbow except for complete amputations. In certain distal areas of the extremi­
ties, nerves lie close to the skin and may be damaged by the compression.
Furthermore, rarely does one encounter bleeding distal to the knee or elbow
that requires a tourniquet.

4. Be sure you draw the tourniquet tight enough to stop the bleeding, but don’t

make it any tighter than necessary. The pulse beyond the tourniquet should
disappear.

APPENDIX 5B — First Aid

5B-5

5. Don’t loosen a tourniquet after it has been applied. Transport the victim to a

medical facility that can offer proper care.

6. Don’t cover a tourniquet with a dressing. If it is necessary to cover the injured

person in some way, MAKE SURE that all the other people concerned with
the case know about the tourniquet. Using crayon, skin pencil or blood, mark a
large “T” on the victim’s forehead or on a medical tag attached to the wrist.

5B-3.5

External Venous Hemorrhage. Venous hemorrhage is not as dramatic as severe

arterial bleeding, but if left unchecked, it can be equally serious. Venous bleeding
is usually controlled by applying direct pressure on the wound.

5B-3.6

Internal Bleeding. The signs of external bleeding are obvious, but the first aid

team must be alert for the possibility of internal hemorrhage. Victims subjected
to crushing injuries, heavy blows or deep puncture wounds should be observed
carefully for signs of internal bleeding. Signs usually present include:
n
n
n
n
n
5B‑3.6.1

Moist, clammy, pale skin
Feeble and very rapid pulse rate
Lowered blood pressure
Faintness or actual fainting
Blood in stool, urine, or vomitus

Treatment of Internal Bleeding. Internal bleeding can be controlled only by trained

medical personnel and often only under hospital conditions. Efforts in the field are
generally limited to replacing lost blood volume through intravenous infusion of
saline, Ringer’s Lactate, or other fluids, and the administration of oxygen. Rapid
evacuation to a medical facility is essential.

5B-4

SHOCK

Shock may occur with any injury and will certainly be present to some extent with
serious injuries. Shock is caused by a loss of blood flow, resulting in a drop of
blood pressure and decreased circulation. If not treated, this drop in the quantity of
blood flowing to the tissues can have serious permanent effects, including death.
5B-4.1

Signs and Symptoms of Shock. Shock can be recognized from the following

signs and symptoms.
n
n
n
n
n
n
n
n
n

5B-6

Respiration shallow, irregular, labored
Eyes vacant (staring), lackluster, tired-looking
Pupils dilated
Cyanosis (blue lips/fingernails)
Skin pale or ashen gray; wet, clammy, cold
Pulse weak and rapid, or may be normal
Blood pressure drop
Possible retching, vomiting, nausea, hiccups
Thirst

U.S. Navy Diving Manual — Volume 5

5B-4.2

Treatment. Shock must be treated before any other injuries or conditions except

breathing and circulation obstructions and profuse bleeding. Proper treatment
involves caring for the whole patient, not limiting attention to only a few of the
disorders. The following steps must be taken to treat a patient in shock.
1. Ensure adequate breathing. If the patient is breathing, maintain an adequate

airway by tilting the head back properly. If the patient is not breathing, estab­
lish an airway and restore breathing through some method of pulmonary
resuscitation. If both respiration and circulation have stopped, institute car­
diopulmonary resuscitation measures (refer to paragraph 5B‑2).

2. Control bleeding. If the patient has bleeding injuries, use direct pressure points

or a tourniquet, as required (refer to paragraph 5B‑3).

3. Administer oxygen. Remember that an oxygen deficiency will be caused by the

reduced circulation. Administer 100 percent oxygen.

4. Elevate the lower extremities. Since blood flow to the heart and brain may have

been diminished, circulation can be improved by raising the legs slightly. It is
not recommended that the entire body be tilted, since the abdominal organs
pressing against the diaphragm may interfere with respiration. Excep­tions
to the rule of raising the feet are cases of head and chest injuries, when it is
desirable to lower the pressure in the injured parts; in these cases, the upper
part of the body should be elevated slightly. Whenever there is any doubt as to
the best position, lay the patient flat.

5. Avoid rough handling. Handle the patient as little and as gently as possible.

Body motion has a tendency to aggravate shock conditions.

6. Prevent loss of body heat. Keep the patient warm but guard against overheat­

ing, which can aggravate shock. Remember to place a blanket under as well as
on top of the patient, to prevent loss of heat into the ground, boat or ship deck.

7. Keep the patient lying down. A prone position avoids taxing the circulatory

system. However, some patients, such as those with heart disorders, will have
to be transported in a semi-sitting position.

8. Give nothing by mouth.

APPENDIX 5B — First Aid

5B-7

PAGE LEFT BLANK INTENTIONALLY

5B-8

U.S. Navy Diving Manual — Volume 5

APPENDIX 5C

Hazardous Marine Creatures
5C-1

INTRODUCTION
5C-1.1

5C-1.2

Purpose. This appendix provides general information on hazardous marine life
that may be encountered in diving operations.
Scope. It is beyond the scope of this manual to catalog all types of marine life

encounters and potential injury. Planners should consult the recommended
references listed at the end of this appendix for additional information. Local
medical personnel and expert organizations, such as the Divers Alert Network, are
often good sources of information and should be consulted prior to operating in
unfamiliar waters. A full working knowledge of the marine environment will help
to avoid adverse incidents, severe injuries, and lost time.

5C-2

MARINE ANIMALS THAT ATTACK
5C-2.1

Sharks. Shark attacks on humans are infrequent. The annual recorded number

of shark attacks is only 40 to 100 worldwide. Injuries result predominately from
bites. Shark skin is covered with abrasive dentine appendages, called denticles,
which may cause abrasions if a shark “bumps” a human victim.
5C-2.1.1

Shark Pre-Attack Behavior. Pre-attack behavior by most sharks is somewhat

predictable. A shark that is agitated or preparing to attack may swim erratically,
its pectoral fins pointing downward in contrast to the usual flared-out position,
sometimes with humped back and upward snout, and sometimes in circles of
decreasing radius around its prey. An attack may be heralded by unexpected
acceleration or other marked change in behavior, posture, or swim patterns. Sharks
are much faster and more powerful than any human swimmer. All sharks should
be treated with extreme respect and caution (see Figure 5C 1). Attacks tend to
occur upon persons at the surface, particularly if there is commotion.

5C-2.1.2

First Aid and Treatment.
1. Bites may result in significant bleeding and tissue loss. Take immediate action

to control bleeding using large pressure bandages. Cover wounds with layers
of compressive bandages preferably made with gauze, but easily made from
shirts or towels, and held in place by wrapping the wound tightly with gauze,
torn clothing, towels, or sheets. Direct pressure with elevation or sufficient
compression on “pressure points” over major arteries will hopefully control all
but the most serious bleeding. These pressure points are the radial artery pulse
point for the hand; above the elbow under the biceps muscle for the forearm
(brachial artery); and the groin area with deep finger-tip or heel-of-the-hand
pressure for bleeding from the leg (femoral artery). When bleeding cannot be
immediately controlled by direct pressure and elevation or by compressing
pressure points, a tourniquet should be used to save the victim’s life even

APPENDIX 5C — Dangerous Marine Animals

5C-1

Figure 5C-1. Types of Sharks.

though there is the possibility of loss of the limb if the application exceeds a
duration of 2-4 hours. Do not remove the tourniquet. It should be removed only
by a physician in a hospital setting. Loosening a tourniquet prematurely may
cause further shock by allowing recurrent bleeding.
2. Treat for low blood pressure (in the extreme, for shock) by laying the victim

down and elevating his feet.

3. If medical personnel are available, begin intravenous (IV) Ringer’s lactate or

normal saline solution with a large-bore catheter (16 or 18 gauge). If blood
loss has been extensive, several liters should be infused rapidly. The victim’s
color, pulse, and blood pressure should be used as a guide to the volume
of fluid required. Maintain the airway and administer high flow oxygen by
face mask. Do not give fluids by mouth. If the victim’s cardiovascular state
is stable, narcotics may be administered in small incremental doses for pain
relief. Observe closely for evidence of depressed respirations due to the use of
narcotics.

4. Initial stabilization procedures should include attention to the airway, breathing,

and circulation, followed by a complete evaluation of the victim for multiple
traumas.

5. Transport the victim to a medical facility as soon as possible. The goal is to

treat hemorrhage with blood transfusions. Reassure the victim.

6. Should a severed limb be retrieved, wrap it in bandages, moisten with saline,

place in a plastic bag and chill, but do not put the limb in direct contact with
ice. Transport the severed limb with the victim.

5C-2

U.S. Navy Diving Manual — Volume 5

7. Clean and debride wounds as soon as possible in a hospital or other controlled

environment. Since shark teeth are cartilage, not bone, and therefore may not
appear on an X-ray, operative exploration should be performed to locate and
remove dislodged teeth.

8. Perform X-ray evaluation to evaluate bone damage. Severe crush injury may

result in acute renal failure due to myoglobin released from injured muscle.
Monitor closely for kidney function and adjust IV fluid therapy appropriately.

9. Administer tetanus prophylaxis: tetanus toxoid, 0.5 ml intramuscular (IM) and

tetanus immune globulin, 250 to 400 units IM.

10. Culture infected wounds for both aerobes and anaerobes before instituting

broad spectrum antibiotic coverage; infections with Clostridium or Vibrio
species have been reported. Consider administering an antibiotic, such as
ciprofloxacin, for acute shark bite wounds to prevent Vibrio infection.

11. Acute surgical repair and reconstructive surgery may be necessary.
12. In cases of unexplained decrease in mental status or other neurological signs

and symptoms following shark attack while diving, consider arterial gas
embolism or decompression sickness as a possible cause.

5C-2.2

Killer Whales. Killer whales live in all oceans, both tropical and polar. These large

mammals have blunt, rounded snouts and high black dorsal fins (Figure 5C-2).
The jet black head and back contrast sharply with the white underbelly. Usually,
a white patch can be seen behind and above the eye. Killer whales are usually
observed in packs of 3 to 40 animals. They have powerful jaws, great weight,
speed, and interlocking teeth. Because of their speed and carnivorous habits, these
animals should be treated with great respect. There have been no recorded attacks
in the wild upon humans.

Figure 5C-2. Killer Whale.

APPENDIX 5C — Dangerous Marine Animals

5C-3

5C-2.2.1

Prevention. When killer whales are spotted, all diving personnel should

immediately leave the water. Extreme caution should be observed on shore areas,
piers, barges, ice floes, etc., when killer whales are in the area.

5C-2.2.2

First Aid and Treatment. First aid and treatment would follow the same principles

as those used for a shark bites (paragraph 5C-2.1.2).

5C-2.3

Barracuda. More than 20 species of barracuda inhabit tropical and subtropical

waters from Brazil to Florida and the Indo-Pacific oceans from the Red Sea to
the Hawaiian Islands. The barracuda is an elongated fish with prominent jaws and
teeth, silver in color, and with a large head and V-shaped tail (Figure 5C-3). It
may grow up to 10 feet long and is a fast swimmer, capable of striking rapidly and
fiercely. It will follow swimmers but seldom attacks an underwater swimmer. It is
known to attack surface swimmers and limbs dangling in the water, particularly if
they are adorned with shiny metallic objects, such as jewelry. Barracuda wounds
can be distinguished from those of a shark by the bite pattern. A barracuda leaves
straight or V-shaped wounds while those of a shark conform to the shape of the
shark jaws. Life threatening attacks by barracuda are very rare.

Figure 5C-3. Barracuda.
5C-2.3.1

Prevention. Barracuda are attracted by shiny objects, such as metallic fishing

lures. Avoid wearing shiny equipment or jewelry in the water when barracudas
are likely to be present. Avoid carrying speared fish, as barracuda may strike them.
Avoid splashing or dangling limbs in barracuda-infested waters.

5C-2.3.2

First Aid and Treatment. First aid and treatment follow the same principles as

those used for shark bites (paragraph 5C-2.1.2). Injuries are likely to be less severe
than shark bite injuries.
5C-2.4

5C-4

Moray Eels. While some temperate zone species of moray eels are known, they
inhabit primarily tropical and subtropical waters. Moray eels are bottom dwellers
commonly found in holes and crevices or under rocks and coral. They are snakelike in appearance and movement and have tough, leathery skin (Figure 5C-4).
Morays can grow to a length of 10 feet and have copious sharp thin teeth. Moray
eels are extremely territorial and attack frequently when divers reach into crevices
or holes occupied by the animals. They are powerful and vicious biters and may
be difficult to dislodge after a bite is initiated. Bites from moray eels range from

U.S. Navy Diving Manual — Volume 5

multiple small puncture wounds to extensive jagged tears with profuse bleeding if
there has been a struggle. Injuries are usually inflicted on the hands or forearms.

Figure 5C-4. Moray Eel.

5C-2.4.1

Prevention. Extreme care should be used when reaching into holes or crevices.

Avoid provoking or attempting to dislodge an eel from its hole.

5C-2.4.2

First Aid and Treatment. Direct pressure and raising the injured extremity almost

always controls bleeding. Arrange for medical follow-up. Severe hand or facial
injuries should be evaluated immediately by a physician. Treatment is supportive.
Follow principles of wound management and tetanus prophylaxis as in caring for
shark bites. Antibiotic therapy should be instituted early. Immediate specialized
care by a hand surgeon may be necessary for tendon and/or nerve repair of the
hand to prevent permanent loss of function.
5C-2.5

5C-2.5.1

Sea Lions. Sea lions inhabit the Pacific Ocean and are numerous on the west coast
of the United States. They resemble large seals. Sea lions are normally harmless;
however, during the breeding season (October through December) large bull sea
lions are quite defensive and will be aggressive towards divers. Attempts by divers
to handle these animals may result in bites. The bites are similar in configuration
to dog bites and are rarely severe, but may cause unique infections.
Prevention. Divers should avoid these mammals when they are in the water, and at

any time when they are with their offspring.

5C-2.5.2

First Aid and Treatment.
1. Control local bleeding.
2. Clean and debride wound.
3. Administer tetanus prophylaxis as appropriate.

APPENDIX 5C — Dangerous Marine Animals

5C-5

4. Wound infections are common and prophylactic antibiotic therapy is advised.

“Seal finger” refers to an infection with Mycoplasma and is amenable to
treatment with the antibiotic tetracycline.

