NOAA Diving Manual : For Science And Technology Dive 1991
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Diving manual DIVING FOR SCIENCE AND TECHNOLOGY U.S. DEPARTMENT OF COMMERCE l GKtfER&TY "WW* Digitized by the Internet Archive in 2012 with funding from LYRASIS Members and Sloan Foundation http://archive.org/details/noaadivingmanualOOunit NOAA DIVING MANUAL DIVING FOR SCIENCE AND TECHNOLOGY October 1991 z 5i s "T J c SrAT ES O* U.S. ^ DEPARTMENT OF COMMERCE Robert A. Mosbacher, Secretary National Oceanic and Atmospheric Administration John A. Knauss, Under Secretary Oceanic and Atmospheric Research Ned A. Ostenso, Assistant Administrator Office of Undersea Research David B. Duane, Director Mention of a commercial company or product does not constitute an endorsement by NOAA. Use for publicity or advertising purposes of information from this publication concerning proprietary products or the use of such products is not authorized. No photograph appearing in this publication may be reproduced in any fashion without prior written permission from NOAA. Information contained in this May 1990. Manual was current as of Library of Congress Cataloging in Publication Data United States. National Oceanic and Atmospheric Administration. Office of Undersea Research. NOAA diving manual. Bibliography: p. Includes index. 1. I. A Diving, Scientific. publication Changes cally; 2. Hyperbaric Physiology. Title. is of value only if it is check your original source for Updates kept up to date. to this publication will be issued periodi- will also all updates. be available through the Superin- tendent of Documents. TABLE OF CONTENTS V vii ix xiii xxi SECTION 1 SECTION 2 SECTION 3 SECTION 4 SECTION 5 SECTION 6 FOREWORD PREFACE CONTRIBUTORS LIST OF FIGURES LIST OF TABLES HISTORY OF DIVING PHYSICS OF DIVING DIVING PHYSIOLOGY COMPRESSED AIR AND SUPPORT EQUIPMENT DIVER AND DIVING EQUIPMENT HYPERBARIC CHAMBERS AND SUPPORT EQUIPMENT SECTION 7 SECTION 8 SECTION 9 AND SUPPORT PERSONNEL TRAINING WORKING DIVE PROCEDURES PROCEDURES FOR SECTION 10 SCIENTIFIC DIVES DIVING UNDER SPECIAL SECTION SECTION 11 SECTION SECTION 13 14 SECTION 15 DIVER CONDITIONS 12 POLLUTED-WATER DIVING HAZARDOUS AQUATIC ANIMALS WOMEN AND DIVING AND DECOMPRESSION MIXED GAS AND OXYGEN AIR DIVING DIVING SECTION SECTION 16 17 SECTION SECTION 18 19 SATURATION DIVING SECTION 20 UNDERWATER SUPPORT PLATFORMS EMERGENCY MEDICAL CARE ACCIDENT MANAGEMENT AND EMERGENCY PROCEDURES DIAGNOSIS AND TREATMENT APPENDIX A OF DIVING CASUALTIES DIVING WITH DISABILITIES 111 APPENDIX B APPENDIX C NAVY AIR DECOMPRESSION TABLES TREATMENT FLOWCHART AND RECOMPRESSION TREATMENT TABLES U.S. APPENDIX D NOAA NITROX DIVING AND DECOMPRESSION APPENDIX E GLOSSARY I TABLES REFERENCES INDEX IV FOREWORD NOAA, the largest component of the Department of Commerce, an agency with a broad mission is mental monitoring, prediction, and understanding of the oceans and the atmosphere. systems agency" because studies the relationship between the natural it important duties we perform is I components of our call NOAA planet. in environ- the "earth Among the most the monitoring of the oceans and Laurentide Great Lakes. NOAA operates a variety of sensors and platforms that permit observation and measurement of change in the and Great Lakes. We operate satellites, ships, and submersibles, as well as the world's only underwater seas habitat. To add a uniquely human dimension to ocean research and marine services, NOAA conducts wet diving operations throughout the Great Lakes, the territorial sea, the U.S. Exclusive Economic Zone, and wherever the agency is involved in marine operations and research. NOAA — more than 250 men and technicians who dive under the auspices of NOAA-sponsored research grants, a factor that significantly increases that number.) As befits the variety of their missions, NOAA's divers are scientists, engineers, technicians, and officers in the NOAA Corps, and all have volunteered to be divers. numbers among its staff the largest diving and women. (This number does not include those Because the tasks NOAA NOAA complement of any civil Federal agency civilian scientists, engineers, divers carry out are as varied as those of any group of underwater workers in the world, — — Diving Manual greatly expanded and revised contains instructions, recommendaand general guidance on the broadest possible range of underwater living conditions and dive situations. Thus, while the Manual is directed toward NOAA, it will be useful, as were previous editions, to working divers who have other affiliations and to those who dive for pleasure only. this version of the tions, Under authority delegated by the Secretary of Commerce, NOAA takes seriously the mandate under Section 21(e) of the Outer Continental Shelf Lands Act Amendments of 1978 to "conduct studies of underwater diving ." techniques and equipment suitable for protection of human safety and improvement in diver performance . NOAA is proud of its record of safe diving and the assistance it . . has provided to the diving community. To continue that record, the Manual has been revised to incorporate recommendations and information obtained from the entire diving community. The various issues addressed and the procedures recommended reflect the wisdom, experience, and specialized skills of working and recreational divers, equipment manufacturers, medical and scientific authorities, and many others. Under ordinary circumstances, the guidance in this mission and a failure. In an extreme situation, however, those who contributed assistance in making to this revision, this revision of the I Manual could mean the difference between a it could make the difference between life and express, on behalf of Manual a truly useful all document of NOAA, my deep appreciation for all divers. John A. Knauss Under Secretary of Commerce for Oceans and Atmosphere successful death. To for their 1 PREFACE This Manual NOAA has been developed for use by divers. are shallower than 250 feet (76 m), the depth range in which focuses principally on diving to depths that It NOAA divers generally operate. Other sources should be referred to for information on deep-water mixed-gas diving procedures. this Manual Manual contains been used liberally to keep This version of the to a manageable As in previous versions, references many changes from the first and second editions. Immediately noticeable the loose-leaf format, which will greatly facilitate revision and additions. This format will permit the updated no matter how large or small the section needing revision, Manual This edition of the 7 are largely Manual to is be e.g., a section, a paragraph, or a single table. Of these units, 6 are new, 12 have has 25 distinct parts: 20 sections and 5 appendixes. undergone major revision, and have size. unchanged, as noted below: New: Section 1 Section 1 History of Diving Polluted-Water Diving Section 13 Women Appendix A Appendix C Appendix E Diving With Disabilities and Diving Treatment Flowchart and Recompression Treatment Tables Glossary Substantially revised: Section 7 Compressed Air and Support Equipment Diver and Diving Equipment Hyperbaric Chambers and Support Equipment Diver and Support Personnel Training Section 9 Procedures for Scientific Dives Section 4 Section 5 Section 6 Section 10 Diving Under Special Conditions Section 14 Air Diving and Decompression Section 15 Section 19 Mixed Gas and Oxygen Diving Emergency Medical Care Accident Management and Emergency Procedures Section 20 Diagnosis and Treatment of Diving Casualties Section 18 Appendix NOAA D Nitrox I Diving and Decompression Tables Largely unchanged: Physics of Diving Section 2 Section Diving Physiology 3 Section 12 Working Dive Procedures Hazardous Aquatic Animals Section 16 Saturation Diving Section 17 Underwater Support Platforms U.S. Navy Air Decompression Tables Section 8 Appendix B Although the recommendations and guidelines contained in this Manual are based on the best information judgment and expert opinion or to restrict the application of science and technology that may become available in the future. NOAA also recognizes that some procedures may have to be modified under controlled experimental conditions to permit the advance of science. Because the information in this Manual reflects the thinking and experience of many specialists in the field of diving, procedural variations available, they are not intended to replace should be As made only on the basis of expert advice. stated above, this responsibilities are the Manual has been developed for NOAA's divers, whose missions are varied but whose chief conduct of oceanic and Great Lakes research and the support of such research activities. vn NOAA also recognizes that this Manual will be useful for others who dive because The information it contains a wealth of Manual, however, should not be taken to reflect any endorsement or approbation on the part of NOAA or its Undersea Research Program for any products illustrated, nor can either accept any liability for damage resulting from the use of incorrect or incomplete information on applied diving techniques and technology. in this information. The multidisciplinary nature of underwater exploration and research is such that the assistance of numerous experts in diving-related specialties was essential to the preparation of this Manual. number of individuals involved in the task, the reader is referred to the list To gain an appreciation of the of contributors and reviewers for this and previous editions. Special thanks go to all of these contributors and reviewers, but particular gratitude is extended to: the NOAA Diving Safety Board for its review and comments; Dr. Morgan Wells for his very thorough editing, including checking of tables and example problem calculations throughout; Dr. James W. Miller for numerous helpful suggestions, but especially for accepting the task of producing the Glossary; Marthe Kent, whose persistence, knowledge, and attention to detail drove the entire process; and Marcia Collie, who had to translate everyone's handwritten notes to intelligible and intelligent prose, cross-check every draft through to galley and the final page proofs, and in general to see to production. Comments on this Manual are welcome. They should be directed to: Director NOAA's Undersea Research Program, 1335 East-West Highway, Silver Spring, R/OR2 Room 5262 Maryland 20910 David B. Director Vlll Duane, CONTRIBUTORS AND REVIEWERS Bachrach, Arthur J., Breese, Dennison Ph.D. New Mexico Taos, Sea-Air-Land-Services Southport, North Carolina Bangasser, Susan, Ph.D. Redlands, California Busby, Frank Busby Associates Barsky, Steven Arlington, Virginia Diving Systems International Santa Barbara, California Butler, Glenn Underwater Contractors, New York International Bassett, Bruce, Ph.D. Human Underwater Biology, San Antonio, Texas City Island, Inc. Clark, James Inc. M.D., Ph.D. D., Environmental Medicine University of Pennsylvania Medical Center Philadelphia, Pennsylvania Bauer, Judy Institute for Hyperbaric Medicine Program University of Florida Gainesville, Florida Clarke, Richard E., George C, Lt. Col., M.C., USAF Lackland Air Force Base, Texas Bell, Bell, M.D. Department of Hyperbaric Medicine Richland Memorial Hospital Columbia, South Carolina Richard, Ph.D. Department of Chemical Engineering Clifton, H. Edward, Ph.D. University of California Geological Survey Davis, California United States Department of the Interior Bennett, Peter, Ph.D. Menlo Park, California Duke Medical Center Durham, North Carolina Berey, Richard Cobb, William F. Northwest and Alaska Fisheries Center National Oceanic and Atmospheric Administration Pasco, Washington W. Fairleigh Dickinson University National Undersea Research Center National Oceanic and Atmospheric Administration St. Croix, Corry, James A. U. S. Virgin Islands Technical Security Division Department of Treasury Black, Stan Naval Port Civil Engineering Washington, D.C. Laboratory Hueneme, California Crosson, Dudley Bornmann, Robert, M.D. Limetree Medical Consultants J., Ph.D. Harbor Branch Oceanographic Institution, Inc. Fort Pierce, Florida Reston, Virginia Daugherty, C. Gordon, M.D. Bove, Alfred, M.D. Austin, Texas Temple University Davis, Jefferson Philadelphia, Pennsylvania C, M.D. Hyperbaric Medicine Affiliations, titles, and academic degrees are as they were was made. the time contribution at Southwest Texas Methodist Hospital San Antonio, Texas IX Contributors and Reviewers Desautels, David Halstead, Bruce Hyperbaric Medicine Program World University of Florida Colton, California W. Life Research Institute Gainesville, Florida Dingier, John R. Hamner, William M., Ph.D. Department of Biology Geological Survey University of California U.S. Department of the Interior Los Angeles, California Menlo Park, California Hamilton, R.W., Ph.D. Dinsmore, David A. Hamilton Research Ltd. University of North Carolina at Wilmington Tarrytown, New York National Undersea Research Center National Oceanic and Atmospheric Administration Heine, John N. Wilmington, North Carolina Moss Landing Marine Laboratory California State University Eckenhoff, Roderic G., M.D. Moss Landing, California Wallingford, Pennsylvania Hendrick, Walter, Edel, Peter Sea Space Research Co., Harvey, Louisiana Inc. Department of Kinesiology Los Angeles, California Emmerman, Michael Lifeguard Systems, Inc. York, New York C, Farmer, Joseph New York, New York Hennessy, T. R., Ph.D. Egstrom, Glen, Ph.D. New Jr. Lifeguard Systems, Inc. London, U.K. High, William L. Western Administrative Support Center National Marine Fisheries Services National Oceanic and Atmospheric Administration Seattle, Washington M.D. Jr., Edmund Division of Otolaryngology Hobson, Duke University Medical Center Durham, North Carolina Tiburon Laboratory Southwest Fisheries Center National Oceanic and Atmospheric Administration Feldman, Bruce A., M. D. Tiburon, California Washington, D.C. Hollien, Harry, Ph.D. Fife, William, Ph.D. A& Texas M University College Station, Texas Flynn, Edward T., Advanced Study Communication Processes Institute for Hyperbaric Laboratory of University of Florida Gainesville, Florida M.D., Hubbard, Dennis, Ph.D. Capt., Medical Corps West USN Fairleigh Dickinson University Diving Medicine Department Naval Medical Research Institute Indies Laboratory St. Croix, Virgin Islands National Naval Medical Center Hussey, Nancy R. Bethesda, Maryland Washington, D.C. Francis, Art, Lt. (j-g-), NOAA NOAA Diving Office Rockville, Maryland Jenkins, Wallace T. Naval Coastal Systems Laboratory Panama City, Florida Graver, Dennis National Association of Underwater Instructors Kent, Marthe B. Montclair, California Kensington, Maryland Contributors and Reviewers Ann Kinney, Jo Surry, S., Newell, Cliff Ph.D. Maine Chief, Diving Operations National Oceanic and Atmospheric Administration Lambertsen, Christian Institute for M.D. J., Seattle, Washington Environmental Medicine Norquist, David S. University of Pennsylvania University of Hawaii Philadelphia, Pennsylvania National Undersea Research Center Lanphier, Edward H., Ph.D. National Oceanic and Atmospheric Administration BIOTRON Waimanalo, Hawaii University of Wisconsin Orr, Madison, Wisconsin Dan Academic Diving Program Lewbel, George, Ph.D. Florida State University LGL Tallahassee, Florida Ecological Research Associates Bryan, Texas Pegnato, Paul, Lt. Cdr., NOAA Loewenherz, James W., M.D. National Oceanic and Atmospheric Administration Miami, Florida Long, Richard NOAA Diving Program Maryland Rockville, W. Pelissier, Michael Diving Unlimited International, Inc. Ocean Technology Systems San Diego, California Santa Ana, California NOAA Macintyre, Ian G., Ph.D. Peterson, David H., Lt. Cdr., Department of Paleobiology National Oceanic and Atmospheric Administration Museum National of Natural History Maryland Rockville, Smithsonian Institution Peterson, Russell, Ph.D. Washington, D.C. Westchester, Pennsylvania Mathewson, R. Duncan, Summerland Key, III, Ph.D. Phoel, William C, Ph.D. Sandy Hook Laboratory Florida Northeast Fisheries Center Mayers, Douglas, M.D., MC, Naval Medical Command Naval Medical Research Bethesda, Maryland USN Institute National Marine Fisheries Service National Oceanic and Atmospheric Administration Highlands, New Jersey Reimers, Steve, P.E. McCarthy, James Reimers Engineering Navy Experimental Diving Unit Panama City, Florida Alexandria, Virginia Miller, James W., Ph.D. Big Pine Key, Florida Robinson, Jill Jill Robinson & Associates Arlington, Virginia Rogers, Wayne, M.D. Miller, John N., M.D. University of South Mobile, Big Pine Key, Florida Alabama Alabama Roman, Charles M. Office of NOAA Corps Operations Murray, Rusty National Oceanic and Atmospheric Administration Moray Wheels Rockville, Maryland Nahant, Massachusetts Rounds, Richard Murru, Frank Curator of Fishes Sea World West Orlando, Florida St. Croix, Indies Laboratory Fairleigh Dickinson University National Undersea Research Center U. S. Virgin Islands XI Contributors and Reviewers Rutkowski, Richard L. Hyperbarics International Thompson, Terry Ocean Images, Inc. Miami, Florida Berkeley, California Schroeder, William W., Ph.D. Thornton, Marine Science Program Texas Research University of Alabama Dauphin Island, Alabama Austin, Texas Schane, William, M. D. Geological Survey J. Scott, Ph.D. Institute, Inc. Valentine, Page, Ph.D. West Indies Laboratory Fairleigh Dickinson University United States Department of the Interior Woods Hole, Massachusetts National Undersea Research Center St. Croix, U. S. Virgin Islands Vorosmarti, James, Rockville, Jr., M.D. Maryland Somers, Lee, Ph.D. Department of Atmospheric and Oceanic Sciences University of Michigan Ann Arbor, Michigan Walsh, Michael, Ph.D. National Institute on Drug Abuse U.S. Public Health Service Rockville, Maryland Spaur, William, M.D. Norfolk, Virginia Waterman, Stanton A. East/West Film Productions, Staehle, Michael Lawrenceville, New Inc. Jersey Staehle Marine Services, Inc. North Palm Beach, Florida Webb Stanley, Chet NOAA Diving Safety Officer Rockville, Webb, Maryland Paul, M.D. Associates Yellow Springs, Ohio Wells, Morgan, Ph.D. Stewart, James R., Ph.D. NOAA Diving Program Maryland Scripps Institution of Oceanography Rockville, La Wicklund, Robert Jolla, California Stewart, Joan, Ph.D. Scripps Institution of Oceanography La I. National Undersea Research Center Jolla, California Caribbean Marine Research Center Lee Stocking Island, Bahamas Stone, Richard B. Wilkie, Donald W., Ph.D. National Marine Fisheries Service Scripps Institution of Oceanography National Oceanic and Atmospheric Administration University of California Silver Spring, Maryland Strauss, Michael B., M.D. Memorial Medical Center of Long Beach Long Beach, California Swan, George Northwest and Alaska Fisheries Center National Marine Fisheries Service National Oceanic and Atmospheric Administration Pasco, Washington xn La Jolla, California Williscroft, Robert, Ph.D. Williscroft Manuscripts Dayton, Washington Workman, Ian Southeast Fisheries Center Pascagoula Facility National Oceanic and Atmospheric Administration Pascagoula, Mississippi 1 1 LIST OF FIGURES SECTION 1 HISTORY OF DIVING Page l-l Breath-Hold Pearl Divers 1-2 Alexander the Great's Descent Into The Sea 1-3 Halley's Diving Bell, 1690 1-3 1-4 Triton Diving Apparatus 1-4 1-5 Rouquayrol-Denayrouse Semi-Self- 1-2 ... Contained Diving Suit 1-6 1-5 Fernez-Le Prieur Self-Contained Diving Apparatus 1-7 1-3 World War II 1-5 Military Swimmer Dressed in Lambertsen Amphibious Respiratory Unit 1-6 SECTION 2 PHYSICS OF DIVING 2-1 Equivalent Pressures, Altitudes, and Depths 2-2 Effects of Hydrostatic Pressure 2-3 Boyle's 2-4 Gas Laws Objects Under Water Appear Closer 2-5 .... 2-4 2-5 Law 2-9 2-12 2-13 SECTION 3 DIVING PHYSIOLOGY 3-1 3-2 3-3 3-4 The Process of Respiration The Circulatory System Oxygen Consumption and Respiratory Minute Volume as a Function of Work Rate Relation of Physiological Effects to Carbon 3-1 3-3 3-4 Dioxide Concentration and Exposure Period 3-5 3-6 Effects of Hydrostatic Pressure on Location of Breathing Bags Within a Closed-Circuit Scuba 3-9 3-6 Principal Parts of the Ear 3-1 3-7 Location of Sinus Cavities 3-12 3-8 Lung Volume Complications From Expansion of Air 3-13 3-9 Pressure Effects on in the Lungs During Ascent 3-15 3-10 Isobaric Counterdiffusion 3-19 3-1 Effect of Exposure Duration on Psychomotor Task Performance in Cold Water 3-26 xiii — A List of Figures Page SECTION 4 COMPRESSED AIR AND SUPPORT EQUIPMENT 4-1 Production of Diver's Breathing Air 4-6 4-2 Steel Cylinder Markings 4-7 4-3 Aluminum Cylinder Markings 4-8 4-4 Valve Assemblies 4-11 4-5 Gauges 4-12 SECTION 5 DIVER AND DIVING EQUIPMENT 5-1 Open-Circuit Scuba Equipment 5-1 5-2 First-Stage Regulators 5-3 5-3 Breathing Hoses 5-4 5-4 5-5 5-5 Mouthpieces Check and Exhaust Valves 5-6 Lightweight Helmet 5-8 5-7 Face Masks 5-12 5-8 Flotation Devices 5-13 5-9 Swim 5-14 5-10 5-15 5-13 Neoprene Wet Suit Effects of Water Temperature Cold- Water Mitt, Liner Included Open-Circuit Hot-Water Suit 5-14 Snorkels 5-19 5-15 Dive Timer 5-20 5-16 5-20 5-17 Depth Gauges Pressure Gauges 5-18 Diving Lights 5-23 5-19 Signal Devices 5-23 5-20 Shark Darts Shark Screen in Use Diver Communication System Schematics of Diver Communication Systems Modulated Acoustic Communication System... 5-25 5-11 5-12 5-21 5-22 5-23 5-24 5-6 Fins 5-16 5-17 5-18 5-22 . 5-25 5-26 5-26 5-27 SECTION 6 HYPERBARIC CHAMBERS AND SUPPORT EQUIPMENT 6-2 Double-Lock Hyperbaric Chamber Exterior View Double-Lock Hyperbaric Chamber Interior View Mask Breathing System for Use in Hyperbaric 6-3 Transportable Chambers 6-4 Certification Plate for Hyperbaric 6-5 Burning Rates of Filter Paper Strips Angle of 45° in N -0 Mixtures 6-1 6- IB 6-1 6-2 Chamber 6-3 2 xiv 2 6-4 Chamber at .... 6-4 an 6-15 List of Figures Page Combustion in N->-Ot Mixtures Showing the Zone of No Combustion 6-6 SECTION 6-16 7 DIVER AND SUPPORT PERSONNEL TRAINING No Figures SECTION 8 WORKING DIVE PROCEDURES Deep-Sea Dress 8-1 Surface-Supplied Diver 8-2 Predive Environmental Checklist 8-3 Lightweight Surface-Supplied 8-4 Surface-Supplied Diver In Lightweight 8-5 8-6 in 8-2 8-3 Mask 8-4 Mask and Wet Suit Major Components of a Low-Pressure Compressor-Equipped Air Supply System Typical High-Pressure Cylinder Bank Air Supply System 8-5 .... 8-10 8-10 8-12 8-7 Circular Search Pattern 8-8 Circular Search Pattern for 8-9 Circular Search Pattern Through Ice 8-14 8-10 Arc 8-15 8-11 Jackstay Search Pattern 8-12 Searching Using a 8-13 8-17 8-15 Diver-Held Sonar Using a Compass for Navigation Underwater Hydraulic Tools 8-16 Explosive Hole Punch 8-22 8-17 8-22 8-21 Oxy-Arc Torch Salvaging an Anchor With Lift Bags Aquaplane for Towing Divers Underwater Cameras Basic Equipment for Closeup and Macro 8-22 Diurnal Variation of Light Under Water 8-23 Selective Color Absorption of Light as a 8-24 Lighting 8-25 8-26 Video Recording Systems Commercial Underwater Video System SECTION 9 Two Diver/Searchers 8-14 8-18 8-19 8-20 (Fishtail) 8-12 Search Pattern Tow Bar Photography 8-16 8-18 8-21 8-26 8-30 8-33 8-34 Function of Depth Arms and 8-16 in Clear Ocean Water 8-35 8-36 Brackets for Strobe Systems 8-40 8-45 8-46 PROCEDURES FOR SCIENTIFIC DIVES Tape 9-3 9-1 Fiberglass Measuring 9-2 Bottom Survey in High-Relief Terrain High-Frequency Sonic Profiler 9-3 9-3 9-4 Multipurpose Slate 9-6 9-5 xv List of Figures Page 9-5 Counting Square for Determining Sand Dollar 9-8 Density 9-6 Diver-Operated Fishrake 9-8 9-7 Underwater Magnification System Hensen Egg Nets Mounted on a Single Diver 9-9 9-8 9-9 Propulsion Vehicle 9-9 A Circle Template for Determining Benthic 9-10 Population Density 9-1 Coring Device With Widemouth Container Infauna Sampling Box 9-12 Use of a Hand-Held Container 9-13 Use of 9-10 9-10 9-1 to Collect Zooplankton 9-12 a Plexiglas Reference Frame for Estimating Population Densities in Midwater 9-13 9-14 Benthic Environment of the American 9-15 Diver With Electroshock Grid 9-15 9-16 Tagging a Spiny Lobster on the Surface Tagging a Spiny Lobster in Situ Elkhorn Coral Implanted on Rocky Outcrop Algal Cover of Rock Substrate Diver in Giant Brown Kelp (Macrocystis) Bed Fish Using Tires as Habitat An Artificial Reef Complex Underwater Geological Compass Box Cores (Senckenberg) for Determining 9-15 9-14 Lobster 9-17 9-18 9-19 9-20 9-21 9-22 9-23 9-24 Internal Structure in Sand 9-17 .... 9-19 9-18 9-21 9-21 9-23 9-25 9-34 Greased Comb for Ripple Profiling Diver Using Scaled Rod and Underwater Noteboard Aerial Photograph and Composite Map Dip and Strike of Rock Bed Geologist Measuring Dip (Inclination) of Rock Outcrop Coring in a Deep Reef Environment With a Hydraulic Drill Pneumatic Hand Drill Diver Taking Vane Shear Measurement Undersea Instrument Chamber Dye-Tagged Water Being Moved by Bottom 9-35 Diver Using Water Sample Bottle 9-36 Water Sample 9-37 Diver Recovering Indian Artifacts 9-37 9-38 Archeologist Exploring the Golden Horn 9-38 9-39 Heavy Overburden Air Lift Prop Wash System Used for Archeological 9-39 9-40 9-41 Fish Trap 9-42 9-42 Diver Checking Fish Trawl 9-43 9-43 Slurp 9-25 9-26 9-27 9-28 9-29 9-30 9-31 9-32 9-33 9-26 9-26 9-27 9-28 9-28 9-28 9-29 9-31 9-32 9-35 Current Bottle Backpack Gun Used 9-36 9-36 9-41 Excavation xvi 9-16 .... to Collect Small Fish 9-45 1 List of Figures Page SECTION DIVING 10 UNDER SPECIAL CONDITIONS lO-l Schematic Diagram of Waves in the Breaker Zone 10-8 10-2 Near-shore Current System 10-3 Shore Types and Currents 10-4 Entering the Water Using the Roll-In 10-5 10-7 Transom-Mounted Diver Platform Side-Mounted Diver Platform Down-line Array for Open-Ocean Diving 10-8 Three Multiple Tether Systems (Trapezes) 10-9 Safety Reel Used 10-6 Used 10-10 lO-l Method 10-1 Open-Ocean Diving in Cave Diving Water Temperature Protection Chart Diver Tender and Standby Diver in Surface 10-12 Cross Section of a Typical Hydroelectric 10-10 for Shelter Dam in the Northwestern United States Diver Protected by Cage and Ready to be 10-14 A 10-16 10-12 10-13 10-15 10-16 10-18 10-20 10-21 10-13 10-15 l 10-12 Lowered into Dam Gatewell Fish Ladder at a Hydroelectric Dam in the Northwest Creeper A Device Used to Move Across Rocky Substrates in Strong Currents 10-29 10-30 10-30 — 10-32 Support Ship, Trawl, Diver Sled, and Support Boat 10-35 SECTION 11 POLLUTED-WATER DIVING ll-l Diver Working in Contaminated Water Dry Suit 1 1-2 Diver 1 1-3 NOAA-Developed Suit-Under-Suit (SUS) 1 1-4 Dressing a Diver for Contaminated-Water in System Diving 11-5 Decontamination SECTION 12 Team at Work 11-2 1 1-4 1 1-5 1 1-5 11-6 HAZARDOUS AQUATIC ANIMALS 12-2 Sea Urchin Echinothrix diadema on Hawaiian Reef Stinging Hydroid 12-3 Stinging or Fire Coral 12-2 12-4 Portuguese Man-of-War 12-3 12-5 Large Jellyfish of Genus Cyanea Bristleworm 12-3 12-4 12-8 Cone Shell Anatomy of 12-9 Rare Australian Blue-Ring Octopus l 2-1 12-6 12-7 a Cone Shell a 12-1 12-2 12-4 12-5 12-5 xvn 1 1 List of Figures Page 12-10 Dasyatid Stingray 12-6 12-1 Myliobatid Stingray 12-6 12-12 Lionfish 12-7 12-13 Surgeonfish 12-7 12-14 12-8 12-16 Sea Snake Great White Shark Gray Reef Shark 12-17 Moray Eel 12-10 12-18 Barracuda 12-11 12-19 12-12 12-20 Torpedo Ray Examples of Pufferfish SECTION 13 12-15 12-8 12-9 12-12 WOMEN AND DIVING 13-1 SECTION Scientist on Research Mission 13-5 14 AIR DIVING AND DECOMPRESSION 14-1 Sea States 14-2A Hand 14-2B Additional 14-3 Deliverable Volumes at Various 14-4 Typical High Pressure Cylinder Bank Air 14-5 Repetitive Dive Flowchart 14-25 14-6 Repetitive Dive Worksheet 14-26 14-5 14-10 Signals Hand Signals 14-1 Gauge 14-16 Pressures Supply 14-18 SECTION 15 MIXED GAS AND OXYGEN DIVING 15-1 Minimum Safe Inspired Gas Temperature 15-5 Limits 15-2 Percentage of Oxygen as a Function of in Breathing Mixtures Depth and Oxygen Partial Pressure Relative to Ranges for Hypoxia and CNS Toxicity 15-3 Closed-Circuit Mixed-Gas Scuba 15-4 Closed-Circuit (Rebreather) 15-1 15-5 Oxygen Scuba (Rebreather) Air Analysis Kit for On-Site Use 15-14 15-6 Direct-Reading Colorimetric Air Sampler 15-15 SECTION 16 SATURATION DIVING No xviii 15-6 Figures 15-1 List of Figures Page SECTION 17 UNDERWATER SUPPORT PLATFORMS Complex 17-1 Saturation Diving 17-2 Open Diving 17-3 17-4 17-9 System Open Bell Showing Control Lines Open Bell Emergency Flow-Chart Cutaway Showing Mating Position With Deck Decompression Chamber Undersea Habitat Specifications and Operational Data Edalhab Hydrolab 17-10 Tektite 17-14 17-11 La Chalupa 17-15 17-12 Aegir 17-16 17-13 17-17 17-15A Underwater Classroom Aquarius Sublimnos 17-15B Subigloo 17-19 17-15C 17-19 17-15D Lake Lab Undersea Instrument Chamber 17-16 Diver Propulsion Vehicle 17-20 17-17 JIM System 17-21 17-18 17-19 WASP System ROV System Components 17-22 17-20 Mitsui Engineering and Shipbuilding 17-21 Examples of SECTION 18 17-4 17-5 17-6 17-7 17-8 17-14 Bell 17-2 on Deck of Seahawk Bell 17-3 17-5 17-6 17-7 17-8 17-12 17-13 17-17 17-18 17-19 17-21 RTV-100 17-23 ROV David Work Tasks 17-23 EMERGENCY MEDICAL CARE 18-1 Life-Support Decision Tree 18-2 Jaw-Lift 18-3 Bag-Valve-Mask Resuscitator 18-2 Method 18-4 18-6 SECTION 19 ACCIDENT MANAGEMENT AND EMERGENCY PROCEDURES 19-1 Buddy Breathing Mask 19-2 Clearing a Face 19-3 Do-Si-Do Position for 19-6 19-8 Administering In-Water Mouth-to-Mouth Artificial Resuscitation 19-1 19-4 Mouth-to-Mouth In-Water 19-5 Mouth-to-Snorkel Artificial Resuscitation 19-6 Towing Artificial Resuscitation Position for Mouth-to-Snorkel Artificial Resuscitation 19-7 19-12 19-13 Tank-Tow Method 19-14 19-18 xix List of Figures Page (DAN) 19-8 Divers Alert Network 19-9 19-24 19-10 Modified Trendelenberg Position Diving Accident Management Flow Chart 19-11 Evacuation by Helicopter 19-27 19-22 19-25 SECTION 20 DIAGNOSIS AND TREATMENT OF DIVING CASUALTIES 20-1 Structure of External, Middle, and Inner Ear 20-2 Summary 20-3 20-4 20-5 xx 20-8 of Decompression Sickness and Gas Embolism Symptoms and Signs Decompression Sickness Treatment From Diving or Altitude Exposures Treatment of Arterial Gas Embolism Treatment of Symptom Recurrence 20-10 20-12 20-14 20-16 1 LIST OF TABLES SECTION 1 HISTORY OF DIVING No p age Tables SECTION 2 PHYSICS OF DIVING 2-1 Conversion Factors, Metric 2-2 Conversion Table for Barometric Pressure 2-3 Colors That Give Best Visibility Against a to English Units.... 2-2 2-3 Units Water Background 2-16 SECTION 3 DIVING PHYSIOLOGY Carboxyhemoglobin 3-1 as a Function of Smoking 3-8 Narcotic Effects of Compressed Air Diving 3-2 SECTION 4 COMPRESSED AIR AND SUPPORT EQUIPMENT Composition of Air 4-1 SECTION 3-22 in its Natural State 4-1 5 DIVER AND DIVING EQUIPMENT No Tables SECTION 6 HYPERBARIC CHAMBERS AND SUPPORT EQUIPMENT 6-1 Hyperbaric Chamber Predive Checkout 6-5 Procedures 6-2 Ventilation Rates and Total Air Requirements for Two Patients and One Tender Undergoing Recompression Treatment 6-8 6-3 Chamber 6-4 Pressure Test Procedures for Post-Dive Maintenance Checklist NOAA Chambers 6-5 Standard NOAA 6-9 6-1 Recompression Chamber Air Pressure and Leak Test 6-12 xxi List of Tables Page SECTION 7 DIVER AND SUPPORT PERSONNEL TRAINING No Tables SECTION 8 WORKING DIVE PROCEDURES 8-1 Wind Speed and Current 8-2 Diver Power Tools 8-3 Selection Guide for Discharge Pipe and 8-4 Characteristics of Principal U.S. Explosives 8-5 Color Correction Filters 8-6 Manual and Through-the-Lens (TTL) 8-7 Through-the-Lens (TTL) Mini Strobes for Automatic and Manual Exposure Exposure Compensation for Underwater 8-38 8-8 Photography Underwater Photographic Light Sources Still Films Suited for Underwater Use Processing Adjustments for Different Speeds Motion Picture Films Suited for Underwater Use 8-38 Estimations Air Line Used for Demolition Purposes Strobes for Closeup Photography 8-9 8-10 8-1 8-12 SECTION 8-11 8-19 8-28 8-32 8-36 8-37 8-39 8-41 8-42 8-43 9 PROCEDURES FOR SCIENTIFIC DIVES 9-1 Micro-Oceanographic Techniques 9-33 9-2 Levels of Anesthesia for Fish 9-44 9-3 Fish Anesthetics 9-47 SECTION DIVING 10-1 10-2 10-3 10 UNDER SPECIAL CONDITIONS Comparison of Differences in Time Limits (in Minutes of Bottom Time) for No-Decompression Dives Theoretical Ocean Depth (TOD) (in fsw) at Altitude for a Given Measured Diving Depth 10-25 Pressure Variations with Altitude 10-27 SECTION 11 POLLUTED-WATER DIVING No xxii Tables 10-26 List of Tables Page SECTION 12 HAZARDOUS AQUATIC ANIMALS No Tables SECTION 13 WOMEN AND DIVING No Tables SECTION 14 AIR DIVING AND DECOMPRESSION 14-1 Sea State Chart 14-6 14-2 Signal Flags, Shapes, and Lights 14-9 14-3 Hand 14-12 14-4 Line Pull Signals for Surface-to-Diver 14-5 Respiratory Minute 14-6 Air Utilization Table at Depth 14-15 14-7 Cylinder Constants 14-16 14-8 Scuba Cylinder Pressure Data Signals Communication Different 1 4-9 14-13 Volume (RMV) at Work Rates 14-14 Estimated Duration of 7 1 .2 ft 3 14-17 Steel 14-17 Cylinder 14-10 Flow-Rate Requirements for SurfaceSupplied Equipment 14-19 14-1 No-Decompression Limits and Repetitive Group Designation Table for NoDecompression Air Dives 14-21 1 14-12 Residual Nitrogen Timetable for Repetitive 14-13 Optional Oxygen-Breathing Times Before Air Dives 14-22 Flying After Diving 14-31 SECTION 15 MIXED GAS AND OXYGEN DIVING 15-1 Oxygen Partial Pressure and Exposure Time Limits for Nitrogen-Oxygen Mixed Gas 15-2 1 5-3 15-4 Working Dives Depth-Time Limits for Breathing Pure Oxygen During Working Dives NOAA NITROX-I (68% N 2 32% 2 ) No- 15-3 15-7 , Decompression Limits and Repetitive Group Designation Table for NoDecompression Dives Equivalent Air Depths (EAD) and Maximum Oxygen Exposure for Open-Circuit Scuba 15-8 68% 32% Oxygen (NOAA Using a Breathing Mixture of Nitrogen and Nitrox-I) 15-5 Air Purity Standards 15-9 15-11 xxiii List of Tables Page SECTION 16 SATURATION DIVING Summary 16-1 of Air and Nitrogen-Oxygen Saturation Exposures 16-2 Characteristics of Three 16-2 Carbon Dioxide Absorbents 1 6-3 Hazardous Materials SECTION 16-10 for Habitat Operations 16-14 17 UNDERWATER SUPPORT PLATFORMS 17-1 Desirable Features of Underwater Habitats SECTION 17-1 18 EMERGENCY MEDICAL CARE No Tables SECTION 19 ACCIDENT MANAGEMENT AND EMERGENCY PROCEDURES 19-1 Summary of Probable Causes of Non- Occupational Diving Fatalities from 1976-1984 19-5 19-2 Sources of Emergency Assistance 19-21 19-3 Ground-to-Air Visual Signal Code 19-23 19-4 Diving Casualty Examination Checklist 19-26 SECTION 20 DIAGNOSIS AND TREATMENT OF DIVING CASUALTIES 20-1 Characteristics of Inner Ear Barotrauma and 20-2 List of U.S. 20-3 Tables General Patient Handling Procedures Inner Ear Decompression Sickness xxiv 20-5 Navy Recompression Treatment 20-1 20-15 Page SECTION 1 HISTORY OF 1.0 General 1.1 Free (Breath-Hold) Diving 1-1 DIVING 1.2 Diving Bells 1-1 1.3 1-2 1.4 Helmet (Hard-Hat) Diving Scuba Diving 1.5 Saturation Diving 1-6 1.6 1-1 1-3 1.5.1 Saturation Diving Systems 1-6 1.5.2 Habitats 1-7 1.5.3 Lockout Submersibles 1-7 Summary 1-7 ( ( HISTORY OF DIVING 1.0 GENERAL the bar of a weighted line to plunge to this depth and Divers have penetrated the oceans through the centuries for held his breath for 3 minutes and 39 seconds. The obvious advantage purposes identical to those of modern diving: to acquire food, search for treasure, carry out military of free diving as a work (and as a recreational method) is operations, perform scientific research and explora- freedom of the breath-hold diver and enjoy the aquatic environment. In a brief history of diving, Bachrach (1982) identified five principal periods in the history of diving, from free (or obvious disadvantage tion, breath-hold) diving, to bell diving, surface support or helmet (hard hat) diving, scuba diving, and, finally, saturation diving. (Atmospheric diving, another div- mode, is discussed in Section 17.5.) All of these diving modes are still currently in use. ing limited to the maintain FREE (BREATH-HOLD) DIVING Free diving, or breath-hold diving, diving techniques, and it snorkel book, all in The Hae-Nyu and Korea and Japan (Figure pearl divers of among 1-1) are the better-known breath-hold divers. In his Half Mile Down, Beebe (1934) is an aid reports finding in it fills necessarily is can take air the diver and in breath or can obtain by means of a The modern breath-hold diving but is not used because on descent to provide a continuous supply of air, with water that must then be exhaled on surfacing. DIVING BELLS The second the earliest of has played an historic role the search for food and treasure. Ama is amount of in a single maneuver; the to that the air supply snorkel-type reed or tube to the surface. 1.2 1.1 is method mobility and the its diving. One principal historical mode of diving bell is of the earliest reports of the use of a device some that enabled a diver to enter the water with degree of protection and a supply of air involved the Colimpha used in Alexander the Great's approximately 330 B.C., depicted by an Indian artist in a 1575 miniature (Figure 1-2). An diving bell descent in several mother-of-pearl inlays in the course of con- account of ducting an archeological dig at a Mesopotamia site manuscript, The True History of Alexander. In his Problemata, Aristotle described diving systems in use that dated back to 4500 B.C.; these shells must have been gathered by divers and then fashioned into inlays in by artisans of the period. Beebe also describes the extensive use of pearl shells among people from other divers, ancient cultures. The Emperor of China, for example, this dive his time: appeared "they contrive a means of respiration for by means of a container sent naturally the container which constantly received an oyster pearl tribute around 2250 B.C. Free In the Greek historian Thucydides that in According to an Athenian attack which the Athenian divers cut through underwater barriers that the Syracusans had built to on Syracuse in obstruct and damage Greek Rome on his shoulders hold divers sometimes used hollow reeds as breathing by slings. remain submerged for type of primitive snorkel was use- tubes, which allowed longer periods; this ful in military them to operations (Larson 1959). Free diving continues to be a major diving method. set in 1969 by a U.S. Navy diver, Robert Croft, who made a breath-hold dive to 247 feet World records were (75 meters), a record broken in 1976 by a French diver, Jacques Mayol, who set the current world's breath- hold dive record at 325 feet (99 meters). October 1991 — NOAA Diving Manual Mayol grasped was not bell. a until device that can Davis (1962) about an hour 1535 of a tells in a lake near using de Lorena's diving apparatus, which rested ships. Free or breath- the for air, few this period, very Guglielmo de Lorena developed who worked them; to submerged man." in diving. It be considered a true diving diver down not filled with water, but 1000 years following developments occurred reports. is assists the divers were also used in military operations, as the Thucydides, divers participated 13th century French in the De and had much of its weight supported Lorena's "bell" thus provided a finite but reliable air supply. In 1691, the British astronomer Sir Edmund Halley (who was then Secretary of the Royal Society) built and patented a forerunner of the modern diving bell, which he later described in a report to the Society. As Sir Edmund described it, the bell was made of wood coated with lead, was approximately 60 cubic feet (1.7 cubic meters) in volume, and had glass at the top to allow light to enter; there was also a valve to 1-1 Section 1 Figure 1-1 Breath-Hold Pearl Divers Photos courtesy Suk 1.3 (Figure 1-3). In his history of diving, Davis (1962) suggests that Halley undoubtedly knew of a develop- Although these early diving to provide air from the surface to a diving bell pressure. Papin proposed to use force to pumps under or bellows provide air and to maintain a constant pressure bell. Davis speculates that Halley's choice within the of the barrel rather than forced air method of replenishment may have reflected Halley's concern that Papin (who was also a Fellow of the Royal Society) would accuse him of stealing his concept. Halley's method was used for over a century until Smeaton introduced a successful forcing pump in 1788. In 1799, Smeaton dived with his "diving chests," which used a forcing pump to replenish the air supply Diving bells continue to be used today as part of modern diving systems, providing a method of transporting divers to their work sites while under pressure and, once at the site, of supplying breathing gas while the diver works. Both modern-day open (or "wet") and bells provided some protection and an air supply, they limited the mobility and 18th centuries, a number of of leather) were developed to provide air to divers and to afford greater mobility. However, most of these devices were not successful, because they relied on long tubes from the surface to provide air to the diver and thus did not deal with the problem of equalizing pressure at depth. The first real step toward the development of a surfacesupported diving technique occurred when the French scientist Freminet devised a system in which air was of the diver. In the I7th devices (usually pumped from made the surface with a bellows, allowing a constant flow of air to pass through a hose to the diver in the water. (Larson 1959). Hong HELMET (HARD-HAT) DIVING vent the air and a barrel to provide replenished air ment reported by the French physicist Denis Papin, who in 1689 had proposed a plan (apparently the first) Ki the first This system is considered by many to be true helmet-hose diving apparatus. Freminet has been credited with diving in 1774 with this device to a depth of 50 feet (15 meters), where he remained for a period of The first 1 hour. major breakthrough in surface-support closed bells are clearly the successors of these ancient diving systems occurred with Augustus Siebe's inven- systems. tion of the diving dress in 1819. 1-2 NOAA Around the same Diving Manual time, — October 1991 History of Diving Figure 1-2 Figure 1-3 Halley's Diving Alexander the Great's Descent Into The Sea Courtesy National Academy of suit that would allow firefighters to work in a burning building. They received a patent for this system in 1823, and later modified it to 1690 Sciences Deane Brothers, John and Charles, were working the on a design for a "smoke apparatus," a Bell, "Deane's Patent Diving Dress," consisting Courtesy National particular helium-oxygen, were developed. Sciences The first the USS Squalus, in The breathing 1939. of mixed gases such as helium-oxygen permitted divers to dive depths for longer periods than had been to greater with ports and hose connections for surface-supplied possible with air mixtures. Siebe's diving dress consisted of a waist-length of major open-sea use of helium and oxygen as a breathing mixture occurred in the salvage of the submarine, of a protective suit equipped with a separate helmet air. Academy supported diving technique is The hard-hat surfaceprobably still the most received air under pressure from the surface by force widely used commercial diving method; the use of heliox mixtures and the development of improved decom- pump; pression tables have extended the diver's capability to jacket with a metal helmet sealed to the collar. Divers the air subsequently escaped freely at the diver's waist. In 1837, Siebe modified this open dress, which work in this diving dress at depth. Although surface- allowed the air to escape, into the closed type of dress. supported diving has several advantages The closed stability, air supply, suit retained the attached helmet but, by venting the air via a valve, provided the diver with a full-body air-tight suit. This suit served as the basis for modern hard-hat diving was tested and found to gear. Siebe's diving suit be successful in 1839 when the British started the salvage of the ship George, which had sunk in 1782 to a until — NOAA contained underwater breathing apparatus (scuba). depth of 65 feet major developments occurred in hard-hat gear the 20th century, when mixed breathing gases, in October 1991 certain dive situations by the development of self- Royal (19.8 meters) (Larson 1959). No in terms of and length of work period, a major problem with hard-hat gear is that it severely limits the diver's mobility. This limitation has been overcome in Diving Manual 1.4 SCUBA DIVING The development of self-contained underwater breathing apparatus provided the free moving diver with a portable 1-3 Section 1 Figure 1-4 Triton Diving Apparatus supply which, although finite air in comparison with the unlimited air supply available to the helmet diver, allowed for mobility. Scuba diving quently used ous forms, work mode is is the most fre- in recreational diving and, in vari- perform underwater and commercial purposes. also widely used to for military, scientific, There were many steps cessful self-contained in the development of a suc- underwater system. In 1808, Freiderich von Drieberg invented a bellows-in-a-box device (Figure 1-4) that was worn on the diver's back from the surface. This work but it did serve to suggest that compressed air could be used in diving, an idea initially conceived of by Halley in 1716. In 1865, two French inventors, Rouquayrol and Denayrouse, developed a suit (Figure 1-5) that they described as "self-contained." In fact, their suit was not self contained but consisted of a helmet-using surface-supported system that had an air reservoir that was carried on the diver's back and was sufficient to provide one breathing cycle on demand. The demand valve regulator was used with surface supply largely and delivered compressed device, named air Triton, did not actually because tanks of adequate strength were not then available to handle air at high pressure. This system's demand which was automatically controlled, represented a major breakthrough because it permitted the diver to valve, air when needed in an emergency. The Rouquayrol and Denayrouse apparatus was described with remarkable accuracy in Jules Verne's classic, Twenty Thousand Leagues Under The Sea, which was written in 1869, only 4 years after the inventors had have a breath of made their device public (Larson 1959). The demand valve played a critical part in the later development of one form of scuba apparatus. However, since divers using scuba gear exhaled directly into the surrounding water, much air was wasted. One solution problem was advanced by Henry Fleuss, an English merchant seaman who invented a closed-circuit breathing apparatus in 1879 that used pure oxygen compressed to 450 psig for the breathing gas supply to this and caustic potash to purify the exhaled oxygen. Fleuss' "closed circuit oxygen-rebreather when SCUBA" passed a was used successfully in 1880 by the English diver Alexander Lambert to enter a flooded tunnel beneath the Severn River to secure an iron door that had jammed open and to make needed repairs in the tunnel. Although Fleuss' rebreather was successful in this limited application, the depth limitations associated with the use of pure oxygen directed most attention to compressed air as a breathing mixture. crucial test it In the 1920's, a French naval officer, Captain Yves Le Prieur, 1-4 began work on a self-contained air diving Courtesy National Academy of Sciences apparatus that resulted in 1926 in the award of a patent, shared with his countryman Fernez. This device (Figure 1-6) was a steel cylinder containing compressed air that was worn on the diver's back and had an air hose connected to a mouthpiece; the diver wore a nose clip and air-tight goggles that undoubtedly were protective and an aid to vision but did not permit pressure equalization. The cylinder on the first FernezLe Prieur model contained around 2000 psi of air and permitted the wearer to remain less than 15 minutes in the water. Improved models later supplied sufficient air to permit the diver to remain for 30 minutes at 23 feet (7 meters) or 10 minutes at 40 feet (12 meters). The major problem with Le Prieur's apparatus was the lack of a demand valve, which necessitated a continuous flow (and thus waste) of gas. In 1943, almost 20 years after Fernez and Le Prieur patented their apparatus, two other French inventors, Emile Gagnan and Captain Jacques-Yves Cousteau, demonstrated their "Aqua Lung." This apparatus used a demand intake valve drawing from two or three cylinders, each containing over 2500 psig. Thus it was that the demand regulator, invented over 70 years earlier by Rouquayrol and Denayrouse and extensively used in aviation, came into use in a self-contained breathing apparatus that did not emit a wasteful flow of air during inhalation NOAA Diving Manual — October 1991 History of Diving Figure 1-5 Rouquayrol-Denayrouse Semi-Self-Contained Figure 1-6 Diving Suit Fernez-Le Prieur Self-Contained Diving Apparatus Courtesy National Academy Sciences of Equivalent self-contained apparatus was used by the military forces of Italy, the United States, and Great World War II and continues in active The rebreathing principle, which avoids Britain during use today. waste of gas supply, has been extended to include forms of scuba that allow the use of mixed gas (nitrogen or helium-oxygen mixtures) tion depth and dura- to increase beyond the practical oxygen limits of air or pure breathing (Larson 1959). A major development occurred in in regard to mobility France during the 1930's: Carlieu developed a set of swim Courtesy National (although it Academy Sciences of continued to lose exhaled gas into the made possible the develop- water). This application ment of modern open-circuit air scuba gear (Larson In 1939, Dr. Christian Lambertsen began the devel- opment of a series of three patented forms of oxygen rebreathing equipment for neutral buoyancy underwater swimming, which became the first self-contained under- water breathing apparatus successfully used by a large number of divers. piratory Unit The Lambertsen Amphibious Res- (LARU) (Figure 1-7) formed the basis for the establishment of U.S. military self-contained diving (Larson 1959). This apparatus was designated scuba (for contained underwater breathing apparatus) by October 1991 — NOAA Diving Manual its selfusers. diving de the first to be produced since Borelli designed a pair of claw-like fins in 1680. When used with Le Prieur's tanks, goggles, and nose clip, de Carlieu's fins enabled divers to move horizontally through the water like true swimmers, instead of being lowered vertically in a diving bell or in hard-hat gear. 1959). fins, in Commander The later use of a single-lens face which allowed better visibility as well zation, also increased the mask, as pressure equali- comfort and depth range of diving equipment. Thus the development of scuba added a major work- ing tool to the systems available to divers; the mode allowed new freedom of movement and access to greater depths for extended times and required much less burdensome support equipment. Scuba also enriched the world of sport diving by permitting recreational divers to go beyond goggles and breathhold diving to more extended dives at greater depths. divers greater 1-5 Section 1 Figure 1-7 World War Military Swimmer Dressed in Lambertsen Amphibious Respiratory Unit II decompression obligation in the course of such The initial development of saturation diving by the U.S. Navy in the late 1950's and its extension by naval, civilian government, university, and commertial dives. cial laboratories revolutionized scientific, commercial, and military diving by providing a method that permits divers to remain at pressures equivalent to depths of up 2000 feet (610 meters) for periods of weeks or months without incurring a proportional decompres- to sion obligation. Saturation diving takes advantage of the fact that a diver's tissues become saturated once they have absorbed the nitrogen or other inert gas they can hold at that all particular depth; that tional gas. Once is, they cannot absorb any addi- a diver's tissues are saturated, the diver can remain at the saturation depth (or a depth within an allowable excursion range up or down from the saturation depth) as long as necessary without proportionately increasing the amount of time required for decompression. mode work Divers operating in the saturation out of a pressurized facility, such as a diving bell, seafloor habitat, or diver lockout submersible. facilities These subsea are maintained at the pressure of the depth at which the diver be working; this depth will termed is the saturation or storage depth. The historical development of saturation diving depended both on technological and scientific advances. Engineers developed the technology essential to support the saturated diver, and physiologists and other scientists defined the respiratory capabilities and limits of this and other physiological mode. Many researchers played essential roles in the development of the saturation Navy team working at Submarine Medical Research Laboratory concept, but the U.S. London, Connecticut, is the U.S. in generally given credit for New making team was led by two Navy diving medical officers, George Bond and Robert Workman, who, in the period from the mid-1 950's to 1962, supervised the painstaking animal tests and volunteer human dives that provided the major initial breakthroughs in this field. This the scientific evidence necessary to confirm the valid- Courtesy C. J. Lambertsen ity of the saturation concept (Lambertsen 1967). 1.5.1 Saturation Diving Systems The 1.5 SATURATION DIVING Although the development of surface-supplied diving permitted divers to spend a considerable amount of earliest saturation dive performed in the open sea was conducted by the Link group and involved the use of a diving bell for diving and for decompression. Initial Navy efforts involved placing a saturation hab- working time under water, divers using surface-supplied on the seafloor. In 1964, Edwin Link, Christian Lambertsen, and James Lawrie developed the first systems for deep and/or long dives incurred a substan- deck decompression chamber, which allowed divers 1-6 itat NOAA Diving Manual in — October 1991 History of Diving a sealed bell to be locked into a pressurized environ- ment at the surface for the slow decompression from The first commercial application of this form of saturation diving took place on the Smith Mountain Dam project in 1965 and involved the use of a personnel transfer capsule. The techniques pioneered at Smith Mountain have since become standard in comsaturation. mercial diving operations: saturated divers pressure, in the deck decompression live, a surface vessel and are then transferred to the under- water worksite in a pressurized personnel transfer cham- ber (also called a surface decompression chamber) (Lambertsen 1967). Although saturation diving systems are the most widely used saturation systems in commercial diving today, two other diving technologies also take advantage of the principle of saturation: habitats technologically advanced habitat system, has replaced the Hydrolab and lockout submersibles. as NOAA's principal seafloor research 1.5.3 Lockout Submersibles Lockout submersibles provide an alternative method for diver/scientists to gain access to the underwater environment. Lockout submersibles are dual-purpose vehicles that permit the submersible's pilot/driver crew to remain at surface pressure 1 at which saturated diver-scientists live and work under pressure for extended periods of time. Habitat divers dive from the surface and enter the habitat, or they may be compressed in a pressure vessel on the surface to the pressure of the habitat's storage depth and then be transferred to the habitat. Decompression may take place on the seafloor or in a surface decompression chamber after the completion of the divers' work. The most famous and widely used habitat was NOAA's Hydrolab, which was based in the Bahamas and Caribbean from 1972 to 1985 and provided a base for more than 600 researchers from 9 countries during that time. In 1985, the Hydrolab was retired from service and now resides permanently in the Smithsonian Insti- — NOAA and at a pressure of is pressurized separate compartment to the pressure of the depth which he or she will be working. The lockout com- in effect as a personnel transfer and from the seafloor. The Johnson Sea-Link, which can be pressurized Habitats are seafloor laboratory/living quarters in October 1991 (i.e., atmosphere), while the diver-scientist in a capsule, transporting the diver to Habitats discus- sion of habitat-based in-situ research programs.) partment thus serves 1.5.2 more detailed laboratory. (See Section 17 for a under chamber on board Museum of Natural History in WashThe Aquarius, a more flexible and tution's National ington, D.C. Diving Manual 2000 fsw (610 msw), has played a central role in undersea research program for years, particularly pollution 1.6 and to NOAA's in fisheries research off the Atlantic coast. SUMMARY Humans have explored the ocean depths at least since the fifth millennium B.C., and the development of the diving techniques and systems described in this section reflects mankind's drive for mastery over The search all aspects methods that will allow humans to live comfortably in the marine biosphere for long periods of time continues today, as engineers and scientists work together to make access to the sea safer, easier, and more economical. of the environment. for 1-7 ( ( 1 Page SECTION 2 PHYSICS OF 2.0 General 2-1 2.1 Definitions 2-1 DIVING 2.2 2.3 2.4 2.1.1 Pressure 2-1 2.1.2 Temperature 2-1 2.1.3 Density 2-1 2.1.4 Specific Gravity 2-1 2.1.5 Seawater 2-1 2-2 Pressure 2.2.1 Atmospheric Pressure 2-2 2.2.2 Hydrostatic Pressure 2-2 2.2.3 Absolute Pressure 2-2 2.2.4 Gauge Pressure 2-3 2.2.5 Partial Pressure 2-3 Buoyancy Gases Used 2-3 in 2-6 Diving 2.4.1 Air 2-6 2.4.2 Oxygen 2-6 2.4.3 Nitrogen 2-6 Helium 2.4.5 Carbon Dioxide 2.4.6 Carbon Monoxide 2.4.7 Argon, Neon, Hydrogen Gas Laws 2-6 2.4.4 2.5 2-7 2-7 2-8 2.5.4 Law Law Charles' Law Henry's Law 2-7 Boyle's 2.5.5 The General Gas Law 2-11 2.5.2 2.5.3 2.6 Gas Flow (Viscosity) 2.7 Moisture in 2-10 2-1 2-12 Breathing Gas 2.7.1 Condensation 2.7.2 Fogging of the in 2-12 Breathing Tubes or Mask Mask The Physics of Light Consequences 2-13 2-13 Light and Vision Under Water 2.8.1 2.9 2-6 Dalton's 2.5.1 2.8 2-6 Under Water and for Vision 2-13 the 2-13 2.8.1.1 Refraction 2-13 2.8.1.2 Scatter 2-14 2.8.1.3 Absorption 2-14 2.8.1.4 Insufficient Light 2-15 Acoustics 2-16 ( ( ( F PHYSICS OF DIVING 2.0 GENERAL Rankine (R) This section describes the laws of physics as they affect humans the water. in A thorough understanding of the physical principles set forth in the following paragraphs is Temperatures measured to = °F 2.1 to may centigrade in X X) + (1.8 Temperatures measured DEFINITIONS plus 273.15 °F plus 459.67 be converted Fahrenheit using the following formula: and effective diving performance. essential to safe X = = Kelvin (K) 32 may Fahrenheit in be converted centigrade using the following formula: This paragraph defines the basic principles necessary to an understanding of the underwater environment. The most important 2.1.1 (°F - C of these are listed below. 32) Pressure Pressure is force acting on a unit area. Expressed 2.1.3 Density Density mathematically: mass per unit volume. Expressed mathe- is matically: Pressure = Force P or = Area Density (D) = Mass Volume Pressure (psi) or usually expressed in pounds per square inch is Density kilograms per square centimeter (kg/cm 2 ). meter (gm/cm 3 ) Temperature form of energy that increases the temperawhich it is added and decreases the temperature of the matter from which it is removed, providing that the matter does not change state during the process. Quantities of heat are measured Heat is in the in grams per cubic centi- metric system. a ture of the substance or matter to in calories or British The temperature Temperature is thermal units (Btu). of a body is measure of a thermometer and expressed or Fahrenheit (°F). in it is its heat. measured by a degrees centigrade (°C) The quantity equal to the total kinetic energy of of heat in the all of its Temperature values must be converted body is Specific gravity is the ratio of the density of a sub- stance to the density of fresh water at 39.2 °F (4°C). Fresh water has a specific gravity of 1.0 at 39.2° cific gravities greater than 1.0, and substances lighter than fresh water have specific gravities human body 1.0, less than 1.0. The has a specific gravity of approximately although this varies slightly from one person to another. molecules. to absolute values for use with the Gas Laws. Both the Kelvin and Rankine scales are absolute temperature scales. Absois 2.1.4 Specific Gravity (4°C); substances heavier than fresh water have spe- produced by the average kinetic energy or speed of the body's molecules, and lute zero usually stated in pounds per cubic foot (lb/ft 3 ) English system and in the 2.1.2 is the hypothetical temperature characterized 2.1.5 Seawater Seawater is known that occur in nature. to contain at least 75 The elements four most abundant elements in by the complete absence of heat; it is equivalent to approximately -273 °C or -460 'F. Conversion to the Kelvin or Rankine scales is done by adding 273 units to the temperature value expressed in centigrade or 460 seawater are oxygen, hydrogen, chlorine, and sodium. units to the temperature value expressed in Fahrenheit, ture of seawater varies respectively. 30°C). October 1991 — NOAA Diving Manual Seawater is always slightly alkaline because it con- tains several alkaline earth minerals, principally sodi- um, calcium, magnesium, and potassium. The temperafrom 30.2T to 86.0°F (-IX to 2-1 Section 2 Table 2-1 Conversion Factors, Metric to English Units The specific gravity of seawater is affected both by and temperature, and these effects are interrelated. For example, water with a high enough salt content to sink toward the bottom will float at the surface if the water is sufficiently warm. Conversely, salinity water with a relatively low salt content will sink if it is Seawater also is an excellent electrical conductor, an interaction that causes corrosion problems when equipment is used in or near the ocean. To Convert From Metric Units To English Units Multiply By PRESSURE sufficiently chilled. gm/cm 2 inch of fresh water pounds/square inch 1 kg/cm 2 kg/cm 2 kg/cm 2 cm Hg cm Hg cm Hg cm Hg 1 cm 1 1 The viscosity of seawater varies inversely with tem- perature and as at 89.6 nearly twice as great at 33.8 °F (1°C) is °F (32 °C). The impact of be seen when the same sailboat higher speeds in warm water than in many In 1 able to achieve 1 1 cold. parts of the world the metric system of measurement still is 1 property can this is 1 of fresh water feet of fresh 0.394 water inches of mercury 14.22 (psi) (ffw) Hg) (in. 32.8 28.96 pound/square inch 0.193 foot of fresh water 0.447 foot of seawater (fsw) 0.434 inch of mercury 0.394 inch of fresh water 0.394 used rather than the English system widely used in the United States. Table 2-1 pres- VOLUME AND CAPACITY ents factors for converting metric to English units. 2.2 PRESSURE The pressure on forces: the a diver under water is the result of two weight of the water over him or her and the weight of the atmosphere over the water. Table 2-2 1 cc or ml cubic inch (cu 1 m3 cubic feet (cu 1 liter cubic inches 1 liter cubic foot 1 liter fluid 1 liter quarts (qt) ounces 0.061 in.) 35.31 ft) 61.02 0.035 (fl 33.81 oz) 1.057 provides factors for converting various barometric pressure units into other pressure units. The various types WEIGHT of pressure experienced by divers are discussed in the following sections. ounce (oz) ounces pounds (lb) gram 1kg 1kg 1 2.2.1 Atmospheric Pressure Atmospheric pressure acts on all bodies and strucatmosphere and is produced by the weight of atmospheric gases. Atmospheric pressure acts in all directions at any specific point. Since it is equal in all 0.035 35.27 2.205 LENGTH tures in the directions, its effects are usually neutralized. At sea atmospheric pressure is equal to 14.7 psi or 1.03 kg/cm 2 At higher elevations, this value decreases. Pressures above 14.7 psi (1.03 kg/cm 2 ) are often level, 1 cm inch 1 meter inches 1 meter feet 3.28 1 km mile 0.621 0.394 39.37 . AREA expressed in atmospheres. For example, one atmosphere equal to 14.7 psi, 10 atmospheres is equal to 147 psi, and 100 atmospheres is equal to 1470 psi. Figure 2-1 shows equivalent pressures in the most commonly used units for measuring pressure at both altitude and depth. is 1 cm 2 square inch 1 m2 square feet 1 km 2 square mile 0.155 10.76 0.386 Adapted from 2.2.2 produced by the weight of and acts on all bodies and struc- water (or any fluid) immersed in the is water (or pressure, hydrostatic pressure at a specific depth. sure to divers is is fluid). Like atmospheric equal hydrostatic pressure. descent in seawater and 0.432 psi per foot (1 kg/cm 2 per 10 meters) of descent in fresh water. This relationship is shown graphically in Figure 2-2. in all directions The most important form rate of 0.445 psi per foot (1 2-2 (1979) Hydrostatic Pressure Hydrostatic pressure tures NOAA It kg/cm 2 per of pres- increases at a 9.75 meters) of 2.2.3 Absolute Pressure Absolute pressure is the sum of the atmospheric pressure and the hydrostatic pressure exerted on a NOAA Diving Manual — October 1991 Physics of Diving Table 2-2 Conversion Table for Barometric Pressure Units N/m 2 atmosphere 1 Newton (N)/m 2 or 2 Hg lb/in ("Hg) (psi) 760 29.92 14.70 .0102 .0075 2953X10" 3 .1451X10" 3 Pa bars mb kg/cm 2 (cm H 2 0) 1 1.013X10 5 1.013 1013 1.033 1033 .01 1.02X10' 5 = 1 gm/cm 2 or atm in. mm Hg Pascal (Pa) = 9869X10" 5 1 bar = .9869 10 5 1 1000 1.02 1020 750.1 29.53 14.51 1 millibar (mb) = 9869X10" 3 100 .001 1 .00102 1.02 .7501 .02953 .01451 1 kg/cm 2 = .9681 9807X10 5 .9807 980.7 1 1000 735 28.94 14.22 1 gm/cm 2 = 968.1 98.07 9807X10' 3 .9807 .001 1 .735 .02894 .01422 = .001316 133.3 .001333 1.333 .00136 1.36 1 .03937 .01934 .0334 3386 .03386 33.86 .03453 34.53 25.4 1 .4910 .06804 6895 .06895 68.95 .0703 70.3 51.70 2.035 1 (1 1 cm H 2 0) mm Hg 1 in. Hg = 1 2 lb/in = (psi) 10 1 5 Adapted from submerged body. Absolute pressure is measured in pounds per square inch absolute (psia) or kilograms per square centimeter absolute (kg/cm 2 absolute). submerged body can be calculated by subtracting the weight of the submerged body from the ment, that Gauge Pressure Gauge pressure pressure and a being pressure specific measured. Pressures are usually measured with gauges that are balanced to read zero to the air. at sea level Gauge pressure is reads in when they are open therefore converted to absolute pressure by adding 14.7 psi or 1.03 if the dial is, the dial reads in if kg/cm 2 . that of the displaced liquid, the and the body Pressure density, that In a mixture of gases, the proportion of the total pressure contributed by a single gas in the mixture called the partial pressure. tributed by a single gas is buoyancy will be 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 will be neutral and the body will remain suspended in the liquid. If the weight of the submerged body is greater than is The is partial pressure con- in direct proportion to its percentage of the total volume of the mixture (see Section 2.5.1). buoyancy will be negative will sink. The buoyant 2.2.5 Partial If the total displace- the weight of the displaced liquid, greater than the weight of the submerged body, the the difference between absolute is (1979) Using Archimedes' Principle, the buoyancy or buoyant force of a weight of the displaced liquid. 2.2.4 NOAA is, force of a liquid its is dependent on its weight per unit volume. Fresh water has a density of 62.4 pounds per cubic foot (28.3 kg/ m3 ). Seawater is heavier, having a density of 64.0 pounds per cubic foot (29 kg/0.03 m 3 ). Therefore, a body in seawater will be buoyed up by a greater force than a body in fresh water, which accounts for the fact that it is easier to float in the ocean than in a fresh 0.03 water lake. 2.3 BUOYANCY Archimedes' Principle explains the nature of buoyancy. A body immersed in a liquid, either wholly is buoyed up by a force equal the weight of the liquid displaced by or partially, to the body. October 1991 Lung capacity can have a significant effect on the buoyancy of a submerged person. A diver with full lungs displaces a greater volume of water and therefore is more buoyant than a diver with deflated lungs. Other individual differences that may affect buoyancy include bone structure, bone weight, and relative amount of body fat. These differences help to explain why certain individuals float easily — NOAA Diving Manual and others do not. 2-3 m nn i Section 2 Figure 2-1 Equivalent Pressures, Altitudes, and Depths Atmospheres (atm) I 1 1 .0 1 1 1 1 1 .2 .1 Pounds Per Square Inch 1 1 .3 1 .4 1 1 .5 1 1 .6 1 1 .7 1 1 1 .8 1 1.0 .9 — — — — — — — — — — — — — — — — — — — — — — — — — — — — —i— I I I I I (psi) I I I I I I I I I I I I I I I I I I I I I I I I 2 4 Inches of Mercury (in i i i i 12 14 14.7 Hg) i i i i i 5 i i i i i 10 i i i i i i i i i 20 15 i i i i i 25 29.92 — — — — — — —(mm ——————————————————————— Millimeters of Mercury i i i 10 —————————————————————————————— i i 8 6 i i i Hg) i i i i i i 200 100 i i i i i i i i i 400 300 i i i i 500 i i i i i 700 600 760 + Millibars (mb) 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 P 1 I 200 100 400 300 600 500 700 800 900 0123456789 Newtons Per Square Meter x104 (n/m 2 x10 4 I 1 1 1 1 1 1 1 1 i i i i i 60 100 30 m i i i i i i i i 15 i i i 8 I 1 1 1 I I 1 I I P 1 1 i i i I 10 5 2 I of Feet i i 10 I 1 10.13 —n— — — — i i 3 I I 1 Thousands 1 6 I 1 i i i 20 10 Ll_l 1 i 30 40 1 1 i i i 50 20 ) ——————— Pressure Altitude 1 1013.2 I I I I I Thousands of Meters 0123456789 Atmospheres Absolute (ATA) I 1 Depth 1 in 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 10 Seawater I Meters 1 1 1 1 1 1 40 20 I I 200 150 I I I 1 I I I 1 80 60 100 50 1 250 300 I I Feet Adapted from National Aeronautics and Space Administration (1973) 2-4 NOAA Diving Manual — October 1991 ' Physics of Diving Figure 2-2 Effects of Hydrostatic Pressure > At the Surface Atmosphere Absolute, 14.7 psi The flotation device is fully expanded. in At 33 Feet {Vi 2 Atmospheres Absolute, 29.4 psi Surface Volume) Because of hydrosta tic pressure, the same volume of air in the flotation device is reduced to only Vi its surface lifting capacity At 1 32 Feet 5 Atmospheres Absolute, 73.5 psi A Surface Volume) Because of hydrostatic X pressure, the same volume flotation device surface lifting is of air in reduced to only the Vi its capacity. Adapted from October 1991 — NOAA Diving Manual NOAA (1979) 2-5 Section 2 Divers wearing wet suits usually must add diving some other diving the diver should adjust his or her gases. For example, when nitrogen is breathed at increased partial pressures, it has a distinct anesthetic effect called "nitrogen narcosis," a condition characterized by loss of judgment and neutral state so that disorientation (see Section 3.2.3.5). weights to their weight belts to provide the negative buoyancy that allows normal descent. At working depth, buoyancy to achieve a work can be accomplished without the additional physical effort of counteracting positive (upward) or negative (downward) buoyancy. 2.4.4 Helium Helium 2.4 GASES USED IN DIVING While under water, a diver is amounts. totally dependent on a Two methods of providing used. The diver may be supplied is It breathing gases can be diluent for or he or she may The second method gas supply. Many air is in and is is color- used extensively as a deep diving gas mixtures. Helium has some disadvantages but none as serious as those associated with nitrogen. For example, breathing helium- called scuba, an is combinations of breathing gases are used Compressed tasteless oxygen mixtures causes a temporary distortion of speech (producing a Donald Duck-like voice), which hinders Apparatus." diving. the atmosphere only in trace carry the breathing Underwater Breathing initialism for "Self-Contained and oxygen odorless, less, merged source, in substance, -452.02°F (-268. 9°C). Helium supply of breathing gas. with gas via an umbilical from the surface or a sub- found has the lowest boiling point of any known the most common, but use of other mixtures for special diving situations The following paragraphs describe most commonly found in diving operations. increasing. in the is the gases communication. Helium also has high thermal conductivity, which causes rapid loss of body heat in divers breathing a helium mixture. Helium is used in breathing mixtures at depth because of its lower density and lack of narcotic effect. However, helium should never be used in diving or standing of its treatment without a full under- physiological implications. 2.4.1 Air Air is a mixture of gases (and vapors) containing nitrogen (78.084%), oxygen (20.946%), argon (0.934%), carbon dioxide (0.033%), and other gases (0.003%). Compressed air is the most commonly used breathing gas for diving (see Section 2.4.2 is is 4). a colorless, odorless, and tasteless gas that only slightly soluble in water. It can be liquefied at -297. 4°F (-183°C) at atmospheric pressure when cooled T and will Oxygen is the only gas used by the human body, and it is essential to life. The other gases breathed from the solidify to -361.1 atmosphere or breathed by divers serve only as vehicles and diluents oxygen is (-218.4°C). in their gas mixtures for oxygen. However, dangerous when excessive amounts are breathed under pressure; this harmful effect oxygen poisoning (see Section is is and fermentation. It is colorless, odorless, and Although carbon dioxide generally is not considered poisonous, in excessive amounts it is harmful to divers and can even cause convulsions. Breathing C0 2 at increased partial pressure may cause unconsciousness (see Sections 3.1.3.2 and 20.4.1). For example, a person should not breathe air containing more than 0.10 percent C0 2 by volume (see Table 15-3); divers must therefore be concerned with the partial pressure tion, of the carbon dioxide in their systems, point is is and tasteless gas. It incapable of supporting life. -320. 8°F (-196°C). Nitrogen is oxygen in diving gas mixtures but has several disadvantages compared with 2-6 the removal of the excess the diver's breathing (see Sections 15.5.1.2 and C0 2 generated by essential to diving safety is 15.5.1.3). 3.3). a colorless, odorless, commonly used breathing gases. In the case of closed- and semi-closed-circuit breathing Carbon Monoxide Carbon monoxide (CO) is a poisonous gas. It is colorand tasteless and therefore difficult to detect. Carbon monoxide is produced by the incomplete combustion of hydrocarbons, which occurs in the exhaust systems of internal combustion engines. Carbon monoxide may also be produced by over-heated less, odorless, chemically inert and Its boiling produced by various called Nitrogen Nitrogen is a gas is natural processes such as animal metabolism, combus- 2.4.6 2.4.3 Carbon Dioxide Carbon dioxide (C0 2 ) tasteless. Oxygen Oxygen 2.4.5 as a diluent for oil-lubricated compressors. NOAA A level of Diving Manual 20 parts per — October 1991 Physics of Diving CO million of should not be exceeded breathing systems (see Table 15-3). in When pressurized scuba cyl- container were filled with oxygen alone, the partial pressure of the oxygen would be atmosphere. l If the inders are filled, care should be taken not to introduce same container were CO sures of each of the gases comprising air would con- from the exhaust system of the compressor into air the breathing gases. Proper precautions must be taken where cylinders are filled are adequately ventilated. The compressor's air intake must draw from an area where the atmosphere is free of to ensure that all areas with filled tribute to the total pressure, as shown in the following tabulation: Percent of Component x = contamination, such as automobile exhaust fumes. Total Pressure (Absolute) Partial Pressure Atmospheres Percent of Argon, Neon, Hydrogen 2.4.7 the partial pres- air, component Gas partial pressure Argon, neon, and hydrogen have been used experimentally as diluents for oxygen in breathing gas mix- although these gases are not used routinely tures, in diving operations. However, the results of recent research N2 78.08 0.7808 o2 20.95 .2095 co 2 .03 .0003 Other .94 .0094 100.00 1.0000 suggest that hydrogen-oxygen and helium-hydrogen- oxygen breathing mixtures may be used within the next decade in deep diving operations (Peter Edel, Total personal communication). 2.5 Example GAS LAWS The behavior If the of gases all is affected by three factors: the temperature of the gas, the pressure of the gas, the volume of the gas. The among relationships and these what are called the Gas Laws. Five of these, Dalton's Law, Boyle's Law, Charles' Law, Henry's Law, and the General Gas Law, three factors have been defined in are of special importance to the diver. were Dalton's Law Dalton's The that if it total is for example a scuba cylinder, with air to 2000 psi, the following steps table. Step 1 — Dalton's Law X Percent of component gas Law = total pressure (abso- partial pressure Percent of com ponents: states: total pressure gases same container, filled would be necessary to calculate the partial pressures (in ATA's) of the same components listed in the above lute) 2.5.1 1 exerted by a mixture of equal to the sum 78.08% N2 .7808 of the pressures N2 100 would be exerted by each of the gases alone were present and occupied the 20.95% o2 volume. .2095 2 100 In a gas mixture, the portion of the total pressure contributed by a single gas is called the partial pres- P Total = PPl + PP2 + PPn C0 2 00.94% .0094 Other Other 100 = total pressure of that Ppi = partial pressure of gas Pp 2 = partial pressure of gas Pp n = partial pressure of other gas P Tola An .0003 100 where at 00.03% co 2 sure of that gas. Stated mathematically: gas l component Step 2 l — Convert 2000 psi to atmospheres absolute (ATA) easily understood example atmospheric pressure, 14.7 October 1991 — NOAA component 2 components. (2000 psi) + 1 = ATA 14.7 psi is psi that of a container (l kg/cm 2 ). Diving Manual If the 136 + 1 = 137 ATA 2-7 Section 2 Step 3 — ATA Partial pressure of constituents at 137 Pp N = 0.7808 X 137 = 106.97 Pp = 0.2095 X 137 = 28.70 Pp co = 0.0003 X 137 = 0.04 ATA p P0ther = 00094 X 137 = 1.29 ATA Step 2 — Boyle's Law ATA C0 2 nents of the gas, particularly , 33 feet of water): =K P2 V 2 P2 ATA Step 3 = pressure at 33 feet in V2 = volume K = constant. — Equating increased significantly higher pressures, although they were fairly low at ATA at 33 feet in ft 3 the constant, K, at the surface and at 33 feet, we have P.V, Observe that the partial pressures of some compoat ( (at the following equation: = p2v2 Transposing to determine the volume at 33 atmospheric pressure. As these examples show, the implications of Dalton's Law are important and should be understood by all divers. feet: P.V, where Law 2.5.2 Boyle's Boyle's Law P 1 = states: At constant temperature, the volume of V, a gas varies inversely with absolute pressure, = v2 = 1 atmosphere (ATA) 2 ATA 24 1 while the density of a gas varies directly V2 = with absolute pressure (Figure 2-3). For any gas at a constant temperature, Boyle's Law ft 3 ATA X 24 2 ATA 12 ft 3 ft 3 . ( is: Note that the volume of air in the open bell has been compressed from 24 to 12 cubic feet in the first 33 PV = K feet of seawater. where = P Law Boyle's changes in the absolute pressure V = volume K= constant. Step 4 — Using the mine the method illustrated above volume at 66 feet: to deter- air P]V, is important to divers because volume of a gas to changes it relates in pressure (depth) and defines the relationship between pressure and volume in breathing gas supplies. The following example illustrates Boyle's Law. Example 1 An open (Boyle's where P, Law) v3 - diving bell with a volume of 24 cubic feet is V3 = be lowered into the sea from a surface support ship. No air is supplied to or lost from the bell, and the to is the same volume of the air space temperature 66-foot, Step 1 at all depths. Calculate the in Step the bell at the 33-foot, 5 — For 1 ATA ATA X 24 3 ATA 8 ft 3 ft 3 3 . method illusvolume would be: a 99-foot depth, using the trated previously, the air and 99-foot depths. — Boyle's Law = V, = K = P v4 = (at surface): P,V, 2-8 = =K pressure at surface in ( volume ATA 3 at surface in ft constant. PlV, where p4 V, NOAA < = 4 ATA = 6 ft 3 . Diving Manual — October 1991 > Physics of Diving Figure 2-3 Boyle's Law Adapted from October 1991 — NOAA Diving Manual NOAA (1979) 2-9 Section 2 As depth increased from the surface volume of open air in the 24 cubic feet to 6 cubic In this bell to 99 Because the volume of the closed feet, the was compressed from surface as at it is 99 feet, the bell is the decrease in the same at the pressure is a result of the change in temperature. Therefore, using feet. example of Boyle's Law, the temperature of Charles' Law: the gas was considered a constant value. However, temperature significantly affects the pressure and volume of a gas; is it therefore essential to have a method of (volume constant) including this effect in calculations of pressure and volume. is To because the temperature of the water deep oceans or in the knowing the effect of temperature a diver, essential, in lakes is from the temperature of the where often significantly different air at the surface. The gas = = T7 = law that describes the physical effects of temperature on pressure and volume At Law Charles' Law. 14.7 psia (atmospheric pressure) T, 80°F 33 °F + + 460°F 460° F = = 540 Rankine 493 Rankine. Transposing: Law 2.5.3 Charles' Charles' is Pj states: a constant pressure, the P2 volume of a = P.T 2 T, gas varies directly with absolute temperature. For any gas at a constant volume, the pressure of a gas varies directly with P, r 2 absolute temperature. _ — X 14.7 493 540 Stated mathematically: P2 (volume constant) = 13.42 psia. Note that the final pressure is below atmospheric pressure (14.7 psia) because of the drop in temperature. —=— V, T, Example 3 (pressure constant) To (Charles' Law) illustrate Charles' Law further, consider the fol- lowing example: where An = P2 = Tj = T2 = V, = V2 = P( To initial initial final one given for Boyle's A (Charles' is 45 ° F. What is is feet. At the 80 °F; at depth, the temper- the volume of the gas in the bell at 99 feet? Law, we know compressed to 6 cubic that the volume of the gas was level. 99-foot feet when the bell was lowered to the From Example volume volume. Law, an example similar Law lowered into the ocean to a depth of 99 ature pressure (absolute) final pressure (absolute) initial having a capacity of 24 cubic feet bell surface, the temperature final pressure (absolute) illustrate Charles' Example 2 is pressure (absolute) open diving to the can be used. 1 illustrating Boyle's Applying Charles' Law then illustrates the additional reduction in volume caused by temperature effects: Law) closed diving bell at atmospheric pressure and having a capacity of 24 cubic feet is lowered from the surface to a depth of 99 feet in the ocean. At the surface, the temperature perature when 33°F. 2-10 it is is is 80 °F; at 99 feet, 33 °F. Calculate the pressure on the bell at the 99-foot level where the tem- and the temperature is = = T2 = Vj volume T, 80 °F 45 °F at depth, 6 ft 3 + + NOAA 460 °F 460 °F = = 540 Rankine 505 Rankine. Diving Manual — October 1991 Physics of Diving Transposing: 2.5.5 The General Gas Law comGeneral Gas Law, Boyle's and Charles' laws can be conveniently Vv 2 — V,T 2 bined into what X 6 as the expressed mathematically as follows: T, V — known is P,V, P.V, 505 540 = V, 5.61 ft 3 T| P2 = V, Law Henry's = = = P, Law Henry's 2.5.4 where . states: The amount of any given gas that initial pressure (absolute) initial volume initial temperature (absolute) will dissolve in a liquid at a given temperature and a function of the partial pressure of the is gas that is contact with the liquid and the in coefficient solubility gas the of in the particular liquid. final pressure (absolute) V2 = final volume = final temperature (absolute). Tt This law simply states that, because a large percentage of the human body is more gas water, will dissolve into Example 4 (General Gas Law) the blood and body tissues as depth increases, until the point of saturation gas, saturation takes long as the pressure reached. Depending on the is from is 24 hours or longer. As 8 to maintained, and regardless of the quantity of gas that has dissolved into the diver's tissues, the A gas will remain way in 99 feet which Henry's Law works can be seen when a bottle of carbonated soda suddenly, causing the gases in solution to happens rate is form bubbles. This in a diver's tissues if the is developed fully is VG for = Henry's come out The General Gas Law states: p2v 2 P,V, of T, prescribed ascent in the discussion of decom- where = V, = T, = P2 = T2 = P, Law Determine the volume of similar to what pression (see Section 3.2.3.2). The formula being lowered to is exceeded. The significance of this phenomenon for divers is seawater from a surface temperature of 80 °F to a depth temperature of 45 °F. opened. Opening the container releases the pressure solution and to in the gas in the bell at depth. in solution. simple example of the Let us again consider an open diving bell having a capacity of 24 cubic feet that is: aP, VL 14.7 psia 24 3 ft 80°F + 460°F = 540 Rankine 460 °F = 505 Rankine. 58.8 psia 45 °F + Transposing: where VG = volume of gas dissolved at STP (standard temperature and pressure) V, = PiV.T 2 T,P, VL = a = volume of the Bunson liquid solubility coefficient at specified (14.7X24X505) V, temperatures (540)(58.8) P| = partial pressure in atmospheres of that gas above the liquid. October 1991 — NOAA Diving Manual V, = 5.61 ft 3 . 2-11 3 Section 2 Figure 2-4 Gas Laws ( same answer as that derived from a combination of Example 1 and Example 3, which were used This to is the demonstrate Boyle's and Charles' Laws. Figure 2-4 among illustrates the interrelationships Charles' Law, and the General Boyle's Law, Gas Law. Note: Effects of gravity 2.6 and water vapor are GAS FLOW (VISCOSITY) considered There are occasions when it is desirable to determine the rate at which gas flows through orifices, hoses, and other limiting enclosures. This can be approximated by employing Poiseuille's equation expressed mathematically as: for a given gas gases, which V = is for in not the illustration because they are so sma I ATM 80°F 40°F 60°F 3 2 l APr 4 7r 8Lt7 where 20-0 V = AP = gas flow, in cm 3 sec 2 1 • ATM 4 • 6 cm-2 r = radius of tube, in cm L = length of tube, in cm t] = viscosity, in poise. ( r This equation can be used only in relatively simple 3 9.6 10.0 9.3 ATM 7 systems that involve laminar flow and do not include a 9 8 of valves or restrictions. For practical applica- tions, the diver should note that, as resistance increases, flow decreases in direct proportion. Therefore, length of a line if the increased, the pressure must be is increased to maintain the same flow. Nomograms for flow resistance through diving hoses can be found in Volume 5 pressure gradient between 2 ends of tube, in dynes number 18.5 19. 2 of the US Navy Diving Manual 6.6 6.4 (1987). 1 r 6.2 Instructions: 2.7 MOISTURE IN (1) BREATHING GAS Breathing gas must have sufficient moisture to be comfortable for the diver to breathe. Too much moisture in and pro- a system can increase breathing resistance duce congestion; too little (2) can cause an uncomfortable sensation of dehydration in the diver's mouth, throat, nasal passages, and sinus cavities (U.S. Navy 1988). (3) Air or other breathing gases supplied from surface compressors or tanks can be assumed to be dry. This dryness can be reduced by removing the mouthpiece and rinsing the mouth with water or by having the diver introduce a small amount of water into his or her throat inside a full face mask. The use of gum or candy 2-12 (4) A uniform bore sealed-end tube with 20 divisions is inverted in a container of water at 80 degrees F and one atmosphere pressure. The conditions of temperature and pressure are then changed as illustrated to explain the three gas laws. Steps 1,2,3; 4,5,6; 7,8,9 (horizontally) illustrate Charles' Law, i.e., the reduction of volume with reduction in temperature at a constant pressure. Steps 1,4,7; 2,5,8; 3,6,9 (vertically) illustrate Boyle's Law, i.e., at a constant temperature the volume is inversely related to the pressure. Steps 1,5,9; 3,5,7 (diagonally) illustrate the General Gas Law i.e., a combination of Charles's and Boyle's Laws. Adapted from NOAA Diving Manual NO A A (1979) — October 1991 ( Physics of Diving Figure 2-5 Objects Under Water Appear Closer can be dangerous, because to reduce dryness while diving these items may become The mouthpiece should may lodged not be be polluted (see Section Condensation 2.7.1 in 1 in the diver's throat. removed in water that 1). Breathing Tubes or Expired gas contains moisture that Mask may condense the breathing tubes or mask. This water is easily in blown out through the exhaust valve and generally presents no problem. However, may freeze; if in very cold water the condensate this freezing becomes serious enough to block the regulator mechanism, the dive should be aborted. 2.7.2 Fogging of the Mask Condensation of expired moisture or evaporation from the skin may cause fogging of the face mask glass. Moistening the glass with saliva, liquid soap, or commercially available anti-fog compounds will reduce or prevent this difficulty. However, it should be noted that some of the ingredients in chemical defogging agents can cause keratitis (inflammation of the cornea) if improperly used. Wright (1982) has described two such cases; symptoms included severe burning, photophobia, tearing, and loss of vision, which Wright attributed to the use of excessive quantities of the Rays passing from water into air are retracted normal, since the refractive index of water The is away from the 1.33 times that of system of the eye (omitted for simplicity) forms a image on the retina, corresponding to that of an object at about three-quarters of its physical distance from the air-water interface. The angle subtended by the image is thus 4/3 air. real lens inverted larger than Source: in air. NOAA (1979) defogging solution and inadequate rinsing of the mask. 2.8 LIGHT AND VISION UNDER WATER diving, the refraction occurs at the interface mask and the water. The image of an underwater object (see Figure 2-5) is magnified, appears larger than the real image, and the air in the diver's 2.8.1 The Physics of Light Under Water and the Consequences for Vision To function effectively under water, divers understand the changes that occur ception under water. Many simply by the fact that must in their visual per- of these changes are caused light, the stimulus for vision, travels through water rather than air; consequently it between refracted seems to be positioned at a point three-fourths of the actual distance between the object and the diver's faceplate. This displacement of the optical image might be expected to cause objects to appear closer to the diver than they actually are and, under some conditions, and scattered differently than Refraction, absorption, and scatter all follow objects do indeed appear to be located at a point three- physical laws and their effects on light can be predicted; fourths of their actual distance from the diver. This is refracted, absorbed, in air. changed physical stimulus can in turn have pronounced effects on our perception of the underwater world. Both the physical changes and their effects on vision are described in detail in Kinney (1985) and are only summarized here. this distortion interferes with hand-eye coordination and accounts for the difficulty often experienced by novice At phenomenon may reverse objects appearing farther away than divers attempting to grasp objects under water. greater distances, however, this itself, with distant they actually are. The clarity of the water has a pro- found influence on judgments of depth: the more tur2.8.1.1 Refraction bid the water, the shorter the distance at which the In refraction, the light rays are bent as they pass from one medium October 1991 to another of different density. In — NOAA Diving Manual reversal from underestimation to overestimation occurs (Ferris 1972). For example, in highly turbid water, the 2-13 Section 2 distance of objects at 3 or 4 feet (0.9 or 1.2 m) may be overestimated; in moderately turbid water, the change might occur 20 to 25 feet at away clear water, objects as far 22.9 (6.1 to 7.6 m); and in very as 50 to 75 feet (15.2 to m) might be wmferestimated. It is 20/200) on the surface (Luria and Kinney 1969). While myopes (near-sighted much as loss in individuals with individuals) do not suffer quite acuity if their face masks are lost as 20/20 myopes and normals, were found vision do, the average acuities of the two groups, important for the diver to realize that judgments of depth and distance are probably inaccurate. As a more be 20/2372 and 20/4396, respectively, in to one study of underwater acuity without a mask (Cramer 1975). rough rule of thumb, the closer the object, the likely it will appear too close, and the more turbid the water, the greater the tendency to see it as too far away. Scatter occurs Training to overcome inaccurate distance judgments can be effective, but it is important that it be carried out in water similar to that of the proposed dive or in a variety of different In addition, training types of water (Ferris 1973). must be repeated periodically to in the optical image result in a number other distortions in visual perception. Mistakes in of esti- mates of size and shape occur. In general, objects under water appear to be larger by about 33 percent than they actually are. This often pointment to sport divers, who is a cause of disap- find, after bringing catches to the surface, that they are smaller than they appeared under water. Since refraction effects are greater for objects off to the side of the field of view, distortion perceived shape of objects is in air, light an object appears to cross the distortions; if view, its speed will apparent distance These errors it be increased because of the greater travels (Ross in visual and Rejman 1972). perception and misinterpreta- refraction can be overcome, to and speed caused by some extent, with experi- ence and training. In general, experienced divers fewer errors diffused and scattered by the water molecules is all divers are influ- to respond more accurately have met organisms. Normally, scatter interferes with vision and underwater photography because it reduces the contrast between the object and its background. This these undesirable effects, air itself if the face in water, mask is is essential for vision. lost, the diver's eyes which has about the same refrac- Consequently, no normal focusand the diver's vision is impaired immensely. The major deterioration is in visual acuity; other visual functions such as the perception of size and distance are not degraded as long as the object can be seen (Luria and Kinney 1974). The loss of acuity, however, is dramatic, and acuity may fall to a level that would be classified as legally blind (generally tive index as the eyes. ing of light occurs 2-14 major reason why vision loss of contrast is the much more is so restricted in water than in air (Duntley 1963, Jerlov 1976); it also accounts for the fact that even large objects can be invisible at short viewing distances. In addition, acuity or perception of small much generally is poorer in water than in air, despite the fact that the optical image of an object The magnified by refraction (Baddeley 1968). is deterioration increases greatly with the distance the light travels through the water, largely because the image-forming light is further interfered with as it passes through the nearly transparent bodies of the biomass, which is composed of organisms ranging from bacteria to jellyfish (Duntley 1976). 2.8.1.3 Absorption Light much tral Although the refraction that occurs between the water and the air in the diver's face mask produces immersed kinds of particulate matter held in make with some, but not complete, success. For example, all suspension in the water, and by transparent biological enced to some extent by the optical image, and attempts them greater concern under water because judging the underwater world than do in novice divers. However, almost are much of under water field of tions of size, distance, shape, to train is it frequent. Similarly, the perception of speed can be influenced by these Although scattering also occurs particles in the water. details in the when individual photons of light are when they encounter suspended deflected or diverted themselves, by be effective Changes Scatter 2.8.1.2 to of is it absorbed as is lost in components of it passes through the water, and the process. In addition, the spec- light, the wavelengths that give rise our perception of color, are differentially absorbed. Transmission of light through air does not appreciably change its spectral composition, but transmitting light through water, even through the clearest water, does, and this can change the resulting color appearance beyond recognition. In clearest water, long wavelength or red light is lost first, being absorbed at relatively shallow depths. Orange is filtered out next, followed by yellow, green, and then blue. Other waters, particusilt, decomposing plant and animal material, and plankton and a variety of possible pollutants, which add their specific absorp- larly coastal waters, contain tions to that of the water. Plankton, for NOAA Diving Manual example, absorb —October 1991 Physics of Diving violets and blues, the colors transmitted best by clear of material suspended in some harbor ous under water because fluorescent materials convert frequently sufficient to alter the transmission are rarely present under water, which increases the water. The amount water is curve completely; not only ted, but the long is wavelengths very may little light transmit- in clear water (Jerlov 1976, Kinney et al. 1967, Mertens 1970). Color vision under water, whether for the of colors, color appearances, or legibility, more complicated than is visibility thus much Accurate underwater know the colors involved, in air. color vision requires that divers understand the sensitivity of the eye to different col- know ors, color contrast. be transmitted bet- than the short, a complete reversal of the situation ter short wavelength light into long wavelength colors that the depth and underwater viewing distance, The use of color coding under water by these changes in they are equally bright, but equally visible the characteristics of the specific waters involved. Infor- turbid harbor waters, red mation is available from several investigations about which colors can be seen best and which will be invisi- green under water (Kinney et al. is a summary in the appearance of colors under water. For example, red objects frequently appear black under water. This is readily understandable when one considers that red objects appear red on the surface because of reflected red light. in Since clear water absorbs the red light preferentially, at depth no red light reaches best for peripheral or off-center viewing. Attenuation and scatter dramatically reduce the amount of natural light available under water, restricting natural daylight vision to a few hundred feet under the and to to 2 feet (0.30 to 0.61 m) or under the worst or highly turbid conditions. If there is not enough light (without an auxiliary dive best of conditions l less light) for daylight vision, we take many visual capabilities that for granted in air will be greatly different; this includes good acuity, color vision, and good central or the object to be reflected, and therefore the object direct vision. In a low-light situation, acuity appears unlighted or black. In the same way, a blue poor and the diver object in yellowish-green water near the coast could appear black. Substances that have more than one peak in their reflectance curve may appear quite different on land and in the sea. Blood is a good example; maximum in the green is a much larger one in the red. At depth, the water may absorb the long wavelength light and blood may appear green. The ghostly at the surface a reflectance not noticeable because there appearance of divers clear water is in 20 to 30 feet (6.1 to 9.1 and less color is m) of loss of red light. perceived as the depth and viewing distance under water are increased, and all objects tend to look as though they are the color (the color that ular is same best transmitted by that partic- body of water). Objects must then be distinguished by their relative brightness or darkness. In Table many 2-3, of the most visible colors are light, bright colors that give good brightness contrast with the dark water If the background were different (for examwere white sand), darker colors would have increased visibility. Fluorescent colors are conspicuit October 1991 — NOAA Diving Manual is very be unable to read; he or she will have no clear vision, because objects will appear all center to see rather than looking directly at an object. Moreover, in order to see at all, the diver must dark- adapt. In air, an individual can gradually adapt to night- time light levels during twilight and probably not notice may go directly from bright sunlight on the boat into a dark underwater world and be completely blind. To function effectively, the change in vision; however, a diver the diver's eyes light. must adjust 30 minutes as long as Some if to the dim illumination he or she has been for in bright adaptation will take place while the diver descends, but the rate of descent cannot be slow enough to make this a practical solution, are required. This in is and other techniques especially important during dives which the bottom time is short and visual observa- tion important. The most background. ple, if will white, gray, or black; the diver will have to look off- is another example of the In general, less highly best for direct viewing and is 2.8.1.4 Insufficient Light of the results of these experi- ments and shows the colors that were most visible when viewed by a diver against a water background. Changes occur too is if 1967, 1969; Kinney and Miller 1974; Luria and Kinney 1974; Kinney 1985). Table 2-3 complicated colors can be employed without risk of confusion. Green and orange are good choices, since they are not confused in any type of water. Another practical question concerns the most legible color for viewing instruments under water; the answer depends on many conditions, which are specified in Human Engineering Guidelines for Underwater Applications (Vaughan and Kinney 1980, 1981). In clear ocean water, most colors are and are familiar with the general nature of water and ble is color appearance, and only a few to remain dive. in effective way to become dark-adapted is the dark for 15 to 30 minutes before the If this is impossible, red goggles are recommended. 2-15 Section 2 Table 2-3 Colors That Give Best Visibility Against a Water Background Water Condition Murky, turbid water of low (rivers, visibility Natural Illumination Incandescent Illumination Fluorescent yellow, orange, Yellow, orange, red, white (no advantage and red harbors, in Mercury Light Fluorescent fluorescent yellow-orange paint) etc.) yellow-green and Regular yellow, orange, and Regular yellow, white white Moderately turbid water Any fluorescence (sounds, bays, coastal yellows, oranges, or reds the in Any fluorescence Fluorescent the in yellows, oranges, or reds yellow-green or yellow-orange water) Clear water (Southern water, deep water Regular paint of yellow, Regular paint of yellow, orange, white orange, white Fluorescent paint Fluorescent paint Regular yellow, white Fluorescent paint offshore, etc.) Note: With any type of illumination, fluorescent paints are superior. a. With long viewing distances, fluorescent green and yellow-green are excellent. b. With short viewing distances, fluorescent orange is also excellent Adapted from The night vision system of the eye is relatively insensi- tive to red light; consequently, if a red filter is worn colder a layer of water, the greater its that a sound heard 164 feet (50 meters) light day vision system to continue to function. The red filter should be worn for 10 to 15 minutes and must be removed before the dive. Because high visual sensitivity is reached sooner when this procedure is used, visual underwater tasks can be performed at the beginning of the dive instead of 20 to 30 minutes later. If it is necessary to return to the surface even momentarily, the red filter should be put on again, because exposure for the to bright light quickly destroys the dark-adapted state of the eye. is within one layer source if may the diver is in is a periodic motion of pressure change transmitted (air), Since liquid a denser required is to a liquid (water), or a solid (rock). medium than disturb its gas, equilibrium. more energy Once this disturbance takes place, sound travels farther and faster in the denser medium. Several aspects of underwater sound are of interest to the working diver. may be two or more water at different tem- During diving operations, there distinct contiguous layers of peratures; these layers are 2-16 source its In shallow water or in enclosed spaces, reflections and reverberations from the air/water and object/water interfaces will produce anomalies in the sound field, i.e., is echoes, dead spots, and sound nodes. swimming shallow water, in among When a diver coral heads, or in enclosed spaces, periodic losses in acoustic communication signals and disruption of signals from acoustic The problem as the frequency of the signal increases. through a gas is its another layer. navigation beacons are to be expected. ACOUSTICS Sound from be inaudible a few meters from becomes more pronounced 2.9 density; as the transmitted between them. This means sound energy adapt and at the same time there be enough (1979) difference in density between layers increases, less over the face plate before diving, the eyes will partially will NOAA known as thermoclines. The The use of open-circuit scuba affects sound recep- 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). If several divers are working in the same area, the noise and bubbles tion 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. will affect A suit is an effective barrier to sound above 1000 Hz, and it becomes more of neoprene wet at frequencies NOAA Diving Manual —October 1991 Physics of Diving a barrier as frequency increases. This problem can be overcome by exposing a small area of the head cither by cutting holes 0.79 to 1.18 in. (2 to 3 cm) at the temples or above the ears of the hood. The human ear is an extremely sensitive pressure detector in air, but it is less efficient in water. A sound must therefore be more intense in water ( + 20 dB to 60 dB, SPL) to be heard. Hearing under water is very to localize and navigate conditions. In general, similar to trying to hear with a conductive hearing loss correspondingly high intensity pressure waves. under surface conditions: a smaller may shift in pressure is to sound beacons under all successful sound localization and navigation depend on clearly audible pulsed signals of short duration that have frequency components below 1500 Hz and above 35,000 Hz and are pulsed with a fast rise/decay time. Sound is transmitted through water as a series of pressure waves. High intensity sound is transmitted by A diver be affected by a high intensity pressure wave that transmitted from the surrounding water to the open required to hear sounds at the extreme high and low is frequencies, because the ear The preswave may create increased pressure within these open spaces, which could result in injury. The sources of high intensity sound or pressure waves include underwater explosions and, in some cases, sonar. Low intensity sonars such as depth finders and fish finders do not produce pressure waves of an intensity dangerous to a diver. However, some military antisubmarine sonar-equipped ships do pulse high intensity pressure waves dangerous to a diver. It is prudent frequencies. is not as sensitive at these The SPL necessary nication and navigation for effective a function of the is commu- maximum dB SPL distance between the diver and the source (-3 for every doubling of the distance and the measurement point), the between the source frequency of the signal, the ambient noise level and frequency spectrum, type of head covering, experience with diver-communication equipment, and the diver's stress level. The use of sound as a navigation aid or as a means of locating an object in the environment depends primarily on the difference in the time of arrival of the sound two ears as a function of the azimuth of the source. Recent experiments have shown that auditory at the localization cues are sufficient to allow relatively pre- sound localization under water. Moreover, it has been demonstrated that under controlled conditions cise divers are able to localize and navigate to sound bea- cons (Hollien and Hicks 1983). This research and practical experience have shown that not every diver October 1991 — NOAA Diving Manual is able spaces within the body (ears, sinuses, lungs). sure to suspend diving operations transponder is being operated a diver-held pinger system, it if a high-powered sonar in the area. is When using advisable for the diver wear the standard 1/4-inch (0.64-cm) neoprene for ear protection. Experiments have shown that such a hood offers adequate protection when the ultrasonic pulses are of 4-ms duration, are repeated once per second for acoustic source levels up to 100 watts, to hood and are at head-to-source distances as short as 4 inches (10 cm). 2-17 ( ( ( Page SECTION 3 DIVING 3.0 General 3-1 3.1 Circulation and Respiration 3-1 PHYSIOLOGY 3.1.1 Circulatory System 3-1 3.1.2 Mechanism 3-2 3.1.3 3.1.2.1 Pulmonary Ventilation 3-2 3.1.2.2 Blood Transport of Oxygen and Carbon Dioxide 3-2 3.1.2.3 Gas Exchange 3-4 3.1.2.4 Tissue 3.1.2.5 Summary Need in the for Tissues Oxygen of Respiration Process Respiratory Problems 3.1.3.4 Smoking 3-7 3.1.3.5 Excessive Resistance to Breathing 3.1.3.6 Excessive 3.1.3.7 Hyperventilation and Breath-holding Dead Space 3.2.1.2 3.2.1.3 3 2.1.4 The The The The 3-5 3-6 3-8 3-8 3-8 3-10 Direct Effects of Pressure During Descent 3.2.1.1 3.2.3 3-5 3.1.3.3 Effects of Pressure 3.2.2 3-4 3-5 3.1.3.2 3.2.1 3-4 Hypoxia Carbon Dioxide Excess (Hypercapnia) Carbon Monoxide Poisoning 3.1.3.1 3.2 of Respiration 3-10 Ears 3-10 Sinuses 3-12 Lungs 3-13 Teeth 3-14 Direct Effects of Pressure During Ascent 3-14 3.2.2.1 Pneumothorax 3-14 3.2.2.2 3-14 3.2.2.3 Emphysema Subcutaneous Emphysema 3.2.2.4 Gas Embolism 3-15 3.2.2.5 Overexpansion of the Stomach and Intestine 3-16 3.2.2.6 Bubble Formation and Contact Lenses Mediastinal Indirect Effects of Pressure 3-15 3-16 3-16 3.2.3.2 Gas Absorption and Elimination Decompression Sickness 3.2.3.3 Counterdiffusion 3-19 3.2.3.4 Aseptic Bone Necrosis (Dysbaric Osteonecrosis) 3-20 3.2.3.5 Inert 3.2.3.6 High Pressure Nervous Syndrome (HPNS) Inert 3.2.3.1 Gas Narcosis 3.3 Oxygen Poisoning 3.4 Effects of Cold (Hypothermia) 3-16 3-17 3-20 3-22 3-22 3-24 3-25 3.4.3 Thermal Protection Symptoms of Hypothermia Survival in Cold Water 3.4.4 Rewarming 3-27 3.4.1 3.4.2 3-25 3-26 3.5 Effects of Heat (Hyperthermia) 3-27 3.6 Drugs and Diving 3-28 3.6.1 3.6.2 Prescription Drugs 3-28 Drugs 3-28 Illicit ( ( < DIVING PHYSIOLOGY 3.0 GENERAL Figure 3-1 This section provides divers with basic information about how the body reacts to physiological stresses that are imposed by diving and how to compensate The Process of Respiration for these stresses and other physical limitations. Divers Conchae should become familiar with the terminology used in this Sphenoidal Sinus chapter to understand and be able to describe any symptoms or physical problems they Commonly used diving medical terms are diving-related experience. Septum Adenoid (Naso-Pharyngeal Tonsil) defined in the glossary of this manual (Appendix E). 3.1 The CIRCULATION AND RESPIRATION each activity of cell Hairs Soft Palate Hard Palate Tonsil Tongue of the body involves several delicate reactions that can take place only under well- defined chemical and physiological conditions. chief function of the circulatory system is to conditions around the cells at the level that for their functioning. The Esophagus (Food Tube) The Larynx (Voice Box) maintain is Trachea (Windpipe) optimal regulation of cardiac output and the distribution of the blood are central Alveoli is Lung Bronchus to the Pulmonary Vein the process by which gases, oxygen, Pulmonary and carbon dioxide are interchanged among the tissues and the atmosphere. During respiration, air enters the lungs via the nose or Right Bronchial physiology of circulation. Respiration Pharynx mouth and then Artery Cut Edge of Pleura traverses the (Hilus) Bronchiole pharynx, larynx, trachea, and bronchi. Air being exhaled follows this path in reverse. The bronchi enter the lungs and divide and re-divide into a branching net- Pulmonary Venule Cut Edge of Diaphragm work, ending in the terminal air sacs (alveoli), which are approximately one ten-thousandth of an inch (0.003 millimeter) in diameter. The Pulmonary Arteriole Stomach alveoli are sur- rounded by a thin membrane, and the interchange of membrane, where the blood gases takes place across this Source: NOAA (1979) pulmonary capillaries takes up oxygen and gives off carbon dioxide. This process is shown schein the tiny Before discussing diving physiology, a basic understanding of circulation, respiration, and certain prob- lems associated with the air-containing compartments of the body is necessary. These topics are discussed in the following paragraphs. 3.1.1 Circulatory The heart sides, is System divided vertically into the right and left each consisting of two communicating chambers, October 1991 — NOAA is pumped by the pulmonary artery, through the pulmonary capillaries, and back to the left side of the heart through the pulmonary veins. The left ventricle pumps the blood into the aorta, which distributes it to the body. This distribution is accomplished by a continual branching of arteries, which become smaller until they become capillaries. The capillaries have a thin wall through which gases and other substances are interchanged between the blood and the tissues. Blood from the capillaries flows into the venules, the veins, the auricles and ventricles. Blood matically in Figure 3-1. Diving Manual right ventricle into the 3-1 Section 3 is returned to the heart. In this way, carbon dioxide produced in the tissues is removed, transported to the lungs, and discharged. This process is shown schematically in Figure 3-2. During exercise, there is an increase in the frequency and force of the heart beat as well as a constriction of the vessels of the skin, alimentary canal, and quiescent muscle. Peripheral resistance is increased and arterial pressure rises. Blood is expelled from the spleen, liver, skin, and other organs, which increases circulatory blood volume. The net result of this process is an increase in the rate of blood flow to the body organs having a high demand for oxygen the brain, the heart, and any and, finally, — adequately to a demand for increased ventilation during exercise. Because diving often requires strenuous exercise, cardiovascular or respiratory disorders participating in this activity. 3.1.2.1 Pulmonary Ventilation Air drawn into the lungs passages until air it is distributed through smaller reaches the honeycomb-like alveoli or through which the exchange of respiratory The rates at which air sacs gases takes place (see Figure 3-1). oxygen active muscles. may from actively seriously limit or prevent an individual is supplied and carbon dioxide removed from the lungs depend on several factors: (1) the composi- and volume of the tion 3.1.2 Mechanism The of Respiration is and relaxation of muscles. This thoracic cavity contains the lungs, which are connected with the outside environment through the bronchi, the trachea, and the upper respiratory passages and the heart and great vessels. When the volume of the thoracic cavity changes, a decrease or altered by the rhythmic contraction increase in pressure occurs within the internal cham- bers and passages of the lungs. This change causes air passageways is until the pressure through the respiratory everywhere in the lungs equalized with the external pressure. Respiratory ventilation consists of rhythmic changes of this sort. Respiration is affected by the muscular action of the diaphragm and chest wall and is under the control of the nervous system, which itself in is through the res- gases in the blood; and (3) the duration for which a chest wall encloses a cavity, the volume of which to flow into or out of the lungs air supplied piratory passages; (2) the partial pressures of respiratory responding to changes blood oxygen and carbon dioxide levels. The normal respiratory rate at rest varies from about 12 to 16 given volume of blood is exposed to alveolar air. In a good physical condition, other facinfluencing respiratory exchange are not likely to normal person tors in be significant. liter of oxygen is used by the During exercise, an exchange of about 3.5 liters or more of oxygen per minute may take place. This flexibility is accomplished by increased At rest, about 0.3 tissues per minute. frequency of breathing, increased heart action propelling blood through the pulmonary capillaries, and increased differences in the partial pressures of oxy- gen and carbon dioxide during exercise. Figure 3-3 depicts oxygen consumption as a function of work rate. Normally, despite wide differences in the rates of gaseous exchange in the resting and heavy exercise condiblood leaving the lungs is almost completely saturated with oxygen and in equilibrium with the tions, the alveolar carbon dioxide pressure. breaths a minute. During and after heavy exertion, this rate increases severalfold. In the chest wall's normal resting position, that is, at the end of natural expiration, the lungs contain about Even when one voluntarily expels all the air possible, there still remain about 1.5 liters of residual air. The volume of air that is inspired and expired during rest is referred to as tidal air and averages about 0.5 liter per cycle. The additional volume 2.5 liters of air. 3.1.2.2 Blood Transport of Oxygen and Carbon Dioxide Blood can take up a much from the resting expiratory position of 2.5 liters that can be taken in during a maximal inspiration varies greater quantity of oxygen and carbon dioxide than can be carried in simple solution. Hemoglobin, which is the principal constituent in red blood cells and gives the red color to blood, has a chemical property of combining with oxygen and with carbon dioxide and carbon monoxide. The normal hemo- greatly from individual to individual, ranging from globin content of the blood increases the blood's oxygen- about 2 to 6 liters. The total breathable volume of air, carrying capacity by about 50 times. The reaction governed primarily called the vital capacity, depends on the size, develop- between oxygen and hemoglobin ment, age, and physical condition of the individual. by the partial pressure of oxygen. At sea level, where there is normally an inspired oxygen partial pressure Vital capacity is defined as the maximal volume that can be expired after maximal inspiration. in vital 3-2 A reduction capacity limits the ability of a person to respond is of 150 millimeters of mercury, the alveolar hemoglobin becomes about 98 percent saturated NOAA Diving Manual in terms of its —October 1991 Diving Physiology Figure 3-2 The Circulatory System Right auricle Lung capillaries Tricuspid -f^lt valve Bicuspid valve Veins Arteries Body capillaries Source: capacity to form oxy-hemoglobin. In the tissues, where the partial pressure of oxygen normally about 20 millimeters of mercury, between one-third and one-half of this oxygen is given up by hemoglobin and made available to the tissues. It is is apparent that the blood of persons lacking a sufficiency of hemoglobin, i.e., anemic persons, to carry oxygen. generally less fit As will be deficient a consequence, in its anemic people are for diving than people anemic. October 1991 capacity who are not The blood contains in Shilling. a small Werts. and Schandelmeier (1976) amount of carbon dioxide simple solution, but a greater amount is found in chemical combinations such as carbonic acid, bicarbonate, or bound to hemoglobin. All the forms of carbon dioxide tend toward chemical equilibrium with each other. The taking up of oxygen by the hemoglobin in the lung capillaries favors the unloading of carbon dioxide at the same time dioxide into the blood in that the absorption of carbon the tissues favors the release of oxygen. — NOAA Diving Manual 3-3 Section 3 Figure 3-3 Oxygen Consumption and Respiratory Minute Volume as a Function of Work Rate S Sitting S. Rest Light Moderate Work Work Heavy Work Severe Work Quietly!