5C-3

VENOMOUS MARINE ANIMALS
5C-3.1

5C-3.1.1

Venomous Fish (excluding Stonefish, Scorpionfish, and Zebrafish). Identification
of a fish following a sting is not always possible; however, symptoms and effects
of venoms from stinging fishes do not vary greatly. Venomous fish are rarely
aggressive. Contact is usually made by accidentally stepping on or handling the
fish. Dead fish spines may remain toxic (Figure 5C-5). Local symptoms following
a sting are usually severe pain combined with numbness and/or tingling around the
wound. The wound site may become cyanotic with surrounding tissue becoming
pale and swollen. General symptoms may include nausea, vomiting, sweating,
mild fever, respiratory distress and collapse. Pain may seem disproportionately
high for the apparent severity of the injury. Medical personnel should be prepared
for serious anaphylactic reactions from apparently minor stings or envenomations.
Pain is usually diminished by immersion into hot water (see below).
Prevention. Avoid handling venomous fish. Venomous fish are often found in

Figure 5C-5. Weeverfish.

holes or crevices or lying well camouflaged on rocky bottoms. Divers should be
alert for their presence and take care to avoid them.
5C-3.1.2

First Aid and Treatment.
1. Assist the victim to leave the water; watch for fainting.
2. Lay the victim down and reassure him.
3. Observe for signs of shock.
4. Rinse the wound with sterile saline solution or disinfected water. Surgery

may be required to widen the entrance to the puncture wound. Suction is not
effective for removing toxin.

5C-6

U.S. Navy Diving Manual — Volume 5

5. Soak the wound in hot water for 30 to 90 minutes. This usually provides partial

or total pain relief, but may sometimes be ineffective. The water should be as
hot as the victim can tolerate but not hotter than 113ºF (45ºC). Immersion in
water above 113ºF (45ºC) for longer than a brief period may lead to scalding.
Use hot compresses if the wound is on the face. Adding magnesium sulfate
(Epsom salts) or any other additive to the water offers no benefit. Hot water
immersion is a useful technique that may be attempted for any puncture caused
by a marine spine, such as that of the crown of thorns starfish (Acanthaster
planci), the “horns” of the Pacific Lobster, spines of the Pacific Ratfish, and so
forth.

6. Infiltration of the wound with 0.5 percent to 2.0 percent lidocaine without

epinephrine, or another similar local anesthetic agent, is helpful in reducing
pain. Narcotics may also be needed to manage severe pain.

7. Clean and debride the wound. Spines and sheath frequently remain within the

wound. Be sure to remove all remnants of the spines or they may continue to
release venom.

8. Tourniquets or pressure-immobilization are not advised. Use an antiseptic or

antibiotic ointment and sterile dressing. Restrict movement of the extremity
with splints and cravats.

9. Administer tetanus immunization as appropriate.
10. Treat prophylactically with topical antiseptic ointment. If more than a few

hours to treatment will transpire, administer an antibiotic such as ciprofloxacin.

5C-3.2

Highly Toxic Fish (Stonefish, Scorpionfish, and Zebrafish/Lionfish). Stings by

stonefish, scorpionfish, and zebrafish, also known as lionfish, may be quite severe.
While many similarities exist between these fish and the venomous fish mentioned
in the previous section, this separate section has been included because of the
greater toxicity of their venoms and the availability of stonefish antivenin. Local
symptoms are similar to those of other fish-induced envenomations except that they
are generally more severe and may persist for days. With the sting of a stonefish,
pain may be extraordinary and local tissue destruction extensive. Generalized
symptoms are often present and may include respiratory failure and cardiovascular
collapse. These fish are widely distributed in temperate and tropical seas.
Zebrafish/Lionfish are now found in the Gulf of Mexico, Carribean, and Atlantic
Coast of the United States. They are shallow-water bottom dwellers. Stonefish and
scorpionfish are less ornate with ruggose or flattened bodies, sometimes dark and
mottled. They tend to take on the appearance of their surroundings. Zebrafish are
ornate and feathery in appearance with alternating patches of dark and light colors
and stripes (Figure 5C-6).

5C-3.2.1

Prevention. Prevention is the same as for venomous fish (paragraph 5C-3.1.1).

5C-3.2.2

First Aid and Treatment.
1. Provide the same first aid as that given for venomous fish (paragraph 5C-3.1.2).

APPENDIX 5C — Dangerous Marine Animals

5C-7

Figure 5C-6. Highly Toxic Fish.

2. Observe the victim carefully for possible development of life-threatening

complications. The venoms affect many organ systems, including skeletal,
involuntary, and cardiac muscle. This may result in muscular paralysis,
respiratory depression, peripheral vasodilation, shock, cardiac dysrhythmias,
and cardiac arrest.

3. Clean and debride the wound.
4. Stonefish antivenom is available from Commonwealth Serum Laboratories,

Melbourne, Australia (see Reference 1 at end of this appendix for address
and phone number). If antivenom is used, the directions regarding dosage and
sensitivity testing on the accompanying package insert should be followed
and the treating physician must be ready to treat anaphylaxis (severe allergic
reaction). In brief, one or two punctures require 2,000 units (one vial); three to
four punctures, 4,000 units (two vials); and five to six punctures, 6,000 units
(three vials). Antivenin is delivered by slow IV injection while the victim is
closely monitored for anaphylaxis.

5. Institute tetanus prophylaxis, analgesic therapy and antibiotics as described for

other fish stings.

5C-3.3

5C-8

Stingrays. Stingrays are common in all tropical, subtropical, warm, and temperate
regions. They usually favor sheltered water and burrow into sand with only the eyes
and tail exposed. The stingray has a bat-like shape and a long caudal appendage
(“tail”) (Figure 5C-7). Most attacks occur when waders inadvertently step on the
top surface of a ray, causing it to lash out defensively with its tail. The spine(s)

U.S. Navy Diving Manual — Volume 5

is located near the base of the
tail. Wounds are either punctures
or lacerations and are extremely
painful. The wound appears
swollen and pale with a blue rim.
Secondary wound infections are
common. Systemic symptoms
may include fainting, nausea,
vomiting, sweating, respiratory
difficulty, and cardiovascular
collapse.
5C-3.3.1

5C-3.3.2

Figure 5C-7. Stingray.

Prevention. In shallow waters which favor stingray habitation, shuffle feet on the
bottom and probe with a stick to alert the rays and cause them to flee.
First Aid and Treatment.
1. Give the same first aid as that given for venomous fish (paragraph 5C-3.1.2).

No antivenom is available.

2. Institute hot water therapy as described under fish envenomation.
3. Clean and debride the wound. Remove the spine, if necessary by surgical

means. Be sure to remove any remnants of the integumental sheath because it
might continue to release toxin.

4. Observe the victim carefully for possible development of life-threatening

complications. Symptoms can include cardiac dysrhythmias, hypotension,
vomiting, diarrhea, sweating, muscle paralysis, respiratory depression,
and cardiac arrest. Fatalities are quite rare. Intrathoracic or intraabdominal
penetration may lead to organ puncture and/or serious hemorrhage. If the spine
has impaled the victim in the neck or thorax, do not remove it until the victim
has been brought to a facility where bleeding control can be promptly obtained
in the operating room.

5. Institute tetanus immunization, analgesic therapy, and broad-spectrum

antibiotics as described for fish envenomation.

5C-3.4

Coelenterates. Hazardous types of coelenterates include: Portuguese man-of-war,

box jellyfish, sea nettle, sea wasp, sea blubber, sea anemone, and rosy anemone
(Figure 5C-8). Jellyfish vary widely in color (blue, green, pink, red, brown) or
may be transparent. They appear as balloon-like floats with tentacles dangling
down into the water. The most common marine stinging injury is the jellyfish
sting. Jellyfish can come into direct contact with divers in virtually all oceanic
regions worldwide. When this happens, the diver is exposed to potentially tens of
thousands of minute stinging nematocysts in the tentacles. Most jellyfish stings
result only in painful, transient local skin irritation. The box jellyfish and other
similar creatures, and Portuguese man-of-war are among the most dangerous
types. The sea box jellyfish Chironex fleckeri (found in the Indo-Pacific) can

APPENDIX 5C — Dangerous Marine Animals

5C-9

Figure 5C-8. Coelenterates. Hazardous coelenterates include the Portuguese Man-ofWar (left) and the sea wasp (right).

induce death within 10 minutes of a sting by cardiovascular collapse, respiratory
failure, and muscular paralysis. Deaths from Portuguese man-of-war stings, some
of which may be attributed to allergic reactions, have also been reported. Even
though intoxication from ingesting poisonous sea anemones is rare, sea anemones
must not be eaten.
5C-3.4.1

Prevention. Do not handle j e l l y f i s h . B e a c h e d o r apparently dead specimens

may still be able to sting. Even towels or clothing contaminated with
the stinging nematocysts may cause stinging months later.
5C-3.4.2

Avoidance of Tentacles. In some species of jellyfish, tentacles may trail for great

distances horizontally or vertically in the water and are not easily seen by the
diver. Swimmers and divers should avoid close proximity to jellyfish to prevent
contacting their tentacles, especially when near the surface.

5C-3.4.3

Protection Against Jellyfish. Wet suits, body shells, or protective clothing should

be worn when diving in waters where jellyfish are abundant. Petroleum jelly
applied to exposed skin (e.g., around the mouth) helps to prevent stinging, but
caution should be used since petroleum jelly can deteriorate rubber products.
Safe Sea is a commercial product that functions as a combination jellyfish sting
inhibitor and sunscreen.

5C-10

U.S. Navy Diving Manual — Volume 5

5C-3.4.4

First Aid and Treatment. Without rubbing, gently remove any remaining tentacles

that can be grasped using a towel or clothing. For preventing further discharge of
the stinging nematocysts, copiously apply lidocaine or vinegar (3- to 10-percent
solution of acetic acid). Topical isopropyl (rubbing) alcohol is recommended by
some experts as an alternative decontaminant. Vinegar is absolutely advised for a
box jellyfish sting. Hot water immersion (similar to that used for stonefish – see
above – may be beneficial. Methylated spirits or methanol, 100 percent alcohol
and alcohol plus seawater mixtures have not been proven to be of benefit. Indeed,
these compounds may also worsen the immediate pain. Picric acid, human urine,
and fresh water also have been found to either be ineffective or to even discharge
nematocysts and should not be used, except for the hot water therapy noted above.
Rubbing sand is ineffective and may lead to further nematocyst discharge so
should not be used.
5C-3.4.5

Symptomatic Treatment. Symptomatic treatment for the inflammatory response

that occurs from 24 to 72 hours after the initial sting can include topical steroid
therapy (not very effective), anesthetic ointment (lidocaine 2 percent), pramoxine
lotion, and systemic antihistamines and/or analgesics. Benzocaine topical
anesthetic preparations should generally be avoided because they sometimes cause
sensitization that leads to later skin reactions.

5C-3.4.6

Anaphylaxis. Anaphylaxis (a severe allergic reaction) may result from jellyfish

stings. It is treated in standard fashion with injected IM epinephrine (such as
EpiPen) antihistamines, and systemic corticosteroids.

5C-3.4.7

5C-3.5

Antivenin. Antivenom is available to neutralize the effects of the box jellyfish
(Chironex fleckeri). Antivenom may be obtained from Commonwealth Serum
Laboratories, Melbourne, Australia (See Refernce 4 for contact information).
Antivenom is preferentially administered slowly through an IV, with a controlled
infusion technique if possible. IM injection is safe, but should be used only if
the IV method is not feasible. An initial dose of one vial (20,000 units) of sea
wasp antivenin should be used by the IV route and three containers if by the IM
route. Antivenom should be kept refrigerated, not frozen, at 36 to 50º F (2 to
10º C). Allergic reaction to antivenom should be treated with an IM injection of
epinephrine (0.3 cc of 1:1,000 dilution), corticosteroids, and antihistamines. Treat
hypotension (severely low blood pressure) with IV volume expanders and pressor
medication as necessary.
Coral. Coral, a porous, rock-like formation, is usually found in tropical and

subtropical waters. Coral edges may be extremely sharp such that the most
delicate-appearing coral may be the most hazardous because of its razor-sharp
edges. Coral cuts, while usually fairly superficial, take a long time to heal and
can cause temporary disability. The smallest cut, if left untreated, can fester and
develop into a skin ulcer. Infections often occur and may be recognized by the
presence of a red and tender area surrounding the wound. All coral cuts should
receive medical attention. Some varieties of coral can actually sting a diver since
certain structures termed “coral,” such as “fire coral,” are actually coelenterates
with stinging cells.

APPENDIX 5C — Dangerous Marine Animals

5C-11

5C-3.5.1

Prevention. Extreme care should be used when working near coral. Coral is often

located within a reef formation subjected to heavy surface water action, surface
current, and bottom current. Surge sometimes develops in reef areas. For this
reason, it is easy for a diver or surface swimmer to be swept or tumbled across
coral.

5C-3.5.2

Protection Against Coral. Coral should not be handled with bare hands. Feet

should be protected with booties, coral shoes or tennis shoes. Wet suits and
protective clothing, especially gloves (neoprene or heavy work gloves), should be
worn when near coral.
5C-3.5.3

First Aid and Treatment.
1. Control local bleeding.
2. Promptly clean with soap and water, and then with medicinal (dilute) hydrogen

peroxide or 10-percent povidone-iodine solution. If possible, sharply debride
any jagged edges of full thickness skin wound, removing as best possible all
foreign particles.

3. Apply antiseptic ointment, such as bacitracin, and cover with a clean dressing.
4. Administer tetanus immunization as appropriate.
5. Topical antiseptic ointment has been proven very effective in preventing

infection. In severe cases, restrict the victim to bed rest with elevation of the
extremity, wet-to-dry dressings, and systemic antibiotics. Systemic steroids may
be needed to manage the inflammatory reaction resulting from a combination
of trauma and allergic dermatitis. It may be difficult to differentiate infection
from hypersensitivity.

5C-3.6

5C-12

The octopus inhabits
tropical and temperate oceans.
Species vary depending on region.
It is configured as a large head sac
surrounded by 8 to 10 tentacles (Figure
5C-9). The head sac houses welldeveloped eyes, and horny jaws on the
mouth. Movement is made by jet action
produced by expelling water from the
mantle cavity through the siphon. The
octopus will hide in caves, crevices and
shells. It possesses a well-developed
venom apparatus in its salivary glands,
and injures its victim by biting. Most
species of octopus found in the U.S.
are harmless. The blue-ringed octopus
common in Australian and Indo-Pacific Figure 5C-9. Octopus.
waters may inflict fatal bites. The venom of the blue-ringed or spotted octopus
Octopuses.