* Swim, 0.71 I (Slow)H^ 0.5 Knot (20) .E E Swim, 0.85 Knot (Average "5 ^ = c 1.4 I (40) 8 SpeeoV^^ Swim, 1 Knot »s E * 2 ° il Swim, 2.1 1.2 Knots^^ \^ (60) o 0) \^ 2.8 cc (80) "\ \ I I I I i I I Oxygen Consumption, standard i liters/min Derived from Gas Exchange 3.1.2.3 in the Tissues 3.1.2.4 NOAA (1979) Tissue Need for Oxygen of oxygen and carbon dioxide between All living tissues need oxygen, but tissues that are the blood and body cells occurs in opposite directions. especially active during exertion, such as skeletal muscle, Oxygen, which need greater amounts of oxygen. The brain, however, The exchange is continuously used in the tissues, exists there at a lower partial pressure than in the made up is of tissue that has an extraordinarily high and produced inside the tissue nearly steady requirement for oxygen. Although the which increases its concentration relative to that of the blood reaching the tissues. Therefore, blood supplied by the arteries gives up oxygen and receives nervous system represents only about 2 percent of the Carbon dioxide blood. is cells, transit through the tissue exchange of these respiratory amount of gas movement depend on carbon dioxide during capillaries. The its rate of gases and the total their respective partial pressure differences, since the exposure time of blood in the tissue capillaries is ade- body weight, it requires about 20 percent of the total circulation and 20 percent of the total oxygen used by the body per minute at work or at rest. If circulation completely cut off, consciousness may be one-quarter of a minute and irreparable higher centers of the brain 5 minutes (see Section is lost in about damage to the may occur within 3 to 3.1.3.1). quate for nearly complete equilibration to be achieved. When more active, the need for oxygen is The increased oxygen is supplied not from an tissues are greater. increase in the oxygen content of the arterial blood but by the larger volume of blood that flows through the tissues and by a more complete release of oxygen from a given volume of the blood. There can be as much ninefold increase in the rate at which oxygen plied to active tissues. 3-4 is as a 3.1.2.5 Summary The process of Respiration Process of respiration includes six important phases: (1) (2) sup- Breathing or ventilation of the lungs; Exchange of gases between blood and air in the lungs; (3) The transport of gases carried by the blood; NOAA Diving Manual — October 1991 Diving Physiology (4) (5) Exchange of gases between blood and body tissues; Exchange of gases between the tissue fluids and and Use and production of gases by the cells. Each phase of this process is important to the life of the and the process must be maintained constantly by the respiratory and circulatory systems. cells, so that spontaneous breathing will resume. cult to know when It is diffi- the heart action has stopped com- pletely, so efforts at resuscitation until 3.1.3 will If breathing has stopped but heart action continues, cardiopulmonary resuscitation may enable oxygen to reach the brain and revive the breathing control center cells; (6) promptly before breathing stops, the diver usually regain consciousness shortly and recover completely. must be continued medical attendants pronounce a victim dead. Respiratory Problems Although most physiological problems associated WARNING with diving are related to the breathing of gases at the high pressures encountered under water, respiratory problems may occur at the surface as well. These problems are generally related to the inadequate transport Is Onset of oxygen to the cells and to the inadequate removal of Some carbon dioxide. of the common respiratory prob- 3.1.3.2 An lems are hypoxia, hypercapnia, and carbon monoxide Each of these poisoning. is discussed in the following if Natural Warning That Tells a Diver of Hypoxia Carbon Dioxide Excess (Hypercapnia) excess of carbon dioxide in the tissues can occur the process of carbon dioxide transport and elimina- tion paragraphs. No There of the is interrupted or modified. In diving, carbon diox- because there is too much carbon dioxide in the diver's breathing medium or because the carbon dioxide that is produced is not eliminated properly. The diver's own metabolic processes are generally the source of any excess carbon dioxide. The proper carbon dioxide level is maintained in the body by respiration rapid enough to exhale the carbon ide excess occurs either Hypoxia The term hypoxia, or oxygen shortage, is used to mean any situation in which tissue cells fail to receive or are unable to obtain enough oxygen to maintain 3.1.3.1 their normal functioning. Hypoxia can occur as a result of interference with any phase of the oxygen transport dioxide produced and delivered to the lungs. For breath- process. ing to be effective, the air inhaled Hypoxia stops the normal function of tissue cells are the most susceptible of all Brain cells. body cells to minimum must contain a mask mouthpiece or of carbon dioxide. Inadequate helmet or ventilation, too large a dead space in hypoxia; unconsciousness and death can occur before tubing, or failure of the carbon dioxide absorption the effects of hypoxia are apparent on other cells. system of closed- or semi-closed-circuit breathing systems may produce an excess of carbon dioxide in Hypoxia may cause sudden unconsciousness is gradual, may or, if onset decrease the ability to think clearly, orient oneself, or to perform certain tasks. Confusion and difficulty standing, walking, and maintaining in may the gas breathed. All tissues are affected by an excess of carbon dioxide, but the brain the most susceptible organ to is be hypercapnia. Figure 3-4 shows the physiological effects unaware of impending trouble even though they become of different concentrations of carbon dioxide for vari- coordination often follow. Victims of hypoxia drowsy and weak. that as A particular danger of hypoxia progresses, it may being that it is causes a false sense of well- prevent the diver from taking correc- ous exposure periods. At the concentrations and durations represented effects have by Zone I, no perceptible physiological been observed. In Zone II, small threshold severe and sud- hearing losses have been found and there den, unconsciousness develops almost at once; un- ble doubling in the depth of respiration. tive action soon enough. If consciousness usually occurs pressure of oxygen lent to the falls hypoxia when to 0.10 is the inspired partial atmosphere, i.e., oxygen pressure prevailing when equiva- a person breathes a 10 percent oxygen mixture at atmospheric pressure. Below this level, permanent brain damage and death occur quickly (US Navy 1985). If a diver suffering from severe hypoxia not res- October 1991 — NOAA If will given fresh air Diving Manual a percepti- Zone symptoms In III, are mental depression, headache, dizziness, nausea, 'air hunger,' and a decrease in visual discrimination. Zone IV represents marked physical distress associated with dizziness and stupor, which is accompanied by an inability to take steps for self-preservation. is cued quickly, the interference with brain function cause failure of breathing control. the zone of distracting discomfort, the is stage of the Zone IV state CO., partial pressure is The final Above a of 0.15 ATA, muscle unconsciousness. (PCOJ spasms, rigidity, and death can occur. If an excess of 3-5 Section 3 Figure 3-4 Relation of Physiological Effects to Carbon Dioxide Concentration and Exposure Period < < 10 10 \ Zone IV Dizziness, stupor, unconsciousness o 0.08 0.06 \ Zone III 8 < 5 6 .£ Distracting discomfort c A 0.04 ^^^^ Zone II Zone I No 3 o CM O O 2 .o """""""——««», Minor perceptible changes 0.02 o « c • c o effect 0.5 I 0.00 I I I I I 30 40 50 60 70 I 20 10 PC0 2 ATA 40 Days Exposure Time, minutes Derived from NOAA (1979) carbon dioxide causes a diver to lose consciousness, he differences in individual responses to increases in car- or she can be revived quickly bon dioxide. The amount of work, the depth, and the with fresh air. The if the lungs are ventilated aftereffects of hypercapnia include headache, nausea, dizziness, and sore chest muscles. The bar graph at the right of Figure 3-4 extends the period of exposure shown to 40 days. for exposures of It illustrates that, 40 days, concentrations of carbon dioxide in air of less than 0.5 percent (0.005 ATA breathing medium are factors that will also alter the effect of an increase in carbon dioxide on breathing. Deliberately reducing one's breathing rate will cause a carbon dioxide buildup; maintaining an adequate ventilation rate necessary to remove carbon dioxide is from the lungs effectively. Other conditions that increase (Zone A) cause no biochemical or the likelihood of carbon dioxide poisoning include severe other effects; concentrations between 0.5 and 3.0 per- exertion, high partial pressures of oxygen, high gas partial pressure) cent (0.005-0.03 ATA partial pressure) adaptive biochemical changes, which (Zone B) cause may be consid- and the use of breathing apparatus that has excessive dead space or high breathing resistance. density, ered a mild physiological strain; and concentrations above 3.0 percent (0.03 ATA partial pressure) (Zone C) cause pathological changes in basic physiological functions. For normal diving operations, ventilation rates should be tial maintained so that carbon dioxide par- pressures are maintained in Zones short-term exposures and in Zones A I and II for and B for long- WARNING Skip-Breathing Is Not a Safe Procedure Because Carbon Dioxide Buildup Can Occur With Little or No Warning term exposures. Increased carbon dioxide in the breathing-mixture stimulates the respiratory center to increase the breathing rate. Carbon dioxide at a partial pressure of 0.02 the carbon dioxide level reaches a partial pressure of 0.05 atmosphere, an uncomfortable sensation of shortness of breath occurs. 3-6 There are large Carbon Monoxide Poisoning Inspired carbon monoxide atmo- sphere generally increases breathing noticeably. When 3.1.3.3 (CO) combines with hemothem incapable globin in the red blood cells, rendering of carrying oxygen to the tissues. bound When carbon monoxide hemoglobin, a person experiences tissue hypoxia (oxygen deficiency in the tissues) even though is to NOAA Diving Manual — October 1991 Diving Physiology the air being breathed has sufficient oxygen. This con- CO monoxide (40,000 ppm). The average carbon monoxide Hemoglobin combines with carbon monoxide about 210 times more concentration inhaled during the smoking of one cigarette readily than with oxygen, so very small concentrations 7.0 percent dition known is as poisoning. monoxide can be dangerous to life (US Navy The hemoglobin-carbon monoxide combination is 400-500 ppm, which produces anywhere from 3.8 to carboxyhemoglobin (HbCO) in the blood; is of carbon in 1985). cent. red in color and may cause an unnatural redness of the However, since this redness may not occur, carbon monoxide poisoning cannot be ruled out lips and skin. non-smokers, the The percentage HbCO level is generally 0.5 of HbCO blood levels after per- con- tinuous exposure to carbon monoxide for 12 hours or after reaching equilibrium are summarized in the table below. simply because a person has normal coloring. In addition to its oxidase a > monoxide enzyme (cytochrome effects on hemoglobin, carbon combines with the final respiratory Continuous Exposure as well. level Because carbon monoxide poisoning feres with the delivery of symptoms oxia. to is 50 40 may 8.4 6.7 30 20 high cause rapid poisoning without the diver's awareness, he or she Blood inter- are identical to those of other types of hyp- monoxide in % ppm CO, to the tissues, the the concentration of carbon If enough If oxygen HbCO Level of causing hypoxia at the tissue in the tissues, f 5.0 3.3 10 1.7 — lose consciousness suddenly. 0.5 (non-smoker) monoxide poisoning is more gradual in pounding headache, nausea, and vomiting may the carbon onset, Source: NOAA (1979) occur. A diver's breathing gas can be carbon monoxide if contaminated by the compressor supplying the breath- draws from an area where the ing gas air is contami- nated by the exhaust from a gasoline or diesel engine or if vapor from the oil used to lubricate the compressor gets into the air supply. It is essential that the air intakes on compressors be protected to avoid this source of carbon monoxide contamination and that appropriate flash point is used in oil with an any oil-lubricated compressor that supplies divers' breathing air (see Sec- a diver loses consciousness, it is routine to administer recompression treatment because of fear that either decompression sickness or an arterial gas embolism has caused the loss of consciousness. Occasionally, carbon monoxide poisoning is the cause of unconsciousness, and recompression treatment, using either USN Treatment Table 5 (Oxygen Treatment of Type I Decompression Sickness; US Navy 1985) or a hyperbaric oxygen treatment table designed specifically to treat carbon monoxide poisoning, is the treatment of choice in these cases as well. Carbon monoxide poisoning victims who resume breathing and regain consciousness quickly have a good chance of complete recovery. 3.1.3.4 Smoking Smoking 20 ppm directly affects the oxygen-carrying capabil- ity of the red blood cells. The smoke of a typical American cigarette contains about 4 percent carbon October 1991 — NOAA Diving Manual carbon monoxide for 12 hours (equivalent to the maximum carbon monoxide level allowed in divers' breathing air by the U.S. Navy (see Table 15-6)). Considering that it takes a heavy smoker approximately 8 hours to eliminate 75 percent of the carbon monoxide inhaled, it is clear that the HbCO level (0.95 percent) smoker diving 8 hours after the last cigarette is almost twice that of a non-smoker (0.50 percent). The carboxyhemoglobin blood level of a passive smoker (i.e., a person who does not smoke but who is exposed to the smoke of others) can rise to even for tion 4.2.2). When Table 3-1 shows the relationship between smoking and HbCO blood levels. This table shows that the HbCO level in the blood of divers who smoke is higher than it would be if the divers had been exposed to 5 a light percent after exposure to a smoke-filled environment (Surgeon General 1986). The dose smoking is of carbon toxic; psychomotor it test monoxide a causes changes results, smoker receives from in neurologic reflexes, sensory discrimination, and electrocardiograms, as well as fatigue, headache, irri- and disturbed sleep. Other shortterm effects of smoking may also adversely affect the diver. For example, in addition to accelerating the atherosclerotic changes in blood vessels, cigarette smoke also raises blood pressure and increases heart rate. Smokers have trouble eliminating respiratory tract secretions, and the accumulation of these secretions can make equalizing pressure in the ears and sinuses difficult (Shilling, Carlston, and Mathias 1984). The irritants in inhaled tobacco smoke can cause an increase tability, dizziness, 3-7 Section 3 Table 3-1 Carboxyhemoglobin as a Function of Smoking ence the amount of breathing resistance encountered Median HbCO Smoking Habits Level, Expired % CO, ppm by a diver using the equipment. Gases moving through tubes of optimal design will flow 'in line' or in laminar flow until restrictions in or the dimensions of the tube Light smoker cause the air molecules to begin moving pack/ (less than Vz day) 3.8 Moderate smoker (more than Vz pack/day and less than 2 packs/day) Heavy smoker (2 packs or more/ 17.1 fashion {turbulent flow). 5.9 27.5 laminar flow 6.9 32.4 required to day) Source: NOAA (1979) move gas is that in a The increase in is disordered in the effort turbulent rather than significant: the resistance increases in relation to the square of the increased flow rate; that is, doubling the flow rate causes a fourfold increase in resistance (see Section 2.6). This may be a problem with small-bore snorkels, small-diameter exhaust valves, mucus and a chronic inflammatory change in Over a prolonged period, these conditions may result in structural weakness of the lung, such as emphysematous bullae, alveoli enlarged in bronchial the bronchial lining. with air, Lung or obstructive lung disease. cysts can enlarge because of gas trapped by bronchial obstruc- and may then rupture. The resulting tears can open into pulmonary veins, permitting gas embolism. Furthermore, nicotine and carbon monoxide increase tion the 'stickiness' of blood platelets, causing a clumping that can interfere with the flow of blood in the small vessels; this condition tibility to Navy may increase a person's suscep- decompression sickness. In divers, cigarette a study of 93 smoking was found to be associated with lung function decrement and to have an important and adverse effect on divers' health (Dembert et al. 1984). Other Navy research reported by Dembert and co-authors suggests that there is an association between smoking and the risk of decompression sickness. The or inadequate breathing tubes and mouthpieces. Thus, snorkels should have diameters approximately 3/4 inch (1.9 centimeters) with no unnecessary bends, corruga- tions, or obstructions, and exhaust valves should be enough large to keep the exhalation resistance as low as possible (see Sections 5.1.1.4 The position of the demand and relation to the internal pressure in the lungs in closed-circuit spiratory system clearly indicate that divers should smoking altoavoid smoking for several (Figure 3-5). As the work-of-breathing level in the tissues (US Navy 1985). Excessive Dead Space Dead space in a diving system 3.1.3.6 residual exhaled air remains. some A is A A of well-designed system has work-of-breathing in (i.e., ume by the amount breathing) to some extent. If the breathing resistance of the apparatus difficult to breathe is high, it will be adequately even during ordinary exertion and breathing will become impossible during hard work. Resistance to the flow of breathing gas is caused by demand regulators, valves, hoses, and other appurtenances of a life-support system. Well-designed equipment minimizes the amount of resistance flow of breathing gas (see Section The 5. 1 . 1 . determining how must this ineffective vol- much exhaled gas is actually rebreathed. Full-face dead space; breath masks may add as much as 0.5 liter of this excess must be ventilated with each (US Navy 1985). Because of carbon dioxide buildup, the excess can seriously limit a diver's ability to do work. Free-flow helmets do not have this dead space problem. The use of oral-nasal masks inside full-face masks is effective in reducing the amount of dead space (see Section 5.2.1). to the 3.1.3.7 Hyperventilation 1 ). characteristics of the breathing gases flowing through tubes of various sizes and configurations 3-8 minimum dead not reveal dead space volume; special equipment breathing apparatus used by a diver under water work involved mask may return amount casual examination of diving equipment will be used to measure the extent of Excessive Resistance to Breathing which returned depends on the dead space volume within the space. Any that space in diver exhaling into a of this exhaled gas to the lungs; the gether, they should at least will increase the increases, the body reaches a point where it will accept increased carbon dioxide rather than perform the respiratory work required to maintain a normal carbon dioxide system. 3.1.3.5 critical pressure causing an increase in breathing resistance not smoke. If divers are not able to stop hours before diving. is scuba to avoid unbalanced hydrostatic snorkel, mouthpiece, or full-face deleterious effects of smoking on the cardiore- 5.6.1). valve or breathing bag in influ- The (C0 ) 2 and Breath-holding respiratory system utilizes both carbon dioxide and oxygen (0 2 ) tensions NOAA (partial pressures) in Diving Manual — October 1991 Diving Physiology Figure 3-5 on Location Bags Within a Closed-Circuit Scuba Effects of Hydrostatic Pressure of Breathing Breathing bag subject to is more deeper than the lungs. It is hydrostatic pressure, increasing breathing resistance on exhalation. Breathing bag is at the same level as the lungs. Breathing resistance is the same as on the surface. Breathing bag is shallower than the lungs. It is subject to less hydrostatic pressure, increasing breathing resistance on inhalation. Source: the body to regulate the process of breathing. Rising CO, tension and falling O, tension are monitored by biological sensors in the body, the breathing response when which normally trigger the appropriate levels are reached. Hyperventilation (rapid, unusually deep breath- ing in excess of the necessary rate for the level of normal operation of the mechanism. Hyperventilation lowers the CO, level in body tissues to levels below normal, a condition known as hypocapnia, which initially causes a feeling of lightheadedness and may cause weakness, faintness, headache, and blurring of vision activity) interferes with the respiratory control over a longer period. Hyperventilation in distance underwater swimming or breath-holding competitions, is or spasm occurs Some unconsciousness before the CO, fall may drown. tion. Divers who notice that they are hyperventilating should take immediate steps to slow their breathing ly. and, if feasible, ascend prompt- After reaching the surface, they should inflate their buoyancy compensators. Hyperventilating divers should because they hyperventilation, oxygen levels can water, the diver more susceptible to hyperventilation-induced hypocapnia than others; however, sufficiently prolonged hyperventilation induces unconsciousness or muscle spasms in most individuals. Both scuba and surface-supplied divers should be aware of the problems associated with hyperventila- dioxide level without significantly increasing the oxy- in in the individuals are not attempt to breath-holding after and may cause uncon- sciousness or muscle spasms. If either unconsciousness a dangerous practice. Hyperventilation lowers the carbon When (1979) often initiated by anxiety or physi- cal stress or outright panic rate, notify their buddies, Voluntary hyperventilation, which occurs gen level of the blood. is NOAA swim may to a boat or the shore unaided lose consciousness in the attempt. During surface-supplied diving, the tender should to levels resulting continuously monitor the diver's breathing for signs of high enough hyperventilation. Divers starting to hyperventilate should level is As a consequence, competiunderwater breath-holding events should be discouraged (Bove 1985). Once on to stimulate respiration. be asked to stop work and tive ing the breath for short periods will aid in replenishing October 1991 — NOAA Diving Manual low CO, levels rest. the surface, hold- and may avert further complications. 3-9 Section 3 3.2 EFFECTS OF PRESSURE The effects of pressure on divers may be divided into two principal categories: (1) those that are direct and mechanical; and (2) those that come about because of changes in With the partial pressure of inspired gases. each 2-foot (0.61 meter) increase depth of sea- in the water, the pressure increases by almost Each psi. 1 The many changes in pressure regularly involved in diving make a pressure-sensitive middle ear a liability for a diver. The immersion on the human ear causes it under water than it does in air. effect of to function differently Normally, sound is compressed) high-amplitude in a transmitted in air (which (HA) low is easily force mode. 33 feet (10 meters) of descent in seawater increases the In liquid (which pressure by an additional atmosphere (14.7 transmitted in a low-amplitude (LA) high force mode. The lungs and psi). respiratory passages contain air at times. In addition to the major air channels, all which include the nose, mouth, throat, larynx, and trachea, there are a number of side compartments issuing from The human ear difficult to compress), is designed to convert is HA of sound in the external and middle however, sound arrives at the ear the upper respiratory passages that are important in back When occur the exposed to pressure changes, such as those that is in diving, air contained in these cavities compression because the pressure of the undergoes to LA is As not efficient. ear. In water, LA mode, LA to HA and and a result, the external/ middle ear mechanisms are functionally bypassed under water and hearing primarily achieved by bone (skull) is conduction. When air delivered by the breathing supply must be equilibrated with the pressure of the surrounding environment. The pressure LA energy to in the diving physiology. These include the eustachian tubes, body is energy (see Figure 3-6) by the mechanical processing the process of converting sound from the middle ear, and the paranasal sinuses. sound divers experience extreme changes in ambient may pressure, the ears be injured unless the pressure of air breathed into and out of the lungs and respiratory between the air-containing cavity and the ambient atmosphere is equalized. Barotitis media (middle ear accordance with changes squeeze) resulting from inadequate pressure equaliza- passages thus also changes in the surrounding hydrostatic pressure. in between the middle ear and the ambient pressure common problem among divers. Although occasionally disabling, it is usually reversible. Because more people are diving to deeper depths, there have tion is 3.2.1 Direct Effects of Pressure During Descent Humans can tolerate increased pressures if they are uniformly distributed throughout the body. However, when the outside pressure is different from that inside the body's air spaces, this difference in pressure shape of the involved distort the This ry. is may causing inju- tissues, in been more serious and disabling problems involving the inner ear. In terrestrial environments, balance and such spaces as the sinuses and the middle ear must be equalized on descent, or pressure spatial ori- entation depend on input to the central nervous system from the visual, proprioceptive (sense of touch), vestibular (sense of balance) systems. called barotrauma. The pressure a fairly work beneath the sea, visual When and people and proprioceptive cues are frequently distorted; thus, spatial orientation and differences will develop across the walls of these spaces. balance become more dependent on information received Once from the vestibular system. Vestibular system dysfunc- it the pressure at a given depth has been equalized, must be allowed to decrease if decreases, as occurs during ascent. the external pressure The effects of pressure on various parts of the body are discussed in the following paragraphs. tion may occur in many phases of diving, and the subsequent vertigo, nausea (and, occasionally, vomiting) can be life threatening. The middle ear space (Figure cell systems in the skull 3-6) connects with air bone containing the ear. With an intact eardrum membrane, the only communication 3.2.1.1 The Ears between this system and the ambient atmosphere is The air-containing external and middle ear gives humans a device that efficiently transforms airborne through the eustachian tube. This tube sound energy leads from the middle ear to the nasopharynx (or upper this energy is to the fluid-containing inner ear, where transduced into electrical signals. Proper functioning of this mechanism requires that both the external ear canal and the middle ear contain air and that differences in pressure be avoided between these structures and the ambient atmosphere or inner ear. 3-10 1.4 to 1.5 inches (3.5 to 3.8 cm) long is approximately in the adult and expanded portion of the throat) behind the nasal caviThe nasopharyngeal opening normally is closed by positive middle ear pressure, or, when opened during swallowing, by muscular action on the surrounding ties. cartilage. NOAA Diving Manual — October 1991 Diving Physiology Figure 3-6 Principal Parts of the Ear drum Semicircular canals or inner ear may occur with as as 3 pounds and they may little (1.3 kilograms) of pressure differential, happen anywhere in the water column. WARNING Because Of The Danger Of Round Window Rupture, A Maneuver Should Forceful Valsalva Not Be Performed During Descent The inner ear consists of a system of fluid-filled bony channels within the temporal bone (Figure 3-6). Membranous structures that are divided into two parts, the vestibular system containing the semi-circular canals and the auditory system, are located in these channels. These two systems are interconnected and have a common blood supply. Changes in cerebrospinal fluid pressure EAR can be transmitted directly to the inner ear compartments, and therefore any maneuver such as straining, The air-containing external auditory canal, middle ear, chian tube are noted. The the perilymphatic fluid-filled inner ear and eusta- subdivided into is and endolymphatic spaces, which connect to the subarachnoid space by the cochlear duct and endolymphatic duct, respectively. Source: Bennett and Elliott (1982) with the permission of Bailliere Tindall, Ltd. or trying to clear the ears against closed nasal lifting, passages can cause increased pressure in the ear's fluidfilled compartments. Marked pressure changes may cause ruptures between the inner and middle ear, leading . to vertigo and hearing loss; this may happen even in shallow exposures. The eustachian tube In general, is lined by epithelium that similar to the lining of the nose, sinuses, ynx. Abnormal is and nasophar- nasal function can be caused by acute or chronic inflammatory diseases, allergy, chronic irrita- from excessive smoking or prolonged use of nose drops, or chronic obstruction from internal or external tion nasal deformities or lesions. Nasal dysfunction may contribute to inadequate eustachian tube function, which may cause middle or inner ear barotrauma in divers (Sections 20.3.2 and 20.3.3). Descent usually causes greater difficulty in equalizing the ear than ascent because the air passes from the middle ear more easily than into the middle ear from As descent or compression proceeds, the nasopharynx. middle ear pressure must be equalized constantly to prevent middle ear barotrauma with possible eardrum rupture or inner ear injury caused by rupture of the round window (see Figure 20-1). Successful methods of equalizing middle ear pressure are swallowing, yawning, or gently blowing against a closed mouth and nostrils. Forceful blowing (valsalva maneuver) should never be done because, if the middle ear pressure is already negative, forceful blowing, which causes an any individual who has difficulty with middle ear ventilation at the surface should not dive. Furthermore, individuals who have chronic nasal obstruction or a history of frequent upper respiratory infections, nasal allergies, mastoid or ear disease, or chronic sinus trouble should have a complete otolaryngological evaluation before diving. Also, individuals who have an upper respiratory infection of any kind should not dive until the infection has cleared. Systemic and topical drugs may improve nasal function and sinus and middle ear ventilation. However, divers should use such agents cautiously because the rebound phenomenon that occurs after the drug, and especially topical nose drops, wears off may lead to greater nasal congestion and even greater equalization problems in the ears and sinuses. Prolonged use of topical nasal medications can cause chronic nasal irritation. For safe diving, equalization problems must be avoided. For example, if a diver cannot clear his or her ears on the surface, he or she should not dive. Some steps to be followed during descent are: • Descend feet first, preferably line or a drop line. It is down the anchor easier to equalize middle increase in cerebrospinal fluid and inner ear pressure, ear pressure in the upright position because drain- may age rupture the round window. Injuries to the ear- October 1991 — NOAA Diving Manual is more effective in this orientation. 3-11 Section 3 Figure 3-7 Location of Sinus Cavities • Clear the middle ear early, actively, and conscientiously during descent. Clearing by forceful blowing against a closed mouth and nose should be • Stop the descent avoided, if ( possible. if ear blockage or fullness devel- symptoms ops; the diver should ascend until these have cleared, even if return to the surface Descent should not be continued is required. until ear pain develops. Inner-ear decompression sickness (also called vestibular decompression sickness) has occurred with no symptoms other than vertigo, ringing in the ears, or nausea (Farmer 1976). Vestibular decompression sickness commonly seen more is after deep helium-oxygen dives, particularly after a switch to air in the later stages of decompression, although shallower air diving. in Any also has occurred it diver with such symptoms Orbit Of Eye during descent or compression should be considered as having inner ear barotrauma, including possible rupture of the oval and round windows, and should not be recompressed. Recompression would again subject the diver to unequal middle ear pressures. However, even if Maxillary Sinus these precautions are heeded, hearing impairment can develop as a result of diving. For this reason, divers should have annual audiometric examinations. ( NOTE Any diver with ringing or roaring in the ears, loss of hearing, vertigo or dizziness, or nausea or vomiting during or shortly after decompression from a dive should be treated as having inner-ear decompression sickness. The Sinuses 3.2.1.2 The sinus cavities are shown in Figure 3-7. Although paranasal sinus barotrauma occurs only rarely in divers, inflammation and congestion of the nose, nasal deformities, or masses can cause blockage of the sinus opening. This blockage leads to a series of changes within the cavities, consisting of absorption of pre-existing gas, vacuum formation, Maxillary Sinus swelling, engorgement, inflamma- tion of the sinus lining, or collection of fluid in the sinus cavity. When such blockage occurs during descent in diving or flying, the intra-sinus vacuum becomes greater and the resulting pathological changes are severe; there in some may more Opening To Pharynx Eustachian Tube be actual hemorrhage into the sinus instances. Paranasal sinus barotrauma also occurs during ascent; the mechanism of this trauma appears to be a blockage ( of a one-way valve of the sinus by inflamed mucosa, cysts, or polyps, 3-12 which permits pressure equalization Source: NOAA Diving Manual NOAA (1979) —October 1991 Diving Physiology Figure 3-8 Pressure Effects on Lung Volume during descent but impairs it during ascent. The symptoms and management of paranasal sinus barotrauma are discussed in Sections 20.2.1 and 20.3. The Lungs As long as normal breathing takes place and the ample, the lungs and airways will 3.2.1.3 breathing supply is equalize pressure without difficulty. If divers hold their breath during a pressure increase, no difficulty arises until the total compressed to less volume of air in the lungs is than the residual volume. Once the in the lungs becomes less than the residual volume, pulmonary congestion, swelling, and hemor- volume rhage of the lung tissue occurs; this condition is called thoracic squeeze. Figure 3-8 graphically illustrates the effects of pressure on lung volume. In breath-hold diving, no high-pressure air able to the lungs. Pressure compresses and Law (P fall in lung volume, the effects of Boyle's i.e., V =P,VJ. Lung volume tolerable compression. will avail- diaphragm; pressure equalization results raises the from the is the diver's chest Descending limits the extent of to 33 feet (10 meters) reduce lung volume by one-half. Compression down volume (the amount of air in the lungs after forceful expiration) can be tolerated; however, when chest compression exceeds this limit, tissue trauma occurs. Fluid from the capillaries and tissues then enters the alveoli and the air passageways and may to residual At the surface Atmosphere Absolute, 4.7 psi. The lungs are expanded with a full breath of air. 1 1 fully cause gross hemorrhaging. Mild lung barotrauma causes only pain and a slight exudation, which reabsorbed, but is the lungs quickly may be damaged. This form of trauma generally responds well in serious cases, to conservative treatment consisting of general supportive care, prevention of infection, and intermittent positive- pressure inhalation therapy. Spraying with bronchodilators may and aerosols and inducing gravitational drainage prove beneficial if hemorrhage or bruising has been severe. The use of a breathing inspiratory resistance apparatus that has a high may cause pulmonary edema (increased fluid in the tissues of the lungs). In an effort to maintain adequate lung ventilation during moder- ate activity, the small veins of the lungs aged, fluid may may be dam- seep through the membranes, and the may rupture. In addition, gas exchange can be hampered, which increases the risk of decompression sickness. Coughing and shortness of breath are symptoms of this condition, and x rays of the chest may show patchy pulmonary infiltration, which usually clears alveoli At 33 Feet 2 Atmospheres Absolute. 29.4 hydrostatic pressure, the lungs is reduced to only Vi psi. Because same volume its of of air in the surface volume. within 24 hours without specific therapy. The lungs can be traumatized during the compression phase of a dive or treatment October 1991 — NOAA if an individual stops Diving Manual Source: NOAA (1979) 3-13 Section 3 may breathing, either voluntarily by breath-holding or invol- overexpansion and overpressurization of the lungs untarily because of windpipe or tracheal obstruction cause progressive distension of the alveoli. This over- or convulsions. distension may be general, which occurs with breath- holding or insufficient exhalation, or localized, which 3.2.1.4 happens with partial or complete bronchial obstruc- The Teeth tion Pain in the teeth (harodontalgia) can occur in diving and may be caused either by referred pain from the paranasal sinuses or by tooth squeeze. This latter condition, athough uncommon, is caused by a variety of dental conditions, such as new lesions or a lesion that has developed around the edge of an old filling (recur- (Rottman 1982). Tooth squeeze is not caused trapped in a filling. Other causes of tooth squeeze rent decay) by air include recent extractions, gum infections that have formed periodontal pockets, large areas of decay where is infected, and recent fillings. Tooth squeeze the pulp can also occur if is mucus, of any type. Problems of lung overinflation can occur during ascent from depths as shallow as 4-6 feet (1.2-1.8 meters) if the breath is held. Several of the most commonly encountered physiological difficulties associated with pressure during ascent are described paragraphs; each may be prevented by breathing normally during ascent, providing there is no localized airway obstruction. Figure 3-9 shows the in the following possible consequences of overinflation of the lungs. to dry and seal the canal between treatments with a material is lesions, a person dives while undergoing root canal therapy. Part of the root canal procedure that caused by the presence of bronchial bronchospasm. For this reason, individuals with bronchial asthma should not do compressed gas diving or WARNING designed to be adequate at a pressure of one atmosphere. Exposure to higher pressures, however, can produce small leaks in this Do Not Hold Breath While Ascending material that are not able to release air fast enough during subsequent ascent. Like other squeezes, tooth squeeze usually subsides 3.2.2.1 Pneumothorax Distended alveoli or (emphysematous sphere. This when the ambient pressure is reduced to one atmomechanism also may be the explanation blebs) for tooth explosion (Rottman 1982). Gas that has accumulated slowly during a saturation dive can cause is tooth explosion during or after decompression. gas expands as the diver surfaces, causing increased may (pleura), air-filled blisters membrane lining of the chest causing pneumothorax. Under pressure, this rupture the extremely dangerous because trapped intrapleural pressure in the chest cavity. The lungs may be lapsed by this pressure, and the heart 3.2.2 Direct Effects of Pressure During Ascent is if the breath is held or there a localized airway obstruction, the expanding air retained, causing overinflation col- be pushed its normal position. Symptoms and signs include sudden severe pain, reduction of breathing capability, and, rarely, coughing of frothy blood. The rapid onset of pneumothorax can cause sudden out of During a pressure decrease (e.g., during ascent), the air in the body cavities expands. Normally, this air vents freely and there are no difficulties. If breathing is normal during ascent, the expanding lung air is exhaled freely. However, may is and overpressurization of the lungs. For example, the air in the lungs at a depth of 66 feet (20.1 meters) gradually expands to respiratory and circulatory difficulty, impaired car- diac function, or death from shock. Early diagnosis and prompt treatment with thoracentesis (chest puncture) are essential. If recompression is required for concomitant conditions, the pneumothorax must be vented or released by a chest tube or other device before ascent is accomplished. WARNING 3.2.2.2 A Who Has Experienced Blowup (or an Overpressure Accident) Must Immediately Be Examined by a Physician Diver Mediastinal Emphysema Mediastinal emphysema is the result of air being forced into the tissues about the heart, the major blood vessels, and the trachea (windpipe) in the middle of the Gas trapped in the spaces between tissues may expand rapidly with continuing decompression, causing impaired venous return. The symptoms of mediastinal emphysema are pain under the sternum (breastbone) and, in extreme cases, shortness of breath or chest. volume during ascent to the surface (see air volume can expand safely to the point of maximum inspiration, assuming there is no three times Figure 3-8). its The airway obstruction. 3-14 If the pressure decreases further, NOAA Diving Manual — October 1991 Diving Physiology Figure 3-9 Complications From Expansion of Air in the Lungs During Ascent fainting caused by circulatory interference resulting vessels. The emphysema is from direct pressure on the heart and large treatment for mild cases of mediastinal symptomatic. In more severe cases, oxygen inhalation may aid resolution of the trapped gas. For severe, massive mediastinal emphysema, recompression is Cerebral Gas Embolism required. Air Passes Via Carotid Arteries To Brain Subcutaneous Emphysema may be associated mediastinal emphysema, is caused by air being 3.2.2.3 Subcutaneous emphysema, which with Mediastinal forced into the tissues beneath the skin of the neck Emphysema extending along the facial planes from the mediasti- num. Unless it is extreme (characterized by a crack- ling of the skin to the touch), the only symptoms of subcutaneous emphysema are a feeling of fullness in the neck and, perhaps, a change in the sound of the voice. Having the victim breathe oxygen will acceler- ate the absorption of this subcutaneous air. Gas Embolism 3.2.2.4 The most tion serious result of nary venous system. This gas Air Passes Along Air Enters- Bronchi To Pleural Cavity Mediastinum (Pneumothorax) Air Enters Blood Vessel pulmonary overpressuriza- the dispersion of alveolar gas into the pulmo- is is carried to the heart and then into the arterial systemic circulation, causing gas emboli (gas bubbles) in the coronary, cerebral, and other systemic arterioles. These gas bubbles continue expand as the pressure decreases, which in turn makes the clinical signs more severe. (Section 20.4.2 describes the symptoms of arterial gas embolism in to detail.) The Alveoli lism Expanded clinical features of may traumatic arterial gas embo- occur suddenly or be preceded by dizziness, headache, or a feeling of great anxiety. Unconsciousness, and convulsions follow quickly. Motor and in different combinations. Death is caused by coronary cyanosis, shock, and sensory deficits occur in various degrees or cerebral occlusion with cardiac arrhythmia, respiratory failure, circulatory collapse, examination of a person with and shock. Physical a gas embolism may reveal: (1) focal or generalized convulsions; (2) other neurological abnormalities; (3) marbling of the skin; Alveoli Normal bubbles (4) air j^ in the retinal vessels of the eye; (5) hemoptysis; or (6) Liebermeister's sign (a sharply defined area of pallor in the tongue). Temporary obstruction of an air passage, which can occur with a cold or bronchitis, increases the risk of gas embolism, and diving with a respiratory infection should therefore be avoided. A person with bronchial asthma has hyper- reactive small airways in the lung. Breathing dry compressed Source: October 1991 — NOAA Diving Manual NOAA (1979) air, aspiring salt water or cold water, exercising, or being anxious can all cause a bronchospasm 3-15 Section 3 under water. Ascent with local air trapped in the alveoli could cause a pressure imbalance and rupture, resulting in gas embolism. For this reason, bronchial asthma is a contraindication for compressed gas diving, regardless of how well the asthma is controlled by medication. Coughing or sneezing while in a recom- strict pression chamber or while ascending during a dive can embolism. Divers should stop their they feel a cough or a sneeze coming on, and ascent to expel gas by belching or passing An tum. may during ascent cause marked discomfort and vaso- foods before diving is not recommended. If a diver swallows enough air, he or she may have difficulty may breathing and then panic. Accordingly, activities that cause air swallowing, such as ascents avoided during diving. chamber operators should stop the chamber ascent they are notified that an occupant of the chamber The only effective treatment for gas A is patient should be kept in the which may help to keep bubbles embolism Bubble Formation and Contact Lenses The use of contact lenses by divers has increased 3.2.2.6 is significantly in recent years. For this reason, studies position, in the circulation reaching the brain. Placing the patient on the helps to maintain cardiac output, which may from left side be impaired because the gas bubbles have decreased the efficiency of the pumping action of the heart (see Figure 19-9). In non-fatal cases, residual paralysis, myocardial necrosis, may occur recomnot carried out immediately and may even and other ischemic injuries pression is occur adequately treated patients in in initiating therapy. if there if is a delay Hyperbaric chambers that can- not be pressurized to 6 ATA chewing, should be if merely symptomatic. head-down gum is about to cough or sneeze. recompression; other treatment per rec- vagal effects. Eating large amounts of gas-producing also cause a gas if it excess of gas in the stomach or intestine are not as effective for embolism treatment as those with this capacity, but recompression to 2 or 3 ATA is far better for the embolism patient than no recompression. have been done to determine the inherent dangers of using them, especially during decompression (Simon and Bradley 1981). Three types of contact lenses were compared, membrane (soft) lenses and two types of polymethylmethacrylate (hard) lenses. One type of hard lens (fenestrated) had a 0.016 inch (0.4 millimeter) hole in the center, while the other type (non-fenestrated) was sions solid throughout. from 149 During controlled decompres- feet (45.5 meters) in a hyperbaric cham- wearing the non-fenestrated hard lenses ber, subjects developed small bubbles in the precorneal tear film under the contact lens. These bubbles, first observed at 70 feet (21.3 meters), increased both in number and decompression progressed. The divers wearing size as these hard lenses experienced soreness, decreased vis- ual acuity, and reported seeing halos when viewing These symptoms were noted at the time of bubble formation and persisted for about 2 hours after return to sea level (Simon and Bradley 1981). No bubbles were noted under the same decompression conditions when the divers wore the fenestrated hard lens, lights. WARNING Central Nervous System Decompression Sickness Is Clinically Similar to Gas Embolism and the Treatment of Either Requires a Recompression Chamber membrane lens, or no lens at all. The authors of this study concluded that the soft the bubble formation was caused by the lack of permeability of the hard non-fenestrated lens (Simon and Bradley In cases of gas embolism, administering oxygen and positioning the body (head-down at a 15 degree angle) are only partially effective; drugs and fluids also be helpful. These measures should be used val before the patient reaches a may It is recommended, therefore, that divers electing wear contact lenses use either soft membrane lenses 1981). to or hard fenestrated lenses. in the inter- recompression cham- 3.2.3 Indirect Effects of ber (see Section 20.4.2). The in the partial 3.2.2.5 Overexpansion of the Stomach and Intestine The stomach and large intestine ordinarily contain 1.06 quarts (1 liter) or more of entrapped gas. Since Pressure indirect effects of pressure are caused by changes pressures of the gases in the breathing medium. These effects include saturation and desat- uration of body tissues with dissolved gas and changes in body functions caused by abnormal gas tensions. the intestines are surrounded by soft tissues, the com- pression and re-expansion of these air bubbles are ordinarily neither hazardous nor noticeable. If one swallows air while diving, 3-16 it may be necessary during 3.2.3.1 Inert Gas Absorption and Elimination While breathing air at sea level, body tissues are equilibrated with dissolved nitrogen at a pressure equal to NOAA Diving Manual — October 1991 Diving Physiology the partial pressure of nitrogen in the lungs. During and thus causes exposures to altitude (low pressure) or tissues; in diving (high inert gas to be eliminated after a sufficient time, enough gas from body will have pressure), the partial pressure of nitrogen in the lungs been eliminated to change and the tissues will either lose or gain nitrogen to reach a new equilibrium with the nitrogen pressure in the lungs. The taking up of nitrogen by the tissues is called absorption or uptake; giving up nitrogen from the tissues is termed elimination. In air diving, nitrogen absorption occurs when a diver is exposed to an increased nitrogen partial pressure, and elimination occurs when pressure decreases. This process occurs when any inert gas is breathed. This process continued until the diver reaches the will Absorption consists of several phases, including the transfer of inert gas from the lungs and to the blood then from the blood to the various tissues through which The gradient flows. it for gas transfer partial pressure difference of the gas is the between the lungs and blood and the blood and the tissues. The volume of blood flowing through the tissues is usually small com- is surface safely. permit the diver to ascend further. On surfacing, the diver's body contains inert gas in supersaturated solution tissues, but this is normally safe if kept within proper decompression limits and if further pressure reduction, such as ascent to altitude, does not occur (see Section 14.8). The basic principles same for any are the of absorption and elimination inert gas breathed. However, there are differences in the solubility and rates of gas diffusion in water in tissues and fat. Helium than nitrogen and diffuses equilibration occurs the case for nitrogen. is much less soluble Thus, helium faster. somewhat more rapidly than is The advantages in using helium- oxygen rather than nitrogen-oxygen mixtures are pared to the mass of the tissue, but over a period of dom from narcosis and a decrease in breathing To develop mathematical models of gas time the gas delivered to the tissue will cause tissues, physiological theory postulates that the body composed of it to become equilibrated with that carried in solution by the blood. The rate of equilibration with the blood gas depends on the volume of blood flow and the respective capacities of blood and tissues to absorb the dissolved still some in is free- resistance. solubility in human several 'tissue compartments,' each having a different 'half time.' For example, a compartment with a half time of 10 minutes is one in which the tissues are 50 percent saturated with gas after For example, fatty tissues hold significantly more exposure to pressure for 10 minutes, while a 20-minute gas than watery tissues and will thus take longer than compartment would be 50 percent saturated in 20 minutes, and so on. Various characteristics of these theoretical compartments, such as their relative fattiness, gas. watery tissues to saturate or desaturate excess inert gas. The process tion. of elimination is the reverse of absorp- During ascent and after surfacing, the tissues lose are believed to account for these differences in tissue half times. excess inert gas to the circulating blood by diffusion, the gradient being the difference partial pressure in between the inert gas of inert gas that can be Decompression Sickness Decompression sickness (DCS) refers to the illness that may occur after a reduction in barometric pres- limited, so the tissue inert gas sure; such a reduction in pressure can occur either each tissue and that in the blood after the blood has equilibrated to the pressure of the gas in the lungs. taken up in the The amount blood is tension falls gradually. As blood flow, the difference amount in absorption, the rate of in partial and the and blood pressures, of inert gas dissolved in the tissues determine the rate of elimination. After decompressing to the surface or ascending to a shallower level, equilibration new level may require 24 hours or more. is assumed that, during decompression, at the It and tissues can to some degree hold gas solution without bubbles being formed. to the blood in supersaturated A supersaturated is become supersaturated when returning from the depth of a dive to the atmo- sphere at sea level or when going from the atmosphere at sea level to the atmosphere decompression sickness from solution in is for short periods of time, a bubbles are the cause of DCS October 1991 — NOAA Diving Manual borne out by the facts DCS (as well DCS symptoms incidents of as during decompressions in occurred), and (2) no other explanation accounts so well for the success of re- compression therapy as a treatment for DCS. These bubbles can cause the symptoms and signs of through various mechanisms: Intracellular bub- bles can disrupt the cells without bubble establishes an outward gradient is which no depth and duration of his or her dive, of that (1) bubbles have been seen and recorded during DCS The ascent The cause the tissues and blood of the body and diver can ascend a certain distance, depending on the formation. at altitude. the release of dissolved gas the consequent formation of bubbles in the body. That one that holds more gas than would be possible at equilibrium at the same temperature and pressure. Because of the ability of the blood and tissue solution 3.2.3.2 and cause loss of function; intravascular bubbles can act as emboli and block 3-17 Section 3 many circulation either to a few or tissues, The most common symptom depending DCS of is which pain, is on where these bubbles lodge; and extravascular bubbles can cause compression and stretching of the blood usually localized at a joint. Pain and nerves. In addition, the blood-bubble interface acts as a foreign surface and activates the early phases of blood coagulation and the release of vasoactive often described as a dull, throbbing pain deep in the joint or tissue. substances from the cells lining the blood vessels. the pain as being related to vessels The causes of DCS include inadequate decompres- decompression table used was sion (either because the inadequate or was not followed properly), individual physiological differences, or environmental factors. Inadequate decompression is an obvious cause of DCS, 70 to DCS 75 percent of The reported to occur in is cases. The pain onset of this pain and, in the early stages, the diver DCS of is usually gradual is may not recognize DCS. However, the pain more intense and, in some cases, it may become severe enough to interfere with the strength of slowly becomes the limb. In divers, the upper limbs are affected about three times as often as the lower limbs. Before decided that the case involves Type DCS I it is only, the symptoms occur even when the decom- diver should be given a careful examination for any obviously inadequate. In addition, decom- as obesity, fatigue, age, poor physical condition, being may be masking symptoms. However, if pain is truly the only symptom, the case falls into the Type I category and should be treated as such. Although pain is reported as a symptom in 30 percent of cases of Type II DCS, this form of DCS includes all cases that have respiratory problems, hypovolemic shock, or more serious symptoms or signs of central or peripheral nervous system involvement. Because of the dehydrated, or having an illness that affects the lung involvement of the nervous system, Type or circulatory efficiency. Environmental factors that be associated with but frequently no pression is may occur even pression sickness tables used are adequate Moreover, it common is if the decompression and are assume strictly observed. to that DCS cannot occur on a 'no-decompression' dive; however, although is uncommon dives, it DCS for to it occur on no-decompression can happen. Differences in individual physi- DCS include factors such ology that may predispose to have been implicated in the DCS development of cold water, heavy work, rough sea conditions, are and the Decompression sickness (colloquially termed 'the may be divided into two general categories, Type I and Type II. Type I DCS includes those cases in which pain, skin itching or marbling, or lymphatic involvement are the only symptoms. The mildest cases bends') DCS are those involving the skin or the lymphatics. Skin bends are characterized by itching of the skin and a burning sensation, which may also be accompanied by the appearance of a mottled rash or marbling of the skin. Lymphatic involvement is usually signaled by many These usually have their after a dive but, as is II DCS may and symptoms. onset during or immediately different signs Type the case with I DCS, may experts also consider the and excessive fatigue that DCS. may common site for Type II DCS common symptoms in spinal cord trauma; these include paralysis, loss of are similar to those seen sensation, muscular weakness, loss of sphincter control, and girdle pain of the trunk. Often the symptoms or signs of either spinal cord DCS or peripheral nerve DCS do not follow a typical nerve distribution, and care must be taken not to dismiss strange neurological complaints or findings as hysterical may toms be unstable in position is uncommon. early stage of spinal or peripheral of anorexia symptoms follow a dive manifes- the spinal cord, and is the most symptoms painless swelling, but such involvement Some serious occur as long as 36 hours after surfacing. The most use of heated suits. of neurological signs, because the pain more is matic nerve different in origin. Symp- and type during the DCS; this shifting in from the usual history of trau- injuries. which are Cerebral decompression sickness can be manifested mild pains that begin to resolve within 10 minutes of form of almost any symptom. Common ones are headaches or visual disturbances, and others include dizziness, tunnel vision, confusion, disorientation, psychotic symptoms, and unconsciousness. The combination of nausea, vomiting, vertigo, and nystagmus is characteristic of labyrinthine DCS, which is known as the 'staggers' because its victims have difficulty tations of Type I onset, are considered mild cases of Type In addition, 'niggles,' symptoms I involvement, or niggles) DCS of Type I DCS. These (skin bends, lymphatic do not require treatment other than breathing pure oxygen at of time, and often even this 1 is ATA for a short period not required. However, any diver with niggles, skin bends, or lymphatic involvement should be watched closely, because these symptoms may presage the onset of more serious problems that will require recompression. ply be assumed that these symptoms to more severe ones. 3-18 It should not sim- in the walking or maintaining their balance. Tinnitus and partial deafness may also occur as part of this complex of symptoms. Pulmonary will not progress It is DCS is commonly known as the 'chokes.' characterized by substernal distress on inhala- NOAA Diving Manual — October 1991 Diving Physiology Figure 3-10 Isobaric Counterdiffusion tion, coughing that can become paroxysmal, and severe respiratory distress that can end in death. This form of DCS has been DCS cases. reported to occur (A) Steady ( about 2 percent of in if ° o Hypovolemic shock may occur as the sole symptom of Type II DCS, but it is more commonly associated with other symptoms. The symptoms of rapid pulse rate, postural hypotension, etc., are no different from those found in hypovolemic shock occurring for other reasons and should be treated in the same manner, that Rehydration should be performed is, by rehydration. orally o o o all the patient conscious is intravenously. Mild hypovolemia or, if may State- o 1 ° o o o °n\° o ^-^ o £Jftt&CQ °y^M \. r o r /•JZWv o o O • o •V Gas 1 Gas 2 o V mpJTSt\\ o o ) I o \ o &&**•* •* ° 0-**° o unconscious, be more com(B) Transient mon in diving than is generally realized because of the '• while dressed in a diving suit, /No \ limited access to fluids, *f symptoms of more complete discussion DCS may be found in Elliott 1 I always be identified and treated, because the treatment of DCS is less effective if the shock condition has A • • pressure or cold diuresis, etc. Hypovolemic shock should not been corrected. • • increased heat load that results from working hard 'W° •y Rx\. * • of the and Kindwall Jfe L-^O/fcr^ • (1982). !• Q¥sV\ • • • • 1 • cs*r°* Source: Bennett and Elliott 1982) with the permission of Bailliere Tmdall, Ltd. ( 3.2.3.3 Counterdiffusion Experiments dating back . 1962 have demonstrated to that the sequential use of different breathing gases in a particular order, determined by their physical properties, could increase dive time at depth without increas- During some of was discovered that a diver breathing one gas mixture while surrounded by ing a diver's decompression obligation. these experiments, however, it another could develop serious gas lesions even when the ambient pressure level was maintained at a constant (D'Aoust and Lambertsen 1982). For example, experimental subjects breathing neon at the skin, where a gradient sloping to the exterior approaches satu- exists; note that the superficial skin ration with gas 1 (°), except for a gradient ies. The process depicted deep counterdiffusion occurs is in Figure 3-1 tissue isobaric gas exchange. suddenly changed to if environment developed skin lesions, severe nausea, vomiting, and vestibular derangement. Because this phenomenon involves the passage of gases at the same ambient pressure through tissue fluids in opposing skin, has been termed isobaric counterdiffusion or isobaric counterexchange. saturation or subsaturation) can occur in the skin or between internal tissues and their capillaries. This can lead not only to serious lesions but also to the formation of gas constant. emboli even when ambient pressures are The process is shown in situation depicted in Figure 3-1 'steady state' and occurs when 0A Figure 3-10. The is referred to as the superficial tissues of the subject approach saturation with gas 2 October 1991 is — NOAA Diving Manual (•) except OB occurs different and gas 2 (•) will be initially in from the 1 c ( ) will through the taken up again via the lungs and through the skin. Unlike the situation in Figure 3-1 0A, this latter process must be considered transient, since gas to a negligible level 1 (°) eventually will be and gas 2 (•) will the subject at a final pressure that Depending on circumstances, counterdiffusion (super- that 1 Deep-tissue isobaric one being breathed. In such a situation, gas be eliminated via the lungs and it gas the gas surrounding a diver one that or nitrogen mixtures while surrounded by a helium directions, in slopes from the exterior to the interior blood capillar- reduced eventually saturate is no greater than ambient (D'Aoust and Lambertsen 1982). Depending on depth and the breathing gases being used, the total gas tensions produced during the transient can reach levels sufficiently high to formation and decompression sickness. cause bubble Work in this complex field is continuing and should lead to the use of improved gas sequences and improvement in the efficiency of deep diving and the development of safer decompression procedures. 3-19 Section 3 3.2.3.4 Aseptic Bone Necrosis (Dysbaric Osteonecrosis) Exposure pressure is to compressed which may have been a factor in the destrucBone lesions may not become apparent on x rays for 4 months to 5 years after the crystals, tion of the joint surface. air at elevated atmospheric sometimes associated with the death of necrosis This condition (1982). is referred to as avascular necrosis of bone, caisson disease of bone, or aseptic or dysbaric bone necrosis. These changes are not of infectious ori- A initiating insult. portions of the long bones of the exposed individual. A detailed review of aseptic bone may be found McCallum and Harrison in 3-year survey of 350 full-time divers in the British Navy showed bone had shown no a 5-percent incidence of aseptic and they have been seen in patients suffering from many conditions, such as chronic alcoholism, pancreatitis, and sickle-cell anemia, in patients using sys- evidence of having experienced decompression sick- temic steroids, and survey of 934 U.S. gin, in caisson (compressed air tunnel) workers and divers. The development of changes in the accompabreakdown, necrosis; half of the affected divers ness (Workman, personal communication). Navy divers, aseptic bone necrosis were found by standard radio- hip and shoulder joints of caisson workers, graphic techniques; another nied by crippling effects caused by joint as doubtful (Hunter et was first noted in 1888, but the disease has not been who In a recent 16 positive cases of 1.71 al. 1 1 cases were interpreted 1978). The data revealed a percent incidence overall and a 6.7 percent inci- more conservative decompression procedures than com- dence for divers over the age of 35. Although the relationship between aseptic bone necrosis and decom- pressed air tunnel workers do. pression sickness particularly prevalent in divers, generally observe is not clear, the incidence of oste- of aseptic bone necrosis occur in the onecrosis in the subjects of this study was found to be head of such bones as the femur (long leg bone) or humerus (bone of the upper arm), the weakened underlying bone that supports the cartilage covering the bone will collapse under weight-bearing and activity, causing the joint surface to break down and become irregular. Pain occurs with movement of these joints and is accompanied by muscle spasms around the joint and the inability to use the joint in a normal manner. Since the lesions often are bilateral and symmetrical, both and number of months of diving. Navy, the long-bone radiographs of a group of 177 non-diving enlisted men were compared to the long-bone radiographs of 93 enlisted divers 35 years of age or over (Hunter and Biersner 1982). It was found that diving, as practiced by the U.S. Navy, contributes independently to the development of aseptic bone necrosis and bone If the lesions may collapse, Lesions may also occur femoral heads causing severe disability. in the shafts of the long bones, but these almost never cause bility; symptoms or disa- however, bony scars that indicate increased density may appear on x ray after elbows, wrists, new bone Bone necrosis is deposited during seldom seen in the or ankles of divers or caisson workers the healing process. is (Kindwall 1972). Factors that may be related to the likelihood of developing bone lesions are frequency of exposure to pressure, number of cases of bends, adequacy and promptness of recompression treatment, and the total amount of exposure to pressure. According to McCallum and Harrison (1982), "The whole process from the first radiographic appearance of the lesions to loss of continuity in the joint surface may take only from 3 or 4 months to 2 or 3 years or perhaps longer." The cause of aseptic bone necrosis has still not been demonstrated beyond doubt. There is some evidence that fat emboli may occlude circulation in the blood vessels in bone and other tissues and thus may be a factor in the development of hip lesions in the chronic alcoholic with a fatty liver. In patients with gout, lesions of the hip joints have contained sodium urate 3-20 related both to age In another study conducted by the U.S. cysts, as evidenced among divers in the tested group. This conclusion was qualified by the statement that the results must be viewed with caution 'because of the larger number group than for the diver group, the small of doubtful films found for the nondiver number of and doubtful cases found in either group, the age of the samples used (35 years of age or older), and the substantial degree of unreliability demonstrated in the classification of the films' (Hunter and Biersner 1982). A subsequent study, also by the U.S. Navy, concluded that the prevalence of bone cysts among Navy divers is probably related to one or more of several conditions, including hyperbaric exposure, positive genetic predisposition, and increased exposure to adverse environmental or hazardous conditions (Biersner and Hunter 1983). 3.2.3.5 Inert Gas Narcosis Inert gas narcosis is caused by the raised partial pressure of the inert gas in compressed air (see Section 20.1.6). In diving, the most common type of inert gas narcosis and other is nitrogen narcosis. Although nitrogen inert gases are physiologically inert mal conditions, they are able NOAA to under nor- induce signs and symp- Diving Manual — October 1991 Diving Physiology toms of narcosis or anesthesia at sufficiently raised pressures. Other inert gases, such as those in the noble gas series, range narcotic potency from helium through in neon, nitrogen, argon, and krypton to the surgical anesthetic xenon. Recent analyses have demonstrated that the qualitative behavioral effects are equivalent regardless of the specific al. Neon 1985). gas causing the narcosis (Fowler et has been used satisfactorily for exper- imental diving procedures but Helium is not used in diving widely used The onset of narcosis is rapid. The condition is often when a diver first reaches depth and may there- severe Recovery after stabilize. equally rapid and is accom- is plished by ascending to a shallower depth so that the narcotic effect of the inert gas who remember reduced. Divers is may have experienced narcosis on a dive not events occurring at depth. High alveolar pressures of in their effects N and CO, are additive on performance, but CO, has no signif- diving as a icant effect on nitrogen narcosis (Hesser, Adolfson, substitute for nitrogen and to prevent narcosis (see and Fagraeus 1971). Factors that can increase the such a weak narcotic that susceptibility to narcosis include alcohol or the after- today. is a gas Section 15.1.3). Helium is in helium narcosis has not been demonstrated. that is it caused by the physiochemical interaction of the inert gas with the nerve cell A body. rect is membranes of the theory widely held that has been proved incorthat the signs and symptoms of narcosis are caused by carbon dioxide retention resulting from respiratory embarrassment occasioned by the breathing of dense inert gas mixtures at raised pressures. signs and symptoms of narcosis are noticed first approximately 100 feet (30.5 meters) during com- The at pressed air breathing and are similar to those of alcoholic intoxication or the early stages of hypoxia; there is a wide variation in individual susceptibility. However, depths the majority of compressed air divers at greater show impairment of thought, time perception, judgment, reasoning, memory, ability to perform mental or motor tasks, and increased reaction time (see Table Many measures 3-2). have been used to assess the perform- ance decrement resulting from inert gas narcosis. Cognitive tests are more sensitive measures of narcotic effects than manual dexterity tests (Fowler et al. 1985). Intellectual capacities such as short-term memory are affected to a greater extent than manual dexterity. If become where they are dives air depths to symptoms of nar- et al. 1960). greater 100 than feet (30.5 meters), special precautions should be taken; only experienced, many be used. As fit, and well-trained divers should decisions as possible should be made before the dive, including length of bottom time, duration of ascent, and actions to be taken in an emergency. Experience, frequent exposure to deep diving, and a high degree of training may permit divers to dive as deep as 180-200 feet (54.9-61 meters) on air, but novices or susceptible individuals are advised to remain at shallower depths. At depths greater than 180 feet (54.9 meters), the performance or efficiency of divers breathing compressed air will be impaired. At 300 feet (91.5 meters) or deeper, the signs and narcosis are severe and there is symptoms of the possibility of hallu- cinations, bizarre behavior, or loss of consciousness. Furthermore, because of the associated increased oxygen partial pressure at such depths, may oxygen convulsions occur. oxygen tend may have feel- and well-being (euphoria) and a sense accompanied by of detachment from the environment, dangerous overconfidence, an uncontrollable desire and a tingling gums, and correct For Frankenhaeuser Experimental work has suggested that divers satu- ings of elation lips, pressure increase the signs and cosis (Hesser 1963; rated on compressed air or a mixture of nitrogen and Divers experiencing nitrogen narcosis to laugh, nitrogen partial pressure, increases in the oxygen partial likely tasks well before diving. a motion sickness remedies and sedatives. At a constant narcotic, they should practice anticipated divers expect to dive in situations to and the effects of effects of alcohol, fatigue, anxiety, cold, Although many theories have been developed to explain the mechanism of inert gas narcosis, it is clear legs. and vague numbness of the There may be an and rapid decisions or on a task. Errors may be inability to make to concentrate effectively made in recording or compil- some to adjust to of the narcotic effects of nitrogen, thus permitting deeper air breathing excur- made (Hamilton et al. 1973, Schmidt et al. and Hamilton 1975, Miller 1976). However, divers must have demonstrated their ability sions to be 1974, Langley to adjust to elevated partial pressures of nitrogen before procedures relying on it can be used without taking extra care and providing additional supervision (Bennett 1976, 1982). Various efforts have been made to use ing data or computations. Novices, especially, may- drugs and other methods to reduce the effects of nar- develop terror rather than euphoria. Narcosis cosis. nificant danger to divers because it is a sig- increases the risk of an accident and simultaneously diminishes their ability to cope with an emergency. October 1991 — NOAA Diving Manual In general, 'the weight of evidence favors the conclusion that ethanol (alcohol) exacerbates narcosis and amphetamine ameliorates it. This with the view that narcosis depresses the is consistent CNS (central 3-21 Section 3 Table 3-2 Narcotic Effects of Air Diving Compressed Depth Feet Meters Effect 30-100 9.1-30.5 Mild impairment of performance on unpracticed tasks Mild euphoria 100 Reasoning and immediate memory affected more than motor coordination and 30.5 choice reactions. Delayed response to visual and auditory stimuli 100-165 Laughter and loquacity 30.5-50.3 may be overcome by self control Idea fixation and overconfidence Calculation errors 165 50.3 Sleepiness, hallucinations, impaired judgment 165-230 50.3-70.1 Convivial group atmosphere. May be terror reaction in some Talkative. Dizziness reported occasionally Uncontrolled laughter approaching hysteria 230 70.1 Severe impairment 230-300 70.1-91.5 Gross delay in of intellectual response to some performance. Manual dexterity less affected stimuli. Diminished concentration Mental confusion. Increased auditory 300 in sensitivity, i.e., sounds seem louder Stupefaction. Severe impairment of practical activity and judgment 91.5 Mental abnormalities and memory defects. Deterioration in handwriting, euphoria, hyperexcitability Almost 300 total loss of intellectual and perceptive faculties Hallucinations (similar to those caused by hallucinogenic drugs rather than alcohol) 91.5 Derived from Edmonds, Lowry, and Pennefather (1976) nervous system)' (Fowler et al. 1985). (Readers are referred to Bennett (1982) and Fowler et more complete discussions of 3.2.3.6 al. (1985) for High Pressure Nervous Syndrome (HPNS) At diving depths greater than 600 fsw (183 msw), signs and symptoms of a condition known as the high pressure nervous syndrome (HPNS) appear and become worse the faster the rate of compression used and the acterized in postural humans by compresemploying exponential compression rates, adding other inert gases inert gas narcosis.) greater the depth or pressure attained. rate of compression to depth, using a stage sion with long pauses at selected intervals, HPNS is such as nitrogen to helium/oxygen mixtures, and selecting personnel carefully. At present, the data suggest that adding 10 percent nitrogen to a helium/oxygen mixture, combined with the use of a proper compression rate, ameliorates HPNS many of the serious symptoms of (Bennett 1982). char- dizziness, nausea, vomiting, and intention tremors, fatigue and somnolence, 3.3 OXYGEN POISONING in intel- Prolonged exposure to higher than normal oxygen and psychomotor performance, poor sleep with nightmares, and increased slow wave and decreased fast wave activity of the brain as measured by an manifestations are referred to collectively as oxygen myoclonic jerking, stomach cramps, decrements lectual electroencephalogram (Bennett et First noted in the initially as 1960's, al. was referred to helium tremors. Since that time, numerous studies have been conducted that were designed to determine the causes of of preventing ameliorating 3-22 it HPNS and to develop means (Bennett 1982). Methods of preventing or HPNS poisoning. include using a slow and steady It is now believed most likely that whose oxygen by increased rates of formation of superoxide, peroxide, and other oxidizing free radicals that ultimately cause critical enzyme inactivation, lipid peroxidation, and impairment of cell mempoisoning 1986). HPNS partial pressures causes a variety of toxic effects is initiated brane function, with resultant disruption of intracellular metabolism. These adverse effects of oxidant species are opposed by anti-oxidant protective NOAA Diving Manual mechanisms — October 1991 Diving Physiology the defenses are until overwhelmed by the magnitude continuous oxygen exposure. Other symptoms or signs CNS and duration of oxidant stress. Thus, the onset time, of nature, and severity of overt manifestations of oxygen irregularities in breathing pattern, determined by the inspired oxygen presduration of exposure, as well as by unique and sure characteristics of enzyme function and external mani- spasms, muscular incoordination, fatigue, confusion, and anxiety. Extreme bradycardia to a degree suffi- toxicity are festations of specific disruptions of intracellular Since oxygen toxicity lism. non in all phenome- a generalized that affects all living cells, ultimately expressed tions is metabo- its (Lambertsen 1978). in the ears, diaphragmatic cient to cause cerebral ischemia with transient loss of consciousness sure at 3.0 may occur during prolonged oxygen expo- atmospheres (Pisarello et al. 1987). Oxygen effects on organs other than the lungs and adverse effects are organ systems and func- oxygen poisoning include ringing CNS undoubtedly occur to some degree during expopulmonary sures that produce overt manifestations of Pulmonary oxygen poisoning occur during will prolonged exposure to any oxygen partial pressure above 0.5 atmosphere. At the lower end of ble degrees of pulmonary intoxication would occur this range, detecta- 1983, Lambertsen or neurologic oxygen poisoning (Clark 1978). These effects go unnoticed because they are not associated with chest pain, convulsions, or other obvious indications of oxygen poisoning. Although the nature weeks of saturation exposure (Clark and Lambertsen 1971a). During continuous administration of 100 percent oxygen, pulmonary symp- and degree of such effects are not now known, toms have been observed within 12 to 24 hours at 1.0 atmosphere (Comroe et al. 1945), 8 to 14 hours in many days only after at 1.5 atmosphere (Clark 2.0 atmospheres (Clark 3 to hours 3.0 at onset of et al. 1987), 3 to 6 hours at and Lambertsen 1971b), and atmospheres (Clark symptoms is et al. then more rapidly until each inspiration it to The 1987). usually characterized by mild substernal irritation that intensifies slowly at Coughing 1 first is and painful. also progressively increases in severity until cannot be suppressed after deep inspiration. Short- and hematopoietic tissues. In addition, a regular increase myopia (near-sightedness) has been noted patients who in some receive daily hyperbaric treatments (Lyne Farmer 1978). Individuals exposed oxygen in saturation diving conditions also have been found to experience potent visual effects (Kinney 1985). 1978, Anderson and to elevated partial pressures of In the absence of definitive information regarding the subtle effects of oxygen toxicity, it is important to remain aware that organ systems and functions external to the lungs and CNS may be adversely affected by may either prolonged and continuous or repeated and severe exposures, presumably because of vital capacity, which can occur before symp- ness of breath during exertion, or even at rest, occur likely target sites include the liver, kidney, endocrine organs, intermittent oxygen exposures. poisoning cul- It is likely that such would be most evident either near the end of a continuous oxygen exposure or within several hours after exposure termination. During a series of inter- generalized convulsions followed by un- mittent oxygen exposures, the probability of detection dominant manifestation of oxygen intoxication during exposures to oxygen partial pressures above 2.0 atmospheres. Convulsions may also occur while breathing oxygen at lower partial pres- of subtle adverse effects will increase directly with the in decreased toms are obvious. Central nervous system minating in consciousness is (CNS) oxygen a sures during periods of exertion, particularly when combined with underwater immersion, during periods of carbon dioxide accumulation with concurrent incre- ments in cerebral blood flow and brain oxygen tension, unusually susceptible individuals. Muscular twitching, especially of the face and lips, or hands, and in may precede does occur, the onset of convulsions. it When this sign should serve as a warning to reduce the effects number and duration of exposures. In humans, recovery from oxygen poisoning after oxygen pressure-exposure duration combinations that do not produce overt intoxication appears to be sufficiently complete to allow appropriately spaced, repeated exposures without fear of cumulative or residual effects (Lambertsen 1978). Full recovery reactivation of critical enzymes and alterations in cellular function. tions of When reversal of early overt manifesta- oxygen poisoning are produced, however, recov- inspired oxygen pressure or to terminate the oxygen ery probably requires a exposure immediately, reversal of tissue inflammatory reactions In a if possible. group of 18 normal resting men breathing oxy- gen for up to 3.5 hours at 3.0 atmospheres in a hyperbaric chamber, constriction of peripheral vision always occurred prior to convulsions (Lambertsen et al. 1987). Nausea and dizziness may occur intermittently during October 1991 — NOAA Diving Manual from such conditions probably requires relatively limited and rapid more extensive and lengthy and repair of cellular metabolic or structural defects. Rates of recovery from the symptomatic and functional effects of effects of most oxygen and different toxicity are variable for different individuals. The complete symptoms associated with CNS resolution oxygen poisoning 3-23 Section 3 occurs within minutes after the inspired oxygen pressure is reduced to normal levels. Even after an oxygen convulsion, recovery can occur within 30 minutes, but may require an hour or more some low oxygen pressures. Possible causes of carbon dioxide retention include faulty CO absorpat unusually tion in closed-circuit breathing equipment, inadequate Chest pain and cough associated with oxygen-induced pulmonary ventilation while exercising under conditions of excessive external resistance to breathing, and tracheobronchitis usually resolve within 2 to 4 hours intentional hypoventilation to conserve air. Cerebral it in individuals. after exposure termination, but unusual fatigue mild dyspnea on exertion may and occasionally persist for few weeks after exposure. Although vasodilation, which occurs ide retention, is in response to carbon diox- responsible for the prominent eleva- nary diffusing capacity for carbon monoxide often requires 1 to 2 weeks or more (Clark et al. 1987). Hyperoxic exposures for diving and decompression tion of brain oxygen tension during oxygen breathing and accounts for most, if not all, of the associated decrement in CNS oxygen tolerance. Extending human oxygen tolerance by means of drugs that have been shown to delay one or more manifestations of oxygen toxicity has not to date been shown to be practical. Since such an agent ideally would have to be distributed throughout all body tissues and oppose applications should be planned to remain well within toxic effects on a variety of known oxygen tolerance limits. They should also be appropriately spaced to ensure complete recovery likely that than a limited potential for practical application (Clark between exposures. This approach will both avoid the cumulative, residual effects of oxygen poisoning and useful procedure for extending several days or even a there is a wide range in individual variability, oxygen- induced deficits in vital capacity and forced expiraand inspiratory flow rates typically reverse within 1 to 3 days after exposure, while recovery of pulmo- tory the enzymatic targets, it is not any drug now available will ever have more 1983, Lambertsen 1978). At the present time, the most human oxygen toler- maintain a reserve of oxygen tolerance in case hyperis required for decompression sick- ance employs systematic alternation of hyperoxic and complex tolerable duration of exposure to a selected level of oxygenation therapy ness or gas embolism. If (as might occur in a treatment) oxygen therapy makes a significant degree of it necessary to cause pulmonary intoxication in a normoxic exposure intervals to increase greatly the hyperoxia. This procedure takes practical advantage of the empirical observation that many early, subclini- effects of oxygen toxicity are reversed more rapidly patient, subsequent operational exposures to hyperoxia cal should be delayed for at least several weeks to allow than they develop. Interrupted exposure as a means of complete recovery. oxygen tolerance extension was initially studied in animals (Clark 1983, Lambertsen 1978), and its effectiveness was later demonstrated directly in man (Hendricks A variety of conditions, procedures, and drugs can be used to modify the oxygen tolerance of humans (Clark and Lambertsen 1971a). These factors may et al. affect the time of onset, rate of progression, or severity exposure has been a component of the U.S. of one or more of the diverse manifestations of oxygen poisoning. Of all the factors known to hasten the development of oxygen poisoning, the effects of exercise and 1977). Although periodic interruption of oxygen gen treatment tables its potential for (US Navy 1985) for Navy oxymany years, oxygen tolerance extension has been only minimally exploited to date. carbon dioxide accumulation are most relevant to diving operations. By mechanisms that are not well understood (apart 3.4 EFFECTS OF COLD (HYPOTHERMIA) a condition in which the deep tissue or from the possible influence of concurrent carbon diox- Hypothermia ide retention), physical exertion itself exacerbates the core temperature of the body development of in CNS CNS oxygen poisoning. This reduction oxygen tolerance is expressed both by the earlier onset of convulsions at oxygen pressures above which is is falls below 95 °F (35 °C), the temperature at which malfunctions in normal physiology begin to occur. If the core tempera- ture drops below 96.8 °F (36 °C), diving operations and by the occurrence of convulsions should be terminated because the consequences of con- during exposure to oxygen pressures at which oxygen- tinuing are serious. If the core temperature falls to in induced seizures would otherwise almost never occur normal, resting individuals. The adverse effects of emergency rewarming and medical treatment are exercise on pulmonary or other non-neurologic mani- Between 86° and 89.6 °F (30° and 32 °C), cardiac irregularities commence and unconsciousness 2.0 atmospheres festations of oxygen intoxication have not been de- Elevated arterial carbon dioxide pressure will also 3-24 required. may monstrated. hasten the onset of convulsions or cause 93.2°F (34°C), temporary amnesia may occur and them to occur result. Because water has a specific heat approximately 1000 times greater than that of air and a thermal NOAA Diving Manual — October 1991 Diving Physiology conductivity 24 times greater than that of air, the body loses heat much faster in water than in air of the During swimming, the increase resulting from exercise is energy production in counterbalanced by the increase same temperature. Fortunately, the thermoregulatory system of the body is highly sensitive to stimulation in from the hands and feet, so that the body's heat generating systems are activated before the core temperature is affected seriously. The fact that the hands and the core to the periphery, and this heat feet get cold first is thus, in this sense, an advantage. muscle blood flow resulting in greater heat transfer. Thus swimming promotes faster transfer of heat from the water (Nadel 1984). This immersed in why is in is turn lost to persons suddenly cold water or divers becoming cold are better off remaining than trying to swim. Rapid still and with core temperatures below 96.8° F (36°C), the defense mechanisms of the body are activated. These mechanisms consist of shivering, which can increase basal body heat production by up to five times, and vasoconstriction, which reduces blood flow to the periphery and thus reduces heat loss. Unfortunately, these mechanisms rarely achieve heat heat loss provokes strong shivering, so that the diver balance, so that the diver continues to lose heat. long slow cooling and undetected hypothermia even in body heat by conductive loss from the skin, a significant loss (10 to 20 percent of total body heat loss) occurs by evaporation from the lungs. The percentage is dependent on the humidity of tropical water. This affects With cold skin In addition to losing the inspired since the drier the air the greater the air, evaporative heat Further, as divers go deeper and loss. heat loss increases. becomes more dense, convective Breathing gas heating is needed beyond depths of 400 feet their breathing gas warned. Gradual heat not cause shivering, yet the accumulated cooling and apparently adequate thermal protection in dives, or repeated dives over several days, may produce memory and a diver's effectiveness and possibly endangering him may thermal protection lead to an unwillingness to dive again or to disabling fatigue known Symptoms of and diminished usefulness. On Because of large individual difmust determine the most suitable protection on an individual basis. A uals are poor judges of their ferences in cold tolerance, every diver body heat available, ranging suits and dry from standard suits to specially heated suits (for detailed descriptions of these suits, of protective equipment, however, creates a complication because the body's defense mechanism is modified by the thermal barrier of the clothing. This complication is only just being recognized as impor- and divers should be aware that the faster the rate of heat loss, the smaller the drop in core temperature tant, for a given quantity of heat loss. rate of body heat (3) the body size. loss; (2) fer is the amount of body fat; and Larger, fatter people are less affected by a given cold exposure amount Furthermore, whether strongly influenced by: (l) the is is 1985). is lost, tal in and less affected by a given of heat loss. For example, because heat trans- about 100 to 200 times faster water than in the heat that reaches the skin surface is in air, rapidly trans- own thermal state. As the body approaches hypothermia; recognizing hypothermia in problem the other hand, loss of extremely difficult to recognize. Individ- diving. its early stages at this stage, a diver is a serious Deep hypothermia, meaning temperature of 95 °F (35 °C) or lower, may become is a rec- dangerous; helpless. enough to threaten life, will produce loss of dexterity and sense of touch in the hands, making it difficult for a diver to do useful work or even to control diving equipment such as weight Chilling, even 10.8). or not a person shivers (Webb easy to recognize that hands and feet are cold by protective clothing. The use now states that are Hypothermia body heat and — be associated with being cold to the familiar sensations of discomfort, numbness, pain, Obviously, a diver exposed to cold water or even warm water for long periods must wear see Sections 5.4 the speed of or her. In addition, repeated diving with inadequate moderately foamed neoprene wet prolonged reasoning and other cognitive functions, thus reducing It is is greater, with the likely result of impaired performance. Use of (122 meters). Thermal Protection variety of diving suits may be even the likelihood of hypothermia 3.4.2 3.4.1 is over a long time often will loss belts if not severe and buoyancy compensators. Shivering causes a lack of coordination and may make it difficult diver to hold the mouthpiece in place. By for a the time shivering becomes uncontrollable, oxygen consumption has increased significantly. Before this, however, the dive should have been terminated and rewarming started. The ability to think clearly also may and short-term memory be affected seriously by cold. Figure 3-1 1 shows the effect of cold water on psychomotor performance when a diver is wearing a 1/4-inch (0.63 centimeter) wet suit, with hood, gloves, and ferred to the water. Generally, the thicker the layer of booties. subcutaneous and the execution of a simple assembly task are affected fat, October 1991 the greater the insulation. — NOAA Diving Manual For example, both fine digital manipulation 3-25 Section 3 Figure 3-11 Exposure Duration on Psychomotor Task Performance in Cold Water Effect of ( Or- 20 - o E o .c o >. CO Q- c o li E CD O 40 - I CD Q CD O c E o Proper Decrement Curve CO Type Task Water Temperature 60 50 40 1 3 6 7 1 2 4 6 1 2 2 3 70 60 "[ Fine Digital Manipulation Simple Assembly Gross Body & Power Move. < 80 ,OStang& Wiener (1970) * Bowen (1968) O Weltman & Egstrom Et Al (1970) ' D Weltman & Egstrom Et Al (1971) 30 20 10 50 40 Time(Min) Source: Egstrom (1974) seriously at 50 °F (10°C) and 40 °F tures, respectively, as have shown that also air much as 29 percent when andHayford 1981). When diver • (4.5 °C) temperaFigure 3-11. Studies • consumption can go up by as • shown in • it is essential for the • Wear thermal Note the first Be aware that even when properly dressed, hypothermia may Watch the behavioral develop without shivering buddy diver and take heed of any changes that may indicate existing or protection appropriate for the water signs of cold hands 3.4.3 Survival in and feet and loss If ship Cold Water abandonment is necessary, there are proce- of dexterity and grip strength dures that can significantly increase the chances of Note survival, even in extremely cold water. difficulty in performing routine tasks, con- fusion, or a • any of the above symptoms are approaching hypothermia. to: temperature (see Figure 5-17) • if present diving in cold water (Dunford diving in cold water, Terminate a dive Note tendency to repeat tasks or procedures Records show that ship sinkings, even in the worst cases, usually feelings of being chilled followed by inter- require at least 15 to 30 minutes. This affords valuable mittent shivering, even though routine tasks can time for preparation. The following procedures should still 3-26 be performed be carried out (U.S. Coast Guard 1975): NOAA Diving Manual — October 1991 ( Diving Physiology Locate and don a personal flotation device as quickly tion. as possible. body heat Try to enter the water avoid in a lifeboat or raft to it Several hours the loss of Wear is Even air provides insulation. in the water, the extra layers of clothing will reduce the rate of body heat be required to restore is all the not beneficial, because increases circulation of blood to the skin and speeds wetting insulating clothing and losing body heat. several layers of clothing because the trapped may Drinking alcohol lost. body heat or lethargic should be is diver who helpless, irrational, rewarmed more a hot bath should be used, but ally, A cold surroundings. in so hypothermic that he or she if vigorously. Ide- none is available, loss. a hot water suit, electric blanket, or inhalation rewarming Especially protect the head, neck, groin, and the are suitable methods. sides of the chest, because these are areas of rapid less, heat loss. cal attention If is it necessary to enter the water, do so slowly to minimize the likelihood of increasing breathing swallowing water, shock, and death. If jumping is necessary, pinch the nose and hold the breath. A hypothermic diver who irrational, lethargic, or help- is unconscious needs medi- and immediate and vigorous rewarming, by any of the prescribed techniques (see Section 18.8.3 for further discussion of rewarming). rate, Once in the water, orient yourself with respect to lifeboats, floating objects, etc. WARNING Also button up and Who Have Been turn on signal lights as quickly as possible before Divers manual dexterity sion Dives (or Dives Near the Decompression Limit) Should Not Take Very Hot Baths or Showers Because These May Stimulate Do is lost. not attempt to swim except to a pump out the nearby warmed water between will the body and Unlike hypothermia, hyperthermia rarely is to hold the knees against the chest in a doubled-up fash- arms around the side of the chest. If others are nearby, huddle together and maintain maximum body contact. Keep make EFFECTS OF HEAT (HYPERTHERMIA) 3.5 Keep the head and neck out of the water. The best position to conserve body heat Board a Bubble Formation to the extremities, thus increasing the ion with the life raft tight or floating object as soon as possible. a positive attitude, because a will to live does a difference. by immersion in water. and bathe rewarming dive, a cold diver should be soup or coffee, dry off rewarmed. in a warm place, in warm in 104° F (40°C) water reestablishes nor- water. Studies have mal body temperature 67 percent shown faster than that rewarming 100°F (38°C) air (Strauss and Vaughan 1981). Cold divers should not make a second dive on the same day, because it is difficult to know when body heat has in been restored. However, it is if a second dive is necessary, advisable to overdo the rewarming until sweating occurs, which indicates that body heat has been Exercising to generate internal heat little cannot be transferred to the water. produced or no difference If heavy exercise is performed under such conditions, there can be serious overheating problems (Bove 1984). Hyperthermia is encountered more commonly durwhere a wet one encased diver, especially suit in the hot sun, can overheat. is restored. also helpful to of dizziness, disorientation, rapid pulse, hyperventilation, and potential loss of consciousness. ous result of hyperthermia more seri- An important factor is dehydration, which can develop quickly as a result of excessive sweating and lack of fluid replacement. Because it reduces the volume of blood available for circulation to the skin, dehydration increases the chances of divers becoming hyperthermic. Dehydration also increases the likelihood of decompression sickness as a result of inadequate blood flow to the muscles and and juices are recommended hol make matters worse. Divers should be put in a Diving Manual A heat stroke, which can that increases the risk of hyperthermia change into warm, dry clothing and continue some mild exercise to improve heat production and circula- — NOAA is cause death (see Section 18.1.8). speed up the rewarming process. The diver should then October 1991 is is the water temperature The symptoms of hyperthermia include heat exhaustion (see Section 18.8.1), with accompanying feelings This can be accomplished by having the diver drink hot liquids such as if temperature between the skin and water and heat in ing dive preparation Rewarming At the end of a However, reaches 85 °F (29.4 °C), there for a long time in a 3.4.4 Decompres- move from clothing layers and cause the blood to body core body heat loss. craft, Swimming fellow survivor, or floating object. Chilled on and other for ingestion fluids act as diuretics, tissues. Water because alco- which will only who develop hyperthermia cool place, given fluids, and cooled 3-27 Section 3 While taking medication, therefore, careful consid- with water poured over the skin until the body temperature returns to normal. eration should be given to the following elements before diving: DRUGS AND DIVING 3.6 • Why are the drugs being used, and are there underly- ing medical conditions that The use of prescribed or over-the-counter medications is a complex issue. There are no simple answers to questions about which drugs are best for which conditions in a hyperbaric environment. Indi- while diving use should the associated risks of diving to an unacceptable level? Prescription Drugs re- its Will the side effects of the drug increase the • all Drug-induced physiological and psychological the half-life of the drug, and for what diver not be exposed to a high-pressure environment? macologically active agents are used. 3.6.1 is period of time before or after and the mental and physical requirements of must be taken into account before phar- ditions, be relatively or 1976)? What • vidual variability, existing medical and physical con- diving may absolutely contraindicated for divers (Kindwall A • Will the drug interfere with physical performance? • Will the drug impair exercise tolerance? • Does the drug produce rebound phenomena? conscientious diver will discuss these questions with sponses often are altered in a hyperbaric environment. his/her physician before diving while taking prescribed The normal metabolic and excretion patterns of drugs taken at one atmosphere may be significantly and pathologically altered once the diver becomes pressur- or over-the-counter medications. An ized. understanding of the types of changes that occur, the implications of these changes, and the relationships between and among drugs, the environment, and the diver are critical to if therapeutic accidents are The manner olized, in which the drug is absorbed, metaband excreted by the body in a hyperbaric environment; • The physical impact of the type of breathing gas, increased density of the gases, water temperature, and other environmental diver exertion all factors, It obvious that cognitive and motor performance is can be impaired by the abuse of psychoactive agents. Alcohol and marijuana (and other cannabis products) and the degree of contribute to the total effect of a drowsiness from antihistamines, may be tolerated on the surface. Acceptable side effects, like In the hyperbaric environment, however, such side effects may become unacceptable, leading in cates that their use some cases to serious morbidity or even death. Impairment of cognitive function, neuromuscular strength and coordination, or integration of thought and action can have catastrophic results while diving. In addition to the antihistamines, drugs may central nervous system is addictive and in some cases potentiate other central nervous system depressants. For example, in addition to being a depressant and having other subjective effects, alcohol can cause reduced blood glucose levels, which can lead in turn to weakness and confusion. Alcohol also causes blood vessel dilation, which can interfere with proper maintenance of body temperature while diving (see Section 3.4). Because of its diuretic action, alcohol can contribute body dehydration, especially in the where divers may combine alcohol with the significantly to consumption of caffeine-containing drinks such as coffee, and There are reports that the use of marijuana preceding cold water dives can reduce a diver's cold tolerance commonly adversely affect diver safety and per- and breath-holding capability, cause general discomfort, unexplainable apprehension, and a desire to ter- formance include: motion sickness remedies, amphet- minate a dive prematurely (Tzimoulis 1982). tant to note that the effects of and decongestants, some of which have been found last for to induce impaired coordination, cardiovascular effects, up Cocaine to is It is nervous system stimulant. noteworthy that the effects of some of these drugs may belies the hazard to have worn off on the surface, only to return the diver 3-28 becomes pressurized (Anonymous 1986). It is impor- smoking marijuana can 24 hours (Anonymous 1986). commonly abused central Its relatively short action currently the most addiction, and inflammation of the lower airways. when tea, colas. amines, tranquilizers, sedatives, hypertensive drugs, appear (e.g., with concurrent administration of barbiturates) can tropics, used that commonly abused depressants in the world today. Research clearly indi- medication; • Drugs Illicit are the most be avoided. Specific concerns include the following: • 3.6.2 it poses to the diver. The hyper- metabolic state that occurs during the use of cocaine (it is rarely used alone NOAA and is often used with alcohol or Diving Manual — October 1991 Diving Physiology marijuana) may place the diver at risk of subsequent discouraged from using medications before diving. The sharing of medications among and the inability to respond promptly to life-threatening emergencies. It also increases the likelihood of an oxygen seizure and can disturb the normal rhythm of the heart (Anon- drug ymous Conservative and safe practices are required for the fatigue, mental depression, acidosis, 1986). Divers and their physicians have an obligation to communicate with one another. The clinician has the responsibility to explain the nature of his or her treat- ment to the diver, and the diver has the responsibility discouraged. A diving exposure divers also should be is nity for either a clinician or a diver to will not a good opportu- determine whether a be safe and efficacious for a given individual. well-being and survival of the diver. Abstinence from diving may be the most conservative approach for an individual requiring systemic medication (Walsh and Ginzburg 1984). (For a comprehensive review of the of indicating to the treating clinician that a diving effects of drugs in a hyperbaric environment, the reader exposure referred to is anticipated. In general, divers should be October 1991 — NOAA Diving Manual is Walsh 1980.) 