U.S. Navy Diving Manual — Volume 5

is a neuromuscular blocker called tetrodotoxin, which is also found in pufferfish.
Envenomation from the bite of such an octopus may lead to muscular paralysis,
vomiting, respiratory difficulty, visual disturbances, and cardiovascular collapse.
Octopus bites usually consist of two small punctures. The bite may be painless,
or a burning or tingling sensation may soon spread. Swelling, redness, and
inflammation are common. Local bleeding just after the bite may be brisk because
the clotting ability of the blood is sometimes retarded by the anticoagulant action
of venom.
5C-3.6.1

Prevention. Extreme care should be used when reaching into locations, such as

caves and crevices that are dark or not well visualized. Regardless of size, an
octopus should be handled carefully even while wearing gloves. One should not
spear an octopus, especially the large ones found off the coast of the northwestern
United States, because of the risk of being entangled within its tentacles. If killing
an octopus becomes necessary, stabbing it between the eyes is recommended.

5C-3.6.2

First Aid and Treatment.
1. Control local bleeding.
2. Clean the wound and cover it with a clean dressing.
3. For a suspected blue-ringed octopus bite, apply direct pressure with a pressure

bandage and immobilize the extremity in a position that is lower than the heart
using splints and elastic bandages.

4. Be prepared to administer mouth-to-mouth breathing and cardiopulmonary

resuscitation if necessary.

5. Blue-ringed octopus venom is heat stable and acts as a neurotoxin and

neuromuscular blocking agent. It is not neutralized by hot water therapy. No
antivenom is available.

6. Medical therapy for blue-ringed octopus bites is directed toward management

of paralytic, cardiovascular, and respiratory complications. Respiratory arrest
is common, so endotracheal intubation with mechanical ventilation may be
required. Duration of paralysis is between 4 and 12 hours. Reassure the victim,
who may be comprehending their surroundings even though paralyzed.

7. Administer tetanus immunization as appropriate.
5C-3.7

Segmented Worms (Annelida) (Examples: Bloodworm, Bristleworm). This
invertebrate type varies according to region and is found in warm, tropical or
temperate zones. It is usually found under rocks or coral and is especially common
in the tropical Pacific, Bahamas, Florida Keys, and Gulf of Mexico. Annelida
have long, segmented bodies with stinging bristle-like structures on each segment.
Some species have jaws and can also inflict very painful bites. Venom causes
swelling and pain.

APPENDIX 5C — Dangerous Marine Animals

5C-13

5C-3.7.1

Prevention. Wear lightweight, cotton gloves to protect against bloodworms, but

wear rubber or heavy leather gloves for protection against bristleworms.
5C-3.7.2

First Aid and Treatment.
1. Remove bristles with a very sticky tape such as adhesive tape or duct tape.

Topical application of vinegar may lessen pain, but this effect is variable.

2. Treatment is directed toward relief of symptoms and may include topical

steroid therapy, systemic antihistamines, and analgesics.

3. Wound infection can occur but can be easily prevented by cleaning the skin

using an antiseptic solution of 10 percent povidone-iodine and topical antiseptic
ointment. Systemic antibiotics may be needed for infections.

5C-3.8

Sea Urchins. Sea urchins have worldwide distribution. Each problematic species

of sea urchin has a radial shape and penetrating spines or seizing organs, known
as globiferous pedicellariae. Penetration by sea urchin spines or the grasp of
pedicellariae can cause intense local pain due to venom effects. Numbness,
generalized weakness, paresthesias, nausea, vomiting, and cardiac dysrhythmias
have been reported.
5C-3.8.1

5C-3.8.2

Prevention. Avoid contact with sea urchins. Protective footwear and gloves are
recommended. Spines can penetrate wet suits, booties, and tennis shoes.
First Aid and Treatment.
1. Remove large spine fragments gently, being very careful not to break them into

small fragments that remain in the wound.

2. Soaking the injured body area in nonscalding hot water up to 113º F (45º C)

may diminish pain.

3. Clean and debride the wound. Topical antiseptic ointment should be used to

prevent infection, but a deep puncture wound(s) may initiate an infection.
If feasible, culture the wound before administering systemic antibiotics for
established infections.

4. Remove as many of the spines and as much of each spine as possible. Some

small fragments may be absorbed by the body. Darkened skin may not
indicate retained spines, but rather pigment that has been released from the
spine’s surface into the wound. Surgical removal, preferably with a dissecting
microscope, may be required when spines are near nerves and joints. X-rays
or other imaging techniques may be required to locate these spines. Spines can
form granulomas months later.

5. Allergic reactions and bronchospasm can be controlled with IM epinephrine

(0.3 cc of 1:1,000 aqueous dilution) and by using systemic antihistamines.
There are no specific antivenoms available.

5C-14

U.S. Navy Diving Manual — Volume 5

6. Administer tetanus immunization as appropriate.
7. Seek medical attention for deep wounds.
5C-3.9

5C-3.9.1

Cone
Snails.
Cone
snails
(sometimes called cone “shells”)
are widely distributed in all
regions and usually found under
rocks and coral or crawling along
the sandy bottom. The snail’s shell
is most often symmetrical in a
spiral coil and colorfully patterned
on its surface, with a distinct head,
one to two pairs of tentacles, two
eyes, and a large flattened foot on
the body (Figure 5C-10). A cone Figure 5C-10. Cone Shell.
snail sting should be considered to
be as potentially severe as a venomous snake bite. The cone snail has a highly
developed venom apparatus: venom is contained in darts inside the proboscis,
which extrudes from the narrow end but is able to reach most of the animal. Cone
snail punctures are followed by a stinging or burning sensation at the site of the
wound. Numbness and tingling begin at the site of the wound and may spread to
the rest of the body; involvement of the mouth and lips is severe. Other symptoms
may include muscular paralysis, difficulty with swallowing and speech, visual
disturbances, and respiratory distress.
Prevention. Avoid handling cone snails. Venom can be injected through

clothing and gloves.

5C-3.9.2

First Aid and Treatment.
1. Lay the victim down.
2. Apply direct pressure with a pressure bandage and immobilization in a position

lower than the level of the heart using splints and elastic bandages.

3. Incision and suction are not recommended.
4. Transport the victim to a medical facility while ensuring that the victim is

breathing adequately. Be prepared to administer mouth-to-mouth breathing if
necessary.

5. Cone snail venom results in paresis or paralysis of skeletal muscle, with or

without myalgias. Symptoms develop within minutes of the sting and effects
can last up to 24 hours.

6. No antivenom is available.

APPENDIX 5C — Dangerous Marine Animals

5C-15

7. Respiratory distress may occur due to neuromuscular blockade. Victims should

be admitted to medical facilities and monitored closely for respiratory or
cardiovascular demise. Treat as symptoms develop.

8. If pain is severe, a local anesthetic without epinephrine may be injected into

the wound site or a nerve block may be performed. Analgesics that produce
respiratory depression should be used with caution.

9. Management of severe stings is supportive. Breathing may need to be supported

with endotracheal intubation and mechanical ventilation.

10. Administer tetanus prophylaxis as appropriate.
5C-3.10

5C-3.10.1

Sea Snakes. The sea
snake is an air-breathing
reptile that has adapted to
its aquatic environment
by, among other things,
developing a paddleshaped tail. Sea snakes
inhabit Indo-Pacific waters
and the Red Sea. The
most hazardous areas in
which to swim are river
mouths, where sea snakes Figure 5C-11. Sea Snake.
sometimes
congregate,
and the water is more turbid. The sea snake is a true snake, usually 3 to 4 feet in
length, but may reach 9 feet. The most commonly encountered species are banded
in appearance (Figure 5C-11). The sea snake is curious and while often attracted to
divers, usually is not aggressive except during mating season.
Sea Snake Bite Effects. Venom of certain sea snakes has toxicity that may exceed

that of cobra venom. The bites usually appear as four puncture marks but may range
from one to 20 punctures. Teeth may remain in the wound. The predominantly
neurotoxic venom is heat-stable, so there is no clinical benefit to hot water
immersion of the bitten body part. Due to the small jaws and short fangs of the
snake, bites often do not result in envenomation. Sea snake bites characteristically
produce little pain, and there is usually a latent period of 10 minutes to several
hours before development of generalized symptoms: muscle aching and stiffness,
thick tongue sensation, progressive paralysis, nausea, vomiting, difficult speech
and swallowing, respiratory distress and failure, and dark-colored urine from
myoglobinuria, which may herald incipient kidney failure.

5C-3.10.2

Prevention. Wet suits or protective clothing, especially gloves, may provide

substantial protection against bites and should be worn when diving in waters
where sea snakes are present. Shoes should be worn when walking where sea
snakes are known to exist, including in the vicinity of fishing operations. Do
not handle sea snakes. Bites often occur to the hands of fishermen attempting to
remove snakes from nets.

5C-16

U.S. Navy Diving Manual — Volume 5

5C-3.10.3

First Aid and Treatment.
1. Keep the victim still.
2. Apply direct pressure using a compression bandage and immobilize the

extremity in the dependent position with splints and elastic bandages.

3. Incision and suction are not useful therapies.
4. Transport all sea snakebite victims to a medical facility as soon as possible,

regardless of their current symptoms, as antivenom will likely be necessary.

5. Watch to ensure that the victim is breathing adequately. Be prepared to

administer mouth-to-mouth breathing or cardiopulmonary resuscitation.

6. The venom predominately blocks neuromuscular transmission. Myonecrosis

with myoglobinuria and renal damage are often seen. Hypotension may
develop.

7. Respiratory arrest may result from generalized muscular paralysis; endotracheal

intubation and mechanical ventilation may be required.

8. Renal function should be closely monitored because peritoneal or hemodialysis

may be needed. Alkalinization of urine with sufficient IV fluids will promote
myoglobin excretion. Monitor renal function and fluid balance anticipating
acute renal failure.

9. Vital signs should be monitored closely. Cardiovascular support plus oxygen

and IV fluids may be required.

10. Because of the possibility of delayed onset of symptoms, all sea snakebite

victims should be observed for at least 12 hours.

11. If symptoms of envenomation occur within one hour, antivenom should be

administered as soon as possible. In a seriously envenomed victim, antivenom
therapy may be helpful even after a significant delay. Antivenom is available
from Commonwealth Serum Laboratories in Melbourne, Australia and in the
United States (see Reference number 1 of this appendix for address and phone
number). If antivenom is used, follow the directions regarding dosage and
sensitivity testing provided on the accompanying package insert. Be prepared
to treat anaphylaxis (severe allergic reaction). Infusion of antivenom by the IV
method or closely monitored drip over a period of one hour is recommended.

12. Administer tetanus immunization as appropriate.
5C-3.11

Sponges. Sponges induce skin irritation (dermatitis) with chemical irritants and

spicules of silica or calcium carbonate embedded in a fibrous skeleton.
5C-3.11.1

Prevention. Avoid contact with sponges. Always wear gloves when handling live

sponges.

APPENDIX 5C — Dangerous Marine Animals

5C-17

5C-3.11.2

First Aid and Treatment.
1. Adhesive or duct tape can remove some of the sponge spicules.
2. Household vinegar (3- to 10-percent acetic acid solution) should be applied

with saturated compresses for 30 to 60 minutes in an initial decontamination as
soon as possible after contact with a sponge.

3. Antihistamine (e.g., diphenhydramine) lotion and later a topical steroid (e.g.,

hydrocortisone) may be applied to reduce the early inflammatory reaction.
Severe reactions may require systemic administration (e.g., oral or injection)
of a corticosteroid.

4. Antiseptic ointment is utilized if there are signs and symptoms of infection.
5C-4

POISONOUS MARINE ANIMALS
5C-4.1

Ciguatera Fish Poisoning. Ciguatera poisoning is caused by eating the flesh

of a fish that has eaten a toxin-producing micro-organism, the dinoflagellate
Gambierdiscus toxicus, or certain other species of dinoflagellates. The poisoning
is common in reef fish between latitudes 35ºN and 35ºS around tropical islands
or tropical and semitropical shorelines in south Florida, the Caribbean, the West
Indies, and the Pacific and Indian Oceans. Fish and marine animals affected
include barracuda, red snapper, grouper, sea bass, amberjack, parrotfish, and the
moray eel. Incidence is unpredictable and depends on environmental changes that
affect the level of dinoflagellates. The toxin is heat-stable, tasteless, and odorless,
and is not destroyed by cooking or gastric acid. Symptoms may begin immediately
or within several hours of ingestion and may include nausea, vomiting, diarrhea,
itching and muscle weakness, aches and spasms. Neurological symptoms may
include pain, ataxia (stumbling gait), paresthesias (tingling), and circumoral
parasthesias (numbness around the mouth). Apparent reversal of hot and cold
sensation when touching or eating objects of extreme temperatures may occur. In
severe cases, respiratory failure and cardiovascular collapse may occur. Pruritus
(itching) is characteristically made worse by alcohol ingestion. Gastrointestinal
symptoms usually disappear within 24 to 72 hours. Although complete recovery
will occur in the majority of cases, neurological symptoms may persist for months
or years. Signs and symptoms of ciguatera fish poisoning may be misdiagnosed
as decompression sickness or contact dermatitis from presumed contact with fire
coral or jellyfish. Because of international transport of fish and rapid modern travel,
ciguatera poisoning may occur far from endemic areas and afflict international
travelers or unsuspecting restaurant patrons.
5C-4.1.1

Prevention. Never eat the liver, viscera, or roe (eggs) of any tropical fish. Unusually

large fish of any given species may be more toxic. When traveling, consult natives
concerning fish poisoning from local fish, although such information may not be
reliable. Although there is a radioimmunoassay to test fish flesh for the presence of
the toxin, there is no diagnostic test that can be applied to human victims.
5C-4.1.2

5C-18

First Aid and Treatment.

U.S. Navy Diving Manual — Volume 5

1. Treatment is supportive and based upon symptoms.
2. In addition to the symptoms described above, other complications that may

require treatment include hypotension and cardiac dysrhythmias.

3. Antiemetics and antidiarrheal agents may be required if gastrointestinal

symptoms are severe. Atropine may be needed to control bradycardia. IV fluids
may be needed to treat hypotension.

4. Intravenous mannitol infusion has been reported to be useful for severe acute

ciguatera poisoning. Amytriptyline has been used successfully to resolve
neurological symptoms such as depression.