3-29 t < Page SECTION 4 COMPRESSED AIR AND SUPPORT 4.0 General 4-1 4.1 Compressed Air 4-1 4.1.1 4.2 EQUIPMENT 4.3 General Safety Precautions for Compressed Air Air Compressors and Filtering Systems 4-1 4-2 4.2.1 Maintenance 4-5 4.2.2 Lubricants 4-5 Compressed Gas Cylinders 4.3.1 Cylinder Markings 4-5 4-5 4.3.2 Cylinder Inspection and Maintenance 4-7 4.3.3 Cylinder Valve and Manifold Assembly 4-10 4.3.4 Low-Pressure Air Warning/Reserve Air Mechanism 4-1 4.3.5 Submersible Cylinder Pressure Gauge 4-1 c « < COMPRESSED AIR AND SUPPORT EQUIPMENT 4.0 GENERAL This section describes the composition and characterof compressed istics air, the most commonly used Table 4-1 Composition of Air in its Natural State breathPercent and the precautions that must be taken when compressed air is used as a breathing ing mixture for diving, medium used for divers. air diving, in and ders, It also discusses the COMPRESSED 4.1 by volume equipment including compressors and cylin- maintenance and inspection. its Gas Nitrogen 78.084 Oxygen Argon Carbon dioxide 20.946 .934 .033 .033 Rare gases AIR Compressed air is the most frequently used diver's breathing medium. In its natural state at sea level Source: NOAA (1979) pressure, compressed air consists of nitrogen, oxygen, argon, carbon dioxide, and trace amounts of other shows the natural composition of gases. Table 4-1 All ambient air air. coolers, does not meet the standards of purity necessary for use as a diver's breathing medium. For example, urban areas the carbon monoxide concen- in tration in the air may be high, and in some cases it may reach a concentration of 50-100 parts per million (ppm). Ambient air may also contain dust, sulfur, oxides, cooling water circulation, or, in the case of air radiator and sources and automotive exhausts and must be avoided breathing air supplied to a diver. in the Scuba cylinders should air source when an is in effect. The Environmental Protection Agency (EPA) monitors ozone and other oxidants EPA is in flow caused by trash, dirt, Potential contaminants include engine or venti- nants. lation exhaust; fuel, or paint; No fumes or vapors from stored chemicals, and excess moisture. compressor should be allowed to operate with its intake or first-stage suction blocked, because this will produce a vacuum within the cylinders that can rap- not be filled from an ambient air pollution alert loss of cooling air The free air intake of the compressor must be located to draw air from an area where there are no contami- other impurities. These contaminants derive from industrial by or lint getting into the radiator fins. metropolitan areas, and the local idly draw lubricating oil or oil vapor from the compressor crankcase into the air system. Some effective methods of preventing the intake of contaminated air are discussed below. office should be consulted before a diving operation undertaken in pollutant levels. an area suspected of having high potential hazard presented by The breathing air obtained from ambient sources is 4.1.1 General Safety Precautions for Compressed under- Air in There are three primary safety concerns associated the United States were unable to achieve compliance with with the use of compressed air or any compressed gas. Federal limits for carbon monoxide by the end of 1987. These lined by the fact that at least In addition to airborne 70 metropolitan areas pollutants, the air compressor • machinery and storage system themselves may introduce contaminants, including lubricating oil and its medium. Additionally, the temperature of the gas being compressed can be high • enough each successive stage to cause pyrolytic decomposition of any hydrocarbon compounds pres- ent. This That the gas be sufficiently pure and appropriate for • vapor, into the breathing are: its intended use; That compressed gas cylinders or storage cylinders be properly labeled and handled; That cylinders be protected from fire and other at is particularly true if hazards. Compressed the compressor's interstage air is available from produced many sources. Most and coolers are not functioning properly. Intercooler mal- of it, function can be caused by excessive condensate, impaired is therefore not of the purity necessary for use as a October 1991 — NOAA Diving Manual however, is for industrial purposes 4-1 Section 4 medium. When compressed essential that the any attempt is made to repair the leak. Leaks can sometimes be detected by painting a 20 percent deter- gas be certified by the manufacturer to be of high gent soap solution (called a snoop) over the external and suitable for breathing. Compressed air suspected of being contaminated should not be used for diving until tested and found obvious because they will cause a froth of bubbles to diver's breathing purchased from a manufacturer, is it air is purity, free of oil contaminants, parts of the valve with a brush. Proper identification and careful handling of com- Compressed pressed gas cylinders are essential to safety. leaks will be form. After the leak has been repaired, the soap solution used for leak detection safe. Even small must be removed completely with fresh water and the valve dried carefully before reassembly. gas cylinders used to transport gas under pressure are Scuba cylinders generally are not color-coded or Department of Transportation (DOT) regulations. These regulations include design, material, inspection, and marking requirements (see Section 4.3). Compressed gas cylinders can be extremely hazardous if mishandled and should be stored securely in a rack, labeled as to type of gas contained; however, large gas subject to preferably in the upright position. When in transit, cylinders allowing it to roll may be color-coded and labeled. The label should be used to identify the contents of a gas cylinder, because color-coding is not standardized. WARNING should be secured against Standing an unsecured cylinder on end or rolling. cylinders unsecured could result in the explo- sive rupture of the cylinder. Cylinders can become deadly projectiles capable of penetrating a wall, and Because Colors Vary Among Manufacturers, the Content of Large Cylinders Should Always Identified By Label— Do Not Rely on Cylinder Color Be they can propel themselves at great speeds over long distances. Scuba cylinders are often fitted with a plastic boot that has holes in it to rubber or permit draining. Several special safety precautions to be observed when using compressed gas are noted on the label of These boots fit over the base of the cylinder and help to keep the cylinder in an upright position. However, cylinders equipped with such boots should not be left unsecured in an upright position, because the boot gas cylinders. In general, these precautions concern alone does not provide sufficient protection against fore not be used or stored in an area falling. hot work, or flammable gases are present. NOTE 4.2 Cylinder boots should be removed periodically and the cylinder checked for evidence Air compressors are the most the flammability of the gas and combustion. Although not ing Compressed gas cylinders are protected against excesby a rupture disk on the valve. Because sive overpressure regulators or gauges opened to may fail when a cylinder valve check the cylinder pressure, it is is important to stand to the side rather than in the line of discharge to avoid the blast effect in case of failure. the Line of Discharge Opening a High-Pressure Cylinder in If a cylinder valve seal leak, 4-2 it is flammable, com- where open flames, COMPRESSORS AND FILTERING SYSTEMS AIR is air. common The compressor used source of diver's for umbilical div- generally backed up by a bank of high-pressure gas storage cylinders to reduce the possibility of interrupting the diver's breathing gas supply because of loss of power or compressor malfunction. There are two main types of compressors: highpressure, low-volume, for use in filling scuba cylin- and low-pressure, high-volume, used for umbiliA compressor is rated at the pressure at which it will unload or at which the unloading switches will activate. A compressor must have the output volume to provide sufficient breathing medium and to provide pressure above the range equivalent to the ambient pressure the diver will experience at depth. When evaluating compressor capacity, the different overbottom pressure and volume requirements of different types of underwater breathing apparatus and/or ders; cal diving. WARNING Do Not Stand ability to support pressed air does support combustion and should there- breathing of corrosion. its in itself When suspected of having a thread or should be completely discharged before NOAA Diving Manual — October 1991 Compressed Air and Support Equipment helmets must be taken into consideration, as well as umbilical length and diameter. Any air compressor used for a diver's surface-supplied system must have an accumulator (volume cylinder) as an integral part of the system. The accumulator will provide a limited emergency supply of air pressor As if the com- fails. number the of scientific, educational, and sport divers increases, there is a concomitant rise in the num- ber and variety of air compressors being used to supply breathing air. Operators should become thoroughly familiar with the requirements associated with the production of breathing air. To ensure proper mainte- nance and care, organizations using compressors should assign the responsibility for the operation of compres- Air compressors are generally rated by two paramethe maximum ient access to a pressure (measured in pounds per when there is conven- high-pressure compressor for recharging. Using cylinders as the gas source reduces the chance of volume of compressed and stored before the dive. Most lockout submersibles carry the diver's losing the primary supply, since the entire gas needed for a dive gas supply in is high-pressure cylinders incorporated into Compressed gas cylinders are also generally mounted on the exteriors of underwater habitats, submersibles, and diving bells to provide a backup gas the system. supply case of emergency, and divers using the habitat in as a base can refill their mounted scuba cylinders from these cylinders. Many types of compressors are available: centrifu- gal, rotary screw, axial flow, sors to a specific individual. ters: Large, high-pressure cylinders are advantageous to use as a source of breathing gas most commonly used type and reciprocating. The in the diving industry is the reciprocating, or piston-in-cylinder, type. These square inch gauge, or psig) they can deliver and the compressors are further classified as "oil-lubricated" output volume (measured jn standard cubic feet per or "non-oil-lubricated," depending on whether or not minute, or scfm) that can be delivered at that pressure. they require lubrication of their compression cylinders. To be volume and pressure or exceed the requirements of the effective, both the output must be equal to system they supply. Air compressors breathing air may In an oil-lubricated compressor, the oil in the crank- case assembly also lubricates the pistons and cylinder walls. commonly used be classified in to provide divers' the following groups: As a result, some of the oil may come contact with the air being compressed. used in machines that provide breathing into direct The air lubricants must be of the quality specified for breathing air and be so desig- • High-Volume, Low-Pressure Air Compressors. These compressors are most often used to support should not be substituted for another unless the manu- surface-supplied operations or to supply hyperbaric facturer's directions so specify. Chlorinated lubricants, chambers. They are generally found where large-scale diving operations are being conducted or aboard surface platforms fitted out for diving. Units commonly used have output volumes of between 50 and 200 scfm at maximum discharge pressures of between 150 and 300 psig. These units may be either permanently installed or portable. synthetics, or phosphate esters (either pure or in a Portable units are generally built into a skid assem- facturers describe their machines as oil-free, even bly along with a power source line engine, or electric filter air, at sites (diesel engine, gaso- motor), volume cylinder, assembly, distribution manifold for divers' and a rack for storing divers' umbilical as- semblies. One lubricant mixture) should never be used. Oil-free compressors usually employ a standard oil-lubricated crankcase assembly similar to that of oil-lubricated however, the pumping chambers in oil-free machines; machines are designed to run either with water lubrication or with no lubrication at all. For this reason, some manu- though the breakdown of such compressors could still result in oily breathing air. The mechanical connections between the pumping chambers and the crank- case on oil-free machines are carefully designed to oil into the pumpThe all-purpose crankcase lubricant prevent the migration of crankcase • Low-Volume, High-Pressure Air Compressors. These compressors are used for filling scuba cylinders and high-pressure air storage systems that provide support for surface-supplied diving and hyperbaric chambers. Portable units used for filling scuba cylinders are commonly available with a volumetric capacity of 2 to 5 scfm at a discharge pressure adequate to fully charge the cylinders (2250 or 3000 psig, depending on the type of cylinder). October 1991 nated by the equipment manufacturer. ing chambers. recommended by the manufacturer can usually be used for oil-free compressors. The compressors used but these machines are still not widely used in opera- tional diving. The production of compressed air is a complex procThe process begins as the piston in the first/second stage head strokes upward in its cylinder. At that ess. point, the intake valve to the first stage closes — NOAA Diving Manual to pro- vide breathing air in hospitals are of the oil-free type, and the 4-3 Section 4 intake valve to the second stage opens. maximum stage opens and compressed air first-stage At the is admitted condense and collect as the air passes air/liquid separator at the discharge The separator cooler. first to the Intercoolers cool the air before intercooler. further recompression and cause water and to point of compression, the exit valve from the oil vapors through the end of the inter- fitted with a drain valve that is them to inert and virtually unchanged physically during the adhere to its purification process. surface, the sieve itself remains With appropriate periodic re- generation processes, most molecular sieves are capa- removing a wide range of contaminants, includ- ble of ing nitrogen dioxide and most odors. However, the remove hydrocarbons and odors with the use of activated carbon, which acts most effective way still is much to must be opened periodically to drain off accumulated liquids. Each intercooler assembly is also fitted with a relief valve that opens if the pressure rises above a safe Another popular filtration system involves the following components, which are used in the sequence level. shown: The second stage downstroke of the which the secondvalve closes and the air is further com- stage inlet At pressed. of compression takes place on the exit valve to the of maximum coalescing section to remove • dessicant section to remove water vapor, nitrogen second stage opens and compressed activated charcoal section for removal of resid- taken and from ambient pressure to approximately 2250 psi. Commay tastes; The Hopcalite® bon dioxide. Hopcalite® Each succeeding cylinder tion is proportionately smaller in is lost because of the volume of the and residual cylinder volumes; this factor and process. the catalytic action intercoolers insignificant. Air leaving a compressor must be cooled and passed through an air/liquid separator to remove any condensed water and oil vapors before storage or immedi- from an oil-free compressor does not genany further treatment unless the applica- erally require tion requires that it be further dried or there is concern about possible contamination of the intake air. Air from an oil-lubricated compressor must be carefully filtered to remove any possible mist, oil vapors, oil from oil oxidation in the compressor (predominantly carbon monoxide), or odors. Sevpossible byproducts eral types of filtration most filtration them in this, is so small as to be physiologically The amount of oxygen used up is approxi- mately 0.5 part of oxygen per million parts of carbon called volumetric efficiency. ate use. Air to car- a true catalyst in this reac- is is neither consumed nor exhausted in the The amount of carbon dioxide produced by mately 10 percent) is monoxide oxidizes the carbon vary with different makes and models of compressors. volume than the previous one. Some efficiency (approxi- and Hopcalite® section for carbon monoxide removal. • pressors typically use a ratio of 6:1, although this re- air ual odors is mist; movable by adsorption; admitted to the second-stage intercooler. In a typical three-stage compressor, the air oil and other contaminants dioxide, hydrocarbons, compression, the • is molecular sieve. • piston, during moment the like a systems are available. To use agents properly, it is necessary to place the filtration system in a specific order. To do the direction of the air flow through the filter monoxide, which has no appreciable effect on the air produced. The lifetime of this system is usually determined by the lifetime of the dessicant, since Hopcalite® is quickly "poisoned" and rendered ineffective An by excessive water vapor. that is not widely understood is aspect of this process that the carbon monoxide oxidation process releases substantial quantities of heat. Hopcalite® If a becomes extremely hot or shows filter signs of discoloration, the compressor output air should be checked for elevated carbon monoxide levels. In addition to Hopcalite®, the use of activated alu- mina No in combination with Multi-sorb® matter what technique is is also widespread. employed, the location of the compressor intake with respect to possible sources of contamination is an important factor in ensuring it satisfactory air quality. Compressors should not be should be checked. Like other high-pressure compo- operated near the exhausts of internal combustion system must be known, and, if there is any doubt, nents, filter canisters should be inspected visually for engines, sewer manholes, sandblasting or painting opera- damage (High 1987). An can be helpful when performing inspection protocol tions, electric arcs, or filter canister tainers of volatile liquids corrosion in- For purposes of dehydration and adsorption, sub- known molecular sieve as molecular sieves are often used. is 4-4 it A a material having an extremely large surface area to enhance Since can give off fumes even when they are tightly closed. Intakes must be provided with spections. stances sources of smoke. Plastic con- its capacity for adsorption. removes harmful contaminants by causing filters for removing dust and other orientation to wind direction up air The is particles. Proper also critical in setting compressor systems. final step in the filling station, production of pure air is the usually located in a dive shop, on board NOAA Diving Manual — October 1991 Compressed Air and Support Equipment ship, or near a diving installation. It is important for the diver to inspect the filling station to ensure that proper safety precautions are being observed and that Federal, state, and local regulations are being followed. Figure 4-1 a schematic of the processing of air from is the intake to the scuba cylinder. (Note that the system depicted Figure 4-1 includes a high-pressure booster in pump, which can increase the efficiency of cylinder filling operations by providing air at the filling station at a pressure above that of the air storage cylinder.) For some diving operations, manufacturer in air is supplied by the banks of high-pressure cylinders. These some This of this oil mixes with the air being compressed. by the compressor's filtering system. Because an improperly functioning filter can oil temperatures sufficiently to decompose or ignite raise the filtered out is oil, it is important to select oil to be used as a lubricant carefully. The oil's flashpoint (the temperature of the liquid oil which sufficient vapors are given off to produce a flash when a flame is applied) and auto-ignition point (the temperature at which the oil, when mixed with air, at burn without an ignition source) are both impor- will tant considerations. The most desirable compressor cylinder banks are fitted with valves and manifolds lubricants have higher-than-average flashpoints and and may be used low provide breathing air in surface- to supplied diving operations and for filling The volatility. recommended by oils most efficient lubricants 4.2.1 for this and equipment. Maintenance Both the compressor and filter system must be maintained properly. When running, the compressor must be cooled adequately, because the primary factor causing the breakdown of lubricants and contamination of the compressed air is high temperature in the may be cooled by blowers or water spray systems or by cooling sys- compressor cylinder. Cylinder heads air the manufac- turer of the compressor are generally the safest scuba cylinders. tems integral to the compressor machinery. head temperature controller is valuable in A cylinder eliminating the possibility of excessive cylinder temperatures. Partic- 4.3 COMPRESSED GAS CYLINDERS The scuba cylinder or cylinders are secured to the back by an adjustable harness or form-fitting backpack assembly equipped with a clamping mechanism. Regardless of which model is employed, all straps diver's securing the apparatus should be equipped with corrosion-resistant, quick-release buckles to permit rapid opening under emergency conditions. Scuba cylinders contain the compressed breathing gas (usually air) to be used by a diver. Most cylinders ular attention should be paid to draining the interstage for diving are of steel or and final-stage separators. Compressors and specially designed filters aluminum alloy construction, and manufactured to contain com- are usually given routine maintenance on an hours-of- pressed air safely at service pressures from 2250 to operation basis. Filters should be examined and replaced 3000 psig (158 accordance with the manufacturer's specifications. The compressor lubricant and mechanical parts should be replaced on a rigorous schedule, based on the manu- to 21 1 kg/cm 2 ) or greater. in facturer's analysis. recommendations or the results of an air Analysis of the output air from oil-lubricated compressor systems should be performed on a periodic basis. Oil mist analyses are difficult to perform and 4.3.1 Cylinder Markings Regardless of cylinder type, data describing the cylinder must be clearly stamped into the shoulder of the cylinder, which must be manufactured require careful collection techniques as well as quali- state Commerce Commission (ICC) fied laboratory analysis of the samples. However, carthe most important, can after by the bon monoxide analyses, by far easily be performed in the field using colorimetric inders as tubes. (See Section 15.4 for information on contami- nant analysis.) A log should be kept for should record all time each compressor. The log in service, maintenance, and air analysis information. CTC/DOT, on the interior of the cylinder's walls, and October 1991 — NOAA recently reflected on cylwhich indicates equivalency with DOT (or ICC). 3AA pressure of 2250 psig cylinders carry the code kg/cm 2 ) and a service or higher on the first line. These marks are followed by the serial number, cylinder manufactur- Oil-lubricated compressors always have a small oil 1970), there- (High 1986a). Regulatory changes in the more than 35 years since scuba cylinders entered service in the United States have produced a variety of code markings. Typically, (158 amount of (until requirements of the Canadian Transport Commission steel Lubricants accordance DOT, and most (steel type), 4.2.2 in with the precise specifications provided by the Inter- Diving Manual symbol (before 1982, the symbol of the user or equipment distributor), the original hydrostatic test er's 4-5 Section 4 Figure 4-1 Production of Diver's Breathing Air < Priority Back Pressure Valve Pressure Gauge %-M Auto Air Distribution Panel Isolation Relief Valve Valve % Magnetic Starter High Pressure Air Booster Check Valve Final Moisture Separator & Hour Meter a Pressure Switch FT-i i . . ! i Bleed Valve i : Chemical Filters X !_ Check Valve Auto Air — Moisture Separator Fill Panel fS>-Auto Condensate Dump * ' i i i i Low Oil "Compressor i_ Level Switch Fill » Hoses High Pressure Lines Electrical Lines Air Storage Cylinders Courtesy Skin Diver Magazine date with testor's symbol, and a plus indicates that a 10 percent is fill ( + ) mark, which over-service-pressure allowed for the 5-year period of the original hydro- indicated in Additional hydrostatic test dates, with the testors' some code markings ( + ) to 3000 psi cylinders. Currently, 5-year or shorter intervals. However, since hydrostatic and scuba cylinders appropri- ately to permit inclusion of the plus mark ( + ) for few steel cylinders are filled in excess of the designated service pressure after the initial period. (Figure 4-2 shows steel scuba cylinder markings.) Current practice allows a cylinder submitted for the plus ( + ), that is the 10 percent overfill, to fail the elastic expansion test and to be reevaluated at the lower service pressure on the basis of the permanent expansion test (High 1986b). Aluminum alloy scuba cylinders entered U.S. commercial service in 1971 and are code-marked in a somewhat different manner than steel cylinders. Initially, DOT issued special permits or exemptions for continued 10 percent 4-6 overfill, as (174 to 211 or overfill allowance codes, will be added on successful retest at required test facilities rarely retest cylinders. These are SP6498 or E6498, followed by the service pressure, which typically ranges from 2475 static test. aluminum the manufacture of CTC that the cylinder in 2 ). No plus used with aluminum alloy aluminum cylinders reflect DOT new material designation (3AL), and a mark indicating volume and equivalency, a the service pressure, shown is kg/cm is intended for scuba service (S80), as Figure 4-3. NOTE Aluminum filled in alloy cylinders should never be excess of marked service pressure, steel cylinders without a plus ( + ) after the current hydrostatic test date should also not be filled over their marked service pres- and sures. NOAA Diving Manual — October 1991 i Compressed Air and Support Equipment Figure 4-2 Steel Cylinder Markings Steel Alloy Specification Manufacturer Initial Test Hydrostatic £ 073440 Company PST (DACOR) Distributor 4-83 + Number Serial NOTE There are four major manufacturers of scuba cylinders in (he United States names and symbols are shown below Their Manufacturer's Symbol Manufacturer Name Inspector's Official Mark A Luxfer Pressed Steel or Authorized Testing G PST (k) Walter Kidde WK WK&Co of Norns Industriesof Inspection Service Cochrane Laboratory T. H. & ® Arrowhead Industrial Service or Hunt Inspection C T H Cochrane Laboratory Derived from The volume of internal physical dimensions and a cylinder may inches or cubic feet. Of more the cylinder, which is a function of is be expressed interest in the capacity of is the quantity of gas at surface The capacity usually standard cubic feet or standard liters is expressed : , or 153 atm) and contain 64.7 standard cubic feet (1848 standard liters) of gas. Cylinders with capacities from 26 standard cubic feet (742 standard liters) (2857 standard liters) October 1991 — NOAA to over 100 standard cubic feet are used for scuba diving. Diving Manual Do Not Fill Cylinders Beyond Their Service Pressure in of gas. Cylinders scuba cylinders generally have a rated working pres- kg/cm WARNING its of various capacities are commercially available. Steel sure of 2250 psig (158 (1979) cubic pressure that can be compressed into the cylinder at rated pressure. its NOAA 4.3.2 The Cylinder Inspection and Maintenance exteriors of most steel cylinders are protected against corrosion by galvanized metal (zinc), epoxy The zinc bonds to the from air and water. Galvanized exteriors are recommended for protection against corrosion; however, epoxy paint or plastic is unsatispaint, or vinyl-plastic coating. cylinder and protects it factory for use over bare steel cylinders, because even 4-7 Section 4 Figure 4-3 Aluminum Cylinder Markings Aluminum Alloy Specification Service Pressure Scuba Service Agency Responsible for Standard 3000 S8oAr(OmittedA CTC/DOT 3AL / (DOT) Serial Number \ SP6498 E6498 , \ ) Cylinder \ Hydrostatic First ^prest 2 A85 "*\Test 2/^v85 P71841^Luxfer Volume and Company ark (A5081)<^ (Distributor) Test Initial Manufacturer- NOTE There are four major manufacturers of scuba cylinders Their names and symbols are shown below Manufacturer's Symbol Manufacturer Luxfer Pressed Steel PST G WK WK&Co. or Norns Industries or <8> Name & Mark, With Manufacturer's Mark Separating of Inspection Service Mark Official A (k) the United States Inspector's o Walter Kidde in Showing Testor's Test Month and Year. Authorized Testing T. H. Cochrane Laboratory Arrowhead £> Industrial Service or Hunt Inspection C T. H. Cochrane Laboratory Courtesy William minor abrasions may penetrate these two coatings and expose the underlying metal, allowing oxidation (rusting) to begin immediately. Epoxy paint or plastic able, however, over zinc-galvanized surfaces it accept- is because reduces electrolytic corrosion of the zinc by salt L. High or assessed. Also, the lining tended to loosen and, in some cases, the resulting flakes clogged the valve or the regulator. A ally Damaged linings must be removed. corrosion-inhibiting epoxy-polyester finish usuis aluminum applied to the exterior of cylinders water and imparts an attractive appearance. With proper both to protect them and to give them an attractive preventive maintenance, electrolytic corrosion color. If this coating scrapes off, tively insignificant is rela- on bare zinc coating. Since internal rusting is a problem, manufacturers formerly applied protective linings on the interiors of cylinders. The use an oxide layer forms that tends to protect the cylinder of internal coatings has only been sion. Often the interiors of from further corrocylinders have a aluminum protective layer over the base metal, such as Alrock® or Irridite®, which is applied during the fabrication process. lining allows moisture in the cylinder to penetrate to Air cylinders and high-pressure manifolds should be rinsed thoroughly with fresh water after each use to bare metal. Corrosion under the lining cannot be seen remove traces of relatively successful, 4-8 because even a small flaw in the salt NOAA and other deposits. The exterior Diving Manual — October 1991 Compressed and Support Equipment Air The of the cylinder should be visually inspected for abra- and corrosion. sion, dents, abrasions or dents, If the cylinder has deep should be tested hydrostatically it before refilling; external corrosion should be removed a protective coating applied to prevent further and Care deterioration of the cylinder wall. When a cylinder is may pared to standards is (1) cuts, gouges, corrosion (general, pitting, line), completely drained and stress lines; (2) dents or bulges; damage; (3) signs of heat if depressed, allowing the second- (4) general abuse; stage valve to open. Cylinders used under water as a (5) condition of plating; source of air for power tools or for (6) current hydrostatic test date. bags often become contaminated by moisture returning through the valve. Cylinders should be stored with about 100 psi of air remaining in lift Interior cylinder evaluations to standards should assess: assembly is (2) (3) thread integrity; attached, because small amounts of water may be trapped in the valve orifice and injected into the cylinder. Moisture in a cylinder often can be detected by (1) the presence of a whitish mist when the valve is opened; (2) the sound of sloshing water when the cylinder is tipped back and forth; or (3) a damp Water in in if the first steel stage or in the hose prior to the second- sion, and the water jacket method. The most common is the water jacket method, which involves method filling and aluminum cylinders should be inspected frequently, they are used filled the cylinder with water, placing cylinder with a hydraulic amount and perhaps as often as every displacement. The pressure in 3 months, a tropical climate or aboard ship, or A special rod- regulations, a more of the is is total expansion indicates that the cylinder unsafe for use and should be condemned. short periods of time. High (1987). to store cylinders over longer periods with to forms of inspection are used, depending on the interval since the previous inspection or the nature of An the suspected problem. informal inspection is a cursory look at a scuba cylinder's exterior and interior to determine A formal inspection in which if there is standards, a dence of the inspection form of a sticker that ity for continued use. a reason to is a it further. complete evaluation against judgment is examine is reached and evi- affixed to the cylinder in the ensure that the valve There is is low pressure not inadvertently opened. a potential for moist ambient air to pass through the open valve into the cylinder as air temperatures change. If there is moisture in the cylinder, air at the higher pressure (higher partial pressure of oxygen) accelerates corrosion. However, a greater danger aluminum exists when partially filled cylinders are exposed to heat, as might occur The metal can attests to the cylinder's suitabil- during a building The temperature-raised pressure reaches that necessary to sticker should indicate the fire. An soften before the standard used, the date of inspection, and the facility burst the frangible safety disk. conducting the inspection. well below the cylinder service pressure. October 1991 DOT permanent expansion of 10 percent or Two in column increased to five-thirds Scuba cylinders may be stored at full pressure for However, it has been traditional Standards and procedures for the visual inspecin detail pump, and measuring the the rated pressure of the cylinder. According to type low-voltage light that illuminates the entire inside of compressed gas cylinders are discussed a water- of cylinder expansion in terms of water the cylinder should be used for internal visual inspec- tion of in it pressure chamber, raising the pressure inside the corrosion. Cylinders should be inspected they receive especially hard service. tion. and neck cracks. There are several methods of hydrostatic testing of damage and if any); (if (7) internal cylinders, including direct expansion, pressure reces- internally by a trained technician at least once a year more presence of manufacturer's re-call items (6) cold water diving, because ice can in interrupted. for (5) sign(s) of substantial material removal; or metallic odor to the air in the cylinder. stage valve, causing the flow of air to the diver to be Both (4) defects in interior coating (if any); a cylinder can create a particularly danger- ous condition form and amount of cylinder contents (if any); magnitude of general, pit, or line corrosion; (1) type Cylinders should never be submerged completely filler and the cylinder to keep water from entering the cylinder. before the should be com- for: must be also enter the cylinder through the regulator the purge button neither is should be performed In general, the cylinder exterior tools. of air while being used with a single-hose regulator, water it only by persons properly trained and using appropriate taken to prevent moisture accumulation inside highpressure cylinders. visual cylinder inspection procedure complex nor time consuming, but — NOAA Diving Manual explosion may occur 4-9 Section 4 Rules for the use of scuba cylinders are: (1) Do not fill high-pressure cylinders if the date of the last hydrostatic test has expired (5 years for and aluminum cylinders) or steel year has passed since the 1 last if more than formal visual Charge cylinder at a slow rate to prevent exces- sive heat buildup. (3) valve of the double- hose regulator rides at the back of the diver's neck. The demand valve of the single-hose regulator positioned at is the diver's mouth, regardless of cylinder orientation. The demand valves of both types must be kept Never exceed the maximum allowable pressure any particular cylinder. Never perform maintenance or repairs on a in close minimum proximity to the diver's lungs to ensure a inspection. (2) demand this configuration, the hydrostatic pressure differential between demand valve and respiratory organs, regardless of diver orientation. If this is not achieved, the diver's respiratory system must work harder than necessary to overcome this for (4) cylinder valve while the cylinder (5) is charged. Handle charged cylinders carefully. Handling by the valve or body is preferred. Handling by straps or backpack may allow the cylinder to on orientation). Thus, the position of the cylinders on the diver's back hose regulator If diver's air especially important is charged cylinders an upright position in shady place to prevent overheating. Secure cylinders properly to prevent falling or in a cool, (7) when a double- employed. is to is be supplied by two or more cylin- ders simultaneously, a manifold assembly slip or drop. (6) Store depending differential during inhalation (or exhalation, to join the cylinders and provide a employed is common outlet. The manifold consists of sections of high-pressure piping and appropriate fittings specially configured and threaded to incorporate two or more cylinders, a valve, rolling. (8) Internal inspections, hydrostatic tests, and repair work should be performed only by those formally and frangible burst disks into a single functional In addition, Have cylinders visually inspected for interior deterioration annually (or depending on more frequently, use). (10) Inspect cylinders externally before and after each dive for signs of general pitting or rosion, dents, cracks, or other line cor- damage. Never use a welded, fire-damaged, uninspected, gouged, or scarred cylinder. (11) Remove cylinder boot periodically to inspect for corrosion and rusting. Boots that inhibit rapid draining and drying should not be used because they allow water to remain in contact with the cylinder, forming corrosion. (12) Do not completely drain the cylinder of air during dives. This prevents moisture from enter- may unit. also contain a reserve valve. The cylinder valve assembly trained to do so. (9) it is a simple, manually operated, multiple-turn valve that controls the flow of high-pressure gas from the scuba cylinder. the point of attachment for the demand It also is regulator. After the regulator has been clamped to the cylinder valve and just before using the apparatus, the valve is opened fully and then backed off one-fourth of a turn. It remains open throughout the dive. On completion of the dive, the cylinder valve is closed and should be bled atmospheric pressure, which prevents the O-ring from blowing out while the regulator is removed. to When a single cylinder supplies diver's air, the cyl- inder valve unit is generally sealed directly into the neck of the cylinder by a straight-threaded male connection containing a neoprene O-ring on the valve body. Most cylinders placed fitted with a valve ing the cylinder. without O-rings. in service before 1960 were having a 0.5-inch tapered thread When a single cylinder is utilized, the cylinder valve assembly houses a high-pressure burst WARNING disk as a safety feature to prevent cylinder pressure Aluminum Cylinders Should Not Be Heated Above 350° F (177° C) Because This Reduces conditions of elevated temperature. Old-style lead-filled from reaching a the Strength of the Cylinder and Could Cause Rupture critical level during charging or under blowout plugs must be replaced with modern frangible disk assemblies. When a pair of cylinders is employed, two burst disks are installed in the manifold assembly. Valve manufacturers use burst disks designed to rupture at between 125 and 166 percent of the cylinder service pressure. The rating may be stamped on the Cylinder Valve and Manifold Assembly face of the burst disk assembly to prevent confusion, Open-circuit scuba cylinders are normally worn on and disks of different pressure ratings must not be used interchangeably. Valves are not interchangeable between 4.3.3 a diver's 4-10 back with the manifold/valve assembly up. In NOAA Diving Manual — October 1991 Compressed and Support Equipment Air Figure 4-4 Valve Assemblies cylinders having different service pressures unless their respective burst disk assemblies are also interchanged. NOTE The standard cylinder valve assembly described above is known as a K-valve. A cylinder valve that incorporates a low-air warning/reserve air mechanism is known as a J-valve. 4.3.4 Low-Pressure Air Warning/Reserve A. Cylinder Valve B. Reserve Valve Mechanism Air Source: NOAA (1979) then made Several mechanisms are used in open-circuit scuba perform the important function of warning divers that the air supply is approaching a critically low level. to Some 300 or 500 psi (23 or 30 kg/cm 2 of air ) is available to the diver. of these devices also provide a reserve air supply Divers should be aware that the availability and that allows the diver to proceed safely to the surface. duration of the reserve air supplied through a reserve Such valve are dependent on the a device generally one of the following: J-valve, is submersible cylinder pressure gauge, or auditory warning mechanisms may be incorporated into valve/manifold assembly or into the demand the cylinder devices regulator. These and their limitations are device. These discussed in the following paragraphs. number of cylinders carried The 300 psi (23 kg/cm ) 2 as well as the depth of the dive. reserve available at actual cylinder pressure; is it is not above ambient pressure. Thus, at a depth of 100 feet (ambient pressure of approximately 50 psi), 300 psi only 250 psi (17 kg/cm starts to ascend. Also, the reserve valve 2 is ) available until the diver mechanism retains a reserve air supply only in one cylinder of a Reserve Valve twin set of cylinders; the other cylinder or cylinders The in reserve valve (also called a J-valve), illustrated Figure 4-4, is a spring-loaded check valve that begins to close as the cylinder pressure approaches a 300 or 500 psi (23 or 30 kg/cm ). Until this pressure is approached, the reserve valve permits an unrestricted flow of air to the regulator throughout the dive. At the predetermined pressure, a spring forces a flow check against the port orifice and restricts the air flow, causing increased predetermined level, generally when the reserve valve trips. mechanism is activated, the reserve are at a lower pressure When the reserve air distributes itself proportionately For this reason, the reserve valve in cylinders. all mechanism employed : breathing resistance. This tion of air flow The remaining if is followed by total obstruc- the reserve air is not manually released. with twin cylinders must be set to provide a 500-psi reserve. Unfortunately, reserve valve though generally mechanism is or mechanical failure and, 1/4", may reliable, the subject to physical if moved as little be tripped inadvertently early which allows the reserve air to damage as 1/8" to in the dive, be exhausted without the diver's knowledge. or reserve air can be released by manually overriding the spring-loaded check valve. NOTE NOTE Reserve valves should be inspected annually defects or whenever a malfunction is suspected. for The reserve valve position when lever must be in the down charging cylinders. 4.3.5 When a diver depresses the cylinder valve/manifold- mounted reserve lever, a plunger pin within the reserve valve advances, forcing the flow check to back off the orifice against the action of the spring. October 1991 — NOAA Diving Manual The remaining Submersible Cylinder Pressure Gauge Use of ure 4-5) is a submersible cylinder pressure a requirement in nearly scientific diving. all gauge (Fig- recreational and These gauges have largely replaced constant reserve valves and audio systems. When reading 4-11 Section 4 Figure 4-5 Gauges be positioned carefully as a result; the high-pressure hose can be run inside the waist strap on the back pack so that the gauges are located on the thigh in a read- When worn able position. improperly, a submersible pressure gauge positioned at the end of a 2- to 3-foot (0.7 to 1 m) length of high-pressure hose can increase the chance that a diver will foul on bottom debris .or become entangled with equipment. The gauge supply hose muSt be connected to a high-pressure port with compatible threads or be used with an adapter. The high-pressure hose normally has brass fittings with a restricting orifice. Should the high-pressure hose rupture, this orifice prevents rapid loss of cylinder air and allows the diver time to abort the dive and surface. Care must be taken to keep water from getting into the first stage of the regulator before the cylinder valve opened, because otherwise water could be blown is into the submersible pressure gauge and other regula- tor parts. Divers also should never scuba cylinders when the valve is off submerge and there their is no pressure in the attached regulator. Gauge readings much that err by as as 300 psi more may occur because gauge accuracy declines with use, especially if small amounts of water have entered the mechanism. Divers should therefore kg/cm (23 compare Courtesy William L. High ularly; 2 ) or their gauges to known cylinder pressures reg- gauges should be checked at various pressures. Professional dive facilities often use gauges in their high-pressure air systems that are accurate to a gauge is difficult, as is the case in low-visibility conditions, a constant reserve valve can be carried as well. In addition, dial faces that glow in the dark increase gauge readability under marginal light conditions. the Some newer gauges amount are able to provide data on make cylinders with known 1 sures available to their customers for comparison. NOAA all or pres- At diving units, pressure gauge testing devices are available that can be used for gauge calibration and to assess erratic needle movement. of time remaining for the dive at the cur- rent breathing gas consumption rate. This feature cal- culates the pressure drop in the cylinder over time and predicts the 2 percent so they can amount of air time remaining, assuming a continued constant rate of use. However, divers should be aware that changing their respiration rates can dramatically alter the amount of time remaining at WARNING Do Not Look Directly At the Face of Any Pressure Gauge When Turning on the Cylinder Because of the Possibility of Blowout low cylinder pressures. to The use of be added increased the when Because the accuracy of the slow indicator needle submersible pressure gauge has declines during normal use, the needle on a defective amount of information that can be obtained a diver monitors the submersible cylinder pres- sure gauge. ers, consoles that allow other types of gauges to the Maximum depth indicators, bottom tim- and compasses are now commonly associated with pressure gauges. However, this use of console gauge holders has added considerably to the mass of the high-pressure hose end, and the hose and gauge must 4-12 unit might stick, which could cause the pressure read- ing to be higher than it actually is. Divers in the field can assess the adequacy of submersible gauge needle function by releasing pressure from the gauge over a 3-minute period while they observe the needle for movement. Defective gauges must be returned to the manufacturer for replacement of parts. erratic NOAA Diving Manual — October 1991 Page SECTION 5 DIVER AND DIVING 5.0 General 5.1 Open-Circuit Scuba 5.1.1 EQUIPMENT 5-1 Demand 5-1 Regulators 5-1 Two-Stage Demand Regulators 5.1.1.2 Breathing Hoses 5.1.1.3 Mouthpieces 5.1.1.4 Check Valves and Exhaust Valves Preventive Maintenance for Regulators 5.1.1.5 Surface-Supplied Diving Equipment 5.1.1.1 5.2 5-6 5-6 Lightweight Free Flow Helmets 5-8 5.2.3 Lightweight Free 5.2.4 Umbilical Assembly Flow/Demand Helmets 5.2.4.3 Gas Supply Hoses Communication Cables Pneumofathometer Hoses 5.2.4.4 Strength 5.2.4.5 Hot-Water Hoses Assembly of Umbilical Members Coiling and Storage of Umbilical Hose Umbilical Maintenance Harness Weighting Surface-Supplied Divers 5.2.4.8 5.2.4.9 5.2.4.10 Members Diver Equipment. 5-8 5-8 5-9 5-9 5-9 5-9 5-10 5-10 5-10 5-10 5-1 5-1 5-1 5.3.1 Face Masks 5-1 5.3.2 Flotation Devices 5-1 5.3.3 Weight Belts 5-13 5.3.4 Diver's Knife 5-14 5.3.5 Swim 5-14 Fins Protective Clothing 5-14 5.4.1 Wet 5-15 5.4.2 Dry Suits 5.4.2.1 Dry Suit Insulation 5.4.2.2 Variable-Volume Neoprene or Rubber Dry Suits Hot-Water Suit Systems 5.4.3.1 Open-Circuit Hot-Water Suits 5.4.3.2 Hot-Water Heater and Hoses 5.4.3.3 Closed-Circuit Hot-Water Suits Accessory Equipment 5.4.3 5.7 5-5 5.2.2 5.2.4.7 5.6 5-5 Flow/Demand Masks 5.2.4.6 5.5 5-4 Free 5.2.4.2 5.4 5-4 5.2.1 5.2.4.1 5.3 5-2 Diver's Suits 5-16 5-17 5-17 5-18 5-18 5-18 5-19 5-19 5.5.1 Snorkels 5-19 5.5.2 5-20 5.5.3 Timing Devices Depth Gauges 5.5.4 Wrist Compass 5-21 5.5.5 Pressure Gauges 5-21 5.5.6 Underwater Slates 5-22 5.5.7 Diving Lights 5-22 5.5.8 Signal Devices 5-22 5 5.9 Safety Lines 5-24 5.5.10 Floats 5-24 5.5.1 Accessories That Are Not Recommended Shark Defense Devices Underwater Communication Systems 5.7.1 Hardwire Systems 5.7.2 Acoustic Systems 5.7.3 Modulated Acoustic Systems 5.7.4 Non-acoustic Wireless Systems 5-20 5-24 5-24 5-25 5-25 5-26 5-26 5-27 4 < DIVER AND DIVING EQUIPMENT GENERAL 5.0 This section describes diving equipment that has proven be reliable to in a Figure 5-1 Open-Circuit Scuba Equipment wide variety of underwater environ- New models and new types of diving equipment come on the market regularly, and divers should be ments. when selecting equipment to ensure that the equipment they have chosen is both safe and efficient. Diving equipment must be maintained properly to percareful form at its best; selection mental 5.1 and maintenance are funda- to safe, effective diving. OPEN-CIRCUIT SCUBA Self-contained underwater breathing apparatus (scuba) was developed to allow the diver freedom of movement under water. In this diving mode, divers carry their breathing medium on their backs, which allows dives to be conducted without surface support. A typical open-circuit scuba system consists of a compressed air cylinder (tank) that contains high- pressure air, a regulator that reduces the pressure of the air in the tank to a pressure equal to that of the environment (ambient pressure), and a means diver's of attaching the tank and regulator to the diver. A standard open-circuit scuba system is shown in Figure 5-1. Three major categories of scuba are currently in use: Courtesy U.S. Divers • Open-circuit demand; • Semi-closed-circuit (for mixed gas applications); • Closed-circuit. and To • equipment that is appropriate for a particular dive, divers must know and understand the difference between self-contained diving (open-circuit air) and surface-supplied diving. The advantages of open-circuit scuba are: It • The equipment needed can be carried for dives of long • Does not permit communication between the diver and the surface; • Cannot be used under conditions of poor visibility; Cannot be used for cold-water diving; and Requires a minimum of two divers (i.e., use of the buddy system) for safety. • • permits diver mobility; • Cannot supply breathing gas durations; select or trans- ported easily; • can be conducted from small boats (i.e., mode requires little support equipment); and • Training for this It The disadvantages • Cannot be used October 1991 mode is at great depths: Diving Manual 5.1.1 Demand Demand widely available. of open-circuit scuba are that — NOAA this Regulators regulators are used to reduce the pressure of the breathing gas coming from high-pressure cylin- ders to ambient pressure and to provide gas to a diver it: on demand; the pressure differential created by the respiratory action of the diver's lungs is the signal to 5-1 Section 5 Most depth or respiration rate and conserve the gas supply exhausted at the regulator through the hose leading over the left shoulder. The two-hose regulator is no longer widely used, and it is not currently in commer- by delivering only the quantity of breathing gas required. cial production. the regulator to provide gas to the diver. tors automatically adjust to changes regula- in the diver's The function of "upstream" and "downstream" valves is critical to the operation of regulators. An upstream is one that opens against the air flow coming from the high-pressure gas in the cylinder. Because this valve is forced closed by gas of higher pressure, it increases breathing resistance. If a major regulator malfunction occurs, the upstream valve is closed by valve the higher pressure gas, which, in turn, shuts off the diver's supply. As a consequence of this feature, these valves are only rarely manufactured today. stream valve, on the other hand, opens A down- same in the direction as the airflow, which causes such valves to be forced open by the higher pressure This method of air. operation results in smoother operation and reduced inhalation effort. Almost regulators are Many stage valves. all commercially available now equipped with downstream seconddifferent demand regulators are available that deliver breathing gas at remarkably consistent, low-differential pressures. The single-hose regulator first pressure reduction is designed so that the stage mounts directly on the tank manifold or valve, and the second pressure reduction stage is contained in an assembly that also includes a mouthpiece and exhaust ports. The first and second stages are connected by an intermediate pressure hose. Air is delivered from the first stage at intermediate pressure (110-160 psi over ambient) and from the second stage at ambient pressure. The exhaust gas is released into the water from the mouthpiece through the exhaust port (non-return valve). two-stage regulator is the most The common single-hose, regulator in use because of its reliability, simplicity, and ease of maintenance (Cozens 1980). Lighter weight plastics are being used in second-stage housings, and silicone rubber components have largely replaced less durable materials. The performance characteristics of secondstage components have also been improved by elimi- nating metal-to-metal interfaces. First-stage regulators are available in two types, 5.1.1.1 diaphragm and Two-Stage Demand Regulators Two-stage regulators are designed to reduce the breathing gas in a cylinder to ambient pressure in two stages. The first stage reduces the pressure to approx- imately 110 to 160 psi above ambient pressure, and the second or demand stage reduces the pressure from this level to ambient pressure. The major advantage of the second stage is that air is supplied to the demand stage which allows both a reduction in breathing resistance and fewer fluctuations caused by changes in depth and decreasing cylinat a nearly constant pressure, der pressure. Breathing resistance the (1 demand is reduced because valve works against a controlled pressure 10 to 160 psi above ambient from the produced in two and balanced (Figure 5-2). The diaphragm first-stage regulator (Figure 5-2a) contains an unbalanced upstream valve (i.e., high- acts against a flexible diaphragm. by the air still in combine is the double-hose lung developed by original two-stage regulator model similar to the original AquaGagnon and Cousteau in 1943, in which both pressure reduction stages are combined into one mechanical assembly that mounts on the tank manifold. Two flexible low-pressure hoses lead from either side of the regulator to a mouthpiece that contains both the inhalation The hose until equilibrium forces exerted During descent, the is restored. When the diver inhales, the reduced pressure in the intermediate is chamber dis- achieved. The balanced diaphragm and exhaust non-return valves. that leads over the right shoulder supplies the ure 5-2b) first-stage regulator (Fig- designed so that the valve stem extends anced configurations of the diaphragm first-stage regulator, failure of the diaphragm causes the valve to close. The unbalanced piston first-stage regulator (Fig- ure 5-2c) contains a downstream valve pressure air acts to open the valve). in the exhaled gas exits through the mouthpiece and pressure, is is completely through the high-pressure chamber; the operation of the balanced valve is thus independent of the tank (supply) pressure. In both balanced and unbal- breathing (inhalation) gas at ambient pressure, and 5-2 to activate the valve. The and the high-pressure demand few two-stage, two-hose regulators are use, and single-stage, two-hose regulators can The spring, the water (ambient), chamber displaces the diaphragm and opens the valve A be seen occasionally. spring applies a increasing hydrostatic pressure in the free-flooding librium regulators. A pressure air acts to close the valve). force that opposes that of the high-pressure air and places the diaphragm and opens the valve until equi- first stage). All single-hose regulators are two-stage piston; both types are configurations, unbalanced the free-flooding and chamber A (i.e., higher bias spring controls the intermediate a hole in the shaft of the piston allows NOAA Diving Manual — October 1991 Diver and Diving Equipment Figure 5-2 First-Stage Regulators of the valve a. therefore independent of tank (supply) is Unbalanced Diaphragm uration, failure of the piston seal tends to cause the • Diaphragm Valve Seat valve to fail in the open or free-flow mode. The second-stage HP [BM Air- Valve b. piece, —Water medium To 2nd Tension Stage Spring Seal\ HP a» To 2nd Ambient Water * Pressure Spring to Stage the improve the dynamic breathing characteristics of phragm inward, which reduces inhalation effort. On diaphragm returns to a neutral posi- Hollow exhalation, the Air Piston tion, releasing pressure on the stem or linkage, which returns to normal position, closing the medium- its pressure valve. To 2nd Stage As exhalation chamber to one-way mushroom valve \ Ambient x Water increases the pressure in Stem above ambient, levels A Adjustable imum of dead space, which limits the /Tension that will be rebreathed. / Spring Valve Seat properly constructed second stage has a min- The pilot number of To 2nd valve that Stage valve second stage also has regulators; is it amount of air been used with a incorporates an air supply opened and closed by air pressure rather than by mechanical leverage. The opening pressure Air downstream pilot valve. A simple mechanical linkage is used between the diaphragm mechanism and the Ambient Water Seals is generated by air flow through a diaphragm-activated Piston 'O" Ring a unseated, which allows water. Balanced Piston Hollow is the exhaled gas to be exhausted into the surrounding Pressure HP in the regulator; the venturi effect tends to pull the dia- the low-pressure d. chamber mouthpiece. In addition, most regulator manufactur- Valve Seat Seals The pressure to a valve in the mouthpiece. ers incorporate aspirators (venturi's) into their designs Stem "O" Ring by a medium- long as a diver inhales, air will continue to flow into the Diaphragm Unbalanced Piston HP to the first stage mouthpiece caused by inhalation results in distortion of a diaphragm. This distortion applies pressure to a stem or linkage that is connected directly to the mediumpressure air inlet valve, opening the valve and admitting air into the mouthpiece at ambient pressure. As Tension Valve Seat mouth- regulator, located in the reduction in pressure in a low-pressure Adjustable Air- connected is pressure hose; this hose, in turn, supplies a constant Pressure Balanced Diaphragm "O" Ring c. Ambient Adjustable Upstream and unbalanced config- pressure. In both the balanced Pressure pilot valve. Source: NOAA Because the pilot valve amount of spring tension needed to is very small, the counterbalance the (1979) pressure is small and less force close the valve. to The is pilot valve necessary to open and opens only a little way permit the air supply valve to pass a small amount of air into a control chamber. With this system, air supply the dry side of the piston to be equalized at the inter- valve openings larger than those used in conventional mediate pressure. During descent, the increasing hydro- leverage systems can be used in the second stage. static pressure in the free-flooding chamber displaces the piston, opening the valve until equilibrium restored. in When the diver inhales, the reduced pressure the intermediate chamber displaces opening the valve until equilibrium The balanced the high-pressure is the piston, achieved. movement chamber by an — NOAA is isolated is from 0-ring: the operation Diving Manual Because there is a piston opposite the valve opening that exactly counteracts the opening force of the air pressure, the supply valve is balanced and therefore not affected by intermediate pressure variations. is The system can be described as a pneumatically amplified piston regulator (Figure 5-2d) designed so that the piston October 1991 is second stage; this means that a small force, the valve, is pneumatically amplified to move pilot a larger force, the air supply valve. 5-3 Section 5 Figure 5-3 Breathing Hoses The aspirator port, mentioned previously, directed is A. Corrugated Hose B. Low-Pressure Hose Fitting toward the mouthpiece inside the regulator and gener- vacuum within As a result, less ates a slight is flowing. the regulator case effort tain air flow during inhalation. for demand is when air required to main- Although normally set breathing, the aspirator can be set for positive-pressure breathing. The regulator tive to pressure variations that, in dive/predive switch is is so sensi- some cases, a incorporated to decrease the Source: response of the regulator. Normally, a regulator requires NOAA (1979) a pressure or suction equivalent to that of a 2-inch cm) water column (5.1 to activate air flow; the pilot system requires a pressure equal to that of a 0.5-inch cm) water column. The operation of the regulator connections that are covered by hose protectors espe- (1.3 initiated is by a slight diaphragm to be drawn downward. The resulting linkage movement opens the pilot valve, and air flows to pressurize inhalation effort that causes the regulator the control chamber; this, in turn, opens the air supply valve. and The air between the structural arrangement pilot supply valves provides a controlling feedback move that allows the air supply valve to response to the pilot valve. The only in exact pilot valve acts as a safety relief valve in the event of first-stage malfunc- A tion. mechanical override also is incorporated into cially carefully before diving, because the protectors sometimes conceal damage. Mouthpieces The mouthpiece (Figure 5.1.1.3 5-4) provides a channel for the flow of breathing gas between the diver and the life-support system. piece differ The among size and design of the mouth- various manufacturers, but the mouthpiece generally is molded of neoprene, silicone rubber, or other materials that have a low deterioration rate. (Silicone rubber has the added advantage of the system to ensure operation in case the pilot valve being hypoallergenic.) Typically, the mouthpiece con- malfunctions. sists of a flange that teeth. Bits, Breathing Hoses 5.1.1.2 ure 5-3A) are flexible, large-diameter rubber ducts that provide passageways for air from the cylinder to the may Corrugated rubber hoses are common, but hoses also be made of rubberized fabric with metallic rings or spiral stiffening. To provide minimum resist- ance to breathing, the hose should have an inside diameter of at least 1 inch (2.5 cm) and should be long enough in the "relaxed" state to allow full freedom of body move- ment. The hose must be capable of stretching to twice its relaxed length without collapsing or buckling. Single-hose scuba, with the second stage of the regulator mask mounted or mouthpiece mount- demand ed, does not require the large-bore, ambient pressure breathing hose described above because the gas in the hose is at medium pressure (110 to 160 psi above ambient) rather than at ambient pressure (Figure 5-3B). or demand valve is connected to a cylinder-mounted first-stage regulator by a single, medium-pressure hose of relatively small diameter. Exhaled gases are discharged directly into the water The second-stage through an exhaust valve in the mask or mouthpiece. Breathing hoses should be checked for cracks or chafing before every dive. Divers should check the 5-4 between the space the jaws. The mouthpiece should In double-hose scuba, the breathing hoses (Fig- diver. fits diver's lips and one on either side of the opening, serve to comfortably fit and be held in place when a slight pressure is exerted by the lips and teeth. The novice diver often forgets that the bits are spacers and should not, under normal conditions, be used as grips. In an emergency, the bits will provide a reliable grip, but continuous force exerted through the teeth weaken the will bits and cause con- siderable fatigue of the muscles around the jaws. Many individuals have difficulty with temporal dibular joint (TMJ) pain when gripping man- the mouth- piece tabs too firmly during a dive. Mouthpieces that spread the load to the rear teeth are more comfortable. Learning to relax the jaw tive deterrent to On TMJ is probably the most effec- pain. a two-hose regulator, the mouthpiece assembly incorporates a system of one-way check valves, and clamps are provided for the breathing hoses. In a hose scuba regulator, the mouthpiece into the second-stage cases, the by a full demand is single- incorporated valve housing. In some mouthpiece assembly can be replaced entirely face mask. The use of a full face mask in lieu of a mouthpiece facilitates voice communication by freeing the diver's mouth; however, with this configuration, an oral nasal mask must be used to prevent carbon dioxide buildup. NOAA Diving Manual — October 1991 Diver and Diving Equipment Figure 5-4 Mouthpieces Double Hose A. B. Single Hose 5.1.1.5 Preventive Maintenance for Regulators Because regulators are one of the primary components of a life-support system, they require careful maintenance. An to ensure that no foreign matter has entered any of the essential element of maintenance is regulator's components; introducing foreign matter into an area of close tolerance or into a perfect seal could cause a malfunction. The primary entry point for foreign matter Courtesy U.S. Divers For the high-pressure inlet in the first stage. is this reason, the dust cap should be kept in position over the high-pressure inlet whenever the regulator is not in use. Salt water entering the high-pressure inlet will leave deposits of salt that 5.1.1.4 ation or pit valve surfaces. Check Valves and Exhaust Valves Check valves and exhaust valves (Figure 5-5) are designed to permit gas flow in one direction only. Check valves direct the flow of inhaled and exhaled gases through the breathing system. During inhalation, pres- chamber (now lower sure decreases in the mouthpiece successive days can substantially degrade the perform- ance of most regulators. Divers should be alert for early resistance moving is directed out through the mouthpiece to the exhaust valve. This pair of valves within the mouthpiece assembly minimizes dead symptoms of equip- ment malfunction. For example, increased breathing but opens the inhalation check valve. During exhala- and exhalation tube of a few drops of salt water into the high-pressure filter on several than ambient), which seats the exhalation check valve tion, the air can prevent proper oper- The addition may parts, be caused by the corrosion of internal and water leakage in the mouthpiece can occur as the result of deterioration of the second-stage exhalation valve. Other signs that indicate problems are rusting or clogging of the first-stage filter, free mini- flowing, and 0-ring leaks. These and other signs of mizes the rebreathing of exhaled gases. The inhalation trouble should be thoroughly evaluated before any air space within the system, and this, in turn, demand check valve also prevents water from entering the regulator An when the mouthpiece floods. exhaust valve is The most important maintenance a special check valve that per- mits the discharge of exhaled gas from the breathing system and prevents the entrance of water. valve (also called a flutter valve) exhaust valve mushroom in is A flapper typically used as an the double-hose regulator, while a valve generally single-hose model. A fulfills this function in flapper valve is simply the a soft rubber tube collapsed at one end; when ambient water pressure is further dives are made. greater than the air pressure within the a regulator is to be performed on a fresh water rinse after each use; this salt and other debris (sand, dirt, from the regulator and prevents deterioration. Rinsing should be done within a few hours of the completion of a dive, regardless of whether the dive was procedure removes etc.) conducted single- in fresh or salt water. Procedures for washing and double-hose regulators vary significantly and are discussed below. With a single-hose regulator, the first stage should valve, the valve remains in the collapsed condition. be held under a stream of warm, fresh water for at least During exhalation, however, the increase 2 minutes while the dust cap remains sealed in place, and water should be allowed to flow freely through any open ports. This is especially important with pistontype regulators, because it prevents the buildup of salt on the piston tracks. Because the dust caps pro- in pressure above ambient pressure forces the flapper open, allowing the gas to escape. Water cannot enter the valve while and when the pressure the higher pressure gas escapes, equalizes, the flapper returns to the relaxed or closed position. The mushroom valve on single-hose models is made of extremely soft, flexible rubber, which renders very sensitive to changes valve. A in pressure across the check wheel-shaped valve seat the rubber mushroom valve seat support the is fashioned to hold rinsing the regulator. When tor, the rinsing the second stage of a single-hose regula- diver should permit water to enter through the in place. Rigid spokes of the mouthpiece and mushroom valve against a clos- flow ing pressure but permit the flow of air when pressure within the mouthpiece exceeds ambient pressure. October 1991 it vided with some regulators are not watertight, the diver must make sure the cap is watertight before — NOAA Diving Manual in exit via the exhaust. Allowing water to the direction of the non-return exhaust valve washes sand, dirt, etc., out of the mouthpiece. The purge button should not be pushed unless the system is 5-5 Section 5 Figure 5-5 Check and Exhaust Valves 5.2 SURFACE-SUPPLIED DIVING EQUIPMENT One of the major constraints of scuba diving is the limited quantity of breathing gas the diver can carry; with umbilical (surface-supplied) diving, divers have them to spend more time on the bottom. The increased safety pro- a continuous air supply, which allows vided by umbilical equipment Source: NOAA (1979) is also important. In this mode, the diver is tethered and has direct voice communication, which permits safe operation under conditions considered too hazardous for the self-contained becomes fouled diver. If a surface-supplied diver pressurized, since doing so opens the air inlet valve and or disabled, a continuous air supply can be maintained through the middle- from the surface and a standby diver can locate the pressure hose to the high-pressure stage. If the regulator diver by following the entrapped diver's tether. In might allow dirty water is to pass to be stored for a long period of time, it may be remove the band holding the two sections of the second stage and the diaphragm in place and to desirable to rinse each separately. Rinsing procedures for the double- hose regulator are more complicated than for the single- hose model. As with the single-hose regulator, rinsing should be conducted with the watertight dust cap in The exhaust place. holes, side of the regulator has a series of and water should be allowed to flow freely through addition, if strong currents are a problem, the tethered diver can use additional weights to increase his or her stability. Surface-supplied diving can be conducted from locations: many from the surface, a habitat, a personnel transfer An capsule, or a lockout submersible. umbilical to the diver that runs from the gas storage cylinders of the habitat, capsule, or submersible provides the diver's (if required), and a communiThe major disadvantage associated with surface-supplied diving is that this mode requires more breathing gas, hot water cations link. this section. Care must be taken when rinsing the hose piece assembly because any water that high pressure into the mouthpiece may is and mouth- forced under bypass the soft rubber non-return valve and enter the intake side, which may cause corrosion. During rinsing, the mouthpiece should be held with the air inlet valve up, and water should be allowed to enter the mouthpiece, flow through the exhaust valve and hose, and exit at the main body of the regulator. To remove water from the corrugations in the hose, the hose should be stretched support equipment and personnel than is the case for the scuba mode. Many safe and efficient diving are available commercially. All masks and helmets masks and helmets provide the diver with a continuous supply of breath- and some models allow the diver to elect either demand operating mode. A communisystem is standard equipment on modern surface- ing gas, the free flow or cation supplied helmets. and the diver should blow through the mouth- lightly piece, allowing excess water to pass out through the exhaust. The To avoid hung by the mouthand weaken the hose. regulator should not be because piece, this will stretch cultivating bacteria in the corrugations, the interior of the hoses should be dried periodically. Scuba regulators should be tested functionally on a regular basis and at least as often as every 6 months. Perform- ing this test usually requires nothing more than Free Flow/Demand Masks The free flow/demand mask is designed 5.2.1 to be used with an umbilical hose that supplies breathing gas from the surface, an underwater habitat, or a personnel transfer capsule (submersible decompression chamFree flow systems supply sufficient ventilation for heavy work and also provide divers with an adjustable-flow, off-on supply to the interior of the mask ber). a manometer. through the muffler deflector. In addition to supplying the diver with a steady flow of breathing gas, the NOTE deflector directs gas across the viewing lens to prevent Hoses (especially exhaust hoses) should be removed periodically and should then be washed with surgical soap to prevent bacterial 5-6 buildup. fogging. When the umbilical hose breathing gas, the at all times. The demand pressurized with is regulator is regulator provides a pressure-loaded demand breath- ing system, similar to that of standard open-circuit NOAA Diving Manual —October 1991 Diver and Diving Equipment scuba, which Low volume Easy strap adjustment Secure strap fasteners adjustable for gas supplied at pressures • ranging from 60 to 180 psi over ambient pressure. Demand systems are preferred for light to moderate • work because they economize on gas requirements and enhance communication. A nose-blocking device is incorporated into demand systems to facilitate sinus and middle-ear equalization, and an oral-nasal mask assembly is used to reduce dead air space and eliminate the possibility of a dead air space carbon dioxide • Hypo-allergenic material • Tempered is buildup. Some lightweight masks and helmets conventionally used for surface-supplied diving are equipped with demand regular scuba regulators and can be adapted • Divers who must wear eyeglasses on land generally need some form of optical correction under water. Several methods for accommodating corrective lenses in divers' face masks have been developed: • masks consume more air • consumption rate should be determined at work loads before actual diving oper- • To permit buddy ations begin. breathing, an octopus • ability to utilize a tape recorder or diver-to-diver Lenses can be mounted • Standard glasses can be mounted inside the faceplate with stainless steel spring wire; • Face masks may be equipped with nose-blocking Each methods has advantages and disadvanworn inside a mask because the temples cause the mask to leak. Wearing of these lens inserts inside the face descent. Blocking off the nose to aid in equalizing sive but provides the ears is accomplished easily either by pushing upward on the bottom of the mask to create a when using masks with nose seal or gripping the nose pockets. Masks valve to aid high-quality also may be equipped with a purge in clearing water from the mask. Only masks with large purge valves are recom- mended, because purge valves are subject to failure or Face mask selection fit, is a matter of individual prefer- comfort, and other diver requirements. Masks are available in a variety of sizes and shapes that will accommodate the lens is different lens configurations. The closer located to the eye, the wider the peripheral (Egstrom 1982). Selection of a mask that well can provide easy clearing and an optimal visual field fits the-shelf mask simple and inexpen- is an extra surface to masks are available with Some fog. off- built-in correction; whether or not these are useful to a given individual depends on several factors, including the type and amount of refractive error, the similarity of error in the two eyes, and the interpupillary distance. The use of contact lenses under the face mask pro- vides good vision under water, offers a wide field of view, and eliminates problems with fogging. However, leakage. ence, and Soft or fenestrated contact lenses can be worn. devices to facilitate equalization of pressure during in frame and be tages. Glasses generally cannot be communication. pressure in a special secured to the inside of the faceplate; first stage. The advantages of this setup are greater comfort around the mouth and jaws during long exposures and the Large-size prescription lenses can be bonded perma- nently to the inner faceplate surface; several different second-stage regulator can be added to the Prescription lenses can be incorporated into the faceplate; than they do with regular scuba mouthpieces, and each diver's air Individual prescription lenses can be inserted into goggle-type masks; easily for use with self-contained air supply (scuba tanks). Divers using these safety glass. visual field. A plastic or clear problem with some of the new clear rubber masks is that they allow light to enter from the side, which may cause a mirror effect on some people do not tolerate contact some lenses cause corneal edema. The signs toms of corneal edema, which include discomfort, haloes around found lights, to and loss of visual acuity, The following features should be looked for when are used; soft lenses or fenestrated hard lenses do not cause this condition, which has been attributed to the inability of 1978, hard lenses to "breathe" (Simon and Bradley 1980). Because a dislodged lens can be very painful and debilitating, Cotter (1981) has suggested eye trouble" if means "lens or either diver wears contact lenses. options available to individuals selecting a face mask: have been occur when unfenestrated hard contact lenses that dive buddies establish a signal that the lens. and and symp- lenses well, who have (The different types of refractive error but wish to dive, and the • Light weight • Comfortable • Wide-angle vision • Easy closure of October 1991 advantages and disadvantages of the various methods, are discussed fully in Kinney (1985).) fit Ventilation across the faceplate generally nostrils for equalization — NOAA Diving Manual and the glass tends to fog easily. To minimize is poor, fogging. 5-7 Section 5 Figure 5-6 Lightweight Helmet the inside of the faceplace should be smeared with and then be rinsed before wearing. Anti-fogging commercial preparation) may be applied to the inside of the faceplate. The faceplate should be washed frequently saliva solutions (such as a mild liquid soap or a special in detergent to remove oils or which enhance fogging. If the drops of water should be surface film, both of mask fogs during use, the mask and should let into then be rolled across the fogged areas to clear them. If the mask has a purge valve, the valve should be thoroughly washed out to remove any sand that might prevent it from sealing properly. The mask should not be left in the sun for any extended period because make the headstrap and sealing edge Although the headstrap can be replaced easily and economically, cracking of the sealing edge will sunlight will brittle. make the mask useless. Self-contained emergency gas supply systems (or bailout units) are used in conjunction with surfacesupplied diving equipment to perform work at depths in excess of 60 pipes, etc., or feet (18.3 m), where there is when working ®Diving Systems International 1990 All Rights Reserved. in tunnels, the danger of entangle- ment. These units consist of a scuba cylinder assembly, a reduction regulator (i.e., first stage of a standard and a backpack-harness assembly. The capacity of the scuba cylinder assembly varies from 10 ft 3 to 140 ft 3 depending on the diver and the situation. Emergency gas may be fed directly into the diver's mask through a special attachment on the side single-hose regulator), , valve or be introduced directly into the diver's air hose assembly. In the latter case, a check valve must be located between the intersection of the emergency gas supply hose and the primary surface supply hose. A completely separate bailout system, which includes a scuba tank and regulator, may be used. If the umbilical air supply is lost, the full face mask must be removed before the diver ascends to the surface using the scuba tank and mouthpiece. If an emergency gas supply sys- tem is carried. selected, a second face The advantage mask should also be comcomputting on the face mask of this configuration is plete redundancy; the disadvantages are loss of munication and difficulty in and locating the regulator. standardized interchangeable fittings, improved valves, unbreakable faceplates, better ventilation (low C0 2 buildup), improved visibility, better communication, versatility because they can be used with any type of dress, bailout capability, and simplicity of use and maintenance. Modern helmets can be used with a neoprene wet suit, a hot-water suit, or a variablevolume suit. Some helmets attach to the neck bands of specially adapted dry suits for use in cold or contaminated water. 5.2.3 Lightweight Free Flow/Demand Helmets Free flow/demand system dry helmets combine the full head protection, communications, and the breathing characteristics of a standard dry helmet with the gas economy and comfort of a demand mask. Weight is distributed throughout the helmet to achieve balance and optimum performance without neck strain or effort. The helmet is designed to be advantages of neutrally buoyant in seawater. It auxiliary (or 5.2.2 Lightweight Free Flow Helmets Many equipped with an valve and with communication earphones and microphone. lightweight free flow diving helmets have been designed and manufactured in recent years. is emergency) system valve and a non-return An oral-nasal mask reduces the potential for C0 2 buildup. Some manu- facturers have constructed helmets of the traditional Assembly spun copper, which emphasizes indestructibility, while others use fiberglass and emphasize comfort, light 5.2.4 Umbilical weight, and maneuverability. In general, weight helmets and free flow/demand masks generally modern light- weight helmets (Figure 5-6) feature streamlined design, 5-8 The umbilical assembly for surface-supplied light- consists of a gas supply hose, a NOAA pneumofathometer Diving Manual — October 1991 Diver and Diving Equipment communications wire, and a strength member. Depending on dive requirements, a hot-water supply hose, a may hose assembled also be included. Umbilical in members continuous lengths; for example, low water diving operations to (i.e., depths are in shal- less than 90 fsw (27 m)), a 150-foot (45 m) assembly may prove satisfactory. Regardless of length, all members should The wire is fitted with ble with those on the connectors that are compati- helmet or mask. A waterproof, "quick-connect" connector four-conductor, often used; is these connectors have a socket-type configuration. When joined together, the four electrical pin connec- be in continuous lengths because umbilical assemblies designed with fittings and connectors have a greater and a watertight seal is formed, which insulates the wire from the surrounding seawater. To be secure and waterproof, these connectors should be molded to the communication cable. Profes- likelihood of failing or separating. sional installation tions are established is desirable. For field installation, rubber electrical tape overlaid with plastic electrical tape has been successful, although Gas Supply Hoses 3/8-inch (1.2 cm) or A larger synthetic rubber, braid-reinforced, heavy-duty hose carry the diver's air supply. is generally used to The hose must have a working pressure of at least 200 psig (this pressure must exceed the diver's required supply pressure). The outer cover of the hose must be durable and resistant to abrasion, weathering, oil, and snag damage. The inside tube of the hose must be non-toxic and impervious to any breathing gas to be used. Hoses must be flexible, kink resistant, and easy to handle. Although a hose may have a sufficient pressure rating, it may shrink considerably in length because it increases in diameter when pressurized, which causes looping of the other members of the umbilical assembly. To avoid problems, the percentage of shrinkage should be determined before purchasing the hose, and the assembly should be taped while the hose less is pressurized. than 150 psig, the change in At pressures nector, generally of the standard terminal post type, that is should be tagged with a serial number. is during use resistant to is compatible with the communications unit. Many divers use simple terminal or binder post connections on masks and helmets. The ends of the wire are prepared with solder, inserted into the binder post termi- and secured. Although less satisfactory than the mentioned above, the use of terminal or binder post connections is satisfactory and nal, special connectors economical. Standard two-wire "push-to-talk" communicators commonly used in diving. By using all four wires in the communication wire, the system can be set up so are that the diver's voice is "live" at all times. All commu- nication wires should be tagged or coded for record- keeping purposes, and lines should be checked before being issued for use on any dive. 5.2.4.3 lost less satisfac- length should not facilitate recordkeeping, all air supply hoses ging band that is The surface end of the wire should be fitted with an appropriate con- exceed 2 percent. To it tory than special molding processes. 5.2.4.1 damage and A metal tag- unlikely to be desirable. Purchase, test, and usage records should be maintained for each hose assembly. Pneumofathometer Hoses The pneumofathometer hose is a small hose that is end and connected to an air source and pneumofathometer at the surface. Pneumofathom- open at the diver's eters are precision pressure in feet gauges that are calibrated of seawater and are used to determine the pre- depth of the diver under water. Pneumofathometers must be protected from abuse and should be calibrated regularly. Lightweight air or oxygen hose (0.24-in. (0.6 cm) i.d., 200 psig working pressure) is generally used. Standard oxygen fittings are used for surface cise 5.2.4.2 Communication Cables Communication cables must be durable enough to when a strain is placed on the umbili- prevent parting cal assembly; they waterproof and must also have an outer packet that and abrasion-resistant. Multiconductor shielded wire (size 14 to 18) that has a is neoprene outer jacket diving. In at is satisfactory for shallow water normal service, only two conductors are used any one time. The wire-braid shielding adds consid- erable strength to the umbilical assembly. should be in a The cable continuous length, with an additional end and the surface end to allow room to install connectors, make repairs, and connect the communication equipment. few feet at the diver's October 1991 connections. oil- — NOAA Diving Manual 5.2.4.4 Strength Members The U.S. Navy recommends the use member in the umbilical assembly. The strength members include: of a strength lines used as cm) nylon braided line cm) synthetic polyolefin braided or • 3/8-in. (1.2 • 3/8-in. (1.2 3-strand twisted line 5-9 Section 5 cm) manila • 3/8-in. (1.2 • thin stainless aircraft-type cable. surface line • Each type of Braided nylon line has line is it advantages and disadvantages. and handling qualities, stretches under high load conditions; and expensive. Some divers use hollow- flexible "whip" (short length accordingly. zations, including the U.S. pact, lightweight, more used between the helmet and the main and the supply hose should also be adjusted organi- Navy, use this type of line. Polyolefin line floats and thus reduces the in-water weight of the umbilical assembly somewhat, but this type of line can be abrasive to the hands. Manila line is readily available and is the least expensive, but it deteriorates rapidly. Aircraft-type cable is strong, com- is umbilical air supply hose, the communication line although many If a lightweight, of hose) commonly used and has accepta- ble strength, durability, placed on the harness and not on the diver's is helmet, mask, or fittings. • If a whip and special auxiliary air supply line valve are used for helmet diving, their length should be adjusted. The diver should have sufficient hose and cable length between the safety harness attachment point and the mask (or helmet) to allow unrestricted head and body core polyolefin line, with the communications line run- movement without placing ning through the hollow core, to combine the strength connections. Excessive hose should not, however, form and communication members. strength A few combination lines are com- member/communicator wire between the harness connection and the a large loop mask. The communication mercially available. excessive stress on the hose should be slightly longer line than the rest of the assembly to permit repairs at the diver's end. 5.2.4.5 Hot-Water Hoses When hot-water wet suits are worn on a dive, a specially insulated hose is required. This hose can be obtained in either 1/2- or 3/4-inch (1.2 or 1.8 cm) inside diameter size, ume The snap hook that depending on the depth and of water to be supplied to the diver. The vol- insulation is diver's end should be fitted with a secured to the strength member and the rest of the assembly to facilitate attachment to the safety harness. The surface end of the strength mem- ber and other components also are secured to a large D-ring, which allows the assembly to be secured at the diving station. reduces the loss of heat to the open sea, which allows a The hose should be equipped with a quick-disconnect female fitting that is compatible with the manifold attached to the lower boiler operating temperature. suit. To prevent handling problems, the hot-water hose 5.2.4.7 Coiling and Storage After the umbilical hose of Umbilical is assembled, Hose it should be stored and transported; protection should be provided should be joined to the diver's gas and communications for hose umbilical. dures. and communications fittings during these proce- The hose ends should be capped with plastic protectors or be taped closed to keep out foreign mat- and to protect threaded fittings. The umbilical hose may be coiled on take-up reel assemblies, "figureeighted," or coiled on deck with one loop over and one ter Assembly 5.2.4.6 of Umbilical Members The various members of the umbilical assembly should be bound together with pressure-sensitive tape. Twoinch (5 cm) wide polyethylene cloth-laminated tape or is commonly used. Prior to assembly, the members should be (1) laid out adjacent to each other, and (2) inspected for damage or abnormal- duct tape various and connections should be installed in advance. The gas supply hose and pneumofathometer hoses should be connected to the air supply and should ities; all fittings loop under. Incorrect coiling, all in the same direction, will cause twist and subsequent handling problems. The tender should check the umbilical assembly at the end of each dive to ensure that there are no twists, and the coil should be secured with a number of ties to prevent uncoiling during handling. Placing the umbilical assembly in a large tarpaulin will prevent canvas bag or wrapping damage during it in a transport. be pressurized to about 150 psig to ensure that shrink- age does not cause looping. The following 5.2.4.8 guidelines should be observed when assembling umbilical members: • The strength member should terminate to hook After a day's diving, the umbilical should be washed with fresh water, be visually inspected for damage, in a position to the diver's safety harness, generally on the left-hand side, so that the strain of a pull from the 5-10 Umbilical Maintenance and be carefully stored to prevent kinks. If the umbili- be stored for a long period of time, the hoses should be blown dry and the connectors should be cal is to NOAA Diving Manual — October 1991 Diver and Diving Equipment capped foreign matter from entering. Con- to prevent required for weight belts fresh-water washing after is nectors should be lubricated with silicone spray after use and predive checks of the quick-release capping. to ensure that 5.2.4.9 The tate Harness wear a harness assembly to faciliattachment of the umbilical assembly. The hardiver should ness should be designed to withstand a 1000-pound (454 kg) pull in minimum any direction, and it of a must mask or helmet when a pull is taken on the hose assembly. The location of the attachment depends on the type of harness assembly worn by the diver, but the harness prevent strain from being placed on the diver's should not be attached to the weight belt latter mechanism operating properly. is it in case the needs to be dropped. 5.3 DIVER EQUIPMENT The on-scene dive master determines which items of equipment are required to accomplish the particular underwater task. Unnecessary equipment should be left on the surface because excessive equipment can become a hazard rather than an asset. This is particularly true when diving in a strong current, under conditions of limited visibility, or in heavy surge, because each additional item of diving equipment (especially additional lines) increases the probability of fouling the diver. WARNING Diver equipment considered in this section includes face masks, flotation devices, weight belts, knives, and Never Attach the Diver's Umbilical Directly Weight Belt. A Separate Belt or Harness is Required To Permit the Weight Belt To Be Dropped If Necessary to the swim 5.3.1 5.2.4.10 Weighting Surface-Supplied Divers To weight the diver properly, lead weights (3, 5, or 8 lbs (1.4, 2.3, or 3.7 kg) The with bolts. wide and is belt is each) are secured to the belt approximately 4 inches (10.2 cm) fitted with a quick-release fastener. The weight belts used for arctic diving are heavier than most belts because of the bulk and positive buoyancy of cold-water exposure suits. A shoulder harness that is similar in configuration to a fireman's suspenders is the best belts method of preventing the heavy, unwieldy from slipping off. If a leather belt should be coated regularly with neat's-foot Weighted shoes or leg weights may is used, overcome bility to the diver. positive the diver's eyes and the water. There are two general classes of face masks: separate face be used buoyancy and in mask, which covers only the eyes and nose, is generally used for scuba diving (when equipped with a mouthpiece) or for skin diving. Full face masks are used with special scuba and surface-supplied diving apparatus. Full face masks consist of The faceplates con- to give sta- and a protective brass toe piece. Leg weights consist of one large or several small weights attached to leather or nylon straps. The straps are fitted with buckles for securing the weights to the The weights vary from pounds (0.9 to 4.5 kg) each, depending on the Leg weights provide improved stability and protection against blowup, because divers wearing variable-volume suits can swim with relative 2 to 10 diver's preference. ease while wearing fins and leg weights. For safety, the weight belt should be worn outermost so that it can be freed easily when released. The only maintenance Diving Manual masks and full The separate face masks (Figure 5-7) (Hall 1980a). tic, place, — NOAA Face Masks Face masks are used to provide increased clarity and visibility under water by placing an air space between a faceplate, a frame, made are tempered safety a lead or brass sole, leather straps to hold the shoe in October 1991 sections below discuss each of these and a headstrap. of highly impact-resistant, it Standard weighted shoes consist of diver's legs near the ankle. The (Glass glass. is still better than plas- oil. junction with the weight belt (primarily by tethered divers) to fins. items in turn. because plastic faceplates are subject tion, abrasive to discolora- damage, and fogging.) The frame is designed to hold the faceplate and to provide a watertight seal; it is usually made of plastic. Silicone rubber has largely replaced less durable materials as face seal components; the widespread use of silicone materials in diving has significantly extended the useful life of most rubber components. The mask should be sufficiently rigid to hold the rubber plate away from the diver's nose and should be pliable enough to ensure perfect and still retain its approximately rear holds the l An inch (2.5 mask 5.3.2 Flotation A shape. fit adjustable rubber headstrap cm) wide and split at the to the diver's head. Devices is an essential part of a diver's and buoyancy control system; it is also an flotation device life-support 5-11 Section 5 Figure 5-7 Face Masks A. Separate Masks item of rescue and safety equipment. Many different buoyancy compensators have been developed during the past few years, including those with the popular stabilizing jacket and compensators using the horse collar designs (Figure 5-8). and These devices are available backpack-mounted as vest units, units, stabilizer jackets, wide range of variable-volume dry suits. Although almost all divers would agree that some type of buoyancy compensation is necessary, they would not agree about which configuration or design is best. When selecting a buoyancy compensator (BC), a number of factors must be considered, including: type in a of exposure suit, type of scuba cylinder, diving depth, characteristics of the breathing equipment, nature of diving activity, and type of accessory equipment and BC weight belt (Snyderman 1980a, 1980b). The be compatible with the exposure suit. must NOTE Buoyancy compensators should not be used ability and physi- as a substitute for swimming cal fitness. Flotation devices should be designed so that a diver, even when unconscious, will float with face up. The mechanism of the device should be constructed of corrosion-resistant metal, and a relief valve should be part of the device when it is used for buoyancy compensation. Most devices are designed to inflate inflating Courtesy Glen Egstrom B. Full Face Mask automatically either tured or when filled when a C0 2 cartridge is punc- with air supplied by a low-pressure hose from the scuba cylinder. Regardless of their method of inflation, all flotation devices should be with an oral inflation tube. The equipped oral inflation tube should have a large diameter and be able to be operated with either hand. Recent studies have determined that a minimum of 25 pounds (11 kg) of positive buoyancy is required to support a fully outfitted diver operating in Sea State 1 conditions. To achieve this, a 19-25 gram C0 2 car- must be used with a properly designed buoyancy compensator. U.S. Coast Guard regulations require life vests to have a positive buoyancy of 24.5 pounds (11 kg) to support a fully clothed adult. Divers and boat operators should keep themselves informed about tridge the status of life vests (personal flotation devices), because, for example, the Coast Guard recently issued a warning cautioning against the use of vests in ' B Diving 1990 5-12 Systems All rough water because they will not Type III life keep a diver's International Rights Reserved head clear in choppy water. Flotation devices that use NOAA Diving Manual — October 1991 Diver and Diving Equipment Figure 5-8 Flotation Devices with a silicone lubricant. The threads on CO, the car- tridge should also be lubricated. The most frequent cause of flotation device mal- corrosion caused by salt water entering the function is inflation compartments; the resulting residue can block C0 2 and cause significant deterioration mechanism. If this occurs, the device should be filled approximately one-third full of warm fresh water, the water should be circulated rapidly through the vest, and the water should then be the passage of of the inflation-release drained out through the oral inflation tube. Fresh water also should be flushed through the passage the vest and the between C0 2 cartridge. Courtesy Glen Egstrom NOTE larger cartridges than those required, multiple cartridges, and one or two available; these pensators if the oral or inflation compartments are also models can be used as buoyancy com- Buoyancy compensators should not be worn with a variable-volume dry suit if the BC hinders easy access to the suit's valves. the diver partially inflates the device through power inflation tube while he or she is still Periodic checks of the inflation device are also The device should be required. submerged. Specially designed buoyancy compensators that have and separate inflatable cham- large oral inflation tubes bers are commercially available. A large cylinder of inflated and hung up over night and/or be submerged periodically to check for leaks. If leaks are observed, they should before the device is used again. The C0 2 be repaired cartridges chargeable from a standard scuba air cylinder is an integral part of some buoyancy compensators; this arrangement allows for partial or complete inflation while the diver is submerged. Pressure relief valves are provided for each compartment should be weighed frequently to ensure that they have to prevent overinflation. with that device. Cartridges should also be inspected compressed air that Training divers is use of specific in the BC devices essential because these devices vary widely in control locations, control operation, is terms of and potential buoy- not lost their charge; grams less if their weight is more than 3 than the weight printed on the cylinder, the cartridge should be discarded. flotation device should The cartridge used in a be the one designed to be used to ensure that the detonating mechanism has not punched a pinhole into the top of the cartridge that has allowed the C0 2 to escape. ancy. Regardless of the diver's choice, training and practice under controlled conditions are required to master buoyancy compensation procedures. Divers must WARNING be trained not to use excessive weights or to be overly BC to compensate for diving weights. Because rapid, excessive inflation can cause an uncontrolled ascent, divers must learn to vent air from dependent on a Buoyancy Compensators Should Not Be Used As Lift Bags Unless They Are Not Attached To the Diver the compensator systematically during ascent to maintain proper control. After each use, the exterior of the device should be rinsed thoroughly with fresh water. Special attention C0 5.3.3 Weight Belts Divers use weight belts to achieve neutral buoyancy; mechanism, oral and power inflators, and other movable mechanical parts to ensure that they operate freely and easily. The they should carry enough weight so that their buoy- C0 2 positive should be given to the 2 release actuating lever, with cartridge removed, should ancy at the surface and becomes is slightly negative with a full tank slightly positive as air buoyancy provided by the is consumed. The diver's suit is prob- be worked up and down while fresh water is being flushed through the mechanism. The mechanical parts ably the largest contributing factor in determining should be allowed to dry and should then be lubricated suit, October 1991 — NOAA Diving Manual appropriate weight requirements. Without an exposure most divers can achieve neutral buoyancy with 5-13 Section 5 Figure 5-9 Fins Swim than 5 pounds (2.3 kg) of weight, whereas 10 to 30 pounds (4.5 to 13.5 kg) may be required, depending on depth, if a full suit is worn. Dry suits may require even less more weight. Divers must accurately determine weight requirements their water before undertaking in shallow a working dive. Failure to establish the proper buoy- ancy can consume following test air and energy unnecessarily. The can be performed to determine the proper amount of weight to be carried: a full lung of air at the maintain a properly weighted diver at surface should water; exhalation should cause the eye-level with the diver to sink slowly, while inhalation should cause a slow rising back to eye-level with the water. (This test should only be performed on the it As a general rule, the deeper the dive, the less because status.) weight will be required to achieve the desired buoy- ancy because of the exposure When suit's compressibility. using exposure suits with increased thickness or should be taken to ensure that the diver air spaces, care has adequate weight to permit a slow, easy ascent, especially during the last 10 feet (3 m) of ascent. 5.3.4 Diver's Knife A diver's knife serves a variety of purposes, the common most being to pry and probe at underwater rocks, organisms, etc., and to free the diver in the event of entanglement (Boyd 1980). A diver's knife should be constructed of a corrosion-resistant metal, preferably Handles must provide a good, firm grip The knife should be worn where it is easily accessible in an emergency; knives are worn on the inside of the calf or on the upper stainless steel. and be resistant to deterioration. arm. Carrying the knife on the inside of the calf popular because this position makes ble with either hand and Courtesy dive of the day last will influence the diver's repetitive dive it is readily accessi- lessens the likelihood that the and are slightly more flexible than the and they use approximately as much force on the up-kick as on the down-kick. The swimmingstyle fin is less fatiguing for extensive surface swimming, less demanding of the leg muscles, and more comfortable. Power-style fins are longer, heavier, and more rigid than swimming fins. They are used with a slower, shorter kicking stroke, with emphasis on the power style, down-kick. This style of fin cal condition Swim fins blade is sharp; if The properly maintained, the material to be performed. inside, or diving in kelp beds, surf grass, or pond weeds. If this may knife should be rinsed with fresh water, dried, and to ensure that the and the nature of the task down before larity prior to storage. maximum with adjustable heel straps either should the ends of their straps taped progress. oil designed for have the straps reversed, with the bitter ends plants must be checked frequently is power thrusts of short duration, and these fins sacrifice some comfort; power fins are the preferred style for working divers. A narrow, more rigid fin provides the best thrust-to-energy cost ratio. The fin must fit comfortably, be sized properly to prevent cramping or chafing, and be selected to match the individual's physi- knife itself will foul. This placement also maintains a knife Divers, Inc. lighter weight, clear drop-path for the weight belt. After each use, the coated with a layer of light New England A catch in the straps number is not done, and impede further of plastic fins have gained popu- because of their good propulsion characteristics and light weight; these fins couple a plastic blade with a neoprene rubber foot pocket and an adjustable heel strap. used in most diving knives will retain a good cutting edge for a long time. 5.4 PROTECTIVE CLOTHING Divers usually require some form of protective cloth- 5.3.5 Swim Fins ing. This clothing, known as a suit or insulation, mini- available in a variety of sizes and designs. mizes thermal exposure effects. In addition, it protects the diver from abrasions and minor bites. Suits must be selected with certain diving conditions in mind; elements to consider include water tem- In general, there are two styles of fins: swimming and power (Hall 1980b). Swimming fins are smaller, of should be considered Swim fins (Figure 5-9) increase the propulsive force of the legs and, when used properly, conserve the diver's energy and facilitate underwater movement. They are 5-14 perature, depth, and activity level. The following points when evaluating thermal needs: NOAA Diving Manual — October 1991 Diver and Diving Equipment Figure 5-10 Neoprene Wet trapped air or gas. • All insulation • Cold water absorbs heat 25 times faster than Fifty percent of the average diver's energy • Suit is air. is con- sumed just trying to keep the body warm. The greater the temperature difference between the body and the surrounding water, the faster • heat leaves the body. The • larger the body mass, the better the heat retention. • takes time, rest, and food to replace lost heat It energy. 5.4.1 Wet Suits The neoprene wet suit the most is common form protective clothing in use (Figure 5-10). It of provides thermal protection, as well as protection against coral, stinging coelenterates, and other marine hazards. suits are Wet constructed of closed-cell foamed neoprene and generally are 3/ 16- or 1/4-inch (approximately cm) thick, although suits as thin as 1/8 (0.3 cm) and as thick as 3/8 of an inch (1.2 cm) are available. Wet suits rely on air bubbles in the closed foam to act as insulation. Because the foam is compressible, how0.6 ever, the suit rapidly loses insulative capability as its depth increases. For example, one-half of a wet insulating capacity is suit's 33 feet (10 m), two-thirds lost at 66 feet (20 m), and three-fourths at 99 feet (30 m). Consequently, wet suits are recommended only for at shallow water diving or snorkeling and generally are recommended not for diving in below 60°F (15. 6°C). The wet suit used in warm water at temperatures Courtesy Diving Unlimited International water consists of neoprene pants and jacket, with optional boots, gloves, hood, and vest. For warm-water (80°F; 26.7°C) diving, a brief vest that covers only the body's trunk Full-length styles that cover the entire ing the hands, feet, is available. body (includ- the effectiveness of a wet suit; some Fit is divers important to may need a custom suit to achieve proper fit. Thinner suits provide more freedom of movement, while suits of thicker mateprovide better thermal protection. Most suits use a nylon liner on the inside surface of the neoprene to limit tearing and is to facilitate easy entry. Models are available with nylon on both the inner faces to minimize tears and damage to and outer surthe suit; howev- prevent separation. Neoprene glue surface nylon does not repair well with ordinary cement, have as many as in, which may be a probNylon on the outside cuts down on abrasions but tends to hold water, which acts as an they also allow water to seep lem suit in cold water. October 1991 — NOAA Diving Manual five zippers, one in A wet suit may each ankle and sleeve and one in the front of the jacket. In colder waters, zippers can loss, if become a significant source of heat and care should be taken either number suits are flexible suit, available in small so tears in this material should be sewn. suits with nylon inside offer easier entry into the is cans for quick and easy wet suit repair. However, double- length and the the diver glue. added layer of nylon further restricts the diver's movements, as do elbow and knee pads. Although wet er, when on the surface. The sections of a wet suit are joined by neoprene The seams on better models are sewn together to and head) except the face are available for use in colder waters. rial evaporative surface and causes chilling to minimize zipper or to provide waterproof zippers extended cold-water work is anticipated. Some and strong enough to be constructed without ankle and sleeve zippers. When water temperatures approach 60 °F (15.6°C), the hands, feet, and head lose heat at a rate that makes 5-15 Section 5 Figure 5-11 Effects of Water Temperature diving without protective gloves, boots, and a hood °C impractical. Even in tropical climates, divers often elect to Normal Body Temperature wear some form of boot and glove for abrasion In colder waters, loss of body heat from 35 — 4 Resting protection. these body areas may Diver 30- formance unless some form of thermal protection is worn (Figure 5-1 1). Thermal protection of the hands is necessary because tiveness. Most divers in movement and -80 During Resting Diver Chills 25H Moderate In Work temperate climates prefer cot- touch. Five-fingered prene gloves are available in foamed neo- 1 -2 Hours -70 20- ton gloves because these gloves do not severely restrict finger Overheat 4 Working Comfortable reduces a diver's effec- loss of dexterity significantly Will -90 significantly affect diver per- Diver s Underwear 0) May 1/8- or 3/16-inch (0.3 to Suffice 60 15- 'Approximate Tolerance Time cm) thicknesses that permit a satisfactory degree of finger movement. Three-fingered "mitts" are used 0.4 in cold water (Figure 5-12). Proper because too tight a will restrict fit and increase the rate of heat fit is Of Working Suits etc. important Diver Without Protection -50 10- I Required 2 1 blood circulation Hours loss. -40 Failure to wear a hood in cold water can result in Fresh numbing of the facial areas and a feeling of extreme pain in the forehead immediately on entering the water, -30 Water Freezing Sea Point Water phenomena that persist until the head becomes acclimated to the cold. Fifty percent of body heat can be -5- from the head and neck during submersion in cold water. Hoods that are attached to jackets generally lost provide better thermal protection than separate hoods. The hood should have an adequate at least midway onto skirt, Source: one that extends NOAA (1979) the shoulders, to prevent cold water from running down the spine. In extremely cold water, a one-piece hooded vest is recommended. Fit important when selecting a hood because too tight a is fit to rot, become brittle, and crack. Storing suits in hot, dry environments also can lead to deterioration. can cause jaw fatigue, choking, headache, dizziness, and inadequate thermal protection. Wet suits must be properly cared for and maintained 5.4.2 Dry Suits should be washed thoroughly with Dry suits that are made of waterproof materials are becoming more widely used than wet suits. Commonly should then be allowed to dry before called shell suits, these fabric suits are designed to be being stored. The suit should be inspected carefully for worn with undergarments; they are usually used with if they are to last for a each use, the fresh water; rips; if suit it reasonable length of time. After any are found, the before being used again. mately 10 minutes after best results it A it should be repaired suit suit can be used approxi- has been repaired, but for should not be used for several hours. Suit zippers and metal snaps should be inspected frequently and be kept corrosion lubricants; petroleum-based products will cause neoprene materials Dry suits can be inflated via the to deteriorate. regulator, and air inside the suit an exhaust valve. Some Suits should be hung for can be expelled through automatic buoyancy control. By manipulating the valves, a properly weighted diver can maintain buoyA power exhaust valve can ancy control at any depth. evacuate excess air from the They may easier to deflate. up or laid flat, but they should not be folded because prolonged folding may cause creasing and deterioration of the rubber at the folds. also be rolled Suits should be stored out of direct sunlight because 5-16 on the valves are equipped with an on wide, specially padded hangers to prevent tearing. prolonged exposure to the sun inlet valve diver's air supply at the low-pressure fitting on the adjustable over-pressure relief mechanism, which allows free. Special silicone greases are available for use as equip- ment hoods and gloves and are relatively easy to doff and don. will cause the neoprene Because flotation capability, a suit, which makes the suit have no inherent shell suits buoyancy compensator that does not cover the suit's valves should be worn. Dry suits must be maintained properly. They should be washed with fresh water after each use, and water NOAA Diving Manual — October 1991 Diver and Diving Equipment Figure 5-12 Cold-Water Mitt, Liner Included Underwear made of such material provides primary thermal protection when divers wear a dry the shell of the suit loses garments have diver's other outer lation. suit because insulation with depth its little and a inherent insu- Leaks can always be a problem with shell suits; however, divers equipped with dry suits and nylon pile or Thinsulite® undergarments have been able to work 2°C intermittently for 6 hours in (35 °F) water (Zumrick 1985). Variable-Volume Neoprene or Rubber Dry 5.4.2.2 Suits Variable-volume dry suits differ from dry fabric- They are one-piece suits that are made of foamed neoprene or rubber compounds. These suits are designed to conserve body heat in shell suits. closed-cell extremely cold water for an extended period of time (Hall 1980c). Variable-volume rubber suits are light and require no surface support, which makes them ideal for use at remote locations. These suits also are simple and reliable, which greatly reduces their maintenance and repair requirements. Operations have been conducted using suits of this type for in arctic regions long-duration dives (2 hours) under ice in 28.5 °F to 30°F(-1.9°C Most (0.4 or 0.6 Courtesy Trelleborg/Viking to -l.rC) water. suits are constructed of 3/ 16- or cm) closed-cell 1/4-inch foamed neoprene and have a Inc. One style is availacompound over a tricot nylon interior and exterior lining. ble that is made from a rubber should be sprayed directly into the suit's valves to material. All suits of this type are designed to be wash out sand. If the suit develops mildew spots, it should be washed with soap and water. Finally, the suit with thermal underwear, are of one-piece construc- should be allowed to dry while hanging so that proof zipper. it will tion, worn and are entered through a water- and pressureThe hood and boots usually are an inte- dry thoroughly inside and out. gral part of the suit, but the gloves are separate. Dry suits should be stored away from sunlight and from ozone-producing sources, such as cars or gas- prevent separation, fired household water heaters. The can be extended by storing the life of the suit's abuse, knee pads often are attached permanently to the suit to bag with talcum powder during long periods of non- The suit in a use. To seams are glued and sewn. Because the knees of the suit are the point of most frequent dry plastic seals all reduce the likelihood of leaks. suit may be inflated via an to the diver's air inlet valve connected supply at the low-pressure fitting on the regulator. Air inside the suit can be exhausted 5.4.2.1 Dry Suit Insulation determined by water temperature, duration of the dive, and the age, body size, sex, and exercise rate of the diver. However, many suits are insulated with materials that trap air and stabilize it. The most common insulation materials in use are synthetic fibers polyester, nylon, in piles, and polypropylene. These made fibers, of used buntings, and batting, are selected because of their low water absorption. October 1991 — NOAA the inlet valve or one on the suit's arm. By manipulat- two valves, a properly weighted diver can maintain buoyancy control at any depth. When diving in cold weather, care must be taken to avoid icing of the suit's inlet and exhaust valves. The inlet valve may be frozen in the open position if the suit is inflated with long bursts of expanding air instead of ing these several short bursts. open position, the When suit uncontrolled ascent. Diving Manual from either by a valve on the opposite side of the chest The amount of suit insulation needed for a particular diver to remain comfortable on a given dive is If the inlet valve freezes in the may overexpand and there is more cause an air in the suit than 5-17 Section 5 Figure 5-13 Open-Circuit Hot-Water Suit the exhaust valve can exhaust, the diver should hold up one arm, remove his or her tight-fitting glove, and allow the excess air to escape under the suit's wrist seal. The disadvantages of variable-volume dry suits are: • Long • Air can migrate into the foot area suits are fatiguing because of the suit's bulk; if the diver is horizontal or head down, causing local overinflation and • • loss of fins; and exhaust valves can malfunction; and seam or zipper could result in sudden and drastic loss of buoyancy, as well as significant Inlet A parting thermal stress. Divers planning to use any type of variable-volume dry suit should be thoroughly familiar with the manufacturer's operational literature and should perform under controlled conditions before wearing training dives the suit on a working dive. Maintaining variable-volume dry suits is relatively simple. After every use, the exterior of the suit should be washed thoroughly with fresh water, and the suit should then be inspected for punctures, tears, and seam separation, all of which must be repaired before reuse. The zipper should be closed, cleaned of any grit, and lubricated. The zipper should be coated with waterproof grease after every few uses. The inlet and outlet valves should be washed thoroughly and lubricated before and after each dive. Cuffs, collar, and face seals also require lubrication with pure silicone spray before courtesy Diving Unlimited International and after each dive. The inflation hose should be inspected before each dive. warm water tribute feet, 5.4.3 Hot-Water Suit Systems Hot-water warm by suit warm water. A hot- water system heats and closely controls the temperature of the water that is pumped through the heated water evenly over the diver's body inside the passive insulation of the specially constructed suit An seals. open-circuit hot-water suit allows the heated water to flow back to the open sea after use, while a closed-circuit hot-water suit returns the warm water to the heater for rewarming. Hot-water systems The control manifold The suit's used and neck suit allows arm, must have a leg, single valve to allow water to bypass the diver and to return directly to the surrounding water. a specially insulated hose to the diver; the system then distributes (Figure 5-13). torso. water to leak out through the systems are designed to keep divers encapsulating them in to the diver's arms, hands, legs, and front and back The hot water that supplies suits of this type does not recirculate the dumped warm water; instead, water can be used to protect more than one diver at a time water supply the hot water in the suit, which allows the diver 1 5.4.3.1 made of passive insulation material; they are equipped with a control manifold and tubing to 5-18 is interrupted, the non-return valve retains up to 8 minutes to return to the bell or surface. Open-Circuit Hot-Water Suits Open-circuit hot-water suits are loose fitting and are is into the sea through the suit's vents. If the and to heat a diving bell. may and be pumped directly to the diver or be passed to the diver from a diving bell, submersible, or habitat. To maintain body heat, a continuous flow of 2.5 to 3.5 gallons per minute of 95 °F to 110°F (35 °C to 43 °C) water is required. This system originate on the surface dis- 5.4.3.2 Hot-Water Heater and Hoses The heater unit of these systems contains water pumps, a heat source, and controls that deliver hot water at a NOAA Diving Manual — October 1991 Diver and Diving Equipment Figure 5-14 Snorkels The heat source may use prescribed temperature. a diesel fuel flame, electric cal-rod heaters, live steam, The heat exchanger generfrom the heat source through an intermediate fresh water system to the diving water system. The intermediate system isolates the diving water system from temperature surges and reduces heater maintenance by controlling scaling and corroor a combination of these. ally transfers heat For operational convenience, the controls that sion. operate the heat source can be located remotely. Hot-water The hose. both a suits require bell bell hose and a diver's hose carries hot water from the heater to the bell, and the diver's hose carries hot water either from the heater or the 5.4.3.3 bell. Closed-Circuit Hot-Water Suits Closed-circuit hot-water suits consist of a dry suit and a special set of underwear; heated water is circulated through the underwear. Water is pumped from a heater, through a series of loops in the underwear, and back to the heat source. Hot water may Courtesy from a heater carried by the diver or from a surface heater. The primary advantages of closed-circuit hot- excessive biting force. Soft rubber models are availa- water systems are that they keep the diver dry and ble, retain their insulating ability for the hot-water source The major disadvantages movement and restricts the diver's more fails. some period of time if of type are that the special underwear severely suits of this TEKNA SCUBA originate either that these suits are fragile than the open-circuit system. and some have a swivel feature. Other models are bent to conform to the configuration of the diver's head or to have a flexible length of hose at the breathing end that allows the mouthpiece to drop away when not in use. Although widely distributed, snorkels with a sharp bend should not be used because they increase airway resistance. Those with shallow bends, such as 5.5 DIVER'S ACCESSORY EQUIPMENT the wraparound models, reduce this resistance to a minimum. Snorkels with corrugated flexible tubes, however, are difficult to clear of water and additionally cause air to move in turbulent flow, which increases There are numerous items of accessory equipment that have special uses and are valuable to a diver to accomplish underwater tasks. The following sections describe breathing resistance. Snorkels should have an opening several of these items. of the same size at the intake as at the mouthpiece; they should not have a divider in the mouthpiece, because the divider also will cause turbulent flow. 5.5.1 A Snorkels snorkel is Ideally, the inside a rubber or plastic breathing tube that allows a diver to swim comfortably on the surface diameter of the snorkel should be 5/8 to 3/4 inch (1.3 to 1.8 cm), and it should not be more than 15 inches (38.1 cm) in length. Longer snor- more without having to turn his or her head to the side to kels increase breathing resistance, are breathe. Snorkels allow scuba divers to survey the and cause additional drag when the diver is swimming under water. Snorkels flood when the diver submerges, but these devices can be cleared easily by exhaling forcefully through bottom in shallow water without having to carry a scuba tank. Snorkels are available in a wide variety of designs (Figure 5-14), and selection preference (Murphy 1980). is a matter of individual The most commonly used to clear, increase the tube. dead With some difficult air space, snorkels, especially those with flexible tubing near the mouthpiece, it is difficult to amounts of snorkel has three segments: a barrel that protrudes clear the snorkel completely, and small above the water, a mouthpiece tube, and a mouthpiece. water The mouthpiece should be tube. Snorkels of this type can be cleared easily selected to fit easily under the lips and should be capable of being held without October 1991 — NOAA Diving Manual may remain in the curve or corrugations of the when the diver surfaces. 5-19 Section 5 Figure 5-15 Dive Timer A ( Timing Devices 5.5.2 watch is bottom time, and assisting in underwater imperative for dives deeper than diver's watch must be self-winding, essential for determining controlling rate of ascent, navigation; is it 30 feet (9 m). A pressure- and water-proof (a screw-type sealing crown is recommended), and should have a heavily constructed case that is shock-resistant and non-magnetic. An external, counter-clockwise-rotating, self-locking bezel required for registering elapsed time. The band should be of one-piece construction and should be flexible enough to fit easily over the diver's arm. A flat, scratchis proof crystal and screw-down and lock stem also are recommended. Electronic (battery-powered) diving watches are now common, but divers should remember that batteries run down and that some of these watches are sensitive to external temperatures, which could affect their reliability during cold-water diving. Dive timers are miniature computers that use microprocessor chips to count the number of dives in a day, the current bottom time, and the current surface interval (Figure 5-15). after the last Some dive to timers also can count the hours let the user know when it is safe to fly. Models are available that can operate for as long as 5 years without battery replacement. Dive timers are activated automatically when « the diver descends to a depth below a certain depth (approximately 5 to 9 feet (1.5 to 2.7 m)). cally at a During ascent, timers stop automati- depth of about 3 to 5 feet (0.9 to 1.5 m). Courtesy TEKNA SCUBA As with other diving equipment, watches and timers must be handled with care and be washed in fresh water after they have been used An water. that it in salt or chlorinated important requirement for any dive timer have a high-contrast face to facilitate is reading Figure 5-16 Depth Gauges under poor-visibility conditions. 5.5.3 Depth Gauges Depth gauges (Figure 5-16) are small, portable, pressure-sensitive meters that are calibrated in feet and allow divers to determine their depth while submerged. Depth gauges are delicate instruments and must be treated carefully to avoid decalibration. Accuracy is extremely important and should be checked at regular intervals. Only a few models of depth gauges can be calibrated in the field; most models can be returned to the manufacturer if they need replacement parts. During evaluation and regular use, gauges should be checked to ensure that rough gears or internal corrosion does not cause the indicator hand to stick at par- 4 ticular depths. 5-20 Courtesy NOAA Diving Manual New England Divers, Inc. —October 1991 Diver and Diving Equipment Most commercially available depth gauges operate diaphragm, or bourdon tube either on the capillary, gauges consist of a plastic the water at one end and is attached principle. Capillary depth tube that is open to a display that to is calibrated in feet. As depth increases, and the the pocket of air trapped in the tube decreases depth read from the water level is in the tube. The diaphragm model has a sealed case, one side of which is a flexible diaphragm. As pressure increases, the diaphragm is distorted, which causes the needle to which it is linked to move. Bourdon tube depth gauges are the most fragile of these types of gauges; they require more frequent calibration than the other types. With bour- don tubes, water pressure causes a distortion of the tube, which in turn moves a needle that indicates depth. Both bourdon tube and diaphragm depth gauges are available in models that are sealed and oil-filled for 5.5.4 Wrist Compass Cylinders An underwater compass consists of a small magnetic compass that is housed in a waterproof and pressureproof case and is worn attached to a diver's wrist by a band. Compasses are useful for underwater navigation, especially in conditions of reduced visibility, and they are also helpful when divers are swimming back to a boat while submerged. Compasses do not provide precise bearings, but they do provide a convenient, reliable directional reference point. To limit magnetic interference, compasses should be worn on the opposite wrist from the diver's watch and depth gauge. Compass models are available that allow a diver to read them while holding them horizontally in front of them when swimming. Compasses do not have to be recalibrated, and the only maintenance they need is a fresh-water rinse after use. smooth, reliable operation. Combination depth gauges are also available; these generally consist of combinations of a conventional bourdon tube with a capillary gauge around the perimeter of the face. Capillary gauges generally give more accurate readings at shallower depths, and these gauges can also accuracy has been gauges at Pressure Gauges Two styles of pressure gauges can be used to determine the amount of air in a scuba tank. A surface 5.5.5 cylinder pressure gauge (Figure 5-1 7 A) is used to check damaged, the readings provided by the two amount of air in a tank on the surface. This type of gauge fits over the cylinder manifold outlet, attaches in the same manner as a regulator, and provides a shallow depths will differ significantly. one-time check of the pressure be used as a reference for measuring the of a bourdon tube gauge. If the bourdon tube Bourdon tube gauges tend to retain salt water in the tube, which may cause salt deposition or corrosion. To prevent this, the tube should be sucked free of water and the gauge should be stored in a jar of distilled water. Helium-filled depth gauges leak and lose accuracy if they are not kept completely submerged in water whenever they are exposed to high-pressure the release valve is installed in a tank. on the gauge so that A pressure- air trapped gauge after the valve on a tank has been secured can be released and the gauge removed. These small dial gauge movements are designed with an accuracy in the ± of 100 psi, but they may become less accurate with use. The submersible cylinder pressure gauge attaches directly to the first stage of a regulator by a length conditions. of high-pressure rubber hose; these gauges provide Depth gauges are delicate, finely tuned instruments and must be used, stored, and maintained with great care. They are an essential part of a diver's life-support equipment, and careless handling on the part of the diver could prove fatal. divers with a continual readout of their remaining Many air. units have a console that holds the compass, depth gauge, and tank pressure gauge (Figure 5-1 7B); these consoles free the diver's arms for other dive activities. Submersible pressure gauges are essential usually meas- pieces of diving equipment; most of these devices ured with a pneumofathometer, which is a pressure gauge located on the surface. To determine a diver's operate on the same principle as the bourdon tube. For surface-supplied divers, depth depth, air surface. is introduced into the The pneumo hose diver's umbilical the diver's end. is air pneumo hose is open end. When the hose is to the water at introduced at the surface dis- places the water in the hose and forces The gauge connected at the one of the members of a assembly and The is One end and and is is gauge is sealed move; the other end is held fixed of the submersible pressure allowed to connected air pressure to a high-pressure air supply. As the increases, the bourdon tube tends to straighten out or to uncurl slightly. The gauge's dial out the diver's face should be easy to read and should have high-contrast clear of water, excess air escapes. markings. Although gauges currently in use are designed to the it hose on the surface indi- to be accurate and reliable, they are not precision cates the pressure (in feet or meters of seawater equiv- laboratory instruments. Divers should not expect accu- alent) required to clear the hose of water. racies better than October 1991 — NOAA Diving Manual ± 250 psig at the upper end of 5-21 Section 5 Figure 5-17 Pressure Gauges A. Cylinder Underwater Slates A slate may be a useful Gauge 5.5.6 piece of equipment when underwater observations are to be recorded or when divers need a means of communication beyond hand signals. A simple and useful slate can be constructed from a 1/8- or 1/4-inch acrylic plastic that has both sides; these slates (0.3 to 0.6 cm) thick piece of been lightly sand-papered on can be used with an ordinary pencil. Semimatte board or (0.01 cm) plastic sheets can be placed on a clip a ring binder. These sheets (about 1/32-inch in thick) may 10 feet (1.8 to 3.0 m). be purchased up to 6 x as needed, and no in sizes They may be cut is required. Ordinary lead pencils can be used, and marks can be erased or wiped off with a rubber eraser or an abrasive cleanser. Some underwater slates are equipped with a compass, depth gauge, and watch sanding Courtesy Dacor Corporation B. that are Submersible Cylinder Pressure Gauge mounted across the When top. slates are used, they should be attached to the diver with a loop or lanyard made them from being of sturdy line to keep lost. 5.5.7 Diving Lights A waterproof, pressure-proof diving light is an impor- equipment when divers are operating in areas of restricted visibility. Lights are used most frequently for photography, night diving, cave diving, wreck diving, exploring holes and crevices, or diving under ice. Regardless of the power of an underwater light, it will have only limited value in murky, dirty tant item of waters where When visibility is restricted consider, such as brightness Courtesy TEKNA SCUBA by suspended matter. selecting a light, there are several factors to and beam coverage, type of batteries (disposable or rechargeable), size and shape, burn time, and storage time (Figure 5-18) (Cozens 1981b). Most the gauge range and between 500 and ± 100 psig at the lower end psig (Cozens 1981a). divers prefer the light to have a neutral or slightly positive buoyancy because As with NOTE Submersible pressure gauges are recommended for all divers and all dives. The only maintenance gauge needs is that a submersible pressure a fresh-water rinse after use. To pre- vent internal deterioration and corrosion of a surface gauge, care must be taken to ensure that the plastic plug that covers the high-pressure inlet is firmly in place. Submersible pressure gauges should be handled with care and should be stored securely use. 5-22 it is easy to add a small weight to keep the light on the bottom, when not in all if necessary. other pieces of diving equipment, lights should be washed with fresh water after every use. The 0-ring should be lubricated with a silicone grease and should be checked for debris every time the light assembled. When is not in use, the batteries should be removed and stored separately. Before a diving light is used, it should be checked thoroughly to ensure proper operation. The batteries should be replaced any time they show any signs of running low, and spare light bulbs and batteries should be available at the dive site: 5.5.8 Signal Devices Signal devices are an important but frequently ignored item of diving safety equipment for divers. They are NOAA Diving Manual —October 1991 Diver and Diving Equipment Figure 5-19 Signal Devices Figure 5-18 Diving Lights A. Diver's Pinger Courtesy Battelle-Columbus Laboratories particularly valuable when a diver surfaces at a great B. Diver's Flasher distance from the support platform or surfaces prematurely because of an emergency. Several types of sig- naling devices are available (Figure 5-19). Whistles are valuable for signaling other swimmers on the surface. For easy accessibility, they may be attached to the oral inflation tube of the buoyancy by a short length of rubber strap. vest (MK-13, Mod 0, Signal Disand Day Night) can be carried taped to the diver's belt or knife scabbard. One end of the flare contains a day signal, a heavy red smoke, while the The military-type flare tress, opposite end holds a night signal, a red flare. Both ends are activated via a pull ring. After either end of the signal has been pulled, the flare should be held at arm's away from the The diver's body length, with the activated end pointed diver at an angle of about 45 degrees. should be positioned upwind of the signal. does not ignite immediately, waving may onds will if work assist ignition. after If the flare for a it few sec- After activation, the flare submergence, although it will not ignite activated under water. After every dive, the flare should be flushed with fresh water and should then be checked for damage Courtesy Dacor Corporation of 1500 feet (457.2 m). These lights are waterproof and can operate submerged at depths up to 200 fsw (61 m), depending on the make and model. Some rescue lights have an operational life of as much as 9 hours; the operational or deterioration. by using the Some NOTE of these units can be extended greatly light only intermittently. divers use chemical light tubes; these small tubes contain two separated chemicals. is Red life flares and smoke signals should be used only as distress signals or to signal the termination of a dive. bent, the chemicals discharge soft When the tube and mix, causing green light that glows for several hours. divers attach these tubes to their scuba cylinders, straps, or snorkels as a Some mask an aid to tracking their buddies, while others carry them as an emergency light source. Signal devices should be carried so that they are At night, divers can carry a flashing rescue light that attached to their belt, harness, or arm. Rescue lights of this type are compact, high-intensity, flashing strobe is lights that are generally visible for (16 to 24 km) from October 1991 1 to 15 miles a search aircraft flying at an altitude — NOAA Diving Manual and will not be lost when equipment is Buoyancy compensators frequently have a ring that will accommodate a whistle or strobe easily accessible discarded. built-in light, and flares are often taped to the scabbard of the diver's knife with friction tape. 5-23 Section 5 5.5.9 Safety Lines equalization of pressure. Diver safety lines should be used whenever divers are operating under hazardous conditions; examples of The increase in pressure inside the goggles as depth increases during the dive may ice, or cause the rim of the goggles to cut deeply into the face or the eyes to be forced against the glass plates; either diving in strong currents. Diver-to-diver lines should of these events can cause severe and painful tissue or be used when the working conditions of the dive could separate the divers who are working under water. Safety eye squeeze. such situations are cave diving, working under Regulator neckstraps should also not be worn because lines provide divers these straps are difficult or impossible to remove in an limited) emergency. Some single-hose regulators come equipped with these straps as standard equipment; the straps should be removed and discarded before diving. with a quick and effective (although means of communications. Under special condia surface float can be added to the line to aid tions, support personnel in tracking the diver. The most commonly used types of safety nylon, dacron, or polypropylene. These materials are strong, have nearly neutral or slightly positive buoy- ancy, and are corrosion resistant. into A snap can be spliced each end of these lines to facilitate easy attach- ment to a float or to a diver's weight belt. Maintenance of safety lines requires only that they be inspected and that their snaps be lubricated. Reels and lines used in cave diving must be dependable; these lines require additional maintenance and careful inspection. Any In addition to the specific items mentioned above, line are safety line should be replaced if it shows signs of weakness or abrasion. any equipment that not necessary for the particular is dive should be considered hazardous because extra equipment increases a gear should be 5.6 left diver's chances of fouling. Excess on the surface. SHARK DEFENSE DEVICES In areas where sharks are frequent, many divers carry some form of shark defense. Several types of devices are available and have been shown to be effective. These devices are designed to be used only as defense mechanisms; they are not effective and should not be used as offensive weapons. 5.5.10 Floats A float carrying the diver's flag should time a diver is is The a wooden club that is counter-weighted to facilitate underwater use and is be used any operating from a beach or in an area that frequented by small boats. Floats also provide the oldest anti-shark device commonly is called a "shark billy." It is used to fend off Shark dive master with quick and accurate information about or to strike a shark, preferably on the nose. the diver's location and provide the diver with a point size made from 3/4-inch (1.8 cm) round fiberglass stock and are 4 feet (1.2 m) long. A hole is drilled in one end to accommodate a lanyard and a loop of flag positioned at the top of a staff; bright colors and the other end is ground to a point and coated with fiberglass resin. Instruments of this length and diameter can be moved through the water quickly because they afford little drag under water. buoyancy in an emergency. Floats range in and complexity from a buoy and flag to small rafts; the type most frequently used is an automobile innertube whose center portion is lined with net. Float should be brightly colored and should carry a diver's of positive make billies surgical tubing, the raft noticeable, and the flag tells boaters that a diver is 5.5.11 in the water. Accessories That Are Not Recommended Several pieces of equipment are sold commercially are If a shark is circling a diver, the diver should use the prod the shark; the butt end should be kept against the diver's body and the sharp end should be used against the shark. This defense should discourage billy to the shark from coming closer than about 4 feet (1.2 m) from the diver. Sharks that have been prodded leave the immediate area hastily (although they return to but should not be used because they can cause injury to the area almost immediately). Although brief, the shark's the diver or convert a routine situation into an emer- retreat usually provides sufficient time for the diver to gency. Earplugs should never be used while diving; leave the water (Heine 1985). they create a seal at the outer ear, which prevents pressure equalization and can lead to serious ear squeeze, shark, a power head can be used. These devices, ruptured eardrum, and, possibly, total loss of hearing monly called "bang sticks," consist of the plug is forced deeply into the ear cavity). Goggles also should not be used in diving because they do not cover the nose and thus do not permit chamber designed to accommodate a powershotgun shell. The chamber is attached to the end of a pole and is shot or pushed (if 5-24 If a diver wishes to kill rather than discourage a com- a specially constructed ful pistol cartridge or NOAA Diving Manual — October 1991 Diver and Diving Equipment Figure 5-20 Shark Darts against the shark, where power heads have it on impact. Although fires a built-in positive safety, they should be handled with extreme caution; they also should not be carried also is in water with poor dangerous to carry visibility or at night. It loaded power heads when several divers are working closely together in the water. Devices known as "shark darts" are available commercially; these instruments are designed to disable or sharks by injecting a burst of compressed gas. Shark darts consist of a hollow stainless steel needle approximately 5 inches (12.5 cm) long that is connected to a small carbon dioxide (C0 2 ) cylinder or extra scuba tank; they are available in dagger or spear kill form (see Figure 5-20). To use these devices, the dart is abdominal cavity, where it penetrates into the animal's body cavity and discharges the contents of the C0 2 cartridge. The expanding gas creates a nearly instantaneous embolism and forces the shark toward the surface. The size of the C0 2 Photo William High thrust against the shark's Figure 5-21 Shark Screen in Use cylinder varies from model to model; a 12-gm cylinder is effective to a depth of 25 feet (8 m), a 16-gm cylin- der to 40 feet (13 m), and a 26-gm cylinder to 100 feet (30 m). Multiple-shot compressed-air models are also available. NOTE some it is illegal to carry comweapons such as shark darts in automobiles or on the person. Divers are In localities, pressed-air check with therefore advised to ties local authori- before carrying these devices. One of the most effective methods of protecting divers in shark-infested waters the Shark Screen, a is Photo Scott Johnson lightweight synthetic bag that has three inflatable collars (Figure 5-21). In the water, the diver the collars, gets into the bag, and blows up with seawater; fills it intelligibility of messages transmitted through any type the bag then conceals the occupant from the sea below of diver and keeps any effusions blood or sweat) that a result of the effects of pressure, interference from When the might attract sharks bag is in (e.g., the bag. not in use, the folded into a small package and carried in a life vest or kept with other survival gear. UNDERWATER COMMUNICATION SYSTEMS is less than optimal as support system, and the need for a diver to life concentrate on behaviors other than communication. Message intelligibility improves significantly, howevand listeners in the underwater environment (Hollien and Rothman er, if 5.7 communication system divers are trained to be better talkers 1976). The four principal types of diver communica- tion systems are described in the following sections. Several underwater communication systems have been developed and are available commercially. These sys- Hardwire Systems because of their inherent deficiencies and use constraints. Studies have shown 5.7.1 that, regardless of the efficiency of these systems, the parable to a telephone tems vary in effectiveness October 1991 — NOAA Diving Manual Hardwire systems employ a closed loop that is comand includes a microphone, an 5-25 Section 5 Figure 5-22 Diver Communication earphone/receiver, and a cable over which the signal System \ is transmitted. These units require a physical connection, i.e., umbilical, between the talker Hardwire systems of the type used and the listener. for surface-supplied or scuba diver communication provide the greatest degree communication of the systems discussed shows the surface control panel of a hardwire diver communication system. Most hardwire systems can be configured either for two-wire or four-wire operation. In a two-wire system, the diver usually is the priority signal path and of intelligible here. Figure 5-22 Photo Michael Pelissier, Ocean Technology Systems the tender listens to the diver. If the tender wishes to must be thrown. The earphone and microphone on the diver's end are wired in parallel (Figure 5-23A). When two divers are operating talk to the diver, a switch on the same radio, the tender must push a cross-talk switch to enable the divers to talk to each other. Figure 5-23 Schematics of Diver Communication Systems A. Two-Wire Mode A four-wire system (Figure 5-23B) allows the tender and divers to participate in open-line (round robin) munication, similar to that in a com- conference telephone call. Most hardwire units are powered by internal 6- or 12-volt lantern-type batteries that provide continu- ous operation on moderate volume output for 25 hours or more. Some units feature connections for an exter- ( power supply; others incorporate redundant batteries so that a spare is always available in an emergency. nal 5.7.2 P^ Acoustic Systems The acoustic system includes fier, power supply, and directly into the water a microphone, ampli- transducer; it 5^f &_ transduces speech by means of the projector (under- B. Four-Wire Mode water loudspeaker). The signal produced can be received either by a hydrophone placed in the water or by divers without any special receiving equipment. Some of these systems also incorporate alarms or signals that can be used to recall divers. 5.7.3 Modulated Acoustic Systems Several units of the modulated acoustic type have been manufactured, and these have performance characteristics that vary from poor to excellent. The most widely used modulated acoustic systems employ ampli- tude modulation (AM), a technique also used by commercial AM broadcast stations. However, since radio signals are absorbed rapidly by seawater, the acoustic carrier rather than the radio frequency carrier ulated in diving situations. A is mod- typical system of this MICROPHONE type consists of a microphone, power supply, amplifier, i modulator, and underwater transducer (Figure 5-24). Acoustic signals produced by such systems can be 5-26 Courtesy Michael NOAA Pelissier, Ocean Technology Systems Diving Manual — October 1991 Diver and Diving Equipment Figure 5-24 Modulated Acoustic Communication System few result, FM systems adapted to underwater use are commercially available. Single sideband has an advantage over AM AM, because puts one-half of the total output power and carrier, this power is ultimately lost. AM nicators have greater range than the in SSB commu- systems for the same output power and frequency. A major drawback to SSB is that it requires more complicated electronics and higher initial cost than other systems, and, as a result, most presently used underwater communication systems Poor utilize the AM intelligibility has technique. been a problem for many users of wireless diver communications. In the late 1960's, researchers at the University of Florida sponsored a series of tests designed to elucidate this problem. Photo Michael Pelissier. Ocean Technology Systems During the tests, divers read phonetically balanced word lists using various masks, microphones, and communicators; test results showed intelligibility scores understood only by a diver or a topside listener equipped with an appropriate receiver and demodulator. In one such unit, for example, a 31.5-kHz carrier signal modulated by the speech into the signal er, is signal, amplified, is and projected water via an acoustic transducer. The acoustic the 50 percent range at best. now known that in many human and equipment factors contribute to an increase in The key elements are the microphone, intelligibility. mask, earphone, transmitter/speech filter design, and diver training. then picked up by another acoustic transduc- amplified, demodulated, and heard in the normal 5.7.4 communicator 1/2 watt. Generally, a range of 1/4 mile (0.4 km) can be expected in good ocean conditions. However, range and clarity can change dramatically because of acoustic background noise, a shadow effect (caused by the tank, buoyancy compensator, wet suit, etc.), or thermoclines. is Non-acoustic Wireless Systems Another approach speech mode. The power output of a typical 31.5-kHz to underwater communication involves a non-acoustic wireless system that uses an electric current field. system made is Because barriers, or reverberation. by the amount of power applied diver "feels" a mild shock communication. Generally, the higher the frequency, the greater the absorption of sound in water. October 1991 — NOAA Diving Manual As a Range is man- determined to the field platers and limited to the diver's height, and power output tems generally require a high ultrasonic frequency to non-acoustic, this by the separation between them. Separation generally is obtain the frequency deviation necessary for intelligi- is it not affected by thermoclines, natural or Other modulated acoustic systems involve frequency modulation (FM) or single sideband (SSB). FM sys- ble It is is limited by what the diver can tolerate because the mode is when transmitting. This limited, at best, to a range of a few feet or meters. With modification, this hundred system can be used to transmit physiological data. 5-27 i Page SECTION 6 HYPERBARIC 6.0 General 6-1 6.1 Hyperbaric Chambers 6-1 CHAMBERS AND SUPPORT 6.2 Design and Certification 6-3 EQUIPMENT 6.3 Operation 6-3 6. 1 .1 Transportable Chambers 6.3.1 Predive Checklist 6.3.2 Gas Supply 6.3.3 Chamber Ventilation and Mask Breathing System Oxygen Analyzers 6.3.4 6.3.5 6-2 6-3 6-3 Calculation of Gas Supply 6-6 6-7 6-8 6-9 6.4 System Chamber Maintenance 6.5 Fire Prevention 6-10 6.5.1 Ignition 6-10 6.5.2 Combustion 6-14 6.5.3 Materials 6.5.4 Management 6.3.6 6.5.5 Electrical 6-9 6-14 of a Fire 6-14 6.5.4.1 Detection 6-17 6.5.4.2 Extinguishment 6-17 6.5.4.3 Breathing Masks and Escape 6-17 Summary of Fire Protection Procedures 6-17 « HYPERBARIC CHAMBERS AND SUPPORT EQUIPMENT 6.0 GENERAL three terms generally describe 'chambers used prima- Hyperbaric chambers were developed human to permit beings to be subjected to an increased pressure environment. Such chambers are vessels capable of accommodating one or pressurized so that the more occupants and of being environment inside the chamber rily treatment of pressure-related fects of pressure, in the refer to these as PVHO's 6.1 Early models of hyperbaric chambers were single- compartment does not diving: surface decompression; Human HYPERBARIC CHAMBERS example, hyperbaric chambers are used in (Pressure Vessels for Occupancy). patient uations that occur is decompression of divers). Engineers conditions, and in the decompression of divers. For in several sit- and decompression cham- for the surface simulates water depth while the pressure outside the chamber remains at normal (l atmosphere) pressure. Hyperbaric chambers are used in research on the ef- to treat diving casualties), bers (a term used to indicate that their primary use (single-lock) and a tender chambers to enter recommend that allowed one and be pressurized. NOAA the use of single-lock chambers because they do not allow medical and tending person- have access omitted decompression; treatment of diving accidents nel to such as gas embolism and decompression sickness; and modern chambers are of the multilock type (see Figure 6-1). The multilock chamber has two or more com- pressure and oxygen tolerance tests. changeably to Terms used inter- denote these chambers include recom- pression, compression, or hyperbaric chambers (these to the patient during treatment. All partments that are capable of being pressurized in- dependently; this feature allows medical personnel and Figure 6-1A Double-Lock Hyperbaric Chamber— Exterior View Oxygen Lifting Eye Gas Nitrox Regulator Inert (Therapy Gas) Regulator Inner Lock Analyzer Gauge j Communications / Outer Lock y Gauge Outer Lock Viewport Viewport C0 2 Scrubber Controls Design and Cert. Plate 2 Overboard Exhaust E.K.G. Air Oxygen and Therapy Gas Cylinders October 1991 — NOAA Diving Manual Exhaust Photo Dick Rutkowski 6-1 Section 6 Figure 6- 1B Double-Lock Hyperbaric Chamber— Interior View Emergency nterior Light Air/Therapy Gas Mask Photo Dick Rutkowski tenders to enter the chamber to treat the patient and Multiplace chambers are designed to accommodate same time. Deck decompreschambers (located on the deck of the surface platform or support ship) and land-based chambers then to leave, while the patient remains at the desired several occupants at the pressure in the inner compartment. sion A chamber • • A should be equipped with the following: two-way communication system A mask the breathing system for oxygen (normally of demand used for recompression treatment and diving research and research are or for clinical hyperbaric treatment examples of multiplace chambers. type, although ventilation hoods are gaining acceptance for clinical treatment) (Figure 6-2) • Emergency air/mixed gas breathing masks 6.1.1 Transportable Chambers and shape • Pressurization and exhaust systems • A • External lighting that illuminates the interior lightweight materials (Figure 6-3) to L-shaped, two- • Viewports person capsules, have been used • Depth control gauges and control manifolds Heating and air conditioning systems (highly fire extinguishing system Small portable chambers, varying in size from single-person, folding chambers made from modern in emergencies to • Stop watches (elapsed time with hour, minute, and second hands) recompress divers being transported to a large wellequipped chamber. Transportable chambers are most valuable when they are of the two-person type and are capable of being mated to a larger chamber, because these features allow the patient to be continuously • Gas sampling tended and pressurized. Small one-person transportable • desirable) 6-2 ports. NOAA Diving Manual — October 1991 Hyperbaric Chambers and Support Equipment Figure 6-2 Mask Breathing System for Use in Hyperbaric Chamber and ancillary equipment should quality pressure gauges C0 2 chamber. All such equipment should be tested and calibrated before a diving operation. Figure 6-4 is an example of a certification plate and shows various specifications and be used Scrubber Motor Viewport Sound Powered Phone in outfitting a hyperbaric certifications. NOTE structural modifications such as those made, the chamber must be recertified before further If involving welding or drilling are use. Hyperbaric chambers used diving usually are cylin- in drical steel pressure vessels that are designed to with- stand an internal working pressure of at least 6 atmo- (ATA) (165 spheres absolute Modern chambers fsw). generally are 54-60 inches (137-152 centimeters) in may have inside diameter but Oxygen Exhaust inside diameters ranging from 30 inches (76 centimeters) to as large as 10 feet (3 meters). Large chambers used to house and decompress divers for long saturation exposures are outfitted with toilet fortable facilities, beds, and showers, but such chambers usually are found only at sites comwhere large-scale diving operations or experimental dives are conducted. C0 2 Scrubber Canister Photo Dick Rutkowski 6.3 OPERATION 6.3.1 chambers, although better than no recompression A Predive Checklist predive check of each chamber must be conducted have major shortcomings because an attendant outside the chamber has no way to perform lifesaving measures, such as maintaining an airway, gas source must be checked to see that the intake performing cardiopulmonary resuscitation, or ing a pneumothorax. The predive checklist (see Table 6-1) should be posted on the chamber itself or on a clipboard next to the capability at all, reliev- before operation. If pressurized by a compressor, the is clean and will not pick up exhaust from toxic sources. chamber. 6.2 DESIGN AND CERTIFICATION Gas Supply A chamber treatment 6.3.2 Several codes and standards apply to man-rated pres- sure vessels, including current standards set by the American National Standards Institute, the American Society of Mechanical Engineers, the National Fire Protection Association, and, under certain circumstances, the U.S. Coast Guard. These codes are comprehensive where the structural integrity of the vessel is concerned and include tion, all aspects of material selec- welding, penetrations into the pressure vessel walls, flanges for entry or exit, October 1991 — NOAA and testing. Diving Manual Only high- and a secondary air facility should have a primary supply that will satisfy the follow- ing requirements: Primary supply — sufficient air to pressurize the cham- ber twice to 165 fsw and to ventilate Secondary supply throughout the treatment: — sufficient air to pressurize the 165 fsw and to chamber once to ventilate for hour. l 6-3 Section 6 Figure 6-3 Transportable Chambers A. Total system B. Courtesy Draegerwerk C. Lightweight one-person transportable Schematic showing victim and tender AG chamber Courtesy Draegerwerk AG Technical Data: Max. operating pressure: Test pressure: 5 bar 72.5 pounds/sq. in. 7.5 bar 108.75 pounds/sq. in. 42,714 Total volume: 700 liters Total outside length: 2540 mm Total outside height: 1520 mm Total outside width: 860 mm Outside height (without mobile base): 1200 mm Total inside length: 2350 mm Largest inside diameter: 640 mm Total weight: approx. 500 kp Weight of the complete base: approx. 275 kp Weight of the complete pressure chamber without base: approx. 225 kp Acceptance: Techn. Inspect. Agency (TUV) cu. •100.00 in. 59.84 in. 33.86 in. • • 47.24 in. • 92.52 in. 25.20 in. • in. 1102.5 pounds 606.4 pounds 496.1 pounds Photo Butch Hendrick Figure 6-4 Certification Plate for Hyperbaric Maximum Working Chamber Maximum Working Temperature Pressure. Manufacturer's Serial ASME Stamp Number (Chamber manufactured in accordance with ASME Code) for, Unfired Pressure Vessel Division of Code (Manufactured according to Section 8, Division 1). Arc or Gas Welded Construction. 77 PSI 150°F Uj DIV W SERIAL NO 1973 I ^.Year of Construction .U.S. Coast Guard Stamp: Class designates either Working Pressure between 30 and 600 psi or working temperature between 275° and 700 °F II « b USCG CLASS MIA 73 25 DESIGNED AND BUILT BY PERRY SUBMARINE BUILDERS RIVIERA BEACH, FLORIDA Coast Guard Office Marine Inspection U.S. MIA Manufacturer 73 25 in charge of — Miami Office — Year of inspection — Sequential number of inspection (e.g., 25th chamber inspected in I 1973) Source: 6-4 NOAA Diving Manual NOAA (1979) — October 1991 . Hyperbaric Chambers and Support Equipment Table 6-1 Hyperbaric Chamber Predive Checkout Procedures Before every operation of the chamber, a predive check of ELECTRICAL SYSTEM the facility must be conducted. This procedure should take Lights operational only a few minutes, provided that the personnel are experienced Wiring approved, properly grounded and the chamber is Monitoring equipment properly maintained. calibrated (if applicable) and operational. Predive Checklist COMMUNICATION SYSTEM CHAMBER Primary system operational Secondary system operational. Clean Free of extraneous equipment all Free of noxious odors FIRE PREVENTION SYSTEM Doors and seals undamaged, seals lubricated Water and appropriate fire extinguisher in chamber. For chambers with installed fire suppression system, Pressure gauges calibrated, compared. pressure on tank AIR SUPPLY SYSTEM Primary air Combustible material supply adequate for 165 feet plus ventilation Secondary air supply adequate two pressurizations to Fire-resistant for MISCELLANEOUS — INSIDE CHAMBER Slate, chalk, Equalization valve closed at Bucket and 350 psig or 250 psig, depending and mallet bags plastic Primary medical on working pressure (200 or 100 psi) of chamber Fittings tight, filters clean, compressors fueled. for body waste kit Ear protection sound attenuators/aural protectors (one pair per occupant) OXYGEN SUPPLY SYSTEM MISCELLANEOUS— OUTSIDE CHAMBER marked as BREATHING OXYGEN; cylinder valves open Replacement cylinders on hand Inhalators installed and functioning Regulator set between 75 and 100 psig Fittings tight, gauges calibrated Oxygen manifold valves closed. Cylinders metal enclosure worn by all chamber occupants mattress and blankets in chamber. one pressurization and 1 hour of ventilation Supply valve closed Supply regulator set in Fire-resistant clothing Stopwatches Recompression treatment time full; Decompression time-personnel leaving chamber Cumulative time Spare U.S. U.S. Navy recompression treatment tables Navy decompression tables Log List of emergency procedures Secondary medical kit NITROX (Therapy Gas) marked 60% N 2 /40% 2 cylinder valves open Replacement cylinders on hand Inhalators installed and functioning Regulator set between 75 and 100 psig Fittings tight, gauges calibrated Cylinders NITROX full; ; Oxygen analyzers CLOSED-CIRCUIT OPERATIONS (WHEN APPLICABLE) C0 2 C0 2 Both the primary and secondary supply may be pro- vided by any combination of stored and compressor at the If amounts of air appropriate pressure in the required times. it is is important to power failures and, wherever possible, to keep an emergency generator available to provide continuous power if service is interrupted. Personnel at chamber installations should be familiar with local fire and rescue units that can provide emergency power and air. — NOAA a card in a conspicuous place showing the date of service and type of lubricant used. Before activating a hyperbaric chamber, the opera- must ensure that the predive checklist shown Table 6-1 in has been completed. WARNING be aware of the possibility of October 1991 absorbent may be used. In addition to having an adequate volume of it C0 2 analyzer functional. The compressor should have tor not feasible to have a high-pressure system available as a backup, two low-pressure systems stored gas, scrubber functional Adequate valves closed. capacities that will provide the required functioning and calibrated. Diving Manual Compressors Should Be Lubricated With Lubricants That Will Not Break Down Under Heat or High Pressure, and Filters Should Be Changed According to Required Maintenance Procedures 6-5 Section 6 6.3.3 Chamber and Calculation Ventilation minimum Unless the chamber equipped with a scrubber, it is necessary to ventilate the chamber with fresh air to maintain safe levels of carbon dioxide and oxygen inside the chamber. The The chamber of Gas Supply is rate at which must be circulated air through the chamber depends on the number of personnel inside the chamber, their level of activity, the chamber depth, and the breathing gas being used. chamber supply should be maintained at a air supply pressure of 100 psig over pressure. Regulator settings for maximum oxygen depend on the type of oxygen breathing masks installed in the chamber; most masks should be supplied with gas at between 75 and 100 psig above the chamber pressure. Knowing the amount of air that 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 fractions of a NOTE turn), which provides a certain number of actual cubic minute at a specific chamber feet of ventilation per The abbreviation acfm refers to actual cubic at the chamber pressure in use at the time; scfm refers to standard cubic feet per minute and to use the air supply valve to maintain a chamber pressure during the ventilation period. pressure, constant • feet per minute, defined as cubic feet per minute at standard conditions at one atmo- The exhaust valve handle should be marked so that sphere pressure and 0° C [acfm = (scfm)/ (chamber pressure in atmospheres absolute, usually expressed as (D + 33)/33), where D = chamber depth in fsw]. the • is it number The possible to determine accurately of turns and fractions of turns. rules in this paragraph should be checked against probable situations to determine the rates of ventilation at various depths (chamber pressures) that are likely to be needed. If the air supply The following procedures reflect various scenarios in chamber operations: encountered (1) When (b) (2) occupants are breathing acfm 4 acfm 2 (a) air in the for each person at for each person not chamber: vide at least that rest at rest. (b) occupants are breathing oxygen by mask chamber without an overboard dump system: 12.5 acfm for each person at rest 25.0 acfm for each person not at rest (c) Additional ventilation a (a) is not necessary for much flow at a deeper depth. • The necessary valve • and depths should be determined with the help of a stopwatch by using the chamber itself as a measuring vessel. The ventilation rate can be calculated by using When in is ample, determination of ventilation rates for a few depths (30, 60, 100, 165 fsw) may be sufficient, because the valve opening specified for a given rate of flow at one depth normally will prosettings for the selected flows this formula: occupants who are not breathing oxygen. (3) Interrupted ventilation: (a) Should not exceed 5 V X R = minutes during any (P 30-minute period. t (b) When acfm (4) oxygen monitoring equipment is where available: Ventilation should be used as required to (a) maintain oxygen concentration in the chamber below 23 percent. (5) With an The installed overboard Step 1 The quantity is system: R chamber V volume of chamber t = ventilation rates for air breathing given (a) in dump 33 and then the normal rate should be resumed. When 33) X resumed, should use twice the required for twice the period of interruption, + 18 above should be used. of air ventilated through the = in cubic feet; time for chamber pressure to change 10 fsw P ventilation rate in acfm; in seconds; chamber pressure (gauge) in fsw. chamber controlled by regulating the precalibrated exhaust valve outside the chamber. been established, the to maintain a constant 6-6 air Once the exhaust rate has supply valve can be regulated chamber pressure. Chamber pressure in the unoccupied be increased to 5 fsw beyond the depth chamber should in question. The exhaust valve should then be opened a certain amount NOAA Diving Manual — October 1991 Hyperbaric Chambers and Support Equipment and the length of time below this maximum it takes to come up example, if checking for a depth of 165 fsw, the chamber pressure should be taken to 170 fsw and the time The it takes to reach The exhaust intake must be placed 10 fsw to depth should be determined. (For 160 fsw should be measured.) cham- maximum ensure chamber and from being drawn from the cham- circulation within the to prevent fresh air ber during ventilations. valve should be opened different degrees until the setting that approximates the desired time known; is Times that setting should then be written down. tings determined for these in the A same way. or table of the valve settings should be ventilation chart using this information chart made and and the a venti- The oxygen system provides oxygen chamber not equipped with a mask overboard discharge system and assuming there are two patients and one tender in the chamber) (for a Cp = 10V + 48,502 where It also provides a source of known clean chamber. The Smoking leaks. A in the vicinity hyperbaric chamber of a chamber is prohibited. may be equipped with both standard and overboard discharge breathing masks. regulator for oxygen or air supply, appropriate hoses Cp total V chamber volume 10 atmospheres needed = (ft to 3 ); to pressurize twice 165 fsw; treatment using USN dump 4. Table 6-2 shows ventilation rates and total air requirements for two patients and one attendant (US Navy fittings to exhaust the diver's exhaled breath outside the recompression chamber; overboard during Treatment Table undergoing recompression treatment and priate hoses total air (in scf) required to ventilate a and fittings, and an in-board dump (or discharge) system (see Figure 6-2). A breathing mask with an overboard discharge system consists of the same basic components as the standard mask, with the addition of a mask-mounted demand exhaust regulator and appro- capacity of primary system (scf); from the surface 1985). As indicated, the maximum air flow rate that the system must deliver is 70.4 scfm (with an oxygen stop at systems are usually used for oxygen breathing. The oxygen cylinder pressure is reduced mately 75 psig over chamber pressure by regulator. This pressure differential chamber depth. The demand calculate secondary system capacity, the formula = 5V + to by changes resulting low-pressure in oxygen or through a lightweight, flexible hose to a demand A control knob on the regulator allows adjustment of the regulator minimize breathing resistance or may 4,224 a to permit constant is flow, Cs a pressure maintained by tion of a standard regulator as required regulator located on the mask. Secondary System Capacity is to approxi- suitable tracking regulator or by operator manipula- air flows 60 fsw). To pure oxygen. air in the event of fouling of the air in the The standard mask is generally used with air but can be used with mixed gas or treatment gas. Overboard discharge masks are generally used for oxygen breathing during recompression or treatments. The standard breathing mask consists of an oral-nasal mask, demand calculated as follows: 48,502 for that part of the decompression/recompression schedule requiring system should be inspected carefully and checked for lation rates should be prepared. Primary system capacity Mask Breathing System 6.3.4 for other rates and depths should be calculated and set- is inside the ber as far away from the supply inlet as practical to if this is desired. The gas delivery pressure also be adjusted from outside the chamber to enhance flow characteristics. where With the overboard discharge units, the diver's exhalais removed through a regulator that is mounted on the side of the mask. The regulator exhaust is connected by a hose to the outside of the chamber. For a tion Cs = total V = chamber volume 5 = capacity of secondary system (scf); 3 pressure differential (ft ); atmospheres required to pressurize from chamber the surface to 165 feet once; = maximum for October 1991 1 ventilation rate of 70.5 hour. — NOAA scfm mask-mounted regulator. The unit should not be pressurized to a depth greater than 60 fsw unless it Diving Manual excess of 60 fsw, an auxiliary wall to limit the differential pressure at the outlet of the 4,224 in regulator must be connected between the hose and the is fitted with an auxiliary vacuum regulator or the 6-7 Section 6 Table 6-2 and Total Requirements for Two Patients and One Tender Undergoing Recompression Treatment Ventilation Rates Air Depth Ventilat on Rate (scfm) of Ventilation Air Required at Stop Using (scf) ' Stop Air °2 (fsw) Stop Stop 165 47.9 140 41.9 5 37 100 32.2 80 27.3 60 50 22.5 70.4 20.1 62.9 40 30 20 17.7 55.3 15.3 47.7 12.8 40.2 10 10.4 32.6 air 2929 4561 1772 1107 1772 1772 6183 6183 1090 1090 1090 966 328 675 603 530 916 770 1250 6898 13606 15182 6038 requirements are dependent on chamber Depth of 4561 4 3 1437 503 444 386 328 675 603 530 139 Total for Ventilation Total 2A 1A 1437 120 NOTE: 6A 6 2 from 60' Treatment Table 1540 2501 1437 503 444 386 328 675 603 530 10996 1540 1250 10778 18692 1831 4 5749 1256 5749 1256 1111 1111 966 966 821 821 8104 7234 6363 10996 1540 1250 25344 22644 19908 34344 7236 5868 45390 125247 size. Stop A Duration 60' 4 Hr. 4 Hr. Air 4 Hr. 60' 4 Hr. Air to 4 Hr. 5,400 16,903 2 3,672 14,430 2 2 Hr. Air 30' 2 Hr. Air to 4 Hr. 10' 4 Hr. Air 10' 4 Hr. Required 16,903 2 30' r 1,922 1,776 10,012 2 2,726 6,262 2 624 2 Hr. Air to 4' at 4' 2 Hr. Air 2 Hr. 4' 499 1,563 2 26 82,718 (min) 4 Min. to Surface Adapted from US Navy (1985) discharge hose has been disconnected from the exter- the manufacturer. For further information, consult the nal port. appropriate manufacturer's instruction manual (see These units should be inspected by the inside tender or supervisor before each use. Hose fittings should be inserted into properly labeled connectors on the wall of the chamber. After testing, the internal and external valves should be closed until mask breathing gas is the predive checklist in Table 6-1). required. therapy, surface decompression, or research. The mask must be cleaned with an antiseptic solu- and warm water, alcohol, and sterilizing agent) after each use, air-dried, and stored in a sealed plastic bag or be reinstalled for subsequent use. Routine inspection and preventive maintenance tion (antibacterial soap when malfunctioning is evident. Generally, inspection and repair service is provided by are required annually or 6-8 6.3.5 Oxygen Analyzers An oxygen analyzer is useful for monitoring oxygen concentrations in chambers where oxygen is used for The oxy- gen level in a hyperbaric chamber should be maintained between 21 and 23 percent to reduce the danger of fire (see Section 6.5). An absolute upper limit of 25 percent should be observed, in accordance with current National Fire Protection Association rules. Several oxygen analyzers are available. For units placed outside the chamber with a remote sensor located NOAA Diving Manual — October 1991 Hyperbaric Chambers and Support Equipment Table 6-3 Chamber Post-Dive Maintenance AIR Checklist SUPPLY Close all Check that all log Stow log book. valves Recharge, gauge, and record pressure of Fuel entries banks air compressors OXYGEN SUPPLY Clean compressors according to manufacturer's Check technical manual. inhalators, replace as Close __ VIEWPORTS AND DOORS Bleed Close system 2 all necessary cylinder valves 2 valves Check viewports for damage; replace as necessary Check door seals; replace as necessary Replace cylinders with Lubricate door seals with approved lubricant. Clean system BREATHING OXYGEN, as required Ensure spare cylinders are available CHAMBER Wipe have been made if contamination is suspected. NITROX (Therapy Gas) SUPPLY inside clean with vegetable-base warm fresh water Remove all but necessary support soap and Check chamber items from Clean and replace blankets Encase all Close flammable material in inhalators, replace as NITROX cylinder Bleed NITROX system Close chamber in valves all Replace cylinders with fire-resistant containers necessary valves 60% N 2 /40% 2 , as required Ensure spare cylinders available. Restock primary medical as required kit Empty, wash, and sanitize human waste bucket Check presence Air out chamber sand and water buckets of in COMMUNICATIONS chamber Test primary and secondary systems; Close (do not seal) outer door. Preferably leave one on inside chamber to keep moisture make repairs as necessary. light out. ELECTRICAL SUPPORT ITEMS Check and Check reset stopwatches and lock them in Ensure presence of decompression and treatment tables. housing for Turn all of emergency and Manual ventilation procedures, and the _ Restock secondary medical as required and stow kit If Clean and stow fire-retardant clothing inside the is When in chamber, an appropriate chamber penetra- required. Small, portable, galvanic cell-type however, may lights off Check Diving be placed directly in the chamber. choosing portable units for hyperbaric use, the bulbs as necessary encased If NOAA units, circuits light desk drawer list tion all Replace control in pressure-proof housing, check damage power wiring for fraying environmental monitoring equipment is used, maintain accordance with applicable technical manual. must be inspected to ensure that the system is properly grounded and that all fittings and terminals are in good order and encased in spark-proof lights inside, they housings (see the predive checklist in Table 6-1). manufacturer's instructions should be consulted to be certain that the unit is compatible with hyperbaric environments. Since nearly to partial pressures of 1 all oxygen ATA, mathematical WARNING units read out in response relative to a pressure of conversions must be ascertain the true reading at depth. made to The manufacturer's Lights Inside the Chamber Must Never Be Covered With Clothing, Blankets, or Other Articles That Might Heat Up and Ignite instructions should be consulted for detailed information on specific oxygen analyzers. 6.4 6.3.6 Electrical The electrical System system in Proper care of a chamber fiber optics or chamber, size of the no less than once a month, whichever comes first, the chamber should be maintained routinely in accordance with the Post-Dive Maintenance Checklist shown in Table 6-3. At this time, minor repairs should be made and supplies restocked. At least twice a year, the chamber to to provide lights keep all through through port windows, and to have the When chambers October 1991 — NOAA have electrical systems and Diving Manual hyperbaric chamber requires both routine and periodic maintenance. After every use or actual electrical system controls located outside the chamber. a com- varies in plexity, depending on the capability and chamber. Whenever possible, it is best electricity out of the CHAMBER MAINTENANCE should be inspected both outside and inside. Any deposits 6-9 Section 6 of grease, dust, or other dirt should be removed and the affected areas repainted (steel chambers only). Only mits corrosion to be recognized easily. Painting an aluminum chamber (and thus will serve only to hide encourage) corrosion. Corrosion is best removed by hand-sanding or by using a slender pointed tool, being careful not to gouge or otherwise damage the base The corroded area and a small area around it should be cleaned to remove any remaining paint or Electrostatic sparks. The most common sources of chamber fires in the past have been lighted cigarettes, faulty electrical powered devices. from overheating caused by a defective component, a short circuit, a jammed rotor in a motor, sparks produced by making or breaking a load-carrying circuit, or from a NOAA hyperbaric chambers must be pressure The procedures to be followed are shown in Table 6-4, and Table 6-5 presents a checklist for chamber pressure and leak electrically Electrical fires, however, can start either device with arcing brushes. The safe use of electrical devices in a chamber is primarily a design factor, requiring proper installation painted with a non-toxic, flame-retardant paint. tested at prescribed intervals. and sparks from wiring, corrosion products. Steel chambers should then be All Heat of compression • chambers are painted. Aluminum cham- steel bers normally are a dull, uneven gray color that per- metal. • of the supply wiring and properly designed devices. Wiring should be insulated with mineral materials or in metal conduit (which can be Teflon® and be shielded either rigid or flexible). tests. The housings of electrical de- vices such as instruments can be purged with an 6.5 A FIRE oxygen-free inert gas during operation and may or may not be pressure proof. Lights may be enclosed and PREVENTION hyperbaric chamber poses a special fire hazard because of the increased flammability of materials in compressed air or an environment otherwise enriched in oxygen. purged, or they have the may be external to the chamber and light directed inside with a "light Even an enclosed fiber optic cable. light pipe" or can generate chambers requires basically same practices as it does in other locations. The chamber environment, however, involves two special tion plan should include the capability to disconnect the atmosphere is an "artificial" one, and people are confined with the fire in a relatively must be Fire safety in hyperbaric enough heat the both the design and operational stages. considerations small space. sary for a — The fire, chamber anywhere or else, are a source of ignition, combustible materials, and an oxidizer. There are four steps in chamber fire safety in addition to preventive measures: detecting the fire, extinguishing — — mask for breathing, and if possible escaping. A safe chamber begins in the design stage. Various codes and design handbooks deal with this complex subject, and it can only be touched on here (Naval it, using a Facilities Engineering Command 1972, National Fire Protection Association 1984). After safe design, the manner in which the chamber tance. This section reviews is used chamber is next in impor- fire safety, cover- installations, control of the electrical haz- ber at all. When electricity is used, however, This may be accomplished by employing protective Use of low voltages ers. hazard, but it is (e.g., 12 or 24 volts) avoids this a dangerous misunderstanding to think such voltages cannot start a fire if (Shilling, Werts, and as intrinsically safe may ally are be used. Low-current, low- considered safe. There is Possible sources of ignition in a hyperbaric tion of made chamber safety. Ex- to prevent the igni- flammable gases or vapors by sparks generated electrical in a equipment; this is not the expected prob- diving chamber. Junction boxes and other equipment made chamber a fundamental dif- ference between the concepts behind "explosion-proof lem include: to explosion-proof standards may pro- vide the kind of protection afforded by mechanical housings (mentioned above), but this equipment is designed for a purpose different from the enriched- • Electrical wiring or apparatus oxygen hyperbaric environment and may • Cigarettes or other smoking materials inadequate. Also, most explosion-proof boxes are 6-10 is and qualifying voltage devices such as headsets and microphones gener- by 6.5.1 Ignition high-current flow possible. Devices tolerant of pressure plosion-proof housings are The Underwater Handbook requires devices such as ground fault detectors and interrupt- devices and those required for in it protection of the occupants from electrical shocks. additional references, consult the section on fire safety Schandelmeier 1976, pp. 646-664). protec- fire achieved by allowing no electricity in the cham- is and operational techniques. For a more thorough treatment of the subject and ing both basic principles A available. At some ard be considered at power instantaneously. Auxiliary lighting electrical all traditional trio of conditions neces- in a to start a fire, a fact to NOAA Diving Manual in fact be much — October 1991 . , , Hyperbaric Chambers and Support Equipment Table 6-4 Pressure Test Procedures for A NOAA Chambers* pressure test must be conducted on NOAA every 3. recompression chamber: Repeat Steps until all and 2 1 the leaks have been eliminated. 2. When initially installed; When moved and reinstalled; 3. At 2-year intervals 1, when in 4. Pressurize lock to maximum chamber place operating pressure (not hydrostatic at a given location. pressure) and hold for 5 The 1, test is to be conducted as minutes. follows: Pressurize the innermost lock to 100 (45 psig) feet an equivalent penetration seals, 5. solution, leak test viewports, fittings, shell all dog 165 feet Hold for (73.4 psig). 1 hour. 145 feet (65 psig) and locate and mark Mark and with Step 2 leaks. Depressurize the lock all components adjust, repair, or replace until final at least is Viewport Leaks gasket (replace - Remove the viewport necessary) if , feet Repeat Steps 1 through leaving inner door contact with any lubricant. come Acrylic viewports should not in 5, open and the outer door closed. Leak test only those portions of the chamber be lubricated Acrylic viewports should not in 145 wipe. 6. come pressure (65 psig) CAUTION or in accordance above and repeat this procedure as necessary to eliminate leaks. a. leaks. Depressurize chamber and weldments. repair leaks 2. If pressure drops below door dogs (where applicable) valve connections, pipe joints, shell Depressurize the lock to Using soapy water or . contact not previously tested. with any volatile detergent or leak detector (non-ionic detergent leak test) up . When to is be used for reinstalling viewport, take retaining ring bolts until the gasket compresses the viewport. Do not just overcompress the gasket. Weldment Leaks b. - Contact appropriate technical authority for guidance on corrective action. *AII NOAA standard recompression chambers are restricted to a too large and heavy for efficient use in the crowded conditions of a chamber. Although sphere in a is lem pressure of 100 psig, regardless of design pressure rating. in the piping of oxygen-rich gases, factor in should be avoided, the atmo- static sparks chamber maximum usually humid enough to sup- chamber A an explosion. vapors, gases, or dry, finely divided materials, none of flow through a in a chamber. Static sparks it is also a Because gases heat up when compressed, the sudden opening of a valve, which allows an oxygen mixture press sparks. Also, static sparks are only a hazard with which should be present safety. air is to compress in the pipes, can cause different but related hazard filter or muffler is the gas in the air supply. If the produced by an oil-lubricated compressor, some may usually can be prevented by using conductive materi- oil and by grounding everything possible. In some medical hyperbaric chambers, the patient himself is grounded with a wrist strap. Although the heat of compression is more of a prob- by compression or sparks generated by flowing gas. als October 1991 — NOAA Diving Manual collect Incredible as on the it filter may seem, or muffler and be ignited a ber fires has been smoking. This major source of chamis less of a hazard now than before the risks were widely known, but the pro- 6-11 Section 6 Table 6-5 Standard NOAA Recompression Air Pressure and Leak Test Chamber i Ship/Platform/Facility Type of Chamber: Double Lock Aluminum Double Lock Steel Portable Recompression Chamber Other* * (Description) NAME PLATE DATA Manufacturer Date of Manufacture Serial Number Maximum Working Date Pressure Pressure Test of Last . Test Conducted by (Name/Rank/Title) 1. Conduct Chamber visual inspection of chamber to determine if chamber satisfactory ready for test. Initials of Test is Conductor Discrepancies of inoperative chamber equipment: 2. Close inner lock door and with outer lock door open, pressurize inner lock to 100 fsw components do not (Note: Inner lock leak A. (45 psig) and verify that the following leak: If chamber has medical lock, open inner door and close and secure outer door.) checks Shell Penetrations and Fittings Satisfactory B. Viewports Satisfactory C. Door Seals Satisfactory D. Door Dog Shaft Seals Satisfactory E. Valve Connections and Stems Satisfactory F. Pipe Joints Satisfactory G. Shell Welds Satisfactory 3. Increase inner lock pressure to Record Test Pressure 225 fsw (100 psig) operating pressure (not hydrostatic pressure) for 5 minutes. Initials of Satisfactory (NOTE: Disregard small leaks 6-12 and hold Test Conductor at this pressure) NOAA Diving Manual — October 1991 Hyperbaric Chambers and Support Equipment Table 6-5 (Continued) Depressurize lock slowly to 165 fsw (73.4 psig) 4. Secure all supply and exhaust valves and hold for hour. 1 Pressure Start time Fnd timp Ci iterion: If Pressure pressure drops below 145 fsw (65 psig) Innpr Inrk prpssurp drop tpst , locate (NOTE: Repeat tests 6. tested in If of sections 2. sections 2, 3, 7. Outer Lock Checks A. Shpll Penptrations B Vipwports and and chamber has medical 3, leaks. Depressurize, repair, and fsw retest inner ock. I passpd Depressurize inner lock and open inner lock door. Secure 5. and mark 165 fsw in open lock, close position. Close outer and secure and 4 above when setup per section inner door 5. Leak door and secure. and ope n outer door) test only those portions of the char nber not 4. Fittings Satisfactory Satisfactory Door Seals C. Satisfactory Door Dog Shaft Spals D. Satisfactory Valve Connections and Stems E. Satisfactory Pipe Joints F. Satisfactory Shell G. Welds Satisfactory Maximum Chamber Operating 8. Pressure Test (5 minute hold) Satisfactory Initials of TestC onductor Inner 9. and Outer Lock Chamber Drop Test (Hold for 1 Hour) Start time Pressure Fnd time Inner Pressure and Outer Lock Pressure Drop Test Passed 165 fsw fsw Satisfactorily Initials of TestC onductor 10 . All above tests have been satisfactorily completed. Date Test Director Signature Diving Officer/ Director, October 1991 — NOAA Diving Manual NDP UDS Date Date 6-13 Section 6 smoking hibition against be and around chambers must in no combustion, there a broad pressure-oxygen per- is centage zone of incomplete or reduced combustion. strictly enforced. 6.5.3 Materials 6.5.2 Combustion The The primary factor increasing the risk of fire in a hyperbaric chamber is the increased combustibility An caused by the enriched oxygen atmosphere. oxygen atmosphere is one that either has a partial pressure or an oxygen percentage that (determined in a laboratory and level air, An chamber in the is rate when also has an increased percent- The relationships among flammability, partial pressure, and oxygen fraction are complex and non-linear, but show a consistent trend toward faster burning with increased oxygen percentage or with an increasing pressure at the same oxygen percentage (Figure 6-5). The nature of the age (i.e., fraction) of oxygen. background gas is minimum, and important, too, with helium requir- an overboard essential to use when if risk it dump is when oxygen is now considered system for exhaled divers are breathing oxygen by decompression or treatment. able the regarded as non-flammable known is fuel, i.e., chamber be kept to a Some it is in air will materi- burn in a best to rely on materials to be safe or relatively safe in oxygen. Metals are safe, as are ceramics. For wiring insula- TFE (Teflon®) is probably the best all-around material, but there are mineral insulations and fiber- some hard glass, as well as Melmac® that are usable in plastics like Bakelite® and some circumstances. Some fluorine-based elastomers are relatively safe in high oxygen mixtures, but their conductive properties are poor and they are expensive. For clothing, the popular choice is Durette®, but Nomex® is also adequate. Beta fiberglass is suitably flameproof but has undesirable wearing properties (Dorr 1971). Although chamber design is important to fire safety, even the well-designed chamber needs to be used prop- Because of the greatly increased added to the chamber atmosphere, gas in a fire safety requires that where possible, materials that are high oxygen mixture, so ing higher ignition temperatures but allowing faster burning. that, make fire not flammable in enriched oxygen be used. als tion, introduced when the gas is combustible materials all twice that of sea 2.5 times as fast at 165 fsw. it is additional hazard mixture greater than with paper strips) equivalent to 75 fsw is is The burning that of air at sea level pressure. the pressure enriched third element required to something to burn. Chamber It is mask during a also considered accept- a low oxygen level can be maintained by venti- lating or purging the chamber with air, but this is a less desirable option because the gas used for purging itself fairly rich in oxygen. It and high flows may be accompanied by excessive noise and compressor wear and tear. The "zone of no combustion" concept is the oxygen within accepted limits, helpful in the management is mandatory; all and other flammable materials must be stowed or removed from the chamber when it is being operated beyond the fire-safe zone. Particularly important to eliminate are fuzzy or powdered or finely divided materials and flammable liquids and loose clothing, papers, gases. One flammable gas is takes high flows to keep of fire safety in chambers. Good housekeeping erly to be safe. use in diving is that may come into increasing hydrogen. The use of this gas explored for deep diving because of properties (primarily its its is being physiological low density, which results in low breathing resistance). Hydrogen can be used with- out danger of explosion (once it properly mixed) is affect burning rate, changes in the percentage of oxy- when a mixture contains less than 5 percent oxygen, making it suitable for diving deeper than 100 fsw. Most of the safety problems associated with the use As of hydrogen as a diving gas occur during handling This concept takes into account the fact that, although changes in pressure at a constant oxygen percentage gen have a greater effect. a result, there is a "zone" of pressure and oxygen percentage that provides ade- and mixing. quate oxygen for respiration but that will not support combustion (Shilling, Werts, and Schandelmeier 1976; Rodwell and Moulton 1985). This is illustrated in Figure 6-6. An combustion 6.5.4 is that the saturation dives is chamber environment fire safe except in in most the later stages of Management The preceding important consequence of the zone of no chamber fires. of a Fire sections addressed the prevention of Another component of fire safety requires that the people involved be able to deal with a fire once decompression. The existence of this zone allows for it controlled combustion, such as that of welding, to be rapidly (National Fire Protection Association 1979), performed safely at pressure. In addition many 6-14 to the zone of starts. Although some past chamber fires have spread others have been extinguished without loss of NOAA Diving Manual — October 1991 Hyperbaric Chambers and Support Equipment Figure 6-5 Burning Rates of Filter Paper Strips 45° in N 2 -0 2 Mixtures at an Angle of 4.5 P0 2 =2Atm o 99.6% 2 CO E o LU DC CD 1.00 2.51 50 4.03 1 00 5.54 7.06 8.57 10.1 ATA 50 200 250 300 FSW 1 PRESSURE October 1991 — NOAA Diving Manual 6-15 Section 6 Figure 6-6 Combustion in N 2 -Oo Mixtures Showing the Zone of No Combustion O COMPLETE COMBUSTION A INCOMPLETE COMBUSTION O SLIGHT COMBUSTION Q NO COMBUSTION COMPLETE COMBUSTION o LU o rr LU Q_ LU _l o Z LU O > X o 4 12 8 TOTAL PRESSURE, ATMOSPHERES ABSOLUTE Combustion zones are defined by by dashed lines. The area A-D-E solid lines is and normal prolonged periods, while the area represented by A-B-C 6-16 respiration compatible with respiration is for breathe for short periods only (adapted from Shilling, Werts, and Schandelmeier 1976) safe to NOAA Diving Manual — October 1991 i Hyperbaric Chambers and Support Equipment life. It therefore essential that is chamber personnel be trained in fire safety techniques. At present, the best extinguishing agent for use fire hyperbaric chambers in Water extinguishes water. is primarily by cooling and works best flame or wets the 6.5.4.1 Detection Numerous fire a pressure in mechanisms are available Many of these systems are chamber, particularly ones operating the relatively low pressures used with compressed at air. The detection mechanisms most suitable for chamber use are those involving infrared or ultraviolet sensors. Ionization or smoke detectors may also be of value. and needs of the particular feel, for example, that a clinical treating patients with open wounds should have an alarm system only, rather than one that automatically deluges the chamber; a preferred approach is to have both a hand-held directable fire hose inside and switches to activate a general deluge system easily available to both chamber occupants and the topside crew. Whether a deluge or alarm system is used, it should be thoroughly tested at the time of installation and periodically thereafter. the context of the uses Most experts hyperbaric chamber installation. The best protection against fire crew that is ble detection is in system compressed air, the only dependa- another person standing by to is watch the operation. It is best if the designated "fire watch" person stands inside the chamber rather than outside (Hamilton, Schmidt, and Reimers 1983). 6.5.4.2 water, is personnel A on. fire to a to control small localized fires. The Breathing Masks and Escape caused by smoke inhalation fire fatalities are fire first thing the should do unless immediate escape is possible is to don a breathing mask. The masks should be handy and should have a breathable gas on line or be controllable by the occupants at all times. If quickly to another it is possible for occupants to flee chamber be sealed off from the fire, or compartment that can they should do so rather than donning masks and trying to extinguish the 6.5.5 fire. A summary • of Fire Protection of chamber fire Procedures prevention procedures Maintain oxygen concentration and partial pressure as low as possible, preferably within the region Use an overboard dump system whenever pure oxygen is breathed by mask in a chamber. of non-combustion. • Eliminate ignition sources. • Minimize combustibles, with the complete exclusion of flammable liquids and gases. If combustible materials must be employed, the type and quantity and their arrangement in the chamber must be carefully controlled. Firewalls and other containment techniques should • can be smothered by reducing the oxygen or fuel concentration to a level that will not sup- Summary follows: tem- evolution of flammable vapors. be utilized to isolate high-risk • fire zones. The extinguishing system should involve a water port combustion. deluge spray that can be activated either by occu- The fuel can be separated from the oxidizer by removing either the fuel or the oxidizer or by pants or topside operators and a hand that can be controlled mechanically separating the two. Mechanical protein • chamber hose will permit occu- fire occupants of a chamber with a perature below that required for ignition or the • must of course remain the chamber; lights rather than burns. Accordingly, the accomplished by physical, or The combustible material can be cooled fire in suppression system should be tested periodically Most • The chamber should be to the manually directable 6.5.4.3 four basic mechanisms: • power under chamber operating conditions. a combination of physical and chemical, actions involving • Simultaneous with the discharge of velocities. electrical shut off to prevent shorting and electrical shocks to Extinguishment Fire extinguishment all an alert chamber backed up by detectors. During certain welding operations strikes the pressure to produce the desired degree of atomization and droplet pants of a There are two problems with fire detection systems: false alarms and failure to detect a fire quickly enough. Any detection system needs to be studied thoroughly in it spray nozzle must be 50 psi or more above chamber detection for routine fire protection. usable if spray form. The pressure at the fire in foams operate in this fashion by blanketing the fuel and separating it from the oxidizers. The reactions occurring in the flame front or just before the flame front can be inhibited or interfered with through the use of chemicals. October 1991 — NOAA Diving Manual fire hose and directed by the cham- ber occupants. • A mask with an appropriate gas on line should be available for each • Escape to should be the tions plan, chamber occupant at all times. another chamber or directly into the sea first whenever option in the fire safety opera- feasible. 6-17 < Page SECTION 7 AND SUPPORT PERSONNEL DIVER 7.0 General 7.1 NOAA Divers 7-1 7.1.1 Selection Standards 7-1 7.1.2 Physical Examination 7-1 7.1.3 Swimming 7-3 7.1.4 Scuba Training TRAINING 7.2 7-1 Skills 7-3 7.1.4.1 Classroom 7.1.4.2 Pool and Open-Water 7-4 7-4 7.1.5 Umbilical Dive Training 7-5 7.1.6 Special Equipment Training 7-6 7.1.7 Mixed-Gas Training 7-6 7.1.8 Saturation Training 7-7 7.1.9 Chamber Operator Training 7-7 Training of Diving Supervisors 7-8 7.3 Diving Medical Technicians 7-8 7.4 Hyperbaric Physicians 7-9 7.5 Research Divers 7-10 Selection 7-10 7.5.1 Curriculum Equipment Maintenance 7.5.2 7.6 7-1 7-1 « < DIVER AND SUPPORT PERSONNEL TRAINING 7.0 GENERAL screening by experienced This section describes the general content of diver training programs, the training involved in preparing under specialized circumstances, and basic approaches to diver training. It does not prescribe to dive specific training procedures or attempt to teach divers how to perform specific underwater Many the NOAA organizations offer diver training. Navy are among agency missions. and universities offer diver training Many and diving schools offer extensive diver training for divers in the commercial diving industry. These training organi- zations select students on the basis of their personal motivation, physical fitness, and basic swimming NOAA This section emphasizes the training of all ation interview helps to identify any misconceptions NOAA diving work. 7.1.2 Physical divers. The physical examination NOAA Corps universities and organizations involved in sponsored programs that require diving officers, skills. by a trained hyperbaric physician. Military, com- tion mercial, and scientific divers are evaluated according to standards set forth organizations. NOAA cal standards for NOAA from other Federal agencies. All of the candidates who apply to NOAA's diving program tions increase the risk of serious injury or disability in framework programs can vary who greatly: NOAA shallow water as well as divers who • Any Allergy to materials used comes terms of in diving equipment that into contact with the skin is a relative • History of sensitization or severe allergy to marine or waterborne allergens should be disqualifying. Psychiatric • • Acute psychosis should be disqualifying. Chronic or acute depression with suicidal tendenbe disqualifying. Chronic psychosis in partial remission on medica- tion should be disqualifying. divers are selected from volunteers on the fitness The psychological evaluation • and Substance use or abuse, including abuse of alcohol or use of mood-altering drugs, should be disqualify- for acceptance into the program consists of a personal interview, an assessment of motivation, and a general Diving Manual in contraindication. Selection Standards — NOAA rank systems chronic or acute dermatitis adversely affected cies should October 1991 to by prolonged immersion should be disqualifying. • and physical made Skin are required to The selection and training of NOAA divers are monitored carefully by the NOAA Diving Program. basis of their psychological is their relative importance. divers dive only occasionally dive regularly as part of their normal duties. their water skills. The guidelines below present for individual dive fitness evaluations; and no attempt of diving involved in the dif- include senior researchers NOAA divers. conditions disqualify a person for diving with compressed gas, and other medical condi- • are volunteers. 7.1.1 its Many medical by their respective agencies or has developed and enforces medi- NOAA- also trains divers in if they are not established standards. These guidelines researchers, diving technicians, and individuals from NOAA of divers to determine they are medically qualified to dive requires evalua- are organized in accordance with a systems approach, NOAA-certified divers include ferent Examination the diving environment. NOAA DIVERS The amount and type training or the require- ments, conditions, and responsibilities of subsequent a 7.1 may have about the candidate skills. divers and other personnel, but many of the principles described here apply to the training of divers to identify and research diving. The evalu- stresses of operational to students Commercial local dive shops. NOAA are unlikely to be able to handle the col- and faculty members who use diving as a research tool. Diver training also is available from diver certification organizations who and those government agencies that train divers in support of leges tasks. individuals ing. • Careful attention should be paid to the maturity of prospective candidates, their ability to adapt to 7-1 Section 7 stressful situations, their motivation to pursue div- or has been surgically repaired and their ability to understand and follow decompression tables and directions. ing, is ally cleared for diving with the may perforation Neurologic • • Closed head injury; following full recovery, any neurologic deficit (including an abnormal EEG post-traumatic seizures) should be disqualifying. Spine injury, with or without cord damage, may • and attendant lower extremity paralysis. Prior cord decompression sickness with residual symptoms Chronic or acute • • corrected) should be evalu- Meniere's disease and other conditions that are Extensive mastoid surgery, stapedectomy, or disorder that causes or results in loss of con- includes any form of seizure, previous gas • • patent nasal passage and the absence of sinus and Nasal polyps, deviated nasal septum, and other diving is permitted. • Acute or chronic ated individually; however, • A is not an absolute infection should be disqualifying. history of long-term decongestant use should contraindication. Issues to be considered include trigger a search for the cause of the congestion, d absence of seizures, presence of residual neurologic and candidates should be warned about the dangers of the chronic use of chemical agents while diving. \ deficit, and impairment of regional perfusion. Ophthalmologic Oral and Dental Candidates should demonstrate adequate visual acuity to orient themselves in the water and on a boat. Corrective lenses, either fixed to the face mask • Candidates must be able to be fitted with and hold a scuba mouthpiece. • or soft contact lenses (which allow for gas Where there is a danger that trapped gas could get under a tooth and rupture transfer), are acceptable. • A Diving after intracranial surgery should be evaluit motility has returned to normal. obstructive nasal lesions should be corrected before dispose to decompression sickness). • membrane nasal congestion are essential in diving. regional perfusion abnormalities that would pre- • Barotitis should be disqualifying until all middle Nose and Paranasal Sinuses embo- lism, or prior cerebrovascular accident (due to arti- cochlear implant should be disqualifying. panic neuropathy. Any externa should be dis- ear inflammation and fluid have resolved and tym- ated on an individual basis, as should peripheral sciousness should be absolutely disqualifying. This otitis associated with vertigo should be disqualifying. should be disqualifying. Herniated nucleus pulposis • recur. Active ear infection should be temporarily dis- ficial (if condition- warning that the qualifying until healed. carry an increased risk of decompression sickness of the lower back may be qualifying. or • • and the candidate able to auto-inflate, he or she it, diving should not be permitted. Narrow-angle glaucoma, aphakia with correction, motility disorder, cataract, and retinitis pigmentosa • Badly decayed or broken teeth should be dis- qualifying. are relative disqualifications for diving; a skilled Pulmonary ophthalmologist should be consulted. • Because color vision is required for certain diving tasks, deficiencies in color vision may • Because any abnormality tion be dis- rax, or qualifying. • As a prerequisite to diving, candidates must have tympanic membranes and be able to automiddle ear. Performing a Valsalva or Toynbee maneuver can be used to indicate whether the candidate can inflate his or her middle ear (inability to do so predisposes to rupture of the tympanic membrane or round window). Tympanic membrane perforations should be disqualifying (an opening in the tympanic membrane would allow water to get into the middle ear). If a tympanic membrane rupture is completely healed intact 7-2 be absolute disqualifications for diving: — Bronchial asthma; — History of traumatic or spontaneous pneumo— Previous penetrating chest trauma surgery of the —Chronic obstructive lung including —Active pneumonia or lung and disease with cavity formation. — Mycotic A Long-term cigarette smoking increases the ^ thorax; inflate the • pulmonary system func- pneumomediastinum, the following condi- tions should Otolaryngologic in can cause arterial gas embolism, pneumotho- or chest; disease; infection, active tuberculosis; (fungal) • risk of pulmonary complications while diving. NOAA Diving Manual — October 1991 Diver and Support Personnel Training • All candidates should be given a screening chest x ray to determine if • Obesity increases the relative risk of developing decompression sickness because of the decrease they have a disqualifying lesion. in gas diffusion through adipose tissue. Cardiovascular • • Cardiovascular defects can be disqualifying because they predispose the individual to unacceptable risks. Conditions that should be disqualify- — Cyanotic heart coarctation of the — Aortic — Prosthetic heart — Exercise-induced rhythm disorders, Paralytic disorders should be relatively disqualifying. disease; stenosis or basis. Musculoskeletal • ing are: Other endocrine abnormalities should be evaluated on a case-by-case • Bone fractures that are incompletely healed and aorta; osteomyelitis that is actively draining should be valves; disqualifying. including • disorders that manifest as paroxysmal tachycardias despite control with drugs; — Heart block; — Cardiac or pulmonary A-V shunts; — Candidates with pacemakers should ment should be • disqualifying. Inadequate physical fitness to handle the physical work of diving should be disqualifying. be indi- vidually evaluated and generally should be disqualified. • Deformities, either congenital or acquired, that impair the candidate's ability to use scuba equip- Obstetric and Gynecological • Coronary artery disease should be evaluated by Pregnancy should be absolutely disqualifying because of the risk of bubble formation in the developing fetus during decompression. an expert. • Peripheral vascular disease requires case-by-case evaluation. • 7.1.3 Candidates taking cardiovascular drugs (including Skills All applicants for diver training should perform the blood pressure medication) should be evaluated following on a case-by-case basis. The use of beta blockers snorkels and with confidence and good watermanship: increases the risk of swimming exercises without face masks, fins, or bronchospasm and suppresses • the stress response. • Swimming • case basis. Swim 300 sidestroke, Hypertension should be considered on a case-by- yards (274 meters) using the crawl, and backstroke Swim under water for a distance of 50 feet (15.2 meters) without surfacing Hematological • • Leukemia brosis • • or pre-leukemia manifesting as myelofi- 7.1.4 and polycythemia should be disqualifying. Anemia relatively disqualifying is and requires Intoxication that has caused Scuba Training Although NOAA certification program, case-by-case evaluation. • Stay afloat for 30 minutes. Sickle cell anemia should be disqualifying. methemoglobinemia has its own NOAA diver training and personnel often receive basic scuba training before they become NOAA diver candidates. Regardless of the training organization, should be disqualifying. however, there are basic practices and procedures that Gastrointestinal • Any disorder that predisposes a diver to vomiting should be disqualifying (including Meckel's should be included • Unrepaired abdominal or inguinal hernia should • be disqualifying. Active peptic ulcer disease, pancreatitis, hepatitis, colitis, cholecystitis, or diverticulitis should be dis- qualifying until resolution. diet controlled. October 1991 competence that will — NOAA • and efficiently. Diving procedures, particularly those of a lifesaving Diabetes mellitus should be disqualifying unless is a level of Divers who can respond to emergency situations and make appropriate decisions when faced with problems under water Divers who can execute assigned underwater tasks safely Endocrinological • who reach Divers permit safe open-water diving sickness). • any scuba training program. For di- verticulum, acute gastroenteritis, and severe sea • in example, any diver training program should produce: it nature, should be overlearned to ensure automatic response Diving Manual in emergencies, which reduces the likelihood 7-3 Section 7 of the diver losing control and panicking (Bachrach and Egstrom 1986). Although training courses vary widely among organizations with respect to length, content, complexity, and water skills required, all courses should include surface-support requirements in vessel diving; and water entry and • definition of tasks, selection of equipment, selec- tion of dive team, emergency planning, special equipment requirements, and setup and check out both classroom sessions and in-water training. The core of a training program for working divers should follow the guidelines discussed in Sections 7.1.4.1 and exit; Operations planning: objectives, data collection, of support platforms; • Principles of air diving: introduction to decom- pression theory, definition of terms, structure 7.1.4.2. and content of diving tables, single and repetitive div- 7.1.4.1 ing principles, practical decompression table problems (including decompression at altitude), and Classroom calculation of air supply requirements; Classroom lectures using multimedia presentations • should be developed to provide the candidate with as much knowledge as possible. It is important for the ments; hand and line signals; recall; water emer- candidate to develop a general understanding of diving and the principles and the diving environment, Diving procedures: relationship of operations planning to diving procedures; warning signal requiregencies; buddy teams; tending; precautions required by special conditions, e.g., pollution, restricted self- confidence (but not overconfidence) necessary to operate visibility, safely in the field. Formal training courses are only the becoming a safe and efficient diver. With first step in this in or flying after diving; dive station setup and post- mind, dive procedures; work procedures for search and diver training should expose the trainee to a wide vari- recovery; salvage and object lifting; instrument ety of diving-related experiences in addition to teaching the basics. Details of various diving systems ancillary equipment will deployment and maintenance; and underwater navi- and gation methods; be learned as part of on-the• job training. Topics to which working and research divers should be exposed during basic currents; "dive safe ship" requirements; boating safety; dangers of diving at high altitude Accident prevention, management, and and advanced resuscitation training include: • (CPR), use of oxygen resuscitators, development of accident management plans, recov- Diving physics: pressure, temperature, density, spe- ery of victims and boat evacuation procedures, buoyancy, diving gases, the kinetic theory of gases, and the gas laws and their practi- lung overpressure, and "diver's colic"), the indi- recognition of pressure-related accident signs and symptoms, patient handling en route to treatment, introduction to recompression chambers and treatment procedures, and procedures for reporting accident investigations (see Sections 18 and 19); and Diving environment and hazardous marine life: tides and currents (surf; thermoclines; arctic, temperate, and tropical conditions); waves and beaches; rip currents; and river, harbor, and marine life rect effects of pressure (decompression sickness, hazards. cific gravity, cal application in diving; • first aid: basic principles of first aid, cardiopulmonary Diving physiology and medicine: the anatomy and mechanics of circulation and respiration, the effects of immersion on the body, hypoxia, anoxia, hyper- • capnia, hypocapnia, hyperpnea, apnea, hyperthermia, hypothermia, the direct effects of pressure (squeeze, gas embolism, inert gas narcosis, oxygen toxicity, bone necrosis), breathing gas contaminants, drown- near-drowning, overexertion, exhaustion, breathing resistance, "dead space," and psycho- ing, logical factors • such as panic; Equipment: selection, proper use, and care of personal gear; air compressors and compressor systems; operation and maintenance; tank-filling procedures; requirements for testing and inspection of specific types of cylinders); • 7-4 and air purity equipment (including scuba standards and testing; 7.1.4.2 Pool and Open-Water A program of work in the water that progresses from pool to protected open water and then to a variety of open-water situations is essential to diver training. Students should be exposed to open-water conditions while diving at night, under conditions of reduced visibility, and in cold water (see Section 10 for details of diving under special conditions). An understanding of the proper use of mask, fins, and snorkel; surface swimming; surface dives; underwater swimming; pressure and rescue techniques Diving platforms: shore, small boat, and large vessel equalization; platforms; fixed structures; safety precautions and skin (breath-hold) is required to master and scuba diving. NOAA Diving Manual — October 1991 Diver and Support Personnel Training hazardous, and work- Experience and experimental data have shown that must be the diver should be trained to maintain a reasonably competent swimmers in excellent physical condition. The skin diver is subject to barotrauma of the ears and sinuses, just as any other diver is; however, air embolism and related complications are a problem only if the skin diver breathes air from a scuba cylinder, a habitat, or an underwater air pocket. Since breathholding can cause serious problems, divers should constant respiration rate with a nearly complete inha- Breath-hold or skin diving is ing and research divers using this technique lation and exhalation pattern. This slow deep-breathing pattern permits good air exchange at relatively low flow rates. Keeping the flow rate at lower levels results more comfortable breathing; higher in respiration rates can cause discomfort and anxiety (Bachrach and Egstrom 1986). thoroughly understand the potential hazards of prolonged breath-holding under pressure. Specific skills to be learned in a pool and open-water program should include but not be limited 7.1.5 Umbilical Umbilical diving Dive Training is to: also referred to as surface-supplied diving. In umbilical diving, the diver's breathing gas • Skin diving is supplied via an umbilical from the surface, which pro- skills — equalization of spaces — mask clearing and equalization — snorkel clearing — proper use of buoyancy compensator — proper use of weight belt (including how ditch — proper kicks with and without —distance swimming with skin-diving gear — water and surface dives vides the diver with an unlimited breathing gas supply. air Preliminary selection procedures and criteria for umbilical dive training are essentially the same as those for basic scuba. In NOAA, divers applying for umbilical training must be certified as advanced working to it) fins which requires the completion of at least 100 logged dives. Before qualifying as umbilical divers, divers, trainees should receive instruction and training in: full entries • The general purpose and limitations of surface- supplied (umbilical) diving; • Skin diving confidence • drills • — recovery of mask, and —clearing the ears —one-finned kicks over a distance — snorkeling without mask snorkel, fins system; • Lifesaving lar tasks skills • — search and recovery — proper rescue — rescue techniques with and compensator — rescue — in-water mouth-to-mouth Use of accessory tools and equipment basic to umbilical procedures and specific to the particu- • • Use of masks and helmets; Assembling and disassembling of the gas supply • being contemplated; Methods of achieving intelligible communication; Equipment repair and maintenance; Water entry, descent, and ascent procedures and problems. entries without a buoyancy When initial training is completed, an open-water qualification test that includes both general diving carries techniques and actual working procedures should be artificial resuscita- given. tion Qualification Test • Skills involving the use of scuba equipment — sharing — "ditch and don" exercises — mask clearing — regulator recovery and clearing —emergency ascent breathing — —scuba — buoyancy control — gauges and other special support equipment — scuba rescues. air To pass the qualification demonstrate the ability • test, candidates must to: Plan and organize an air surface-supplied diving operation to depths between 30 and 50 fsw (9.1 and 15.2 msw), including calculation of hose pressure and air requirements and instruction of surface personnel; station entries life October 1991 — NOAA Diving Manual • Demonstrate ability to rig all surface and underwater equipment properly, including air supply, mask/helmet, communications, and other support equipment; 7-5 Section 7 • • • Demonstrate proper procedures of dressing-in and Variable- Volume dressing-out, using the particular pieces of equip- — Suit preparation, and maintenance — Emergency procedures blowups, weighting, buoyancy control —Control of operational problems — Hypothermia/hyperthermia —Accessories — In-water training — Cleanup and decontamination after pollutedselection, ment needed for the working dive; Tend a surface-supplied diver; Demonstrate knowledge of emergency procedures (these may differ for for each project or exposure) as determined by the instructor or dive master; • Participate in at least two practice dives, as described below: — Properly (3 enter water that is at least msw) deep and remain submerged 10 fsw water dives for at least Contaminated-Water Diving Training 30 minutes, demonstrating control of air flow, buoyancy, mobility, and facility with communi- —Protective systems — Donning and doffing — Buoyancy — Hyperthermia —Training tender — Work performance while — Decontamination procedures. cation systems. — Ascend and leave water a prescribed manner. — Properly enter water that between 30 and in control is 50 fsw (9.1 and 15.2 msw) deep and conduct as a work-related tasks. fully suited After successful completion of this tor should evaluate the diver's test, the instruc- performance and estab- phased depth-limited diving schedule lish a Dry Suit Training to ensure a safe, gradual exposure to deeper working depths. 7.1.7 Detailed descriptions of umbilical diving equipment Mixed-gas diving involves the use of a breathing other than air; this mixture may consist of nitrogen-oxygen, helium-oxygen, or oxygen and one or more inert gases. The curriculum for NOAA's mixed-gas training program includes coverage of the following topics: and its 7.1.6 use appear in Sections 5.2 to 5.2.4.10. Special Equipment Training how to operate and maintain and umbilical equipment, divers In addition to learning diver life-support scuba medium may be called on to use special equipment in the performance of their duties. In such instances, new techniques and procedures must be learned from divers who are already experienced in their use, from technical personnel (such as Mixed-Gas Training • Oxygen • Nitrogen-oxygen breathing mixtures • Depth/time • Central nervous system and pulmonary oxygen partial pressure limits limits for oxygen during working dives manufacturers' representatives), or by test and evaluation. Examples of types of equipment that are used by divers and whose use requires special training are: variable-volume suits; thermal toxicity • Nitrogen/oxygen breathing media mixing procedures • Analysis of mixed-gas breathing media • Mixed-gas diving equipment (open-circuit systems) protection diving suits; protective suits, clothing, support equipment, and breathing apparatus for diving in contaminated water; photographic/video equipment; scientific equipment; and underwater tools. Many cial • • NOAA circuit addressed include: • Nitrox I NOAA Nitrox decompression tables NOAA Nitrox residual nitrogen table NOAA Nitrox surface interval table. NOAA mixed-gas trainees attend classroom • I • I —Search and recovery techniques — Wireless communications — objects —Ships husbandry systems — Underwater — Pinger/sonar —Underwater • I television locators tools equivalent air depths for open- scuba Operational Diver Training Lifting of 7-6 Nitrox I no-decompression limits and group designation table for no-decom- pression dives training programs prepare divers to use spe- equipment and protective clothing. The topics NOAA repetitive and then progress to sessions open-water dives, during which they use a nitrox (68 percent nitrogen, 32 percent oxygen) breathing mixture. Divers enrolled in a commercial diving mixed-gas course or those being trained by their companies receive classroom and open-water NOAA Diving Manual — October 1991 Diver and Support Personnel Training training in the use of heliox (helium-oxygen) breathing mixtures. in Heliox is a widely used breathing deep mixed-gas diving and in medium saturation diving. For example, water boils at a higher temperature under water than on the surface: 262°F (128°C) at 50.5 feet (15.4 meters) and 292°F (144X) at 100 feet (30.5 meters); cooking procedures must be altered, tat. because burned food not only constitutes a fire hazard 7.1.8 Saturation Training but produces toxic gases at depth. (For additional infor- Although the basic requirements for saturation diving are the same as those for surface-based diving, there (1984).) are ration usually is "home base" during satu- either a seafloor habitat or a diving system (see Section bell ration diver needs a 17). A that need to be addressed some important differences during training. The diver's mation on underwater habitation, see Miller and Koblick For this reason, the satu- fundamental reorientation to the slight loss in speech occurs as a intelligibility also atmosphere result of the denser at depth. The amount of speech distortion depends on the habitat breathing mixture and the depth. Other factors directly affecting the saturated diver or a habitat diving program environment. For example, the saturation diver must include: the necessity to pay special attention to per- constantly be aware that returning to the surface will sonal hygiene, e.g., to take special care of the ears and complicate, rather than improve, an emergency situa- Because of the high humidity encountered in most habitats, the growth of certain pathogens and organisms is stimulated and recovery is prolonged. Proper washing, drying, and care of diving suits is This factor has specific implications with respect tion. to the selection and use of certain pieces of saturation diving equipment. For example, in saturation diving: skin. essential to prevent skin irritation or infections. Trainees • Weight belts without quick-release mechanisms or weight harnesses should be used; • Buoyancy compensators with to the use of toxic materials in a oral inflation tubes rather than a cartridge or tank inflation system should be used; • A for the repair of when umbilical equipment is utilized; filling scuba cylinders to avoid admitting water into the valves. Because the consequences of becoming lost are so program also should include training in underwater navigation techniques. serious, a saturation diving training lines, string highways, ripple marks, suits) and aerosol sprays. should teach divers the procedures for making ascending and descending excursions from the storage depth. Special diving excursion tables have been developed for excursions from the saturation depth. These tables are designed to consider storage depth, oxygen dose, nitrogen partial pressures, and other facTrainees should become familiar with these tables tors. and their limitations. A Divers should be instructed in the use of navigational such as grid wet Training for saturation diving from underwater habi- in tropical regions; backup breathing gas supply should Extra precautions must be taken when aids, to the use of scientific preparations but also to the use of tats self-contained be used • closed-environment system such as a habitat. This applies not only normally harmless things such as rubber cement (used Adequate diving suits should be worn because the extended diving time involved in saturation may cause chilling even • should be aware that there are restrictions with respect unique feature of saturation diving ability to make upward is the diver's excursions. However, upward topographical features, and navigation by compass. excursions constitute a decompression, and divers must Because compasses are not always accurate, divers should be trained to use the compass in combination with topographical and grid line information. Training in habitat operations, emergency procedures, and local diving restrictions usually is conducted on site. Such training includes instruction in: communi- be careful to remain within the prescribed excursion cation systems; use of special diving equipment; habi- resist tat support systems; emergency equipment; regional topography; underwater landmarks; navigational grid systems; depth and distance limitations for diver/ scientists; This applies not only to the divers themselves limits. but also to certain types of equipment; for example, camera is opened and reloaded in a habitat, if a an upward excursion of 10 to 15 feet (3.0 to 4.6 meters) can cause flooding because such equipment is not designed to internal pressure. Students should be instructed check all equipment to be used in a habitat to determine whether it is designed to withstand both internal and external pressures. to and operational and safety procedures used by the surface support team. Other features related need to to seafloor habitation also be identified during saturation training. Some of these relate to housekeeping chores inside the habi- October 1991 — NOAA Diving Manual 7.1.9 Chamber Operator Training The operation and maintenance chambers are of recompression a necessary part of a diving program; it is 7-7 Section 7 therefore important to ensure that all personnel oper- As an often not practical. is (DMT) alternative, a Diving ating recompression Medical Technician include the following topics: emergency medical situations and can also communicate effectively with a physician located at a distance from the diving site chambers are properly trained and certified as chamber operators. A training program for chamber operators should • Introduction to hyperbaric chambers; • Chamber trained in the care of diving casualties can be assigned to the The development — Pre- and post-dive procedures — Plumbing — Controls — Life-support and emergency procedures — Breathing and communication systems — Maintenance procedures in- of emergency medical service organizations began in the United States in the mid1970's in response to the need for improved national emergency medical fic care. The National Highway Traf- Safety Administration of the Department of Trans- portation developed and implemented a program to Emergency Medical Technicians (EMT's) at vari- train ous levels of certification. These services, coordinated Recordkeeping; by the Department of Transportation, are offered and Introduction to the physics of pressure; Decompression theory and calculation of decompression tables; Recompression theory and treatment managed at the state level. Courses in various aspects of emergency medical American American Heart Association, and local fire and rescue groups. Individuals successfully completing these courses are certified by the sponsoring agency as having fulfilled the course requirements. care are offered by organizations such as the tables; Red Barotrauma; Examination and handling of patients; Emergency management of decompression and air embolism; sickness Cross, the may Courses lead to different levels of certification, Inside tending procedures; kit national, state, local, or regional, e.g., contents and use; Review of case histories; Hands-on experience with simulated treatments; Chamber An (see Section 19.6.1). setup and subsystems; Chamber medical site. dividual so trained can respond to and thus may reflect different levels of proficiency. In the late-1970's, the need for medical technicians emergency treatment of diving caswas recognized; this specialized need arose specializing in the operation procedures. ualties because existing EMT training programs were heavily oriented toward urban ambulance-hospital emergency TRAINING OF DIVING SUPERVISORS 7.2 Many organizations, including NOAA, the Navy, and commercial diving companies, designate certain experi- enced divers as supervisors. NOAA has four supervi- sory diving categories: Line Diving Officer, Unit Diving Supervisor, Diving Instructor, Each organization provides and Divemaster. training that is specifi- cally related to the goals of the organization; however, all diving supervisors are required to have a broad range of diving experience. In addition, every supervisor must have the working knowledge projects, oversee diving activities, to plan diving conduct inspections, and investigate accidents. Diving supervisors receive advanced training in dive planning, the use of special equipment, first aid, communications, and accident management. systems. The medical technicians interest in diving grew with the development of offshore oil and gas well drilling platforms. Experts decided that the most workable solution to this need was to cross-train work- ing divers as medics rather than to train medics to working by economic considerations, since using a diver as a medic made it unnecessary to have a person standing by. The National Association of Diver Medical Technicians (NAMDT) was founded in 1981 and, by 1985, a number of training organizations were approved to provide DMT training. NOAA has adopted DMT training for its medical personnel and has a representative on the NAMDT Board of Directors. The approved DMT training program is an extensive 303-hour course and includes training in the following treat diving casualties. This choice to train divers as medical technicians was also driven areas: 7.3 DIVING MEDICAL TECHNICIANS Although there are obvious advantages in Lecture (158 hours) having a qualified hyperbaric physician at a diving site, this 7-8 • orientation, anatomy, medical terminology, legal problems NOAA Diving Manual — October 1991 Diver and Support Personnel Training support, shock, use of oxygen ing casualties has increased. In response to this need, • basic • systemic diseases and injuries several organizations offer specialized training. • medical, environmental, thermal, diving, and de- courses range from a series of lectures to more inten- compression aspects sive courses lasting several weeks. • equipment • life handling, emergency com- use, patient drugs and fluids Society, Inc., which One • animal laboratory (optional) the is located in of the most respected and comprehensive train- gram offered by autopsy (optional) • diving treatment, neurological examination • chamber operations NOAA. Started the 3-week pro- is in 1977 with finan- support from the Department of Energy and the cial • hyperbaric Bethesda, Maryland. ing courses in hyperbaric medicine and care, suturing patient assessment is in Undersea and Hyperbaric Medical medicine • best source of information on the availability of courses munications Laboratory and Practical Experience (115 hours) The These cooperation of the U.S. Navy, this program has trained The course over 269 physicians to date. includes train- ing in the following areas: Clinical Observation (30 hours) • mixed ambulance/emergency room experience. DMT training may based on the number but includes a it is EMT Level I diving physics basic diving physiology Program fundamentals of of important additions. Because stress physiology be hours or even days before medical help oxygen toxicity emergency diving situation, the DMT must be capable of delivering more advanced support arrives in an than a medical technician DMT's ingly, in mothorax air an urban area. Accord- saturation diving commercial diving equipment decompression tables pneu- stabilization, simple suture techniques, embolism vestibular problems related to diving receive training in parenteral drug administration, intravenous infusion techniques, exchange and behavior inert gas and decompression sickness and treatment other special procedures. DMT's must helium-oxygen tables and recompression treatment be recertified every 2 years and must attend 24 hours of lectures and serve 24 hours in recompression chamber operation and safety an procedures ambulance/emergency room situation to maintain their certification. Serving under the diving supervisor, the trained DMT brings enhanced diagnostic and clinical skills to medically DMT's gas analysis systems pressure exposures and geographically remote worksites. also have the ability to orientation to the national Divers Alert received from medical specialists belonging to organi- Network (DAN) Network basics of diving accident though these experts are geographically distant from the scene of the diving (see Section recompression chambers emergency treatment of diving casualties implement expert advice zations such as the national Divers Alert in hyperbaric oxygen therapy 19.6.1), even management case histories of diving accidents and treatment polluted-water diving accident or illness. treatment of near-drowning victims 7.4 A evaluation and assessment of scuba diver injuries HYPERBARIC PHYSICIANS hyperbaric physician cial training in the is and illnesses. a medical doctor with spe- treatment of medical problems Physicians trained in hyperbaric medicine are an related to diving and/or elevated atmospheric pres- important resource for the diver. Every diver should Such a physician may be a general practitioner or a specialist in any branch of medicine. In many cases, the personal impetus to become an expert in hyperbaric medicine derives from the fact that the physician is also a diver. Historically, the U.S. Navy and U.S. Air Force have been the primary sources of expertise and learn the sure. trained personnel in hyperbaric medicine. Because of the increase in the October 1991 — NOAA Diving Manual cian in his of divers, to treat div- or her area. In the event of a diving accident related to pressure, such as an sion sickness, it is essential to embolism or decompreshave located a physician trained in hyperbaric medicine before beginning the Hyperbaric chambers are described in Section and the treatment of diving casualties is discussed dive. number however, the need for physicians trained name, address, and phone number of the nearest hyperbaric facility and/or hyperbaric physi- 6, in Section 20. 7-9 Section 7 7.5 RESEARCH DIVERS Research diver training number tories. is offered by NOAA and a and the success of scientific diving are maintained (American Academy of Underwater Sciences 1987). of educational institutions and marine labora- Although the course content and style differ Selection 7.5.1 with different organizations, the objective of such courses is either to train experienced divers in scientific tech- niques and methods to enable them ter scientific technicians or to train tists to act as underwa- experienced scien- the techniques and methods of underwater work. in In either case, the curriculum should include advanced instruction in diving physiology, uses of underwater equipment, and a review of the potential hazards faced by Selecting individuals for research diver training depends on the objectives of the particular course. The acceptance of individuals for such training should be based on need, academic background, personal moti- and the vation, ability to pass certain fitness requirements. mon If possible, swimming and individuals with com- objectives should be grouped together and trained in a single class. divers. Each of these Selection criteria should require research diverfactors should be related to the prob- candidates to demonstrate evidence of: lems faced by diving scientists and their impact on the conduct of underwater investigations. Diving safety should be emphasized throughout the course so that on • Diver certification from a recognized organization • Satisfactory completion of a physical examination completely com- • to concentrate their • Good Need energies on the work or scientific tasks at hand. This • Training degree of competence can be achieved only • Training or equivalent experience methods completion of training the divers fortable in the water feel and are able if the basic diving skills are learned so thoroughly that routine become operations and responses to emergencies • physical condition for the specialized training in the basics of first aid, Ability to pass diving and CPR including swimming in research skill tests to the satisfaction of the examiner. automatic. University research diver training programs have historically lasted for a minimum of 100 hours and Research divers must be comfortable in the water and required candidates to complete 12 open-water dives. know their limitations and those of their equipment. To accomplish these ends, a series of pretraining tests Admin- are used to predict likely success in the diving envi- In 1984, the Occupational Safety and Health istration in (OSHA), which had promulgated regulations 1978 governing commercial diving operations, spe- exempted from these regulations those scienand educational diving programs that could meet certain requirements. A research organization or educational entity wishing exemption from the Federal OSHA standard must have in place a diving program that has developed a diving manual, has a diving ronment. The following phases are included in the pretests: cifically tific control officer Phase fins, 1. 2. to fulfill these requirements for exemption was originally de- The become new and certification procedures. Individuals or organizations wishing information about scientific diving programs Academy or snorkel and in the following sequence: Perform a 75 foot (22.9 meter) underwater swim Perform a 1000 foot (304.8 meter) swim on the Perform a 150 foot (45.7 meter) underwater swim, surfacing for no more than 4 single breaths during the swim. community reflects the effectiveness of current diver training completed within a or side stroke. 3. available. safety record of the research diving to be surface in less than 10 minutes, using the breast veloped at the Scripps Institution of Oceanography in technologies and techniques have is on a single breath. procedures for emergency diving situations. The pro- the 1950's and has been updated since then as — Swimming Pool 15-minute period and should be done without mask, and diving safety board, and has developed gram used by many research organizations 1 This series of activities The 75 underwater swim simulates emergency ascent, except that the exhaling is omitted. The 1000 foot (304.8 meter) surface swim simulates a swim back to the beach. The foot (22.9 meter) a 75 foot (22.9 meter) Underwater Sciences (947 Newhall Street, Costa Mesa, California 92627). As a result of the combined experience of single breaths, simulates surf passage, scientific diving organizations, a set of standards has to been developed before the next wave. should contact the American 7-10 of to ensure that the high level of quality 150 foot (45.7 meter) underwater swim, surfacing for 4 where one has surface, take a breath, and get back under water NOAA Diving Manual — October 1991 Diver and Support Personnel Training The candidates are then required to swim 75 Operational planning, including diver supervision, feet scheduling, and emergency plans; (22.9 meters), dive to the bottom of the pool, recover, and tow a person of similar size 75 feet (22.9 meters). First aid, including CPR; Diving accident management procedures; Phase 2 — Open-Water Test open-water swim involves (304.8 meter) open-water swim and a dive An ocean 1000 foot or other Underwater navigation and search methods, includmethods of locating, marking, and returning to ing a research to sites; the bottom in a depth of at least 15 feet (4.6 meters). Collection techniques, including introduction to This open-water exercise often reveals potential problems sampling, testing, and harvesting systems, tagging, that are not apparent swimming The pool. those screened by Institution of when the candidate swims in a diver training success rate means of these two tests at the preserving, transporting of specimens, and data among recording methods; Photographic documentation, including the use of Scripps Oceanography has been nearly 100 per- cent (Stewart 1987). 