5. Cool showers may induce pruritus (itching).
5C-4.2

Scombroid Fish Poisoning. Scombroid fish poisoning occurs from certain fish

that have not been promptly cooled or prepared for immediate consumption.
Typical fish causing scombroid poisoning include tuna, skipjack, mackerel, bonito,
dolphin fish, mahi mahi (Pacific dolphin), and bluefish. Fish that cause scombroid
poisoning are found in tropical and temperate waters. Bacteria in the fish flesh
stimulate production of histamine and saurine (a histamine-like compound),
which produce the symptoms of a histamine-like reaction: nausea, abdominal
pain, vomiting, facial flushing, urticaria (hives), headache, pruritus (itching),
bronchospasm, and a burning or itching sensation in the mouth. Symptoms may
begin one hour after ingestion and last 8 to 12 hours. Death is rare.

5C-4.2.1

5C-4.2.2

Prevention. Immediately clean any fish and preserve by rapid chilling. Do not eat
any fish that has been left in the sun or in the heat longer than two hours. Try to
place all fish intended for consumption on ice or in a cold refrigerator.
First Aid and Treatment. An oral antihistamine, (e.g., diphenhydramine,

cimetidine), epinephrine (given subcutaneously), and steroids are given as needed.

5C-4.3

5C-4.3.1

Pufferfish (Fugu) Poisoning. An extremely potent neurotoxin called tetrodotoxin
is found in the viscera, gonads, liver, and skin of a variety of fish, including the
pufferfish, porcupinefish, and ocean sunfish. Pufferfish—also called blowfish,
toadfish, and balloonfish, and called “fugu” in Japan—are found primarily in the
tropics but also in temperate waters of the coastal U.S., Africa, South America,
Asia, and the Mediterranean. Pufferfish is considered a delicacy in Japan, where
it is thinly sliced and eaten as sashimi. Licensed chefs are trained to select the
pufferfish least likely to be poisonous and also to avoid contact with the visceral
organs in which resides concentrated poison. The first sign of poisoning is usually
tingling around the mouth, which spreads to the extremities and may lead to body
wide numbness. Neurological findings may progress to stumbling gait (ataxia),
generalized weakness, and paralysis. The victim, though paralyzed, may remain
conscious until death occurs from respiratory arrest.
Prevention. Avoid eating pufferfish. Cooking the fish flesh does not destroy the

toxin.

APPENDIX 5C — Dangerous Marine Animals

5C-19

5C-4.3.2

First Aid and Treatment.
1. Provide supportive care with airway management. Monitor breathing and

circulation.

2. Monitor rectal sphincter tone for progression of paralysis.
3. Monitor and treat cardiac dysrhythmias.
5C-4.4

Paralytic Shellfish Poisoning (PSP) (“Red Tide”). Paralytic shellfish poisoning

(PSP) is due to mollusks (bivalves), such as clams, oysters, and mussels that ingest
neurotoxin-containing dinoflagellates. Proliferation of these dinoflagellates in
the ocean during certain months of the year produce a characteristic red (or other
colored) tide. Some dinoflagellate blooms are colorless, so that poisonous mollusks
may unknowingly be consumed. Local public health authorities must monitor
seawater and shellfish samples to detect the toxin(s). Poisonous shellfish cannot
be detected by appearance, smell, or folk methods (e.g., discoloration of either a
silver object or a clove of garlic placed in cooking water). Poisonous shellfish can
be found in either low or high tidal zones. Toxic varieties of dinoflagellates are
common in the following areas: northwestern U.S. and Canada, Alaska, part of
western South America, northeastern U.S., the North Sea European countries, and
in the Gulf Coast area of the U.S. One type of dinoflagellate, although not toxic if
ingested, may lead to eye and respiratory tract irritation from shoreline exposure
when a “bloom” becomes aerosolized by wave action and wind.
5C-4.4.1

Symptoms. Symptoms of systemic PSP include circumoral paresthesias

(tingling around the mouth), which spreads to the extremities and may progress
to muscle weakness, ataxia, salivation, intense thirst, and difficulty swallowing.
Gastrointestinal symptoms are not common. Death, although uncommon, can
result from respiratory arrest. Symptoms begin 30 minutes after ingestion and may
last for many weeks. Gastrointestinal illness occurring several hours after ingestion
is most likely due to bacterial contamination of the shellfish (see paragraph 5C
4.5). Allergic reactions such as urticaria (hives), pruritus (itching), dryness or
scratching sensation in the throat, swollen tongue and bronchospasm may reflect
individual hypersensitivity to a specific shellfish and not be related to PSP.

5C-4.4.2

5C-4.4.3

Prevention. The toxins are heat stable, so cooking does not prevent poisoning.
Broth or bouillon in which shellfish is boiled is especially dangerous because the
toxins are water-soluble and will concentrate in the broth.
First Aid and Treatment.
1. No antidote is known. Lavaging the stomach with alkaline fluids (e.g., a

solution of baking soda) has been reported to be helpful, but is unlikely to be of
great benefit.

2. Provide supportive treatment with close observation and advanced life support

as needed until the illness resolves.

5C-20

U.S. Navy Diving Manual — Volume 5

5C-4.5

Bacterial and Viral Diseases from Shellfish. Large outbreaks of typhoid fever

and other diarrheal diseases caused by the bacteria genus Vibrio have been traced
to consuming contaminated raw oysters and inadequately cooked crabs and
shrimp. Diarrheal stool samples from victims suspected of having bacterial and
viral diseases from shellfish should be placed on a special growth medium (e.g.,
thiosulfate-citrate-bile salts-sucrose agar) to specifically grow Vibrio species, with
isolates being sent to reference laboratories for confirmation.

5C-4.5.1

Prevention. To avoid bacterial or viral disease (e.g., Hepatitus A or Norwalk viral

gastroenteritis) associated with oysters, clams, and other shellfish, an individual
should eat only thoroughly cooked shellfish. It has been proven that eating raw
shellfish (mollusks) definitely presents a risk for contracting gastroenteric disease.

5C-4.5.2

First Aid and Treatment.
1. Provide supportive care with attention to maintaining fluid intake by mouth or

IV.

2. Consult medical personnel for treatment of the various Vibrio species that may

be suspected.

5C-4.6

5C-4.6.1

5C-4.6.2

5C-4.7

5C-4.7.1

Sea Cucumbers. The sea cucumber is frequently eaten in some parts of the world,
where it is sold as “trepang” or “beche-de-mer.” It is boiled and then dried in the
sun or smoked. Contact with the liquid ejected from the visceral cavity of some
sea cucumber species may result in a severe skin reaction (dermatitis) or even
blindness. Intoxication from sea cucumber ingestion is rare.
Prevention. Local inhabitants can advise about the edibility of sea cucumbers in
that region. However, this information may not be reliable. Avoid contact with
visceral juices.
First Aid and Treatment. Because no antidote is known, treatment is symp¬tomatic.
Skin irritation may be treated as are jellyfish stings (paragraph 5C 3.4.4).
Parasitic Infestation. Parasitic infestations of fish can be of two types: superficial
and within the flesh. Superficial parasites burrow into the surface of fish and are
easily seen and removed. These may include fish lice, anchor worms, and leeches.
Parasites embedded into flesh can become encysted or remain free in the muscle,
entrails, and gills of the fish. These parasites may include roundworms, tapeworms,
and flukes. If the fish is inadequately cooked, these parasites can be passed on to
humans.
Prevention. Avoid eating raw fish. Prepare all fish by thorough cooking or hot-

smoking. When cleaning fish, look for mealy or encysted areas in the flesh; cut out
and discard any cyst or suspicious areas. Remove all superficial parasites. Never
eat the entrails or viscera of any fish.

APPENDIX 5C — Dangerous Marine Animals

5C-21

5C-5

REFERENCES FOR ADDITIONAL INFORMATION
1. Stonefish, Sea Snake, and Box Jellyfish antivenom available at Commonwealth

Serum Laboratories, 45 Poplar Road, Parkville, Victoria, Australia; Telephone
Number: 011-61-3-9389-1911.

2. Auerbach, P. (2012) Wilderness Medicine. 6th ed. Philadelphia: Elsevier.
3. Auerbach, P. (1997) A Medical Guide to Hazardous Marine Life. 3rd ed.

Flagstaff: Best Publishing.

4. Budkur, P. (1971) The Life of Sharks. New York: Columbia University Press.
5. Cousteau, J. and Cousteau, P. (1970) The Shark: Splendid Savage of the Sea.

New York: Arrowhead Press.

6. DuPont, H. (1986) Consumption of Raw Shellfish - Is the Risk Now

Unacceptable? New England Journal of Medicine, 314 p.707-708.

7. Edmonds, C. (1995) Dangerous Marine Creatures. 2nd ed. Flagstaff: Best

Publishing.

8. Edmonds, C. et al. (2002) Diving and Subaquatic Medicine. 4th ed. London:

Hodder Arnold.

9. Halstead, B. (1970) Poisonous and Venomous Marine Animals of the World.

Washington, DC: U.S. Government Printing Office, Vol 1-3.

10. Schwartz, G. et al. (1999) Principles and Practice of Emergency Medicine. 4th

ed. Baltimore: Williams & Wilkins.

11. Copyrighted Images
a. Biopix. Schou, JC. Stingray. Digital image. 6/2011. Web. .
b. Wikimedia Commons. Peterson, Jens. Sea Snake. Digital image. 6/2011.

Web. .

c. Wikimedia Commons. Shapiro, Leo. Box Jellyfish. Digital image. 6/2011.

Web. .

d. Wikimedia Commons. U.S. Department of Commerce, National Oceanic

and Atmospheric Administration. Portuguese Man-of-War. Digital image.
6/2011. Web. .

5C-22

U.S. Navy Diving Manual — Volume 5

Index
A
Absolute pressure.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-12
Absorption
of gases.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-30, 3-9, 3-46, 16-5
Accidents
actions required.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5-6, 5-8
equipment shipment.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5-4
investigation requirements.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5-5
reporting criteria.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5-5
Technical Manual Deficiency/
Evaluation Report. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5-4
ACLS. See Advanced Cardiac Life Support
Acronyms. . . . . . . . . . . . . . . . . . . . . . . . . . . . 1D-1, 1D-9
Admiralty Experimental Diving Unit.  .  .  .  .  .  .  .  .  .  .  .  .  . 1-19
ADS-IV. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-25
Advanced cardiac life support.  .  .  .  .  .  . 17-7, 17-40, 17-41
Advanced Diving System IV .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-25
AED. See Automated External Defibrillator
AGE. See Arterial gas embolism
Air compressors
capacity requirements .  .  .  .  .  .  .  .  .  .  . 4-11, 4-12, 4-14
filters. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 4-14
intercoolers. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 4-13
lubrication.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 4-12
oil-lubricated.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 4-12
pressure regulators .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 4-13
reciprocating. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 4-11
Air cylinders, high-pressure.  .  .  .  .  .  .  .  .  .  . 4-14, 7-27, 8-25
Air decompression
air decompression tables.  .  .  .  . 9-9, 9-21, 9-65, 9-86
ascent rate variations.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-31, 9-35
ascent to altitude after diving.  .  .  .  .  .  .  .  .  .  .  .  .  .  .
9-7, 9-49, 9-50, 9-57, 12-3, 15-23
central nervous system
toxicity in chamber .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-42, 9-43
central nervous system toxicity symptoms.  .  .  .  . 9-37
contamination of oxygen with air .  .  .  .  .  .  .  .  .  .  .  . 9-37
decompression sickness during surface
interval. . . . . . . . . . . . . . . . . . . . . . . . 9-40, 9-41
decompression sickness in water. . . . . . . 9-45, 9-46
definitions.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-2, 9-3
dive charting and recording .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-4
dive computers.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-58
diving at altitude.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-46, 9-52, 9-53
Electronically Controlled Closed-Circuit UBA.  .  . 15-1
emergency procedures. . . . . . . . . . . . . . . 9-35, 9-46
exceptional exposure dives .  .  . 9-4, 9-21, 9-30, 9-31
in excess of air decompression table.  .  .  .  .  .  .  .  . 9-35
flying after diving .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-57, 9-58
loss of oxygen supply in chamber .  .  .  .  .  . 9-41, 9-42
loss of oxygen supply in water.  .  .  .  .  .  .  .  . 9-36, 9-37
No-Decompression Table.  .  .  .  .  . 9-8, 9-9, 9-11, 9-21

Index

omitted decompression .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-43, 9-45
oxygen convulsion.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-37
repetitive dives.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
9-11, 9-21, 9-25, 9-29, 9-30, 9-53, 9-58
repetitive group designation table .  .  .  .  .  .  .  . 9-6, 9-8
surface interval greater than 5 minutes .  . 9-39, 9-40
theory of.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-1, 9-2
Air decompression tables
ascent rate.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-7
decompression stop time.  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-7, 9-8
defined.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-2
descent rate.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-7
eligibility for surface decompression .  .  .  .  .  .  .  .  .  . 9-8
in-water decompression on air.  .  .  .  .  .  . 9-7, 9-9, 9-11
in-water decompression on air and oxygen.  .  .  .  .
9-1, 9-9, 9-11, 9-21
last water stop .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-8
mode of decompression selection.  .  .  .  .  .  .  .  .  .  . 9-21
no-decompression dives .  .  .  .  .  .  .  .  .  .  . 9-8, 9-9, 9-63
selecting decompression schedule .  .  .  .  .  .  .  .  .  .  . 9-7
shallow water diving.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2A-1, 6-9
surface decompression on oxygen. . . . . . . . . . .
9-9, 9-15, 9-17, 9-21, 9-40, 9-53
types of. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-6, 9-7
Air sampling program
general procedures .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 4-8, 4-10
maintenance requirements. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 4-9
NSWC -PC sampling services.  .  .  .  .  .  .  .  .  .  .  .  .  .  . 4-9
Air supply systems. See Surface air supply systems
Altitude. See Diving at altitude
Alveolar air. . . . . . . . . . . . . . . 3-9, 3-10, 3-32, 3-47, 3-49
ANU. See Authorization for Navy Use
Anatomy. See Physiology
Anemones.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-10
Animals. See Marine animals
Anticoagulants.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-34, 17-35
Antivenin.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-7, 5C-8, 5C-11
Aqua-Lung.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-10, 1-15
Archimedes’ Principle .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-13
Area
equivalents.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-34
formulas for .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-31
Armored diving suits
history of. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-7, 1-8
Arterial gas embolism. See also Neurological
examination; Recompression chambers
ancillary care .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-20, 17-32
anticoagulants administration. .  .  .  .  .  .  . 17-34, 17-35
aspirin use .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-34, 17-35
causes .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-6
diagnosis of .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-6
diving supervisor’s responsibilities.  .  .  .  .  .  .  .  .  .  . 17-3
emergency consultation.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-5