7.5.2 for scientific investigations. Curriculum Research diver training should cover dives conducted many in as different environments as possible. Addi- tionally, students should gain experience using a vari- ety of different platforms, such as small boats, ships, piers, docks, and jetties, and should make water entries The curriculum should be tailored to the local area and the particular needs of the researcher. However, the following outline identifies topics that are usually • A in a practical scientific diving course: review of diving physiology and physics as they relate to field operations; • Surface-supplied diving techniques, including tending, communications, capabilities of surfacesupplied diving systems, and emergency procedures; • Small boat handling, including the uses and limitations of small craft as diving platforms, load limits and distribution, securing procedures, minor field repairs, • • legal responsibilities; and securing of research equipment Environmental hazards, such as: Training element equipment maintenance is an important any diving program. Although fatal diving accident statistics show that equipment failure issuance of visual cylinder inspection stickers The cylinder inspection course covers the following in the water; diving in currents, • Reasons • Frequency of inspection; wrecks, and under con- for cylinder inspection; • Types of inspection; • Analysis of cylinder structure and accessories; • Criteria of inspection, e.g., wall thickness, material and valve specifications; Evaluation of cylinder interior and exterior; Use of inspection equipment, Thermal protection problems, including the use of wet suits, variable-volume dry suits, and hot water suits, and the advantages and disadvantages of • hardwire, and acoustic and diver recall systems; — NOAA Diving Manual lights, probes, Detailed inspection sequence (this is an 18-step process describing each step of a cylinder inspection); Diver communication, including diver tending, e.g.. flushing solutions; each; October 1991 The tightly is controlled. • in rarely the course are certified as cylinder inspectors. ditions of limited visibility; and is ience, and premature dive termination. Only trained and qualified personnel should perform maintenance and repair of diving equipment, especially regulators, scuba cylinders, and other life support systems. NOAA and other organizations have instituted a training and certification program for scuba cylinder inspectors. The objective of these programs is to ensure that uniform minimum inspection standards are used at diving facilities. People who successfully complete • as caves, under ice, • in in the cause of death (see Section 19.2), equipment mal- polluted water, blue water, restricted areas such • EQUIPMENT MAINTENANCE topics: Equipment handling, including safe use, field maintenance, and storage of diving and scientific equipment; Underwater rigging, including emplacement, moving, • and 7.6 function does cause near-misses, lost time, inconven- under as many shore conditions as practical. addressed video, movie, and time-lapse photography still, • and The inspection of a minimum of 10 cylinders under the supervision of an instructor. 7-11 « « Page SECTION 8 8.0 General 8-1 WORKING 8.1 Surface-Supplied Diving Procedures 8-1 DIVE 8.1.1 Planning the Dive PROCEDURES 8.1.2 Selecting the Dive 8.1.3 Dressing the Surface-Supplied Diver 8-3 8.1.4 8-4 8.1.6 Tending the Surface-Supplied Diver The Dive 8.1.5.1 Diver Emergencies Ascent 8.1.7 Post-Dive Procedures 8-8 8.1.8 Umbilical Diving From Small Boats 8-8 8.1.9 Basic Air Supply Systems 8-9 8.1.5 8.2 Rates of Air Flow Supply Pressures Search and Recovery 8.4 8-2 8-4 8-5 8-7 8.1.10 8-9 8.1.1 8-10 8-10 8.2.1 Circular Search 8.2.2 Arc Pattern 8.2.3 Jackstay Search Pattern 8-13 8.2.4 Search Using a Tow Bar 8-15 8.2.5 Search Without Lines Recovery 8.2.6 8.3 8-1 Team 8-12 (Fishtail) Search Underwater Navigation Underwater Tools 8-13 8-16 8-16 8-16 8-18 8.4.1 Hand 8.4.2 Pneumatic Tools 8.4.3 Hydraulic Tools 8-20 8.4.4 Electric Tools 8-21 8.4.5 Power Velocity Tools 8-21 8.4.6 Cutting and Welding Tools 8-22 8-18 Tools 8-20 8.5 Maintenance and Repair Tasks 8-23 8.6 Instrument Implantation 8-23 8.7 Hydrographic Support 8-24 8.7.1 Hazards 8-24 8.7.2 Locating and Measuring Least Depths 8-25 8.7.3 Resolving Sounding Discrepancies 8-25 to Navigation 8.8 Wire Dragging 8-25 8.9 Salvage 8-26 8.10 8.11 8.12 8.9.1 Lifting Devices 8-26 8.9.2 Air Lifts 8-27 Diving From an Unanchored Platform 8-27 8.10.1 Liveboating 8.10.2 Drift Diving 8-30 Underwater Demolition and Explosives Underwater Photography 8-31 Photography 8-33 8.12.1 Still 8.12.2 8.12.3 8-33 8.12.1.1 Lenses and Housings 8-33 8.12.1.2 Light and Color 8-34 8.12.1.3 Selection of Film 8-38 Time-Lapse Photography Motion Picture Photography 8.12.1.4 8.13 8-28 8-41 8-42 8.12.2.1 Selection of Film 8-42 8.12.2.2 Procedures 8-42 Special Procedures Underwater Television 8-44 8-44 « i WORKING DIVE PROCEDURES GENERAL 8.0 depths that do not require to shallower This section describes some of the techniques and procedures used by scientific and academic divers engaged in underwater objects, routine underwater of choice for underwater ment of various types to supplied air. This mode is 8.1.1 also called umbilical diving. may in detail.) of any dive depends on careful pre-dive SURFACE-SUPPLIED DIVING planning, which must consider the goals of the dive, PROCEDURES the tasks involved in achieving these goals, environ- The surface-supplied NOAA by 5 Planning the Dive The success 8.1 a lightweight diving outfit describes diver and diving equip- be used. (Section work operations. The diving mode work that requires the diver remain submerged for extended periods of time is maximum protection from pollution, temperature extremes, or gives them mental conditions (both surface and subsurface), the air diving mode is widely used divers and by diver-scientists because the flexibility they need to perform it many different underwater tasks. In surface-supplied div- breathing mixture ing, the diver's surface by means is supplied from the of a flexible hose; thus, divers using mode have a continuous breathing gas supply. The surface-supplied mode is generally used when this divers need to remain under water for an extended period of time to accomplish the dive's objectives. The advantages of surface-supplied diving over scuba diving are that it: personnel needed to carry out the dive, the schedule for the dive, the equipment needed to conduct the dive safely and efficiently, and the availability of emer- gency assistance. Figure 8-2 is a checklist that can be used to evaluate environmental conditions that may affect the dive. For every surface-supplied dive, the dive supervisor should complete this checklist (or one adapted to the specific conditions of a particular dive) before decid- and equipment needs. Different environmental conditions affect members of the dive team ing on personnel differently. For example, divers are generally not affected by surface waves except when entering or exiting the • provides greater safety; • permits dives to greater depths; water; however, divers operating in very shallow waters, • permits divers to stay on the bottom for longer in surf, or in periods; by wave action • • • provides thermal protection (if exceptionally large waves can be affected at the surface. Air temperature and wind conditions at the surface diving in cold water); may have a greater effect on the tender and other permits communication between the diver and the also surface; and surface support personnel than on the diver, because these individuals are provides an unlimited air supply. Another advantage of the surface-supplied mode that it surface conditions. platforms, including piers, small boats, barges, and The disadvantages of this mode, compared with the scuba mode, are: (l) that the umbilical diver's mobility and operational range are restricted by the length of the umbilical; and (2) that a large amount of ships. equipment is required to support umbilical diving. Surface-supplied diving gear includes both deepsea and lightweight equipment. When a diver-scientist needs maximum protection from the physical or thermal environment or when the dive is deep (i.e., to 190 fsw (57 m)), the deep-sea diving outfit shown Figure 8-1 is the diving dress of choice. For dives October 1991 — NOAA Diving Manual more exposed than the diver to is important to remember, how- is can be undertaken using a variety of support in It ever, that the surface crew should be able to operate with maximal efficiency throughout the dive, because reductions in the performance of topside personnel could endanger the diver. Visibility at the surface can affect the performance and safety of the diver and the surface crew. For example, a diver surfacing under low- or no-visibility conditions might not be able to find the support craft. The underwater environment can influence many aspects of a dive, from crew selection to choice of diving mode. All diving operations must consider: • depth; • bottom type; 8-1 ^ Section 8 Figure 8-1 Surface-Supplied Diver in Deep-Sea Dress Helmet Assembly Adjustable ill Exhaust Valve .Jocking Harness Air / Yvr^^rlrfu". ^^Front Communication Jocking Strap W Hip Weight > — Pocket -i Whip Whip Rear Jocking Straps iv*' ^S ii^^oidS. P Thigh Weight Pocket Umbilical Dry Suit Thigh Retainer •Crotch Jocking Strap Calf Weight Pocket , Calf Retainer Boot Safety Straps Boots Source: US Navy (1988) • temperature of the water; ocean, and tidal currents vary with such factors as the • underwater and • tides time of year, phase of the tide, bottom conditions, depth, and weather. Underwater visibility and water temperature also have a visibility; and currents. In addition, the presence of contaminants in the water underwater obstacles, ice, or other unusual environmental conditions can affect planning for some dives. Dive depth must be measured using two different methods before the dive begins. To obtain an accurate (see Section 11), depth profile of the area of the dive, a series of depth measurements must be plotted. Methods of measuring depth that may be used include lead line sounding, pneumofathometer, high-resolution sonar, or shipmounted fathometer. Depth readings on maps or charts are useful for general screening purposes but are not sufficiently accurate to be used to measure dive depths. Samples should be taken of the bottom area of the dive; in tions some in the general instances, in-situ observa- and visibility underwater conditions in major U.S. geographi- cal regions, see Section 10.1. 8.1.2 Selecting The the Dive size of the Team team needed for a surface-supplied number of divers on the dive team, the type of equipment available, the dive's safety dive depends on the requirements, environmental conditions, dive depth, dive mission, and the surface support platform availa- The optimal number of dive team personnel for a and complex surface-supplied dive is six: a dive supervisor, diver, standby diver, tender, standby tender, and timekeeper/recorder. If all members of the team are fully trained, a job rotation system can be ble. large can be made before the dive. Bottom conditions affect a diver's mobility major influence on dive planning. For a detailed description of under water; a maximum mobility, and the diver's stir up so much sediment that visi- used that permits team members all sandy bottom allows ing as divers; this approach allows for movements do not working time and By comparison, working in an area muddy and silty bottom can be dangerous, because diver may become entrapped in the mud and usu- bility is restricted. with a the 8-2 ically efficient. The dive supervisor is responsible for planning, in a aid supplies are available, conducts pre-dive briefings, the surface-supplied scientist-diver The in-water direction and velocity of river, visibility. Currents must be considered in dive planning, whether river or the ocean. maximum thus both logistically and econom- managing all dive operations; the dive supervisor remains at the surface at all times. This individual also determines equipment requirements, inspects the equipment before the dive, selects team members, ensures that emergency procedures and first ally generates sufficient silt to interfere substantially with is to take turns serv- is working organizing, and NOAA Diving Manual — October 1991 Working Dive Procedures Figure 8-2 Predive Environmental Checklist her diving gear complete, good repair, and ready must know both line pull signals and voice signals and must respond to and comply with instructions from surface personnel. Surface is in for use. In addition, all divers Atmosphere Sea Surface Visibility Sea State Wave Sunrise/Set Moonrise/Set Temperature (air) Humidity The standby Action: is required for Height Length bility of the size. It surface- all the responsi- is standby diver to be ready to provide emergency or backup support to the diver any time the diver Current: in is the water. The tender Direction Precipitation standby supplied operations, regardless of Direction Barometer must be as well trained and quali- diver fied as the diver; a the is member of the surface team who is Cloud Description/Cover Velocity responsible for tending the diver while the diver Wind Type the water. Every diver in the water must have a tender. Direction/Force Other: Water Temperature _ • checks the diver's equipment; • checks the • dresses the diver. Local Characteristics Subsurface Once Visibility Depth Underwater: degrees depth at degrees at depth degrees at depth degrees at depth feet at depth feet at depth in the water, the tender takes care of line. In addition, the tender maintains supervisor informed of the diver's progress. All ten- On complex dives, a standby tender The standby tender should be and should be instructed It is in all may be needed. fully trained as a diver of the required duties of the standby tender's job to be ready to tender or to replace him or her at any time. The timekeeper may be dedicated Obstructions: depth at on the assist the depth at is the tender. Bottom Type: Thermoclines: is ders should be fully qualified divers. depth Bottom bottom the diver communication with the diver and keeps the diving feet at feet at and air supply; the diver's lines to ensure that no excess slack or tension Water Temperature: to keeping the diver's time during the job or, on dives involving a Current: limited Direction Marine Source number of dive involve keeping an accurate record of dive sibilities Pattern times and noting dive. Other: Tides: High Water Low Water Ebb Direction On some all of the important details of the dives, the dive supervisor acts as the timekeeper. time / team members, the tender may The timekeeper's respon- also serve as the timekeeper. Life: Velocity time Velocity Flood Direction _ Velocity _ 8.1.3 Dressing the Surface-Supplied Diver Surface-supplied divers use either a diving Adapted from US Navy (1988) a helmet, monitors the progress of the dive, debriefs the divers, prepares reports of the dive, and checks equipment and diver logs at the completion of the dive. diver(s) must be qualified and trained in the equipment and diving techniques needed for the dive. During the course of the dive, the diver must keep surface personnel informed of the progress of the dive, bottom conditions, and any problems (actual or potential). Every diver October 1991 is responsible for ensuring that his or — NOAA Diving Manual mask or and the supervisor and diver must decide whether a dry The in Before the diver enters the water, the tender: Visibility Underwater and Bottom is suit, wet suit, or bathing suit is appro- priate for a particular dive. Factors to be considered when making these choices include: • Personal preference; • Depth of the planned dive; Nature of the work to be performed; • • Length of the planned dive; • Environmental conditions (temperature of the water, speed of current, underwater visibility, etc.); and • Condition of the water, i.e., polluted or clean. 8-3 Section 8 Figure 8-3 Lightweight Surface-Supplied Mask The dressing procedures followed by the diver and depend on the type of dress selected or her tender his Steady Flow Valve (defogger) for the dive. At least one tender assists in dressing a diver wear- ing a lightweight surface-supplied diving system (dry suit) or a wet suit. If a dry suit is to be worn, the diver applies a lubricant to the suit's zipper and then, while seated, inserts his or her legs into the suit. The diver then stands and works both arms into the suit's sleeves. The tender holds the breech ring while the diver performing these procedures. Then the tender: Wraps is 'Dial-a-Breath" "Adjustment knob the harness chest strap tab around the left shoulder strap and presses it into place; Pulls the crotch strap to the front and fastens the weight belt latch; Adjusts the waist belt and shoulder straps and Waterproof secures both rear jocking straps; Inserts thigh Communication Connector and calf weights and secures the (Male) thigh and calf restrainers; Ensures that air is available to the the air supply valve is helmet and that Source: US Navy (1988) opened; Lowers the helmet into place on the diver's head and aligns it with the lower breech ring lugs; Presses the quick-release locking pins, slides them and ensures that all pins are locked; Positions the umbilical and whips under the diver's left arm and secures them; Performs a communications check; and into place, stage or ladder. diver and to prevent a As a hand on fall. the diver enters the water, the tender pays out the umbilical at a steady rate, being careful to avoid sharp edges. Throughout the dive, the tender out of the Establishes the appropriate air flow. The tender must always keep the diver's lifeline close to the helmet to steady the line; at the must keep slack same time, the tender must be careful not to pull the line taut. Maintaining approxiIf a a lightweight mask (Figure wet suit or bathing suit, 8-3) is to be used with dressing procedures are simpler than those described above. For divers wearing a wet suit or a bathing suit, the tender assists the diver to perform the following steps: • Don • Place the lower breech ring with neck the harness; dam over the mately 2 or 3 feet (0.7 to 1 m) of slack on the line permits the diver the right degree of freedom and prevents him or her from being pulled off the bottom by currents or by the movement of the support craft. Too much slack in the line interferes with effective line communication between the diver and tender and increases the likelihood of line fouling. Throughout the diver's head; • Secure the ring to the jock strap; and • Place the helmet on the diver's head and secure any line-pull signals Figure 8-4 shows a surface-supplied diver dressed and in a wet from the diver. If an intercom it. system ready to dive dive, the tender continuously observes the descent line and monitors the umbilical to receive suit. is not in use, the tender periodically signals the diver (using line pulls) to ensure that the diver's condifails to respond to two pull must be treated as an emergency and the dive supervisor must be notified immediately. tion is good. If the diver signals, the situation 8.1.4 Tending the Surface-Supplied Diver is the dive team member in closest com- The tender munication with the diver during the dive. Before the dive begins, the tender checks the diver's diving dress, paying particular attention to the valves on the helmet, the helmet locking device, the helmet seal, and the harness. The tender then dresses the diver and helps the diver to position himself or herself on the diving 8-4 8.1.5 The Dive Once the diver is dressed and ready for the dive, the tender helps the diver to prepare for water entry. The entry technique used depends on the staging area or type of vessel involved in the operation. If a stage used for diver entry, the diver should stand or NOAA Diving Manual sit is squarely — October 1991 Working Dive Procedures Figure 8-4 Surface-Supplied Diver In Lightweight Mask and Wet Suit The diver must equalize pressure • sinuses during descent. When both ears and in equalization is not pos- must be terminated. sible, the dive • If descending in a tideway or current, the diver should keep his or her back to the current so that he or she will be forced against the descent When • line. the diver reaches the bottom, the tender should be informed of the diver's status and the diver should ensure that the umbilical assembly is not fouled in the descent line. • If necessary, buoyancy and air flow should be reg- ulated before releasing the descent line; adjust- ments made to air control valves should be in small, cautious increments. • The diver should attach a distance line one is used) and should then proceed to the work area. A distance line should be used when (if visibility is extremely poor and the diver cannot see the descent from a distance. line • After leaving the descent line, the proceed slowly to conserve energy. for divers to carry diver should It is advisable one turn of the umbilical hose in the hand. Source: US Navy (1988) • The diver should pass over, not under, wreckage and obstructions. • If on the stage platform and maintain a good grip on the rails. If the diver makes a moving against a current, it may be necessary assume a crawling position. for the diver to jump or roll entry into the If the • water, he or she must maintain a grip on the face mask etc., while the tender maintains sufficient slack on the line and diver the umbilical hose at the entrance to the confined space. When the diver is positioned for descent, the follow• various members of the dive team. The tender must constantly inform the diver bottom time. The diver should be notified minutes The diver should adjust his or her buoyancy, Whether the diver is weighted neutrally negatively will depend on the dive's objectives. necessary. • The tender should be made in the air supply fittings and also should look for or suit must before the diver's descent. The tender should check for any leaks air bubbles. No diver should dive with malfunctioning equipment. The tender should ment • is also re-verify that all a few advance of termination so that the task can be completed and preparations if re-verify that the air supply are functioning properly. If not, corrections in of the made for ascent. or system, helmet (or mask), and communications • required to enter wreckage, tunnels, air hose. ing procedures, as appropriate, should be followed by • is a second diver should be on the bottom to tend If the diver experiences rapid breathing, panting, or shortness of breath, abnormal perspiration, or an unusual sensation of warmth, dizziness, or fuzzy vision, or become cloudy, there is probably carbon dioxide in the helmet. To get rid of the helmet ports have an excess of this excess, the air flow in the helmet should be increased immediately by simultaneously opening the air control and exhaust valves. equip- functioning satisfactorily. The diving supervisor should give the diver per- 8.1.5.1 Diver Emergencies mission to descend. • The line. diver should descend The descent down rate used a descent or "shot" depends on the diver; should not exceed 75 ft/min (22.9 m/min). however, it The supply should be adjusted for breathing air — NOAA A surface-supplied diver's umbilical may become fouled in mooring lines, wreckage, or underwater structures, or the diver may be trapped by the cave-in of a tunnel or the shifting of heavy objects under water. In ease and comfort. October 1991 Fouling Diving Manual 8-5 Section 8 such emergencies, surface-supplied divers are in a better position to survive than scuba divers, because they have a virtually unlimited air supply and can communicate with the surface, both of which facilitate may rescue operations. Fouling result in fatigue, expo- and prolonged submergence, and sure, sitate it may also neces- an extended decompression. Divers who are fouled should: • Remain calm; • Think • Describe the situation to the tender; • Determine the cause of fouling and, if possible, and Be careful to avoid cutting portions of their umbilical themselves are unsuccessful, divers should call for the standby diver and then wait calmly for his or her arrival. Struggling make actions only remaining and other panicky the situation worse by using up the supply at a faster rate. air After surfacing, blowup victims should not be allowed resume diving. If a diver who has experienced a blowup appears to have no ill effects and is still within to the no-decompression range prescribed by the tables, m) and decompress for the amount of time that would normally have been required for ascent from the dive's working he or she should return to a depth of 10 feet (3.0 The diver should then surface and dress, after which he or she should be observed for at least an hour for signs of delayed-onset air embolism or decompression sickness. Blowup victims who are close to the no-decompression who require decompression should first be recompressed in a chamber and then be decompressed in accordance with surface decompression procedures; if the available surface decompression tables are not adequate, the victim should be recompressed in a chamber to 100 feet (30.5 m) for 30 minutes and then be treated in accordance with U.S. Navy Treatment Table 1A (see Appendix C). If no chamber is available, conscious viclimit or assembly when using their knife. If efforts to clear losing depth. clearly; clear themselves; • method of ascent should never be used because control of the rate of ascent can have fatal consequences. tims should be treated in accordance with recompression Blowup Blowup the uncontrolled ascent of a diver from is depth; this is a hazard for divers using either a closed dress (deep-sea or lightweight helmet connected to a dry suit) or variable-volume dry suit equivalent). (UNISUIT® Blowup occurs when the diving dress becomes overinflated or the diver loses hold of the botor descending line and is swept to the surface. During blowup, the diver exceeds the rate of ascent (25 ft/min (8 m/min)) that must be maintained to be decompressed successfully at the surface. Accidental inversion of the diver, which causes the legs of the suit fill with air, also may result in uncontrolled blowup. Accidental blowup can cause: • • • Cerebral gas embolism; Decompression sickness; and/or (if the diver's head Physical injury strikes an object, such as the bottom of a ship or platform). Before descending, the diver must be certain that all exhaust valves are functioning properly. The diving suit or dress should fit the diver well to avoid leaving exces- sive space in the legs in which air can accumulate; air in the legs of the suit presents a serious hazard, particularly with variable-volume suits. Divers must be trained under controlled conditions, preferably in a swimming pool, in the use of all closed-type diving suits, regardless of their suits. Some previous experience with other types of divers have attempted to use a technique called "controlled 8-6 blowup" . unconscious victims should be handled according to the m recompression table in Appendix C that is designed for cases of air embolism or serious decompression sickness. or or suit tom to procedures for interrupted or omitted decompression; for ascent; however, this Loss of Primary Air Supply Although losing the primary quent occurrence air supply is an infre- surface-supplied diving, in it does occasionally occur. In the event of a primary air supply malfunction or loss, the panel operator should switch immediately to the secondary supply, notify the tender and diver, and call for the termination of the dive. (Secondary air supply systems on the surface are discussed in Sections 4.2 and 14.5 for both air compressor and high-pressure cylinder air supplies.) The use of self-contained emergency air supplies in surface-supplied diving has significantly reduced the hazard associated with primary air supply failure. In an emergency, a diver equipped with such a supply can simply activate his or her emergency supply and proceed to the surface. Divers faced with the loss of their surface supply should close their helmet free-flow valves to conserve air, and the surface crew should be alerted soon as it develops. If, because of to the situation as fouling, the diver is forced to cut the air supply line, a check valve incorporated into the reserve manifold The diver a must immediately terminate the dive if it is necessary to switch to the emergency supply; under no conditions should the diver attempt to complete the work task. fl will prevent loss of the reserve air supply. NOAA Diving Manual — October 1991 Working Dive Procedures when self-contained emergency the primary air supply fails If without a a diver is diving air supply, the Loss From View of Descent or Distance Line Occasionally a diver diver can drop his or her weight belt (without removing line or lose the mask) and then ascend to the surface, exhaling tance line throughout the ascent to prevent air embolism. A diver will lose sight of the descent contact with the distance lost, is line. If the dis- the diver should search carefully within arm's reach or within his or her immediate with a fouled hose should release his or her weight belt vicinity. If the and harness (or harness attachment) and then remove the mask by grasping it and pulling it forward, up, and over the head. The surface-support team should han- the tender should be informed and should haul in the dle a diver who way surfaces in this blowup emergency, because as a pression sickness is in the same manner embolism or decom- air a possibility. water is less than 40 feet (12.2 m) deep, umbilical assembly and attempt to guide the diver back to the may be hauled a short distance off the bottom. descending line. In this situation, the diver contact with the descent line is When regained, the diver should signal the tender to be lowered to the bottom again. In water deeper than 40 feet (12.2 m), the tender should guide the diver to the descent line Loss of Communication or Contact with the Diver contact with the diver If is lost, the following proce- in a system- atic fashion. dures should be implemented: • If intercom communication lost, is the tender should immediately attempt to communicate with the diver by • line-pull signals (see is it generally best to terminate the dive so that the problem can be resolved and the dive plan revised. • If the tender does not receive an immediate line- pull signal reply an especially serious hazard for divers from the diver, greater strain hull of a ship. A diver falling off a diving stage or work platform wearing such equipment to be injured is much more likely than a diver falling a greater distance in open water. The principal danger from falling is the sudden increase in pressure, which may not be compensated for by the overbottom pressure of the air supply; this could result in helmet or mask squeeze. The diver and tender must therefore always be alert to the possibility of a fall. Should the diver start to fall, the tender should take an immediate strain on the be sent again. Considerable resistance to the ten- umbilical assembly to steady the diver. der's pull may fouled, in which case a standby diver should be If the indicate that the umbilical line is it is still attached to the diver but continues to receive no reply to line-pull signals, it is is air pressure should If a tear develops in a variable-volume suit, the dive tating to a diver. If a closed suit with the helmet is available, or if for some considered unwise to use one, the diver available to assist with the ascent. — NOAA in the water. Diving Manual is torn in a fall, the diver should remain in an upright position and ascend to the surface at a safe rate of ascent. Ascent When the diver's bottom 8.1.6 time has expired or the task has been completed, the diver should return to the is The following procedures should be used; all times to enter the water when divers wearing variable-volume dry suits are attached ascent line and signal the tender to prepare for ascent. It thus essential that a standby diver be ready at October 1991 and the effect of water entering the suit can be severely debili- must be pulled to the surface at a rate of 60 feet (18.3 m) per minute or less, and the tender and the dive team should be prepared to administer first aid and recompression as soon as the diver surfaces. If the diver is wearing closed dress or a variable-volume dry suit, pulling him or her to the surface is likely to cause blowup unless another diver it, be increased slightly to prevent water leakage. standby diver should be dispatched no standby diver reason faceplate does crack, however, the diver should be terminated immediately because the chilling to immediately. If If the should continue to wear be unconscious. In the diver should be this event, the assumed The likelihood of a faceplate being cracked during a fall when a modern helmet is being used is relatively small. tender feels sufficient tension on the line to conclude that • is should be taken on the line and the signal should dispatched as soon as possible. • Falling using deep-sea or helmet equipment to work on the Section 14.2). Depending on diving conditions and the arrangements made during dive planning, the dive may either be terminated or continued to completion (using line-pull signals for communication). In research diving, Falling • The tender should pull in any excess umbilical line and exert a slight strain on the line; he or she 8-7 Section 8 • should then exert a slow and steady pull at the divers are chilled. prescribed rate (generally 60 ft/min (18.3 m/min)); any equipment defects noted during or after the dive, start a timer on the surface and should then monitor this timer (along with the and defective equipment should be tagged for corrective maintenance. The divers should then be debriefed Divers should establish their and the log completed. own standard of care for their masks, depending on the conditions of use. For example, using a mask in fresh water requires different maintenance procedures and The tender should pneumofathometer) to control the diver's ascent rate; • diver controls his or her buoyancy by using The either a buoyancy compensator or adjusting the air in his or her closed- or suit, • • variable-volume suit must be careful not (the diver to overinflate the which could cause an accidental blowup); line cleaning frequencies than are required used in seawater. seawater, the exterior of the a mask is When mask should be diving in rinsed in microphones. The interior of the mask should then be wiped clean with a cloth or sponge. An alcohol solution is useful for cleaning and disinfecting the oral-nasal or diving supervisor should inform the may be required for When decompression is mask. (Inhibisol® or similar solvents should not be completed, the tender assists is stored, even Some masks 8.1.7 Post-Dive Procedures if the storage time is very short. should be placed in the face-down posi- water to drain from the face seal. some types require additional maintenance. For example, the interior of masks that are fitted with a cold-water hood are difficult to clean and dry unless the hood is first removed. After the hood is removed, the mask should be turned inside out and the water in the open-cell foam face seal should be squeezed out. The interior of the hood and mask should be dried tion to allow Divers should be helped from the water and should then be assisted by surface-support personnel in removing their equipment. harm the acrylic port.) The mask should be completely dry when the used, because they will interior of the mask The following procedures are recommended: Remove Remove the weight belt; • the helmet and secure the air flow valve; Unbuckle and remove the emergency backpack; • Remove the neckring assembly; • Unbuckle and remove the jocking Masks of completely before reassembling. Installing a zipper the back of the hood simplifies maintenance because in it reduces the number of times the hood has to be removed. belt. Close the supply valve and vent the primary air maintenance and repair masks in accordance with the manufacturer's instructions and the service man- hose; ual supplied with each mask. Monthly If the • when of underwater activity also The tender the diver to board the support platform. • The type fresh water after each dive, taking care not to flood the long decompressions); • and tenders should report during ascent; requirements (a diving stage • divers influences maintenance requirements. The diver should continuously hold onto the diver well in advance of his or her decompression • The diving system is not to be used again that day: (or between-dive) should be performed on all Close the emergency air cylinder valve, open the reserve air valve to vent the line, and close the 8.1.8 Umbilical Diving From Small Boats reserve air valve again; • • • Disconnect the primary air hose from the emer- gency manifold; Disconnect the hose from the helmet inlet and disconnect the communication cable; Place the helmet in an upright position, rinse external surfaces with fresh water, and wipe the interior, then wipe • it if necessary, with a them dry; clean damp sponge and dry; Rinse the jocking belt in fresh water and hang it up to dry. The umbilical diving is fixed platforms, the readily to small boat small boats, i.e., at m), a bank of high- is usually used to supply breathing which enables the team to operate without an air compressor and its accompanying bulk and noise. The pressure cylinders air, number and size of the high-pressure cylinders required depend on the size of the boat and on operational requirements. For small boats, two or more sets of divers should be observed for any signs of sick- standard twin-cylinder scuba tanks can be connected and warming proce- by a specially constructed manifold that is, in turn, connected to a high-pressure reduction regulator or ness or injury caused by the dive, dures should be 8-8 Although most surface-based conducted from large vessels or umbilical system can be adapted operations. When working from depths of 16 to 30 feet (4.9-9.1 commenced as soon as possible if the NOAA Diving Manual — October 1991 Working Dive Procedures The umbilical small gas control panel. is then con- nected to the pressure side of the pressure reduction In larger boats, air unit. may be carried m3 240- or 300-cubic foot (6.8 or 8.5 in a series When is of • Of specified purity (see Table Of adequate volume; • At the proper pressure; and • ) high-pressure Regardless of the cylinder configuration used, cylinders. cylinders must be secured properly, and the valves, all • manifold, and regulator must be protected to prevent personnel and equipment damage. The umbilical may the boat. For the convenience of the tender, the is is: 1 5-3); Delivered at a sufficient flow rate to ensure ade- quate ventilation. Regardless of the type of system, be coiled on top of the air cylinders or in the bottom of municator properly configured, either of these air sources able to supply breathing gas that is it imperative that it be good in com- repair, be manned by serviced at regular intervals, and be trained personnel. generally placed on a seat or platform. Communications equipment must be protected from Air compressors are discussed When in more detail in Sec- weather and spray. Because small boats can only be tion 4.2. used to support shallow water work, the umbilical from diving operations incorporates an on-line air compressor, the boat to the diver m) 45.7 in depths to length. less It is is the air supply system for surface-supplied usually 100 to 150 feet (30.5- the general system configuration generally wise to limit diving shown than 100 feet (30.5 m) when working from a small boat. When Figure 8-5. in similar to that is surface-supplied diving operations utilize a high-pressure cylinder system for diver air supply, the general system configuration used The diving team for a surface-supplied dive from a is the one shown in Figure 8-6. small boat usually consists of a diver, tender, and standby diver. The tender, who a qualified diver, is also serves as the supervisor on such dives. If properly 8.1.10 Rates of Air The qualified, all personnel can alternate tasks to achieve maximum The standby diver second umbilical and mask or, operational efficiency. may be equipped with a as frequently the case, be equipped with scuba; he or is to which rate at Flow air must flow from the air supply- the diver depends on whether the breathing appara- mask) is operated in a free-flow or demand mode. With free-flow equipment, the primarytus (helmet or she should be completely dressed and capable of don- requirement of the air supply system ning scuba and entering the water capacity (in acfm) that will provide sufficient ventila- ute. A in less than a min- standby using scuba should be fitted with a quick-release lifeline (readily releasable in the event of entanglement). Some munication cable as a divers use a heavy-duty lifeline, com- which allows the standby- diver and tender to stay in communication. This line also constructed so that it may be released readily is in Many divers consider high-pressure cylinder air supply systems safer and more dependable than systems incorporating a small compressor and a volume or receiver tank, and some divers prefer to have a small tank incorporated into the system to provide air for surfacing in an emergency. Most experts agree that a diver should carry a small self-contained emergency scuba tank for use in the event of primary system failure. An emergency supply of this type is mandatory when a diver will be working around obstructions or inside submerged structures. 8.1.9 depth to prevent the carbon dioxide tion at mask or helmet work levels By ensuring gencies. liters) will not all circum- exceed 2 percent. To compute inspired C0 2 , the following equation should be used: R = 6(Pa)(N) where R = ventilation flow rate in scfm; lute pressure at working depth in ATA; Pa N = = abso- number of divers to be supplied. Example: What ventilation rate would be required for two divers using lightweight helmets at 80 fsw (24.4 R = R = R = For 6(Pa)(N) 41.04 scfm demand equipment, the air requirement for res- maximum Air compressors; and piration • High-pressure cylinder systems. flow rate under severe work conditions. is based on the m)? 6(3.42)(2) • Diving Manual capable of is under the ventilation rate necessary to control the level of basic types of air supply systems used for — NOAA level in the stances, divers can be reasonably certain that the inspired surface-supplied diving are: October 1991 have a limits at that the apparatus supplying at least 6 acfm (170 Basic Air Supply Systems The two from exceeding safe it normal and during extremely hard work or emer- carbon dioxide case of entanglement. that is instantaneous (peak) The maximum 8-9 Section 8 Figure 8-6 Typical High-Pressure Cylinder Bank Air Supply Figure 8-5 Major Components of a Low-Pressure Compressor-Equipped Air Supply System System Supply Air to Divers Moisture Back Separation .Pressure ^i+J Regulator LP Compressor /Valve / D*0— W ^^^^ Air Intake to J I~0- Pressure Regulator (if req) Pressure Regulator From Secondary Source Volume Tank US Navy Source: Divers "C£<|_ Manifold (1985) Drain 'Valve | Drain regulators). Valve The supply pressure must always exceed the ambient pressure at the working depth to provide a Source: US Navy (1985) safety factor in case an accidental rapid descent from below the planned working depth must be made. When instantaneous flow is demand but not a continuous rather the highest rate of air flow attained during the inhalation part of the breathing cycle. A diver's air using a free-flow mask or lightweight helmet, a hose pressure of at least 50 psi water less than 120 fsw (36.6 is m) required for dives in in depth, and a pres- sure 100 psi greater than ambient pressure is necessary requirement varies with the respiratory demands of the work level. Consequently, the rate at which compressed air is consumed in the system is significantly lower than the peak inhalation flow rate. for depths exceeding 120 fsw (36.6 m). In addition, a Computing the rate of flow that the air supply system must be able to deliver for demand breathing equipment is essentially the same as calculating the weight helmets. consumption rate at loss through the valves of at least 10 psig should be anticipated. Simple calculations give the supply pres- sures necessary for most free-flow For depths less light- than 120 fsw (36.6 m): Ps depth (see Section 14.3). masks and = 0.445D + 65 + Pj = supply air pressure in psig; D = depth in = absolute hose pressure (50 psi + 14.7 psi); fsw; 65 = pressure loss in system. and Pj where P s Example: What rate of flow will a diver require using a demand mask and doing moderate work at 75 fsw (22.9 m)? For depths greater than 120 fsw (36.6 m): Cd = Cd = Cd = RMV (Pa) acfm) (3.27 3.6 scfm (1.1 For demand equipment, the rate of ps ATA) where 115 air flow = = 0.445D + 115 + P; absolute hose pressure (100 psi + 14.7 psi). must meet or exceed the diver's consumption rate at depth. 8.2 8.1.11 The Supply Pressures supply system must be capable at SEARCH AND RECOVERY Search techniques all rely on one common element: the times of adoption and execution of a defined search pattern. delivering air to the diver at a pressure that overcomes The pattern should commence at a known point, cover a known area, and terminate at a known end point. Search patterns are implemented by carrying out search sweeps that overlap. To be efficient, the overlap air all the water pressure at the working depth (overbottom pressure) and the pressure losses that are inherent in any surface-supplied diving system (hoses, valves, and 8-10 NOAA Diving Manual — October 1991 Working Dive Procedures Table 8-1 Wind Speed and Current Estimations should be minimal. The initial step in a search is to define the general area and the limits to be searched. If Wind Speed, Wind Current, being conducted to locate a specific object, knots (m/s) miles/day (km) the search the last is known position of the object is the starting open 1-3 (0.5- 1.5) 2 (3.2) sea resulting from sea and wind currents, the local 4-6 (2.0- 3.0) 4 (6.4) 7-10 (3.5- 5.0) 7 (11.3) 11-16 (5.5- 8.0) 17-21 (8.5-10.5) 16 (25.8) 22-27 (11.0-13.5) 21 (33.9) 28-33 (14.0-16.5) 26 (41.9) The point for defining the search area. wind condition drift in the time the object was at the lost, and the leeway (movement through the water from the force of the wind) should be studied. Sea currents can be esti- mated for a particular area using current NOAA Tidal 11 (17.7) Current Tables and Tidal Current Charts and the U.S. Navy's current Atlas of Surface Currents. Wind currents can be estimated using Table 8-1. The leeway generally to 10 percent calculated at is Adapted from of the wind speed, depending on the area of the object NOAA (1979) exposed to the wind and the relative resistance of the The object to sinking. direction of leeway is downwind, made around sions are 40 percent off the wind vector. Calculation of the value is and direction of leeway can be implemented using a variety of patterns, depending on the search equipment, visibility, or number highly subjective for objects is that float or resist sinking; however, wind velocity is or the object leeway has if the average relatively low (under 5 knots (2.5 m/s)), heavy enough is to sink rapidly, the or no effect on the calculation of a little the datum except for boats that have a tendency to drift up to located. Searching the area point until the object around the datum point of search vehicles involved. Systematic searching is the key to success. A good search technique ensures complete coverage of the area, clearly defines areas already searched, and probable location. After the vectors of water current, wind current, and remaining to be searched. The visibilibottom topography, number of available divers, identifies areas leeway have been added vectorially and applied to the ty, known position of the object, a datum point is defined. The datum point is the most probable position of the object. Once the datum point has been defined, the search radius around the datum point is selected. The search radius, R, is equal to the total probable and error of position plus a safety factor, as defined by the of the ship's position by normal surface survey meth- following formula: ods. This last size of the object(s) to in selecting the best be located are prime factors method for a particular search. There are two acoustic approaches to underwater object location. The first is to traverse the area being searched with a narrow beam fathometer, keeping track approach is suitable for returning to the known object that has high acoustic relief position of a R = radius and = safety factor (between C = total probable error k and 1.5) is When receiver unit R = + k)C (1 total probable error is a mathematical combination of the initial error of the object's position (x). the navigation error of the search craft (y), and the drift error (d e ). The drift error is assumed to be one-eighth of the total drift. The total probable error, C, is: C = (d e : +x 2 +y 2 )'/2 mount. The using side-scan sonar, a transponder is towed either from the surface or a left and submersible. Acoustic beams are broadcast right, The such flat area, second acoustic method involves the use of side-scan sonar. where located in an otherwise relatively as a wreck, significant rock outcrop, or a and the signals received are processed to present a picture of the bottom on both sides of the transponder- receiver unit. Approximate object mined by knowing the position can be deter- ship's position, heading, and speed, and the approximate position of the transponder- receiver unit with respect to the ship. Onboard microprocessors necessary to produce to control the optimum range/gain display contrast are Each factor included in the total probable error is somewhat subjective. Selecting conservative values has the use of microprocessors simplifies the task of the the effect of enlarging the search radius; sometimes, a observer and increases the effectiveness of a search. If small search radius October 1991 is selected, — NOAA and repeated expan- Diving Manual beginning to replace manual adjustment of the gain; more precise determination is necessary, one of the 8-11 Section 8 Figure 8-7 Circular Search Pattern acoustic surveying methods described in Section 9.1.3 ,, —Descending — Line If* can be used. Underwater object location using acoustechniques involves divers only after the object has tic been detected. The following diver search techniques have been useful for such purposes. ^ , Marker Line M7==4s= ==_-L rft. is is the circular search technique is is is reason- recommended. Under the least potential for entanglement. to ^ " /AD V be made First Search Circle Weight IA ^-^«_ ^>v small, use of such favorable conditions, a floating search line is anchored to the bottom or tied with a bowline around the bottom of the descent line and is used to sweep the area. To determine when a 360-degree circle has been made, a marker line should also be laid out from the same anchor as the search line. This marker line should be highly visible and should be numbered with the radial distance from the anchor. Where current is noticeable, the marker line should be placed in the downcurrent position so that the diver always commences the search from the position having is J J ==:== free of projections, good, the object to be located ably large, and the area to be searched one circle SS Search In conditions where the bottom the visibility VwTT^ \ ^V 8.2.1 Circular j , When more Search Line Descending Line Anchor Second Search Circle Courtesy Skin Diver Magazine Figure 8-8 Circular Search Pattern for Two Diver/Searchers than with tethered divers, the direc- changed tion of travel should be at the end of each rotation to prevent the possibility of fouling lines. The many circular search has modifications, depending on the number of divers and the thoroughness required. The standard technique is to station one or more divers along the search line close to the center of the search The marker line can be used to assign precise The divers hold the search line and swim in a area. (A) distances. marker line, which ensures 360 degrees has been covered. The divers increase the radius for the next search, moving out a distance that permits good visual coverage. This procedure is continued until the outermost perimeter is circle until they return to the that a full reached (see Figure When Previously Searched Area 8-7). two divers are searching, search effectiveness can be increased by having one diver hold the circling line taut and swim the outside perimeter of the area to be cearched while another diver sweeps back and forth along the taut circling line. As shown in Figure 8-8A, bounded by the outside diver's path. The search starts and finishes at the marker line. The search may be extended by the pattern shown in Figure 8-8B, in which case the circling line is marked at the point where the outside diver was previously stationed. The outside diver then moves to a new position, farther out on the circling the line, first search will cover a and the inside diver full circle sweeps back and forth between the marker and the outside diver's 8-12 new position. Posi- Source: tions may be changed become fatigued. NOAA (1979) at regular intervals if the divers Changing positions can be done at the end of each sweep by having the outside diver hold NOAA Diving Manual — October 1991 i Working Dive Procedures moving out one position after visibility length; the other diver then moves outside, taking up his or her murky water, using a weighted line ble; if the lost object moving line, a pull shaped so that is on the secured with a descending line in the for a circular search. same The is conducted diver descends to the bottom (using a weighted line, be advisa- necessary) and searches the immediate area. After snag the will it line will tell the diver that the object has been found. may if reporting to the surface, the diver again descends, going downstream to the extended length of the At Circular search techniques also is manner described above may position for the next sweep. If the search in diver this point, the diver be used for arc-type swing. begins moving sideways line. an in As the diver circles in the pattern, he some resistance on the upward swing of diving through the ice in waters that have no current, or she will feel such as inland lakes and quarries. The following pro- the arc. cedure has been used successfully by the Michigan State Police Underwater Recovery Unit (1978). When who pulls in the line the distance of the diver's visibility. The diver then swings back along the bottom in the the ice covered with snow, a circle is formed is the in snow, using the under-ice entry hole as the center When this occurs, the diver signals the tender, opposite direction until he or she again meets the resist- ance of the current. The pattern repeated until the is the snow indicates the area being searched and the approximate location of the diver who is searching back at the original starting point. This pattern can also be used in open water, including rivers and lakes, and can be conducted from bridges, boats, and off the shore. The fishtail technique is shown in under the Figure 8-10. pivot point. The radius of the circle determined by is The the length of line used to tend the diver. ice. within the of the search If the object first procedure only one diver, with a The backup entering the hole, the diver line, not recovered is and the other end formed on the is is is in The held by the tender. diver If the object surface and describes the underwater conditions. The diver then proceeds just under the ice to the full length With the of the line (approximately 75 feet (25 m)). use of rope signals, the diver begins circling, keeping the line taut and staying about 6 or 8 inches (15-20 cm) below the ice. After the diver completes one circle without encountering any resistance, the tender signals the diver to descend to the bottom. With the line taut, the diver begins the first circle on the bottom. After the diver completes one circle, the tender him pulls or her to a The (within the limits of visibility). searching in a second circle, until the diver again After reaching the general vicinity of the object, the diver standing by; before secured by one end of the not found directly below, the diver returns to the and variation on the arc pattern search can be used to relocate objects in waters with fast-moving currents. diver searches large areas of the river bottom by swinging search of an object will go directly below the hole nals the diver A is circular pattern involves and make a search of the immediate area. is sur- continued until the complete is area has been searched. in on marked-off area, a second circle that slightly overlaps the last circle face. This circle diver diver reaches the hole. is repeated If the diver's rudder, allowing the current to force bottom in right (or left) until the line repeated; otherwise, the standby diver takes over and a second is becomes swims taut. to the The diver then turns onto his or her right side, grasps the line with the right hand (both hands are needed very in strong currents), and stiffens his or her body, turning at an oblique angle so that the current sweeps it it rapidly As the arc slows, a conventional swimming assumed and the diver swims upstream and shoreward. When swimming against the current becomes to the left. position is hand, turns on his or her left side, and repeats the procedure in reverse mode. tom, the diver As progress slips is made across the bot- backward along the making larger and larger arcs. The depends on current velocity and line, gradually size of the arc line length. If the up the the pivotal point, relocates the anchor, and line to standby diver initiating the search, the diver has slack in the line and ond hole is across the river it When alternating directions. object of search cut in the ice and the procedure attached to a heavy pivotal tom, or a creeper. The diver's body can be used as a physical condition continues to be satisfactory, a secis line difficult, the diver shifts the line to his or her left sig- new location commences and the pattern widening arcs from a object, such as an anchor, a stake driven into the bot- is not found, the diver returns begins again. designated. Figure 8-9 illustrates this through-the-ice search technique. 8.2.3 Jackstay Search Pattern In the jackstay search pattern, a rectangular search 8.2.2 The Arc Pattern (Fishtail) Search October 1991 in Buoy is used to perform lines run from the bottom anchor weights to the sur- water that has a current. The face, and a ground arc pattern search technique an under-ice search and buoyed (see Figure area — NO A A is Diving Manual laid out line is 8-11 A). stretched along the bottom 8-13 Section 8 Figure 8-9 Circular Search Pattern Through Ice Courtesy 8-14 NOAA Diving Manual Clifford Ellis —October 1991 Working Dive Procedures Figure 8-10 Arc (Fishtail) Search Pattern B. Search A. in Offshore Search Waters with Currents Courtesy Clifford Ellis between the weights. The divers conducting the search metal bar 4 to 10 feet (1.2-3.0 m) long that permits two descend on the buoy divers to be towed behind a boat (liveboating). and search along the ground line, beginning at one of the anchor weights. When the searching diver reaches the other anchor weight, the weight is moved in the direction of the search. The distance the weight line moved depends on weight is moved the is visibility; if area to be searched is marked The off with four diving flag buoys, one at each corner, to form a square or rectangle. The distance between size of the area to the buoys depends on the be searched and the maneuverability distance the of the boat. After the buoys are in place, the divers searching diver can comfortably see as he or she swims grasp the tow bar and are pulled parallel to two of the visibility good, the is along the line. If visibility is poor, the line only as far as the searching diver can reach. is moved The searching buoys slow rate of speed. After the divers have at a passed the last buoy, the boat is brought about through swims back toward the first anchor weight along the ground line (Figure 8-llB). The length of the ground line determines the area to be covered. The jackstay search pattern is the most effective search the center of the square and parallel to the buoys. technique then be diver then 8.2.4 in waters with poor visibility. Search Using a Tow Bar The tow-bar partem is similar to the aquaplane illustrated in Figure 8-21. October 1991 — NOAA It method involves the use of a Diving Manual second pass is made along away. This pattern is continued until the buoyed area has been searched completely. moved A the buoys, one boat width Two to the far side of the of the buoys can second set of buoys, forming another square. This technique is shown in Figure 8-12. (The procedures and safety precautions associated with liveboating are described in Section 8.10.1.) 8-15 — \ Section 8 Figure 8-12 Searching Using a Figure 8-11 Jackstay Search Pattern 6 Rectangular Search Tow Bar t ^\ Buoy Buoy /" N^Buoy ( BuoyV ' ' ' ~~~—~rr^ \.Buoy |.C J Buoy J ''^ I | ' ' ; Courtesy ' J I Source: NOAA Diving 8.2.6 Search Without Lines When conditions are such that 8.2.5 search lines cannot be used, a search can be conducted using an underwater compass. There are many search patterns that will ensure maximum tern important. Divers should use the cardinal points is N, E, coverage; however, simplicity of pat- W — and S, the length of a side intervals or 50 kicks —and Clifford Ellis Pnjgram —one-minute should turn the same way each time. Recovery The method chosen to recover a lost object depends its size and weight. Small items can be carried on directly to the surface by the diver, while larger items require lifting devices (see Section 8.9.1). is used, the diver ment must attach When lifting straps to the item being recovered. A a lift and equip- line that is longer than the depth of the water being searched and that has a small buoy attached should be carried to the spot to mark the located object. In addition to observing the usual safe diving practices, divers conducting searches should consider the following: • • When plastic-coated steel wire is used as a line marker, a small pair of wire cutters should be carried to permit escape from entanglement. To prevent line fouling when two tethered divers are used in search patterns, one should be designated as the inside diver; this diver always remains under and inside the position of the other tethered When At UNDERWATER NAVIGATION present, all readily available diver navigation or positioning systems rely on surface position for their origin. If navigational or geodetic positions under water were used, the origin would have to be extrapolated, which would introduce an additional margin of error. Recently, acoustic telemetry techniques, which use microprocessor-controlled methods, have been applied to diver. • 8.3 advisa- diver navigation. These systems can be used to track ble to use contrasting materials for radius, bound- from the surface and to guide them to particular Newer methods will allow divers to take the system along to monitor their own position (Woodward 1982); however, dead reckoning is still the most common form of underwater navigation. This procedure has a long ary, untethered divers are involved, and distance of a diver lines to becoming lost. it is decrease the possibility Polyethylene line pro- vides a good contrast to plastic-coated stainless steel wire 8-16 and is recommended for boundary lines. divers locations. NOAA Diving Manual —October 1991 Working Dive Procedures Figure 8-13 Diver-Held Sonar and is used because it is impractical for divers and operate cumbersome and complex navi- history to carry An gation equipment. acoustic-based navigational system has recently been developed that uses a person's sensory ability to differentiate the time-of-arrival of under- water sounds at the two ears. produced along a line, a If a sequence of sounds is person interprets them as deriving from a moving sound source, just as a person perceives the lights being sequentially turned on and marquee off on a theater as moving. A diver can quite accurately perceive the center of a sound array and swim to when diving in from distances as great as 1000 feet (303 m). This technique can be used in habitat operations and Sonar ity to it is murky water. another method of increasing a diver's abil- may navigate under water. Divers find carrying a Courtesy Dukane Corporation compact active sonar useful for avoiding obstacles. Underwater diver-held sonars have been used with some success for years (Figure 8-13). The effectiveness of sonar operations is related directly to the level of a many hours diver's training; of listening to audio tones headset are required before a diver can "read" the in a tones. When using diver-held sonar, the diver slow 360-degree rotation until the object is makes a located and then notes the compass heading. The active range of most diver-held sonars the passive or listening is about 600 feet (182 m). In mode, pingers or beacons some- times can be detected as far away as 3000 feet (909 m). For shorter ranges, there are units that allow a diver ahead and obtain a direct readout feet for distances up to 99 feet (30 m) with a For relatively short underwater excursions, however, the compass, watch, and depth gauge are when activated, emit a high-frequency signal. are the used in companion Pingers a in a is noted. is To swim good compass course, the axis of the compass must be A simple and reliable parallel to the direction of travel. method of achieving this that does not have the to to grasp this is for divers to compass on arm with which the compass Swimming with the arms it extend the arm in front of hand the other them (i.e., the strapped) (Figure 8-14). is helps divers to in this position follow the desired course and, in low visibility, prevents them from colliding with objects. Practicing on units to pinger locators; locators are land by walking off compass courses and returning to the passive mode. Pingers can be attached to the starting point helps to train divers for underwater any underwater structure, including: navigation. Because the accuracy of a compass by the presence of advisable to deter- steel tanks, it is is affected • Habitats; mine a • Submersibles; diver swimming alongside and varying • Pipelines; depth gauge or watch should not be worn on the same • Wellheads; • • Hydrophone Wrecks; and • Scientific instruments. as the compass because compass heading. A in some however, the sequentially activated acoustic array to either pingers dead reckoning. — NOAA the course. may cause A a deviation in D T = S cases, have been as accurate as dead reckon- system has been shown to be superior October 1991 it with a second diver can calculate his or her transit time by using locating underwa- within the audible frequency range. In single beacons in a pool the following formula to estimate distance: with acoustic beacons that emit signals ter structures ing; compass's deviation arm arrays; Divers have had some success or com- or her. Progress timed with the watch, and the depth arm 1982). him horizontal position in front of in cm) (Hall a along the line of bearing, holding the compass and then Acoustic pingers are battery-operated devices that, the still pass bearing has been ascertained, the diver swims to point the device reported accuracy of 6 inches (15.2 Once simplest navigational devices available. where T = D = S Diving Manual = transit time in minutes distance to be covered in feet speed of advance in feet per minute. 8-17 Section 8 Figure 8-14 Using a Compass for Navigation A swimming at a pace maintained over a known distance and slightly modifying the formula to: diver can estimate speed by easily S D =T For example, a diver traversing a 1000-foot (305 m) course in 10 minutes (30.5 is m) per minute, mile (1.85 km) per swimming at a speed or approximately of 100 feet 1 nautical hour. Some underwater topographical navigation aids that can be used are underwater landmarks (and turns made with respect to them), the direction of wave ripples in the sand, and the direction of the current (if it is known change during the dive). Some areas require the use of a transect line because they lack distinct bottom features. Divers often use the increase in pressure against their ears and masks or changes in the sound of exhaust bubbles to identify changes in depth. that the current will not 8.4 UNDERWATER TOOLS A fundamental aspect of accomplishing work under is the selection of proper tools and equipment. In all operations, the relative advantages and disadvantages of power tools and hand tools must be considered. The amount of effort that will have to be expended is an important consideration in underwater work, and power tools can reduce the amount of physical exertion needed. Having to supply tools with power and to transwater may be a substantial disadvantage. The performance of divers under water is degraded port them, however, by several factors, including water resistance, diver buoyancy, equipment bulk, the confined space environment, time limitations, visibility restrictions, and a amount of reaction force without adequate staging, hand grips, or body diver's inability to provide a proper harnesses. A diver's land. performance compared with significantly Even a may therefore decrease his or her performance on relatively simple task like driving a nail can be difficult because of limited visibility, water viscosity, and other environmental factors; however, some tasks are easier to accomplish under water because of the diver's ability to move easily in three dimensions. Because diver safety is a primary consideration in any underwater operation, hazards such as electric shock, excessive noise, and other potential causes of injury must be taken into account when selecting underwater lists along with their 8-18 some common tools used under water, sources of power and available acces- J. Cardone Most pneumatic and hydraulic tools can be adapted for underwater use. The information supplied sories. by the manufacturer contains detailed use tool's specifi- cations that should be observed faithfully. 8.4.1 Hand Tools Almost all standard hand tools can be used under water. Screwdrivers are generally available in three configurations: the machine (or straight-slotted) type, the phillips type, and the alien type. alien screwdriver only torque is required to operate is to damage When and the linear slip out of the screw the screw by twisting. multipurpose tool can be driver blade it is screwdriver have a tendency to head or the three, the minimum. Also, the alien longer lever arm. The other types of reaction force necessary type provides a Of easiest for a diver to use, because and a pair of made by welding pliers to An added tendency of the blade to lihood that the blade will NOAA A single a screw- an adjustable wrench. using a hand saw under water, follow a straight line. tools. Table 8-2 Photo by Bonnie it is difficult to complication is the which increases the likebreak. Because it is easier for flex, Diving Manual —October 1991 Working Dive Procedures Q. co C (0 CO ~o CD Cl- lO o o $ 5< S -D O O CO |co S O E (1) CO IZ0. CO O -C oo Q. bo co a 2 ac o co o 5 o o o CD n c o 3 n CD •D o t o -O 0) CD CD £ = o co £ ac a. o o E 2 Q. °. o *^ o ** ci) £ T3 o »- ^ D) C a c o o < m T3 o o -o a o o 5 oc -o o o 5 "O c CD CO 3 o o E X: 00 CD Q en CO a Q. n CO CD C o o CO to o a c\j S 0) := CO CO co — 9 oo 3 E E "cd o CO r c ^ o ® g. gt o O a T3 fi : cd tt en g" CO J2 cd 3 en CM 5= CD CD C CD o is - s > CD "5 CD CD CO -C -o >. X CL 00 CO O o 5 •D Q. X >. CD 5 E 1- Q. D (0 CD S 3 O CO .C o -C CD *^ co E C E D a> c CL Cl D CD CD T3 CL CO o -C 1- en CO c Q. E O CO CD ^z 3 o o o o c o -D § Cl co X CD "D CD CO T3 o o c CD o CO CO CD E c jj 3 o Q. a CO (0 73 CO c CO T3 CO 3 s CD CO c CO O i; o -^ ~ CO ii T3 >> x CL LU CD C a. O O co L. CD ; en E CO o o a co O O CO o CO M" o J cd" T3 in s o 3 CL ? CD C tr CD a » ^r» 1 E D a>< X CO XI 0) o 1- faa Cl c g T ~ ** o ^r in CD "™ g aj n 3 oi c 2 CO CO E o XI o o E CO c Q. D. CD x> 3 -I o CO o CD en : CD XI CO o o 00 to w to C\J CO E 3 C CD ; a> co CD Q. CO CL CO £ > CL CO CD k_ c O co X ^ a a •D >< D CO o cd :s 3 E c o C -a a> oo c 2 c o CO Q. o co C T3 o O CL s o o -o T3 3 5 a> _> (0 in CD CO oc c XI 'w -C CO « < O CO U d (D O X 3 E 2 o co \_ X 3 en = i « CD <-> a E E x 5 E CD CO xs CO ol CO CD "O Q. CO CD £ .* CJ CO -) c a 8-19 Section 8 a diver to pull than push under water, useful to put it is saw so that the sawteeth are oriented toward the diver and the cut is made on the draw. the blade in the A 2- to 4-lb used underwater short-handled tool. easier to develop force weight of a sledge ting with a lighter Because it is effort by pounding with the heavy than by swinging and hit- site in a canvas bag to the diver's belt with a line. also can be attached to a descending line with a down this line to the job site from the surface. Tasks involving grinding, chipping, pounding, or reaming with hand equipment are arduous and 8.4.3 tect is not practical unless the task hand bath before being turned on once to To Hydraulic Tools closed-cycle power, are safer to use under water, have little or no depth limitation, are much lighter per unit of power output, do not produce bubbles that obscure the diver's vision, and require relatively nance. little mainte- As with pneumatic motors, hydraulic systems have the capability and stop rapidly, and they to start can be operated at different speeds. Tools such as (Figure 8- 15 A), impact wrenches drills pro- (Figure 8-1 5B), chain saws, disc grinders (Figure 8-1 5C), be rinsed with and cable or pipe cutters usually are modified versions of hydraulic tools designed for use on land. To convert tools for underwater use, different seals are used, internal voids are compensated to withstand ambient small. is tools after use, they should oil Hydraulic tools are the most popular kind of tool with working divers because they provide consistent time consuming, and the use of hand tools for these tasks an is easy to lose or drop tools under water, shackle and be slid in displace any water trapped in the tool. than on land, hammer. and are then attached the motor section; the tool should then be sub- merged commonly hammer they usually are carried to the work They a is Because considerably more hammer under water required to swing a it is hammer fills fresh water and lubricated with a protective waterdisplacing lubricant. pressure, external surfaces are painted or coated with 8.4.2 a corrosion inhibitor, and dissimilar metals are insulated Pneumatic Tools from each other. Although pneumatic tools are rarely designed specifically for use under water, they need little, if any, alteration to be used in this medium. According to Hackman and Caudy (1981), the power available in air motors ranges from 1/8 to 25 hp, and loaded speeds range from 40 to 6000 rpm; some of these tools have even higher speeds. Most pneumatic tools require 90 psig of air pressure to operate, and they exhaust into the water. A disadvantage of these tools is that they To facilitate the field use of hydraulic tools in areas where hydraulic oil is not readily available or where environmental restrictions prohibit the discharge of oil, hydraulic tool systems are being developed that use seawater as the working fluid in place of oil. The Navy has supported a program, called the "Multi Func- tion Tool System," that involves the development of a seawater hydraulic grinder, band saw, impact wrench, and rock underwater use. drill specifically for exhaust bubbles that may disturb divers or impair their visibility under water. In addition, the amount of pressure available for power decreases at depth. Pneu- that can be located at the matic tools can be modified to include a hose attach- These power sources are compensated ment on the exhaust that depths but require built-in batteries or an electrical is larger in diameter than the supply hose. Often, the exhaust hose the surface, where it is routed back to discharges to atmospheric pres- Even with these modifications, surface-supplied pneumatic power can be used only to depths of 100 to 150 feet (30.5-45.7 m). Although closed-circuit pneusure. matic tools would not be as wasteful of energy at depth have not been developed because the entire system would have to be pressurized or the tool would have to be designed to withstand ambient water pressure. The extensive maintenance requirements of pneumatic tools can be minimized by using in-line oilers to meter oil automatically into the as open-circuit tools, they air supply hose. After each day's diving, poured into the 8-20 air inlet of the tool until oil it should be completely Hydraulic tools require a power source at the surface or a submersible electrohydraulic power source work site near the diver. to operate at all umbilical from the surface to run the motor. normally operate at pressures from 1000 To psi to The tools 3000 psi. use them, divers usually work standing on the bottom or on some structure. When working with these tools on the side of a structure or in the midwater column, a diver can use harnesses or a diver's stage for support. The U.S. Navy has adapted and developed a variety of diver-operated hydraulic tools for construction and salvage work. These tools include: 1. 2. An abrasive saw (2000 by 1/8-in. thick blade); A grinder (2000 psi, psi, 11 6-14 gpm, 10-in. dia. gpm, used with discs, cups, or wire brush); NOAA Diving Manual — October 1991 Working Dive Procedures Figure 8-15 Underwater Hydraulic Tools Hydraulic tools that minimize diver fatigue and discomfort should be selected. Most tools can be reconfigured or redesigned to increase diver comfort. attention should be given to underwater neering principles the design of in human new tools. More engi- Areas where progress could be made include weight reduction, special grips and triggers, placement of handles at the center of gravity or wherever they will best counteract torque, and reduction of vibration and reaction forces. Hydraulic tools are easy to maintain. They should be rinsed thoroughly with fresh water after each use and then be sprayed with a protective lubricant such as WD-40. Tools 8.4.4 Electric Underwater tools that operate by power have electric been designed, developed, and manufactured, but they are seldom used. The AC motor, stator, and control electronics of such tools are potted in epoxy, motor tools require only a small umbilical, limitation, and are reasonably Courtesy Stanley Hydraulic Tools shock persists, have no depth Although light in weight. ground-fault detector circuitry electric and the water cooled and water lubricated. Electric is is provided, the fear of and most divers consequently prefer to use hydraulic tools despite their greater weight and support equipment requirements. 3. A come-along (1500 cable 1.5 4. A in. psi, 2000 lb. force, moves hurst tool (input of 5000 psi and .07 gpm, jaws of tool open and close with force of 6 tons through Power Velocity Tools Power velocity tools are actuated by the firing of an explosive cartridge, which increases the pressure behind a piston to accelerate a stud or a cutter into the a distance of 32 inches); 5. 8.4.5 per stroke, used as a rigging aid); Impact wrenches (2000 psi, 5 gpm, used for driltapping, or for make/break of nuts and bolts); Linear actuators (10,000 psi rams, 8 ton pullcylinders, 10,000 psi cutters or 2 1/2 in. wire piece (Figure 8-16). Power work velocity tools are used to attach padeyes, studs, and hollow penetrations in plate ling, 6. steel. Different configurations are used to cut cable, rebar, hydraulic/electrical umbilicals, impact socket for loosening jammed and to drive an Studs are nuts. rope, rebars, or splitting nuts); 7. 8. A pump (2000 psi, 5 gpm hydraulic fluid; 100 available to penetrate steel that 400 gpm water flow, used for jetting, washing, and dredging); and Hose reels and different hydraulic power supplies. (An excellent source of information on the operation and maintenance of the Navy's hydraulic tool systems isNAVSEA Some 1982.) thick (0.64 cm). in The cutters can sever at least is, that operates on for 2000 example, a hydraulic psi, 0.5 to 3.0 1/4-inch diameter cables or 2-inch (5.1 gpm, and cm) diameter 1.5-inch (3.8 cm) in composite umbilicals. WARNING Only Properly Trained Personnel hydraulic tools have been designed solely for underwater use. There hammer is psi, May Han- dle Explosive Cartridges. Trained Divers Also Should Use These Tools Only When The Proper Safety Precautions Have Been Taken develops a 40-foot-pound force per blow; output speed ranges from 1 to 300 blows per minute. The unique design uses compressibility of the hydraulic fluid to generate and store the impact energy. October 1991 — NOAA Diving Manual Power velocity tools are well suited to water work. Their weight is most under- comparable to that of 8-21 Section 8 Figure 8-16 Explosive Hole Punch Figure 8-17 Oxy-Arc Torch Courtesy Broco, Inc. Courtesy Battelle-Columbus Laboratories metal being heated. The metal is heated to ignition temperature by a hydrogen/oxygen flame, and pure hydraulic tools, but they require no umbilical or power line. Some models of underwater stud guns feature by the diver. The heavier duty models, as well as most cutters, require that reloading be performed on the surface. oxygen Cutting and Welding Tools Cutting and welding are often required both in sea- water and in dry underwater enclosures or habitats. Since habitat welding involves techniques and tools similar to those of atmospheric welding, this manual addresses only cutting and welding tools that are used then directed at the heated spot to start the as a fuel gas for cutting, barrels that can be replaced easily 8.4.6 is cutting action. Although acetylene also has been used at it is considered unsafe to use depths greater than 30 feet (9.1 m). Shielded metal- arc cutting is a process in which metal is severed sim- and physically pushing the metal out of the kerf. An electric arc is formed between the electrode and the work piece to provide the heat for melting. The process is used in situations where no oxygen is ply by melting available. ting is Some believe that shielded metal-arc cut- superior to oxygen cutting on steel plates less than 1/4 inch (0.64 cm) thick or when cutting brass, copper, or copper-based alloys. Oxy-arc is used to cut metal burns or oxidizes very rapidly. Electric current up to 2 inches (5.1 cm) thick. The most widely used underwater welding process is shielded metal-arc welding. The weld is produced by heating with an electric arc between a flux-covered metal electrode and the work piece. The heat developed by the arc causes the base metal parts, the core wire of the stinger, and some of the flux covering to melt. Other constituents of the flux decompose to gases, which shield the molten metals somewhat from contamination. When welding under water, technique is important and special training is required. Generally, underwater welds are not as strong as surface welds because of water quench and contamination. Also, it is vitally important that the diver be aware at all times of not required for oxy-hydrogen, but an air hose the severe shock hazards associated with electric cut- in seawater. Underwater cutting and welding processes emit toxic gases that rise to the surface and, since they are heavier than air, collect in any low-lying confined areas. Ventilation during is underwater cutting and welding thus essential to protect both divers and surface personnel. The most popular cutting torch ure 8-17); the process is is oxy-arc (Fig- learned with less training than oxy-hydrogen, oxy-acetylene, or shielded metal arc cutting. The oxy-arc process uses electric power to heat the work piece to ignition temperature; a jet of oxygen is is required to then directed at the heated spot and the fill the flame and to hold water 8-22 is a shield cup around the tip to stabilize away from the area of steel ting and welding processes. Metal helmets must be insulated. NOAA Diving Manual —October 1991 Working Dive Procedures INSTRUMENT IMPLANTATION 8.6 WARNING The proper implantation Diver Training and Experience Are Essential in Underwater Cutting or Welding gations. is Instruments that are implanted on the sea bottom include 8.5 of scientific instruments important to the success of underwater scientific investi- cameras, positioning stakes, radi- lights, ometers, recording current meters, thermistors, oxygen sensors, and acoustical devices. Factors affecting MAINTENANCE AND REPAIR TASKS the success of implantation are: Maintaining and repairing equipment, structures, and instruments under water requires skill and an under- • standing of the work to be done. In addition, underwater maintenance should be performed only when envi- sions, fragility, • ronmental conditions are acceptable. The available power supply and instrument out cables, or (if read- self-contained) the frequency divers should practice underwater tasks with which the instrument's batteries must be changed or the instrument must be serviced or The time that must be known (or a will be needed to accomplish the task to enable the diver to major portion of air supply. it) complete the task replaced • within the constraints of the For strenuous tasks, the work should be divided into subtasks and several divers should take its to Bottom conditions, the bearing strength of the • them out. To accomplish underwater work, four task phases are involved: The alignment of the instrument in position, height above the bottom, and its sensitivity misalignment turns carrying bottom, anticipated currents, and the type of marine life • The Inspection of the work site and determination of precise markings of instrument location and methods used the • size and weight, mounting dimenand attachment points shallow water before attempting them in deep water. If practical, in The instrument's for recovery at completion of the mission. the condition of the equipment that needs mainte- nance or repair; • • The Selection of appropriate tools; cal Performance of the repair or maintenance task; and • and weight of the instrument and size used and the techniques chosen to to the site. Reinspection to ensure that the work has been accomplished successfully. its physi- dimensions and fragility affect the type of anchor may move the instrument For small instruments, a concrete block be an appropriate anchor. The blocks can be predrilled, fitted with fasteners on the surface, moved Most underwater maintenance and repair tasks that is asked to perform are associated with the inspection and repair of a ship's rudder, propeller, sea a diver chest, or cathodic protection system. When a diver is working over the side of a ship to perform a maintenance task, the ship's propeller should be locked out and the rudder should be held in static position. The appropriate international code flag should be hoisted. Divers should be careful to avoid skin contact with the hull of the ship on which they are working, because to the site as a unit and positioned. and In other and instrument can be moved and a diver can then position and cases, the concrete block to the site separately, align the instrument in the water. A concrete block anchor can be lowered directly into position using a winch, or it may be fitted with flotation devices and guided into position by a diver, who removes the tion device when the anchor is flota- in position. For large instrument packages, anchors can be made of metal piles that are driven into the bottom by a diver using a sledgehammer or pneumatic impact hammer. marine Steel pilings create magnetic anomalies that can affect growth (barnacles, algae). These paints retain their toxic qualities for months after the freshly painted instrument readings; instruments should therefore be toxic paints are often used on the hull to inhibit used only after the effect of the pilings on the instru- may ship has been returned to the water. ment's functioning has been calibrated. Pilings Maintenance and repair tasks can be accomplished more easily if a restraining system is used. Such a grouted system can be as simple as a instrument installation and can be driven into the bot- onto that is line for the diver to hold attached to a convenient point or as elabo- rate as a jacket with magnets or suction cups that attach to a shear plate. October 1991 — NOAA face. tom in Embedment anchors can to secure the lines. be used to stabilize an Chains or wires equipped with turnbuckles can be run over the instrument package between anchors Diving Manual be place with concrete supplied from the sur- to secure the installation further. The 8-23 Section 8 foundation package should be designed to accept the therefore equip these instruments with automatic pinger instrument package easily so that devices in addition to marker buoys (see Section 8.3). If a pinger-equipped instrument is believed to be it is as easy as possi- ble for the diver to attach the package. foundation When the complete, a line or lines should be run to is the surface to assist in lowering and guiding the instru- ment into place. Many underwater instruments require outside power to operate and to transmit data to outside receivers. During the installation of instrument cables, a diver usually is required to anchor the cable at various points along the cable run. The first near the instrument package. point of anchor should be To reduce and the instrument. The diver should guide the instrument cable around any rocks or bottom debris that might abrade the cable covering. Anchors should be placed a bight) of extra cable between the first anchor frequent intervals along the length of the cable, wherever the cable turns, and on each side of the cable where it runs over an outcropping or rise in the bottom. Cable anchors can either be simple weights attached embedment the cable or special The alignment alignment tom is A is important to simple technique to achieve to drive a nonferrous stake into the bot- A then to hang a compass from the line or wire. nonferrous stake and the compass indicates that the alignment is correct. stakes and the attached line then act as the reference point for aligning the foundation or instru- ment. A tape is used to translate measurements from the reference stakes and line to the foundation or the 8.7 necessary. HYDROGRAPHIC SUPPORT In hydrographic operations, divers can be used to con- firm the existence and/or location of hazards to navi- and measure least depths, and resolve any sounding discrepancies identified by different surface-based measurement techniques. When using gation, locate divers for this type of work, is it essential to consider the skills of the divers, water conditions, the nature of the work, special equipment requirements, and the Because hydrographic availability of diver support. important to mark the dive site it is using buoys, electronic pingers, or fathometers; this precaution becomes increas- ingly important under conditions of reduced visibility and high currents. Hazards to Navigation 8.7.1 A ing significant portion of hydrographic support divis Once conducted to identify hazards to navigation. the general location of a navigational hazard has been identified, When Before selecting a location for an instrument, botconditions should be analyzed to identify the appro- priate foundation. The instrument site should be reinspected at frequent intervals to monitor the condition of the instrument ma-ine growth that Unmanned may and to clear away sediment or affect instrument readings. its precise location can be determined instrumentation is increasingly used for Because many unmanned instruments are self- contained and expensive, they must be equipped with reliable relocation devices. the object has been found, with a taut-line buoy and be noted. If the depth is its it should be marked geographic position should shallower than about 50 feet (15.2 m), a lead line depth should be recorded, along with the time of notation. Diving operations that are designed to prove that no navigational hazard exists in a particular area are long-term data-gathering and environmental monitoring tasks. is using the search techniques described in Section 8.2. instrument. tom long search second then driven into the bottom when is murky water when the divers are surface supplied and use liveboating techniques (see Section 8.10.1), particularly if the pinger is weak and a especially well in operations are frequently conducted in open water, that has a nonferrous wire or line attached The two to anchors. of the foundation successful implantation. to the approximate location; they can then descend and search with a hand-held locator unit. This technique works move- either the cable or instrument will break the cable connection, the diver should allow a loop (called at implantation, a surface receiver from a boat can guide divers unit operated the possibility that the cable will topple the instrument or that ment of lost in the vicinity of Although surface or sub- LORAN-C extremely time consuming and require painstaking documentation of search procedures and location. The reported location and geographic position of the hazard should be marked precisely; a taut-line buoy should be used to mark the search control point. Any time the common moved, the move should be documented and the geographic position of the new control point relocation devices, at least for short-term implanta- should be noted. Documentation of the search should surface buoys (used in combination with or satellite navigation systems) are the most tion, these buoys are subject to vandalism, fouling ship propellors, and accidental release. 8-24 Many control point is in include the geographic position of control points, the users type of search, the equipment used, water conditions, NOAA Diving Manual — October 1991 Working Dive Procedures and problems encountered, what was found or not found, statement describing the area that has been searched and any area that may have been missed. and a hazards associated with any wreck diving operation, the wire itself poses a hazard. For example, if the wire slips on an obstruction, could pin it diver; a if the strands of the wire are broken, the wire can cut a diver severely; Locating and Measuring Least Depths 8.7.2 it When Divers can be used to determine least depths accurately, especially in such areas as rocky shoals, coral and wreck sites. After the general location to be studied has been identified, a diver is sent down to mark precisely the least depth by tying off a line on the bottom so that a buoy floats directly overhead. Care reefs, must be taken to ensure that the lead line marking that the time of is recorded. A is plumb and taut-line buoy can be used to mark the geographic position of the least depth so that it can be noted and recorded by surface personnel. and if a diver holds the wire and an underwater obstruction needs tigated, the support boat must be nearest the obstruction. After agreeing on the discrepancies, and mark site, resolve in swim to the buoy and descend to the bottom wire. Depth gauges are checked, and the depth of the obstruction is noted on a slate. Because of forces acting on both the wire and the upright to the buoy, the depth at the weight can vary from its setting by as much as 10 feet (3 m). Once on the bottom, the divers proceed hand-over-hand along the wire, one behind the other, taking care to stay procedure is to effort to stay as The recommended "crab" into the current, making every much above the wire as possible. WARNING Divers Must Be Extremely Careful When ing Inside the Bight of a Ground Wire Work- WIRE DRAGGING Wire dragging is a method The method involves deploying a wire between two ships and hold- depth with weights ranging from 50 to 250 pounds (22.7-113.4 kg). The objective of this procedure is to tow the wire in such a manner that hydrodynamic forces induce an arc-shaped curve. As the ships move through the water, the wire will snag on obstrucing it at tions protruding After arriving at the obstruction, wire depth of ensuring that surface ships can pass through an area safely. above the depth of the drag. Divers supporting wire-dragging operations are used to identify: • be difficult reefs. 8.8 • may areas such as rocky substrates, faulted or volcanic bottoms, • buoy proce- the site correctly. Dis- crepant measurements are most likely to occur and all dures, the divers tends to push the diver into the bight. of undersea features are dis- crepant, divers can be used to inspect the be inves- because most drags are run with the current, which Resolving Sounding Discrepancies When measurements to tied off to the outside the bight of the wire. This 8.7.3 pulls loose, it can sever the diver's fingers. The objects on which the wire hangs; The least depth over the obstruction; and The highest protrusion that could be caught from any direction. recorded. The the obstruction; this procedure requires the divers to leave the wire. If the obstruction depth when they enter the bight. Once the least depth is found, the divers record the depth and determine whether the high point could cause the ship to hang at any point. If the object is intact or is a candi- point date for recovery, the divers select a suitable place to tie off a small buoy. The buoy must be tied off inside away when the drag wire is the bight so as not to be torn recovered. The depth information recorded the equipment involved is in the removal of minor obstructions. Another task performed by divers verified by a is surface-tended pneumatic pressure gauge. Because Divers also can identify underwater features that pose assist not substantial, the is divers should be several feet above the obstruction's a hazard to fishing nets and trawling or ground tackle and is divers then try to find the least depth of is assessing the areal extent is cumbersome, this technique rarely used during the initial investigation. tively calm seas and slack current, a lead line In rela- may be used to verify depth information. of wreckage. If the least depth cannot be determined Because divers following a wire do so in single file, it accurately, the approximate depth needed for clear- is easy for one diver to lose track of his or her buddy. ance A buddy-check should therefore be carried out every is sought. Divers need to exercise extreme caution when work- ing around wire drag hangs because, in addition to the October 1991 — NOAA Diving Manual 50 feet (15.2 m); this procedure also entanglement when there is poor may prevent diver visibility. 8-25 Section 8 Figure 8-18 Salvaging an Anchor With Lift Bags NOTE Wire-drag support diving should be done only by experienced divers who are well trained in the techniques and fully aware of the hazards involved. SALVAGE 8.9 Salvage of a ship or craft, cargo, or its equipment its requires a knowledge both of the technical aspects of recovery and the legal aspects of ownership of the salved items and claims for salvage. recovers a ship or craft or its ment with the owner must A salvor who cargo without prior agree- file a claim in the United States District Court nearest to the port in which the salved items are landed. Salvage techniques vary considerably with the size, and condition of the item to be salved, the depth of the object and seafloor conditions, and the equipment available to conduct the salvage. Salvage techvalue, niques that are used commonly winch or crane, floating lifts are direct lifts Photo by Geri Murphy using a using a device to compen- from the container; this will displace more water and may increase the speed of ascent to an uncon- buoyancy of the ship or craft, and repairing and restoring the inherent buoyancy of the sate for the negative salved object trollable rate; itself. Individual divers often salvage instruments or instru- ment arrays, anchors, or other small structures. In the • The weight of the object in water is amount equal to the weight of the water reduced by an it displaces. majority of these cases, the diver simply carries the item to the surface. In other situations, the diver atta- ches a flotation device (Figure 8-18) or, for items, a line or wire that will facilitate a direct heavy lift to 8.9.1 Lifting Many Devices objects can be used as lifting devices, includ- ing a trash can or bucket inverted and tied to the the surface. In some salvage operations such excavations, it may be necessary to clear bottom sedi- ment from around the item before This procedure is as archeological it can be recovered. necessary to ensure that the item free of entanglement. A water jet or air lift is commonly used to clear away entangling debris (see Sec- is bag placed in a net bag, a 55-gallon oil drum, or a commercially available lift bag (shown in Figure 8-18). If the object is lying on a soft bottom, it may be necessary to break the suction effect of the mud by using high-pressure hoses or by rocking the object, a plastic object back and forth; a force equal to 10 times the may be necessary to break it free. Raising and lowering can be accomplished with commercially available lift bags of various sizes and weight of the object tion 9.12.2). When working with heavy or overhead items with under tension, divers must develop cables, lines, or chains lifting capacities or a sixth sense for safety. Divers should avoid positioning themselves or their umbilicals under heavy objects that might fall or placing themselves above lines that are under tension. The buoyancy or the weight of water displaced from a container by the compressed air necessary to raise an object is equal to the weight of the object in water plus the weight of the container. It is important to remember that: • The container should be vented • The air will expand if the object is raised from the bottom before all the water has been displaced air 8-26 from rupturing to prevent excess it; tubes. One with ordinary automobile regular-sized inner tube will tire lift inner about 100 pounds (45.4 kg). The tube or tubes are rigged with them together and with the a short loop or rope holding valves pointing toward the bottom. (The valve caps and cores must be removed.) A rope loop is attached to the object to be lifted and is then pulled down as close to the object as possible, because inner tubes have a tendency to stretch to about twice their original length before lifting starts. An ordinary shop air nozzle with a spring-loaded trigger is attached to a short length of low-pressure air hose and is then plugged into the low-pressure port of a single-hose regulator first-stage NOAA Diving Manual — October 1991 Working Dive Procedures mechanism. This device is attached to a separate air cylinder for transport to the work nozzle The end site. of the and pushed so and the object inserted into the tire valve opening is The tube that air will not escape. fills, Care must be taken to leave the valve open, because the expanding air on surfacing rises to the surface. the object cannot be lifted to the surface directly If by winching or lift devices, the rise of the tide can be used if a large vessel or pontoon is available. At low connected tautly to the object and the tide, lines are surface platform; as the tide rises, the load rises with it. could burst a closed system. With practice, objects can Every salvage project must be planned and executed Novice divers should not attempt under- be raised part-way to the surface and moved under individually. kelp canopies, etc., into clear water, where they can be water salvage tasks for which they are not properly surfaced and towed. Divers using this technique should trained or equipped. accompany try to the object to the surface and should way expose themselves not stay on the bottom or in any drop or ascent path of the object. This technique to the is 8.9.2 Air Lifts An especially useful to biologists lifting heavy bags of Although the innertube method works, commercially for lift bags are preferred. These bags are designed heavy duty use, come from 100 to 20,000 lbs in a variety of sizes (45.4-9080 kg) in and have built-in overpressure valves. They ranging and/or dump and readily trans- also are lightweight weighs only 6 lbs (2.7 kg), and a 1/2-ton-capacity bag weighs only 14 mud, and similar materials from the holds of some cases of stranding, an air lift may be used to clear away sand mud from the side of the vessel (Figure 9-39); An air lift works on the pressure-differential princi- and ple. Air introduced into the lower end of a partially is submerged pipe. The combining of air bubbles with the liquid in the pipe forms a mixture that is less dense than the liquid outside the pipe. The lighter density head pressure inside the pipe than outwhich causes the mixture to rise in the pipe. The amount of liquid lifted depends on the size of the air lift, submergence of the pipe, air pressure and volume side, lifting an object, the bag should be inflated lift Inflation should cease as soon as the object begins to off the bottom. rate of ascent to lose control. may Because expands as air it rises, Loss of control tip is over dangerous, and when it it used, and the discharge head. the increase rapidly, causing the diver can cause the bag to also An to the bottom. The bag's dump valve, therefore, should be used carefully to control ascent. discharge pipe and a foot The size of the discharge pipe ranges from approximately 3 to 14 inches (7.6-35.6 reaches the surface, spilling the air out and sending the object air lift consists of a piece or air chamber. in back mixtures of water, grain, lift results in less lbs (6.4 kg). slowly from a spare scuba cylinder or other air source. lift used to ships during salvage operations. In lifting capacity, relief portable, e.g., a bag capable of lifting 100 lbs (45.4 kg) When is sand, specimens. available air lift done and the service intended. The air chamber should be located approximately 20 to 30 inches (50.1-76.2 cm) from the end of the pipe. Table 8-3 may be used as a guide charge pipe and WARNING air available An Do Not Use Your Buoyancy Compensator as a Lifting Device While Wearing the Compensator cm) diameter, depending on the amount of work to be in selecting the size of dis- air line, taking into consideration the and the job to be done. air lift operates as follows: the submerged in the mixture discharge pipe to be lifted to a approximately 50 to 70 percent of the total length of The air is turned on, and the lifting operation commences almost immediately. Occasionally, considerthe pipe. able experimentation In addition to the type of lift bags shown in Fig- amount of is necessary to determine the air required to operate the lift efficiently. ure 8-18, special computer-controlled lifting systems The use of air lifts in archeological excavation have been developed for large salvage jobs (Kail 1984). described in These systems are relatively insensitive velocities to be held constant even for loads as great as Such systems can be used for October 1991 8.10 emplacing and retrieving heavy instrumentation packages as well as for salvage. is Section 9.12.2. to surface weather conditions and permit both ascent and descent 15 tons. is depth of FROM AN UNANCHORED PLATFORM DIVING Diving from an unanchored barge, small boat, or can be an efficient method of covering a large vessel — NOAA Diving Manual 8-27 Section 8 Table 8-3 Selection Guide For Discharge Pipe and Air Line Diameter of Pipe, inches Diameter Compressed of 3 4 6 10 Cubic Gallons per Minute Air Line, inches .50 50--75 .75 90- -150 1.25 2.00 210--450 600- -900 Feel: of Air 15-40 20-65 50-200 150-400 Source: area for search or survey purposes. towed from a boat that referred to as liveboating. diver but the diver is is When a diver is under way, the technique is When liveboating is (1979) used, the following safety pre- cautions are recommended: a boat accompanies the not attached to the boat and being propelled by current alone, the technique drift diving. When NOAA is is • boat should be equipped with a "jet propeller. There are procedures and safety precau- tions that apply to both kinds of diving; these are If possible, the dive" propulsion system, which has no rudder or called • If the boat equipped with a propeller, a propeller is cage or shroud should be fabricated to protect the described below. divers. • WARNING A communications system should be practiced prior to diving. When Liveboating or Drift Diving, the Engines of Both the Small Boat and Large Vessel (if Any) Should Be in Neutral When the Divers Are Close to the Boat or Are Entering or Leaving the Water tow or descent • Liveboating Some underwater tasks require great distances covered in a minimum amount of time. These include inspecting a pipeline, surveying a habitat searching for a lost to be tasks Free-swimming divers are inefficient at carryand quicker methods of search or survey are needed. Devices such as sion units, swimmer to Divers being towed should carry signal devices from the boat and tow line. Unless there is danger of entanglement, the divers should carry a surface float to assist the boat crew in tracking them. The float line also can be used If diving If diving A • another method of searching a large area. This technique is called diver The boat should be equipped with and vary their depth according to the contour of the bottom, which allows them to make a closeup search of the area over which the boat is traveling. • 8-28 and all charts, radio, and resuscitator, emergency air sup- equipment required by the Coast Guard The boat operator should know the procedure alerting the Coast Guard in case of an accident. for All personnel on board should be thoroughly briefed on the dive plan. One Liveboat Divers Should Be Careful to Moniand Control Their Depth to Avoid Developing an Embolism aid kit for safe boating operations. • tor with surface-supplied equipment, one ladder or platform should be available for ply, towing; the divers hold onto a line attached to the boat WARNING on the bottom. with scuba, two divers should be towed boarding. first is weather become separated the boat suited up and ready to dive. • increase diver efficiency. Towing a diver behind a small boat from the diver should be towed while the other remains in propul- wet subs, or towed sleds may be used line separate together. • wide area, or any number of similar opera- ing out such tasks, A may be employed. for signaling the divers while they are • site, instrument, observing fish popula- line conditions such as fog, in case they 8.10.1 tions. up between (whistle, flare, etc.) especially in adverse • tions over a set the diver and the boat, with signals agreed on and and inexpensive method of liveboating single towline with loops, a tow bar, or a fluked anchor for the divers to hold. Divers using such an apparatus should be towed at a comfortable speed that will not dislodge their masks. The height above the bottom at which the divers travel is practical involves the use of a NOAA Diving Manual — October 1991 Working Dive Procedures controlled by the speed of the boat and the ability of length of the towline from the position of the surface the divers to arch their bodies and to plane up or down. boat at the time of observation. A back to a yoke with a short line for each diver works best. There should be two crew members in the tow boat, one to single towline, rather than a bridle, leading operate the vessel and the other to watch for surfacing divers and to keep the towline from fouling in the boat In areas may where entanglement not a problem, divers is wish occasionally to drop off the towline during A traverses to investigate objects of interest. m) (13.4 50-foot return line attached to and trailing behind the aquaplane can be used to permit a diver who drops propeller. the sled to grasp the line and return to the sled. The equipment necessary for towing divers is readily available. The boat should have at least a 30-hp engine and should be large enough to accommodate three or more people and the diving equipment. A towline of 1/2 or 5/8 inch (1.3 or 1.6 cm) nylon line about 200 feet (61 m) long used with about 75 pounds important for those (34 kg) of weight permits divers to reach depths of to 90 fsw (27.4 m). The towing weight should be made of two or three pieces of lead, steel, or concrete. up Three 25-pound (11.3 kg) lead balls are ideal are doing, especially to hang up on 1/2 inch (1.3 cm) submerged objects. A return line of nylon 50 feet (15.2 m) long should be tied to the towline at the weights. Polypropylene line should not be used because trail it is buoyant. The return line will behind the towed divers, who hang onto the towline at or near the weights. Any time one diver leaves the towline, the partner should monitor the departing diver's actions until he or made she has again contact with the return line. If the may aquaplane released by sled or downward by Some tow itself and have a small wire rigs built into the towline, with a waterproof pushbutton switch, so that the divers can communicate by buzzer with the tow boat. One of the best methods of towing divers, especially they intend to drop off the towline, arm is to equip each of the yoke with a large cork float, such as those used on fishing nets or mooring pickup poles. The diver merely straddles the cork and hangs onto the The towing pull is ahead. line then between the legs and not on the hands and arms. Maneuvering by body flexing easy, is and when the divers wish to leave the line they merely release their grip and spread their legs, allowing the cork to rise rapidly to the know boat surface to let the divers are off the line. personnel As soon the in as the cork breaks the surface, the boat stops, backs up along the line to the cork (the boat abandon the towline and both divers must surface line to the boat), must not pull the cork and hovers, with the engine and in neutral, near the bubbles until the divers surface. The divers Another liveboating method uses the aquaplane (Fig- The simplest ure 8-19). tilted is the divers they intend to drop off the line A diver fails to regain the return line, the partner must together. know what boat to continue planing crash into the bottom. because less likelihood that a ball will is if observe the bottom. a diver if there in the off It downward is a shown that, when the tow. Experience has dynamic thrust danger of losing the bubbles using board corresponding pull on the towing cable. to counter the The addition version or sideways, provides a can then hand over samples, relate findings, and resume of a broom-handle seat and proper bal- that there this or no little is method, because the relatively slow towing speed of the boat allows the cork to surface within seconds of being released. The ancing of the towing points permit one-handed control cork should surface at a point very close to the place of the flight path. With an aquaplane, which can be few hours from off-the-shelf materials, a team of divers can be towed behind a small boat; as where the divers dropped off the made not used and in a with other towing methods, the maximum be such that the diver's mask not torn off. is speed must The dive team may operate either in tandem off the same board, which requires some practice and coordination, or each diver As may have in the traverse (see Section the diver keys observation to time. 10.16.5), At the same time, a surface attendant notes the location of the tow boat or escort boat as it line. moves along the traverse, with horimarking locations versus time. to be is a lowered slowly and carefully overboard, so as not to hit the divers below. The towboat should stand by vents the surface boat from being carried at away from the survey area by current or wind. The scope and in of the towline may be as much as 10-to-l, deep water this could place a diver far behind Later, the position of the diver at times of recorded earlier, the observations can be determined by subtracting the the diver Diving Manual is chance that they are temporarily lost. In this case, a standby buoy with an adequate anchor should be ready the tow boat. If a weighted line — NOAA method bubbles cannot be seen from the tow boat, there zontal sextant angles October 1991 If this after the divers drop off a tow, their the buoy until the divers surface. This technique pre- a separate board attached to a yoke. swimming if, is is used, as described scope can be reduced to about 4-to-l. a long distance behind the tow boat, If a 8-29 Section 8 Figure 8-19 Aquaplane for Towing Divers Source: iMOAA (1979) safety boat may be used to follow the towed divers to them if they become separated from the towline. Whenever a towing operation is planned, regardless of the equipment or method used, it is advisable to assist conduct a series of practice runs to determine the best combinations of boat speed, towline-yoke length, and diver-boat signals. Although towing is a useful way of terrain, there are limitations technique. It is to especially cautious to keep the umbilical clear, and positive may wish The system that allows monitoring of the diver's communication. If diver-to-surface communication is interrupted for any reason, the engines must be stopped. bridge also to incorporate a cover a great deal and drawbacks difficult to take notes or to this photographs 8.10.2 Drift Diving while under tow, unless enclosed sleds are used. There may communications must be maintained between the bridge on the large vessel and the tender. be considerable drag on the body, so one should Drift diving area when is used occasionally to cover a large there are strong currents. Divers are put hands should not be used for anything but holding on. water upstream and drift with the boat, which buoy with a clearly visible diver's flag. If the operation must be conducted in heavy currents, divers Sample bags, cameras, should enter the water as far upcurrent as necessary not carry bulky equipment either in the hands or on the weight belt. Until the diver leaves the towline, the should be attached to the etc., towline with quick-release snaps. to The amount of work be accomplished and the equipment to be carried can be determined in predive practice. into the trails a and drift with the current, holding onto a line attached to the drifting boat. Drift diving only when observers should be carried out in the drifting boat can see the Liveboating also can be used when surface-supplied diver's bubbles. If the drift involves a large vessel, a umbilical systems are provided. Under such conditions, must be slow (0.5-1.5 k (0.25- small boat should be used to track the divers and to the speed of the boat pick them up. As with liveboating, drift divers should 0.75 m/s)), carefully controlled, and determined by the carry appropriate signaling devices (see Section 8.10.1). experience of the divers. Precautions must be taken to During pickup, the boat operator should not (except an emergency) approach the divers until the entire dive team is on the surface and has given the pickup avoid fouling the diver's umbilical in the propeller. Generally, the propeller is covered by a specially in The constructed wire or metal rod cage, and the umbilical signal. "buoyed" so that it floats clear of the stern. When liveboating from a large vessel, it may be desirable to tow a small boat behind the vessel and to tend the towed diver from the smaller boat. The tender must be side the dive party on a is 8-30 boat's operator should bring the boat along- downwind or downcurrent side, and the dive tender should assist the divers aboard. In all cases, the boat's motor should be in idle during pickup, with the propeller in neutral. NOAA Diving Manual — October 1991 Working Dive Procedures WARNING explosion, losing its intensity with distance. pressure waves follow the Liveboating or Drift Diving Should Never Be Conducted With Inexperienced Personnel UNDERWATER DEMOLITION AND EXPLOSIVES Many underwater Less severe shock wave very closely. For an extended time after the detonation, there is considerable turbulence and movement of water in the area of the explosion. 