Index–1

emergency medical equipment
requirements.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-36
fluids replacement .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-33, 17-35
lidocaine use .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-34, 17-35
non-standard treatments .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-31
post-treatment considerations .  .  .  .  .  .  . 17-28, 17-29
prescribing and modifying treatments .  .  .  .  .  .  .  . 17-4
recompression treatment.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-14
resuscitation of a pulseless diver.  .  .  .  .  .  .  .  .  .  .  . 17-7
sleeping and eating .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-20
steroids use .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-35
surface oxygen use .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-33, 17-34
symptom recurrence. . . . . . . . . . . . . . . . . . . . 17-42
symptoms of.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-7
treatment abort procedures .  .  .  .  .  .  .  .  . 17-31, 17-32
treatment of .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-7
treatment tables.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-17, 17-21
Ascent procedures. . . . . . . . . . . . . . . . . . . . . . . . . .
17-48, 17-49, 8-36, 12-4, 15-18, 15-23, 16-20
Ascent rate
delays in arriving at first decompression
stop.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-31
delays in leaving a stop .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-32, 9-35
early arrival at first decompression stop.  9-31, 12-11
travel rate exceeded. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-31
variations .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-31, 12-11
Ascent to altitude.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
9-7, 9-49, 9-57, 2B-2, 2B-7, 12-3, 15-23
Aspirin.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-58, 17-34, 17-35
Asymptomatic omitted decompression.  .  .  .  .  .  .  .  .  .  . 9-43
ata. See Atmospheres absolute
Atmospheres absolute. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-18
Atmospheric air.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-14, 2-15
Atmospheric pressure.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-12
Atoms .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-1, 2-15
Authorization for Navy Use.  .  .  .  . 4-2, 18-6, 18-17, 18-30
Automated External Defibrillator. 6-18, 6-19, 17-7, 17-36

B
Bacterial shellfish diseases.  .  .  .  .  .  .  .  .  .  .  .  . 5C-20, 5C-21
Barometric pressure .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-11, 4-11, 9-52
Barracuda .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-18
Barrel diving suit .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-8
Bert, Paul. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-6, 1-11
BIBS. See Built-in breathing system
Bleeding control. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-9
Blood components. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-3
Bloodworms. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-14
Body temperature .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-11
Bond, Captain George F..  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-22
Bottom time
air decompression table.  .  .  .  .  .  .  .  .  .  .  .  .  . 9-65, 9-86
defined.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-1, 9-2
in excess of air decompression table.  .  .  .  .  .  .  .  . 9-36

Index–2

operational risk management.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 6-6
Box jellyfish.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-9, 5C-11
Boyle’s law. .  .  .  .  .  .  .  .  .  . 2-17, 2-19, 2-21, 3-6, 3-30, 7-17
Breathing air
purity standards.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 4-5, 4-9
sampling program. . . . . . . . . . . . . . . . . . . . . 4-8, 4-9
Breathing bags
history of. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-3, 3-13, 3-15
Breathing gas mixing procedures
cascading.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 14-3
continuous-flow .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 14-7
gas analysis.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 14-8
gas transfer system .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 14-2, 14-4
ideal-gas method mixing .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 14-2
mixing by partial pressure .  .  .  .  .  .  .  .  .  .  .  . 14-1, 14-2
mixing by volume.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 14-7, 14-8
mixing by weight. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 14-8
oxygen percentage adjustment .  .  .  .  .  .  .  . 14-5, 14-7
Breathing tubes
history of. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-2
Bristleworms,.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-14
Browne, Jack.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-18
Built-in breathing system.  .  .  .  .  .  .  .  .  .  .  . 18-2, 18-3, 18-20
Buoyancy. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-13, 2-14
Buoyancy compensators.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-14, 7-15

C
Caisson disease. 1-6. See also Decompression sickness
Caissons
history of. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-5, 1-6
Carbon dioxide
properties of.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-16
toxicity .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-26, 15-27
Carbon monoxide .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-16
Cardiopulmonary resuscitation .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5B-1
Caustic cocktail.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-29, 16-5
CCTV. See Closed-circuit television
Celsius scale.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-3
Central nervous system. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-1, 3-2
Central nervous system toxicity
causes of .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-42, 15-24, 16-2
in chamber.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-42, 9-43
closed-circuit oxygen UBA diving.  .  .  .  .  .  .  .  .  .  .  . 16-2
helium-oxygen dives. . . . . . . . . . . . . . . 12-15, 12-19
Electronically Controlled Closed-Circuit UBA
diving. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-23, 15-24
off-effect.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-26, 16-3
prevention of. . . . . . . . . . . . . . . . . . . . . . . . . . 15-26
during recompression chamber treatment.  .  .  . 17-26
SCUBA diving. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-11, 1-12
symptoms.  .  .  .  .  .  .  .  . 9-37, 15-26, 18-24, 16-2, 16-3
treatment of .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-24, 15-27
Chariot torpedoes .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-13, 1-14
Charles’/Gay-Lussac’s law .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-18, 2-21
Chemical injury .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-29, 16-5, 16-6

U.S. Navy Diving Manual

Chest cavity physiology.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-6
Chokes .  .  .  .  .  .  .  .  .  .  .  . 17-11, 17-12, 17-16, 17-33, 17-34
Ciguatera fish poisoning .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-18
Circulatory system physiology
anatomy.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-2
blood components .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-3, 3-5
circulatory function.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-2, 3-3
heart.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-2, 3-3
pulmonary and systemic circuits .  .  .  .  .  .  .  .  .  .  .  .  . 3-2
Closed-circuit oxygen rebreather. . . . . . . . . . . . . . . 16-1
Closed-circuit oxygen UBA diving
ascent procedures.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 16-20
carbon dioxide toxicity .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 16-4
central nervous system oxygen toxicity.  .  .  .  .  .  . 16-2
chemical injury.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 16-5, 16-6
closed -circuit oxygen rebreather.  .  .  .  .  .  .  .  .  .  .  . 16-1
combat operations.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 16-13
diving at altitude.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 16-13
equipment requirements. . . . . . . . . . . . . . . . . 16-15
exposure limits.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 16-11, 16-12
flying after diving .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 16-13
inadvertent excursions.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 16-9
maximizing operational range .  .  .  .  .  .  .  .  .  .  .  .  . 16-13
middle ear oxygen absorption syndrome.  16-6, 16-7
MK 25 MOD 2. . . . . . . . . . . . . . . . . . . . . 19-9, 19-12
operating limitations.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 16-13
operations planning .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 16-13, 16-14
oxygen deficiency. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 16-3
oxygen exposure limit testing.  .  .  .  .  .  .  .  .  .  .  .  .  .  . 16-7
oxygen susceptibility precautions. .  .  .  .  .  .  .  .  .  .  . 16-7
personnel requirements.  .  .  .  .  .  .  .  .  .  .  . 16-14, 16-15
postdive procedures.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 16-20
predive precautions .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 16-16, 16-17
predive procedures. . . . . . . . . . . . . . . . . . . . . 16-17
pulmonary oxygen toxicity .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 16-3
single-depth limits. . . . . . . . . . . . . . . . . . . . . . 16-10
training.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 16-14, 16-15
transit with excursion limits. . . . . . . . . . . . 16-7, 16-8
underwater procedures .  .  .  .  .  .  .  .  .  .  .  . 16-19, 16-20
water entry and descent.  .  .  .  .  .  .  .  .  .  .  . 16-18, 16-19
Closed-circuit television. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-4
CNS. See Central nervous system
CNS toxicity. See Central nervous system toxicity
Cochran Navy Air III. . . . . . . . . . . . . . . . . . . . . . . . . 9-58
Coelenterates .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-9, 5C-11
Cold water diving
emergency procedures. . . . . . . . . . . . . 11-15, 11-16
information resources. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 11-1
operating precautions. .  .  .  .  .  .  .  .  .  .  .  .  .  . 11-12, 11-15
operations planning .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 11-1, 11-10
predive procedures. . . . . . . . . . . . . . . . 11-10, 11-12
Color visibility. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-6
Combat swimmers
missions.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 6-6
World War II SCUBA use.  .  .  .  .  .  .  .  .  .  .  .  . 1-14, 1-15
Command Diving Log .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-16, 13-17

Index

Command Smooth Diving Log. . . . . . . . . . . . . . . 5-2, 5-4
Communications System. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-4
Communications
diver intercommunication systems.  .  .  .  .  . 8-23, 8-24
line-pull signals. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-39, 7-42, 8-23
Conduction .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-10
Cone snails.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-15
Construction, underwater .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 6-6
Convection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-10
Convulsions. See Oxygen convulsion
Coral .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-11, 5C-12
Cousteau, Jacques-Yves. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-10, 1-22
CPR. See Cardiopulmonary resuscitation
Cross Correction.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-46, 9-47
Cylinders, SCUBA
backpacks .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-13, 7-28
guidelines for handling.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-12
harnesses. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-13
identification markings.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-11
identification requirements.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-5
manifold assemblies. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-12, 7-13
manifold connectors.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-13
over pressure safety device.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-13
pressure gauge requirements .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-10
sizes of.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-12
specification requirements.  .  .  .  .  .  .  .  .  .  .  . 7-10, 7-11
valves.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-12

D
Dalton’s law.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-24, 2-28, 14-1
Davis, Sir Robert H.. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-20
Davis Lung. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-13
DDC. See Deck decompression chambers
DDS. See Deep Diving Systems
Deane, Charles.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-4
Deane, John .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-8
Deane’s Patent Diving Dress. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-4
Deck decompression chambers .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-25
Decompression. See Air decompression
Decompression chambers. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-25
Decompression dive .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-1
Decompression schedule .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-3
Decompression sickness. See also Neurological
examination; Recompression chambers
at altitude.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-13
ancillary care .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-20
anticoagulants administration. .  .  .  .  .  .  . 17-34, 17-35
aspirin use .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-34, 17-35
cause of.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-6
diagnosis of .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-9
diving supervisor’s responsibilities.  .  .  .  .  .  .  .  .  .  . 17-3
emergency consultation.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-5
emergency medical equipment
requirements.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-36

Index–3

environmental temperature .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-35
fluids replacement .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-33
lidocain.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-34
non-standard treatments .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-31
post-treatment considerations .  .  .  .  .  .  . 17-28, 17-30
prescribing and modifying treatments .  .  .  .  .  .  .  . 17-4
prevention and treatment of.  .  .  .  .  .  .  .  .  .  .  .  . 1-6, 1-7
recompression treatment.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-21
steroids use .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-35
during surface interval .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 12-25
surface oxygen use .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-33, 17-34
symptom recurrence. . . . . . . . . . . . . . . . . . . . 17-42
symptomatic omitted decompression.  .  .  .  .  .  .  . 12-22
symptoms of.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-9, 17-11
treatment abort procedures .  .  .  .  .  .  .  .  . 17-31, 17-36
treatment of .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-14, 17-17
treatment tables.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-43, 17-52
Type I.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-40, 17-9, 17-11
Type II. . . . . . . . . . . . . . . . . . . . 13-40, 13-41, 17-11
in water. .  .  .  .  .  .  .  .  . 9-45, 9-46, 12-24, 12-25, 17-15
when treatment is not necessary.  .  .  .  .  .  .  .  .  .  .  . 20-2
Decompression stops .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-3
Decompression tables.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
9-3. See also Air decompression tables
Deep diving records. . . . . . . . . . . . . . . . . . . . . 1-30, 1-31
Deep Diving Systems .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-24, 13-1, 14-8
Deep Submergence Rescue Vehicle. .  .  .  .  .  .  .  .  .  .  .  . 1-29
Deep Submergence Review Group. .  .  .  .  .  .  .  .  .  .  .  .  . 1-29
Deep Submergence Systems Project.  .  .  .  .  .  .  .  .  .  .  . 1-29
Deepest depth.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-2
Demand regulators
first stage .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-8
full face mask.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-10
mouthpiece. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-10
octopus. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-10
Rouquayol’s.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-9
schematic.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-9
second stage .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-8
single hose regulators .  .  .  .  .  .  .  .  .  .  . 3-16, 3-32, 11-3
Descent procedures .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-27, 12-7
Descent rate .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-7
Descent time
defined.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-2
Dewpoint.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-29, 4-13
Diffusion. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-6
Divator DP Surface Supplied Diving System. . 8-15, 8-18
Dive computers.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-20, 2B-1, 2B-9
Dive/Jump Reporting System .  .  .  .  .  .  .  .  .  .  .  . 5-1, 5-2, 5-4
Dive Medical Officer .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-2, 17-1
Dive program administration
Command Smooth Diving Log.  .  .  .  .  .  .  .  .  .  . 5-2, 5-4
dive mishap/near mishap/hazard reporting .  5-4, 5-6
Dive Jump Reporting System. .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5-9
Diver’s Personal Dive Logbooks .  .  .  .  .  .  .  .  .  .  .  .  . 5-4
Diving Life Support Equipment Failure Analysis
Report.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5-4
diving mishap/casualty reporting .  .  .  .  .  .  .  .  . 5-4, 5-5

Index–4

documents.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5-1, 5-2
Equipment Accident/Incident Information
Sheet. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5-7, 5-8
equipment failure or deficiency reporting.  .  . 5-7, 5-8
Failure Analysis Report .  .  .  .  .  .  .  .  .  .  .  .  . 5-1, 5-2, 5-4
Recompression Chamber Log.  .  .  .  .  .  .  .  .  .  . 5-2, 5-3
record keeping and reporting system objectives.
5-1, 5-2
Dive Reporting System.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5-4
Dive systems
alteration of diving equipment .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 4-2
Authorization for Navy Use. . . . . . . . . . . . . . . . . 4-2
breathing air sampling program.  .  .  .  .  .  .  .  . 4-8, 4-11
breathing gas purity standards.  .  .  .  .  .  .  .  .  .  . 4-4, 4-7
document precedence.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 4-2
operating and emergency procedures.  .  .  .  . 4-3, 4-4
Planned Maintenance System.  .  .  .  .  .  .  .  .  .  .  .  .  .  . 4-2
System Certification Authority .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 4-3
technical program managers.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 4-3
Diver buoyancy.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-13, 2-14
Diver communications
diver intercommunication systems.  .  .  .  .  .  .  .  .  .  . 8-23
line-pull signals. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-23, 8-24, 8-25
Diver fatigue .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 12-3
Diver-guided torpedoes.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-13, 1-14
Diver noise. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-7
Diver’s Personal Dive Logbooks.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5-4
Diving at altitude
air diving chart .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-55, 9-60, 9-60
altitude correction procedure.  .  .  .  .  .  .  .  .  . 9-47, 9-49
closed-circuit oxygen UBA diving.  .  .  .  .  .  .  .  .  .  . 16-13
Cross Correction .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-46, 9-47
depth measurement at altitude. .  .  .  .  .  .  .  .  .  .  .  .  . 9-49
equilibration at altitude.  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-49, 9-50
need for correction.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-49
repetitive dives.  .  .  .  .  .  .  . 9-21, 9-53, 9-56, 9-59, 9-60
sea level equivalent depth.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-48
surface-supplied mixed gas dives .  .  .  .  .  .  .  .  .  .  . 12-3
worksheets.  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-51, 9-54, 9-56, 9-59
Diving bells. See also Caissons
history of. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-3, 1-4
mixed-gas diving .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-20, 1-22
Diving charts
abbreviations .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-4, 9-6
diving at altitude.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-55, 9-62
nitrogen-oxygen diving.  .  .  .  .  .  .  . 15-20, 15-22, 17-25
repetitive dives.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-2, 9-24, 9-53
Diving injuries. See also Arterial gas embolism;
Decompression sickness; First aid
initial assessment of.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5A-1, 5A-2
neurological assessment.  .  .  .  .  .  .  .  .  .  .  . 5A-2, 5A-13
Diving Life Support Equipment Failure Analysis
Report. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-4, 5-8
Diving physics. See Physics
Diving records.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-30, 1-31
Diving suits. See also Helmets
armored .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-7, 1-8

U.S. Navy Diving Manual

design history.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-3, 1-5
MK V deep-sea diving dress .  .  .  .  .  .  .  .  .  .  .  . 1-8, 1-9
Dizziness.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 12-22
DJRS. See Dive/Jump Reporting System
DLSE. See Diving life-support equipment
Double-lock steel recompression chamber.  .  . 18-6, 18-9
Draeger Lung Automatic Regenerator V.  .  .  .  . 1-14, 1-15
DRS. See Dive Reporting System
DSRG. See Deep Submergence Review Group
DSRV. See Deep Submergence Rescue Vehicle
DSSP. See Deep Submergence Systems Project
Duke University.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-23, 1-24

E
EAD. See Equivalent air depth
EBS. See Emergency breathing system
EDU. See Experimental Diving Unit
EEHS. See Emergency Evacuation Hyperbaric
Stretcher
EGS. See Emergency Gas Supply
Electronically Controlled Closed-Circuit UBA
altitude diving procedures .  .  .  .  .  .  .  .  .  . 15-23, 15-24
ascent procedures.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-18
canister duration limits.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-9
carbon dioxide toxicity .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-27
central nervous system oxygen toxicity. . 15-24, 15-26
characteristics .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-6
chemical injury.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-29, 15-30
decompression procedures .  .  .  .  .  .  .  .  . 15-18, 15-23
decompression sickness in water. . . . . . . . . . 15-32
decompression tables .  . 15-39, 15-51, 15-69, 15-77
descent. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-17
dive briefing .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-16
dive record sheet.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-14
diving procedures.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-12
diving supervisor check .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-13
emergency breathing system.  .  .  .  .  .  .  . 15-11, 15-22
equipment reference data .  .  .  .  .  .  .  .  .  . 15-32, 15-33
equipment requirements. . . . . . . . . . . . . 15-9, 15-11
flying after diving .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-23, 15-24
limitations.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-7
line-pull signals. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-16
multi-day diving .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-23
no-decompression limits. . . . . . 15-36, 15-48, 15-66
omitted decompression .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-30
operational planning.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-5, 15-13
oxygen deficiency. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-26
oxygen flask endurance.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-8
personnel requirements.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-8
postdive procedures.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-24
predive procedures. . . . . . . . . . . . . . . . 15-13, 15-15
pulmonary oxygen toxicity .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-26
recompression chamber requirements.  15-11, 15-12
repetitive dive worksheet.  .  .  .  .  . 15-38, 15-50, 15-68
repetitive group designators.  .  .  . 15-36, 15-48, 15-66

Index

residual helium timetable.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-49
Residual Nitrogen Time .  .  .  .  .  .  .  .  .  .  .  . 15-37, 15-66
underwater procedures .  .  .  .  .  .  .  .  .  .  .  . 15-17, 15-18
Elements.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-1
Elk River .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-25, 1-26
Embolism. See Arterial gas embolism
Emergency breathing system .  .  .  .  .  .  .  .  .  .  . 15-11, 15-21
Emergency Evacuation Hyperbaric Stretcher.  .  .  .  .  . 18-4
Emergency Gas Supply. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-11
Emergency medical equipment. See also First aid
advanced cardiac life support. . . . . . . . 17-40, 17-41
emergency kits.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-41
portable monitor-defibrillator. . . . . . . . . . . . . . 17-36
Emergency operating procedures
air decompression .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-35, 9-46
approval process .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 4-3
cold water and ice diving .  .  .  .  .  .  .  .  .  .  .  . 11-15, 11-16
format.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 4-5
helium-oxygen dives. . . . . . . . . . . . . . . 12-12, 12-25
nonstandardized. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 4-4
standardized. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 4-2
surface air supply systems.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 4-14
Emerson-Lambertsen Oxygen Rebreather.  .  . 1-14, 1-15
Enclosed space diving. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2C-12
Energy
classifications of.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-5
equivalents.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-34
heat energy in diving .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-10, 2-11
kinetic energy.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-5, 2-16, 2-17
Law of the Conservation of Energy .  .  .  .  .  .  .  .  .  .  . 2-5
light energy in diving. . . . . . . . . . . . . . . . . . . 2-5, 2-6
mechanical energy in diving.  .  .  .  .  .  .  .  .  .  .  . 2-6, 2-10
types of. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-4, 2-5
English System of measurement
pressure measurement .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-11
temperature measurements.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-3
use of.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-2, 2-3
Environmental Assessment Worksheet.  .  .  .  .  .  .  .  .  . 2C-10
EOD. See Explosive Ordnance Disposal
EPs. See Emergency operating procedures
Equipment. See Dive systems
Equipment Accident/Incident Information Sheet.5-9, 5-10
Equivalent air depth. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 10-1, 10-5, 10-7
Equivalent single dive.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-4
Equivalent single dive time .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-4
Exceptional exposure dives. .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-4, 9-31
Experimental Diving Unit.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-12, 13-7
Explosions. See Underwater explosions
Explosive Ordnance Disposal. See also
Electronically Controlled Closed-Circuit UBA
mission objective .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 6-5
training and missions.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-14
underwater breathing apparatus development.  .  . 1-13
Extreme exposure suits.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 11-8

Index–5

F
Face masks
cold water diving. . . . . . . . . . . . . . . . . . . . . . . . .11-5
SCUBA diving. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-7, 7-10
FADS. See Flyaway Dive System III
Fahrenheit scale .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-3
Failure Analysis Report.  .  .  .  .  .  .  .  .  .  .  . 5-1, 5-2, 5-4, 6-28
FAR. See Failure Analysis Report
FARCC. See Fly Away Recompression Chamber
Fire suppression systems.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-21
First aid
cardiopulmonary resuscitation.  .  .  .  .  .  .  .  .  .  .  .  .  .
5B-1, 5B-7, 5C-13, 5C-17
massive bleeding control.  .  .  .  .  .  .  .  .  .  .  .  . 5B-1, 5B-6
poisonous marine animals.  .  .  .  .  .  .  .  .  . 5C-18, 5C-21
shark bites .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-1, 5C-3
shock .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5B-6, 5B7
venomous marine animals.  .  .  .  .  .  .  .  .  .  . 5C-6, 5C-17
Fish, venomous.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-6, 5C-7
Fish poisoning.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-18, 5C-19
Flasks, high-pressure. 8-14, 8-22, 8-23, 10-8, 14-7, 18-4
FLATUS I.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-12
Fleet Modernized Double-Lock Recompression
Chamber. . . . . . . . . . . . . . . . . . . . . . . . . 18-3, 18-10
Fleuss, Henry A. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-10, 1-11, 1-13
Fly Away Recompression Chamber . . 18-4, 18-13, 18-14
Flyaway Dive System III .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-19, 8-20
Flyaway Dive System III Mixed Gas System.  . 12-4, 12-5
Flying after diving .  .  .  .  .  .  .  .  .  .  . 9-57, 9-58, 15-23, 15-24
FMGS. See Flyaway Dive System III Mixed Gas System
French caissons .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-5, 1-6
Fugu poisoning .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-19

G
Gagnan, Emile. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-10
Gas diffusion.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-28, 2-29
Gas embolism. See Arterial gas embolism
Gas laws
Boyle’s law.  .  .  .  .  .  . 2-17, 2-19, 2-21, 3-6, 3-30, 7-17
Charles’/Gay-Lussac’s law.  .  .  .  .  .  .  .  .  .  .  . 2-18, 2-21
Dalton’s law .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-24, 2-28, 14-1
general.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-17, 2-23
Henry’s law. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-29, 3-46
Gas mixing procedures. See Breathing gas mixing
procedures
Gas mixtures
absorption. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-30
Dalton’s law .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-24, 2-26
gas diffusion.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-28, 2-29
gas tension.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-30
Henry’s law. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-29
humidity and.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-29
in liquids.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-29
partial pressures of small quantities.  .  .  .  .  .  .  .  .  . 2-28

Index–6

solubility.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-30, 2-31
surface equivalent values. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-27
Gas tension.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-30, 3-59
Gases. See also Dive systems
atmospheric air. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-14
breathing gas purity standards.  .  .  .  .  .  .  .  .  .  . 4-4, 4-7
carbon dioxide .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-16
carbon monoxide.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-16
gas analysis.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 14-8, 14-9
gas laws.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-17, 2-23
gas mixtures.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-23, 2-31
helium. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-15
hydrogen .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-15
kinetic theory of gases.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-16
measurements.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-3
neon.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-15
nitrogen .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-15
oxygen.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-15
Gauge pressure. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-20, 2-22
Gay-Lussac’s law .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-18, 2-21
General gas law. . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-21
Genesis Project.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-22, 2-23

H
Haldane, J.S..  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-7, 1-26
Harbor Clearance Unit One.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-30
Hazard
defined.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5-4, 5-5
Hazardous marine animals. See Marine animals
HCU 1. See Harbor Clearance Unit One
Heart physiology.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-2, 3-3
Heat energy.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-10, 2-11
Heat transfer rate. . . . . . . . . . . . . . . . . . . . . . . 2-10, 2-11
Helium
properties of.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-15
purity standards.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 4-7
Helium-oxygen diving .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
1-17, 1-20. See also Mixed-gas diving; closedcircuit UBA
Helmets. See also Diving suits; Surface-Supplied
Diving Systems
inadequate ventilation .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-7
KM-37 NS. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-7, 8-14
MK V Diving Helmet.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-8
MK V MOD 1 helmet .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-18, 1-20
Hemorrhage control. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5B-1, 5B-6
Henry’s law .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-29, 3-46
High-pressure air cylinders/flasks.  .  .  .  .  .  .  .  .  . 4-14, 4-15
HMS Royal George.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-5
Hot water suits. .  .  .  .  .  .  .  .  . 2C-5, 2C-7, 11-7, 11-8, 13-10
Humidity
gas mixtures and .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-29
Hydrogen.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-15
Hydrogen-oxygen diving.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-18, 1-19
Hydrostatic pressure.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-12, 2-13

U.S. Navy Diving Manual

Hyperbaric oxygen therapy.  .  .  .  .  .  .  .  .  . 3-22, 17-1, 17-21
Hypercapnia .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-15, 3-18
Hypothermia .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-53, 3-56
Hypoxia.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-12, 3-22

I
Ice water diving
emergency procedures. . . . . . . . . . . . . 11-15, 11-16
information resources. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 11-1
operating precautions. .  .  .  .  .  .  .  .  .  .  .  .  .  . 11-12, 11-15
operations planning .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 11-1, 11-10
predive procedures. . . . . . . . . . . . . . . . 11-10, 11-12
In-water decompression .  .  .  .  .  .  . 9-9, 9-11, 12-13, 12-14
Incidents
actions required.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5-6, 5-8
equipment shipment.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5-4
investigation requirements.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5-5
reporting criteria.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5-5
Technical Manual Deficiency/
Evaluation Report.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5-4
Intercom systems .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-4
Internal bleeding .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5B-6
International System of Units
pressure measurement .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-11, 2-14
use of.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-2, 2-3

J
Jellyfish .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-9, 5C-11, 5C-18

K
Kaiten diver-guided torpedoes. . . . . . . . . . . . . . . . . 1-14
Keller, Hannes.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-19
Kelvin scale.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-3
Killer whales .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-3, 5C-4
Kinetic energy.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-5, 2-16, 2-17
Kinetic theory of gases .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-16, 2-17

L
Lambert, Alexander.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-11
Lambertsen, Dr. C.J..  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-12, 1-14
Lambertsen Amphibious Respiratory Unit.  .  .  .  .  .  .  .  . 1-14
LAR V. See Draeger Lung Automatic Regenerator V
LARU. See Lambertsen Amphibious Respiratory Unit
Law of the Conservation of Energy.  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-5
Length equivalents .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-34
LePrieur’s SCUBA design.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-9, 1-10
Lethbridge, John.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-3, 1-8
LFA. See Low-frequency active sonar
Lidocaine.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-34, 17-35, 5C-7, 5C-11

Index

Life preservers. .  .  .  .  .  .  .  .  .  .  . 7-14, 7-15, 7-29, 7-50, 11-5
Life-support systems.  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-7, 13-8, 13-10
Light energy. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-5
Light scattering .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-6
Lightheadedness.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-29, 12-22, 17-11
Lightweight Dive Systems.  .  .  .  .  .  .  .  .  .  .  .  . 4-13, 8-1, 8-18
Line-pull signals. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-39, 7-42, 8-23
Link, Edward A..  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-22
Lionfish .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-7
Low-frequency active sonar. . . . . . . . . . . . . . . . . . . 1A-1
LSS. See Life-support systems
Lung Automatic Regenerator V.  .  .  .  .  .  .  .  .  .  .  . 1-14, 1-15
Lungs physiology. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-6, 3-8
LWDS. See Lightweight Dive Systems