8.11 initial Many factors affect the intensity of the shock wave and pressure waves; each should be evaluated terms of the particular circumstances in in which the explosion occurs and the type of explosive tasks require the use of explosives. Several different types of explosives are available, and involved. Type of Explosive and Size of the Charge. Some these can be applied in a variety of ways. Because explosives have high brisance (shattering power explosives are powerful and dangerous tools, they should power at long range, while others have reduced brisance and increased power over a greater area. Those with high brisance generally are used for cutting or shattering be used only by trained personnel. To achieve accurate underwater applications, the explosive must results in be selected carefully and positioned properly. immediate in the vicinity of the explosion) with less Explosives are used under water to remove obstruc- purposes, while low-brisance (high-power) explosives open new channels or widen existing ones, and are used in depth charges and sea mines, where the tions, to to cut through or cables. steel, They concrete, or wooden pilings, piers, are also used to trench through rock or coral. Explosives suitable for underwater use include primacord, various gelatins, plastics, precast blocks, liquids. Such and some charges are relatively safe to use if the target may not be in immediate contact and the ability damage over to inflict a greater area is an advantage. The high-brisance explosives therefore create a highlevel shock wave and pressure waves of short duration over a limited area. High-power explosives create a less intense shock and pressure waves of long duration manufacturer's instructions are observed and general over a greater area. safety precautions for explosives handling are followed. sive to be utilized Bulk explosives (main charges) generally are the most use to estimate the type and duration of the resulting stable of the explosive groups; there shock and pressure waves. The principal characteris- less stability progressively is with the secondary (primers) and tor (detonators/blasting caps) groups. initia- Initiators and tics of the most shown tion are in The characteristics of the explo- need to be evaluated carefully before commonly used Table explosives for demoli- 8-4. secondary explosives always should be physically separated from bulk explosives. WARNING WARNING Only Properly Trained and Certified Personnel Are Permitted to Handle Explosives An underwater explosion creates a series of waves that propagate in the water as hydraulic shock waves hammer") and in the seabed as seismic waves. 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 (the so-called "water and liberation of a large volume of gas, violent creation in the form of a gas pocket, at high pressure and tem- perature. Subsequent pressure waves are caused by Before Any Underwater Blast All Divers Should Leave the Water and Move Out of Range of the Blast If a diver must remain in the water, the pressure of the charge a diver experiences from an explosion must be limited to less than 50 to 70 pounds per square inch (3.5-4.9 kg/cm 2 ). To minimize pressure wave effects, up a position with feet pointing toward the explosion and head pointing directly away from it. The head and upper section of the body should be out of the water, or divers should float on their back a diver should also take with their head out of the water. rapid gas expansion in a noncompressible environment, For scientific work, very low-order explosions are occasionally used to blast samples loose or to create which causes pressure waves through substrata. Each use must be a sequence of contractions and expan- sions as the gas pocket rises to the surface. The initial dangerous; it high-intensity shock wave is the most travels outward from the source of the October 1991 — NOAA Diving Manual evaluated in terms of diver safety and protection. Bot- tom conditions, the degree of the diver's submersion, and the type of protection available to the diver can 8-31 Section 8 < CO o c » jg c§ to CO CD z « 15 c o DC C © c a •+* c § 5 0) Q. >« T3 X O X X X O O 111 111 UJ UJ C5 Q. > CO CO co CO CO CO CD CD CD CD CD CD o» O) O) O) O) O) c 0 T3 X CD O O c c O) CO CO UJ O CO CO CD o> UJ co CO E O 3 »- >.".— co 3 c o » c —c oCO o CO o> 3 O h. 3 o l_ CD . t O) .c c A Q 3 O %m 3 O 3 O 1- o> c CO Q a a Q Q ^ CO T~ 10 CM *~ 10 •^ CO c 3 O i_ c CO c CO CO c CO 3 O 3 O c c CO CO 3 O u c CO 3 O 1— 3 O 1- C CO JZ 3 O k. O) C CO Q Tf CO '- CM CO CO CO Q. Q. a. C 0. CO CO CD TO Char ivene 00) 1. ffect _ hing CO CD 1 m 10 t— 10 CO '- f- ^ 1— 1 * CO »- ' - ' Co r- tive Bre £ « „ CO = (TN *8 co "o CO CO .2 to w a> CO CO CO Q. Q. a. 0. O O O) O O CM 00 r-- * CO Q. 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CD CO t 8CD «* O m c CM m CD '55 — O a E O O O in to O c to l- Diving Manual CD a. — October 1991 4 Working Dive Procedures Figure 8-20 Underwater Cameras modify the effects of an explosion and must be considered in Divers also should be cautioned against diving vicinity A. Watertight Camera planning a dive involving the use of explosives. when sub-bottom air or high electrical discharges 8.12 UNDERWATER PHOTOGRAPHY Scientists can use three in the profiling using high-pressure is being conducted. methods to document under- water events: written records, tape recordings, and photography/television. This section describes the use of photography and television in underwater work. Courtesy Nikon Either diver-held cameras or remotely operated cam- eras can be used, and each has certain advantages. Diver-held cameras allow the photographer greater mobility and permit more precise positioning B. Standard Camera in Watertight Housing in rela- tion to the subject than can be achieved with remotely controlled cameras. On the other hand, the remote camera disturbs underwater subjects than the pres- less ence of a diver, and such cameras can operate at depths difficult for divers to reach. 8.12.1 Still 8.12.1.1 Photography Lenses and Housings A 35-mm camera is a good starting point for under- water photography; cameras of this type can then be modified as necessary to meet task requirements. categories of camera can be used under water: ments specifically designed to operate Two C. Motor-Driven instru- and Motor Winder Camera in Watertight Housing the sea and in that have water-tight sealing, such as the Nikonos®, or cameras designed for air use that are then housed in a watertight casing (Figure 8-20). Cameras designed underwater use are easily portable and are relacameras that have been adapted for underwater use are more versatile for tively simple to use, while land-use because they can be modified The choice water is of lens for any easily. camera to be used under dictated by the required field of view and the Because the distance from camera must be short compared with that in air (Figure 2-5), a photographer who wishes to photograph a broad expanse must use a lens that has a wide degree of clarity of the water. to subject A coverage. visibility ity, is good rule of thumb is Ikelite Underwater Systems that photographic only about one-third as good as eye visibil- which means that Courtesy a wide-angle lens is an impor- tant tool even in clear water. Wide-angle lenses create optical problems of water require that wide-angle lenses be corrected before they are used under water; a correction for underwater use can be designed into the lens formula under- (an expensive but effective approach), or corrective used through a plane parallel port ports can be placed in front of the lens. Attaching a facing the water, these lenses produce distortions and Plexiglas® dome (part of a hemisphere) and making an allowance for closer focusing of the lens than is water use. When color aberrations, narrow the angle of view, sharpness at the periphery. October 1991 — NOAA The in and lose optical characteristics Diving Manual necessary in air solves the underwater wide-angle lens 8-33 Section 8 Figure 8-21 Basic Equipment for Closeup and Macro Photography Locking Screw problem ter at lesser cost. Several commercial underwa- Support Rod Wire Framer housings have built-in corrective capabilities, and Locking Screw. sealed cameras can be fitted with lenses that range from 15 to mm in width. 80 Close-Up Lens When close-up photography of small objects is required, a plane parallel port coupled with lenses of longer focal length is useful. This type of photography demands ground 9.25 Inches (23.4 cm) glass focusing for precise framing, whisker sharpness of the image, a lens that can focus closely on the object, and at least one light source Locking Knob coupled to the camera. Plane parallel ports are helpful when using a longer lens because they enhance the telephoto effect without noticeably destroying the sharpness or color quality of the picture. For example, A Locking Screw / i the use of a Nikonos® close-up kit with a standard 35 mm lens allows clear pictures to be obtained distance of 9.25 inches (23 cm); with the 35 Locking Screw at a focal mm lens must be 33 inches (84 cm). This achieved through the use of an optically alone, this distance ability is matched auxiliary magnifier lens that is Framer Bracket A. Closeup placed over Extension Tube Lens Wire Framer the primary lens. Another method of obtaining close-ups is macro photography. This technique involves placing an exten- between the camera's body and the lens to A framer extension is attached in front of the lens to ensure proper framing and focal distance, which allows pictures to be obtained at distances as close as 2.5 inches (6.3 cm) from the subject. sion tube extend the focal length. In addition to the high magnification, raphy offers maximum color saturation, sharp focus due to the strong flash illumination, and minimal sea water color filtration because of the short focal distance (usually 3-7 inches (7.6-17.8 cm)). Figure 8-21 shows the basic equipment needed for closeup and macro photography. Unmodified off-the-shelf underwater cameras or simpler housings for air cameras only permit a photographer-scientist to work in the mid-distance range; although useful data can be collected at this distance, long distance, closeup, and Courtesy Geri Murphy macro photogB. Macro life. In comparison, the ground glass focusing of the housed camera and ers to its longer lenses allow photograph- work farther away from their subjects. The under- water photographer must weigh the advantages and disadvantages of each technique to determine which is most suitable. An excellent series of articles comparing closeup and macro photography was recently published in Skin Diver Magazine (Murphy 1987-1988). macro photography can provide valuable additional information. Well-designed and engineered housings for air cameras are heavier and bulkier and require more maintenance than sealed underwater cameras; however, housed cameras can be more flexible and have a broader range of wide angle and closeup capabilities than underwater cameras. Another disadvantage of sealed cameras is that the diver must work within a rigidly defined distance from his or her subject and must rely on mechanical framing rods to determine distance. Few fish will tolerate a metal framing rod in their territory, and these rods often cause unnatural behavior in fish and other marine 8-34 8.12.1.2 Light and Color Light and color go hand in hand in underwater pho- tography (Figure 8-22). Color films balanced for either daylight or tungsten light are relatively blind to the color subtleties that the eye can distinguish within the blue and green spectra of water. When light in shallow depths, filtration offers sation. A using^ available some compen- color-correction filter (Table 8-5) over a up enough so that a certain amount of color is restored. The color red disappears at approximately 22 feet (6.7 m), orange vanishes at lens will break blue color NOAA Diving Manual —October 1991 Working Dive Procedures Figure 8-22 Diurnal Variation of Light Under Water When the sun is 90° above the is only reflected by three percent as it enters the water; nearly all the light will be transmitted below the surface. horizon, 0sable its light Angle of Sunlight Low-angle sunlight is nearly totally reflected by the water's surface. Water s surface Source: NOAA (1979) approximately 40 feet (12.2 m), and yellow disappears (Murphy approximately 80 feet (24.4 m) of water, and no filtration of the lens can restore it (Figure 8-23). Color absorption and transmission of light under water, see at correction filters that selectively subtract ultraviolet light and correct the blue readily available (Murphy shift found in seawater are 1987). These filters, which 1987). For additional information on the Section 2.8. Artificial light illuminates underwater situations and also brings out the color inherent in the subject. effective in water, artificial light are designed and color-balanced for available light at closer to the subject than depths ranging from 15-50 feet (4.6-15.2 m), can be The attached to and removed easily from the camera while under water. Because such filters subtract from the of light reaching the film, however, slightly amount longer exposure times are required October 1991 — NOAA when they Diving Manual are used To be must be used much would be necessary in air. and more powerful the light, the more it will compensate for the inherent blue of seawater. By varying distance and power, different balances can be obtained; a water-blue background with a slight hint of color can be achieved as easily as brilliantly illumicloser 8-35 Section 8 Table 8-5 Color Correction Figure 8-23 Selective Color Absorption of Light as a Function of Depth in Clear Ocean Water Filters ( Exposure Underwater path length of the increase Filter light (feet) 1 CC CC CC CC CC CC . 2 . 5 . 8 . 12 15 05R 10R 20R 30R 40R 50R 1/3 1/3 1/3 2/3 2/3 1 For distances of greater than 15 feet (4.5 m), composite the appropriate number stops in of units filter filter with can be used. Adapted from NOAA (1979) nating the subject and completely obliterating the water quality. Many good electronic flash units are made for underSome offer an underwater wide beam for use with wide-angle lenses, others a narrow beam that may penetrate the water column more effectively. (For water use. a list of underwater strobe units, see Table 8-6.) variance in exposure is when using The different strobe units caused by: • • • • The light beam angle; The strobe reflector material; The watt-seconds; and The guide number of the strobe. Most strobes designed underwater use come with for an exposure guide (see Table When i 8-6). using macro photography under water, divers have a choice between manual and through-the-lens (TTL) flash systems. Although each has its advantages and disadvantages, the manual system is less expensive, has underwater quick-disconnect features, and offers better exposure control. In general, the system is manual method for macro photograsystem does, however, have The automatic TTL some advantages. For example, because the length of the flash is controlled by the amount of light reflected from the subject back through the lens, the system automatically compensates for varying distances and phy. reflectivity. This system also provides a visual signal confirming that the correct exposure was used. Auto- TTL systems can be switched readily to the manual mode as needed; Table 8-7 lists some TTL mini strobes that are suitable for macro photography. matic Tests should be ous speeds. It is 8-36 amount of blur caused by of the camera during exposure. Table 8-8 lists exposure compensations for underwater photography that should be used as a starting point for work with adjustable cameras. These recommendations are based on the following conditions: bright sunshine between 10 a.m. and 2 p.m., slight winds, and availa- other factors can significantly affect photographic These shutter speeds should freeze important to conduct tests before advisable possible. movement 1/100 or 1/125 of a before the dive to establish when shooting with ble light to use shutter speeds of if the action and reduce the about 50 feet (15.2 m). The degree of visibility, the amount of particulate matter in the water, the reflective qualities of the bottom, and made correct exposures with any unit that uses films of vari- second, Derived from Church 1971 Derived from Church (1971) the preferred flash underwater results, visibility of and thus it is NOAA Diving Manual — October 1991 ( Working Dive Procedures Table 8-6 Manual and Through-the-Lens (TTL) Strobes for Closeup Photography Mfg. Akimbo Head Weight Model Size In Air Subatec S-100 6 x 3.5" 2.75 lbs. Beam Depth Beam Tested Angle Spreader 500 ft. 96 No Color Temp. Batteries Removable 4,500 K Rechargeable Pack Power No. of Recycle U/W Slave TTL Modes Flashes Time Guide Mode Mode Subatec S-200 TTL 6 x 3.5" 2.75 lbs. 500 ft. 96 No Removable 4,500 K Rechargeable Pack Scuba Helix Helix Ikelite Ikelite Whale Strobe TTL 7 x 4" Aquaflash 28 6 x 5" Aquaflash 28 TTL 6 x 5" Substrobe 150 TTL 10 x 6" 2.3 lbs. 165 ft. 65 Ikelite Yes 4 AA Dry Cells 5,600 K (95) II 3.8 lbs. 165 ft. 65 Yes 5,600 K 6 3.8 lbs. 165 ft. 65 Yes 5,600 K 10 x 6" 8 lbs. lbs. 300 300 ft. ft. 110 110 No No Nikon SB-103 7 x4" 2 lbs. 160 ft. 65 Yes 5,500 Nikon SB-102 8.5 x 5.5" 4.3 lbs. 160 ft. 79 Yes Oceanic 3000 Master See & Sea YS-150 See & Sea YS-100 TTL 9 x 5.7" 9.5 x 5" 6 x 4" 4.8 lbs. 5.4 lbs. 2 lbs. 300 350 200 ft. ft. ft. 110 100 65 No No Yes Subsea 11 x 6" 8.5 lbs. 350 ft. 150 No Yes Yes Yes No Yes Yes Yes Yes Yes Yes No Yes Yes Yes No 8 Full 130 7 sec. 32 1/4 450 2 sec. 16 Full 80 10 sec. 40 1/4 300 sec. 22 10 sec. 1 1 1 11 Full 80 1/4 300 1 150 300 600 6 sec. 3 sec. 2 sec. 22 125 250 500 6 sec. 3 sec. 32 22 2 sec. 16 130 450 12 sec. 4 sec. 24 sec. 5.6 1/4 1/2 4 AA Dry Cells Full 1/4 1/4 sec. 16 11 12 1/16 1,400 6C Full 33 1/4 120 400 14 sec. Dry Cells 5 sec. 16 1/16 1,200 2 sec. 8 350 650 3 sec. 22 sec. 16 100 200 5 sec. 22 3 sec. 16 5,500°K Built-in High Rechargeable Pack Low 1 1 Removable Full Rechargeable Pack 1/2 4 AA Dry Cells Full 130 12 sec. 1/2 12 sec. 32 22 12 sec. 16 1/8 250 450 900 12 sec. 11 150 100 50 175 250 325 5 sec. 22 3 sec. 16 5,400 K (80) Subsea Mark 150RG Yes 11 sec. 1/4 Graflex Yes 2 sec. 1/4 Full 5,400 K Yes 16 Removable 5,700 K 40 22 3 sec. Rechargeable Pack (95) No 4 sec. 1/2 K Yes 150 250 350 500 1 1/2 Full (95) Yes 8 Removable 4,800 K No sec. 1/4 Rechargeable Pack 4,800 K 225 TTL AA Yes 16 Dry Cells 6 (95) 7 AA Dry Cells (95) No 22 3 sec. 2 sec. 1/8 Berry No 4 sec. 1/8 Akimbo No 150 250 350 500 1 1/2 Removable 5,500 K Rechargeable Pack 2 sec. 11 Courtesy Gen Murphy starting to photograph; these variables can cause exposures to vary by as much as 4 or 5 stops (see Section 2.8.1.3). strobe flash systems, flash bulbs (clear bulbs for dis- tance and blue bulbs for closeups) can effectively under water (Table 8-9). still be used The longer water effectively filters the clear bulbs with blue so October 1991 — NOAA be aware that the pressure at great depth can cause bulbs to implode; divers have been cut Although most underwater photographers now use column that the light balances for daylight film. Divers should Diving Manual bulbs in when changing deep water. Incandescent lights that are powered either by battery or by a topside generator and that are a must motion picture work can also be used in still for photogra- phy. Incandescent light does not penetrate water as 8-37 ' Section 8 Table 8-7 Through-the-Lens (TTL) Mini Strobes for Automatic and Manual Exposure Manual Angle Beam Color Guide Model (diameter) (degrees) Spreader Temp. No. Batteries No. Power Time Modes (seconds) Flashes Whale Strobe TTL 7x4" 65 Yes 5,600 K 32 4AA Beam Mfg. Berry Scuba Helix Ikelite * u/w* Head Size 6x5" Aqua Flash 28 TTL Substrobe MV Full 7 1/4 2 (95 degrees) II 5,600 K Yes 70 6AA 40 1/4 No 65 " 10 Full (95 degrees) 4.5 x 3.5" Recycle 5,800 K 20 4 AA 1 5 Full 130 450 80 300 250 Depth Tested Extras (feet) Confirm • 165 Signal • Test Fire • • Slave Confirm • Signal Test Fire • Inter- 165 300 changeable sync cords SB-103 Nikon 7x4" Sea & Sea YS-100TTL 5,500 K Yes 65 4 24 AA Full 12 130 1/4 4 450 1/16 1 1,400 (95 degrees) Speedlight 6x4" Yes 65 5,400 K 4 32 AA 12 12 12 12 Full (80 degrees) 1/2 1/4 1/8 Confirm • 160 Signal 130 • Slave 250 450 900 • Audio 200 Ready Exposure • Calculator Sea & Sea * YS-50 TTL 6x3" No 72 5,400 K 4 22 AA 10 Full 200 140 *U/W Guide Number based on ISO 50 film with strobe set on full power manual. 'Recycle times and number of flashes based on alkaline batteries. Rechargeable nickel-cadmium batteries produce faster recycle times but fewer flashes. Courtesy Geri Murphy Table 8-8 with brackets that permit them to be either mounted or Exposure Compensation for Underwater Photography hand held. 8.12.1.3 Selection of Film Number of f-Stops to Depending on the quality of the documentation required Increase Lens Opening Over Normal Above-Water Depth Exposure of Subject Just under surface 6 feet 20 30 50 feet feet feet 1 m) (6.0 m) (9.0 m) (15.0 m) 1/2f-stops 2 f-stops (1.8 2 1/2 f-stops 3 f-stops 4 f-stops Adapted from NOAA (1979) by the diver/scientist, a wide variety of both blackand-white and color films is available (Table 8-10). The sensitivity of film is measured according to an American Standards Association (ASA) rating that ranges for most purposes from 25 to 400 ASA. There are slower and extra high-speed emulsions available for special purposes and techniques. Film is merely a base on which an emulsion of lightsensitive, microscopic grains of silver halide has been placed. These particles react to light in various ways that affect the following: well as electronic or flash bulb light, and these lights are also clumsier to use. Lighting arms and brackets or extension cords allow off-camera light to be placed in many positions (Fig- ure 8-24). Lights should not be placed on the camera • Grain, which is the clumping of silver halides. High-speed film clumps more rapidly than slower film, and enlargements show graininess more than small pictures. Grain tends to destroy the sharpness and detail of a photograph, but it can be reduced or increased in processing. To obtain sharp water directly can curtain off the subject matter and tures, film of the finest grain should be used, unless increase backscatter. Underwater exposure meters, pri- the light marily of the reflected-light type, are manufactured necessary. lens axis, 8-38 because lighting suspended particles in the is insufficient NOAA pic- and a high-speed film Diving Manual is — October 1991 Working Dive Procedures Table 8-9 Underwater Photographic Light Sources Type of Depth Lighting Limit(ft) Noturol 50 100 to Control Accuracy Light Subject of Effects Limiting of Color for the Human From Visibility Rendition Eye as Camera Will See If Light fair to poor (predominantly green) very good scattering absorptivity fairly good very good absorptivity none Flood Ability to Factors Means Duration of Power Extent Requirement of Use Intensity Determining Exposure good meter none guide number determined by experiment high (sec) Remarks Scattering continuous good at surface general but decreases with depth /ery good relatively low continuous scattering ( general, 2 1 to2kw) especially at greater depths none Flash bulbs absorptivity. good fairly poor fair 1 50 to 1 100 guide numbers h.gh general self- scottermg contained replace bulbs battery none Electronic absorptivity good foirly poor fair to scattering flash very good 1 1 1 2 000 000 very high to or Diver must general Electronic guide numbers, self- automatic contained flash battery probably faster is better than regular flash for use under water Adapted from • Resolving power, which the ability of the film to is hold fine details; resolving power the number will record distinctly. is measured • in made from be viewed the finer the grain, the higher the resolving power. • Latitude the over- and under-exposure toler- is ance of a film. Wide-latitude film is best under water because a picture can be obtained even when the exposure film • this film, and the resulting picture can in its true perspective shortly after the Storage and is shelf-life. The storage and shelf-life often an important consideration. For atively high storage temperatures but may rel- shift with a 4 f-stop variance, while color transparen- color with aging. Professional films, however, remain cies of short latitude will tolerate only a constant in color but must be stored under temper- A deviance. ing 1/2 f-stop wide-latitude film should be used whenever a good picture is make ature-controlled conditions. necessary and bracket- impractical. Color negative films, which are is used to color prints, offer better latitude A fast film, such as Eastman Kodak Ektachrome film that has an ASA value of 200, can produce very than color reversal films, which are used to pro- acceptable results, with good depth of field at moder- duce color ate light levels. In low light conditions, the effective ASA be increased four times to slides. Color balance, which film. Films are made is to problem only of color match the color temperaa tures of different light sources-daylight, tung- value may ASA 800. although this film speed requires special processing (see Table 8-11). Black-and-white films are available are color-balanced for outdoor use in sunlight and ASA of 1200. As ASA's are approached, however, black-and-white films lose shadow detail during developing. When taking underwater pictures with a flash or for use with electronic flash systems. strobe, both the f-stop generated sten, strobe, etc. Processing and printing greatly affect the ultimate color balance. Both color reversal and color negative films are daylight • work under water. example, over the counter films can withstand white negative film will allow sufficient exposure • still developed. is of film not exact. For example: black-and- is used most commonly for Slides or black-and-white or color prints can be related directly to grain: is (1979) Color reversal. Color reversal (positive color) film is of lines per millimeter that the film It NOAA Contrast the difference in density between darkest is shadow and trast is brightest highlights. Under water, con- low because of the diffused results, film with high contrast light. For best should be used under water. October 1991 films; both — NOAA Diving Manual that can be processed to achieve an higher by the strobe or flash and the available light (f number registered on the light meter) must be considered. In this case, the aperture must be adjusted to accommodate the stronger of the two light sources or a flash distance must be selected that will equalize the natural and artificial light levels. 8-39 Section 8 Figure 8-24 Lighting Arms and Brackets for Strobe Systems Hydro Vision International Photo Cobra Flash Arm Top: Sea & Sea YS 100 TTL Strobe Insert: Sea & Sea Motormarine Helix Aquaflush Nikonos Speedlight SB-102 and SB-103 8-40 28TTL Insert: Helix Universal Slave Strobe Courtesy Sea & Sea, Hydro Vision International, Nikonos®, and Helix NOAA Diving Manual —October 1991 i Working Dive Procedures Table 8-10 Films Suited Still for Underwater Use Dayligh Resolving t ASA Film Type Description Sharpness Grain Power high very high Daylight Color Eastman Kodak Ektachrome 64 A medium-speed 64 color slide film for general picture-taking purposes, e.g., Daylight macro, closeup, Eastman Kodak Ektachrome 200 A high-speed 200 flash, available light deep available Eastman Kodak Ektachrome 400 A 400 very high-speed color slide deep Eastman Kodak Kodachrome 25 25 Daylight Eastman Kodak Kodachrome 64 64 ~ film for (e.g., available light) Moderate speed, daylight balanced (e.g., macro photography) high A medium-speed high extremely extremely closeup, (e.g., high fine color slide film for general picture-taking Daylight high fine (e.g., light) general picture-taking purposes Daylight very high color slide film for general picture-taking purposes Daylight fine high fine flash, available light) Eastman Kodak Kodachrome 400 A 400 " very high-speed color slide film for extremely very fine high ~ ~ ~ Slow-speed film for a very high degree of enlargement very extremely very high fine high Medium-speed very extremely high high fine very very high fine very extremely high fine general picture-taking Daylight deep (e.g., available light) Vericolor II S 100 Professional color negative film for short exposure times (1/10 sec. or shorter) Black and White Panatomic X 32 Plus-X Pan Tri-X film for general purpose photography where a high degree of enlargement is required 125 Pan 400 purpose film when the enlargement required is Fast, general degree of medium not great Verichrome Pan Medium-speed film for general purpose photography where a high degree of enlargement is required 125 Note: Proper color balance occurs when colors are reproduced as they actually are. Making warmer or colder tones cameraman. All color films should be exposed properly and have good At more than ± Vfc stop, color reproduction differs noticeably from the original color. aesthetic decision of the ± 1 /2 stop. high is Adapted from Infrared film has opened up new possibilities in underwater photography; however, because of drastic color changes, infrared film color documentation. ASA in 20 at 1/60 sec feet (6.1 October 1991 at yellow filter (1979) should be used to exclude exces- sive blue saturation. starting at ASA 8.12.1.4 an f-stop of 5.6 on a sunny Many m) of water — NOAA A NOAA not suitable for scientific Kodak recommends 100, but underwater tests have 50 exposed day is sure. an color acceptability at shown will give Diving Manual that proper expo- that it Time-Lapse Photography is biological and geological events occur so slowly neither possible nor desirable to record them 8-41 Section 8 Table 8-11 Processing Adjustments for Different Speeds Kodak Kodak Kodak Kodak Change Ektachrome 200 Ektachrome 160 Ektachrome 64 Ektachrome 50 in Film Film Film (Daylight) (Tungsten) (Daylight) Professional (Tungsten) 800 400 Normal 200 100 640 320 Normal 160 80 250 125 Normal 64 32 200 100 Normal 50 25 the time the first developer by + + 5 1/2 minutes 2 minutes Normal — 2 minutes For Kodak Ektachrome film chemicals, Process E-6. Adapted from continuously on film. Time-lapse photography, which permits the scheduling of photographic sequences, is be able to swim in and out of scenes with as unnecessary movement as possible. To cover the solution in such cases. This technique has been should be planned. An and many other phenomena. It is particularly useful for underwater studies, where, in addition to investigating slow processes, the inconvenience and cost of frequent site visits make other photographic good amateur work is generally in one area. techniques impractical. for Modern technology has greatly improved underwacamera systems that are triggered automatically by means of standard timing devices or by remote command. The time-lapse interval (the time between ter photographs) is determined by the nature of the event 5 feet (1.5 (1979) little a single subject adequately, several dives used widely for years for studying plant growth, weather patterns, NOAA m) average for topside shooting m) used 1:5 (1 foot (0.3 in for every exposed). Photographers should consider using a tripod if the objects to be photographed are Artificial lighting is critical motion picture work deeper than approximately 30 feet (9.1 m). Surface-powered cumbersome lights are but more reliable and longer-lasting than batterypowered lights. Ideally, a buddy diver should handle the lights, which frees the photographer to concentrate on filming techniques. being studied, the available equipment, environmental conditions, and cost. The time interval can vary seconds or minutes to hours or even days. of a long-term study using current technology record being made from 8.12.2.1 Selection of Film An example is the of the scouring and erosion of sand around offshore platforms and pipeline installations during storms in the North Sea. In this instance, three pictures per day were taken over a period of 1 month, using a stereo-camera system (Photosea Systems Inc. 1984). A wide range of motion picture film in both 100 foot (30.5 in tions of the film. This film also has a broad range of color correctability that can be applied during print- and is faster and has more latitude than Eastman Ektachrome Commercial 7252. Eastman 7294 also is used frequently for filming at greater depths and on ing Because time-lapse systems remain unattended for long periods, they must be thoroughly checked out for reliability, leaks, buoyancy, and anchoring before deployment. They must also be maintained and stored carefully when not in use. darker days because it has a higher ASA be processed as easily as 7291 can, and quality that allows it Eastman Video News Motion Picture Photography Almost all motion picture cameras can be adapted for underwater use; such cameras should be confined in rugged, reliable underwater housings that will with- rating, it can has a fine it be edited with 7291 scenes. films 7239, 7240, and 7250 are to improvements over Eastman Ektachrome 8.12.2 available for is m) and 400 foot (121.9 m) rolls (see Table 8-12). Eastman Color Negative Film 7291 should yield the best picture information in both highlight and shadow porunderwater photography EF (daylight) 7241 and Eastman Ektachrome EF (tungsten) 7242, both with respect to speed and warmer tone (highlight) characteristics, which lend a pleasing overall effect to the photographs. stand rough handling. All camera controls should be outside the housing and should be as simple as possible. The camera also should be balanced properly to be neutrally buoyant. The underwater cinematographer must position the camera himself or herself and must 8-42 8.12.2.2 Procedures Because all film is sensitive to heat, it should not be stored in the sun or in hot enclosures. In addition, film should always be loaded in subdued NOAA Diving Manual light. Other pro- — October 1991 Working Dive Procedures Table 8-12 Motion Picture Films Suited for Underwater Use Film ASA Type Description Black and White Reversal Eastman Plus-X 7276 . . . 50 Daylight A medium-speed panchromatic reversal film characterized by a high degree of sharpness, good contrast and excellent tonal gradations Reversal Eastman Tri-X 7278 . . . . A high-speed panchromatic 200 Daylight lent tonal Reversal Eastman 4-X 7277 . Negative Eastman Plus-X 7231 . . . reversal film that provides excel- gradations and halation control 400 Daylight A 80 Daylight A medium-speed panchromatic very high-speed panchromatic reversal film negative film for general pro- duction Negative Eastman Double X 7222 . A high-speed panchromatic negative 250 Daylight latest Negative Eastman 4-X 7224 . advances in speed granularity representing film An extremely high-speed panchromatic negative 500 Daylight the ratio film Color Reversal Eastman Ektachrome Commercial 7252 (Tungsten) Reversal Eastman Ektachrome EF7241 . . . Daylight 16 w/85 A color . reversal camera film, balanced for dayintended primarily for direct projection (after processing). However, satisfactory color prints can be made if they are balanced properly A high-speed color .160 . light Reversal Eastman Ektachrome . . . w/85 . . . 1 . . . filter - exposure, A high-speed color reversal camera film balanced for tungsten exposure, intended primarily for direct projection (after processing). However, satisfactory color prints can be made if they are balanced properly 80 A high-speed color reversal camera film balanced for daylight exposure, intended for use under low-level illumination both for color news photography and for high-speed photography. Satisfactory color prints can be made if they are balanced properly 60 Video News 7239 (Daylight) Reversal Eastman Ektachrome Video News 7240 (Tungsten) reversal originals from (Daylight) Reversal Eastman Ektachrome EF 7242 (Tungsten) camera film designed to provide low-contrast which color release prints (duplicates) of good projection contrast can be made filter w/85 B filter = 80 . . . .A high-speed color reversal Satisfactory color prints film, intended can be made for if use in daylight. they are properly balanced Reversal Eastman Ektachrome . . . w/85 B filter = 250 . . . No data Video News High Speed 7250 (Tungsten) Negative Eastman Color Negative 7291 (Tungsten) . w/85 II filter - 64 A high-speed color negative camera film designed for use in tungsten light and in daylight with an appropirate filter. It is characterized by accurate tone reproduction, excellent image structure, and wide exposure latitude. Excellent prints (duplicates) can be made from the original Adapted from October 1991 — NOAA Diving Manual NOAA (1979) 8-43 Section 8 cedures to be observed when taking motion pictures relief valves, are: external pressure • When 16-mm equipment, photographers using • • starting to film, the housed down to m), returned to the surface, and checked for leaks. The camera should be held if feasible, a tripod Protective shock-absorbing cases lined with books, • and camera floods in salt water, the best immediis to pack the equipment in ice and to keep frozen until it • the value and length of each scene are considered during the shooting. • • Different distances, angles, and exposures of each scene should be shot. • Scenes should not be rushed because the beauty of the sea can be lost • Only a few special when they only if the photographer is If ice camera should it in fresh At the end of the day's work, all camera equipment should be washed with fresh water. When the camera and housing are removed from the water, they should be placed in the shade immediately; this is especially true in the tropics, where even a minimal exposure to the sun can cause heat hurried. effects should be used, can be delivered to a repair not available, the is be flushed thoroughly by immersing water or alcohol. The length of scenes should be varied (some short, some long); this can be done in editing, but film if it to aid in the editing process. can be saved more informative than photography of which contain errors. ate action Photogiaphers should overshoot at the beginning to establish the scene If a many facility. • foam Actual underwater experience and experimenta- as steadily as possible; (custom-made or commercially and end of each scene Wearing a wool watch cap can keep water from the from dripping into the camera during tion are often bought and heavily weighted) should be used. • WD gear in a boat. (9.1 • • camera main40 or rubber are essential for transporting photographic camera should 30 fsw for reloading. meter. be put in the water, taken up diver's hair • When released. equivalent, towels, etc.) should also be on hand. real-time action. • is basic tool kit should be set tenance, and spare parts (0-ring grease, should film at 24 frames per second (FPS) to achieve At 24 FPS, most motion picture cameras attain a shutter speed of approximately 1/50 of a second. Such a shutter speed is necessary for interpreting f-stops when using an exposure A because the housing can flood when inside the and then camera housing to damage the film. are exceptional and an integral part of the picture. • The shooting but it from • is script should generally be followed, important to be flexible enough to deviate it if the situation so dictates. most UNDERWATER TELEVISION Significant advances continue to be ter television systems. Photographers should know their cameras thoroughly so that they can be used 8.13 effectively. for the scientific made tion, Procedures Underwater photographers may find the following hints helpful: • • Overweighting with plenty of lead makes a diver a much steadier photographic platform. A wet suit protects against even when • • it is rock and coral injuries not needed for thermal protection. and working diver with respect to hull inspec- damage assessment, improving working procedures and techniques, and diving safety. Excellent solid-state underwater color systems now are on the market that permit small, compact television cameras to be: (l) held in the hand, (2) mounted on tripods, (3) worn as an integral part of a diving helmet (Figure 8-25), (4) mounted on manned submersibles, or (5) used as an integral part of remotely controlled systems. Underwater video systems capable of operating at depths as Photographic equipment should not be suspended from lines on boats in a rough sea unless the line has a shock absorber incorporated into it. great as 35,000 feet (10,668 available. This capability, quality of cur- To rent video systems, has resulted in television replacing the extent possible, photographic sequences m) are now when coupled with the high The camera photography as the method of choice for underwater and technical documentation. When selecting an underwater video system, it is best to choose a system designed specifically for housing should be taken up open, regardless of underwater operation rather than to select a "surface" should be planned before the dive. • underwa- recording natural phenomena, conducting surveys, documenting experimental procedures, ship 8.12.3 Special in These advances offer great promise Cameras should be taken down to a habitat open unless the housing has a relief valve; pressure pre- vents cameras from opening at depth. 8-44 scientific NOAA Diving Manual — October 1991 Working Dive Procedures Figure 8-25 Video Recording Systems A. Handycam® System With Underwater Housing Courtesy Sony Corp. C. Diver Using Underwater Video B. of America Underwater Housing With Angle Lens Attached Courtesy Ikelite Underwater System System Photo by Jim Churcn October 1991 — NOAA Diving Manual 8-45 Section 8 Figure 8-26 Commercial Underwater Video System Courtesy Hydro Vision International, The system packaged for underwater use. Surface television cameras normally operate at high light levels and television Filming often are not sensitive enough for underwater condi- sive) as the selection of a tions. Further, surface cameras are sensitized to red Inc. selection of a lighting system for underwater is just as critical (and often as expen- camera. Although quartz iodide lights are often used for underwater work, their mercury or thallium light, while underwater cameras for use in the open sea lights are not as efficient as have maximum charge lamps because quartz provides a high red spec- the spectrum. camera also is sensitivity in the blue-green region of The dynamic range of an underwater critical if under the broad range of it is to be used effectively light intensities commonly encountered. To achieve these underwater needs, tral output that absorbed rapidly is seawater. in On the the only source that produces enough red to allow good underwater color filming. specifically is other hand, quartz iodide light dis- Another alternative is a water-cooled quartz halogen lamp that offers burn times of up to 3 1/2 designed low-light-level television cameras often are hours at 100 watts at depths to 250 feet (76 m). Like used; such cameras can record images at light levels as cameras, underwater lights are designed to operate at low as 0.0005 foot-candle at the camera tube while depths of several thousand feet maintaining a horizontal resolution of 500 meters). Specific factors to consider lines. In addition to operating at low light levels, these cameras can significantly extend the viewing range. Such sys- tems offer great potential for working under conditions of low visibility, where the diving scientist needs to observe or record the behavior of marine life without (i.e., several hundred when selecting a camera include the size and location of the battery pack, burn and recharge times, the size of the underwater beam angle, and an arm and bracket mounting system. Rapid advances continue in the development and miniaturization of videotape forlighting system for a video either artificial light or the veiling effect of backscat- mats. Miniature camcorders weighing less than 3 pounds ter that occurs with lighted systems. In addition to the (1.4 kg) have reduced the bulk of video systems optical characteristics of video cameras, other impor- permitted the use of high-quality 8 and buoyancy control; type of viewfinder; automatic versus zone focusing; automatic exposure control with manual override; and automatic white balance. Other options to consider are built-in microphones, zoom lenses, focusing for macro photography, housings, and tant features to consider include: size, weight, general ease of operation. 8-46 Underwater DC, 115 and mm video tapes. TV systems can operate from 12 volts 230 vac input power, which provides to operate either from large or small vac, or the flexibility diving support platforms. As with other television sys- tems, data can be viewed in real time on the surface or be stored for later viewing. The combination of a diverheld or helmet-mounted camera, a surface-based moni- NOAA Diving Manual — October 1991 Working Dive Procedures TV good diver-to-surface communication system permits the diver to act as a mobile underwater platform under the direction of the diving supervisor or a scientist on the surface. This arrangement not only permits real-time recording of events but greatly detach, or service a enhances diving safety by allowing the surface support wireless communication. team narrative tor, and to a monitor the activities of the diver continuously. This monitoring can be done either at the site on the surface or at a remote station or laboratory. Computer microprocessing technology also permits means that wide variety of data can be recorded, including video camera. For the diving scientist, this a information on such things as environmental conditions, weather, water conditions, and the results of experiments. Underwater TV is used in a variety (1) attached to submersibles, (2) the monitoring in are obtained of modes, including lowered by cable for mode when the camera is manipulated by a diver using either umbilical diving gear with hard- wire communications or a scuba diver with reliable is In either case, the diver's recorded on videotape, along with the picture. Commercial systems are available that are designed as an integral unit, including a full face on the output of the digital displays to be overlaid camera or to carry the camera-light module. The best results mounted mask, helmet- or hand-held camera, monitor, and complete facilities for two-way communications and videotaping (Figure 8-26). Divers usually can work with cable lengths up to 500 feet (152.4 m) if floats and buoys are used to reduce the drag and the possibility of fouling. Underwater television technology has reached the stage where it is preferable, in most cases, to underwater photography. Its advantages include: on-the-spot evalu- ation of results; instant replay; communication with use as a remote instrument, or (3) placed on or near a surface support personnel both for safety and assis- structure or habitat for long-term monitoring. Within tance in the evaluation of results; and cost-effective working depth limitations, divers October 1991 — NOAA may be asked to attach, Diving Manual duplicate films. 8-47 < ( 1 Page SECTION 9 PROCEDURES FOR SCIENTIFIC DIVES 9.0 General 9-1 9.1 Site Location 9-1 9.1.1 9.1.2 Methods Electronic Methods 9-1 Traditional 9-2 Underwater Surveys 9.2.1 Direct Survey Methods Indirect Survey Methods 9.2.2 Underwater Photographic Surveys 9.2.2.1 Underwater Acoustic Surveys 9.2.2.2 9-2 9.3 Underwater Recording Methods 9-5 9.4 Biological Surveys 9-6 9.2 9.4.1 9.5 9.8 9.9 9.10 9.11 9.14 9-8 9-8 9.5.2 Benthic Organism Sampling 9-9 9.5.3 Airlift Sampling Midwater Sampling 9-1 9-1 9-12 Shellfish Studies 9-13 Collecting Techniques 9-14 Tagging and Marking Techniques Botanical Sampling 9-17 9.8.1 Field Procedures 9-18 9.8.2 Collecting Techniques 9-18 9.8.3 Specimen Preparation and Preservation Artificial 9-19 9-20 Reefs 9-22 Geology 9.10.1 Mapping 9-22 9.10.2 Sampling 9-26 9.10.3 Testing 9-31 9.10.4 Experimentation 9-31 Microphysical Oceanography 9-32 9.11.1 Emplacement and Monitoring 9.1 1.2 Planktonic Studies 9-33 9.11.3 Use of Dye Tracers Water Samples 9-34 of Instruments 9-32 9-34 9-36 Archeological Diving 9-37 9.12.2 Shipwreck Location and Mapping Shipwreck Excavation 9.12.3 Artifact Preservation and Salvage Rights 9-40 9.12.4 Significance of Shipwreck Archeology 9-40 9.12.1 9.13 9-4 Plankton Sampling 9.1 1.4 9.12 9-3 9.5.1 9.6.1 9.7 9-3 9-7 Estimating Population Densities Biological Sampling 9.5.4 9.6 9-2 Capture Techniques 9-37 9-41 9.13.1 Nets 9-42 9.13.2 Seines 9-42 9.13.3 Trawls 9-42 9.13.4 Diving on Stationary Gear The Use of Anesthetics in Capturing and Handling Fish 9-42 9-42 9-43 9.14.1 Response 9.14.2 Selecting an Anesthetic 9-43 9.14.3 Application of Anesthetics 9-43 9.14.4 Diver-Operated Devices 9-46 to Anesthetics < i PROCEDURES FOR SCIENTIFIC DIVES 9.0 GENERAL Diving is widely performed phenomena and to SITE LOCATION 9.1 to observe underwater acquire scientific data, and this use To study any map a base region carefully, is it necessary to plot on the precise location from which data will be of diving has led to significant discoveries in the marine obtained (Holmes and Mclntyre 197 1 ). This method that can be used to make valid observations and take accurate measurements. Using equipment and techniques designed specifically for underwater use, the important diving scientist can selectively sample, record, photo- of the seafloor, a scale of sciences. In some instances, diving is the only if there is a need location several times during a study. base map depends size of the area to is especially to return to the The same scale of the on the detail of the study and the be investigated. In geological mapping water, and fish behavior studies, requires diving to be inch to 200 yards (2.5 cm to adequate for reconnaissance surveys. In archeological and some biological studies, a much more detailed base map, with a scale of inch to 30 feet used throughout the entire project, while other research (2.5 may contain the proper scale or sounding density, make graph, and field observations. Some such as ecological surveys, benthic inventories research, in shallow require diving only as an adjunct to submersible, remote sensing, or surface ship surveys. Regardless of the project or the role that diving plays, marine research using diving as a tool has been important in understanding the ocean, The measured its organisms, and its dynamic processes. is minutes and seconds instead of hours (unless the saturation diving mode is used). Long underwater work periods necessitate decompression times twice as long as the actual work time on the bottom: the cost-effectiveness of scientific diving therefore depends on how efficiently scientists can perform their tasks. Efficiency under water requires good tools, reliable instruments that can be set up rapidly, and a well-thought-out task plan. Until recently, there was almost no standardization of the equipment and methods used to perform scientific research under water, and in many cases the instruments, tools, and techniques were (and still 1 is 1 cm to 9 m), may be required. If existing charts are) improvised by individual meet the specific needs of the project. However, now that the value of scientific diving has been widely recognized, scientists are becoming concerned about the accuracy and replicability of their it do not may be necessary to use echosounder survey techniques to construct a bathymetric map of the bottom before starting the dive. Gross features can be delineated and bottom time used more efficiently diving scientist or technician's working time in 183 m) good bathymetric map if the diver has a of the study area. If published topographic charts are inadequate, the sounding plotted on original survey boat sheets of a region (made by NOAA's National Ocean Service) can be contoured and will usually provide adequate bathymetric control for regional dive surveys. bottom traverses, it will If the survey plan requires be necessary to provide some means of locating the position of the diver's samples and observations on the base chart. Techniques used to search for underwater sites fall into two general categories: visual search techniques and electronic search techniques. The results from the latter must be verified by divers after the specific site has been located. scientists to data and results and are increasingly using statistically valid and standardized methodologies. Through neceswho want to work under water must be sity, scientists proficient both in their scientific discipline and as divers, inventors, The purpose and mechanics. of this section is October 1991 to to describe gather data. — NOAA The some of the Diving Manual Methods great majority of diving is carried out in nearshore waters where surface markers, fixed by divers over strategic points of the work site, may be surveyed from the shore using well-established land techniques, including the theodolite, plane table, and alidade, or from the procedures used in diver-oriented science projects. These methods are intended as guidelines and should not be construed as the best or only way to perform underwater surveys or 9.1.1 Traditional or, sea, using bearings from a magnetic compass preferably, measuring horizontal angles between known points with a sextant. Small, inexpensive, and rugged plastic sextants are commercially available, and techniques for using them are simple to learn. Although sextants have limitations, especially when 9-1 Section 9 UNDERWATER SURVEYS they are used from a small boat, they are generally 9.2 sufficiently accurate to be useful. A At the other extreme in terms of complexity is a site relocation method used successfully by many scientists; in landscape; these include direct and indirect surveying method, lineups and landmarks on shore are sighted this visually, without the use of artificial aids. Basically, once the site is located and the boat anchored over it, scientists take a number of sightings of various nearshore landmarks (such as trees, hills, and power poles) and align them visually so that when the boat is repositioned the landmarks line up the same way. The only drawbacks to this method are that the work must be conducted near shore and the visibility must be good the shoreside landmarks to be seen. When in order for survey used during the directly over the weights anchoring lie initial them the selected underwater features; the best plan is to to wait for a calm day at slack tide. In some cases anchors this is in may be advisable to leave the seabed place after the floats have been cut away. If contemplated, the anchors should be constructed to rise slightly may it above the surrounding terrain so that they be seen easily on the next of syntactic foam may be visit. tied to the Small floats made anchors below the surface with a short length of polypropylene line to aid in relocation. However, because biological fouling soon obscures any structure used, expensive, highly painted markers generally are not appropriate. Floating markers, even seen if they are small and badly fouled, usually can be if they protrude a short distance above the surrounding substrate. Once system of markers established and fixed relative to is methods used to survey the underwater is methods. Direct methods require diver-scientists to measure distances themselves, while indirect approaches use photography or acoustic means to determine distances, angles, and other features. 9.2.1 Direct Survey Methods With the exception of long distance visual triangulation, many of the methods used in land surveying can several lineups have been established and proven, they should be diagrammed in a notebook that is kept in the boat. These methods allow divers to establish the locations of major features in the working area accurately. If buoys are used for location, particular care is needed to ensure that the surface floats variety of the transect, grid, or other also be used text under water. on surveying A review of a standard college provide the scientist with some will basic surveying concepts, while Woods and Lythgoe (1971) give an excellent description and review of methods that have been devised specifically for work under water. In most diving surveys, distances are measured with a calibrated line or tape. However, measurements done under water seldom need to be as accurate as those on land, and the use of an expensive steel tape is unnecessary. Additionally, most ropes or lines will stretch and should be used only if the measurement error resulting from their use is acceptable. A fiberglass measuring tape that has a of stretch and is marked in feet minimum and inches on one side and meters and centimeters on the other commercially is come in an frame with a large metal crank to wind the tape back onto the reel. They are ideal for most purposes and require no maintenance except for a fresh water available (see Figure 9-1). These tapes open plastic rinse and lubrication of the metal crank. No matter what measuring method is used, especially if long distances are involved, the lines or tapes must be kept on reels to prevent tangling or fouling. In clear waters, optical instruments can and have been used to measure permanent features on the shore, the diver should record both distance (range finder) and angles between objects the position of selected features within the working for triangulation. area in relation to the buoy array. The first step in surveying any area is to establish a horizontal and vertical control network of accurately located stations (bench marks) in the region to be mapped. Horizontal control 9.1.2 Electronic Methods a Electronic positioning methods are excellent, but they are also expensive. If cost is no object or extreme accuracy of station positioning and marking is required, map is the framework on which of features (topography, biology, or geology) to be constructed; such a control provides a locating the detail that is means of makes up the map. Vertical and may be obtained control gives the relief of the region several highly sophisticated electronic ranging instru- by stadia distance and ments may be used. Rough measurements can be made by comparing Satellite positioning equipment can few meters of the desired Loran equipment, although less accurate, is vertical angles or by spirit leveling. position a scientist within a differences in depth using a diver's depth gauge, but location. measurements may be inaccurate readily available at relatively low cost. 9-2 surface is if the irregular sea used as the reference point. NOAA Diving Manual — October 1991 Procedures for Scientific Dives Figure 9-2 Figure 9-1 Fiberglass Measuring Bottom Survey Tape in Courtesy Forestry Suppliers, High-Relief Terrain Inc. One method that has worked well in areas of high where echosounders are not satisfactory is relief described below (Hubbard 1978). • Along a convenient axis (N-S, E-W, etc.), place two permanent poles, one on either end of the survey area. • Stretch a line between them to serve as a fixed centerline. • At Source: by the intervals prescribed the irregularity of the terrain, place additional poles identified by a taut-line • some buoy may make the Lay out the lines sites permanent grid is more of methods described with respect to surface positions. tie-in points. If a between the centerline The detail to appear on the finished poles. terrain has significant relief, horizontal changes can be measured by moving away from each centerline pole, as shown in has been completed. Figure 9-2. In areas of significant terrain, it difficult to is maintain an accurate horizontal measurement. Knowing the difference in depth (y) between the two points (from a calibrated depth gauge or several depth gauges) and the measured slope distance (z), the horizontal distance (x) can be calculated is located is located first and the detail is located in a separate operation after the control survey On other surveys, the control and the detail are located at the • map by moving from the control networks (bench marks) to the features to appear on the finished map. On some surveys, the control If the Section 9.1.1 locates the site in visible. desired, place poles at intervals to those (1979) Determining the two end points of the centerline by the perpendicular to the centerline by using the centerline poles as comparable The use sort of coding. NOAA and size of the area method is preferable if same time. The former long-term observations are to be carried out in an area, for example, around a permanently established habitat. The latter technique reconnaissance studies are being is preferable in remote regions or if in made areas that will not require the re-establishment of stations. easily using the formula: x= V z 2 When must be taken Survey Methods 2 . Indirect underwater surveying involves techniques using a depth gauge over a period of hours, tidal fluctuations staff or 9.2.2 Indirect y into account. bench mark should be established A reference at the begin- ning of the survey, and readings should be taken at the that do not require the diver physically to measure angles and distances using tapes, lines, protractors, etc. Indirect underwater surveying currently is performed using either photographic or acoustic methods. reference during the period over which depths are being measured in the survey area. from each of the centerline By going poles, a in either direction complete Dathymetric survey can be conducted with considerable accuracy. October 1991 — NO A A Diving Manual Underwater Photographic Surveys Obtaining reliable measurements by means of 9.2.2.1 photography —photogrammetry—though not as advanced 9-3 Section 9 under water as on land — is a tool being used with increasing frequency. Limited visibility major drawbacks is one of the in its application. recording changes with time. Subtle changes in often recorded on sequentially obtained exposures of the same area alone is or station can be missed if memory costly systems can be used to some of the problems A methods. Photographs with appropriate scales in the field of view can be useful in measuring objects on the seafloor and More complex and avoid that arise with these simpler high-frequency sonic profiler (Figure 9-3) can rapidly measure underwater Such 1977). not a factor, the sonic profiling is way the best (Dingier et al. and beyond the means of most researchers. technical support If cost sites a device, however, requires electronic method is by far of obtaining an accurate representation of small-scale subaqueous bed forms. relied on. Photographic transects are useful in showing variations over an area or changes that occur with depth. In the acoustic equivalent of direct trilateration. In photogrammetry was conducted because of the technical difficulties in producing known corrected lenses and maintaining altitude and constant are interrogated sequentially from within their estab- the past, little true depth and because of the high relative relief of many bottom features. However, improved techniques have been developed that allow increased accuracy and flexibility. Recent computerization of photogrammetric plotting equipment has reduced technical difficulties considerably. To improve mapping for detailed archeological studies, photographic towers may be used (Bass 1964, 1968; Ryan and Bass 1962). The progress of excavation in Acoustic Grid. This method of underwater survey simplest form, three acoustic transponders are placed at positions on the sea bottom. lished grid, occurs is sound in and the time delay before each response delay in time can be related to the distance between the and each of the transponders. Transponders are implanted and their positions are determined using direct underwater survey methods. interrogator The interrogator produces a consistent series of photos that can be compared easily when analyzing the data. The tower ensures that each photo is taken from the same point of view, thus simplifying follow-on dark room procedures. A The process however, a perspective view that requires is a small, hand-held directional sonar device that has a digital readout of the time delay. diver, positioned is, These transponders measured and recorded. If the velocity of seawater is known for that area and time, the each area can be recorded with grid photographs taken through a hole in the top of the tower. This approach photograph is its visually at the first transponder is The above the point to be surveyed, aims and takes three readings. repeated for the other two transponders. Ideally, the data are sent to the surface via communications an underwater In the absence of this equipment, link. the data should be recorded on a writing slate attached directly to the interrogator. The accuracy of this system correction for the difference in scale and position of can be increased significantly by using four or five objects. transponders. A series of stereophoto pair photographs may be taken of sites for three-dimensional viewing under a stereo-viewer. More important, it is possible to make three-dimensional measurements from such photos. The use of wide-angle lenses, such as a 15-mm lens, permits detailed photographs to be taken that cover from short distances. Bass (1978) recomand divided into 6.6 foot (2 m) squares. These squares are then excavated and photographed individually. large areas mends that rigid metal grids be constructed Because so many variables affect the velocity of in seawater, errors in measurement can have a significant effect on the resulting mathematical analysis. For example, sound velocity measurements in very shallow water can be affected seriously by errors in recording temperature. Accurate results depend on keeping the salinity and temperature measurement errors small enough so that the errors in velocity are below sound the inherent equipment-introduced errors. More sophisticated versions of the acoustic grid survey system are available, and directly. Underwater Acoustic Surveys Another method for conducting bottom surveys 9.2.2.2 involves the use of sonic location beacons (pingers). These devices are particularly useful if there is a need to return to specific locations. The system may consist of small (the size of a roll of quarters) pingers, which can be placed receiver. at the site of interest, specific frequencies to differentiate 9-4 and a diver-held The pingers can be tuned by the diver between sites. to many of these read out range Although more convenient may to use, system be created by variability in speed of sound. Compact and reasonably priced sound velocimeters are now available that permit in-situ measureinaccuracy ments to still be used immediately as survey system correctors. The acoustic site is visited grid is particularly valuable when a repeatedly to measure features that vary over time, such as the motion of sand waves. Another advantage of this system is its internal completeness. If the geodetic location of the site NOAA is not important and Diving Manual — October 1991 Procedures for Scientific Dives Figure 9-3 High-Frequency Sonic Profiler its inherent mobility and flexibility are distinct advan- tages except in situations where job requirements make the acoustic grid or one of the direct methods preferable. Under measurement certain conditions, the phase system can be more fully utilized if diver towing tech- niques are employed. In this case the position of the diver relative to the support ship must be monitored continuously, which increases both ease of operation and accuracy. Combining the phase measurement system with a good diver-to-surface communication system results in an excellent survey procedure. 9.3 UNDERWATER RECORDING METHODS The simplest and most widely used method for recording data under water involves using a graphite pencil on These records a white, double-sided plastic board. are sufficiently permanent to withstand normal handling Photo Tom Harman during a dive. Since most divers use abbreviations and shorthand in recording observations and species names, however, the notes should be transcribed as Wax soon as possible. only relative position and motion within the site are to be measured, the acoustic grid an appropriate method. possible to relate the grid It is also geodetic is map measurements to a at a later time. which determines the position of an object relative fixed network of transponders, phase to a measurement systems are contained within the support ship except mobile transponder. Three receiving elements are located precisely with respect to each other on the underside of the support craft; they are usually attached to a mast extended over the side of the craft. A diver places a transponder on the object whose position is to be determined, and an interrogator located on the ship queries the transponder. A phase analysis by the receiver on the return signal, which as deflection angle and is is performed displayed line-of-sight range to the object with respect to the receiver element mast. The only variable is velocity of sound, which must be determined by the method discussed previously. scuba cylinder so that the position of the diver can be monitored continuously by personnel craft. When in continuous communication the support is available, the diver can be directed through a geodetically fixed survey pattern if This system the ship's position is is known brittle and break in corrode. Ordinary pencil lead can be cleaned off easily wax smears and often must be removed with a solvent. Mechanical pencils are unsatisfactory, since the metal parts will soon corrode. The best writing instrument is an off-the-shelf, readily available plastic pencil that uses bits of sharpened lead encased in plastic butts. Slates can be made multipurpose by adding compasses, rulers, or inclinometers (see Figure 9-4). Because there accurately. suited to applications where a large made under water, a list of tasks to be undertaken and the form to be used for measurements should be all developed before the dive. These lists and tables may be inscribed on the plastic pads. In some cases desirable to retain the original records (this important in is is the case of archeological drawings, for instance); drawings then are made with wax crayons on or rubber bands. There are several types of underwater paper, including a fluorescent orange paper. Standard formats can be duplicated ahead of time to facilitate recording during a dive. A simple and inexpensive technique for underwater data sheets is to prepare the sheets on regular typing paper and then have each sheet laminated in the same way that drivers' licenses disadvantage of requiring a surface-support platform. good practice Diving Manual it particularly and other important identification are preserved. Where precise measurements are to be made, — NOAA is a risk of misinterpreting the often rather erratic notes area must be surveyed or where there are only one or two sites of interest. Although the system has the October 1991 cold water, and pencil holders have metal parts that will waterproof paper attached to the plastic board by screws Small transponders are available that can be strapped to a pencils are usually not satis- become with scouring powder, but Phase Measurement. Unlike the acoustic grid method, for a single factory because they for two observers to take it is independent 9-5 Section 9 Figure 9-4 Multipurpose Slate breathing noise and increases voice fidelity by picking up sounds from the resonating chamber formed by the rather than from the high-sibilance area in front of the lips. Several commercially available masks are equipped with demand regulators that can be used mask with standard scuba cylinders or with an umbilical air When an umbilical is used, most diver-tender communications systems can be wired to accept a tape supply. recorder so that both sides of the conversation can be recorded. Regardless of the unit selected, divers should practice using the system in shallow water until they can produce To intelligible transcriptions routinely. optimize recording fidelity and minimize distortion and interference, cassette tapes of the highest quality should be used. At present, commercial tapes are Photo Robert Dill available that have 60 minutes of recording time on each side, and this capacity generally sufficient for is most scuba missions. Maintenance measurements and to check them with each other for agreement before returning to the surface. If there is disagreement, the measurements should be repeated. Tape recording is another useful, although somewhat specialized, method of documenting data under water. The most satisfactory and reliable system includes a cassette tape recorder as part of the hardwire two-way in the is 9.4 BIOLOGICAL SURVEYS same requirements and involve the same techniques as those described in a self-contained unit carried by a diver Section 9.2; however, some specific aspects should be in scuba mode. The position of the microphone and way which Biological surveys generally have the mentioned. Biological surveys are used for placing recorder. the effects of ocean in especially important O-rings, seals) to prevent corrosion. waterproofed is critical in determining the usefulness of an underwater tape the is must be taken (checking umbilical diving; the communication system used alternative for tape recorders; special care it is Some commercial systems feature a special mouth- piece unit into which a microphone which the scuba regulator is built and to many poses, including determining the environmental man-made objects on the seafloor and assessing dumping on marine most marine environments, ate the impact of pur- impact of it is resources. In not possible to evalu- man-made changes without performing attached. Standard special baseline surveys designed to obtain specific however, do not allow the lips to move form anything more than simple words or noises, which are usually intelligible only to the speaker immediately after the recording is made. This is information about the biota and the physical environ- is especially true for biologists giving long cannot be obtained before the natural undersea envi- mouthpiece is bits, sufficiently to names or for scientists reading lists of scientific numbers from instruments. ment. To be meaningful, these studies must be made before structures are emplaced on the seafloor or material discharged into the area. When baseline information ronment has been altered by human actions, biological surveys can be used to determine the incremental impacts of subsequent activities. NOTE Baseline studies must be designed so that they can The most critical factor to consider in a voicerecording system for data gathering is the ability of the diver to speak and enunciate clearly enough to be understood and transcribed accurately. be monitored at prescribed intervals. Control stations placed outside the area being studied are necessary to provide data on environmental changes occurring naturally (e.g., seasonal effects). The techniques of underwater make The best equipment configuration equipped with a microphone that the immediate 9-6 mouth is is a full-face mask, located away from area; this position diminishes biological surveying involve establishing a standardized methodology to the results of the survey quantitatively meaningful and ecologically acceptable. This is done by choosing stations at specific depth intervals along a transect line and dropping an anchor at each station to serve as NOAA Diving Manual — October 1991 Procedures for Scientific Dives the center of a circle of study. Quantitative observa- made tions are then within the circle; general bottom area; to the extent that the surfaces from the horizontal, area will sampled depart be underestimated, which cause density to be overstated. This bias becomes topography and biological features of the areas beyond will the circles are also noted. particularly important as the scale of the surface vari- The amount of bottom area covered does not need to ation approaches the scale of the distribution being be the same for every station; water clarity and the measured. Dahl (1973) describes a technique designed complexity of the biota study to quantify the estimation of irregular surfaces in the The poorer the visibility, the more restricted the amount of bottom that can be surveyed. In West Coast marine environment. Briefly, the technique consists of making some simple height, frequency, and surface will affect the size of the circle. regions and for sand stations having a limited macrobiota, m) a 10.2 foot (3.1 line is generally used to produce a length measurements and then applying a surface index formula to determine the surface area. The technique 323 square foot (30 m 2 ) area of study. In rocky areas, where the biota is more diverse, a 7.2 foot (2.2 m) line Thalassia, sand can be used to define the radius of the circle of study. reefs. In addition, using tools such as plankton nets and bottom cores, scientists can estimate the number of plants and animals, take quantitative samples of life organisms is who used it forms, and take photographs of general bottom conditions ure 9-5). At each location sampled, the authors spent 10 and of each quadrat. to Environmental factors that must be considered when surveying the establishment and growth of underwater has been applied to coral reefs, benthic algal substrata, A and rubble zones, reef crests, and patch simple method for estimating populations of sessile described by Salsman and Tolbert (1965), to 15 minutes survey and collect sand dollars (Fig- making observations, taking photographs, and sampling population density. To facilitate counting and to ensure a random sample, a counting cell was by bending an aluminum rod into a square communities include exposure to wave or swell action, type and slope of substrata, water temperature, dissolved constructed oxygen and nutrient content, and extent of grazing. Variations in the intensity and spectral composition of counting squares also can be constructed using light under water also have a significant effect on plant communities, but it is often difficult to obtain accu- measurements. The illumination rate light at or within community can be obtained with accuracy a given plant only by actual in-situ light measurements; photographic light meters are not satisfactory for this purpose. 11.8 inches (30 As tubing. cm) long on each side. Inexpensive PVC divers approached the seafloor, they released the square, allowing it to fall to the bottom. The organ- isms within this square were counted and collected for procedure was then repeated later size determination; this at least two more times same method can be used any sessile A each location sampled. The at to take a random sample of organism. Underwater spectroradiometers, which are probably the most effective means of measuring light in the sea, operated fishrake (Figure 9-6). are available. Submersible spectroradiometers have obtain information on the small-scale distribution been used in studies of photosynthesis and calcification device used for surveying epifauna It is the diver- has been used to patterns and estimates of population densities of demersal and invertebrates. The apparatus consists of a rates of corals. fishes Most underwater investigators have used transect or simple quadrat methods for the analysis of benthic communities. A reasonable description of the change in biota relative to depth and other factors can be metal tubular frame fitted with a handle, a roller of obtained by measuring the area of cover along a strip or band transect. Accurate quantitative data on standing crops can best be obtained by collecting the entire ground cover from component species a in quadrat and sorting this into the laboratory for subsequent rigid PVC tubing into which stainless steel wire "staples" are fixed, and an odometer of a plastic tracking pushed along the bottom by a diver who makes and other observations on animals that occur within the path traversed by the It is visual counts, size estimates, roller. In some underwater of animal behavior, analysis. made wheel and removable direct-drive revolution counter. it is situations involving observations necessary to remain a reasonable distance from the subject so as not to interfere with normal behavior. Emery (1968) developed an underwater telescope for such situations by housing a 9.4.1 Estimating Population Densities When estimating the biological content or density of a given region, account. An it is necessary to take surface area into irregular surface can greatly increase the October 1991 — NOAA Diving Manual PVC rifle scope in tubing with acrylic plastic ends. The underwater scope described by this author functioned satisfactorily at depths as great as 180 feet (55 m). An underwater telephoto camera lens was used during the Tektite II 9-7 Section 9 Figure 9-5 Counting Square for Determining Figure 9-6 Sand Diver-Operated Fishrake Dollar Density j* s \s /-Z J^y\^~~^SF / ss.yy~~~--~~~A\) gv < y yyyy copper * yy REVOLUTION COUNTER pipe PLASTIC ROLLER Photo Art Flechsig •MP" Courtesy U.S. Navy ably the most important practical one ability to observe the experiments to avoid interfering with animal behavior (VanDerwalker and Littlehales 1971). At the other end of the magnification continuum is an underwater magnifying system (Pratt 1976). This device, referred to as the Pratt Macrosnooper, has a magnification power of seven and permits the diver to study marine organisms too small to be comfortably observed with the naked eye. It is a three-element lens system designed specifically for use under water and tiveness, cm) plastic pipe (see Figure 9-7). are then drilled through the housing is mask in use, the Macrosnooper faceplate. It should be cleaned is its in effec- some cases, such as with underwater sampling considerably more effective than from In fish, and magnitudes of the and allows one to decide whether the sampling site is unusual or representative of a larger area. With the less common species, it may be particularly important to be able to make repeated population estimates without imposing unnatural mortality by the removal feeling for the types errors associated with the sampling to held against the and rinsed of the surface. Direct observation gives one a permit the entry of water for equalization at depth. When the improve the design or pro- to situ. small demersal Holes and the spacers and cedure in consists of three lenses with appropriate spacers inserted into a 2 inch (5 make estimates operation, to is sampling apparatus carefully, of individuals. along with other diving equipment, after each use. Soap, mineral, or fungus deposits, which by an overnight soak dry detergent, may may form on Because a diver using marker buoys, stakes, or pingers be removed in either bleach, vinegar, or laun- the lenses after prolonged can return repeatedly to the same location, changes in both environment and the biota can be followed for considerable periods. In addition, changes can be imposed use. on the environment by selective removal of species, by alteration of substrata, 9.5 BIOLOGICAL SAMPLING Although a discussion of research design and so on, and the effects of these experimental manipulations can be followed in for a sampling detail. program is outside the scope of this volume, careful attention should be given to the implementation of sampling methods. Chapters on the design of sampling programs can be found in Holmes and Mclntyre (1971). As Fager and his colleagues have noted (Fager 1966), et al 9.5.1 Plankton Sampling Planktonic organisms that live within 3.2 feet (1 m) of the bottom can be sampled with a skid-mounted multilevel net apparatus that is pushed by a diver over a predetermined distance. Hand-operated butterfly valves are used to isolate the collection bottles located 9-8 Underwater operations have several advan- in the tages over sampling from the surface for ecological studies involving quantitative Plankton sampling nets 11.8 inches (30 cm) in diameter, with a mesh size of 0.08-0.12 inch (2-3 mm) sampling or observations of behavior. Prob- are used to collect plankton selectively in reef areas. cod end of the net. NOAA Diving Manual — October 1991 Procedures for Scientific Dives Figure 9-8 Figure 9-7 Hensen Egg Nets Mounted on Underwater Magnification System a Single Diver Propulsion Vehicle A. Optical B. System Complete System Photo William carried out properly, there net is reused, it is no sample loss. L High Before a should be turned inside out and back- flushed. Benthic Organism Sampling 9.5.2 Quantitative sampling of the epifauna can be accom- plished by counting the animals within a randomly located circle or square quadrat. Photo Harold Wes Pratt of brass, Air-filled bottles also can be inverted appropriate in with grooves at 0.4 inch The areas to suck up plankton and water samples. A circle template, movable arm may be constructed with the center rod and movable arm marked fixed center rod, and (1 cm) intervals (Figure 9-9). position of an animal within the circle can be Several methods of sampling plankton have been defined by three numbers: the distance along the center developed. Ennis (1972) has employed a method using rod from a standard end; the distance from the center two diver propulsion vehicles on which a 19.7 inch (50 cm) plankton net was mounted. A similar method was used during a saturated dive in the Hydrolab habitat at Grand Bahama Island, when two 3.2 foot (1 m) long Hensen egg nets were mounted on a single diver propulsion vehicle that was operated at a speed of about 2 to 3 knots (1 to 1.5 m/s) (Figure 9-8). At the end of every run, each net should be washed separately and the sample should be concentrated into the cod end by holding the net up inside a trapped bubble of air under a plastic hemisphere having an 18 inch (45.8 cm) radius. The cod end should then be removed, and the rod along the movable arm; and the half of the circle contents of the net should be poured into a glass jar. The volume at wrap should be placed over the top of the jar to trap a small bubble air. The and carried jar is to a then removed from the hemisphere work area at the base of the habitat. The work area should be deeper than that hydrostatic pressure will help to from escaping. A the hemisphere so keep the syringe filled with formalin pushed through the plastic wrap, the jar immediately secured, and labeled. October 1991 air — NOAA When this Diving Manual is bubble is then capped, procedure is To study details species, the "distance of the nearest neighbor" tech- nique can be used. This method involves preassembling a large, lightweight it metal or PVC at the appropriate location. square and dropping Within the square, divers place short brass or plastic rods with fabric flags on them at predetermined positions in relation to the individuals of the species being examined. After the positions of all individuals have been marked, distances to nearest neighbors are measured, and reflexives are counted. Samples of the substrate and infauna can be collected jar should be filled, except for a small the top, with filtered seawater, and plastic of within which the animal was observed. of the distribution pattern of individuals of sedentary with no loss of sediment or organisms by using a simple coring device with a widemouth sample container The corer jar) attached to the top (Figure 9-10). pushed a given distance, e.g., 2 inches (5 (a is cm), into the aluminum plate is slipped through the sand. The apparatus is inverted sediment is allowed to settle into the jar. Once sand, tipped slightly, and an under it and the all sediment and organisms are inside the attachment is removed and the jar is jar, the coring capped. 9-9 Section 9 Figure 9-10 Coring Device With Widemouth Container Figure 9-9 A Template Determining Benthic Population Density Circle for Photo Art Flechsig Another simple soft-bottom sampling device, esand meiofauna, is a pecially good for small infauna thin-walled coring tube of transparent plastic, the diameter of which is based on a predetermined sample designed to gather the desired substrate and organisms most efficiently. Most organisms obtained by this type of device will be found in the top 3.9 to 4.7 inches (10 to 12 cm) of the sample. For ease of handling, the tube should be at least 11.8 inches (30 cm) long and sealed with rubber corks, one of which has a small hole drilled through it. With both corks off, the tube should be rotated carefully into the sand to the desired depth, and the cork with the small hole should then be used to cap the tube. While gripping the tube for removal, the scientist's thumb should be held over the hole to create a suction that keeps the sediment from falling out. When the tube is free of the sediment, the bottom cork should be inserted. Samples accurate to any depth can be taken with this device, and depth lines can be marked on the outside of the tube. To remove the core, the scientist places a finger over the hole in the top cork, removes the bottom cork, and allows the plug To remove to fall out. discrete segments of the core, the plug may Photo Art Flechsig Another coring device samples of the infauna is for obtaining quantitative a square stainless steel box with handles and a screen covering one end (Figure 9-11). Its rugged construction allows scientists forcibly to penetrate hard substrates, such as sand or vegetated bottoms, as well as softer sediments. The sampler, currently in use by NOAA/NMFS divers, can m 2 sample to a depth of obtain a 0.17 square foot (1/64 ) be pushed out the end and cut into desired lengths or 9.1 quick-frozen in dry ice immediately upon surfacing substrate to the desired depth, one side of the device (to prevent migration of animals) and later cut with a hacksaw. A is used for studying the depth distribution of infauna. This corer samples an area of 1 (6 cm). inches square (45 The corer cm 2 ) to a depth of 2.4 inches consists of a square brass box fitted with a funnel adapter at the top to accept widemouth sample containers. The front side of the corer is slotted to permit thin metal slide plates to be inserted to separate the sample into five separate layers, which can then be transferred under water to separate sample containers. 9-10 excavated and the device is is pushed into the is which the To prevent any loss of tilted over, after corer and sample are pulled free. multilevel corer about inches (23 cm). After the corer sample, the diver holds the open end of the corer against body while ascending. The contents are then appropriate mesh size (Figure 9-11), washed free of most of the sediments, and the residue containing the organisms is placed in jars of preservative. A red dye (usually Rose Bengal) is added to the preservative to facilitate the sorting and identihis or her placed in a sieve of fication process. A Multiple Disc Sampling Apparatus for collecting epibenthic organisms has been developed by NOAA Diving Manual NOAA/ —October 1991 Procedures for Scientific Dives Figure 9-11 Infauna Sampling 701 Box 1.2 mm 2 cm Diameter Stainless Steel Mesh Screen 0701 mm 2 Mesh Screen 1.6 mm Stainless Steel Plug Sampler Source: NMFS divers. 9.7 inches (24.6 Each cm) collecting unit consists of a disk in 0.54 square feet (1/20 have been used in can bore into it or merely attach to diameter with a surface area of composition m2 over long periods. In soft bottoms, ). Various kinds of material the construction of the disks (wood, glass, steel, rubber, cement). Rubber and cement will also determine it, NOAA (1979) and the rock's resistance to erosion its it is useful to describe sediment grain size and bottom configurations; deter- minations of grain size, chemical composition, and generally are superior substrates for most sessile invertebrates. The disks are wired to a galvanized pipe especially equipped to handle these tasks. Situations frame placed on the bottom by divers. Individual disks vary, removed at intervals by divers who place a canvas collecting bag over the disk and cut the wire holding the disk to the frame. This procedure minimizes the geological data. are the disks are filled with a narcotic solution (7.5% chloride mixed 1:1 with seawater) for hour and the disks are then preserved in a 1 10 percent formalin solution. Wiring disks rather than bolting them simplifies the operation of corroded fastenings. and eliminates the problem The experimental design — col- lecting frequency, substrate material to be tested, or other epifaunal survey requirements number and it may be helpful to consult geologists for recommendations on where to obtain the appropriate organisms. Individual bags containing loss of motile magnesium other physical characteristics are best done by scientists — dictates the of disks to be used. Because of the large size of disks, the epifaunal assemblages that are collected by 9.5.3 Airlift An Sampling airlift is plastic pipe a sampling device that consists of a long equipped with a device The to supply air at the and organisms and water, so that they can then be emptied into a mesh bag of a certain size (see Section 8.9.1). Large areas of soft bottom can be collected in a very short time with this device, and the samples can be screened through the lower end. airlift carries sediment to the top of the pipe in a bag in the process. When stream of air used with a diver-held scraping method are more typical of those found on natural substrates. However, only a portion of each disk is examined and enumerated. Some knowledge of geological techniques is helpful when sampling. For example, on rocky substrates it is important to know how to measure angles of inclines on device, an airlift overhangs or shelves, because Although plastic bags have been used successfully to sample swarming copepods and small aspirators have been used to sample the protozoan Noctiluca, animals in midwater must generally be collected using this this many organisms orientation of angle influences the (see Section 9.10.1). Similarly, knowing the composition of the rock important in is determining whether or not organisms October 1991 — NOAA Diving Manual is also useful on hard substrates, especially to collect the small organisms that tend to escape when attempts are 9.5.4 made to "scrape and grab." Midwater Sampling 9-11 Section 9 Figure 9-12 Use of a Hand-Held Container to Collect Zooplankton other techniques. It is difficult to sample even very ftp' * • ~WM small animals, such as the copepod Oithona, without swim rapidly and readily dodge water bottles, short distances disturbing them. Although small, copepods for nets, or aspirators. If nets must be used, they are deployed most effectively by divers swimming the nets by hand or guiding diver-propulsion units to which the nets are attached (see Figure 9-8). the mouth of No ^^y objects should obstruct the net, because even monofilament bridles cause zooplankton to avoid nets. The diver can easily capture larger, less motile zooplankton that range from several millimeters to a few centimeters in size, such as the gelatinous medusae, ctenophores, salps, pteropods, and chaetognaths, by permitting the animals to swim etc., into a hand-held container, preferably of clear plastic or glass (see Fig- ure 9-12). This is it is the method of data the preferred for all aspects of laboratory collection y^w marine research, because way to collect these delicate animals without damage that normally occurs even with the most the carefully handled net. Estimating density of planktonic aggregations. For many kinds of organisms, density and distribution can B^afl be determined photographically without disturbing the The use aggregation. of an 80-mm lens and extension tubes provides a small measured field of view some 11.8 to 15.7 inches (30 to Depth of 40 cm) from the camera. field varies systematically with f-stop (see Photo Al Giddings Section 8.13). Instructions for some underwater cameras provide these calculations, but investigators can make own cameras by photographing underwater targets at a series of known distances in front of the camera with different f-stops and determining the them for their depth of field in the resulting photographs. Density of organisms such as copepods within swarms by counting i.e., all within a is determined of the animals in focus in the photograph, known volume determined by area of field field. When the number of organisms in times depth of focus is large, density can be estimated by measuring the distance from one individual to its closest in-focus neighbor for each of some 20 individuals within a single plane. These distances are averaged and the density of the aggregation is estimated by entering this average into the formula for close packing of spheres or of isohedronic arrays. Use of the formula 1,000,000 cm 3 /0.589 x (average nearest neighbor's distance in Number cm) 3 Density measurements for animals sparsely distributed can be obtained more easily by swimming Figure 9-13). Divers also 9-12 all drift slowly on a tether drift rate and counting the number of organisms that pass through a grid in a specified time. Replicated measurements permit the application of most normal ecology. many statistical Some statistics procedures used in quantitative tests are of questionable validity because depend on presupposed patterns of normal distributions, patterns that may dimensional arrays. Nonetheless, not apply to three- many of the sampling procedures used by the terrestrial ecologist may be applied to underwater sampling. Biological oceanographers now use these new techniques frequently. = of organisms per meter 3 preferred because isohedrons pack symmetrically along may with the ship and estimate densities by measuring the 9.6 is line transects between tethered buoys while counting the number of animals that pass through a grid of selected size (see three axes, whereas spheres do not. SHELLFISH STUDIES The use of diving as a research tool to study lobsters, crabs, scallops, and other types of NOAA shellfish has increased Diving Manual — October 1991 Procedures for Scientific Dives Figure 9-13 Use of a Plexiglas Reference Frame for Estimating Population Densities in Midwater ment. In addition, lobsters than one-half pound less (0.22 kg) in size generally are not nocturnally active in environment but are active their natural at night in the confines of an aquarium tank. Lobsters spend most of their first 3 years of life in a labyrinth of tunnels projecting as many as 3 feet (0.9 m) into the boulder- rock substrate of the ocean bottom (see Figure 9-14). Replicating this substrate 9.6.1 in an aquarium is difficult. Collecting Techniques Many shellfish (crabs, lobsters, and clams) inhabit tunnels and burrows on the bottom. Others (scallops, and abalone) live in beds and reefs or creep and rocks. When collecting shellfish, divers should always wear gloves and carry catch bags. oysters, across the seafloor Lobsters inhabit burrows, tunnels, and caves in shallow and in ocean depths that are beyond the range of surface-supplied diving. Those more than one-half pound in size are nocturnal in their movements; during daylight hours, they remain in their homes. coastal waters When picked up, spiny lobsters and bulldozer lobsters if grabbed around the abdomen (tail), the tail can cut a diver's fingers. The American lobster can be collected easily by grabbing should be held by the back; it from the back, behind the claws. Lobsters can also be grabbed by their ripper claws and held Courtesy ^National Geographic Society Photo Al Giddings seconds; for l to 2 held longer, their crusher claws will be if brought into action. Lobster claws should be inactivated by banding or pegging before the animal is put in a catch bag; this will prevent animals from crushing commercial importance of these and the difficulty of sampling these as a result of both the living resources organisms effectively with conventional surface-oriented equipment. In general, shellfish studies have been directed toward the ecology of these organisms, their behavior in relation to sampling gear, the efficiency of sampling gear, and the potential effects of conventional sampling techniques on the bottom environment and its fauna. Historically, more underwater studies have been New conducted on the American lobster of the England coast than on any other single species of shellfish. In addition, extensive studies have been done in Florida and California on the spiny lobster (Herrnkind and Engle 1977, Marx and Herrnkind 1985). Direct in-situ observation of lobsters is the most each other. Lobsters frequently will autotomize (drop) antennae and claws when handled; American lobsters this especially during the winter months, when water temperatures range between 28.5° and 34.0° do (-1.94° and 1.1°C). The conventional method for commercial harvesting and New England clawed lobster is the wire or wooden trap. Divers should assess the efficiency and design of this gear before using it, bearing in mind that spiny lobsters move much faster than American lobsters and are much more sensitive to of the spiny being disturbed. Commercial crabs are found in waters ranging from shallow estuaries to ocean depths that are beyond conventional diving limits. Gloved divers can catch them easily by hand with short-handled scoop nets and when way to study lobster ecology and behavior. Comparative studies of lobsters in the laboratory- tongs. Caution should always be exercised aquarium environment have shown that claws; depending on the size and species, such injuries effective is altered significantly when they example, lobsters held balistic, in but cannibalism October 1991 — NOAA is their behavior are in captivity. For collecting crabs because they can pinch with their can vary from a cut finger (blue crab or Dungeness captivity are highly canni- crab) to a broken finger (stone crab or Alaskan King rare in the natural environ- crab). Diving Manual 9-13 Section 9 Figure 9-14 Benthic Environment of the American Lobster coast states, and in the North Pacific. They occur and pilings, and together, in large beds of thousands of individuals. These sedentary shellfish are easy to collect by hand. A individually, in clusters attached to rocks Surface pry bar can be used to collect samples that are attached. Oysters can temporarily be piled loosely on the bottom during harvesting. Scallops live in bays, sounds, and ocean bottoms in depths up to 328 feet (100 m). Density varies from one or two individual scallops to dozens per square meter. They are collected easily by piles of scallops Distance from Shore (Meters) 100 the scallops 200 150 should not be hand or scoop left may swim away. Loose net. on the bottom because Getting one's fingers stuck in the shell of a live scallop is painful. National Marine Fisheries Service Abalone inhabit rocky coasts from Alaska to southern They are nocturnal foragers of algae and California. Blue crabs estuaries, bays, and sounds Atlantic Ocean. When fast in frightened, they will burrow quickly into the bottom or These temperate waters of the Gulf of Mexico and live in the shallow, swim away with great speed. rest during the day at their "homespots" on a rock. iron pry bar can be used to pull them An and they loose, can sometimes be pried loose quite easily with a quick motion. swimming, pugnacious crabs can be collected They can be found partially buried and lying around shells and 9.7 rocks or walking along the bottom. Tagging aquatic organisms can provide information on easily with a short-handled scoop net. Stone crabs inhabit burrows, depressions, and shell houses in the coastal waters along the South Atlantic and Gulf of Mexico tongs is useful to An cm) pair of extricate them from burrows and states. 18 inch (45.7 TAGGING AND MARKING TECHNIQUES many tion, aspects of underwater including coastal migra- life, nearshore to offshore movement, seasonal bution, and growth rate. Because tagging can distri- damage the animal, the value of the information gained from a shell houses. Their claws can be brought into action quickly and can easily crush fingers, so they should be return should be carefully considered. handled carefully. Stone crabs should be handled by organisms: their rear legs. be captured and brought to the surface for tagging. The Alaskan King crab lives in the cold waters of the North Pacific Ocean and the Bering and Okhotsk Seas. Young crabs (2 to 3 years old) inhabit shallow waters collect fish for tagging. in large "pods" of 2000 to 3000 individuals and migrate to deeper water as they mature. Mature crabs (males range up to 6.6 feet (2 m) and 22 pounds (10 kg)) migrate seasonally between deep and shallow water to spawn. As the crabs walk across the bottom, divers can collect them by grabbing them cautiously from behind. Dungeness crabs are found in shallow inshore, and offshore waters from southern California to Alaska and the Aleutian Islands; they live in waters that are up to 328 feet (100 m) deep. These large crabs, which range up to 9.4 inches (24 cm) across the back estuarine, and up to 2.2 pounds (1 kg) in weight, can move quickly, occasionally even faster than a diver can swim. Individual crabs can be captured from behind and placed in a mesh bag, if this is done cautiously. Oysters inhabit relatively shallow waters bays, 9-14 and sounds in the There are two different methods of tagging marine The animal can either be tagged in situ or Figure 9-15 shows an electroshocking grid used to Although more traumatic for the organism, the latter method has the advantage of allowing the animal to be weighed, measured, and examined in detail before release. ble to take measurements in situ Methods are under water. Although body dimensions can be measured under water, a method for determining body mass (weight) has not been developed. Ebert (1964) described a fish-tagging gun that satisfactory inserted a standard dart tag into bottom-dwelling fishes and which could be adjusted scale thickness. More to account for skin or recently, the plastic Gulf of Mexico, off the Atlantic "T" tag, marking clothing (Figure 9-16), has been used. The needle of the tagging gun is placed against the organism and the tag is inserted into the body tissue. With practice, the depth of tag penetration originally designed for can be controlled by the tagger. Because in estuaries, availa- gun has many metal parts, it this particular must be washed and oiled carefully to avoid corrosion. NOAA Diving Manual —October 1991 Procedures for Scientific Dives Figure 9-16 Tagging a Spiny Lobster on the Surface Figure 9-15 Diver With Electroshock Grid Courtesy Floy Tag and Manufacturing Inc Courtesy Diving Systems International Photo Steven M. Barsky carapace, adjusted, and then crimped with a leader sleeve. Other methods of short-term tagging include staining by injection or dipping with vital stains, fluo- Lobsters have been tagged within their natural envi- Tagging of oysters, scallops, and abalone can be accomplished by attaching Petersen tags with glue or a be marked with styrofoam floats, numbered wire, painting the shell, using colored quick-setting term (retained dens may rescent dyes, or phosphorescent dyes. shedding) tags and marks. Lobster ronments with short-term at (lost at shedding) and long- The carefully to note specific locations. Color-coded tags cement, or staining the shell with may be inserted into the dorsal musculature between excurrent holes on abalone shells are very convenient abdomen and thorax of the lobster with the aid of a No. 20 syringe needle (Figure 9-17). A secondary mark abalone has been reported by Tutschulte (1968). This or 4 mm) technique involves attaching a small battery-powered mark will the may be made by punching a small hole (0. 