M
Marine animals
attacking.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-1, 5C-6
poisonous.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-17, 5C-21
venomous. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-6, 5C-17
Masks. See Face masks
Mass equivalents. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-35
Matter .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-1, 2-2
Maximum breathing capacity. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-9
Maximum depth.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-2
Maximum expiratory flow rate.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-9
Maximum inspiratory flow rate. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-9
Maximum voluntary ventilation .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-9
MCC. See Main control consoles
McCann-Erickson Rescue Chamber.  .  .  .  .  .  .  .  .  .  .  .  . 1-28
Measurement systems .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-2, 2-3
Mechanical energy
sound.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-6, 2-8
underwater explosions.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-8, 2-10
Medical equipment. See Emergency medical equipment
Middle ear oxygen absorption syndrome. . . . . . . . . .
3-60, 3-61, 16-6, 16-7
Mixed-gas diving. See also Breathing gas mixing
procedures; Electronically Controlled ClosedCircuit UBA; Nitrogen narcosis; Operational
Risk Management
dive team selection. . . . . . . . . . . . . . . . . . . . . 12-12
diving bells.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-20, 1-21
nonsaturation diving.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-16, 1-20
operational tasks .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 12-1
Remotely Operated Vehicles.  .  .  .  .  .  .  .  .  .  .  .  .  . 2C-14
saturation diving.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-21, 1-24
Mixed-gas diving theory
Boyle’s law.  .  .  .  .  .  . 2-17, 2-19, 2-21, 3-6, 3-30, 7-17
Charles’/Gay-Lussac’s law.  .  .  .  .  .  .  .  .  .  .  . 2-18, 2-21
Dalton’s law .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-24, 2-27, 2-28, 14-1
general.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 12-17, 2-23
Henry’s law. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-29, 3-46
Mixed-gas rebreathers. . . . . . . . . . . . . . . . . . . 1-12, 1-13
MK 12 Mixed-Gas Surface-Supplied Diving System. . 1-20

Index–7

MK 1 MOD 0 Diving Outfit.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-20, 1-25
MK 2 MOD 0 Diving Outfit.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-25, 1-26
MK 20 MOD 0 Surface-Supplied Diving System.  .  .  .  .
8-14, 8-15
MK 3 MOD 0 Surface-Supplied Diving
Systems.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-18, 8-19
MK 12 Surface-Supplied Diving System.  .  .  .  .  .  .  .  .  .  . 1-8
MK 21 Surface-Supplied Diving System.  .  .  .  .  .  .  .  .  .  . 1-8
MK 6 UBA .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-12, 1-13
MK V deep-sea diving dress
history of. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-8, 1-9
MK V MOD 1 helmet.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-18
Molecules. 2-6, 2-16, 2-17, 2-27, 2-30, 3-47, 3-48, 10-11
Moray eels.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-4, 5C-5
Multi-day diving.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-23

N
Naval Safety Center .  .  .  . 5-1, 5-4, 6-13, 9-4, 11-1, 12-25
Naval Submarine Medical Research
Laboratory .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1A-1, 1A-2
Navy Dive Computer
advantages of. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2B-3
ascent procedures.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2B-6
ascent to altitude .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2B-7
decompression.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2B-6
decompression sickness in the water. . . . . . . . 2B-9
exceeded decompression limits.  .  .  .  .  .  .  .  .  .  .  .  . 2B-9
function. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2B-2
loss of NDC .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2B-7
omitted decompression .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2B-7
principles of operation .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2B-1, 2B-4
predive procedures. . . . . . . . . . . . . . . . . . . . . . 2B-5
postdive procedures.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2B-6, 2B-7
repetitive diving .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2B-7
safety .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2B-3
Navy Diving Salvage and Training Center. .  .  .  .  .  .  .  . 17-6
Navy Experimental Diving Unit
emergency medical consultation .  .  .  .  .  .  .  .  .  .  .  .
9-35, 12-12, 13-39, 16-13, 17-6
life support equipment testing .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5-7
mission of.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-7, 13-8
SCUBA research .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-12, 1-13
Sealab project research.  .  .  .  .  .  .  .  .  .  .  .  .  . 1-22, 1-23
NDSTC. See Navy Diving Salvage and Training Center
NEDU. See Navy Experimental Diving Unit
Neon .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-15
Nervous system physiology. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-1, 3-2
Neurological examination
checklist.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5A-3, 5A-4
coordination .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5A-5, 5A-6
cranial nerves.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5A-6, 5A-7
deep tendon reflexes.  .  .  .  .  .  .  .  .  .  .  .  .  . 5A-10, 5A-13
initial assessment of injuries. . . . . . . . . . 5A-1, 5A-2
mental status .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5A-5
motor system.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5A-7, 5A-8, 5A-9

Index–8

sensory function.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5A-8, 5A-10
Nitrogen
characteristics of .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-15
purity standards.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 4-8
Nitrogen narcosis. . . . . . 1-7. See also Mixed-gas diving
Nitrogen-oxygen diving. See also Electronically
Controlled Closed-Circuit UBA
advantages of. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 10-1
breathing gas purity.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 10-9
disadvantages of .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 10-1
dive charting.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 10-5, 10-6
equipment cleanliness.  .  .  .  .  .  .  .  .  .  .  .  .  .  . 10-8, 10-9
equipment requirements. . . . . . . . . . . . . . 10-7, 10-8
Equivalent Air Depth. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 10-1, 10-4
fleet training.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 10-7
mixing, blending and storage systems . . 10-12, 10-13
NITROX mixing .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 10-9, 10-11
oxygen toxicity.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 10-2, 10-3
procedures.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 10-3, 10-5
repetitive diving .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 10-5
NITROX. See Nitrogen-oxygen diving
No-decompression dives.  .  .  . 3-53, 6-8, 8-11, 12-9, 15-20
No-decompression limits.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
9-6, 9-8, 9-44, 10-5, 2B-7, 15-20, 17-8
No-Decompression Tables .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
2A-2, 9-10, 9-63, 15-36, 15-48, 15-66
No-stop table.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-8
Nohl, Max Gene. . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-18
Non-steroidal anti-inflammatory drugs. . . . . 17-34, 17-35
Nonsaturation diving
helium-oxygen diving.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-16, 1-18
hydrogen-oxygen diving.  .  .  .  .  .  .  .  .  .  .  .  .  . 1-18, 1-19
MK 1 MOD 0 Diving Outfit .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-20
surface-supplied.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-19
NSMRL. See Naval Submarine Medical Research
Laboratory
NSWC -PC
air sampling services.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 4-9

O
Ocean Simulation Facility .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-24, 13-7
Octopuses.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-12, 5C-13
Off-effect.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-26, 16-3
Offgassing.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-30
Omitted decompression
asymptomatic.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
9-43, 9-45, 2B-7, 12-20, 15-31, 17-17, 17-18
symptomatic.  .  .  .  .  .  .  .  .  . 12-22, 15-30, 15-32, 17-13
One-atmosphere diving suits. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-8
Open-circuit SCUBA diving.  .  .  .  .  .  .  .  . 1-9, 1-10, 7-2, 7-7
Operating procedures
approval process .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 4-3
format.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 4-3
nonstandardized. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 4-2, 4-3
standardized. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 4-2

U.S. Navy Diving Manual

Operational Risk Management
combat swimmer missions.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 6-6
course of action analysis/risk assessment.  .  .  .  . 6-13
defined.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 6-14
demolition missions .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2C-14
diver training and qualification requirements.  .  . 6-3, 6-7
enclosed space diving .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2C-12
Environmental Assessment Worksheet.  .  .  .  .  . 2C-10
environmental hazards.  .  .  .  .  .  .  .  .  .  .  .  .  . 2C-1, 2C-10
explosive ordnance disposal .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 6-5
process. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 6-14
salvage/object recovery.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 6-4
sea state. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2C-1, 2C-4
search missions.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 6-3
security dives.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 6-5
surface conditions .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2C-1, 2C-3
underwater construction.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 6-4, 6-7
underwater construction planning resources.  .  .  . 6-5
Underwater Ship Husbandry .  .  .  .  .  .  .  .  .  .  .  . 6-2, 6-3
OPs. See Operating procedures
ORCA. See Oxygen Regulator Console Assembly
ORM. See Operational Risk Management
OSF. See Ocean Simulation Facility
Oxygen
deficiency.  .  .  .  .  .  .  .  .  . 3-12, 3-13, 15-25, 16-3, 5B-7
properties of.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-15
purity standards.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 4-5, 4-6
Oxygen convulsion
closed-circuit oxygen UBA diving.  .  .  .  .  .  . 16-2, 16-3
helium-oxygen dives. . . . . . . . . . . . . . . 12-16, 12-19
symptoms of.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-38, 9-39
treatment of .  .  .  .  .  . 9-38, 9-39, 12-16, 12-17, 12-19
Oxygen flask endurance.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-7, 15-8
Oxygen Regulator Console Assembly.  .  .  .  .  .  . 8-21, 8-22
Oxygen toxicity
causes of .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 10-2, 10-3
in chamber.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 12-19
helium-oxygen dives. . . . . . . . . . . . . . . 12-15, 12-19
Electronically Controlled Closed-Circuit UBA.  .  . 15-1
off-effect.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-26
prevention of. . . . . . . . . . . . . . . . . . . . . . . . . . 15-26
during recompression chamber treatment.  .  .  . 17-26
SCUBA diving. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-11, 1-12
symptoms.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-44
treatment of .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-24, 15-26

P
Paralytic shellfish poisoning .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-20
Parasitic infestation.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-21
Partial pressure.  .  .  .  .  . 2-24, 2-32, 2-33, 3-10, 3-12, 3-20

Index

Pasley, Colonel William.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-5
Pearl Harbor
salvage diving. . . . . . . . . . . . . . . . . . . . . . . . . . 1-29
PEL. See Permissible Exposure Limit
Peripheral nervous system .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-1, 3-2
Permissible Exposure Limit.  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1A-1, 1A16
Personal dive log.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5-4, 9-4
Personnel Transfer Capsule .  .  .  .  .  .  .  .  . 1-24, 1-25, 13-22
Physics
atoms.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-1
elements. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-1
energy .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-4, 2-5
formulas.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-32
gas laws.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-17, 2-24
gas measurements. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-3
gas mixtures.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-24, 2-36
gases in diving.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-14, 2-16
heat energy in diving .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-10, 2-11
light energy in diving. . . . . . . . . . . . . . . . . . . 2-5, 2-6
measurement systems.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-2, 2-3
mechanical energy in diving.  .  .  .  .  .  .  .  .  .  .  . 2-6, 2-10
molecules.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-1, 2-2
pressure in diving.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-11, 2-14
states of matter. . . . . . . . . . . . . . . . . . . . . . . . . . 2-2
symbols and values.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-31
temperature measurements.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-3
Physiology
circulatory system. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-2, 3-5
nervous system .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-1, 3-2
respiratory system .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-5, 3-10
Planned Maintenance System. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 4-3
PMS. See Planned Maintenance System
Pneumofathometers .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 4-15, 9-49
PNS. See Peripheral nervous system
Poisonous marine animals .  .  .  .  .  .  .  .  .  .  .  .  . 5C-18, 5C-21
Portable monitor-defibrillator.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-36
Portuguese man-of-war.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-9, 5C-10
Potential energy. . . . . . . . . . . . . . . . . . . . . . . . . 2-5, 7-27
Power equivalents.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-35
Pressure
absolute pressure.2-12, 2-17, 2-18, 2-20, 2-22, 2-27
Archimedes’ Principle. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-13
atmospheric pressure. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-12
barometric pressure.  .  .  .  .  .  .  .  .  .  .  .  . 3-11, 4-11, 9-52
buoyancy .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-13
definition of.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-11
depth, pressure, atmosphere graph.  .  .  .  .  .  .  .  .  . 2-37
diver buoyancy.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-13, 2-14
equivalents.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-33
formulas.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-32
gauge pressure .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-12
hydrostatic pressure.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-12, 2-13
measurement of.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-11
partial pressure. . . . . . . . . . . . . . . . 2-24, 2-25, 2-32
pressure chart .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-13
symbols and values.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-31

Index–9

Pressure gradient .  .  .  .  .  .  .  .  .  .  .  .  . 2-30, 3-46, 3-49, 3-59
Pressure points.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5B-1, 5B-7, 5C-1
Pressure waves.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-7, 2-8
Primary emergency kits.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-36, 17-37
Program administration. See Dive program
administration
PSP. See Paralytic shellfish poisoning
PTC. See Personnel Transfer Capsule
Pufferfish poisoning.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-19
Pulmonary oxygen toxicity
closed-circuit oxygen UBA diving.  .  .  .  .  .  .  .  .  .  .  . 19-4
Electronically Controlled Closed-Circuit UBA.  .  . 15-1
during recompression chamber treatment.  .  .  . 17-25

R
Radiation.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-10
Rankine scale .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-3
RCF. See Recompression Chamber Facility
Reciprocating air compressors .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 4-11
Recompression Chamber Facility.  .  .  .  .  .  .  .  .  .  .  .  .  .  .
17-22, 17-28, 18-2, 18-3
Recompression Chamber Log. .  .  .  .  .  .  .  .  .  . 5-1, 5-3, 17-3
Recompression chambers
access to occupants. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-25
air supply requirements .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 18-16
carbon dioxide control .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-23
central nervous system oxygen toxicity. . 17-26, 17-27
components of.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 18-2, 18-3
description .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 18-2, 18-14
diver candidate pressure test.  .  .  .  .  .  .  . 18-30, 18-31
double-lock steel chamber.  .  .  .  .  .  .  .  .  .  .  . 18-3, 18-4
Emergency Evacuation Hyperbaric Stretcher . . 18-4
equalizing during descent. . . . . . . . . . . . . . . . 17-25
fire hazard prevention. . . . . . . . . . . . . . 18-29, 18-30
Fleet Modernized Double-Lock Recompression
Chamber.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 18-3
Fly Away Recompression Chamber.  .  .  .  .  .  .  .  .  . 18-4
gag valves .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 18-20
gas supply .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 18-15, 18-17
history of. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-6, 1-7
inside tenders.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-28, 17-29
life-support considerations.  .  .  .  .  .  .  .  .  . 17-22, 17-28
line guide .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 18-5
lock-in operations.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 18-20
lock-out operations.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 18-20
loss of oxygen during treatment.  .  .  .  .  . 17-27, 17-28
maintenance. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 18-23, 18-30
manning requirements.  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-1, 17-6
Navy support levels .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 6-20, 18-1
operating procedures.  .  .  .  .  .  .  .  .  .  .  .  .  . 18-17, 18-23
oxygen control .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-23
patient hydration. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-24, 17-25
postdive checklist.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 18-23
predive checklist. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 18-17
pressure test. . . . . . . . . . . . . . . . . . . . . 18-30, 18-31