1 6 in. into one of the five tail fan sections; this be retained through at least one molt and will permit recognition of a lobster that has lost Movements and its primary locations of lobsters at night tag. may be determined by using small sonic tags (pingers). These tags are small (about 1.2 x 2.0 x 0.4 in. or 3 x 5 x 1 cm) and weigh only a few grams. Several types are available commercially. They operate in the general frequency range of 70 kHz and may be picked up as far away as m) on an open bottom and 60 1200 feet when the tagged lobster When kept in (363 is mind movements shell are its to the shell. for tagging During the night, the of the abalone with the light source on recorded on sensitive film by a camera Movement fixed several meters above the seafloor. of a marked animal may be recorded either as light streaks (in time exposures taken with a or as a moving point of still light (in time-lapse tography). Animals studied by this to a constant, low-intensity light method are subjected and are not illumi- havioral changes caused by unnatural light flashes and the affect overall behavior. In one in night diving; be- are therefore probably eliminated with this method. A technique has been developed for tagging echino- study, a significant alteration of the population dis- derms (Lees 1968). This method involves was noted during the course of several weeks of capturing and tagging (Miller et al. 1971). Long-term and short-term tags also have been used by divers in crab population studies. Long-term dart and spaghetti tags can be inserted at the isthmus of the carapace and abdomen, the point from which the crab tiny hole completely through the sea urchin tribution exits when shedding. Short-term to the legs or carapace. tags can be applied Carapace tags for blue crabs consist of an information-bearing plastic spaghetti is stainless steel line) that has carefully in a holding device its The urchin first is hole or crevice and placed made from diver to press the urchin still (11.4 Diving Manual removed from a weighted plastic bowl lined with thick polyurethane foam; this enables the drill — NOAA been strung with small pieces of color-coded vinyl tubing. A October 1991 drilling. a and inserting an inert filament (monofilament line or high-quality put around each of the lateral spines of the tag with a loop of stainless leader wire at each end. loop camera) cinema- should be required for direct observation it method nated by the periodic flashes of high-intensity light that the very presence of the diver may luminous beacon A m) feet (18.4 in a crevice. conducting a survey of lobsters, tagging procedures points of attachment for tags. vital stains. down into the during the drilling operation. An fitted with an 18-gauge, 4 cm) hypodermic needle is used to foam to hold it ordinary hand 1 /2-inch-long drill completely 9-15 Section 9 Figure 9-17 Tagging a Spiny Lobster in Situ (Randall 1961). Spaghetti tags are made of soft tubu- about 1/16 inch (0.16 cm) in diameter, with monofilament nylon in the center. This type of tag lar vinyl plastic can be attached by running the line through the fish's back beneath the rear of the dorsal fin. Because this type of tag can snag on rocks or coral, the method is not recommended for reef fishes. Dart tags consist of a vinyl plastic tube with a nylon tip and barb. They can be inserted into the back of the fish with a hollow needle so that the plastic streamer bearing the legend trails posteriorly, this come tend to Source: NOAA (1979) with a slight upward tilt. Although technique permits fairly rapid tagging, these tags via the first loose more easily than those implanted two methods. Another method of tagging finfish involves injecting colored dyes subcutaneously (Thresher and Gronell through the test and body cavity. After the filament or wire has been threaded through the needle, the entire drill/needle assembly slowly withdrawn, pulling the is 1978). This technique has been used successfully in studying the behavior of reef fish. The dye can be injected via disposable plastic syringes and dispossitu for wire through the body cavity and leaving wire and tags able needles. Although several different dyes have been on the urchin. The ends of the wire are then used, plastic-based acrylic paints are the most satis- in place twisted together to form a loop, and the loose ends are factory and apparently do not trimmed. cantly affect their behavior. The same technique can be used to tag sea cucum- can be pushed through by bers, except that the wire hand instead of with a drill. Animals tagged in this fashion seem to be unaffected, and tags have been known to last for 6 to 8 months. With sea cucumbers, trimming the tags short important because fish is may otherwise nibble on the long loose ends. Tagging The finfish requires special skill size of the fish will not must be and handling. sufficient so that the tag impair the ability of the fish to navigate, forage, or avoid predators. Lake (1983) lists several guidelines for tagging finfish: • use barbless hooks to catch the fish • avoid the use of bait • don't tag fish that have been tired by a long fight • hold fish with a wet rag over their heads keep • don't tag fish that are bleeding from the gills • tag during cold water season whenever possible • during tagging, gills free the water for of sand and dirt make sure that fish are not out of more than 60 seconds. For small-scaled and scaleless species, the needle from the number of techniques have been used to tag finfish. Three common methods involve Petersen disk tags, spaghetti tags, and dart tags. Disk tags are about 3/8 or 1/2 inch (0.95 to 1.27 cm) in diameter and come in a variety of colors. They can be attached to the back of is body surface, so that the tip enters the skin, runs underneath it for a short distance, and then emerges. This in-and-out technique ensures that the tag is placed immediately below the skin, the best position for producing a longlasting tag. Slight pressure should be placed on the syringe to start the flow of dye (and ensure that the needle is not plugged), and then the needle should be pulled back under the skin and withdrawn. The smooth motion results in an even line of color below the skin. inserted rear, parallel to the For large-scaled species, the needle should be inserted under the rear edge of a scale and moved gently from is applied to the syringe, which causes a small pocket of dye to be deposited under the scale. Acrylic paint tags inserted in this manner have lasted as long as 16 months; durability depends in part on the color of the paint. Scallops have been marked successfully using a quickcement (Hudson 1972). This setting calcium carbonate material meets four criteria: A the fish or signifi- used, depending on the size of the species to be tagged. side to side while pressure • harm Two methods have been tissue; 2) it is 1) it does not harm living easy to apply and readily visible; 3) it adheres to a wet surface and hardens under water; and 4) it makes a durable mark. The recommended mixture for this purpose is: not be used on fish that will seven parts Portland gray (or white) cement (Portland Type II is best because it is formulated the tag will especially for use in seawater) the fish with monofilament 9-16 line. This type of tag should grow to a large size because cause pressure on the fish as it grows • NOAA Diving Manual — October 1991 Procedures for Scientific Dives Figure 9-18 Elkhorn Coral Implanted on Rocky Outcrop • one part moulding paste • two parts builder's sand (fine grain). This mixture will start to harden in 3 to 5 minutes (or moulding paste is used). The materials should be thoroughly mixed while dry, and three parts of water should be added to 10 parts of dry mix. If colored cement is desired, no more than 10 percent additive by volume should be used, so that the strength sooner if of the cement less is not reduced. The final consistency should be similar to that of a firm putty. To apply cement to a scallop, the organism should be removed from the water and the upper valve should be pressed into a soft sponge to remove excess water. A small quantity of cement (about 1/2 cc for scallops 0.4 to 0.8 inch (10 to 20 mm) in shell height and 1 cc for scallops 1.2 inch (3 lip cm) or larger) is placed near the and then rubbed firmly across the shell at right angles to the ribs. This tightly grouts the depression between the over the "A* and leaves a thin coating of cement Several quick shell. to distribute shell ribs thumb cement evenly out to the lip so that J. Harold Hudson new growth can be measured accurately. Only enough cement should be applied Photo strokes are necessary relatively deep habitats. The sites where most research the inter-rib areas; involving algal and angiosperm vegetation takes place the upper surface of the ribs should be visible through are shallow enough to be accessible with scuba equip- the coating. Marked to fill scallops can be returned ately to the holding tank, immedi- where they should be held for several hours to allow further hardening. Scallops marked in this way have retained this marking material months or more. The same type of cement has been used to transplant live coral in reef areas and to mark large marine gastropods and other delicate bivalve molluscs (Hudson for 15 1978). Figure 9-18 shows a living elkhorn coral, Acropora palmata, implanted on a rocky outcrop. Another method marking marine organisms involves the use of various dyes. Alizarian Red dye has increasingly been found useful for making permanent growth line marks in living corals and other invertebrates. The dye does not harm the coral, and subsequent growth can be for measured after the coral sliced with a saw. is ment. Wherever stable substrates occur nearshore, on rocky beaches, in estuaries or bays, or on coral reefs, various forms of plants will develop. As with all underwater work, however, site-specific features limit and strongly influence the choice of sampling method. Large-scale biologic studies may include samples or catalogues of plants, recorded with estimates of area covered. may sometimes Data be combined for forms or species (crusts, Iridaea spp., for example), depending on the need for taxonomic precision. Large discrete thalli, such as taxa of brown kelp, usually are counted. In some cases only indicator taxa, selected on the basis of economic value, dominance, or ease of identification or counting, are of interest. Sampling programs that are designed natural environments focus on both nearshore intertidal abundance and distribution patterns of plants sessile organisms are described in Sections 9.5.1 and 9.5.2. Presence/absence data or estimates of abundance are utilized for experimental studies as well as for descriptive investigations. The methods employed for these various objectives rely on sampling procedures the region where sufficient that have largely been adapted from terrestrial or can penetrate the water to support the growth of (Figure 9-19). Benthic algae can occur at depths greater intertidal studies. Their applicability to subtidal work depends on their efficiency under conditions where time, mobility, and visibility are often severely limited. These factors must be assessed independently for every than 656 feet (200 m), but few species occur situation. to record and other 9.8 BOTANICAL SAMPLING Studies of benthic macroalgae and seagrasses in their zones and depths. This light is diverse and often dense associations of photosynthetic organisms that grow attached October 1991 — NOAA to bottom substrates Diving Manual in these 9-17 Section 9 Figure 9-19 Algal Cover of Rock Substrate material into component species in the laboratory. These specimens can then be dried, weighed, and reduced to ash for analysis of organic content. For ecological studies or census (.data, the size and of quadrats to be used must be determined by number appropriate tests, such as species accumulation curves, and researchers often find it advisable somewhat larger than the minimal one to use to an area be confident of establishing statistically significant differences between samples. Seasonal variations in the diversity and abundance of plants world. and To is very conspicuous in certain parts of the get complete coverage of events in an area to gain understanding of the natural cycles, it is necessary to sample repeatedly throughout the year. It is same best to return to the station to monitor changes over time. Photo 9.8.1 Field Bunton Procedures As with any ecological project, the objectives and constraints of the study sites Bill and the features of underwater determine which techniques are appropriate. In Some plants have a narrow temperature tolerance, and these may act as indicator species because their presence or absence suggests certain environmental characteristics. North latitude kelp taxa, for example, do not live in warm water and are not found in tropical latitudes except where cold currents or deep cold water provide suitable circumstances. recent years, subtidal biological methods have been summarized in books that draw on hundreds of scientific and technical publications. These sources provide up-to- 9.8.2 Collecting Techniques date reviews of methods, as well as discussions of their Before beginning a study that requires the collection advantages and disadvantages. Accordingly, of plants, an investigator should survey local environ- the following paragraphs represent only a brief review mental conditions so that he or she will know where and how to sample. Most macroalgae require a hard substrate for attachment, and the diversity of plants on relative of botanical field procedures. Generally, underwater botanical sampling, whether of data or specimens, depends on the use of transect lines, grids, haphazard ("random" is rock surfaces usually far greater than in soft sediment is in fixed, systematic, or or sandy areas. Pilings, shells, dead corals, barnacles, rarely practical) positions. shipwrecks, and mangrove roots are other places algae and quadrats arranged Recently, circular sampling designs have been found are likely to attach. Marine vascular plants (seagrasses) useful in sites of heavy surge, rough water, or low follow the reverse pattern; most species visibility. grow on soft or In circular sampling, a radius-length line sandy substrates, although some, such as Phyllospadix, used to partition the grow on the rocky shores of the western United States. Frequently, seagrasses and larger algae themselves attached to a central fixture is area and guide the diver. Underwater sites are usually located on the surface by sighting or buoys and on the provide substrates for a great array of smaller epiphytic bottom by a variety of fixed markers. Data can be recorded by notations on data sheets treated for underwater use, by collections of organisms, photography, voice recorder, or television camera (see plants. Because benthic plants are attached to the substrate, a tool such as a putty knife, scraper, or knife is usually appropriate for investigating marine plants. Studies remove entire plants if these are required for voucher specimens or for later study. Mesh bags or small plastic vials with attached lids are useful for holding samples. If plant samples are necessary for methods seek, identification, portions or selected branches are often Section 9.3). Methods suitable for sessile animals are particularly that rely on these ferentiate and classify plant in general, to dif- communities and to analyze needed to adequate. If there is no reason for collecting material, of productivity, a non-destructive sampling or experimental design standing crop data can be obtained by collecting the can be implemented. If small thalli are needed for laboratory examination, it is often more efficient to the data to identify changes. entire vegetation 9-18 As an index from a given area and sorting the NOAA Diving Manual —October 1991 Procedures for Scientific Dives Figure 9-20 Diver in Giant Brown Kelp (Macrocystis) Bed collect pieces of rock or substrates than to remove and handle plants during the dive. When several divers are involved in a study, a system "unknowns" (specimens for incorporating be identified that cannot the field) should be included in the in planning stage. Vouchers for such data as well as for all critical taxa should be assembled and retained with the raw data. If an investigator wishes to obtain a census of an area, collections from diverse substrates should be sampled. Because some plants only in intertidal live or shallow water, while others live only in deep water, made over a broad depth range. such as the kelp Macrocystis (Figure 9-20), that may be 100 feet (30 m) in length, with holdfasts 3 feet (0.9 m) in diameter and as many collections should be Data as for large plants, 400 or 500 based on in-situ stipes, are usually observations and measurements. Care should be exercised when placing several types of marine plants in a common container, because plants that have extremely high acidic content in may damage other forms of algae the container. A clipboard with waterproof paper and pencil for notes and a field notebook should be used to record data immediately after diving. Diving observations should be recorded as soon as possible. Ideally, field data should include notes on depth, substrate, terrain, water temperature, current, visibility (clarity), con- Source: NOAA (1979) spicuous sessile animals, herbivores, the date, time, methods used, and the collecting party. If possible, information on available light, salinity, and other environmental factors should be obtained. Census data become more species is useful i.e., abundance of each whether common, Many marine species are incon- if the relative at least estimated, occasional, or rare. spicuous, and these require careful microscopic exami- increased surface area, which augments the current output per unit of illumination; a system for easily filters; and a sensitive ammeter whose range can be altered by current attenuation changing the colored circuitry. nation and identification in follow-up work. measurements within a given plant community can be obtained by using small, selfcontained light meters. The use of photographic light 9.8.3 meters that incorporate selenium photocells be Accurate light is unsatis- factory unless restricted spectral regions, isolated with colored are measured. This filters, system that responds differently is Specimen Preparation and Preservation To determine the kinds of plants present, notes should made on the collected specimens while they are still fresh. Herbarium and voucher specimens can be made because a sensing from either fresh or preserved material. Plants prepared wavelengths soon after collection tend to retain their natural color to different being used to measure light that is becoming monochromatic with depth. The introduction of colored filters in front of the meter greatly is better than those that have been preserved, because increasingly more than formalin does. Although procedures for drying and mounting large algal and seagrass specimens are described in many easily obtained and standard guides, a few simple procedures are described here. Most marine algae have a gluelike substance on the outside of the cells that makes specimens more or less self-adherent to most kinds of paper. Standard herbarium paper will preserve a reduces added its to sensitivity. make An opal cosine collector can be the system behave more like the plant's terms of light absorption, but such collectors can only be used in shallow, brightly lit waters. The apparatus needed to make such measuresurface does in ments generally incorporates October 1991 — NOAA a selenium photocell of Diving Manual alcohol bleaches thalli 9-19 Section 9 collection permanently, but this paper requisite for making a useful Formalin (2.5-5%) set of will preserve is not a pre- voucher specimens. small or delicate forms, Samples obtained from many stations can be kept separate bags in a single large storage off, or collector should be associated with every specimen condition for several weeks by label, with a numbered reference to a field book or in that can be sealed tightly to prevent formalin from leaking out. and permanent slides are useful for ongoing work. Time and place of collection and the name of the study data drum For shipping, most of the preservative can be drained because the plants, once preserved, remain An in good they are kept damp. if method for preserving whole large them for several hours or days alternative plants involves soaking set. There are standard herbarium methods for pressing some special variations for marine algae. The usual approach is to float specimens in large, flat plants and and to slide them carefully onto sheets of heavyweight herbarium paper. Using water, the plants are arranged on the paper; the paper is placed on a sheet of blotting paper and topped with a square of muslin or other plain cloth or a piece of waxed paper. This is covered with another blotter, and a corrugated cardboard "ventilator" is placed on top. Another layer of paper plant cloth blotter cardboard is blotter stacked on top. When 20 or 30 layers have been stacked, the pile should be compressed, using a weight or the pressure from heavy rocks or from straps wrapped around the plant press. The top and bottom pieces trays — — — — — in a solution consisting of 10 percent carbolic acid and 30 percent each of water, alcohol, and glycerin. Spec- may be imens thus preserved dried and then rolled up The glycerin helps to keep the plants flexi- ble indefinitely. Another technique involves partially newspaper (in the shade) and for storage. air-drying giant kelp on beginning with the holdfast. Rolls rolling the plants, wrapped in paper, and left to finish drying. Specimens so prepared can later be resoaked are tied, labeled, for examination. one wet preserved specimen should be If possible, kept for each pressed specimen. This is especially impor- tant for unidentified species, because taxonomic classification often depends on cell structure. Some small plants can be preserved with general collections, but boards slightly larger than the herbarium delicate specimens should be isolated. Retaining small paper and blotters are generally used. After several pieces of rock with encrusting algae attached helps hours (or overnight), the stack should be taken apart, keep the plants intact. Coralline algae and rock- should be stiff; and the damp blotters should be replaced with dry ones. Many small algae dry in one day using this technique, but some, such as the large brown algae, may take a full week to dry completely, depending on air humidity. The usual method for preserving specimens for later detailed examination and herbarium preparation is encrusting species require special attention. Articu- may be pressed on paper and then brushed with a diluted solution of white glue as an alternative to older methods of storing in boxes. Plants collected for particular purposes (electron lated corallines microscopic study, chemical analyses, culture inocula) require special treatment. It is important to fix or simple and effective. For each station, one or more preserve such specimens as soon as they are removed large plastic bags can be used to hold samples of larger from seawater. Because algae are photosynthetic organ- plants. Small bags or should be used for selected vials isms and the deleterious effects of surface light on a the pigment systems of specimens from subtidal habitats solution of 3 to 4 percent formalin in seawater buffered tablespoons of borax per gallon. Ethyl can affect other metabolic processes, they should be kept relatively cool and dark until placed in a killing made up (fixing) solution or fragile or rare plants. with 3 to 4 alcohol (70%, The best general preservative with fresh water) for longer storage. Plant is is recommended used for physiological work. and animal specimens should not be mixed. Permanent cies. slides may be made One common method clear corn syrup of microscopic spe- uses a solution of 80 percent and 4 percent formalin. The slides 9.9 ARTIFICIAL REEFS Artificial reefs are manmade or natural objects in- should be allowed to dry slowly; as the syrup dries, tentionally placed in selected areas of marine, estua- more should be added. The edges of the rine, or slide can be sealed with clear nail polish. fish habitats. Plants collected for histological study should be preserved in a manner that is appropriate for the particular technique to be used. In all cases, preserved specimens should be kept in a dark place, because exposure to light causes preserved plants to fade. 9-20 freshwater environments to provide or improve Much of the ocean, estuarine, and fresh- water environment has a relatively barren, featureless bottom that does not provide the habitat that reef fish need. Natural reefs and rock outcrops are limited; less than 10 percent of the continental shelf can be classified as reef habitat. Even NOAA if rough bottom consists of Diving Manual —October 1991 Procedures for Scientific Dives Figure 9-21 Fish Using Tires as Habitat Figure 9-22 An Reef Complex Artificial Photo Dick Stone, National Marine Fisheries Service Source: Grove and Sonu (1985) low-profile rock outcrops, fish it can provide a habitat for and invertebrates. Properly sited and constructed artificial reefs can provide the same enhance benefits as natural reefs. fish habitat, provide more They can accessible and high- quality fishing grounds, benefit the anglers and eco- nomies of shore communities, and increase the total number of fish within a given area. Artificial reefs function in the same manner as natural reefs. They provide food, shelter, spawning and nursery habitat, and orientation in an otherwise relatively featureless non-toxic solid wastes or surplus materials have been used in the United States to build reefs automobiles junked (Figure 9-21), and streetcars, damaged concrete materials, including gas and Christmas trees, oil and brush reef materials in fresh water. scrap tires pipe and building rubble, surplus or derelict ships, and tires, and fiberglass-coated tested in the United States. used commonly Japan and Taiwan. Fish aggregating devices in these have been used for many years in in the United States; the western Pacific. Although artificial reefs can enhance recreational and commercial fishing opportunities, creating a successful reef involves more than placing miscellaneous materials in ocean, estuarine, and freshwater environments. Planning artificial reefs. constructed, all is needed to ensure the success of species at the reef sites. Species, mean als, number of individu- and behavioral observations should lengths, be recorded on waterproof data sheets (see Section visibility 4 feet (1.2 is observations can be made by two m) or 9.3). or more, these more divers. Each observer makes counts by species for sections of the reef, and these are then totaled for the entire reef. The obtained by all observers are averaged for a totals mean species count of territorial and schooling fish, cardinalfish, morays, and certain groupers, the highest is used. Although count obtained by any one observer the accuracy of fish population estimates varies with visibility, species, and time of day, it is assumed that, conditions remain constant, the counts represent if population density. Photographs taken at intervals from the same location also can be used to count and iden- tify species. In this case, the photo print should be placed on a soft surface and a pin hole put through each identified fish; the print should then be turned over and the holes counted. Visibility should be meas- ured after taking the picture to compare the areas covered by different photographs. Diver-biologists have used direct observation tech- or part of a reef can disappear or break niques to demonstrate that artificial reefs can be used natural reefs in the vicinity. October 1991 site materials are improperly placed or If apart and interfere with commercial fishing operations or damage and any changes that occur over time are important pieces of information to researchers and managers. Also, diver estimates of reef fish populations can be made by direct counts of the number and on the grunts, and most porgies. For seclusive fish, such as plastic units have been Figure 9-22 shows an (FAD's) also are becoming popular of reef material have been popular recently, fabricated reef complex. Fabricated units are artificial The charting such as black sea bass, Atlantic spadefish, snappers, piles More numerous other documenting the suc- in structures. Rocks, structures such as Japanese-style fish houses, concrete structures, cess of an artificial reef. When environment. Many Divers can play a key role — NOAA Diving Manual augment productive natural areas. They have also shown that to reef and rough bottom these structures increase 9-21 Section 9 biomass within a given area without detracting from biomass potential in other areas. total clinometer can be cemented to a clipboard or to a plastic writing surface and a pencil can be attached with rubber tubing; a plastic ruler can also be mounted on the edge of the board (Figure 9-23). Other useful 9.10 equipment of a general nature might include: a GEOLOGY Diving is research. still, movie, or video camera; an assortment of small sampling an invaluable The advent tool for many aspects of geologic bags or vials; lights; 9.10.1 Mapping and small coring tubes. of scuba in the late forties and early fifties permitted easy access to the shallow subaqueous environment for the first time. The results of in-situ underwater studies soon began to appear in niques generally are applicable to research in lakes Three basic types of mapping can be accomplished under water: bathymetric, surficial, and geologic. Bathymetric maps display the depth contour of the seafloor. Surficial maps show the two-dimensional character and distribution of the material that comprises the seafloor, and geologic mapping projects a and rivers. The topics on the seafloor. the literature. Since that beginning, the scientific applications of diving have increased to the extent that many geologists now routinely use scuba as a research Although most underwater geologic research has taken place in shallow marine waters, the same techtool. categories three-dimensional analysis of the rocks that crop out in this section are — characterization grouped into two general and experimentation. Geological characterization includes mapping, sampling, and testing parts of the underwater environment, while experimentation deals with the real-time analysis of specific geologic processes. Experimental geological studies rely in part on information obtained from characterization studies, but they go much further in that they require extensive interplay between geology and other disciplines such as biology or fluid mechanics. Initially, underwater geologic research primarily involved the characterization of existing conditions, but such studies now routinely entail experimentation Bathymetric mapping is best done from a surface echo sounding equipment. Multibeam swath sonar systems are available in hull-mounted and towed fish configurations; although expensive, their accuracy is unsurpassed. A diver under water generally cannot match the range and efficiency, the accuracy of location, or the precision of depth determination and recording possible from a surface craft. However, in unnavigable water, or when taking precise measurements of a highly irregular bottom or of features too small to be resolved from the surface, underwater mapping may be the only craft with practical means of compiling the bathymetry. Bathymetric mapping can also be done as well. Although sophisticated methods have greatly expanded scientists' sampling abilities, careful observation is still the mainstay of most underwater geological studies. In some projects, observations may constitute the main data collected; in other cases, careful docu- in detail over a small bottom area to determine the area's microrelief. Small-scale bed forms are an example of an important geologic feature too small to be resolved from surface craft. These forms develop in response to near-bottom currents, and their presence indicates aspects of the of dynamics of the environment that otherwise may not be readily apparent. Moreover, such features may be preserved in the geologic record, where they are of the most important elements of underwater geological considerable use in deciphering ancient environments. accurate note-taking, coupled Scaled photographs of bed forms provide important mentation may be important either to select sampling sites later or to place a chosen study site into the larger context of its research, therefore, surrounding environment. is with agreement on what was seen. It is One advisable to supplement notes with a debriefing immediately after the dive and to record debriefing results along with information on shape and orientation. In mapping features such as sand ripples, however, the geologist needs to determine the average size of the bed forms The small size of the bed the underwater notes. over a section of seafloor. Although most research projects require specific equipment, there are some basic tools that a diving geologist should carry routinely. These include a compass, inclinometer, depth gauge, noteboard, ruler, and forms, the nature of the sediment, and the fact that bed or unidirectional currents create difficult sampling These are small items, and many of them can be combined into a single tool. For example, a small, oil-filled plastic surveying compass with in- Peterson's Wheel-Meter Tape Trianguiation Method. This trianguiation method requires a wheel that is mounted on a vertical shaft and that has a rim marked collecting bag. 9-22 forms often are located in areas of strong wave-induced problems. NOAA Diving Manual —October 1991 Procedures for Scientific Dives Figure 9-23 Underwater Geological Compass the table tops and the alidades are set on these. Two plane tables are placed on the bottom, one on each side of the and site, leveled. Initial sightings are made on a previously selected reference or primary fixed control point and across the site from one table to the other. Lines are inscribed on each plastic drawing surface with ordinary lead pencils and are then labeled. The resultant vectors, plus a between the two measurement of the distance points, establish the position of both tables on a horizontal plane. If the tables are not at the same elevation, the relationship a 19.7 foot (6 at the lower m) determined by placing is long calibrated range pole, weighted end and buoyed A the lower table. at the top with a float, sighting is made from on the upper plane, and the distance between the sighted point on the length of the pole and the lower table provides the Photo Robert Dill vertical elevation relationship. A diver diver in degrees. locations. The shaft is driven into the bottom at selected The 0-degree mark on the rim aligned is A meter tape, pulled out from the top of the shaft, measures the distance to any point, with the direction read on the wheel rim where it is with magnetic north. A crossed by the tape. around it, mounted slightly larger wheel, over and perpendicular to the first so that it can pivot allows elevations to be calculated from simultaneous readings of upward or downward angles. site, mans each of the two plane tables. moves the range pole from point to point and sightings are taken from each table and labeled marker up or down the pole until he from the diver manning one of the plane tables. The distance is then measured from that point to the object being positioned. The plane table diver uses the horizontal element of the cross hairs for this measurement. The efficiency of this method is limited by the clarity of the water and the diver, who moves a or she receives a stop signal requirement that three divers record each point. Meter Tape Triangulation Method. This triangulation method is preferable to Peterson's wheel method when small areas need to be surveyed under conditions of reasonable visibility. Although this method is time consuming, it is inexpensive, requires little equipment and only a few divers, and is especially adaptable to level and uncomplicated sites. Control points at known distances from each other are selected and marked on the seafloor around the site. Horizontal measurements with a meter tape made from two of these control points to any object or point on the site provide the necessary information for plotting the position on a used by archeologists. plane. object within the frame. is a simple Plane Table Triangulation Method. This triangulation method may be used in clear position triangulation and for taking elevations. plane tables are necessary. table, three is movable legs, water or on land, both for They consist of a and a weight. A Simple wooden simple alidade constructed by combining a sighting device, a tube Dumas Measuring Frame Method. precision frame is mapping for small areas has couplings. The and extension leveled a few meters above a sloping site, and the new sections into place. Using two frame as tracks, a horizontal crossbar mounted on wheels can be moved from one side of the doubled by fitting sides of the frame to the other. This crossbar, in turn, by a yoke holding a the vertical pole, centimeters. The is traversed The mobile crossbar, and the frame are calibrated in vertical pole. vertical pole is adjusted to touch any The coordinates of the point are recorded from three measurements read on the frame, the beam, and the elevation pole. The details around the point must be drawn by a diver hovering over portable 6.6 foot (2 m) grids placed directly on the site materials. grids are divided into 7.9 inch (20 sides of the grids. Diving Manual m) square metal extension couplings allow the size to be indefinitely are designated by — NOAA 16.4 foot (5 telescopic legs enable the frame to be weighted base. Sheets of frosted plastic are then tacked October 1991 A This method of been successfully fitted with four telescopic legs with cross hairs at each end, and a straightedge on a to third on the consecutively. Elevations are measured by the third method of making measurements under limited visibility conditions, using two divers equipped with voice communication. This A cm) These simple squares, which numbers and letters marked on The measuring frame is used to the fix 9-23 . Section 9 the positions of the corners of the grid. Although this method and the Dumas Measuring Frame method are no longer used extensively, they may be useful in certain Merifield-Rosencrantz Method. A marker stakes has been developed and tested by Merifield and Rosencrantz (1966). Two divers are used for the survey. The procedure of ground control reference consists of the following operations: rough sketch of the approximate locations of the points to be surveyed is drawn on a frosted plastic sheet for underwater recording. Using a tape measure, the between the various points determined. is A work of measurements should be made, forming a triangular net (three sides of all triangles); this eliminates the need for making angle measurements. When possible, more than the minimum set of measurements should be taken. For example, if surveying a square that has a point at each corner, all four sides and both diagonals should be measured. One of these measurements nometry and a hand-held scientific calculator. The is redundant, but it a set of adjoining box cores (the basic box coring tech- nique shown is sediment in Figure 9-24). Because the surficial box core in the may be modified during the when Newton (1968) covered the coring process, additional steps must be taken surface relief is desired. sediment surface with a layer of dyed sand followed by A lattice vertical heights unconsolidated sediment can be measured from one or simple method of determining the three-dimensional positions of a number slant distance True horizontal survey distances and microrelief of a small section of seafloor covered by circumstances. 1 3. are then calculated from these data using basic trigo- will enable the divers check the accuracy of the measurements and to detect errors. (Errors can easily happen when a large number of points is being measured.) to a layer of native sand to provide a protective covering before coring. After the core was impregnated with casting resin, the microrelief was obtained from slabs. This type of box coring is is not only time consuming but also extremely difficult to accomplish under the influence of strong currents. Ripple height and wave length can be established under water and, where closely spaced, the resulting profiles can be used to create a three-dimensional of a section of the seafloor. equipment used The map sophistication of the to establish ripple profiles differs greatly, and the corresponding resolution of the data varies accordingly. Inman (1957) used a greased "comb" (Figure 9-25) to obtain a profile of the large ripples that form in medium and coarse sand. In principle, this technique should give a fairly accurate profile of the 2. The vertical height of each point is measured using a simple but extremely accurate level. is A stake driven into the ground in the middle of the array of points. A clear plastic hose with an inner diameter of 0.37 inch (0.95 cm) is fastened to the top of the central end of the hose pointing down. The hose should be long enough to reach the farthest point to be measured. To set up the level, a diver first works all the air bubbles out of the hose. The free end is held at the stake, with one end attached to the stake. The diver then blows into the free end and fills the hose with air. As it fills, the hose will rise and form an inverted "u" in the water. The diver then swims to each point to be surveyed with the free end of the hose. A measuring same level as the is placed on the point and held vertically. The end of the hose is placed alongside the stick and pulled down until bubbles are seen rising from the fixed end of the hose. When this occurs, the water level stick free at the measuring stick fixed end, and the is even with the mouth of the vertical measurements can be read off the stick. If visibility conditions prevent seeing the fixed end, the hose at the free end should be pulled down slowly until the water level remains steady with respect to the measuring stick. When this occurs, come out of the free end, even keeps them from being seen. will 9-24 if bubbles poor visibility ripples as long as the spacing of the comb elements is small compared with the ripple wave length. In practice, the comb is awkward to use because it has to be handled carefully to prevent grease from fouling divers and equipment and to ensure that the adhered grains are not lost before the trace can be measured. If visibility permits, photographing a scaled rod laid transverse to the ripples produces a quick but accurate measure of wave length (Figure 9-26). To measure the small form in fine sand, Inman (1957) laid a Plexiglas® sheet on top of the ripples and marked off the crests with a grease pencil. Using this method, ripple heights could only be estimated, and the problem of ripple distortion by the Plexiglas® was always present. Furthermore, reliability decreases markedly when the current velocity increases because of scour around the sheet and the diver's inability to hold position long enough to mark the Plexiglas®. Underwater surficial mapping requires identification and delineation of the materials and features that compose the seafloor. In a small area, this can be accomplished more accurately by a diver at the underwater site than by instruments from a surface ripple ripples that craft. Surficial features (such as rock outcrops, coral unconsolidated sediment, and textural and compositional variations in the sediment) must be reefs, NOAA Diving Manual —October 1991 Procedures for Scientific Dives Figure 9-24 Box Cores (Senckenberg) for Determining Internal Structure in Sand (^ y\ / / -V / BOTTOM TOP — Senckenberg boxes aligned in o series, shown here as normal a northtrending shoreline (L). Box 81 is nearly completely emplaced boxes 82 and 3 partly emplaced. Spiral anchor screwed m sond behind boxes provides stability and leverage for diver b — Box filled with sand bottom plate secured with elastic band Box sides were taped together prior to sampling to prevent their spreading apart during emplacement c — Box on side in laboratory bottom pier moved d — Upper side of box detached and uppermost 2 to 3 cm of sand removed by careful troweling, e — Metal tray inverted and Taking and processing of sand box cores to identify internal structure, a to sand surface Orientation data transferred to tray f — Tray removed and sand leveled and dried. Orientation data ot g — Sand within tray impregnated with about 120 cc of epoxy resin. When resin has set orientation data is transferred the sand slab, h — Sand slob removed from tray, internal structure outlined by surface relief provided by preferential penetration o through individual beds Orientation data on underside of slab pushed into side of tray Source: identified, and their distribution must be traced and plotted to scale. The problems of locating underwater features accu- and of covering a sufficiently large area can be minimized by towing the diver-observer with a surface rately craft to NOAA (1979) In areas where the bottom can be seen clearly from above water, aerial photographs are useful to establish the general bottom configuration. The details can then be completed under water (Figure 9-27). Geologic equipped for precise navigation and communication mapping of the rocks that compose the seafloor is best accomplished by using seismic profiling techniques To ensure accurate location of features, mark the features with a float. the identification of a rock unit or the location of the with the divers. the towed diver should October 1991 — NOAA Diving Manual from a surface craft. If a specific question arises —such as 9-25 Section 9 Figure 9-25 Greased Figure 9-26 Diver Using Scaled Comb for Rod and Underwater Noteboard Ripple Profiling ' m / / 'V ^*',-^.*B^. Photo David Klise Photo David — direct underwater observamust be used to answer it. For example, a geologist may need to know the attitude (strike and dip) of sedimentary strata or of fractures, joints, and faults in surface trace of a fault Klise tion the rock. The strike of a rock the bed would bed is make when plane on the earth's surface. Dip is is the compass direction that with the bubble defines the dip and dip bearing. projected to a horizontal Some outcrops are located in water too deep to be sampled by these methods unless the diver is operating in the saturation mode. Where underwater sampling To fix the orientation of the bed, however, it is also necessary to know the dip. The dip is the angle in degrees between a horizontal plane and the inclined angle that the bed makes, measured down from horizontal in a plane perpendicular to the strike. The other crosshair, which now horizontal, defines the strike of the feature, and the downward direction of the crosshair coincident coincides with a crosshair. cannot be done, a photograph of the outcrop that includes considerable For any kind of underwater mapping, measured with a clinometer. These prepare a base relationships are illustrated in Figure 9-28. Rock outcrops on the seafloor one in Figure 9-29) can yield a amount of information. a scale (like the may be located by map on which established features are drawn New it is useful to the outlines of previously in indelible ink on a features can be sketched in noting irregularities in bottom profiles, anomalous shoals sheet of plastic material. or reefs, or the presence of organisms such as kelp that pencil on the base and, as they are confirmed, inked normally grow on rocks. The rock outcrop may be so onto the map. encrusted by bottom flora and fauna that recognition of features, such as stratification surfaces, fractures, and joint planes, geologist is difficult. In such cases the diving 9.10.2 must clean off the encrustations, search Sampling for freshly scoured surfaces, or collect oriented samples in Diving geologists sample everything from unconsoli- the hope of establishing the three-dimensional fabric dated sediments to surface and subsurface rock forma- of the rock in the laboratory. In some areas, differential weathering or erosion makes stratification surfaces and fractures more readily visible under water. directly in a few underwater situations, they usually To measure the attitude of planar elements in the adequate compass with an Underwater housings can be built for the relatively large surveying compasses commonly used tions. Although standard land techniques can be used must be modified to (or new techniques must be developed) cope with the underwater environment. Diving allows which when using rocks, the diver needs an selective sampling, inclinometer. boat-based methods. The diver sees exactly what on shore. A hollow plastic dish almost completely Filled with fluid (plastic petri dishes work well) and marked with perpendicular crosshairs on the flat useful adjunct to underwater mapping. surfaces The placed in the plane of the feature whose attitude be measured and rotated until the enclosed 9-26 air is dish is a is to bubble collected and how it is not possible is relates to other aspects of the submarine environment. Compromised samples can be discarded and easily replaced. Also, diving may be the only way of sampling the seafloor in areas, such as the high-energy surf zone, inaccessible to surface craft. Rock sampling may be required of an underwater geologic NOAA map in the compilation or to answer other Diving Manual — October 1991 Procedures for Scientific Dives Figure 9-27 Aerial Photograph and Composite Map Courtesy U.S. Geological Survey may be 4-cylinder industrial motor, which limited the type of they can be traced to a particular outcrop. surface vessel used for support. Smaller units have are the most reliable, although talus fragments adequate if Breaking through the external weathered or encrusted rind of a submarine outcrop may be water makes swinging a hammer difficult because impossible; a pry bar or geological pick can be used in existing fractures or can be driven against an outcrop with better effect. Explosives may be practical in some cases but must be used with extreme care (see Section 8.12). Pneumatic, electric, or work hydraulic drills are available for underwater (see Section 8.4). diver-operated drill m) (Figure used 9-30). in The water depths up to 49 feet drill consists of a Stanley hydraulic impact wrench (modified for consistent rotation) that surface. The is been designed that is a powered by drill rotates at a a hydraulic maximum pump of 600 on the rpm and provides sufficient torque to core under any reasonable Glynn 1976, Macintyre 1977). recover cores roughly 2 or 3.5 inches utilize more portable unit, of Macintyre's original design, cores over 82 feet (25 in (Halley et al. 1977, Hudson 1977, Shinn Marshall and Davies 1982, Hubbard exposed in water less reefs, a tripod is diameter, using a double-walled core barrel. October 1991 — NOAA Diving Manual drill bag can be used in place of the tripod. Using the habitat Hydrolab in the U.S. Virgin Islands as a base, Hubbard and his lift coworkers (1985) were able to core horizontally into the reef face in water depths of 98 feet (30 m). On such deep operations, bottom time a diver in 1977. al. required to support the (Figure 9-30). In deeper water, a The cm) et et al. 1985). than 6.6 feet (2 m) deep or on In addition to tending the (5 or 9 m) length have been retrieved with these newer systems conditions (Macintyre and unit will 5-10 hp motors. The result weighing about 350 pounds (159 kg), that can be operated from a small boat. Although this approach reduces the flow rate over that For use Macintyre (1977) describes a hydraulically powered, (15 Macintyre's original unit was powered by a Triumph Samples broken directly from the outcrop questions. and is needed to note to is usually the limitation. normal operation of the drill, monitor the progress of the coring anything that would be useful in logging 9-27 Section 9 Figure 9-28 Dip and Strike of Figure 9-30 Coring in a Deep Reef Environment With a Hydraulic Rock Bed Block diagram due east, illustrating dip and shown by arrow; amount Drill strike. Direction of dip of dip, angle abc. Notice that arrow extends horizontally as it would if placed flat on a map. Direction of strike is north-south, shown by crossarm of symbol; it represents a horizontal or level line drawn on inclined bedding plane. Photo Holmes (1962) Figure 9-29 Geologist Measuring Dip (Inclination) of Rock Outcrop Photo Eugene Shinn The hydraulic drill is also useful in obtaining shorter samples through large coral heads for the purpose of examining internal growth bands. single-walled barrel is A fitted to the larger diameter, same drill and is used to remove a plug from the coral colony. Because method is meant to be non-destructive, great care must be taken not to damage the surrounding colony. Some researchers have inserted a concrete plug into the hole they have drilled to promote overgrowth of the this colony by algae. Photo Larry Bussey A the core at the surface. submersible drilling frame can solve some of these problems when divers are working in deeper water. Adjustable legs allow deployment on an irregular, sloping bottom. The frame securely holds bag can be used either the drill in place, while a lift place pressure on the or to drill using a video camera, the drill and divers are needed only cores. 9-28 lift it out of the hole. to By can be monitored remotely, to set up and recover the The drill 100 psi (7 that is (Figure 9-3 la), which can operate at about kg/cm 2 ), is attached to a neoprene hose fitted to the low-pressure port of the first stage of a regulator, which is attached to a standard scuba cylinder. The sample forced up into the middle of a core barrel is drill bit is attached to the bit. designed so that the core This barrel, in turn, sample when the barrel is designed to removed from the bit. The barrels containing the sample can be removed, and new barrels can be attached by the diver retain the core is under water. The best cores can be obtained by running NOAA Diving Manual — October 1991 Procedures Tor Scientific Dives Figure 9-31 Pneumatic Hand A. Drill and Attachment Drill The sediment beneath the seafloor may have been deposited under conditions markedly different from those producing the surface sediment; will differ accordingly. How is character its mud? How containing interlayered sand and sample if so, does one sample a sediment large a required to be representative of a specific particulate trace component, such as placer gold, without some component, such biasing the sample by the loss of as the finest or densest material? Many of these questions have been addressed in conjunction with subaerial sampling, and the techniques employed in this form of sampling are applicable to underwater sampling as well (Clifton et X Ray B. Core of al. 1971). Surficial samples taken with a small core tube circum- vent many sampling problems and permit consistent collection program. centimeters in a highly Plastic core tubes several diameter with walls a millimeter or so thick are ideal and inexpensive. Cut into short tubes numbered and have several centimeters long, they can be rings drawn (or cut) on them 0.39 to 0.78 inches (1 to 2 cm) from the base and top (depending on the thickness of the sediment to be cored). Two plastic caps for each Photo Collin W. Stearn tube complete the assembly. The tubes are carried uncapped by the diver to the collection site. A tube is the at drill on the maximum make the its to bit penetration of the bit motion of the permit it to is carefully over the top of the tube. Its A in diameter and up cm) long have been obtained with single 72 cubic foot (2 m 3 ) scuba cylin- der is sufficient to drill 4 holes in the coral Montastrea annularis at depths up to 23 feet (7 m) (see Figure 9-3 lb). Because this equipment is not designed for use in salt water, extra care must be taken after use to rinse and clean it to avoid corrosion. number is the full break the core free and cm) sediment until the ring on the side pressure be removed from the hole. Complete (1 into the coincides with the sediment surface, and a cap completed, a slight rocking bit in the hole will to 33.5 inches (85 method. When hole quickly. unfractured cores 0.39 inch this maximum speed, with pushed along with a description of the sample location. or rigid plate the tube is is is placed recorded, A trowel slipped under the base of the tube, and then removed from the sediment and inverted. The second cap is placed on the base, and both caps are secured. This simple arrangement can be improved by adding a removable one-way valve to the top end and a removable core catcher to the bottom. These items allow the diver to insert and remove the core without capping it. Capping is done at a convenient time, and the end pieces are then transferred to another tube for reuse. Further details concerning also present An inexpensive alternative to a core tube is to cut one end off a 50-cc disposable syringe and to use it as a small piston core. The sampler is pushed into the sediment while the syringe plunger is being withdrawn problems. The collection technique used depends on slowly to keep the sampler at the sediment surface. this technique can be found in Stearn and Colassin (1978). Sampling unconsolidated sediment generally than sampling solid rock, but it may the purpose of the study. For example, if is easier samples are The plunger provides enough collected for compositional or textural analysis, the sampler primary concern losing a larger entity. is On to obtain material representative of the other hand, if internal structure or engineering properties are the goal, the sample should be as undisturbed as possible (see Section 9.10.2). number For example, how Collecting a representative sample creates a of problems that must be resolved. deep below the surface should the sampler penetrate? October 1991 — NOAA Diving Manual to suction to permit the small be removed quickly from the bottom without any sediment. The sample can then be extruded sample bag, or it can be kept in the core tube by capping the tube with a small rubber stopper. into a Undisturbed samples of seafloor sediment are valuable for identifying internal structures, such as stratification or faunal burrows, and for of certain engineering properties. making measurements Compared with the 9-29 Section 9 brief view of the seafloor possible during a single dive, to a stationary pole so that the piston analysis of these structures provides a broader per- sediment surface during coring can increase the penetration of this apparatus to several meters. Recently, spective on processes through time. Internal stratifi- remains at the have constructed a coring apparatus that cation, considered in light of sediment texture, can be scientists used to infer the strength of prevailing currents during used a hydraulic jack hammer. The jack The hammer is orientation of cross-strati- attached to one end of a section of 3 inch (7.6 cm) in fication indicates the direction of the stronger currents in diameter aluminum irrigation tubing cut into the the time of deposition. the system and may indicate the direction of sediment The degree transport. to which mixing by faunal necessary lengths. made by The attaching device press-fitting a collar to a is a slip-fit standard jack hammer upper 6 inches burrowing disrupts these structures is indicative of the rate of production or stratification, which in turn reflects chisel shaft. Slits are also cut into the the rate of the occurrence of physical processes and/or water. During operation, the entire device the rate of sedimentation. the water with an air bag or air-filled plastic garbage cm) of the core tube (15.2 to allow for the escape of is suspended in seafloor sediment also can. Holding the core pipe in a vertical position, the provide a basis for interpreting ancient sedimentary diver releases air from the air bag and descends slowly Internal structures of modern environments. Direct comparison of depositional features in a be rock outcrop with those in an individual core difficult core. This may because of the limited view permitted by a problem can be overcome, to a degree, by taking oriented cores in an aligned series, which yields a cross section that is comparable with that in the the trigger oriented vertically, is pressed and the tube is is jack-hammered m) of penetra- into the bottom. Generally, 19.7 feet (6 tion attained in about 30 seconds. Experience has is shown that loss up compaction is less than 10 29.5 feet (9 m) in length have been due to to The obtained using this method. collection of undisturbed samples from the seafloor requires special coring techniques. Diver- operated box cores have been used successfully to core the upper 3.9 to 7.8 inches (10 to 20 cm). removed are useful in muddy at the is layer can be lost or sediments. With their tops off, they can be pushed easily into the the top Cans from which the bottoms have been similar containers mud until sediment surface level (the surface the container is pushed below the if sediment surface). The opening at the top of the container sealed by a screw cap or stopper after the can emplaced in the is sediment, and the sediment remains intact as the core is withdrawn. A wedge-shaped or spade corer permits the taking of somewhat larger Cores can be taken in sandy sediment with a variety of devices, ranging in design from very simple to quite complex. Cores more than 6.6 feet (2 m) long can be taken by driving thin-walled tubing several centimeters diameter into the sediment. A simple apparatus removable collar that can be attached firmly to a 3 inch (7.6 cm) in diameter thin-walled in consists of a irrigation pipe. 3 inch (7.6 welded to collar. By cm) it is A pounding sleeve consisting of inside diameter pipe with a two pipe handles slipped over the irrigation pipe above the forcefully sliding the pounding sleeve onto the collar, a 3.3 to 6.6 foot (1 to 2 m) down core can be taken (the core tube must be long enough to allow for the core and enough pipe above the collar to slide the pounding A different type of apparatus used for underwater coring is the vibracore, which relies on high-frequency vibrations rather than pounding to push the core tube through the sediments. The core tube into the bottom as possible and is is driven as deeply then extracted; dur- ing extraction, the vibration source is turned off. Several excellent but costly commercial units are available; a less-expensive unit can be constructed by attaching a simple concrete vibrator to the top of a 3 inch (7.6 cm) piece of irrigation pipe. The unit can be powered by a small motor located in the support boat; cores 32.8 feet (10 m) long have been taken with this type of unit. Subaqueous cores are saturated with water when surficial cores. 9-30 ascertaining that the core tube percent. Cores outcrop. is tube makes contact with the bottom. After until the sleeve). Adding a removable piston attached they are removed from the bottom and must be handled carefully to avoid destroying them. For example, unless may be washed from removed from the water, be liquefied by excessive agitation, or collapse during removal from the corer. The careful geologist avoids these frustrations by planning core retrieval and transport as an integral great care is the corer as taken, the sediment it is part of the coring system. Other types of geologic samples can be collected by For example, gas escaping from seafloor seeps may be collected more easily by a diver/scientist operating at the seafloor site than by scientists working from a surface craft. Hydrocarbons in the sediment can be analyzed with greater precision when the samples have been taken by divers. These containers can be divers. NOAA Diving Manual — October 1991 Procedures for Scientific Dives Figure 9-32 Diver Taking Vane Shear Measurement sealed immediately after sterilization, be opened under water, and then be resealed with the sample inside before being returned to the surface. 9.10.3 Testing means determin- In the context of this section, testing ing some variable of the sediment in situ that same sediment. For example, the cannot be from a sample of and Moore (1965) identified accurately on the surface Dill modified a commercial torque screwdriver by adding a specially designed vane to the shaft. inserted carefully into the sediment, The vane was and torque was slowly and constantly increased until sediment failure occurred (Figure 9-32). From this simple authors were able to determine the They strength of surface sediments. test, these maximum shear also measured the "residual strength" of the sediment by continuing to twist the dial after initial shear occurred. equipment generally is because the diver has test to Use of this restricted to currentless locales to remain motionless during the be able to operate the apparatus correctly and accurately. Photo Lee Somers 9.10.4 Experimentation The underwater environment a is superb natural laboratory, and diving permits the geologist to study a number of processes in real-time experiments. Most studies of this type begin with a careful characterization of the study area, followed by an experiment (usually carried out over an extended period of time) designed to explore the interrelationships logical, physical, among geological, bio- equipment such as sonic pingers (see Section 8.3) may be needed under adverse conditions. Current technology has advanced to the point where Loran C navigation systems can guide a boat to within less than 20 feet (6.1 m) of a previously visited site. Such units are readily available and can be used on small boats. Surface buoys tend to arouse the curiosity of recreational boaters, who may tamper with and chemical processes. or even remove them, and land- The experimental technique may be simple or sophisticated, depending on the nature of the phenomenon marks are seldom close enough studied and the resources of the experimenters. Repeated stakes at the actual site must be done carefully so as observations at a selected site can produce much information on processes, such as bed-form migration or bed erosion and deposition. When visibility permits, real-time video, cinephotography, or time-lapse photog- useful, especially when to the actual site to visibility not to alter the current flow is enough to be Emplacing poor. compromise experimental results. Some experiments involve the emplacement unattended sensors that monitor conditions of at specific raphy produces a permanent record of an ongoing process times or whenever certain events occur. The data from that can later be analyzed in great detail. Monitoring a such sensors are either recorded with sophisticated sensors can, for instance, yield by cable or radio in situ or transmitted to a recording station. Relocation is quantitative information on the interaction of perti- necessary to maintain or recover the equipment used in nent physical and geologic variables. such experiments. site Since making many experimental studies in nature involve serial observations of the experimental site may have to same be reoccupied Characterization studies will continue to be the main- the stay of underwater geologic research because most of to continue them can be completed without elaborate equipment. site, the study or to service equipment. Relocating the site In-situ and must be planned ahead of time. A buoy, stake, or prominent subaqueous landmark may become can be difficult suffice in clear, quiet water, while October 1991 — NOAA more sophisticated Diving Manual experimental studies, however, increasingly important as cover the advantages they offer will more in undoubtedly geologists dis- answering funda- mental questions about the geologic environment. 9-31 Section 9 Figure 9-33 Undersea Instrument Chamber MICROPHYSICAL OCEANOGRAPHY 9.11 Micro-oceanographers have so far not taken advan- full tage of diving techniques; to date, in-situ measurements and observations of water mass processes have not been widely used. Turbulent cells, boundary layers, and flow regimes have not been studied extensively. Notable among published accounts are the studies of visual indications of the thermocline, the use of tracers to reveal flow patterns and the study of 1971), dye (Woods and Lythgoe waves and the formation (LaFond and Dill 1957). Hydrolab has shown that internal of bubbles in sound attenuation Work by Schroeder (1974) divers can be used to do in more than emplace, tend, and recover oceanographic instruments. Divers are the best means of ascertaining the measurements of the The oceanographic scientist today dives to implant instruments in the active parts of the water column and to ensure that these instruments are measuring the real underwater scale of physical nature of the water column. world. Table 9-1 summarizes some of the micro-oceano- graphic variables and problems that involve the use of divers in data collection. As better methodology develops, the diver's role in micro-oceanography will expand. ( 9.11.1 Emplacement and Monitoring of Instruments The implantation, reading, and maintenance of instruments and instrument arrays and the recovery of samples and data are important jobs divers can perform in oceanographic surveys. Instruments implanted at a site to measure current flow, direction, or other phenomena may be damaged by marine growth or the buildup of sand or bottom debris. If the instruments are read remotely, these conditions of the data may alter the validity measured by the instrument. Divers should routinely check the condition of implanted instruments to Photo Morgan Wells ensure that they are operating correctly. Undersea laboratories are of great advantage imental studies requiring the use of many in exper- instruments and dives of long duration. The Undersea Instrument Chamber (USIC) provides a stable underwater housing for instruments that record oxygen, temperature, pH, conductivity, and sound. The light, USIC can be entered by divers as necessary for data retrieval equip- ment, calibration, and monitoring (Figure 9-33). A good diver-managed oceanographic instrumentation program was carried out during a Hydrolab underwater habitat mission in 1972 (Schroeder 1975). The objective was to evaluate a continuously deployed shallow-water current and hydrographic monitoring system. Divers set up thermometers, current meters, 9-32 pressure gauges for tidal measurements, and instru- measuring depth, temperature, conductividissolved oxygen, and pH using a taut line buoy array. Data were obtained by reading the instruments and/or by a direct readout display inside the ments for ty, salinity, habitat. When reading a vertical array of the thermometers, the procedure was to swim at an angle to the top thermometer, read line to it, and then to descend the buoy read the remaining thermometers. The data were transferred onto a slate secured to the anchor weight of the buoy system. This procedure prevented the aquanaut's exhalation bubbles from disrupting the thermal structure. NOAA Diving Manual — October 1991 ( Procedures for Scientific Dives Table 9-1 Micro-Oceanographic Techniques Variable Temperature Instrument/ Diving Technique Mode* Thermometer array as Placement Problems Remarks Taut-line buoy, Where Limited by bottom pier, piling, mometers. Pre and post use time oil rig. calibration. Reduires modes. to position ther- in conventional repetitive observation. Recording thermograph Same as above but secure to bottom. C.S Equipment flooding. Relocation of units. Electronic failure. Only one data point unless multiple units used. Remote readout Same C.S as above. Same as above Excellent for use in habitat. Water samples Salinity C.S Bottle rack Number carried by Processing procedures. of samples. Dissolved salino- Same as for Temperature, above Remote readout Same as tor Temperature, above Water samples C.S Oxygen time in conventional modes diver. Recording meter Limited by bottom Bottle rack Outgassing when brought Best carried by to surface. a habitat Reverse vertical Fouling of cables. Excellent for profiling using Interface at surface. habitat operations. used from divers. Multiple Remote readout Same as for Temperature, above Recording Same as for Temperature, above Remote readout C.S Sensor Unit floats and pulley system. Currents Recording Same as for Temperature, above Remote readout Same as for Temperature, above Recording (waves) Same as Ambient pressure S Dye Tides studies gauge inside for Temperature, above Gauge inside habitat. habitat "C = conventional diving S = saturation diving Source: 9.11.2 Planktonic Studies NOAA screw-type anchor or other anchoring device (1979) in the Diving techniques have long been an integral part of lake bottom and attachment of a collapsed bag held in experiments on the effects of controlled nutri- a vertical position by a submerged float (Somers 1972). in-situ ent enrichment of phytoplankton lations. bags at and zooplankton popu- Lake Michigan, divers implanted large plastic various depths, which required placement of a In October 1991 — NOAA Diving Manual Divers could then insert a hose into each bag to tate filling with lake water facili- and nutrient solutions. After the filling process was completed, the divers 9-33 Section 9 disconnected the hoses and secured the Water samples were taken a hose and pump. The role of zooplankton filling tubes. periodically by divers using vidual vortexes rapidly lose their own motion and low the ambient flow. The pellets are sealed proof polyethylene strips until needed. Three sizes, in a coral reef system was each with the same aspect ratio, are used: the smallest, studied by divers working from the Hydrolab under- described above, gives the most regular water habitat during three saturation missions (Schroeder only for about 5 minutes. et al. fol- in water- 1973). Plankton samples were obtained by divers in The wake but lasts largest, 0.24 inch (6 mm) mm) diameter by 0.09 inch (2.3 thick, can lay a The speed using small nets attached to a hand-held diver pro- streak through the whole thermocline. pulsion vehicle (see Section 9.5.1). Several variations these pellets this technique have been used and are described in Schroeder (1974). To quantify the volume of water filtered by the sampling nets, the area of the net mouth was multiplied by the distance traveled. Samples were preserved by pouring the contents of the cod end of the net into a jar filled with filtered seawater and sealing it with plastic wrap. The sample was then preserved by injecting formalin through the plastic by syringe and capping the jar immediately. A second method of sampling zooplankton in inac- zontal velocity encountered along any streak, on drop path is is comparable and their means that the cannot be determined from a single often quite complex, which velocity profile photograph. Instead, the layer of mean shear across any given obtained in successive frames of a timed sequence is still of to the difference in hori- photographs or motion pictures. The general procedure is as follows: after identify- ing the area of interest by dropping a trial pellet, the cessible areas, such as small caves in coral, involves a photographer positions himself or herself above the chosen level and then signals an assistant who is floating above and upstream to release a second pellet. As suction system utilizing air from a scuba tank to create the second pellet begins to a vertical water current in a 7.9 inch (20 cm) tube with a plankton net secured to the top. When used capable of capturing even fast- properly, the device moving small reef is plastic fall, the assistant increases buoyancy, which permits the assistant to move away from the dye streak without disturbing it. Whenever possible, the assistant is positioned above his or her the sheet overlaying the layer being filmed; this sheet fish. movements from the dye. The photographer then films the dye streak, keeping the sun behind the camera to increase contrast. Current can also be measured near the bottom by using dye tagging techniques (Figure 9-34). Care must be isolates the assistant's 9.11.3 Use of Dye Tracers In addition to the emplacement and monitoring of instruments, divers have used dye tracer techniques to measure currents, internal waves, thermoclines, and various turbulent components of the water column (Woods and Lythgoe 1971). Water masses tagged with fluorescein dye can be followed and photographed to provide an accurate measurement of current speed and direction. If a point source of dye (a bottle full of dyed taken not to kick up sediment or to create artificial released into the current, accurate measure- column, care should be taken to minimize the amount of activity around the study sites to avoid unnecessary water) is ments can be made at speeds lower than those of most current meters commonly employed. To understand the generation of turbulence inside a thermocline and within the water column, it is know both shear. The most necessary to the density gradient and the velocity vortexes by swimming in the area during such studies. Water Samples When taking measurements 9.11.4 or samples in the water mixing of the water column caused by vertical water currents from the diver's exhaled bubbles. Instruments should be placed well away and upstream of all bubble activity. to Divers can collect bulk water samples by swirling drop a tiny pellet of congealed fluorescein through the large plastic bags through the water until filled, sealing layer under study. Disk-shaped pellets, 0.12 inch the mouths of the bags, and carrying the bags to the convenient technique for laying a shear streak (3 mm) in diameter and 0.6 inch (1.5 mm) is thick, are particularly useful. These pellets are attached to a light line and dropped through a thermocline. The dispersion of the dye by the ambient flow can then be photographed. The only disturbance caused by column is caused by the formation of a small vortex wake, whose indito the existing flow the pellet's passage through the water 9-34 Because large water samples are heavy, the bags should be put into rigid underwater containers that are then attached to the boom of the ship. The plastic bag sampler can be modified to collect more precise water ship. samples by gluing or stapling a strip of wood or plastic to each edge of the bag opening, so that it will extend from the corner to about two-thirds the length of the The remaining third of the open end is then opening. NOAA Diving Manual — October 1991 Procedures for Scientific Dives Figure 9-34 Dye-Tagged Water Being Moved by Bottom Current of the air-filled jar is buoyancy sufficient to disturb the of the diver, requiring constant attention to depth regulation When and distracting the diver from the task at hand. standard ship-operated water samplers are used, the divers and ship personnel can precisely position and trigger the samplers under water. It is measures of difficult to obtain accurate dis- solved oxygen in seawater because the changes in pressure which to y^> a sample of seawater is subjected as it is brought to the surface affect the chemical nature of the solution. Liquids and solids are relatively insen- but dissolved gases are sensi- sitive to pressure effects, tive to pressure as / if taken up when the container / Courtesy U.S. Navy the container is protected raised through the water column, oxygen is it changes. Even may be opened on the surface. To overcome this limitation, a sampler that is portable, versatile, and inexpensive has been developed (Cratin et al. 1973). This sampler and technique are equally effective for operations from the surface or from an ocean floor laboratory. The sample PVC is bottles (Figure 9-35) are constructed mm) folded back against one of the supports and lightly closed with tape or a rubber band to prevent water from from entering the bag. To begin sampling, the diver pulls the two mouth supports apart, breaking the tape or rubber band, and opens the bag to form a triangular mouth. The bag will fill entirely as the diver pushes it provides a volume of about 0.24 quart (225 ml). Screw forward. The diver then closes the supports, refolds the end back against one of the supports, and rolls the edge tightly toward the bottom of the bag to seal in the water sample. Large plastic bags also can be filled loose using hand-operated pumps. When shipboard analysis requires uncontaminated samples, new, acid-washed, hand-operated plastic bilge pumps can be used to collect 1.9 inch (48 caps made tubing that mm) i.d., is and 2.4 inches (60 4.7 inches (12 of plastic and fitted with cm) PVC long, o.d., which inner linings and rubber O-rings effectively seal both ends of the sample bottle from their surroundings. A hole, 0.59 inch (15 mm) in diameter, each sampler and a piece of mm) is drilled into the side of PVC tubing 0.59 inch rubber membrane and over the small PVC tubing. When taking large numbers of samples, a backpack designed to fit over double scuba tanks is a useful accessory (15 is long is sealed into it. Finally, a fitted into (Figure 9-36). A samples. Smaller water samples, up to 1.06 quart (1 L), can be taken with extreme precision using a plastic or glass jar with a 2-hole stopper, one hole of which is fitted with a flexible sampling tube of selected length and diameter. At the desired depth, the diver inverts the unstoppered jar, The stopper. jar purges is it with air, and then inserts the place. then righted and, as the air bubbles out of the open hole in the stopper, the diver manipulates the sample collection proceeds as follows: the open i.e., without the screw caps, is moved to the underwater location, tapped several times to ensure complete removal of all trapped air, and one of the caps is screwed on. A marble is placed into the sample bottle and the second cap is then screwed firmly into bottle, sampling tube to vacuum organisms, or detritus into the jar. the water sample, After evacuating all To prevent oxygen from ongassing when is the sample brought to the surface, two chemical "fixing" solu- tions are added in (hypodermic) needle the following manner: a venting is placed into the membrane and the diver seals the jar by inserting the tip of the .0042 pint (2 ml) of manganese (II) sulfate and alka- sampling tube into the open hole of the stopper or by potassium iodide solution are injected into the by hypodermic syringe. (Special care must be taken to make certain that no bubbles of air are present in any of the syringes.) The bottle is shaken several times to ensure complete mixing. (The dissolved oxygen gas is converted through a series of chemical reactions the air, swiftly replacing the stopper with a cap. remains in the with water when air tion is A top of the sampling jar and the stopper is bubble of is replaced removed. Contamina- generally insignificant. Bottles larger than 1.06 quart (1 L) are inconvenient because the buoyancy October 1991 — NOAA Diving Manual line bottle 9-35 Section 9 Figure 9-35 Diver Using Figure 9-36 Water Sample Bottle Water Sample Bottle Backpack Source: into a white insoluble solid When —manganese III NOAA hydroxide.) the samplers are taken to the laboratory, they must be kept under water as added insurance against leakage. Once in the laboratory (with the bottle water), a venting needle is inserted into the still Photo William (1979) under membrane L. High As more people have discovered the advenand monetary rewards of shipwreck diving, government resource managers and scientists have become increasingly aware of the need to preserve and protect artifacts. ture historic shipwrecks. Although this section deals primarily with shipwreck and .0042 pint (2 ml) of concentrated sulfuric acid is added via a hypodermic syringe. The bottle is shaken several times to ensure complete reaction. The sampler is then removed from under the water, one of the caps is carefully unscrewed, and known volumes of solution are withdrawn. A knowledge of the volumes, concentrations of reacting chemicals, and other pertinent archeology, research on prehistoric remains that are data enables the analyst to calculate quantitatively the than 10,000 years. Figure 9-37 shows a diver recovering oxygen content nique is seawater. Use of this sampling tech- may limited only by the depth at which a diver safely work. much in Oxygen analysis of samples taken from greater depths requires more complicated and expensive equipment that can be operated remotely. under water is conducted for other purposes as well. For example, extensive work has been done in Warm Mineral Springs (Cockrell 1978) and Salt Springs (Clausen 1975), Florida, to depths of more than 200 feet (61 m), to obtain information on the area's early animal and human inhabitants, who date back more Indian artifacts off the coast of California. The real boom in archeological diving in the United States has involved shipwrecks. the more It is estimated that, of than 2.5 million certified recreational divers in the country, about 200,000 are wreck divers. In more than addition to recreational divers, there are 1000 active salvor divers 9.12 ARCHEOLOGICAL DIVING 20 years, diving methodology and technology have had an enormous impact on the scientific development of underwater archeology in the Americas (Burgess 1980). Archeological procedures developed Over the in the in the trained marine archeologists, last 1960's for use on shipwrecks in the Mediterra- country. Professionally who number no more than 100 in the United States, thus comprise the smallest group of wreck divers. It is estimated conservatively that there are well over 100,000 shipwrecks in United States waters. Available data indicate that close to 90 percent of known shipwrecks on the Continental Shelf are located in depths of less than 60 feet (18.3 m). Along some parts nean by Bass (1966, 1970, 1972, 1975) and his associates have been adopted and modified by professional archeologists in the United States to study both sub- of the coastline, shipwrecks are clustered in large many bers within a few hundred meters of the beach. merged prehistoric and historic sites. Since then, archeologists have conducted historical and/or anthro- Thousands of recreaand professional salvors have also become involved with wreck diving in their search for historic pological research on shipwrecks. tional divers 9-36 numMost harbors and inlets are rich in shipwreck sites. The rivers, estuaries, and navigable channels waterway also contain thousands of shipinland of the Great Lakes, wrecks from many different periods. NOAA Diving Manual — October 1991 Procedures for Scientific Dives Figure 9-37 Diver Recovering Indian Artifacts and grid mapping, and photomosaic surveys, are well-known procedures on land sites and are described in detail in archeologiartifact triangulation, plane table cal publications (see Sections 9.2.1 method and theory the and 9.10.1). Although of underwater archeology are similar to those used to conduct excavations on land, operating procedures for mapping sites can be very The best modify these different because of underwater conditions. way for archeologists to learn techniques how to by borrowing from the experiences of is marine biologists and geologists and by experimenting with various methods to ensure that reliable descriptive data are obtained. 9.12.2 Shipwreck Excavation Every historic shipwreck presents unique problems with respect to the archeological methods required to excavate. The depositional environment of each site how shipwreck remains are to be uncovered and recorded in situ. No two wreck sites are exactly the same. Shipwreck discoveries made since largely governs the early I960's along the coasts of Florida, Bermuda, the Bahamas, and throughout the Caribbean have shown that ancient wooden-hull shipwrecks do not stay intact for as long as formerly believed. Shallow water shipwreck remains are subjected continuously to the onslaught of the sea. Because the vessels' super- structures are degraded by the impact of currents, storms, and shifting overburden, visual remains often Courtesy Diving Systems International Photo Steven M. Barsky 9.12.1 Shipwreck Location and Mapping Underwater archeologists use many of the same techniques and much of the same equipment as other marine scientists. The two principal methods of locating shipwrecks involve the use of visual search and remote sensing techniques. Visual search procedures are discussed in Sections 8.2 and 9.1 to 9.3. Within the are not easily recognizable on the sea bed. Before excavation, a 1986). number make objective of these techniques to obtain reliable that accurately reflect of these mapping techniques, such October 1991 — NOAA the horizontal Many as baseline offsets. Diving Manual and unnec- the operation efficient ples of the environmental and logistical information needed include: • Measurements of the bottom topography and rates of sedimentation to determine the type of excava- equipment needed Sub-bottom profiles to determine sediment layers tion relative to • Number at the site • and stratigraphic relationships between different types of artifacts within overall artifact scatter patterns. more Exam- of different The primary sites. measurements essential to determine the is to avoid • techniques to survey underwater is it essary expenditures, accidents, and mistakes. shallow water shipwreck remains scattered over miles Marine archeologists use ship's ballast general character of the environment, which helps to sophisticated with respect to locating and defining (Mathewson 1977, 1983, its last decade, remote sensing techniques have become highly of open ocean The and lower hull structure, may be covered by tons of sand, mud, or coral. Figure 9-38 shows a marine archeologist exploring the wreck of the Golden Horn. contents, along with If site, and/or coring requirements work days and best time of year and the weather conditions Movement bility, • wreck or of work to to be expected of suspended materials, underwater wave action, current, visi- and temperature near shore, usefulness of shore area as land base. work area, and living area. 9-37 Section 9 Figure 9-38 Archeologist Exploring the Golden Horn cm) 3 to 14 inches (7.6 to 35.6 diameter greater than cm) are very difficult for individual divers to handle. sand or mud When needs to be removed from a wreck larger diameter pipe more is with a in diameter, airlifts 8 inches (20.3 effective. When deep site, the uncovering fragile artifacts, particularly in the presence of large amounts of organic matter, however, a 3 or 4 inch (7.6 or 10.2 cm) airlift is essential. The principle of airlift operation is described in Section 8.9.2. with water depth because Airlift efficiency increases the trapped air expands as ascends it in the pipe; air- lifts are consequently not very effective in water depths of less than 15 feet (4.6 m). Exploratory test holes 6 feet m) in diameter can be dug cm) airlift in 45 feet (13.7 m) of water to define the perimeter of a site. When excavating around fragile artifacts, the airlift should be used more as an exhaust for removing loose overburden than as a digging instrument. Instead of using the (1.8 m) deep and 10 feet (3 quickly with a 6 inch (15.2 suction force of the airlift to cut into the sea bed, divers should expose artifacts by carefully hand-fanning the bottom deposits into the pipe. In this way, fragile artifacts can be uncovered without being sucked up the pipe. Because even experienced divers lose artifacts pipe, the use of a basket or grate at the other essential. The most common problem with up the end is airlifts is drawn that large pieces of ballast, coral, or bedrock get into the mouth become jammed of the pipe and as they ascend. Water Courtesy Diving Systems International Photo Steven M. Barsky jet excavation involves the use of a highpump, a fire hose long enough to reach pressure water The nozzle should the sea bed, and a tapered nozzle. Before excavation, all possible information about the attitude and extent of a shipwreck and its cargo must be known. Once the preliminary survey has been completed, a site excavation plan is formulated and systematic layer-by-layer surveying and artifact removal can begin. Care is needed to avoid damaging the artifacts or removing them without documenting their position; archeological excavation requires tech- nique, appropriate equipment, and a great deal of patience. pingpong paddles to the application of large-diameter prop washes, more commonly referred to as deflectors or "mail boxes." Each digging procedure has its own advantages and disadvantages. excavation involves the use of a long discharge made of PVC or aluminum) and an air manifold bottom chamber (Figure 9-39). Although the size of the airlift can range anywhere from pipe (usually 9-38 stabilize the hose. The water jet creates a high-pressure stream that can cut through and remove hard-packed clays and sand, but its use as an excavating tool limited to situations where the water jet will not is dam- age artifacts or the integrity of archeological deposits before they are mapped. The venturi pump excavation technique, sometimes referred to as a Hydro-dredge, involves the use of a 10 foot (3 Excavation methods range from hand-fanning with Airlift have small holes for permitting a backward thrust of water to eliminate the recoil so that the operator can m) length of metal cm) in diameter, (7.6 to 15.2 at the suction end. A or PVC that is tube, 3 to 6 inches bent in a 90° elbow hose from a high-pressure water pump on the surface at the end of the tube. is attached to the elbow juncture When high-pressure water flows along the length of the tube, a venturi effect causes a which draws bottom sediment into the tube and out the other end, where it is discharged off the suction, site. This excavation technique is ideal in shallow water, particularly in areas that are not accessible to the large NOAA Diving Manual — October 1991 Procedures for Scientific Dives Figure 9-39 Heavy Overburden Air Lift LOW AIR PRESSURE COMPRESSOR Courtesy: October 1991— NOAA Diving Manual 7ffV&%2) NOAA (1979) and Duncan Mathewson 9-39 Section 9 needed vessels to support airlifts or a prop wash. In 9.12.3 Artifact Preservation water over 50 feet (15.2 m) deep, a similar hydraulic dredging tool called a Hydro-flo can be used by lowering it over the side and controlling it from the deck. As with underwater excavation all must be used carefully tools, hydraulic dredges damaging to avoid artifacts. horizontal discharge of the water thrust that normally is deflected downward. This away the bottom sediment. As successive overlapping holes are dug by shifting the surge of water blows position of the boat on its anchor lines, an archeologi- to using the ological tool is only the first step in enjoying the rewards of research, diving, and hard work. divers, either rule for preserving wet until submerged ever, if is to first keep them initi- should consult local experts or publications on artifact treatment (Murphy 1985). Special preservation procedures are required for iron and steel artifacts, including the use of rust and corrosion inhibitors, acid treat- ment, sealants, chemical and electrolytic reduction, and encapsulation (Murphy 1985). Some of these techniques require soaking or treatments lasting weeks or months, depending on the nature and size of the fact. arti- Non-metallic artifacts must be preserved by the In addition to preserving artifacts, engine speed properly. At it is essential that the states and the courts establish the rightful owner- very delicately from wreck sites submerged bottomlands. 50 feet (4.6 to Generally, the U.S. Government controls operations damaging the archeological It can do great damage, how- on or under navigable waters, while the states own the When authority over most finds. Non-navigable waters are in 15 to of water without integrity of the deposits. them uncertain about what to do, he or she is ship of artifacts recovered on m) artifacts proper preservation procedures can be ated. If a diver slow speeds, the prop wash can remove overburden 15.2 by accident or by design, recover valuable or historic artifacts, only to lose prop wash as an effective arche- to control the Many is use of entirely different procedures. cal picture of the artifact scatter pattern slowly emerges. The key and Salvage Rights of submerged artifacts because they do not take proper care of them. The Prop wash excavation (also known as a "blower" or "mailbox") involves a 90° elbow-shaped metal tube mounted on the transom of a vessel (Figure 9-40). The metal elbow, slightly larger in diameter than the vessel's propeller, is lowered over the propeller, where it is locked into position. With the vessel anchored off the bow and stern, the engines are started so that the pushes the vessel forward The recovery the engines are raced for too long a time. waters and their submerged beds, which gives them owned or are controlled by local gov- operating a prop wash, experience and good judgment usually privately are needed to ensure that artifacts are not lost or ernments. There are damaged. It is essential to maintain good communication between the divers on the sea bed and the operator of historical artifacts or the salvage of abandoned proper- at the throttle to ensure safe, well-controlled excavation. such activities must be aware of applicable laws, both wash can be very effective in defining the anatomy of a wreck site by determining the extent of its artifact scatter pattern. Even in deep sand, where it is impossible to record exact provenance data, artifact clusters mapped as coming from the same prop wash hole may aid in the interpretation of a site. Marine archeologists in Texas, Florida, North Carolina, and Massachusetts have successfully used In proper hands, a prop many laws affecting the recovery and these are often complex. Divers involved ty, to protect in themselves and their historical finds. 9.12.4 Significance of The archeological Shipwreck Archeology significance of shipwreck sites best determined by their physical integrity potential for providing historical and is their and cultural data that are not available elsewhere. Information that can prop washes to excavate wrecks. be gleaned from shipwreck sites includes: overseas The use of flotation gear is an inexpensive and effective method of lifting. Lift bags are available in different sizes and forms, ranging from large rubberized cultural processes; maritime life styles bags and metal tanks capable of tion of lifting several tons to cultural change; European and information regarding the evoluvessels and the development of New small plastic and rubberized nylon bags for lifting World shipbuilding techniques. 50 to 500 pounds (22.7 to 226.8 kg). Larger bags should be equipped with an air relief valve at the top. For archeological work, smaller rubberized nylon bags are distributed on a recommended; these self-venting bags have a lifting capacity of 100 pounds (45.4 kg) and are useful in all underwater operations. Lifting bags are described further in Section 8.9.1. 9-40 New World and patterns of trading patterns and maritime adaptation to Like terrestrial tial sites, random historic shipwrecks are not basis. patterning of shipwrecks is The temporal and spa- primarily a function of environmental factors, seafaring cultural traditions, maritime technology, and socio-political variables. Recent studies have demonstrated that the preservation potential for shipwrecks NOAA is highest in areas of low Diving Manual —October 1991 Procedures for Scientific Dives Figure 9-40 Prop Wash System Used for Archeological Excavation LOOSE SHELLY SAND .••U.Y. Courtesy: energy (less wave action) and/or high rates of sedi- mentation. Thus, a knowledge of oceanography and aquatic geology is important when searching for sub- merged artifacts. Shipwrecks should be considered not only as cultural resources but also as a source of valuable educational and recreational experiences. Wrecks to be explored for recreational purposes should be situin clear water less than 30 feet (9.1 m) deep, have ated a visible hull structure, boats. Heavily disturbed sites physical integrity can. how teach students cal operations to and be accessible by small in with little or no remaining certain cases, be used to perform underwater archeologi- without distorting the archeological record (Mathewson 1981). Similarly, heavily disturbed sites and those of more recent date can be developed into archeological parks to provide new underwater experiences for sport divers. By promoting such recreational dive sites, user pressure on some of the more archeologically significant sites October 1991 can be reduced. — NOAA Diving Manual 9.13 Duncan Mathewson ANIMAL CAPTURE TECHNIQUES A wide variety of devices is used by scientists and commercial fishermen to aggregate, concentrate, or confine aquatic animals. Trawls, seines, traps, grabs, and dredges have equipped ior. all been used successfully by scuba- scientists interested in Diver-scientists who will animal and gear behav- be diving near such cap- ture systems should train under simulated conditions before participating in open-water dives. Marine sci- can help to improve the design of trawls and other such equipment by evaluating its underwater entists performance, observing how animals behave in relaand then conveying this information to equipment designers. tion to the gear, In the FLARE and Hydrolab undersea programs, divers were able to observe fish near stationary traps 25 to 80 feet (7.6 to 24.4 m) below the surface for up to 8 hours per day (Figure 9-4 1) and to devise methods to alter catch rates and the species captured (High and 9-41 Section 9 Figure 9-41 Fish Trap draw the bottom closed, which seals off the fish's escape route. 9.13.3 Trawls Trawls are nets constructed like flattened cones or wind socks that are towed by one or two vessels. The net may be operated at the surface, midwater, or in across the seafloor. Specific designs vary widely, depending on the species sought. A plankton net having a 1.6 foot (0.5 may Source: NOAA (1979) be towed at speeds up to 3.5 knots (1.7 m/s), while m) a 202 foot (61.5 long pelagic trawl with an opening 40.3 by 10.5 feet (12.3 by 21.5 1 Ellis 1973). Divers from the National Marine Fisher- Service were also able to estimate accurately the ies populations of fish attracted to experimental submerged structures during studies designed to develop automated fishing platforms. 9.13.1 of use. Divers working close to an active net (one which being towed) can interfere with is cially if touch it. it is its if net considered large Any is contact does not appreciably influence tion or operation. if or direct diver its configura- Plankton nets typify small nets both and in the retain micro-organisms. sea 4.5 (61 be opened horizontally by towing each wingtip from a separate vessel, by spreading the net with a rigid wooden or metal beam, or by suspending paired otterboards in the water to shear out away from each to entangle fish when towed. on Stationary Gear Diving on stationary gear such as traps, gill nets, and some seines presents few problems. Experienced divers can dive either inside or outside the net to observe it lightweight web required to At the larger extreme, hightuna seines often are 3600 feet (1098 m) long, with inch (11.4 cm) long meshes stretching 200 feet m) or more down into the water. Gill nets are designed in physical size water at operation, espe- they swim too near to small, filter may 9.13.4 Diving purpose, materials, and methods in size, m) may knot (0.5 m/s). Figure 9-42 shows a trawl diver. Trawls other horizontally Nets Nets vary m) long m) mouth opening 9.8 foot (3 attempting to push through the meshes; webbing mesh and thread size vary, as do net length and depth, in accordance with the size and species of fish sought. Gill nets use fine twine meshes hung vertically in the water between a corkline and a leadline. The net may be suspended at the surface or below the surface or be weighted to fish just above bottom and across the expected path of migratory fish. Divers and their equipment can easily become entangled in gill net webbing, which is difficult to see in the water. animal behavior or to carry out work assignments. Divers must be alert to the entanglement hazard presented by loose diving gear, such as valve pull rods, valves, mask rims, knives, vest inflator mechanisms, and weight belt buckles. A buddy diver can usually clear the entanglement more readily than the fouled diver. Fouled divers must avoid turning or spinning around, which will entrap them in the web. It is occasionally necessary for a fouled diver to remove the tank, disengage the caught mesh, and replace the tank assembly before continuing with the task 9.14 at hand. THE USE OF ANESTHETICS IN CAPTURING AND HANDLING FISH Anesthesia has been defined as a state of reversible insensitivity of the cell, tissue, or organism. In connection with fish, the terms narcosis and anesthesia are often used interchangeably, although not all chemi- cals characterized as fish anesthetics also act as nar- 9.13.2 Seines cotics. Anesthetics Seines are similar to gill nets in that a wall of web is held open vertically in the water by the opposing forces of a corkline and leadline; however, the seine circle to confine fish within the entangle the fish. leadline through 9-42 is set in a web rather than to Seines often have rings along the which a line or cable can be pulled to should be used for surgical inter- vention or to perform other painful manipulations. Fish anesthetics have been used in conjunction with a multitude of operations, including capture, transport, tagging, artificial spawning, blood sampling, moving fish in aquaria, surgical intervention, sessions. There is and photographic a wealth of published information NOAA Diving Manual in — October 1991 Procedures for Scientific Dives Figure 9-42 Diver Checking Fish Trawl pose concerned. In the absence of applicable data, it is often advisable to conduct a preliminary experiment, may since even closely related species same anesthetic the intolerance Many not respond to same manner. Species-specific has been demonstrated with some anesthetics. in the chemicals exhibit toxic effects that are unrelated and these may be transitory Some chemicals that exhibit toxic effects long-term exposure may be satisfactory to use to their anesthetic action, or sustained. during for short-term anesthesia. The therapeutic used Photo Ian K. Workman in TR = LC 50 /EC ratio is EC = the concentration necessary to provide the desired level of anesthesia. Generally, a and of chemicals and The use on a wide variety scientific literature their applications. more TR exercised to minimize this effect. The subsequent which anesthetics have been used must take this into account, because census and other data are affected by the use of anesthetics. TR, its usefulness is somewhat The toxicity of the anesthetic be considered. A given anesthetic handle because of potential, or it limited. to may its humans may Response acute toxicity or carcinogenic toxify fish flesh, rendering gerous or fatal to eat. This to Anesthetics wild, last consideration the gills. As to the water, which is know in simplified which is where the fish will later be released where fishermen might catch it. may be important, and the stages of anesthesia can vary with the anesthetic. As mentioned above, it usu- evaluating the depth of the anesthesia. A levels of anesthesia, devised largely from the work of McFarland (1959) and Schoettger and Julin (1967), in Table 9-2. is thetic quinaldine generally cannot be used to induce the sedation stage, lent to fish and some chemicals are much more repelthan others. Other anesthetics may initially cause an increase in activity. Several anesthetics have low solubility presented must first alcohol to increase their solubility. and ly, pH, and ness, water temperature, salinity or hard- state of excitability of the fish, as well as may be inconvenient, particularly cost in water and be mixed with a carrier such as acetone or The response of a particular fish to an anesthetic depends on a number of factors, including the species size of fish, to the then taken up by the fish proceeds into anesthesia, scheme defining the dan- impor- In addition, the specific responses of fish to an anes- ally follows a series of definable stages that are useful to it is commonly Fish anesthetics are administered most by adding them must also be dangerous to tant in cases 9.14.1 of 2 or considered desirable, but since time of expo- the surrounding environment, and extreme care must be in is sure and a variety of other factors affect the validity of of anesthetics does have an impact on the monitoring of an area the concentration lethal for 50 percent of the specimens and the popular sometimes LC 50 = evaluating an anesthetic, where The need in field to premix work. Final- must be considered, especially when large field collections are concerned. on the dosage and type of anesthetic. With some anesthetics, not all of the stages mentioned in Table 9-2 are observable; for example, with quinaldine there is gen- Recovery begins removed from the anesthetic bath and untreated water, where recovery then 9.14.3 Application of Rapid immobilization. erally no definitive sedation stage. when the fish is transferred to proceeds, usually shown in Table in reverse order, through the stages in If an anesthetic high enough dosages, fish idly for may capture or handling. The to untreated sprayed 9-2. Anesthetics in is administered be immobilized rapfish is then removed water for recovery. The chemical may be the vicinity of the fish or added to a con- tainer holding the fish, or the fish may be removed to a separate bath, depending on the circumstances. Sev- 9.14.2 Selecting an Anesthetic Factors to consider in choosing an anesthetic are purpose, toxicity, repellent action, ease of application, and cost. It may be helpful to refer to the literature to choose a suitable anesthetic for the species and pur- October 1991 — NOAA Diving Manual eral anesthetics that are unsuitable for sustained anesthesia are satisfactory for rapid immobilization, provided the exposure is of short duration. Sustained Anesthesia. Under suitable conditions, fish can be sustained safely under anesthesia for several 9-43 Section 9 Table 9-2 Levels of for Fish Anesthesia Stage 1 2 Description Behavior Unanesthetized Normal Sedation Decreased reaction to visual stimuli and/or tapping on the tank; opercular rate reduced; locomotor activity reduced; color usually darker. Partial loss of equilibrium Fish has difficulty Total loss of equilibrium 3 for the species. remaining in normal swimming position; opercular rate usually higher; swimming disrupted. Plane —Fish usually on side or back; can 1 still propel itself; responds to tap on tank or other vibrations; opercular rate rapid. Plane 2 — Locomotion ceases; fins may still move but ineffectively; responds to of peduncle or tail; opercular rate decreased. squeeze 4 Does not respond Loss of reflex This to peduncle squeeze; opercular rate slow — often may be erratic. the surgical level. Operculum ceases Respiratory collapse 5 is minutes unless fish to move; cardiac arrest (death) revived in will occur within one to several untreated water. Source; days. Choosing the proper anesthetic with regard to toxicity is and stability is Before the anesthetic critical. administered, the fish should be starved for 24 to 48 hours to prevent regurgitation of food. To perform surgery on captured fish, it is head should be immersed in an anesthetic bath For longer term surgery, more sophisticated procedures are required. One successful system employs two water baths, one containing untreated water and the other the anesthetic solution. The level of anesthesia can be controlled carefully by selectively recirculating water from the baths over the fish's gills. Steps should be taken to maintain the oxygen content near the saturation level and the ammonia concentration at the minimal level. Filtration may be required to maintain water quality (Klontz and Smith 1968). Recovery. To revive fish in deep anesthesia, it may be necessary to move them gently to and fro in their normal swimming position. It is helpful to direct a gentle stream of water toward the fish's mouth, which for the duration of the procedure. provides a low-velocity current over the gills. It is not advisable to use a strong current or to insert a hose directly into the mouth because this (Houston et al. in fish after anesthe- 1971). During this post-treatment period, additional stress may result in mortality and simplest to then be placed in a trough or other restraining device, its sia (1979) should therefore be minimized. anesthetize the fish to the surgical level; the fish should and than a week, have been observed NOAA may cause, rather than alleviate, hypoxia. The water in which the fish is NOTE Anesthetics administered to food fish must be approved by the Food and Drug Administration, and those using anesthetics are advised to be thoroughly familiar with all pertinent regulations. Violations of these regulations carry severe penalties. Tidepools and Ponds. Anesthetics are useful when collecting fish in tidepools. The water volume in the pool must first be estimated, and then the desired dose of anesthetic the fish is are untreated water as quickly as possible. to collect fish As calculated and added to the pool. become immobilized, they It removed is from tidepools as the tide because a moderate amount of surge to desirable is rising, in the pool helps to flush anesthetized fish out of crevices, and diluting the pool water with incoming water will prevent the killing of specimens that are not going to be collected. With the proper anesthetic and dose, the mortality of being revived must be of good quality. uncollected specimens can be reduced to a negligible Some species recovering from certain anesthetics may undergo violent, uncontrolled swimming move- level ments, and steps must be taken in such a situation to can be collected with anesthetics. Quinaldine (10-20%) prevent self-inflicted injuries. For example, this used widely for this purpose. One-half to 1.05 quart (0.5 to 1 L) of the solution is generally used for each usually the case when is the yellowtail Seriola dorsalia recovers from quinaldine anesthesia. Various physiological changes, 9-44 some of which may persist for more (Gibson 1967, Moring 1970). Reef and Shore. Many species of reef and shore collection. Species susceptibility is fish is highly variable. For example, angelfish and butterflyfish are highly NOAA Diving Manual — October 1991 Procedures for Scientific Dives Figure 9-43 Slurp Gun Used to Collect Small Fish susceptible, squirrelfish are moderately susceptible, and moray The eels are highly resistant. effectiveness of the anesthetic also varies with the physical situation and experience of the collector. at least somewhat repellent, and as well as the skill Most anesthetics are the fish usually need to be in a situation, e.g., in small caves, short crevices, or under rocks, where they can be confined within the anesthetic's influence for several The anesthetic seconds. squeeze bottle is usually dispensed from a in sufficient quantity to immobilize or partially immobilize tion. in The fish specimens on the first applica- can then be collected with a hand net the case of small specimens, with a gun (Figure 9-43). A power syringe is or, manual "slurp" permits the diver to deliver the anesthetic at closer range to more species of fish than can be done using a this delivery more expensive anesthetics system may make the practical to use for collecting. Sedentary specimens can sometimes be collected by slowly trickling a light anesthetic dose toward them. Fish in some non-repellent anesthetics fish to ensure that the emerges. system for collecting garden eels of the Taenioconger species, which were previously difficult is bilized small sharks and ratfish with this technique, while Harvey (1986) has used it A piece of clear plastic, 6.6 feet (2 m) placed over the area of the eels' burrows and moray eels Coral heads. It usually is advantageous to enclose coral heads with a loose-fitting net before applying the anesthetic. Some hawkfish reside species of fish such as wrasse and in coral at night and can be collected easily at that time with the aid of anesthetics. Large-scale collections. lect fish One technique used over a large portion of a reef is to col- to enclose the desired area with a seine and to administer a large enough quantity of anesthetic to immobilize the enclosed population rapidly. Divers should work as a team to recover the fish because of the danger of the divers becoming entangled Handling large tured by hook in the net. Procedures to free fish. may be in ing advance. Sharks or other large cap- fish immobilized by spraying a strong anesthetic solution directly over their 1 weighted down along the edges with sand. Approximately 1.05 quart (1 L) of 13 percent quinaldine to collect and jacks. Aquarium have developed a successful square, much promise. Harvey, Denney, Marliave, and Bruecker (1986) have successfully immo- entangled divers should be planned Scientists at the Scripps to collect. dart gun, shows downstream burrows are often difficult to collect with anesthetics because the burrows are so deep that the fish cannot be reached by discharging anesthetic from a squeeze bottle. Attaching tubing, such as a piece of aquarium air line, to the bottle may provide an adequate extension to reach into the burrow. The anesthetic should have repellent qualities that will cause the fish to emerge, because otherwise the fish might become anesthetized in the burrow and remain out of range. A noxious chemical can be added to National Geographic Society available that allows oral anes- thetics to be delivered through a probe. This device squeeze bottle, and Photo gills before bring- them aboard. Gilbert and Wood (1957) used 000-ppm a tricaine solution successfully in this situation. Transportation. Anesthetics have been used, with solution in ethanol conflicting results, to immobilize fish during transit. area The is applied under the plastic. The undisturbed for 20 minutes, after which the sedated and immobilized eels are gathered is then left gently by hand. colony may A single collection in a well-developed more than 20 eels. This technique can other burrowing species, although the yield be applied to dosage and time of exposure may have to be varied. Fish can also be anesthetized by injection. Although effectiveness of this approach depends on a of fish, temperature, time in transit, preconditioning of fish, and water quality. Since most fish can be transported successfully without the use of anesthetics, information on the appropriateness of using anes- thetics during transit should be obtained earlier attempts at collecting fish with projectile- literature or mounted syringes were procedure. limited in their success, a recently developed technique utilizing Saffan®, a veterinary anesthetic, administered by a laser-sighted underwater October 1991 — NOAA Diving Manual num- ber of factors, including the type of anesthetic, species from the by experimentation before attempting the Summary. The use of anesthetics as collecting agents aquarium fish is controversial, primarily because for 9-45 Section 9 Conventional methods of capture such as seining, of concern about the delayed toxicity of the anesthetic A agents. survey of the literature indicates that, in the and long-lining are not appropriate trawling, majority of species experimentally subjected to repeated turing fish around coral reefs, and a anesthetization, delayed mortality techniques must be used instead. negligible. Pro- is number An for cap- of special array of suction fessional aquarists at Scripps Aquarium, Steinhart devices called slurp guns has been on the market for Aquarium, and other have also demonstrated some that many institutions other species that have not yet been subjected can be collected safely and to formal experimentation powered either by rubber tubing, diver using a slurp gun (Figure 9-43) pulls the trigger, drawing the plunger back and sucking a large volume handled without significant mortality. Most aquatic time. These are springs, or other means. After cornering a fish, the biologists concerned with collecting of water in through a small opening and thus pulling agree that judiciously applied anesthetics are useful small fish (1-3 inches (2.54-7.6 cm)) into the gun. However, the misuse of these chemicals, especially if widespread, can be very harmful. For example, the practice of using sodium cyanide to collect aquarium fish, which is sometimes done in under- fish are collecting agents. developed countries, human is ill-advised and other organisms among readied for another shot. is to the fish, in a hole, to and the need capture to corner the fish, usually it. Glass or plastic bottles also in the vicinity. Recommendations. Tricaine® (MS-222) is a highly powder that is easy to proved to be a successful anesthetic in a wide variety of applications under a broad range of conditions in both fresh water and seawater, and there use. It has an extensive literature on its properties and use. Tricaine® is a good choice where sustained sedation or surgical-level anesthesia is required, but high cost of captured, the necessity for the diver to be very close the fish soluble and virtually odorless The disadvantages slurp guns are: the small size of the fish that can be in and has resulted deaths, as well as high mortality gun The then moved into a holding container, and the small fish; however, fish may be may used to entrap react to the pressure wave created by the moving jar and swim away. All bottles must be flooded fully with water before being submerged. A better technique than the bottle is the use of a piece of plastic core liner or plastic tube with a screen across one end, which can be slipped over fish is generally precludes its It is of low solubility in water and is generally withdrawn and placed As discussed hol before use in water. Quinaldine is not useful where the goal, and is it should not be used for major surgery or other painful procedures because it is a poor pain killer. Liquid quinaldine can be converted readily to a water-soluble greatly facilitates its use. When salt, which a mixture of the salt combines the desirable properties of both chemicals and is and tricaine is prepared in proper proportions, it effective at lower doses than either alone. Propoxate® and its analog Etomidate® are two relatively new and highly potent fish anesthetics that have potential as anesthetics for fish collection. Table 9-3 shows the commonly used fish mended dosages. anesthetics, including their recom- if in may may be to attract fish, or divers herd fish into the net. Once entangled, fish dissolved in acetone, ethyl alcohol, or isopropyl alco- sedation-level anesthesia Divers on the bottom can also use small Animals such as sea urchins may be broken easily. nets. up and placed near the net use as a collecting agent. Quinaldine has been used widely to collect or handle fish. more gill bags or wire cages. earlier, fish traps may also be effective baited appropriately and placed at a proper point either on the bottom or in the water column. Divers can then remove fish from the trap and rebait it while it remains on the bottom. Deepwater can be caught on hook and fish line and reeled to 60 to 100 feet (18.3 to 30.1 m), where divers can insert hypodermic needles into those with swim bladders and then decompress the fish. There is an 80 percent recovery rate on many species of rock fish when this technique bottom. The fish is used. A dip net fastened to the is useful in collecting fish near the may be pinned against a rock or sand end of a pole spear bottom, taken out of the net, and placed in an appropriate container; again, needle decompression may be helpful. Many larger may be fish such as rays, skates, or harmless caught either by hand or by a loop of heavy monofilament line on the end of a pole (such as a snake stick). Electric fish and rays should not be taken sharks 9.14.4 Diver-Operated Devices The capture Some of live fish poses no special problems for and maintain discrete and roam widely. Diurnal variations may also cause the fish to change with metal poles or rods because of the shock potential regions, while others live in schools (see Section 12.4). their habitats during a 24-hour period. gloves. divers. 9-46 fish are territorial Invertebrates A may be collected by divers wearing pry bar, screwdriver, putty knife, or diving NOAA Diving Manual — October 1991 Procedures for Scientific Dives Table 9-3 Fish Anesthetics Dosage (varies Common with species, Anesthetic Benzocaine* Qualities temperature, Powder, 25-100 mg/L etc.) soluble Use Remarks References Immobilization, Widely used Caldarelli deep anesthesia in in medicine; safe ethanol and effective with fish. Low potency; Chloral Solid, soluble, hydrate inexpensive 1-4 g/L Sedation not widely used. McFarland 1959 McFarland 1960 Bell Cresols mix Liquid; 50:50 with 20-40 mg/L for Collection 1986 human Cresols have 1967 Howland 1969 undesirable immobilization acetone to toxic effects; facilitate para-cresol solution. the most effec- is tive isomer. mg/L High potency; Amend analog of Limsowan propylene Propoxate®; 1983 glycol. longer seda- Make Etomidate 5 1 solution percent 2-10 Immobilization in et al. 1982 et al. tion times and safer than quinaldine and MS-222 mixture. Methylpentynol Liquid. 0.5-2 ml/L Sedation or deep Widely used but Bell (Oblivon®, moderately 1500-8000 mg/L anesthesia less desirable Klontz and Smith Dormison ') soluble Phenoxyethanol Oily liquid 0.1-1 ml/L than other 1968 anesthetics; low potency. Howland and Schoettger 1969 Used Klontz with salmonids. and Smith 1968 Bell 1967 Collection, Good Thienpoint and immobilization agent. Immobilization (2-phenoxye- frequently thanol) Propoxate® Crystalline; (McNeil R7464) 1-4 mg/L soluble 1967 collecting Niemegeers 1965 Howland 1969 Quinaldine (Practical grade) Widely used No soluble with for collection, state; difficulty; dis- immobilization analgesic; Oily liquid, solve October 1991 in 5-70 ml/L 10-50 sedation poor efficacy varies percent acetone, widely with ethanol, or species and water isopropyl alcohol characteristics; to facilitate long exposures solution. toxic. — NOAA Diving Manual Schoettger and 1969 Locke 1969 Moring 1970 Gibson 1967 Howland 1969 Julin 9-47 Section 9 Table 9-3 (Continued) Dosage (varies Common with species, Anesthetic Qualities temperature, Quinaldine Crystalline 15-70 sulfate solid (QdS0 4 Remarks References Collection, Prepared from Allen immobilization liquid quinaldine 1973 and has same Gilderhus, Berger, properties. Sills, Use etc.) mg/L ) and Sills Harman 1973a Rotenone® Powder or emul- 0.5 ppm sion Ichthyocide; Used occasionally fish used water ponds. for collecting to salvage from fresh- Limited use seawater Tate, Moen, Severson 1965 in for live collecting. Sodium cyanide Solid DO NOT USE Used in Philippines Styrylpy- White powder; ridine (4- soluble 20-50 mg/L Dangerous to humans; causes high and elsewhere mortality for collecting fish. Immobilization, Not widely used Klontz and Smith deep anesthesia but a successful 1968 in anesthetic. styrylpyridine) Tricaine® (MS-222, tri- caine meth- mg/L White crystalline 15-40 powder; readily sedation soluble 40-100 mg/L for for deep anesthesia 100-1000 mg/L anesulfonate) Immobilization, Expense bars deep anesthesia; most widely used use used extensively anesthetic in its for collecting; Klontz and Smith 1968 Bell 1967 surgery, fish handling, for rapid transport. immobilization Urethane Carcinogenic DO NOT USE Immobilization, Carcinogenic. Wood 1956 deep anesthesia Mixtures of Powder, readily Various, e.g., 10:20 Immobilization, Combines MS-222 and soluble ppm QdS0 4 MS-222 equals 25 ppm QdS0 4 80-100 ppm MS-222 deep anesthesia properties of each Sills, anesthetic; 1973b QdS0 4 : or desirable Gilderhus, Berger, Harman combination can be used in lower concentration than either anesthetic alone. Source: Donald Wilkie 9-48 NOAA Diving Manual — October 1991 Procedures for Scientific Dives knife may be useful their substrate. may be placed bags. Vials and in removing some specimens from Delicate animals such as nudibranches in separate plastic jars, vials, or ziplock jars should be open at the beginning of either a scoop, which has a line inscribed given volume, or a cylinder aluminum, made showing a of plastic, stainless, or other material that can be forced into the soft substrate. A simple cake server or spatula can the dive but be completely filled with water before be inserted from the side to provide a closure as the being returned to the surface. core of sediment Traps are effective for crabs, lobsters, and, occasionally, octopus. Nylon net bags are more easily used for collecting than bottles or plastic bags. Animals that are neutrally buoyant will float out of the bottle or plastic bag when it is reopened to add another specimen. Animals that live in the upper few centimeters of sediment or sandy bottom may be sampled by using October 1991 — NOAA Diving Manual is withdrawn from the bottom. The diameter of the cylinder should be such that it fits snugly over the mouth of the collecting bottle so the material can be forced into a labeled jar. Nylon or other plastic screens can be obtained in a mesh sizes. These may be tied over ends of plastic tubes as a sieve or be sewn into a bag to be used variety of to hold sediment samples. 9-49 ( Page- SECTION DIVING 10 10.0 General UNDER 10.1 Geographic Regions SPECIAL CONDITIONS 10-1 Northeast Coast 10-1 10.1.2 Mid-Atlantic Coast 10-2 10.1.3 Southeast Coast 10-3 10.1.4 10-3 10.1.7 Gulf of Mexico Northwest Coast Mid-Pacific Coast Southwest Coast 10.1.8 Central Pacific Ocean 10-6 10.1.9 Arctic and Antarctic 10-6 10.1.10 Tropics 10-6 10. 1.1 Diving 10.1.5 10.1.6 10.2 10.3 10.4 10.5 10-1 10.1.1 1 in Marine Sanctuaries or Underwater Parks From Shore 10.2.1 Through Surf 10.2.2 Through Surf on a Rocky Shore 10.2.3 Through Shore Currents 10.2.4 From a Coral Reef Diving From a Stationary Platform Diving From a Small Boat 10.4.1 Entering the Water 10.4.2 Exiting the Water Fresh Water Diving Diving 10-3 10-4 10-5 10-7 10-7 10-7 10-9 10-9 10-10 10-10 10-1 1 10-12 10-12 10-13 10.5.1 Great Lakes 10-13 10.5.2 Inland Lakes 10-14 10.5.3 Quarries 10-14 10-14 10.9 Open-Ocean Diving Cave Diving Cold-Water Diving Diving Under Ice 10.10 Kelp Diving 10-22 10.11 Wreck 10-23 10.12 Diving at High Elevations 10.6 10.7 10.8 10-17 10-19 10-21 Diving 10-24 10.12.1 Altitude Diving Tables Currently in Use 10-24 10.12.2 10-25 10.12.3 Comparison of Existing Tables Recommendations for Altitude Diving 10.12.4 Calculations For Diving at Altitude 10-25 10.12.5 Correction of Depth Gauges 10-26 10.12.6 Hypoxia During Altitude Diving 10-27 10.13 Night Diving 10.14 Diving 10-25 10-27 Dams and Reservoirs 10-28 10.14.1 Diving at Dams 10-28 10.14.2 Diving at Water Withdrawal and Pumping Sites in 10.15 River Diving 10.16 Diving From 10-30 10-31 a Ship 10-32 10.16.1 Personnel 10-32 10.16.2 Use and Storage of Diving and Related Equipment 10-32 10.16.3 Safety Considerations 10-33 10.16.4 Using Surface-Supplied Equipment 10-33 10.16.5 While Underway 10-33 ( DIVING UNDER SPECIAL CONDITIONS 10.0 The GENERAL ber. characteristics of underwater environments, such and type of marine life, vary significantly from geographic region to region and influence the amount and type of diving work that can be carried out under water. The following paragraphs describe the diving conditions most typical of U.S. as temperature, visibility, coastal and other areas and provide an overview of the visibility increases. Water temperatures near the surface during the spring and summer, when a substantial thermocline exists, range from 50 to 70°F (10 to 21 °C). Temperatures at 100 feet (30.5 m) range from 48 to 54 °F (9 to 12'C). During the winter months, the temperature of the water column diving characteristics of these regions. the New England temperature decreases and underwater As one progresses north along coast, water is essentially homogeneous, with temperatures reaching as low as 28.5 °F (-2°C). Subzero air temperatures WARNING and strong winds cause wind volume dry Diving in an Unfamiliar Region, Information About Local Conditions Should Be Obtained From Divers Who Are Familiar With Local Waters. A Checkout Dive Should Be Made With a Diver Familiar With the Area When suits low Wet suits and variablehave become standard for winter diving in the Northeast (see Section 5.4). Underwater visibility is primarily a function of sea and vertical turbulence in the water column. In the Northeast, horizontal visibility of 50 to 80 feet state (15 to 24.4 m) may occur occasionally throughout the year, usually in connection with 10.1 chill factors as as -70 to -80 °F (-57 to -62 °C). GEOGRAPHIC REGIONS For purposes of discussion, the coastal regions are classified as shown on the following table. The principal characteristics of calm a land mass or to estuaries or harbors each region are described in the following sections of this chapter. seas. is Proximity to associated with a because the load of suspended decrease in visibility material in the runoff from the land mass and the processes associated with the mixing of fresh and salt water greatly elevate turbidity. During the summer, biologically caused 'red tide' conditions lowering visibility to less than 1 may occur, foot (0.3 m). Coastal waters within the Gulf of Maine have an average range Area Encompassed Region in visibility of visibility Rhode in Northeast Coast Maine Mid-Atlantic Coast Southeast Coast Rhode Island to Cape Hatteras Cape Hatteras to Florida Gulf of Mexico Coast West Coast Northwest Coast Subarctic Alaska to Oregon Mid-Pacific Coast Northern and Central California (see Section Southwest Coast Point Conception to the extend as to Texas Northern Baja Peninsula Central Pacific Ocean Hawaiian and Leeward Islands and Antarctic Caribbean and Florida Keys Polar Arctic Tropics Cape Cod averages 10 to 15 feet (3.0 to 4.6 m). Island of Florida to 25 to 35 feet (7.6 to 10.7 m), while waters south of Several species of brown algae comprise the large kelp of the New England coast. Unlike the kelp of California, these kelp do not form surface canopies 10.11). much New England kelp occasionally m) off the hard ocean bottom and, although they look impenetrable, they do as 25 feet (7.6 not in fact present a significant entanglement hazard. Generally, these algal plants are sparsely distributed and seldom project more than 6 from the bottom. to 8 feet (1.8 to 2.4 m) New England coast are primarily and generally do not exceed 0.5 knot (0.25 m/s). Faster currents may be encountered in channels and in river mouths. Divers should be cauCurrents along the 10.1.1 Northeast Coast Diving in northeastern waters tidal is an exciting and chilling experience. Generally, the best diving condi- tions in terms of water temperature, sea state, and visibility occur from June through Octo- underwater October 1991 — NOAA Diving Manual in origin tious in the waters off the cially when diving in New England coast, espe- strong currents and cold water, 10-1 Section 10 because of the potential for overexertion. The surf in Water temperatures on the surface range during the modest compared with the surf in California, but it is especially hazardous along rocky, precipitous coastlines such as the coast of Maine. Shortperiod waves as high as 5 to 10 feet (1.5 to 3.0 m) can create very rough and turbulent sea states along these coasts and can push divers into barnacle-covered rocks. summer months from 72-75 "F (22-24 °C) and from this region is Hazardous marine animals. Relatively few species of and invertebrates fish in the New waters off the England coast are potentially harmful to divers. Sharks of several species are occasionally seen, but they are generally not harmful to divers (see Section 12.3.1). and blue shark; occasionally, the shark filter-feeding basking mistakenly identified as a dangerous shark. is The torpedo ray (electric ray) (see Figure 12-19), cownosed ray, and stingray are found off southern New England (Cape Cod and south). Documented divershark or diver-ray encounters are relatively rare along the New England coast. The most bothersome fish in this region is the goose- which may weigh as much as 50 pounds (23 kg) and grow to 4 feet (1.2 m) in total length. It is the habit fish, of the goosefish to lie partially buried on the ocean floor waiting for unsuspecting 'meals' to pass by. This fish is approximately one-half head and mouth and one-half startle tail. The sight of a goosefish another bottom-oriented creature that by fishermen and divers for when bothered. The its is The to many fishermen have wolffish is highly respected strength and aggressive- wolffish's six large canine tusks are capable of inflicting considerable discovered when damage, as trying to boat is The green sea urchin, which has many stout spines that can easily puncture a rubber wet suit, can also injure divers. Unless the tip of the urchin's spine surgically trapped every summer. This pool or summer water on the entire Tidal and wind movement of contains the cell coldest eastern continental shelf. cold bottom water can cause a significant and sudden change tom temperature of the water A off the New removed from the diver's flesh, it will is cause may last for months or found in very dense concentrations on hard substrates to depths of 50 to 60 feet (15.2 to 18.3 m). a painful 'lump' under the skin that The green sea urchin is in the bot- Jersey coast. chief characteristic of the mid-Atlantic water summer the thermocline. The rapid decrease in temperature at the thermocline may cause column in the is an unsuspecting and unprepared diver enough discomfort to abort the dive. Plankton gathered at the ther- mocline also can decrease the light so drastically that artificial lights occasionally are needed in water depths beyond 70 feet (21.3 m). In the Cape Hatteras area, eddies from the Gulf Stream often bring warm clear water to the coast. Bottom temperatures are warmest in October and early November after the cold bottom water mixes with the warmer upper layers. Winter temperatures in the northern range drop as low as 35 °F (2°C) near shore and are relatively homogeneous throughout the water column, with slightly warmer temperatures on the bottom. Underwater October, when visibility it is common is best during Septemberto be able to see for tances of up to 60 feet (18.3 m). Many dis- of the inshore waters of the northern area and the waters near the major estuaries, such as the Hudson and Chesapeake, have poor visibility throughout most of the year. Visibility can range from m) to 15 feet (4.6 in these areas, but improves with distance offshore. Tides this species. years. mid-Atlantic Bight (Montauk Point, N.Y. to Cape May, N.J.), a large bottom 'pool' of cold winter water even a seasoned diver, but these fish do not generally attack unless they are provoked. ness enough is proximity to the shore, and general location. In the These hammerhead, are the mako, dusky, tiger, great white, 40-60 °F (4-1 6 °C) on the bottom, depending on depth, large changes in visibility for as (4.8 km) much may cause as 3 miles offshore near bays and rivers. Tides and currents. Strong tidal currents can be expected in the Chesapeake Bay, parts of the New York Bight, off the outer banks of North Carolina, and in Long Island Sound. Diving especially hazardous of low visibility and if is in these areas can be the diver becomes lost because swept away from the planned exit area. Waves. Long-period open ocean waves in the mid- Atlantic are generally not hazardous to divers, although 10.1.2 Mid-Atlantic Waters Coast characterized by low visibility and cold bottom temperatures. flat Bottom topography generally consists of sand clay or gravel and occasional low-relief rocky outcroppings. York-New 10-2 Wrecks are found frequently Jersey coasts and off squalls can cause quick 'chops' that may be a problem. Waves pose the greatest danger to divers attempting to dive off the end of a rock jetty in a summer off the coasts of the mid-Atlantic states are off the Cape Hatteras. New end of a by a wave. The surf in these waters is generally moderate, and most beaches are composed of sand rather than moderate to heavy surf; divers too close to the jetty can be picked up and thrown NOAA into the rocks Diving Manual — October 1991 Diving Under Special Conditions which makes entry from the shore relatively easy rock, there are often sharp boundaries between water masses for divers. in the Although sharks are numerous off the coasts of the mid-Atlantic states, there have been few diver-shark encounters. However, divers carrying speared fish ties. have been molested by sharks, and divers are therefore advised to carry fish on a long especially in line, murky m) above (0.3-0.6 the bottom, and if 1-2 feet hug the divers bot- tom contours they can work without interference from the current. However, the tending boat operator must be aware of the current differential and must establish a reference for the diver's position to prevent the boat water. As water column that have different current veloci- The current generally slows about in the Northeast, the goosefish is probably the most troublesome marine creature for divers. Divers swimming close to the bottom to see their way in murky water often inadvertently place a hand or foot in the mouth of a goosefish lying camouflaged on area's from being carried away from the dive site. Dropping a well-anchored buoy over the side at the beginning of the dive is a good means of establishing such a refer- ence. Carefully monitoring the bubbles of the diver is Some means of extremely important type of diving. in this the bottom and thus run the risk of being bitten. Sting- diver recall must be established in case the crew on the abundant in estuaries, especially during the summers in the Chesapeake Bay, that maximum protection against them is necessary. surface boat loses sight of the diver's position (see ing jellyfish are so Section 14.2.2). 10.1.4 Gulf of 10.1.3 Southeast Coast For the most part, the waters off the coasts of the southeastern states are tropical. Warm and can reach as high as 75 prevail 27 °C) during the summer months. temperatures to 80° In the F (24 to most north- ern portions of this region of Georgia, South Carolina, Mexico Water temperature in the Gulf of Mexico drops to a low of about 56 °F (13°C) during the winter months and rises to about 86° F (30°C) in the summer. Visibility offshore is generally good to excellent and may even exceed 100 feet (30.1 m) around some reefs. Underwater visibility near shore near river outfalls, in is poor, particularly in areas bays and estuaries, and off some and southern North Carolina, less tropical conditions prevail. Water temperature during the summer in this beaches. Occasionally, a mass of clear offshore water about 70°F (21 °C). In the area just south of Cape Hatteras, the Gulf Stream passes close to land, ity area causing the water temperature to be than it warmer near shore During the winter, water temthe southernmost areas remains 65 to 70 °F in (18 to 21 °C); in the more northerly waters, however, temperatures drop as low as 50 °F (10°C). In the tropi- and subtropical waters of the Southeast, there are a vast up to inshore and increase the near-shore visibil- 75 feet (22.9 number Mobile, should be of concern to divers. At times, strong still the gulf are generally negligible but may occur around offshore oil platforms, and knowledge must be relied on in this situation. Weather conditions and running seas are unpredictcurrents local able in the gulf. Unforecasted storms with 6- to 12-foot good is (1.8 to 3.6 m) seas have curtailed diving operations in to excellent in this region of the the offshore areas; closer to shore, however, 25 to 30 feet (7.6 to 9.1 m), and in it country in the past. drops to harbors and bays, it can be poor. Farther north, both offshore and nearshore drops drastically and averages 20 to 25 feet 10.1.5 Northwest Coast Diving activities in the northwest take place off the coast of subarctic Alaska and extend to areas offshore (6.1 to 7.6 m). When in regions southeast of in of different species of marine animals. Visibility in southern waters visibility m) Alabama. Currents to the south. is perature cal may move is diving at the boundary of major oceanic cur- Gulf Stream, special care from Oregon. Water temperatures in subarctic Alaska eddies that occasionally spin off the main mass of 3°C) during the winter months and average 45 to 50° F (7 to 10°C) during the summer. Divers in these waters must give serious moving water. Extra precautions also must be taken consideration to their choice of diving dress so that because of the meandering nature of the current's edge; dive duration rent systems such as the must be exercised because of the episodic turbulent relatively quiet water near the change to edge may suddenly water with a current velocity of more. Dives in 1 knot or boundary regions must be planned to anticipate high current speeds, and appropriate surface support must be provided. October 1991 — NOAA As the diver descends, Diving Manual range from 34 to 38 °F is to not affected by the cold. During the winter, temperature so that (l some bays, and wind conditions may combine and near-shore waters freeze inlets, over. Visibility in Alaskan waters varies drastically from place to place and from time to time. The best visibility 10-3 Section 10 occurs along coastlines and in the Aleutians, where may it range, at best, from 40 to 80 feet (12.2 to 24.4 m). bays and Visibility in the waters of straits is usually throughout the year. Visibility usually from 5 to 25 feet beaches and from (1.5 to 7.6 At any location, visibility may become temporarily limited by storms or phytoplank- Puget Sound waters. ton blooms. Late each spring in southeast Alaska, the dictable. This visibility in the the water upper 30 to 40 feet m) (9.1 to 12.2 of column may be near zero because of phyto- plankton, but below that layer the water clear (visibility of 40 feet (12.2 this deep, clear water is m) may be very or more). Although Currents very low may in certain areas is is low, ranging in coastal 70 feet (0 to 21.3 m) to 15 to 30 feet (4.6 to 9.1 m). m) water near in protected be strong and unpre- especially true in river diving, visibility where can cause orientation problems. Logs, stumps, wrecked automobiles, fishing hooks and lines, and other bottom trash also pose distinct dangers divers working in Alaskan rivers (see Section 10.15). to often dark because of the shading effect of the overriding low-visibility water, there is usually sufficient ambient light to work. 10.1.6 Mid-Pacific Currents and tides are strong and unpredictable in The mid-Pacific Coast coastal region includes the waters subarctic Alaskan waters. Tides are extremely heavy of Northern and Central California. and can cause currents as high as 10 knots in narrows. Currents also vary significantly and have been observed north, the best diving conditions in terms of underwa- to change direction within a period of minutes. Much of the Alaskan coastline is steep and rocky; many areas are too steep to allow divers either to enter ter visibility as well as From San Francisco water temperatures generally occur from June through September. From San Francisco south to Point Conception, good diving conditions may continue through December. From San Francisco summer temperatures and exit points must be careMost sections of coastline are accessible only from boats. During times of heavy seas or swells, many near-shore diving locations become 48 to 56 °F (9 to 13°C). Fall and early winter temperatures vary from 52 to 60 "F (11 to 16 °C), and late completely unworkable. winter and spring temperatures from 45 to 54 °F (7 to or leave the water. Entry fully selected before a dive. Alaskan waters harbor relatively few hazardous marine A 13 °C). north to the Oregon border, generally range from about thermocline generally exists at depths from m) during organisms. Those that cause divers the most trouble 20 are the urchins, barnacles, and jellyfish, with their summer. The difference and stings. Dense beds of floating kelp can cause some problems for divers, especially during surface swimming. Sharks peratures during this period ranges between 2 and and whales are common but are rarely, if ever, seen under water and generally do not influence diving activity in any way. The presence of killer whales, which are common, is an exception to this general rule. Although no known diver/killer whale encounters have taken place in Alaska, general caution should waters. potential to cause punctures, abrasions, keep divers out of the water to if these animals are be near. Steller sea lions are very abundant known some in areas of Alaska; although there are no reports that these animals have ever fornia sea lions harmed sea lions are large, fast, divers, they divers in Alaska, Cali- have been known to injure and agile divers. Because and are attracted to can disrupt an otherwise routine dive. In addition to being a psychological distraction, the activity 40 feet to (-17 and gloves, Underwater wet suit, a necessity and 5°F including hood, when diving in these varies quite drastically through- summer Oregon border, to winter. late spring m), increasing to 30 feet (9.1 m) in the fall. From Santa Cruz north to San Francisco, visibility ranges from 5 to 15 feet (1.5 to 4.6 m) in the early spring and summer, 10 to 25 feet (3.0 to 7.6 m) in late summer and 6.1 fall, early spring. 10-4 late spring surface and bottom tem- From Fort Bragg and summer underwater visibility ranges between 10 and 15 feet (3.0 and 4.6 m). In the late summer and fall, underwater visibility increases to about 15 to 25 feet (4.6 to 7.6 m). During to the winter and early spring, visibility decreases to 10 feet (0 to 3.0 m). South of Fort Bragg down to San Francisco, visibility ranges from 10 to 20 feet (3.0 to to the iments and a reduction of Farther south, in the waters off Washington and Oregon, water temperatures range from about 43 to 60 °F (6 to 16 °C) over the year in protected areas such as Puget Sound. In open ocean waters, depending on the water masses moving through, temperatures ranging from 40 to 60 °F (4 to 16 °C) may be encountered is in full visibility out the area from of sea lions often causes serious roiling of bottom sedvisibility. A and -15°C). boots, 12.2 to (6.1 and visibility to 10 feet (0 to 3.0 From m) during the winter and Point Conception to Santa Cruz, ranges from 15 to 25 feet (4.6 to 7.6 m) during the late spring and 50 feet (4.6 to 15.2 m) summer and from 15 to and may occasionally in the fall reach 100 feet (30.5 m) near Carmel Bay. During winter and early spring, one can expect visibility to extend 5 to 20 feet (1.5 to 6.1 m). The main factors NOAA Diving Manual — October 1991 Diving Under Special Conditions controlling underwater visibility in this area are the 60's (10 to huge plankton bloom, which occurs during upwelling in the spring and summer, and the dirty water condi- deal of mixing in the upper layers and discrete temper- caused by rough seas and river runoffs during the thermocline at 40- to 60-foot (12.2 to 18.3 m) depths tions 16°C). In fall and winter there a great is ature zones do not exist. However, a distinct summer winter and early spring. causes a sharp temperature drop that should be con- Three species of surface-canopy-forming brown kelp occur on the Pacific coast. From Monterey algae sidered — — dominant kelp north, the is the bull kelp. This particu- forms large beds but, because of lar species its struc- same entanglement hazard ture, does not pose the to dive planning. in Horizontal visibility under water ranges from 5 to 10 feet (1.5-3.0 as much islands. The North of Point Conception, surf conditions are probably the most important consideration in planning a m) of the mainland coast to m) around the offshore best visibility conditions occur in the late summer and divers as the giant kelp (see Section 10.10). m) along much as 100 feet (30.5 fall. underwater During spring and early summer, is generally less (30-50 feet visibility (9.1-15.2 m)) around the islands, at least in part because can expect most areas even on calm days, and on rough days it is not uncommon to see waves 10 feet (3.0 m) or more high. Divers should always scout the proposed dive of prevailing overcasts and heavy fogs. Winter storm area before going into the water to determine the safest material from storm drains and river mouths. 2- to 3-foot (0.6 to 0.9 dive. Divers surf in conditions and rain runoff can reduce the visibility to zero for miles along the mainland coast, because the prevailing long-shore current distributes suspended Shore conditions along the mainland coast of south- area of entry and, in case conditions change, to choose ern California range from sand beaches to high pali- alternate exit sites (see Section 10.2.1). Long-shore currents and tidal currents are and tend nia. On to be severe in common northern and central Califor- very windy days, divers should watch for strong currents around headlands, off rocky shores, and near common sade cliffs. Ocean access from these areas is often impossible, and a careful check of charts and maps, supplemented by preliminary site a recommended before visit, is initiating a dive. highly The offshore along beaches islands generally are accessible to divers only by boat. Hazardous marine animals. As in other areas, divers must watch for sea urchins, jellyfish, and rockfish, but land coast and on the windward sides of the offshore reefs. Rip currents are very and coves (see Section 10.2.3). in shark attacks in this Moderate-to-heavy surf prevails along the entire main- area are not common. In the last 15 to 20 years, fewer than 2 dozen shark attacks involving islands. Under certain weather conditions, the normally calm leeward sides also may present hazardous diving conditions. divers have been recorded; however, diving around the Currents and tides are not of prime importance Farallon Islands, Bodega Bay, Tomales Bay, and off the southwest coastal region, although there are local San Francisco water visibility is is not recommended except when under- ideal. Stingrays and electric rays are in exceptions. Currents around the islands, especially during tidal may changes, The attain speeds of 3 to 4 knots (1.5 to and also found in the mid-Pacific coastal region (for appro- 2 m/s). priate precautions, see Section 12.4). currents can be observed both topside and under water all There are five ecological reserves in this area, where animals and plants are protected: Point Lobos State direction relative strength of nearshore by watching the degree and direction of kelp layover. Hazardous marine organisms in this region include: Reserve, Point Reyes Seashore area, Salt Point State sharks (especially around the offshore islands) such as Marin County San Francisco, and Del Mar Landing in Sonoma County. Divers should consult with the park authori- the blue, horned, swell, angel, and leopard; whales Park, Estero de Limantour Reserve in north of determine the boundaries of these marine reserves ties to and the restrictions that apply to (including killer whales); jellyfish. moray eels; sea urchins; and Divers should be aware of the habitats, appear- ance, and habits of these species (see Section 12). Sewer them. outfalls are common along the mainland coast, and direct contact with sewer effluent should be avoided 10.1.7 Southwest Coast The waters Point Conception to the northern Baja Peninsula. Water temperatures range from 50 to 60 °F (10 to 16°C) in winter and 55 to 70 °F (13 to 21 °C) in summer, with some ing localized areas much made colder by upwelling. Dur- of the year, temperatures at depths below 100 feet (30.5 m) are fairly stable October 1991 — NOAA The outfall discharge point may occur from a few hundred feet to several miles offshore, in from 60 to several hundred feet (18.3 to several hundred meters) of water. The effluent sometimes rises to (see Section of the Southwest include the area from in the 50's Diving Manual and low 1 1 ). the surface in a boil characterized by elevated temperatures, paper If and other debris, and an unpleasant odor. diving must be conducted in outfall areas, precau- tions such as immunization, use of full-face gear, and 10-5 Section 10 scrupulous post-dive hygiene must be observed (see and coral abrasions are the most Section 11 for polluted-water diving procedures). Most injury. No license needed is common types of to harvest fish or crusta- be identified on the surface by a boil or by an orange- home consumption; however, game laws in most states place season and size limitations on some and-white striped spar buoy anchored near the pipe species. outfall discharge points are marked on charts and can ceans for terminus. As Northern California, ecological reserves that in have various restrictions have been established in the California Department of Fish and Game is the best source of information about the location of these reserves and any waters them. restrictions that pertain to Diving The two most important factors to be considered in and antarctic environments are the effects of cold on the diver and the restricted access to the surface when diving under ice. These topics are covered in arctic northern Mexican (upper Baja California) detail in the sections dealing with diving in cold similar to that in lower southern California. (Section 10.8) and diving under ice (Section 10.9). in is and Antarctic 10.1.9 Arctic southwestern coastal region. The local office of the However, Mexico imposes heavy fines and impounds Mexican waters without proper permits; permits can be obtained through the Mexican government or from Mexican customs officials in San Diego. the boats of people diving in Temperature in arctic waters can be as low as 28 °F (-2°C), but the air temperature and its associated chill factor may be more limiting to divers than the cold water Often, surface temperatures as low as itself. -40 to -50 °F (-40 to -46 °C) are reached, with accom- panying wind velocities that bring the chill factor to temperature equivalent to -100°F (-73°C) or 10.1.8 Central Pacific Ocean The Hawaiian Archipelago, which The major islands are: lesser less. a In such conditions, protecting divers from the extreme most accessible diving in this area Hawaiian Islands and the water is around the consists of the major known Leeward Islands. Hawaii, Maui, Kahoolawe, Lanai, Molokai, Oahu, Kauai, and Niihau. The Leeward Islands are a group of rocks, shoals, and islets that are rem- cold is paramount both before and the problem is is then both wet and chilled. conducted under the in a after the dive, although greater after the dive because the diver ice, When diving being is the dive should begin and end heated shelter positioned over the entry hole. If such a shelter cannot be positioned over the hole, one nants of ancient islands and seamounts that extend should be located within a few steps of the entry point. from Kauai to Midway Island. They are all wildlife reserves and generally are inaccessible except to government personnel or authorized visitors. The average water temperature around the major islands is 76 °F (24 °C) and changes very little with the seasons. Underwater visibility is almost always excellent, ranging from 50 to 100 feet (15.2 to 30.5 m) or more. Currents can sometimes be a problem in channels and near points and may reach speeds of up to 3 knots (1.5 m/s). High surf is also a potential hazard and may vary widely with the seasons. The heated make shore from all the islands, but rocks, surge, and surf must always be considered when planning entries and exits (see Section 10.2.1). Since drop-offs occur very near shore and It is possible to continue for several hundred feet, entries it is an airplane parked nearby When exposed to may extremely low air temperatures for longer than a few minutes, divers should Gloves wear heavy, (in the case of warm water be flooded with effects of air the water. loose-fitting and to forestall the chilling comfort to provide greater initial Hot water can be carried tainers such as hooded parkas. dry suits) or entire wet suits can in in insulated con- thermos jugs. In polar regions the marine species of concern are seals, walrus, killer whales, and polar bears. A predive reconnaissance by an experienced observer will indicate to if any of these animals is in the vicinity or is likely cause a problem (see Section 12.5). easy to get into deep water quickly after making a shore entry. Caution interior of satisfy this requirement. must always be exercised when making repetitive 10.1.10 Tropics Tropical waters provide the most interesting envi- because underwater dives. ronment Although most forms of dangerous marine life can be found in Hawaiian waters, they are uncommon. There have been a few recorded shark attacks over the years, but they are extremely rare and usually involve usually excellent and marine although the waters swimmers a storm, during plankton blooms, or from silting near 10-6 or surfers. Eel bites, sea urchin punctures, for diving, ity in tropical more. There waters is little is life visibility is abounds. The generally 50 feet (15.2 m) or variation throughout the year, may become murky and NOAA visibil- Diving Manual silty after — October 1991 Diving Under Special Conditions Water temperatures hover around 70° F shore. during the winter months and (28 °C) in Marine (21 °C) be as high as 82 °F may shallower waters during the summer. life to divers. contours or features, or triangulation methods using known shore When commercial abundant, and some forms are dangerous is Sharks thrive tions should be taken waters and precau- in these when they A are sighted. wide variety of poisonous marine animals (jellyfish, scorpionfish, sea snakes) also abounds (see Section positions should be used initially in locat- ing a dive site. diving operations are being con- OSHA ducted from shore without a boat, played at the dive location. entry conditions permit, If during the dive (see Section 14.2.4). in set aside for the also advisable signaling the shore in an emergency. These flares pro- vide a quick or work purpose of preserving means of accurately locating a diver on the surface (see Section 5.6.8). sanctuaries or underwater parks. These marine sanctu- have been It is equip each diver with a day/night signal flare for to 10.1.11 Diving in aries them divers should carry and/or tow the flag with 12). Marine Sanctuaries or Underwater Parks Divers may on occasion dive for recreation regulations require that the international code flag alpha be dis- Entering the water from a smooth, unobstructed is relatively quiet poses no shoreline where the water or restoring recreational, ecological, or esthetic val- problem. Most lakes, rivers (where currents near shore Examples include the Key Largo National Marine Sanctuary, Biscayne National Park, John Pennekamp Coral Reef State Park in Florida, and Buck Island in are not swift), bays, lagoons, quarries, and ocean coast- ues. (where surf lines negligible) have shorelines of this is type. the Virgin Islands National Park. Marine sanctuaries are built around distinctive marine resources whose protection and proper use require Entering the water even through moderate surf when comprehensive, geographically oriented planning and management but do people. It is not necessarily exclude use by important when diving in these areas to follow the rules and regulations established for sanctuary management. Accordingly, when conducting workmarine sanctuaries ing or scientific dives in designated and parks, ties DIVING lines tially A hazardous operation. conditions should be made is a difficult and poten- careful analysis of surf and, if conditions are con- sidered too severe to allow safe passage to open water, the dive should be terminated. WARNING FROM SHORE diver should expect to encounter a wide variety of conditions burdened with diving equipment important to check with local authori- is before beginning operations. 10.2 A it Through Surf 10.2.1 when entering Before Diving Through Surf From an Unfamiliar Beach, Local Divers Should Be Consulted About Local Conditions the water from shore. Shore- vary greatly, and diving from a particular shore requires individual preparation and planning. Before entering the water, divers should observe the Before entering the water from shore, special atten- surf. Waves equipment checkout. Since diving equipment is often placed on the ground near the water, small dirt particles may have entered a space in the equipment that requires a per- with little tion should be given to the predive fect seal or has a close tolerance. amount of Even the smallest dirt in a regulator or reserve valve may traverse vast expanses of ocean as swell, modification or loss of energy. However, as the waves enter shallow water, the motion of the water particles beneath the surface is altered. When a wave enters water of a depth equal to or less than one-half of wavelength, its orbital it is said to "feel bottom." The circular motion of the water particles becomes ellipti- with depth. Along the bottom, the particles cause a serious air leak or a valve malfunction. Extra cal, flattening care must be taken to ensure that diving equipment oscillate in a straight line parallel to the direction of is wave kept as free from dirt as possible. If the dive from shore underwater location, it is is to be made to a precise mark marker buoy or surface float. floating on the surface, however, diver to see; therefore, October 1991 A the wave feels bottom, and its done by using small marker buoy into water whose depth may be difficult for a compass bearings, underwater — NOAA travel. the spot advisable to clearly at the water surface. This can be a As Diving Manual the steepness increases. is its As wavelength decreases the wave crest moves approximately twice that of wave height, the crest changes from rounded to a more pointed mass of water. The orbital veloc- higher, ity of the water particles at the crest increases with 10-7 Section 10 Figure 10-1 Schematic Diagram of Waves in the Breaker Zone A (4) diver standing on the shore backrush; beach (5) and looking seaward would observe and face; (6) inner translatory waves; (7) note: (1) Surf zone; (2) limit of uprush; (3) uprush; inner line of breakers, (8) inner bar; (9) peaked-up wave; (10) reformed wave; (11) outer translatory waves; (12) plunge point; (13) outer line of breakers; (14) outer bar (inner at low tide); (15) breaker depth, 1.3 x breaker height; (16) waves flatten again; (17) waves peak up but do not break on this bar at high tide; Adapted from US Army Corps of Engineers (1984) (18) deep bar (outer bar at low tide); (19) still-water level; and (20) mean low water. oscillatory increasing wave height. This sequence of changes is the prelude to the breaking of the wave. Finally, at a depth of approximately when 1.3 times the wave height, more the wave becomes wave the steepest surface of the than 60 degrees from the horizontal, inclines unstable and the top portion plunges forward. The are good, the diver should begin swimming seaward on the surface, using a snorkel. If heavy sets of waves are encountered, it may be and to swim as close to bottom is rocky, divers grasping the rocks; on necessary to switch to scuba the bottom as possible. If the can pull themselves along by called surf a sandy bottom, a diver can thrust a knife into the bottom to achieve the same (Figure 10-1). This area of "white water," where the purpose. Ripples on a sandy bottom generally run par- waves finally give up their energy and where systematic water motion gives way to violent turbulence, is called the surf zone. The surfs white water is a mass of used to navigate through the surf zone by swimming wave has broken; this turbulent form water containing bubbles of entrapped is air; these bub- normal buoyancy of the water. bles reduce the Having broken into a mass of turbulent foam, the wave continues landward under beach face, this its own momentum. momentum swash. At the uppermost limit, Finally, at the an uprush or the wave's energy has carries it uprush must now return seaward as backwash, ment of water is to the sea. This i.e., as seaward move- generally not evident beyond the surface zone or a depth of 2-3 feet (0.6-0.9 m). By watching the surf for a short period of time, water entry can be timed to coincide with a small set of waves. When ready to enter, the diver should approach the water, fully dressed for diving. to the face, and place the snorkel in the mouth. With one hand on the faceplate, the diver should then turn around and back into the water with knees slightly bent and body leaning back into the wave. If conditions 10-8 somewhat obliquely to shore, and they can be perpendicular to them. Divers entering with a float it behind them on 10 to 30 feet (3.0 to 9.1 m) and should be aware of the possibility that turbulence may cause the line to wrap around a leg, should pull of line arm, or equipment. WARNING Divers Near the Surface Should Not Hold Their When a Wave Is Passing Overhead Because the Rapid Pressure Drop at the Diver's Depth When the Wave Trough Passes Overhead May Be Sufficient to Cause a Lung Breath Overpressure Accident At the water's edge, the diver should spit on the faceplate, rinse and adjust it or into diminished. The water transported landward in the current flowing back allel Swimming over breakers should not be attempted. As breakers approach, the diver should duck the head and dive under and through them. Diving at the base of the wave is advantageous because the water molecules will carry the diver up behind the wave. NOAA Diving Manual — October 1991 Diving Under Special Conditions A group of divers may make a surf-entry in buddy teams and meet beyond the surf zone at the diver's flag. Once safely through the surf, all equipment should be checked. Even a moderate surf can knock equipment out of adjustment or tear it away. Sand may have entered the mask, regulator, or fins after the diver has passed through the surf. Divers should take time to remove the sand before continuing the dive. cause it in the exhaust valve of a regulator can to seal improperly, permitting water, as well as enter the mouthpiece air, to fins, Sand though only mildly when Sand inhaling. irritating at first, in the may cause carried back toward the shore and then kick seaward wave after the When passes. exiting on a rocky shore, divers should stop wave conditions outside the surf zone to evaluate the toward the beach on the backside and should then exit of the last large wave of the wave As momentum from a series. divers should kick or grasp a rock to lost, is avoid being carried seaward by the backwash. Divers should maintain their position, catch the next wave, and thus move shoreward, exercising caution over slip- pery rocks. a painful abrasion by the end of a dive. Exiting the water through the surf involves performing same procedures used to order. The diver should wait enter, except in reverse the just seaward of the surf for a small set of waves. When the diver should begin swimming shoreward (while a set has been selected, keeping an eye on the incoming waves) immediately after the passage of the last of the larger waves. The Through Shore Currents 10.2.3 In and adjacent to the surf zone, currents are gener- ated by approaching waves (and 1) and 4) tides. When waves angle, a longshore current allel to approach the shore common progress toward the beach. Using this assisting wave current increases swim toward the beach until reaching waist-deep water. At this point, while there is still enough water for support and balance, divers 2) increasing The should pivot around, face the waves, and plant their (0.5 m/s). feet firmly. The diver should then stand up, and, bend- and hips enough When back out of the water. should position them to avoid it velocity 3) increasing velocity angle of along straight beaches. The with the breaker 1) breaker to height; the and 4) decreasing wave of longshore currents seldom exceeds beach Wave slope; shore; period. 1 knot fronts advancing over non-parallel bottom contours are refracted cause convergence or to maintain balance, divergence of the energy of the waves. In areas of exiting with a float, divers convergence, energy concentrations form barriers to down current to or push becoming entangled in it ahead of the towline. As soon as the divers are out of the water, they should remove their fins. knocked over by surf action after standing up, turn; only then should they If an the beach within the surf zone. Longshore currents are most ing at the knees at generated that flows par- is smaller waves breaking behind will assist the diver's action, the diver should bottom surf); 2) contours and irregularities; 3) shoreline geography; the returning backwash, which is deflected along the beach to areas of less resistance. These currents turn seaward in concentrations at locations where there are 'weak gaps points,' in the extremely large water accumulations, bar or reef, or submarine depressions per- divers should not try to stand again but should let the pendicular to shore, and form a rip current through the waves carry them onto the beach. Hands and surf (Figure 10-2). fins should be dug into the bottom to prevent being swept seaward by the backwash. On reaching shore, the divers should crawl out of the surf on their hands and knees. 10.2.2 Through Surf on a Rocky Shore Before entering surf from a rocky shore, divers should evaluate wave conditions and should not attempt to stand or walk on rocks located in the surf zone. Instead, divers should select the deepest wave of backwash of the last and enter the water; the backwash should carry the diver between the larger rocks. Every effort should be made to swim around the rocks large a series rather than over them. Divers should stay in the small deeper channels between rocks and maintain a prone swimming position facing the next They should kick October 1991 oncoming wave. or grasp a rock to keep from being — NOAA Diving Manual The volume of returning water has a retarding incoming waves. Waves adjacent to the rip current, having greater energy and nothing to retard them, advance faster and farther up the beach. Rip currents may transport large amounts of suspended material. A knowledgeable and experienced diver can use rip currents as an aid to swimming offshore. A swimmer caught unsuspectingly in a rip should ride the current and swim to the side, rather than swimming large effect on the against the current. Outside the surf zone the current widens and slackens, which permits the diver to enter the beach at another location. Rip currents usually dissipate a short distance seaward of the surf zone. Most shorelines are not straight. Irregularities in the form of coves, bays, and points affect the incoming waves, tidal movements, and current patterns. When preparing for beach entries and exits, a diver should 10-9 Section 10 Figure 10-2 Near-shore Current System break up the wave action sufficiently to allow passage over the inside calm area without difficulty. If a channel can be located that will allow passage through the should follow reef, the diver deep water. it, submerged if possible, passage cannot be located, the diver should approach the edge of the reef, into If a satisfactory wait for a wave to pass, and slip over. \ 4 MassTranspo \ *~ Longshore Current Shore Line can be used. In addition, Curren t all possible before entry. line, under equipment required equipment can be transported by vehicle directly to the dive Ladders should be used is site. to get as close to the Any approved water as entry technique, such as stepping, can be used safely for heights up to Source: Baker et al. (1966) not (0.9 take wave approach, shoreline configuration, and currents into account. Entries to avoid high waves and and exits should to take be planned advantage of current movements. Divers should avoid dives that require swimming against the current and should never undertake a dive from an ocean beach without considering these factors. Hypothetical beach configurations, approaches, wave and current diagrams are shown in The roll-in method shown in Figure 10-4 recommended for heights greater than 3 or 4 feet to 1.2 m) above the water. Immediately prior to 10 feet (3.0 m). is submerged obstructions. Floating debris is common around a pier, and pilings often rot or break off just below the waterline. Divers should not into jump an area that has not been examined beforehand or where the water is not clear enough to see to the depth of the intended dive. If the dive is to be conducted from an ocean pier or other high platform and no ladder Figure 10-3 to aid divers in planning beach-entry dives. check for floating entering, the diver should carefully debris or is available, gear can be lowered into the water and divers can heavy make a shore entry with a snorkel, equipping themselves 10.2.4 From a Coral Reef with scuba at pierside. If conditions Diving operations from a reef should be planned, possible, to take place at high tide when water if covers the reef. For a diver wearing equipment, walking on a reef is hazardous. Footing is uncertain, reefs are gen- pocked with holes, and areas that look break under a diver's weight. erally solid may impossible, using a small boat is a shore entry When swim- ming under a pier or platform, divers should be submerged whenever possible to avoid contact with pilings, cross-supports, and other potentially hazardous objects. When exiting the water onto a pier or platform, the diver should stop at the ladder to (The ladder should extend 3 NOTE make advisable. to remove his or her fins. 1.2 m) into awkward and 4 feet (0.9 to the water.) Climbing a ladder with fins is dangerous and should be avoided unless the ladder Coral shoes or hard-sole neoprene boots should be worn around coral. In some instances, there side of the reef swimming. In 10-10 may be an area on the shore where the water is deep enough for this case, the outer side of the reef will is designed specifically for use with fins (see Figure 10-5). Tanks and other cumbersome equipment should also be removed and tied securely to a line and be hauled up after the diver reaches the top of the pier. Piers and docks often contain fishing lines, and care must be taken to avoid being hooked or becoming entangled in these lines. NOAA Diving Manual — October 1991 Diving Under Special Conditions Figure 10-3 Shore Types and Currents R ' ' is } '/ J Xy Small Deep Coves Points Rip Currents Rocky Cove - Sand Bar - Sandy Beach Reefs E Heavy arrows indicate direction of wave approach; dashed = entry; X — - Rip Current exit. lines represent path of currents, while direction is shown by light arrows. Source: 10.4 A DIVING small boat FROM A SMALL BOAT is probably the most common • larger solid-hulled vessels. A in (1979) cold or inclement weather for the dive party en route to the dive site and, surface- back to shore Be maintained properly and in good repair Carry a diver's flag (see Table 14-2). after the dive, support platform used by divers with self-contained equipment. Configurations and types of small boats vary greatly and range from small inflatable boats to Provide some shelter NOAA • • boat used as a platform Small boats used to tend divers can be either anchored should: When anchored, the boat should be downstream of the site for easy access when divers surface, and a surface float should be streamed off the stern. Even anchored boats need to be able to move immediately in case an incapacitated diver must be recovered; a buoyed anchor line facilitates a quick getaway. The operator in the boat should keep a constant watch on the diver's bubbles, and great care or unanchored. • • Be equipped with a means for divers to enter and leave the water easily and safely Be seaworthy and loaded within the capacity recommended by the manufacturer for the expected water conditions • Be large enough to accommodate all members of the dive party, the diver's life-support equipment, and any special equipment being used of the dive October 1991 in support positioned should be taken to stay clear of divers gear. — NOAA Diving Manual When if an engine is in tending without an anchor, the operator 10-11 Section 10 Figure 10-4 Entering the Water Using the Roll-In Method Source: Figure 10-5 wale and rolling into the water Transom-Mounted Diver Platform distance is NOAA considered best (1979) if the not greater than 3 to 4 feet (0.9 to 1.2 m) (Figure 10-4). The is diver should examine the area to be entered to ensure that it is on the gunwale clear, sit facing the center of the boat with both feet inside, and lean forward to counterbalance the weight of the equip- ment. When ready to enter, the diver should simply sit up, lean backward, and let the weight of the diving equipment carry him or her over the side. A second method of entry is the 'step-in' method, which is generally used when entering the water from a larger boat. The diver should step onto the gunwale, bend slightly forward at the waist, and step off into the water. When entering the water using these methods, the diver should always hold the face mask firmly in place. Also, any required equipment that cannot be carried conveniently and safely should be secured to a piece of line, As hung over the side, and retrieved after entry. a general rule, the diver should always enter the water slowly, using the method that NOAA Source: should drop the divers off upstream of the boat should then remain downstream of the site. site (1979) The during least physical will result in the discomfort and disturbance to equip- ment. Each diver should determine the method best suited to various water conditions. operations. Drift-diving with a surface float provides an effective method for keeping the boat in position for pickup. 10.4.2 Exiting the When general rules to 10.4.1 Entering the Water Entering the water from a small boat can be accomplished safely by several methods. Sitting on the gun- 10-12 Water exiting the water into a boat, there are two remember and follow. First, exiting actually begins while the divers are still submerged. While ascending, divers should look upward continuously to ensure that the boat is not directly overhead and NOAA Diving Manual — October 1991 Diving Under Special Conditions Figure 10-6 Side-Mounted Diver Platform that they will not strike arm over when it the head during ascent Exhaling during the ascent will alert will surfacing. Holding an is also a good practice. produce bubbles, which surface personnel that the diver is ascending. Second, after surfacing, the diver should not attempt to enter the boat wearing tanks or other heavy equip- ment unless the ladder is strong enough to handle the combined weight of diver and equipment. The diver should remove the tanks and obtain assistance from someone in the boat or from another diver in the water before climbing aboard. Rails extending above the sides of the boat are useful as handrails to support the diver as he or she climbs into the boat. Probably the most widely used method of returning to a small boat is via a diver's ladder. Ladders also provide a secure point for divers to grasp while they are still the water. in A ladder may be built in many con- Source: NOAA (1979) figurations but should have these general characteristics: • It should extend below the surface of the water 3 to 4 feet (0.9 to 1.2 m), providing a place for the diver to stand and hold on while removing equipment. • should be strong, well built, and capable of It being securely fastened to the side so shift when subjected it will not to the action of the seas diver comfortably. • It should be angled away from the boat to permit It the boat and suspended just below the surface of the A diver can swim onto the platform, sit securely while removing equipment, and then stand up and step A hand- or arm-hold should portable, easily stored platform (Figure 10-6) can be constructed from either wood or safely into the boat. should have rungs that are Modifying conventional ladders flat and wide. to fit small boats be provided. A is unsatisfactory because these ladders are closed on both sides assisting a diver into a small boat the use of a platform rigged to the stern or the side of water. easier ascent. • Another method of is should be wide enough to accommodate the It motor, so the diver can pass unhampered on the other side. and the diver's weight. • The ladder should extend about 30 inches (77 cm) below the water's surface to allow diver access. The ladder should have a handle only on the side next to the metal. by rung support shafts, are difficult to climb FRESH WATER DIVING with equipment, and hang too close to the boat to provide 10.5 sufficient toe space. There are thousands of square miles of fresh water Figure 10-5 shows a ladder that is designed to allow a fully equipped diver to re-enter a small boat with safety and ease even in strong currents. The most impor- tant features of the ladder are lack of side supports ('open step' design), its slope, and positioned on the transom of the boat. its ability to be With a ladder of the open step type, divers can use the inner sides of and can then step onto the rung from the side. The angle between the shaft and the transom should be 35 to 40 degrees. Positioning the ladder on the transom (the strongest part of the boat) is particularly important in rivers because the boat partially protects the diver from the their feet to locate the ladder rungs force of the current ladders positioned on the side of the boat are used, the may push October 1991 The five in Great Lakes alone have a total area of 95,000 square miles (2,460,500 sq km), and the two-thirds of these lakes that lie within U.S. boundaries represent almost half of the fresh water acreage in the country. Basic techniques for diving in lakes, rivers, and quar- much like those used in ocean waters. Howevsome differences should be noted. For example, ries are er, depth gauges are calibrated for seawater density, and adjustments must be made to achieve accuracy in fresh water (see Section 10.12. 5). Buoyancy requirements also are somewhat different for fresh and salt water. and because the diver can climb out of the water parallel to the current. If conventional current the United States. the diver sideways. — NOAA Diving Manual 10.5.1 Great Lakes Great Lakes divers need to be aware of the tempera- ture changes that occur with changes in depth and 10-13 Section 10 season. In a typical fresh water lake, the upper layer Old cables, heavy equipment, electric cables, rope, (epilimnion) temperature generally ranges between fishline, fishing lures, 55 and 75 °F (13 and 24 °C) in late summer. However, the lake bottoms. waters below the thermocline (hypolimnion) approach the temperature of maximum density for fresh water, 39.2 °F (4°C). Consequently, divers working below the thermocline, which averages 60 feet (18.3 lakes in late summer, must plan to use m) in these buoyancy con- and thermal protection. During the winter months, the water temperature in the Great Lakes ranges between 32 °F (0°C) near the surface and 39.2 °F (4°C) on the bottom; during this period, a significant portion of the Great Lakes is ice Many and even old cars are often found on lakes have never been cleared of trees, barns, houses, water towers, and other objects. The bottom sediment of lakes is easily stirred up, as is sediment that has settled on lake-bottom trees or brush. Divers should stay off the bottom as much as possible and move slowly when forced to work on the bottom. trol covered. Occasionally, divers are required to 2 to 16 inches (5.1 to 40.6 tions, collect ice to work under make observa- samples, or maintain scientific equipment. Diving under ice special techniques taken only cm) of when is particularly hazardous, requires and equipment, and should be under- absolutely necessary (see Section 10.9). Divers and surface support personnel operating in the lakes may be subjected to atmospheric temperatures of -30 °F (-34 °C), with wind chill factors approaching -100°F(-73°C). Underwater visibility in the Great Lakes ranges from m) less than Lake Erie. Visibility is influenced by local precipitation and runoff, nutrient enrichment, biological activity, local bottom conditions, and diver foot (0.3 in activity. Significant seasonal variations also occur in these waters. From September Artificial to December, storms and severe wave conditions can be expected water systems such as reservoirs and flooded strip mines, gravel pits, or stone quarries are popular some areas, they represent the only and in other regions they are used spots for diving. In place for diving, primarily for diver training. Quarries usually are deep; their water originates from seepage in the surrounding water table. For this reason, the water usually is low in nutrients and significantly colder than water in areas primarily fed by runoff. As the water near the surface warms up during the summer months, a sharp thermocline is created that must be taken into account when dressing for a quarry dive. Quarries are used frequently as dump about 100 feet (30.5 m) in Lake Superior to 1 10.5.3 Quarries sites for old cars and a variety of junk, and quarry divers must beware of becoming snagged on sharp metal or monofilament sediment 10.6 is stirred up and line, especially visibility is when the reduced. OPEN-OCEAN DIVING Researchers have recently become interested and sampling pelagic organisms directly in observing in the open Great Lakes. ocean instead of collecting specimens using such con- Divers working offshore at these times must use sturdy ventional techniques as Niskin® bottles, grabs, or nets. in the and monitor weather forecasts. Because swift currents may be encountered in rivers and straits connecting with the lakes, Great Lakes divers must use considerable caution and be properly trained in the vessels techniques of diving in currents (see Section 10.15). However, because open-ocean (also termed blue-water) diving does not provide a fixed frame of reference, divers performing open-ocean dives may become disoriented because they have a reduced awareness of depth, buoyancy, current, surge, other divers, marine organisms, or, occasionally, even of the direction of the surface (Heine 1985). Special techniques have there- 10.5.2 Inland Lakes Other lakes in the United States vary from clear mountain lakes with low sediment input to reservoirs, sediment-laden rivers, and glacial lakes, which usu- When planning a lake bottom terrain is as important a consideration as underwater visibility. Lakes may have vertical rocky ally have a milky appearance. dive, sides, rocky outcrops, ledges, and talus slopes, or they may be sedimentary and composed primarily of old farm land. Algal blooms often occur in lakes during the warmer months and may completely block the light, even at shallow depths. Thermoclines also occur, and temperature and underwater 10-14 visibility may vary greatly. fore been developed to aid the diver operating in the open ocean to carry out scientific tasks safely. Blue-water diving is usually done from a small boat to facilitate diver entry, exit, and maneuverability and to minimize the 'sail' area, which reduces drift and the consequent dragging of divers through the water. Even when operations vessel, a small are being conducted from a large boat should be used to tend the divers because wind and surface currents often carry a larger boat away from the actual dive site. Open-ocean dive teams generally consist of a boat operator (who remains in the boat), a safety diver, and as many as four or five working divers. After reaching NOAA Diving Manual —October 1991 Diving Under Special Conditions Figure 10-7 Down-line Array for Open-Ocean Diving 100 feet (30 m) long, the dive site, a downline about loaded with 5 to 10 pounds (2.3 to 4.5 kg) of weight and knotted at specific depths, passed from the boat is through a surface float and lowered to serve as a safety (Figure 10-7). This line line for the divers then is secured to the surface float and to the small boat. m) 4-foot (1.2 sea anchor is A frequently used to reduce caused by wind; the anchor can be attached to a drift loop in the downline at the surface float or to a separate float to keep from collapsing and sinking if the wind it is useful to drop a small it To mark dies. the dive site, open jar of fluorescein dye into the water. The vertical column of dye emitted as the jar descends will be distorted by currents, giving a visual display of the current pattern in the water column Because of the absence of any the inherent danger of drifting ocean divers are tethered (see Section 9.8.2). visible reference away or down, all and open- at all times to the safety line an underwater trapeze. The trapeze can be configured via Adapted from Hamner (1975) from any bar or ring that accepts clips and shackles easily. Figure 10-8 shows examples of three types of than to the tether), trapezes that have been used for this type of diving. In conventional diving, in buddy swim divers together; it diver's body, can be released by pulling which ensures that it away it will release. open-ocean diving, however, the safety diver serves buddy diver as the shown in for all of the divers Figure 10-7, all on the team. As divers are tethered to the trapeze by means of lines approximately 30 to 50 feet (9.1 to 15.2 underwater To avoid m) long; the length of the line visibility depends on and the task being undertaken. kinking, tethers should be braided lines. good rule of thumb to from the is A WARNING Tethers Should Not Be Attached to a Diver's Weight Belt, Because Ditching or Losing the Belt Would Add Excessive Weight to the Trapeze Array to restrict the length of the tether about 50 to 75 percent of the nominal underwater (Heine 1985). The exception to this the safety diver's tether, which should only be visibility distance rule is about 3 feet (0.9 m) they understand the diving signals, especially the long. Because tethers of a fixed length tend droop and to become tangled, they should be designed taut at ling. all times, which also to remain facilitates line-pull signal- This can be achieved by weighting the end nearest the safety diver with a 4 to 8 ounce (113 to 227 fishing weight. The Before starting a blue-water dive, all equipment must be checked and the divers must all be sure that gm) tether then passes freely through tug signals, that will be used. the water down first, but all The line- safety diver enters of the divers usually descend the line together to connect the pivot ring to the vertical line and to prepare the tethers. During the dive, the safety diver monitors the tethers, keeps a lookout for hazards, and supervises the dive. The safety the metal loop on the end of a swivel clip (Figure 10-8); diver maintains visual contact with the other divers these clips are attached to the trapeze, which near the safety diver. Thus, as the working diver swims and can attract their attention by tugging at their tethers. The boat operator can signal the safety diver away from the safety diver, the tether pays out smoothly, by pulling on the vertical when the diver returns, the tether retracts as the team can communicate and be alerted to ascend at any time during the dive. A good practice is to have each diver run the tether through the palm of one hand so and, weight sinks. In conditions of low lines is located visibility, tether can be shortened by tying a knot on the weight side of the tether, thus shortening the length available to pay out. nected to The other end of the tether should be the diver's buoyancy compensator or separate harness. If the quick-release shackle to the diver's is conto a attached buoyancy compensator or harness (rather October 1991 — NOAA Diving Manual line. In this way, the entire that the line-tugs can be detected easily. diver can line to move any of the knotted thus control the The the pivot ring up and maximum down The stops, as required, depth of all safety the vertical and can of the divers. safety diver can also terminate the dive or send 10-15 Section 10 Figure 10-8 Three Multiple Tether Systems (Trapezes) Used for Open-Ocean Diving Brass Snaps Working Diver's Tether Bottom Weight Running Counterweight Source: Rioux, as cited in Heine (1985) Stainless Steel Attachment Ring Swivel Snaps Working Diver Tether Line Knot in Line Running Counterweight Polypropylene Washer Safety Diver Tether Line ( Source: )) Small Coated Weight Hamner (1975) Source: Coale and Pinto, as cited 10-16 NOAA Diving Manual in Heine (1985) —October 1991 Diving Under Special Conditions any diver up if the situation warrants such action. Divers can ascend at will by signalling their intent to temporary safety diver. There must always be someone acting as safety diver (Heine 1985). As with any the safety diver, unclipping their tethers at the pivot ring, and ascending the vertical line to the boat. If away from can be attached it depth as the line is is to the line at the appropriate deployed, which makes it unneces- Any equip- ment hung on the downline should be positioned above the trapeze and safety diver, and the weight of the equipment must not be so great that it overweights the downline. Divers working below the trapeze must be careful to avoid entanglement in the weighted tethers, which would envelop the safety diver in a cloud of bubbles and reduce his or her ability to see. If a second line is deployed for equipment, it must be separated clearly from the safety line and should not be used as for tethers. and In addition to diving, safety, scientific equip- ment, most open-ocean divers carry a shark Section According 5.7). to experienced at the University of California at Twenty percent of Readers should consult a specialized open-ocean diving man- hung on the sary for the divers to carry the equipment. an attachment specialized diving, open-ocean diving requires individualized training and practice. ual for further details about this type of diving. the boat. scientific or diving equipment downline, is when ascend- important that the divers hold the downline ing so that they do not drift It billy (see blue-water divers Santa Cruz: the blue water dives all performed by our group in the central 10.7 CAVE DIVING Cave diving performed To holes.' is in a specialized form of diving that can be both inland fresh waters and ocean 'blue scientists, caves offer new laboratories for research. In cave diving, the emphasis should be placed on developing the proper psychological attitude, training in specialized techniques and life support systems, dive planning, and the selection of an appropriately trained buddy diver. WARNING Only Experienced and Specially Trained Divers Should Undertake Cave Diving. Openwater Experience Is No Substitute for Cave Diving Training north and south Pacific gyre systems and the eastern tropical Pacific were aborted due to the persistent presence of sharks, specifically oceanic white tip sharks. In were spotted first all cases they by the safety diver. This The cave diving environment because it is alien to humans, involves both the underwater environment and the limited-access, limited visibility, confined space environment typical of caves. Examples of the special may be encountered cave diving are: underscores the value of the safety diver hazards that and a routine abort plan and the the absence of a direct and immediate ascent route to utility of the surface, the sometimes instantaneous loss of visi- the shark billy (Heine 1985). bility Divers generally work in an area upstream of the because of silting or failure of the diver's light, the divers and the downline, and generally monitors and the entanglement and impact hazards associated with being in a confined, enclosed area. These and other factors all have an effect on the psychological composure of divers and their ability to cope with stressful situations. Improperly trained divers, unaware of the hazards unique to cave diving, often panic and drown when they encounter situations that are in fact normal for the cave diving environment. It is impera- the progress of the dive. During the course of the dive, tive that divers the safety diver maintains contact with the divers by tude before they consider conducting a cave dive. periodically tugging on the divers' tethers to ensure pletion of a standard scuba diving course does not trapeze, in which allows them samples and to collect fresh, undisturbed to stay in a single area in sight of the As they perform their tasks, the divers make visual contact with diver. The safety diver constantly monitors safety diver. scan their surroundings and the safety the surroundings, checks for sharks, keeps an eye on that they are comfortable, their air supply and they are responding If a is adequate, to pull signals appropriately. diver requires minor assistance, the safety diver signals another diver to go to his or her aid. Before the safety diver or she becomes involved must first signal October 1991 — NOAA in helping another diver, he another diver to act as the Diving Manual develop the proper psychological prepare a diver for the special perils faced in atti- Comcave diving. Before taking a course in cave diving, the diver- student must have enough open-water experience to feel psychologically and physically comfortable under water. Because their lives may one day depend on the 10-17 Section 10 Figure 10-9 Safety Reel Used in Cave Diving quality of instruction received, persons contemplating taking a course should select one taught by a mature and nationally A certified cave diving instructor. good cave diving course should include prescreening of potential divers, at least 100 hours of training in underwater work, and instruction in line safety, the elements of buddymanship, dive planning, equipment handling, and dive theory. Three. basic rules of buoyancy control, must be adhered safe cave diving that to by every diver are: (1) Always use a continuous guideline (2) Save two-thirds of the total air to the surface. supply for returning to the surface. (3) Carry at least three lights during the dive. Source: A common silt. hazard To minimize swim trained to buoyancy A cave diving in and cave diver's link to the Temporary safety and navigation. lines are the consist of a safety reel and most line. suitable safety reel should feature a line guide, A drum, buoyancy chamber, a good turns ratio, and be capable of carrying approximately 400 feet (122 m) of 1/16 inch (1.6 mm), 160-pound (72.6 kg) (3.2 line. test to 1/8 inch mm), 440-pound (199.6 kg) test braided nylon The reel should be neutrally buoyant, compact, and rugged (Figure Standard cave diving life-support systems should include: line are the surface and survival. Several kinds of lines are used for commonly used and (1979) cave divers must be specially silting, horizontally and to maintain proper at all times. safety reel NOAA the presence of is 10-9). Large reels and double tanks double manifolds two regulators submersible pressure gauge buoyancy compensator with automatic inflator hose depth gauge watch decompression tables wet or dry suit safety reel with line lines create lights extra drag for the diver When and require extra exertion. running a safety should maintain tension. line, The compass the diver with the reel slate line should be tied within surface light, and safety wraps should be made pencil. approxi- mately every 25 feet (8.3 m). The line should be centered in the cave as much as possible. The reel-diver is first in and last out. The buddy is responsible for The larger capacity double-tank arrangement recommended for cave diving has an 'ideal' or double-orifice manifold. This system manifolds two tanks together common gas supply and uses two regulator unwrapping the safety wraps on leaving the cave and with a for providing light for the diver tying or untying the adaptors. If one regulator line. Physical contact with the line should be avoided except when visibility decreases. In some cases, cave tion without interruption permanent lines for mapping or to permit a more complete exploration of a cave. Novices should use temporary lines and should not attempt to follow permanent lines unless they have a thorough knowledge of the cave. The technique for laying and retrieving a safety line is unique to cave diving and should be practiced until it becomes second nature, because it could save one's life in a total silt-out, where there is a complete loss of visibility. It is impor- cylinders. One 5-foot (1.5 m) hose divers will use tant to remember that in cave diving the safety line not a tow line and should not be used for support. 10-18 is fails, that regulator may be shut off while the second regulator continues to func- and with access to both gas of the regulators also should have a so that divers may share their gas supply when maneuvering out of tight situations. Although the need for lighting in cave diving obvious, the lighting taken on cave dives is adequate for safety. Each diver must carry at lights, is often not least 3 with the brightest being at least 30 watts. Backup can be of lower wattage, but they must also be dependable and of high quality. All cave diving equipment must be checked and rechecked by each member of the dive team before lights NOAA Diving Manual — October 1991 Diving Under Special Conditions submersion ation, to ensure proper functioning, ease of oper- and diver During familiarity. smooth this time, the Two types of diving dress have been used with suc- cess under severe thermal conditions: the hot-water which provides a continuous flow of preheated operation of backup equipment should also be verified wet and the dive plan should be reviewed water to the diver, and the variable-volume dry suit, which allows the diver to control the amount of air in for the last time. The maximum recommended number of cave per team three. is divers Larger groups cannot handle the integrated 'buddymanship' necessary to maintain the constant contact so essential in cave diving. For fur- ther information about cave diving, readers should Cave Diving, Box write to the National Association for 14492, Gainesville, Florida 32604, or the National Cave Diving Speleological Society's Oak low Section, 3508 Hol- Place, Brandon, Florida 3351 1. suit, the suit and thus its wet suit presented is Except for the hot-water wet tion 5.4.) more insulating capability. (A detailed description of these suits in Sec- no dry or suit, provides complete protection of the diver's hands for long periods. As the extremities become cold and dexterity is lost, the diver becomes less efficient and should terminate the dive. The use of heavy insulating socks under the boots of a wet or dry suit will help to keep the feet warm. Hands should be protected with gloves or mittens having the fewest possible digits; 10.8 COLD-WATER DIVING Diving in cold water associated with several equip- is ment problems not found in warmer waters; the major Most single-hose difficulty involves the regulator. regulators have a tendency to freeze in the free-flow extreme position after approximately 20-30 minutes of cold-water exposure. However, several models are avail- and that use a able that are designed to resist freezing special antifreeze-filled housing system. The standard double-hose regulator rarely develops this freezing problem. If a regulator begins to freeze up, the dive should be aborted immediately. freeze-up is about to occur is An early sign that the presence of ice crys- tals on the tongue. Second-stage freeze-up ally caused by moisture in is that the diver's Divers must be careful seawater through their noses, because introducing very cold water into the mask often causes divers to inhale involuntarily. Keeping the diver's body warm is The standard foamed-neoprene wet suit has 10-10). been used 29 °F (2°C) water for dives lasting longer than an doubtful whether the divers on these dives were comfortable or thermally safe. drawback of wet suits over, the diver wet and is that, is A major by the time the dive will therefore is probably con- body heat even after leaving the water. Further, the loss of foam thickness with depth drastically reduces the efficiency of any wet suit for cold tinue to lose water diving much below 60 October 1991 — NOAA from the head can be reduced by wearing a second well-fitted neoprene hood over the regular suit hood. Wearing a knitted watchcap under the hood of a dry suit If the suit's is cap especially effective in conserving body heat. pushed back is far enough to permit the face seal to seat properly, the diver's head will be kept relatively dry and comfortable. With a properly fitting suit kept and warm and If divers all can usually be seals in place, a diver dry, even in cold water, for short periods. and members of the surface-support crew feet (18.3 m). Diving Manual maintained in the best possible condition, dry suit underwear should be kept clean and dry, and all seals and zippers should be inspected and repaired (if necesDuring the dive, divers should body heat. Dives should be terminated immediately if the diver sary) before the dive. exercise as much as possible to generate begins to shiver involuntarily or experiences a serious loss of manual dexterity. Once involuntary shivering begins, the loss of dexterity, strength, and ability to function decreases rapidly (see Section 3.4). After leaving the most impor- tant requirement in cold-water diving (Figure is loss warm recommended. also water exposure can be greatly reduced. Suits should be relieve this condition temporarily. it Heat is the exhaled breath, which mask is more likely to fog or freeze in cold water, which means that a non-irritating defogging agent should be applied to the mask before diving. Partially flooding the mask and flushing seawater over the faceplate will hour, but water just before the dive begins follow certain procedures, the adverse effects of cold- Another cold-water diving problem in they provide. Filling the gloves or mittens with gener- is then condenses and freezes on the metal parts. to avoid inhaling cold manual dexterity associated with the use is overridden by the added warmth the loss of of gloves or mittens the water, cold-water divers are often fatigued, and, because heat loss from the body continues even after removal from cold water, such divers are susceptible hypothermia. Flushing the wet suit with warm to water as soon as the diver surfaces has a comforting, heatreplacing effect, although such flushing can cause additional body heat loss unless it is done cautiously. must be provided that allow the diver a comfortable, dry, and so that he or she can regain relatively warm lost to Facilities dry off in environment, body heat (see Section 3.4.4). Divers should remove any wet clothes or suits, dry off, and then don warm protective clothing 10-19 Section 10 Figure 10-10 Water Temperature Protection Chart /7=\\ °F *"tVpl£ Normal Body Temperature 98°F (3rC) 35— Unprotected Diver Average Skin Temperature 93°F (34°C) Unprotected Diver Uncomfortably Cold 88°F (31 °C) Shivering 86°F (30 C) ^ ^ ^ ^| — Rest mg 90 Working 30— Diver Will Overheat Unprotected Diver Comfortable During Moderate Unprotected 80 25 — Diver At Rest Chills In Work Wet 1-2 or Dry Suit Diver's 20 — — Hours 70 Underwear Or Wet Suit Required Pain 60°F (15°C)^ Dry Suit Required Over 60'; Wet ' f. 60 15- Suit For Short Duration Dives Less Than 60' 10 — Death Within One Hour 40°F(5°C)^ 5 — Unprotected Diver 50 — 40 Hot Water Suit Or Variable Volume Dry Suit Required 30 Fresh ^ Water <4 Sea Freezing Point Water 5 Protection Usually — Needed Heated Suit Source: 10-20 NOAA Diving Manual US Navy (1985) —October 1991 Diving Under Special Conditions Figure 10-11 Diver Tender and Standby Diver in Surface Shelter as soon as possible. In cold-water diving situations that require repetitive dives, it is even more important conserve the diver's body heat, to maintain an adequate fluid balance, and to select the diving dress to carefully. and nutrition are essential to providing cold-water divers with the energy necessary for this type of diving. A diver should have a minimum of 6-8 hours of sleep before the dive. Care must be taken to avoid dehydration, which can interfere with the Adequate rest body's thermal regulatory mechanism. Careful planning is thus of the utmost importance in all cold-water diving. WARNING If a Diver Is Extremely Cold, the Decompression Schedule Should Be Adjusted to the Next Longer Time UNDER DIVING 10.9 ICE In addition to the problems and limitations of diving water (see Section 10.8), there are specific precautions that must be taken when diving under ice. in cold Diving under ice is extremely hazardous and should be Photo Doug Eiser done only by experienced divers who have been carefully trained. Most ice diving is done from large and relatively flat surface ice sheets that are stationary and firmly frozen to the shore. Even at many locations miles from the nearest land, these ice caps often offer a stable work- However, diving from drifting or broken dangerous and should only be done as a last resort. When the ice cap is solid, there is no wave action to the water; however, divers must constantly be on guard because the current beneath the entry hole can change quickly and dramatically without producing any noticeable effect on the surface. In most cases, the absence of wave action produces good underwater ing platform. ice is although under-ice diving operations conareas characterized by river runoff or heavy visibility, ducted in plankton may be associated with conditions of reduced visibility. To drill enter the water through ice, divers should mine and water depth. If conditions are the area around the site should be cleared snow and the approximately 3 size of the entry by 5 fully dressed divers to If no shelter works first site to deter- ice thickness satisfactory, of through the ice at the a small hole is determined. m) accommodated be feet (0.9 by 1.5 hole of allows three at one time. used, a triangle-shaped entry hole the diver's tasks, so that they will understand the diver's movements and be able gency. A — NOAA Diving Manual to respond quickly in an emer- safety line should be tied to the diver (not to the equipment) and the other end should be tied firmly to a large fixed object on the surface. Excursions under the ice should be well planned, and the distance to be away from the entry hole should be kept to a minimum; under normal circumstances, this distance should be limited to 90 feet (27.4 m) and should be extended to as much as 250 feet (45.7 m) traveled under the ice only in unusual circumstances. Longer under-ice excursions make it difficult for the diver to get back to the entry hole in an emergency and increase the difficulty of searching for a lost diver. If divers distances under the ice, for emergency ascend to the tain positive conserve best. October 1991 A In all diving operations under ice, there should be one surface tender for each diver and at least one standby diver (Figure 10-11). While the diver is in the water, the tender must be attentive both to the diver and surface conditions, such as deteriorating weather or moving ice. Tenders should be briefed on air, exits. travel long additional holes should be cut Divers overhead must lost under the ice cover ice should immediately, main- buoyancy, relax as much as possible and wait for assistance. to 10-21 Section 10 WARNING divers from the wind and, together with a small porta- ble heater, can provide relative comfort in these severest Divers Lost Under the Ice Should Ascend to the Ice Cover and Wait Calmly to Conserve Air. They Should Not Search for the Entry Hole of diving conditions. 10.10 KELP DIVING Kelp is found and temperate in dense beds along many of the colder coasts of the world. In the United States, To aid the diver to return to the entry hole, a bright these plants are found along the shore regions of the light should be hung just beneath the surface. For west coast. Kelp beds or forests are widely diversified it is both geographically and as a function of depth and usually the only item required beyond those used in temperature. Different varieties grow in different zones and support an incredible variety of sea life. Kelp will attach itself to practically any substrate (i.e., rock, concrete, steel, wreckage, etc.) and will often form a treelike structure, the base of which is a rootlike holdfast that provides a secure anchor and a home for many organisms. There is generally an area of open water night diving under ice, this light is a necessity; day-time operations. However, since cold water shortens the life of batteries, homing beacons and strobes should be checked before use. Because direct ascent to is impossible when under the means of determining direction often is the surface ice, a rapid critical. In shallow water, detours are often necessary to circumvent the 'keels' (thickened areas) built up beneath the Also, because of the absence of waves, there are no ice. ripple patterns on the bottom to aid in orientation. these reasons, the use of a tether For absolutely essential is under-ice diving. in If there is a failure in an ice diver's primary breath- between the stipes originating from one holdfast. A diver can swim between the stipe columns just as a hiker can walk between the trunks of trees in a forest on the land. Hollow floats or pneumatocysts are found at the base of the blades or fronds on many of the larger, longer kelp plants. These floats cause the fronds to tem, notify the buddy diver, and exit to the surface up and keep the stipes relatively upright. The floating fronds form a canopy when they have grown with the buddy diver. Because buddy breathing sufficiently to reach the surface. In ing system, the diver should switch to the ficult in cold water, all divers backup is sys- dif- should practice buddy breathing before making excursions under the ice. Octo- pus regulators should not be used in cold water as buddy breathing because the float many instances, this rapidly growing canopy becomes very dense and can be several feet thick on and near the surface. The canopy will usually have thin spots or openings located stage randomly throughout the area, and these thin spots or of these regulators tends to freeze up. If a diver's openings provide entry and exit points for divers. These exposure suit tears or floods, the diver should surface thinner areas are easily seen from below the surface immediately, regardless of the degree of flooding, because the chilling effects of frigid water can cause because the light penetration thermal shock within minutes. Surface-supplied tethered light area exhales, the rising substitutes for diving tions is becoming more popular because it in first under-ice opera- eliminates the need for safety lines and navigation lights and provides unlimited air. The full- face masks or helmets of most surface-supplied diving systems provide additional protection for the diver's face and provide the capability for diver-to-diver and under such a bubbles usually float the kelp outward to form an opening that large to enable the diver to surface. exercised when the diver's head may is sufficiently is Care should be out of the water, back and fill in the hole and surround the diver. Although the kelp will not actually wrap itself around the diver, divers who twist around because the kelp float These added features must be weighed carefully against the burden of the added logistic support required to conduct surfacesupplied diving. If the advanced dry suits now availa- and struggle may become entangled. Training ble (see Section 5.4.5) are used, the surface-supplied snag and tangle diver can spend long periods under the ice in relative diver diver-to-surface communication. safety If for and comfort. more than 1 is constructed over the entry hole (Figure 10-11). Such a shelter will protect both surface support personnel 10-22 diving and is and necessary to master the skills to in kelp make entries exits easily. Equipment that is not relatively streamlined can in the kelp becomes entangled, that kelp scheduled to last or 2 days, a tent or shed should be an under-ice dive operation much in these areas is better; in addition, as a diver positioned is it and cause problems. is If the important to remember designed to withstand the pulling force of wind, waves, and currents and consequently that the tensile or stretching strength of the plant is very great. Divers wishing to break a strand of kelp should fold to develop a sharp angle NOAA in the stipe. Pulling Diving Manual it on the —October 1991 Diving Under Special Conditions may kelp will result in frustration and Nicking the kelp with a sharp object cause panic. separate the will streamlined surface to the kelp, since anything that extends out from the body will Swim probably snag. kelp easily, but using sharp objects such as knives fins needs to be done with care because of the proximity of The end of the strap on the inside rather than the outside of the buckle. Taping the loose end of a strap to the main way to get free is to remain calm and to pull the away carefully with a minimum of movement. diving knife on the inside of the calf rather than any- regulator hoses and other critical paraphenalia. easiest strands When working from a boat, it best to anchor in an is opening so that the wind or current will drift the boat back on the anchor line to a second opening in the kelp. Divers may also anchor outside the kelp and swim in to do their work. If anchor full be will the boat is anchored in the kelp, the of kelp that must later be removed with adjustable heel straps should have the loose portion of the strap Entry through the kelp making is best accomplished by finding a feet-first, feet-together entry rather than a headfirst or backroll entry that could easily lead to entanglement. through the canopy and into Once through important to get the open water between It is the surface canopy, the diver can swim with comfort in the forestlike environment. As the diver swims along, it is important to watch for bags, and tools of making an opening. When the diver surface, the arms should be raised over approaches the the head so that any kelp that may be encountered can be moved to the side easily as the diver moves upward into the hole that has been opened. Once on the sur- face, the diver should stay in the vertical position and should not turn around; this helps to avoid entanglement. Submerging can be accomplished easily by either exhaling and sinking or raising the arms overhead, which forces the body deeper down into the water. Smooth and slow movements make this maneuver easy and safe. The diver who wishes to travel on the surface of a kelp bed to get back to the shore or boat has several choices. If the diver is desired location. Each step move streamlined game kinds should be organized to all it is remember that kelp floats and that, possible to achieve flotation by using Under windy the kelp for support. conditions, divers should approach the stern of a small boat to avoid being pressed by the boat's movement into the kelp and becoming entangled. The various forms may grow so that the taller may be found growing over a of kelp kelps such as Macrocystis forest of Pelagophycus canopy of kelp (or elk kelp). This will further reduce the second lower light level but be easier to swim through than the surface canopy. All kelp beds are influenced by wind, currents, may disappear from surge, and major beds view in a swift current because they are held 45-degree angle. This has its and surface down at a advantages because the kelp will stream with the current and thus may be used as a navigational aid during the dive. Achieving comfort and efficiency in diver along who is kelp diving Having the result of training and practice. equally well trained is a is buddy also extremely important. 10.11 WRECK Wreck diving subjects the diver to DIVING hazards that are found in cave or many of the same ice diving. In the past easy to 20 years, wreck diving has evolved into an activity in steps to the requiring both specialized equipment and training, par- sufficiently skilled, use a series of breath-hold dives to in a present minimal problems. will bles to assist in Wearing the fashion and that inflated buoyancy compensators, the light areas that signal the thinner areas in the kelp bed. Surfacing slowly permits a diver's exhaust bub- solution. through the kelp or over the kelp in a pinch, a thin area and good also a where on the outside of the body is also a snag reducer. Kelp divers should remember that they want to move Divers should also surgically. the stipes. is it is requires the diver to sur- ticularly in the case of deep wreck diving. Regardless face through an opening in the kelp and to take a of purpose (lobstering, artifact collecting, photogra- breath or two phy, or exploring), true wreck diving involves the diver in preparation for the next step. Another useful technique, often called the Kelp Crawl, resem- entering the wreck. and involves keeping the body on the surface above the kelp canopy and using the arms enclosed space of the wreck that necessitates the addi- bles the 'dog paddle' to pull the diver across the top of the kelp as the diver's make narrow body across the top of the floating kelp canopy. The arms should reach across the kelp in an extended position and then the hands should grasp the kelp and press down as the body is pulled over the kelp. It is important to present a fins a October 1991 flutter kick to slide the — NOAA Diving Manual It is the act of penetrating the equipment and training. Most intact wrecks are at depths tional in excess of 80 feet (24.4 m), because those in shallower water have been destroyed either by storms or because they were navigational hazards. After arriving on the bottom at the wreck site, the first team of divers must check the anchor of the boat for security and to ensure that the 10-23 Section 10 anchor line will not chafe. ally has fair to however, visibility good may The path visibility. wreck usu- the return trip, be reduced dramatically because the divers have stirred up the (rust) into a On silt from the walls and exposed and ferrous oxide steel plates of the wreck. The reduced visibility and the confusion and anxiety caused by the many passageways, entrances, chambers, bulkheads, and tight spaces require that wreck divers use a penetration line such as a braided 1/8-inch (3.2 mm) nylon line on a reel. The line should be tied off at the wreck's entrance, payed out during entry, and reeled in during return. If the line is lost cut, the diver should pause, allow the silt to settle, or and regain his or her composure before attempting to return to 10.12 DIVING AT HIGH ELEVATIONS The U.S. Navy Standard Decompression Tables, No-Decompression Table, and Repetitive Dive Tables were calculated and validated on the assumption that the diver started from and returned to an ambient atmospheric pressure of 1 atmosphere absolute (ATA). Consequently, these tables do not account accurately for dives conducted from ambient environments hav- ing pressures less than corrections are now 1 ATA. Two sets of tables or use for calculating diving sched- in Boni/Buehlmann tables and the Cross corrections, as modified by Bell and Borgwardt. These are described below, and represent- ules for altitude diving: the ative dive profiles based on these tables are compared. the entrance. Placing the faceplate of the underwater light into the silt will reduce the ambient light level adapt partially to the darkness. This will facilitate the detection of any surface light coming into the passageways and thus aid in 10.12.1 Altitude Diving the identification of possible exit paths. and and allow the diver's eyes to Because of depth, the use of twin scuba cylinders, Currently in The Boni/Buehlmann sion, his colleagues Tables Use tables were developed by Boni (1976) and include no-decompres- decompression, surface interval, and residual together with a pony bottle with a separate regulator, nitrogen (called the 'repetitive timetable') tables for recommended as standard wreck diving equipment. some instances, a spare air supply and regulator each 1,640 feet (500 m) of altitude up to 10,496 feet is In should be placed outside the wreck. These precautions are necessary in case the diver becomes entangled or needed unexpectedly. During wreck diving, entanglement may be caused by objects such as monofilament fishing line, fish nets, collapsed bulkheads, or narrow spaces. A bag containing appropriate tools for artifacts, liftbags, and an upline should be carried to reduce the risk of entanglement that prevails if this equipment is carried by or attached to the diver. Most instrumentation can be strapped to the underwater light; a set of decompression tables may be decompression is attached to the light housing, reducing the amount of equipment carried by the diver but ready access to the tables if still decompression permitting is required. Although a diver inside a wreck may be tempted to breathe in the air pockets produced by previous divers, this practice should be avoided because the partial pressure of oxygen in these pockets is usually quite low and hydrogen sulfide may be present. The water temperature around a wreck is usually low, and divers must therefore dress properly. Variablevolume dry suits or 1/4- to 3/8-inch (6.4 to 9.5 mm) wet suits should be used in water temperatures of 50 °F (10°C) or less (see Section 5.4). Extreme caution must be taken not to snag the suit or equipment on the sharp objects commonly found in wrecks, such as decayed wooden decks or corroded metal bulkheads, because these hazards are frequently overgrown by algae, sea polyps, or other marine growth. 10-24 (3,200 m). The The results of feet (2,000 m) have wet dives (Boni et al. 1976). tables to 6,561 been tested on humans in 94 non-repetitive dives to depths between 52 and 98 feet (15.8 and 9.1 m) and for bottom times as long as 40 minutes were reported. The results of 184 dives under approximately the same conditions were also reported by these authors. No symptoms of decompression sickness of any kind were observed during these 278 dives. These tables require a routine decompression stop for 3 minutes at 6.6 feet (2 m) for dives within the no-decompression limits. Consequently, dives used for testing the tables included a all decom- pression stop for 3 minutes or longer. The Cross corrections to the U.S. Navy tables were Navy decom- developed to convert the standard U.S. pression tables to tables that could be used in altitude method was first developed in 1965 by Dr. Jon Pegg but was never published. A similar set of corrections was later developed by H. J. Smith, Jr. (Cross 1967) and was subsequently published in greater detail (Cross 1970). The Cross method involves determining a theoretical ocean depth (TOD) by multiplying the dive depth by the ratio of the atmospheric pressure at sea level to that at the altitude at which the dive will be made. The TOD and the actual bottom time in the U.S. Navy tables are then used to determine the altitude diving schedule. The theory of the Cross corrections has been examined in detail (Bell and Borgwardt 1976); the correction factors used in the Cross tables do not apply to the diving. This adjustment NOAA Diving Manual — October 1991 Diving Under Special Conditions Table 10-1 Comparison of Differences in Time Limits (in Minutes of Bottom Time) for No-Decompression Dives used critical tissue pressures On safety criteria. in the Navy tables as the other hand, in the cases studied, the Cross corrections always 'failed' on the conserva- Measured Depth (ft) tive, i.e., safe, side. ter research University of California underwa- teams have used the Cross corrections as a in California lakes and in Lake Tahoe, guide to diving Nevada (elevation 6200 (1890 m)). Diving sched- feet ules used have included procedures for repetitive dives per day up to three USN Cross Boni/Buehlmann Tables Tables Tables (min) (min) (min) 60 + 60 40 40 15 80 100 25 6 (+ 3 at 2 m) 25 10 4 120 15 5 ( 3 at 2 m) + 3 at 2 m) Decompression ( depths of 130 feet (39.6 m). to Both no-decompression and decompression dives have been conducted; no reported cases of decompression In this 6000 example, dives are assumed to take place feet an elevation at of (1829 m). sickness have occurred in several hundred dives. Adapted from 10.12.2 Comparison of Existing Tables 2. A comparison of the no-decompression limits given by the two altitude correction methods and the U.S. Navy tables is shown in Table As this Navy 10-1. shows, both the Cross corrections and the 3. table those predicted by the Boni/Buehlmann (1979) altitude of the dive site or the next greater altitude is found in the top The entry corresponding row of the table. to the intersection point of the depth row and the altitude column marks tables the yield no-decompression limits that are longer than in The NOAA "theoretical ocean depth" (TOD), which, according to the assumptions of the Cross theory, although yields a probability of decompression sickness both cases the no-decompression limits are less than equivalent to that for the altitude and measured tables, those that apply to sea level. depth of the dive. There have been no reported cases of decompression 4. The TOD and the total bottom time, including any sickness in divers using the Cross corrections on dives residual nitrogen time accrued from repetitive from an altitude of 6200 feet (1890 m). The Cross dives, are then used with the U.S. corrections therefore appear to be safe. Several labo- The ratories are continuing to study this problem, but at be for a sea-level exposure. Each time a dive is planned, the TOD equivalent is substituted for this time the true bends threshold for these tables has not been established. Consequently, altitude diving, and particularly decompression altitude diving, should be that 5. performed using conservative assumptions and special precautions to ensure access to emergency treatment. dive schedule Navy calculated exactly as tables. would it measured depth. The ascent shown 6. If is in rate at altitude Table must be reduced, as 10-2. a decompression dive is conducted (which is not recommended), the depth of the decompression 10.12.3 Recommendations stops for Altitude Diving recommended for general use within the no-decompression limits. Although The Cross corrections are decompression dives have been conducted using the Cross corrections, they have been relatively few and have not involved depths greater than 130 from an elevation of 6200 decompression dives feet at altitude feet (39.6 m) (1890 m). In general, should be avoided. must also be corrected, as shown in Table 10-2. Example: Two dives are to be conducted at an altitude of 6000 feet (1829 m) on a no-decompression schedule. The first is to be to 80 feet of fresh water (ffw) (24.4 mfw) for 20 minutes; the second to 60 ffw (18.3 mfw) for 25 minutes. Find the surface interval required to complete the dive schedule in minimum time. Solution: 10.12.4 Calculations for Diving at Altitude The Cross correction tables, as modified by Bell and Borgwardt, are shown in Table 10-2. This table identical to that presented by Cross that it has been modified to and rate of ascent. The table 1. is is 970), except ( account for fresh water — NOAA used as follows: Diving Manual 10-2, the theoretical ocean depth in fsw (ffw) (24.4 mfw) in a lake whose surface altitude is 1 The depth of the planned dive is found in the column on the left marked "Measured Depth." October 1991 From Table that corresponds to a depth of 80 feet of fresh water 97 fsw (29.6 msw) and that for a depth of 60 feet of fresh water (18.3 mfw) is 73 fsw (22.2 msw). 6000 The feet is sea-level decompression table (Appendix B) must msw) and 80 fsw therefore be entered at 100 fsw (30.1 (24.4 msw), respectively. A 20-minute dive to a TOD 10-25 Section 10 Table 10-2 Theoretical Ocean Depth (TOD) fsw) at Altitude for a Given Measured Diving Depth (in i Measured Altitude in feet 1000 Depth* 2000 4000 3000 TOD 10 20 30 10 20 29 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200 210 220 230 240 250 39 49 59 68 78 88 98 107 117 127 137 146 156 166 176 185 195 205 215 224 234 244 10 20 30 40 10 11 11 21 22 33 44 54 65 76 87 98 109 120 23 34 45 56 68 79 90 102 113 124 135 147 158 169 31 42 52 63 73 84 94 105 115 126 136 147 157 168 178 189 199 210 220 51 61 71 81 91 101 111 121 131 142 152 162 172 182 192 202 212 222 233 243 253 131 141 231 241 5000 fsw in 12 252 262 261 271 281 272 282 293 9 18 27 9 17 26 34 43 51 9000 10000 63 76 88 73 85 97 109 122 134 146 158 170 182 195 207 219 101 114 126 139 152 164 177 190 202 215 227 240 253 265 278 231 243 255 268 280 292 304 14 27 13 26 39 52 66 79 92 105 118 51 61 152 164 176 187 199 211 223 234 246 258 270 8000 13 25 38 24 36 49 141 192 203 214 226 237 248 260 7000 at Altitude 12 23 35 47 59 70 82 94 105 117 129 152 163 174 185 196 207 218 228 239 250 181 6000 41 55 68 82 95 109 123 136 150 164 177 131 144 157 171 184 197 210 223 236 249 262 276 289 302 315 328 291 303 316 14 28 43 57 71 85 99 113 128 142 156 170 184 199 213 227 191 205 218 232 245 259 273 286 300 314 327 241 255 270 284 298 312 326 340 355 341 Stops 10 10 20 30 40 50 10 19 9 18 31 41 51 10 20 30 40 49 29 38 48 28 37 46 35 44 62 59 57 55 53 21 8 15 23 30 41 8 16 24 32 40 49 47 8 16 25 33 « 7 14 7 15 22 21 38 29 37 28 35 46 44 42 Ascent Rate 60 is not gauge depth. Table takes into account the effect of water density. The zero feet altitude column is for a freshwater lake at sea level. According to Bell and Borgwardt (1976), these tables are theoretically correct (although they do not account for seasonal or daily barometric changes) but are still untested. Adapted from Bell and Borgwardt (1976) * Measured depth diving in of 100 fsw (30.1 tive for a msw) places the diver in the F repeti- group (Appendix B). The no-decompression limit TOD of 80 fsw (24.4 msw) is 40 minutes (Appen- dix B). Therefore, the diver can have no 15 minutes of residual nitrogen time second dive; the diver move from the F group is in the to the C C when had taken place will maximum be passing through on the elevation the diver trip out. more than starting the repetitive group. 10.12.5 Correction To group requires 2 hours Neither gauge actual depth. is often Depth Gauges nor capillary depth gauges pro- oil-filled 25 minutes. In high-altitude diving, the dive off vide accurate depth indications and 29 minutes. A dive schedule for an altitude dive at 6000 feet (1829 m) would therefore be 80 fsw (24.4 msw) for 20 minutes, 2 hours and 29 minutes of surface interval time, followed by a 60-fsw (18.3 msw) dive for last at the Oil-filled when used at altitude. depth gauges are designed to read pressure of 1 ATA. At reduced atmospheric feet at a pressure, the gauge will read less than zero (unless there is a pin that stops the needle at zero); in the water, such a will give a reading that is shallower than the The depth readings can be corrected by followed by a trip through mountain passes at an elevation adding a depth that higher than that used in the calculation. In this event, the atmospheric pressure at the altitude site and it is good practice 10-26 to calculate the last dive as though it 1 ATA. Table is equal to the difference between 10-3 shows NOAA mean atmospheric Diving Manual pressures —October 1991 4 Diving Under Special Conditions Table 10-3 Pressure Variations with Altitude Accordingly, special precautions and extra plan- light. ning are required for night dives. Altitude, Pressure, Pressure, Pressure, ft mmHg psl atm* Oil-filled 760.0 732.9 706.7 681.2 656.4 632.4 609.1 586.5 564.6 543.3 522.8 502.8 483.5 464.8 446.6 429.1 412.1 395.7 379.8 364.4 349.5 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 11000 12000 13000 14000 15000 16000 17000 18000 19000 20000 14.70 14.17 13.67 13.17 12.70 12.23 11.78 11.35 10.92 2.37 3.53 10.51 9.73 9.35 8.99 8.64 8.31 7.97 7.66 7.35 7.04 6.76 night to have correct marking lights that are clearly 6.75 7.73 8.72 9.67 10.58 11.47 12.35 13.16 13.98 14.76 15.54 16.25 16.96 17.67 18.28 0.500 0.479 0.461 light is recom- Predive checks are particularly important at night, because the limited precludes even a cursory visibility inspection of equipment once in the water. Night diving in fog or heavy rain should be avoided because it is easy for the diver to lose sight of the lights on the dive boat or those carried by other divers. Each diver should carry charge sufficient to pated for the dive. the diver in NOAA light or small strobe mended. U.S. standard atmosphereSource: chemical attached to the anchor line or downline (1979) A last a reliable diving light with a longer than the time antici- second light advisable, because is common. The light should be secured to a manner that permits the illumination of failure of lights * A can see under water. 5.70 0.521 which case other steps are approIt is also important at liveboating, in visible to other vessels in addition to a light the divers 4.61 0.772 0.743 0.715 0.688 0.662 0.636 0.612 0.588 0.565 0.542 The boat priate (see Section 8.10.1)). 1.22 0.801 especially critical at night. is must be secure before the diver enters the water (except ft when 1.000 0.964 0.930 0.896 0.864 0.832 10.11 Anchoring gauge correction, is A watches, gauges, or navigational aids. chemical light should be taped to the snorkel or tank valve for under- and the corrections necessary at various altitudes oil-filled for Because of the reduced density of the trapped in the capillary gauge at altitude, less water pressure is air required than at sea level to compress the air to a given volume. As a water and surface The gauges. result, the capillary gauge will indicate a depth greater than the actual depth. Because of the question about the accuracy of these gauges, a meas- visibility in case the dive lights fail. team should be careful to maintain dark adaptation before and during the dive (see Section 2.8.2). Every effort should be made to avoid shining diving lights directly into the eyes of crew members, both before and during the dive. Once in the water, it is easy to keep track of a buddy's light at entire night dive night; however, one diver may occasionally lose another because the glare of the light being held prevents seeing ured downline should be used. the buddy's light. In this case, the divers should turn off or otherwise shield their lights momentarily, adjust 10.12.6 A Hypoxia During Altitude Diving diver surfacing from an altitude dive from a breathing gas sure low. is As which the oxygen in relatively high to an atmosphere may a result, the diver is moving If a partial pres- in buddy's their eyes, locate the ately turn their lights which it is experience symptoms of hypoxia and breathing difficulty for a period after the team is left and then immedi- light, back on. with only one light, the dive should be terminated. Lights may also be used to signal the surface; sweeping the light in a wide arc over the head is the standard 'pick me up' signal. At night, a whistle or chemical flare should also be carried in case of light dive (see Section 3.1.3.1). failure. Shore entries are more hazardous 10.13 NIGHT DIVING Night diving exposes the diver to an entirely different aspect of the underwater world. Marine more or less colors than abundant and appear is familiar to the diver during the may be to be of different day may appear changed to the extent that orientation October 1991 life the case during the day. Areas that are landmarks may be difficult — NOAA at night because such features as rocks, algae, holes, waves, and rip currents are not easily seen. Entries from boats, piers, and locating familiar even with good Diving Manual artificial and other surface platforms require special caution so that the diver avoids hitting objects on or below the surface. If a shore exit requires a particular approach because of in-water obstacles, two shore lights in a line can serve as a navigational aid for divers. When possible, experi- enced night divers should be buddied with novice night 10-27 Section 10 Making divers. the entry at dusk rather than at night reduces some of the problems of night diving. When- ever possible, the area to be dived by night should first such operations are undertaken at altitudes in tions (see Section 10.12). be dived by day to provide the divers with entry and exit experience. If tion. excess of 1000 feet, divers should take special precau- Three major conditions must be considered when dams planning dives at in the northwest (or any other) region: NOTE Water temperature (1) (2) Visibility Decompression diving is more hazardous at night than during the day and should be avoided if possible. To be conducted safely, night decompression dives need considerable advance planning. Flow (3) velocities. Water temperatures may vary from slightly ing in winter to almost 80 °F (27 °C) in above freez- summer. Divers should be protected from the elements before diving and during surface intervals in both warm and cold seasons, because of the potential for heat exhaustion or Most research diving when rivers and melting snow and fish migrations hypothermia (see Section In night decompression diving, lights decompression line are marking the necessary to ensure that the divers conduct their in-water decompression near the dive boat or other platform. Divers operating in a decompression mode should not swim out of sight of lines or lights that will pression line guide them back to the decom- and dive platform. dams occurs during at from rains swell occur. The spring runoff produces low underwater vis- DIVING IN from silt [0-0.6 Hydroelectric dams across rivers in the northwest United States incorporate bypass and collection systems for the protection of migrating fish species such as salmon and steelhead trout (Figure 10-12). Because fish passage research is conducted at many of these dams, NOAA and other scientist/divers are often required to inspect, maintain, install, or retrieve research gear such as flow meters and fish guidance and passage devices. If time and circumstances permit, a shutdown and de-watering of turbine intakes, gatewells, and fish ladders is the safest and most efficient manner for performing work on dam bypass and collection facilities. However, safe and efficient diving operations can be performed within and on the upstream and downstream faces of dams even when these are ing. The agency operating the dam inspector who still operat- supplies a diving coordinates such dives, because strict cooperation between the divers and the powerhouse operations staff is mandatory to ensure proper clear- ances for turbine shutdown and flow gate closures. 10.14.1 Diving at The Dams safety aspects of diving at to those prevailing in cave, dams are comparable wreck, and over-bottom in the carried by flooding waters. In in clear water, the DAMS AND RESERVOIRS m] Snake River) warmer months, algae blooms may cause low underwater visibility. Even ibility (e.g., 0-2 feet sediment disturbed by divers reduces visibility so that the 10.14 10.8). the spring freshet, small amount of natural light penetrating the gatewells is reduced. Although diving minimally effective, the problems associated with low visibility at dams can be overcome lights are only by careful planning, studies of the blueprints and plans dam, and familiarization with the research devices of the to be used during the dive. Objects can be recognized by touch and orientation maintained, even in zero underwater visibility, if the diver is familiar both with the gear and the dam's structures. The velocity of the flow and the force of the suction through screens or orifices dams can be eliminated or controlled by coordinat- at ing the diver's actions carefully with dam operations personnel before the dive. When bypass systems become fouled or clogged by sometimes are required river debris, divers dam gatewells to clear the system's orifices. to enter The haz- ards of gatewell diving can be reduced by taking ade- quate precautions to ensure that the influence of suc- caused by the large hydrostatic head, tion, is avoided which eliminate the need for buoyancy compensators, should be worn to avoid the danger of loose equipment becoming caught (see Section 5.4). Procedures are much the same as those for umbilical diving, whether the diver is using surface-supplied air or scuba cylinders. At a miniat the orifice. mum, Variable-volume suits, a tender line to the diver should be used for diving, contact and signals, although hard wire communica- dam dam and many of the same procedures are used in diving. Predive planning by the dive team with personnel will help to ensure a safe diving opera- transport the diver to and from the orifice level and the 10-28 tion is preferred. A diver cage should be provided to NOAA Diving Manual — October 1991 Diving Under Special Conditions Figure 10-12 Cross Section of a Typical Hydroelectric Dam in the Northwestern United States Courtesy George Swan Figure 10-13 shows a diver ready to be lowered into a be performed in much the same manner as they are conducted when diving amid pools and boulders in dam rivers with relatively fast currents (see Section 10.15). dam, and intake deck of the a safety diver gatewell. Procedures to shut system immediately in the event of an be coordinated with the dam down is required. the bypass emergency should operations controller before Work on fish ladders (Figure 10-14) should be performed during off-season when the number of upstream adult fish runs is low and water flows can be cut off for a period of time, which permits the task to in the open impractical, and diving plete the task. diving tasks must be performed on the upstream dam, turbines and/or spillway gates must be shut down. Adjacent units should also be shut the dive. be completed When face of a Flows air. is On rare occasions this is then the only way to comladders appear quite turbulent in fish when viewed from above; however, baffles or weir walls safety and to reduce flows near the work can be transported to and from the the intake deck of the and crane. A level of dam by means down station. for Divers work and to of a diver cage boat or floating platform also is useful for the safety (standby) diver and equipment. Diving on the downstream face of a dam is handled similarly; flows are shut off to avoid sweeping the diver off station. Divers should avoid water contaminants, such as are regularly spaced perpendicularly to the flow, and spilled the water flows either over the top of each weir or routine operation and maintenance of through large rectangular orifices located byproducts generated by underwater cutting and welding. These contaminants can become concentrated in confined areas such as gatewells, where the water level may be 5 to 20 feet (4.6 to 6. m) below the deck of the dam. Before starting or continuing a dive, any contaminant discovered should be eliminated from the dive of the baffle wall. walls, (2.4 flows as When high 8.0 as mps) may be encountered with the orifices but to either side or may at the base diving in pools between baffle feet in per second be as low as 1.0 fps (0.3 mps) above the line of the orifice. By using safety lines and exercising caution, diving tasks October 1991 — NOAA (fps) areas directly in line Diving Manual may petroleum or lubrication products used 1 dams in the or gaseous 1 site. 10-29 Section 10 Figure 10-13 Diver Protected by be Lowered Into Figure 10-14 Cage and Ready Dam A to Fish Dam Gatewell in Ladder at a Hydroelectric the Northwest Courtesy George Courtesy George Swan water opening; (2) a pierlike structure set out from the shoreline that supports turbine pumps; (3) a combination pier/vault created by closing in the area under a pier with driven sheet piling or other material; 10.14.2 Diving at Pumping The impact Water Withdrawal and (4) a simple Sites single intake line extending to a depth of water withdrawal on populations of juvenile fish in the Columbia Basin of the northwest Swan arrangement of a water elevation. Some pump and or siphon with a below the low vaultlike structures may have trash rack bars in front of the fish screening. A good those seeking permits to install and operate water with- and stable work boat serves as the best diving sites and expedites diver travel between sites, but divers should be careful when entering the water from a small boat. Some sites with enclosed fish screens must be accessed by ladder or small crane. For such a diving task, tanks, weight belts, masks, and fins are lowered by lines to the divers once they are in the water; this procedure is drawals to reversed after the dive. United States Water is a major concern to fisheries agencies. withdrawn from the Columbia and Snake Rivers via pumps and siphons and is then used for is irrigation, industrial applications, drinking water, ther- mal cooling, fish and wildlife propagation, and other domestic needs. Before water can be withdrawn from these rivers, the U.S. ly, Army Corps of Engineers requires install fish protective facilities. Periodical- divers are required to inspect fish screens at water withdrawal sites to monitor the condition of the screening and the status of compliance with established fish screening criteria. Several basic types of water withdrawal sites are common: 10-30 (1) a vaultlike structure with a screened under- platform for accessing most withdrawal Diving safely if in and around pump intakes can be performed and the neces- certain hazards are recognized sary precautions are taken. In general, intake velocities are not high enough to present a suction hazard, although pumps should be shut down, if possible. To perform an inspection during the pumping season, NOAA Diving Manual —October 1991 Diving Under Special Conditions however, the approach velocities ured while the pumps may have to be meas- are operating. Surface air supply when hoses and safety lines should