Index–10

pulmonary oxygen toxicity .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-27
Recompression Chamber Facility.  .  .  .  .  .  .  .  .  .  .  .  . 18-3
requirements .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 18-1
safety precautions .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 18-17
stainless steel chambers .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 18-29
standard features.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 18-4, 18-6
Standard Navy Double Lock Recompression
Chamber System .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 18-3
state of readiness.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 18-15
temperature control .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-23, 17-24
tender change-out .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 18-20
transfer lock.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 18-13
Transportable Recompression Chamber
System .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 18-3, 18-4
treatment at altitude.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-28
use of high oxygen mixes. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-25
ventilation.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 18-20, 18-21
Recompression treatments. See also
Recompression chambers
air treatment tables. . . . . . . . . . . . . . . . . . . . . 17-17
with chamber .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-14
death during treatment.  .  .  .  .  .  .  .  .  .  .  .  . 17-31, 17-32
emergency air evacuation of patients. . . . . . . 17-30
flying after treatments. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-29
guidance for.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-14
hyperbaric oxygen therapy.  .  .  .  .  .  .  .  .  . 17-21, 17-22
in-water. . . . . . . . . . . . . . . . . . . . . . . . . 17-16, 17-17
mechanical failures. . . . . . . . . . . . . . . . . . . . . 17-32
for non-diving disorders.  .  .  .  .  .  .  .  .  .  .  . 17-21, 17-22
non-standard treatments .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-31
objectives.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-14
observation period.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-28, 17-29
with oxygen .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-26
oxygen breathing.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-25
post-treatment considerations .  .  .  .  .  .  . 17-28, 17-30
preventing early surfacing .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-20
residual symptoms treatment.  .  .  .  .  .  .  .  .  .  .  .  .  . 17-30
returning to diving after treatment .  .  .  .  .  .  .  .  .  . 17-30
rules for .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-10
tenders.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-20
transporting patients. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-15
treatment abort procedures .  .  .  .  .  .  .  .  . 17-31, 17-32
treatment tables.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-17, 17-21
when oxygen is not available.  .  .  .  .  .  .  . 17-14, 17-15
without recompression chamber .  .  .  .  .  .  .  .  .  .  . 17-15
Record keeping. See also Diving charts
air decompression .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-4, 9-6
mixed gas operational planning.  .  .  .  .  . 12-25, 12-26
Red Tide .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-20
References .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1B-1, 1B-3
Refraction .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-5
Remotely Operated Vehicles.  .  .  .  .  .  .  .  .  .  .  .  . 2C-2, 2C-14
Repetitive dives
Air EC-UBA dives.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-30
defined.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-3
diving charts.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-26, 9-28

U.S. Navy Diving Manual

Electronically Controlled Closed-Circuit UBA.  .  .
15-17, 15-19
flow chart .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-22
nitrogen-oxygen diving.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 10-1
order of.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-30, 9-31
procedure.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-23, 9-29
Residual Nitrogen Time .  .  .  .  . 9-25, 9-29, 9-49, 9-59
worksheet.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-24
Repetitive group designation tables .  .  .  .  .  .  .  .  .  .  .  .  .
2A-2, 9-8, 9-9, 9-63, 15-36, 15-37, 15-48, 1549, 15-66, 15-67
Repetitive group designator. . . . . . . . . . . . . . . . . . . . 9-3
Repetitive nitrogen time. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-3
Residual helium timetable.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15-49
Residual nitrogen. . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-3
Residual Nitrogen Time.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-3
Respiratory cycle.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-8
Respiratory dead space. . . . . . . . . . . . . . . . . . . . . . . 3-9
Respiratory minute volume.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-9
Respiratory quotient .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-9
Respiratory rate.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-8
Respiratory system physiology
alveolar/capillary gas exchange.  .  .  .  .  .  .  .  .  .  .  .  .  . 3-9
chest cavity. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-6
gas exchange.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-5
lower respiratory tract. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-6
lungs. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-6, 3-8
respiration phases .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-5, 3-6
upper respiratory tract .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-6
ventilation definitions .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-8, 3-9
Risk assessment
defined.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 6-13, 6-14
Risk management. See Operational Risk Management
Risks
defined.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 6-14
RNT. See Residual Nitrogen Time
Rouquayrol, Benoist .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-9
ROV. See Remotely Operated Vehicles

S
SAC. See System Certification Authority
Salvage diving.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-29, 1-30
Salvage/object recovery
mission objective .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 6-4
submarine salvage and rescue .  .  .  .  .  .  .  . 1-26, 1-29
Saturation diving
advantages of. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-21, 1-22
Bond’s saturation theory. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-22
components of.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-1, 13-6
continuing research .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-24
Deep Diving Systems.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-1
developmental testing .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-22
diver life-support systems. . . . . . . . . . . . . . . . . 13-8
Genesis Project .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-22
Sealab programs .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-22, 1-24

Index

U.S. Navy facilities.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-7, 13-8
Scombroid fish poisoning .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-19, 5C-20
Scorpionfish. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-7, 5C-8
SCUBA diving. See also Surface-Supplied Diving
Systems; Underwater breathing apparatus
authorization for navy use .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-1
buoyancy compensators .  .  .  .  .  .  .  .  .  .  .  .  . 7-14, 7-15
closed -circuit.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-10, 1-11
cold water diving. . . . . . . . . . . . . . . . . . . . 11-3, 11-4
cylinders.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-11
demand regulator assembly.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-8
equipment requirements. . . . . . . . . . . . . . . 7-7, 7-17
face masks.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-13, 7-14
history of. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-8, 1-9
impact of. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-10
knives.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-16
life preservers. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-28, 7-29
mouthpiece. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-10
octopus. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-10
open-circuit. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-9, 1-10, 7-7, 7-8
oxygen toxicity.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-11, 1-12
semiclosed-circuit. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-12, 1-13
weight belts .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-15, 7-16
World War II use. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-13, 1-15
SDC. See Submersible Decompression Chamber
Sea, Air and Land special warfare teams
training and missions.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-14, 1-15
Sea blubber.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-9, 5C-11
Sea cucumbers.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-21
Sea level equivalent depth .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-48
Sea lions.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-5, 5C-6
Sea nettles. . . . . . . . . . . . . . . . . . . . . . . . . . 5C-9, 5C-11
Sea snakes.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-16, 5C-17
Sea state.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2C-1
Sea urchins.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-14, 5C-15
Sea wasps.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-9, 5C-11
Sealab programs.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-22, 1-24
SEALs. See Sea, Air and Land special warfare teams
Search missions .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 6-3
Secondary emergency kits .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-36
Security swims. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 6-5
Segmented worms. . . . . . . . . . . . . . . . . . . 5C-13, 5C-14
Self-contained underwater breathing apparatus. See
SCUBA diving
Semiclosed-circuit SCUBA diving.  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-12
Shallow water diving tables.  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2A-1, 2A-3
Sharks.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-1, 5C-3
Shock
treatment of .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5-B7
SI system. See International System of Units
Siebe, Augustus. . . . . . . . . . . . . . . . . . . . . . . . . . 1-4, 1-8
Siebe’s Improved Diving Dress.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-4
Single dive.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-3
Smith, J. Lorrain .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-11, 1-12
Solubility
of gases.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-29
Sonar

Index–11

safe diving distances from.  .  .  .  .  .  .  .  .  .  . 1A-1, 1A-16
Sound .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-7
Sound Pressure Level.  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1A-1, 1A-3, 2-7
SPCCs. See Strength, power, and Communications
cables
SPL. See Sound Pressure Level; Sound pressure level
Sponges .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-17
SRC. See Submarine Rescue Chamber
SSDS. See Surface-Supplied Diving Systems
Stage depth.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-2
Staggers .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-12
Standard Navy Double Lock Recompression
Chamber System.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 18-3
States of matter.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-2
Steroids.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17-34
Stillson, Chief Gunner George D. .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-26
Stingrays.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-8, 5C-9
Stonefish.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-7, 5C-8
Submarine Rescue Chamber .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-28
Submarine salvage and rescue.  .  .  .  .  .  .  .  .  .  .  . 1-26, 1-29
Submersible Decompression Chamber. .  .  .  .  . 1-20, 1-21
Surface air supply systems
air compressors.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 4-11, 4-13
air supply requirements .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-7
high-pressure air cylinders and flasks .  .  .  .  .  .  .  . 4-14
operating and emergency procedures.  .  .  .  .  .  .  .  . 4-3
primary and secondary air supply .  .  .  .  .  .  .  .  .  .  . 8-25
supply pressure standards.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-17
water vapor control. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 4-13
Surface decompression. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-37, 8-38
Surface decompression on oxygen.  .  .  .  .  .  .  .  . 9-15, 9-21
Surface interval.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-3
Surface-Supplied Diving Systems. See also SCUBA
diving; Surface-supplied air diving; Underwater
breathing apparatus
KM-37 NS. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-7, 8-14
MK 12.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-8, 1-9
MK 21.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-8
MK 12 Mixed-Gas. . . . . . . . . . . . . . . . . . . . . . . 1-20
MK 20.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-14, 8-15
portable .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-15, 8-20
Surface-Supplied Mixed Gas Diving
charting. . . . . . . . . . . . . . . . . . . . . . . . . 12-25, 12-26
diving at altitude.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 12-26
helium-oxygen descent and ascent procedures. .
.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 12-4, 12-12
helium-oxygen emergency procedures. . 12-12, 12-25
modern surface-supplied mix-gas diving.  .  .  .  .  . 1-19
operational considerations.  .  .  .  .  .  .  .  .  .  .  . 12-1, 12-3
System Certification Authority.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 4-3

T
Telephone numbers.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1C-1
Temperature
equivalents.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-36

Index–12

measurements.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-3
symbols and values.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-31
“The bends.” See Decompression sickness
Thomson, Elihu.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-16
Tidal volume .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-8
TMDER. See Technical Manual Deficiency/
Evaluation Report
Total decompression time
defined.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-2
Total lung capacity.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-8
Total time of dive
defined.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 9-2
Tourniquets .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5B-4, 5B-6
Transmitting sonar
safe diving distances from.  .  .  .  .  .  .  .  .  .  . 1A-1, 1A-16
Transportable Recompression Chamber System.  .  .  .
.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 18-3, 18-4
TRCS. See Transportable Recompression Chamber
System
Turbidity. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-6

U
UBA. See Underwater breathing apparatus
UDTs. See Underwater Demolition Teams
Ultrasonic sonar. . . . . . . . . . . . . . . . . . . . . . . . . . . 1A-16
Unconsciousness .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-20
Underwater breathing apparatus. See also
Electrolically Controlled Closed-Circuit UBA;
SCUBA diving; Surface-Supplied Diving Systems
closed-circuit oxygen diving.  .  .  .  .  .  .  .  .  . 16-1, 16-21
design of. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13-7
MK 6.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-12, 1-13
MK 20 MOD 0 Surface-Supplied Diving System.
.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-13, 8-15
Underwater construction.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 6-6
Underwater Demolition Teams
training and missions.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-15
Underwater explosions
degree of submersion of diver.  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-9
distance from explosion.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-8, 2-9
estimating explosion pressure on diver .  .  . 2-9, 2-10
location of explosive charge.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-8
minimizing effects of. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-10
seabed characteristics.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-8
size of charge.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-8
type of. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-8
water depth. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-8
Underwater mobile sound communications sets.  .  .  . 13-4
Underwater physics. See Physics
Underwater procedures
adapting to conditions .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-30
bottom checks .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-33
damage to helmet and diving dress.  .  .  .  .  .  .  .  .  . 8-35
enclosed space diving .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2C-12

U.S. Navy Diving Manual

falling .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-35
fouled descent lines.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-34
fouled umbilical lines .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-34
monitoring diver’s movements.  .  .  .  .  .  .  .  .  .  .  .  .  . 8-36
movement on the bottom.  .  .  .  .  .  .  .  .  .  .  .  . 8-30, 8-31
safety procedures. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-32, 8-33
searching on the bottom. .  .  .  .  .  .  .  .  .  .  .  .  . 8-31, 8-32
tending the diver. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-35, 8-36
Underwater Ship Husbandry procedures.  .  .  .  .  .  . 6-3
working around corners.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-32
working inside a wreck.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-31
working near lines or moorings .  .  .  .  .  .  .  . 8-32, 8-33
working with tools.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-33, 8-34
Underwater Ship Husbandry.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 6-2, 6-3
UQC. See Underwater mobile sound
communications sets
U.S. Military Diver’s Breathing Air Standards .  .  .  .  .  . 8-15
USS F-4. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-26, 1-27
USS Lafayette.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-29, 1-30
USS Oklahoma.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-29
USS S-4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-27
USS S-51. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-27
USS Squalus.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-28
USS Thresher.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-28, 1-29
UWSH. See Underwater Ship Husbandry

Work equivalents.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-35
World War II
salvage diving. . . . . . . . . . . . . . . . . . . . . . 1-29, 1-30
use of SCUBA diving .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-13, 1-15

Z
Zebrafish.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-7, 5C-8
Zetterstrom, Arne. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-18, 1-19

V
Variable Volume Dry Suits.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-18
Variable volume dry suits
cold water diving. . . . . . . . . . . . . . . . . . . . . . . . .11-7
Velocity equivalents.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-34
Venomous marine animals .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-6, 5C-18
Ventilation, inadequate .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1-7
Vertigo.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 12-22, 12-23
Vietnam War
salvage diving. . . . . . . . . . . . . . . . . . . . . . . . . . 1-30
Viral shellfish diseases .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-20, 5C-21
Vital capacity.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 3-8
Volume
equivalents.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-33
formulas for .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-32

W
Water depth
sound and. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-7
Water entry/descent .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 8-26
Water temperature
sound and. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-7
Water turbidity.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2-6, 5-8
Weeverfish. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5C-6, 5C-7
Weight belts. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7-51
Wet suits
cold water diving. . . . . . . . . . . . . . . . . . . . . . . . .11-7

Index

Index–13



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