Sight Search

Caissons, Compressed-Air work and Deep Tunnelling

By David Kenyon, Glenn Butler and Richard Vann |PHOTO COURTESY OF LIFE SUPPORT TECHNOLOGIES |Alert Diver Magazine

Some of mankind’s most amazing civil-engineering structures are underground tunnels and bridge foundations below the water table. During construction, the working spaces, or caissons, are pressurised with compressed air to keep out groundwater, and laborers (known as sandhogs) pass though pressure locks into and out of the caissons. In the 19th century, progress was rapid until the workers were afflicted with a mysterious condition called “caisson illness” when they returned to atmospheric pressure. The Brooklyn Bridge was completed before we learned how to prevent and treat the pain, paralysis and sometimes death due to what is now recognised as decompression sickness (DCS).

Caissons are dug vertically into bedrock to support bridge abutments, while tunnels are horizontal and used for roads, railroads, subways, water and sewage. Tunnels, formerly dug by gangs of sandhogs using picks, shovels and explosives, are now dug by tunnel boring machines (TBMs), which have giant rotating cylinder heads with toothed “faces” that cut through rock and muck as the TBM is forced along. In favourable rock formations, only the space in front of the TBM face is pressurised, and it’s only occupied for maintenance and replacing teeth. This limits pressure exposure and vastly improves safety.

IMPROVED TUNNELING EFFICIENCY AND SAFETY

When the 165-foot pressure limit for compressed air is exceeded, alternative gas mixes must be breathed to reduce the incidence of nitrogen narcosis, oxygen toxicity and DCS. TBMs can accomplish this with shorter working and decompression times. The foundation for these improvements was laid in the 1960s when deep diving and decompression research expanded in response to the need for offshore oil, particularly with the Organisation of the Petroleum Exporting Countries (OPEC) oil embargo of the 1970s.

Saturation diving — in which divers remained at pressure for a day or more such that their bodies became equilibrated with the gas they breathed, and they could remain at depth without incurring additional decompression obligations — extended divers’ reach in depth and time to 1,000 feet of seawater (fsw) for weeks with few pressure-related injuries. Experience taught how heliox (helium-oxygen) and trimix (helium-nitrogen-oxygen) could be used at greater depths, how nitrox (nitrogen-oxygen) with more than 21 percent oxygen (oxygen-enriched air, or OEA) could be used at intermediate depths and how 100 percent oxygen could be used during shallow decompression. These techniques made for enormous improvements in productivity and safety.

Surface decompression (decanting) is another technique used widely in military and commercial diving to limit time in the water, where keeping warm is difficult. The diver remains at about 40 fsw before ascending to the surface in 1 minute, entering a deck decompression chamber (DDC), being pressurised back to 40 fsw in the DDC, breathing oxygen to clear inert gas and decompressing to the surface. Surface decompression is also useful in tunnelling and caisson projects in which workers decant from an intermediate pressure of about 18 pounds per square inch gauge (psig) or 40 fsw, dress comfortably, enter a DDC and are repressurised to 18 pounds per square inch (psi) for decompression.

Another useful method developed in the 1960s and ’70s was saturation-excursion diving, in which divers lived in an underwater habitat or DDC and made excursions to greater depths and then returned (with or without decompression stops) to the saturation depth. Decompression to the surface was postponed to a later day. For deep excursion depths, trimix might be used as the breathing gas with careful monitoring of the oxygen exposure history to avoid oxygen toxicity.

TUNNELING AROUND THE WORLD

The use of mixed gases for higher-intervention-pressure civil-engineering projects is more common in Europe and Asia than in the United States. Projects include deep shaft sinking at 4.8 bar (157 fsw) in the Netherlands, 5.8 bar (190 fsw) for subways in Russia and Seattle and 6.9 bar (225 fsw) in a Netherlands tunnel. The Western Scheldt tunnel project in the Netherlands used trimix at 4.8 bar (157 fsw) with saturation-excursion decompression. Mixed gases and higher intervention pressures have improved productivity with good safety records.
There are many demands for air-pressurised caisson systems in Japan, especially for very deep and long tunnels in which new magnetic levitation trains will run between Tokyo and Nagoya. Recently begun, this work will require 10 or more years with pneumatic caissons every 18 to 25 miles for vertical support shafts. Although remotely operated excavators will perform the vertical caisson work, engineers must go inside the air-pressurized caissons once every day or two to maintain machinery.

WHAT MIGHT BE NEXT IN TUNNEL TECHNOLOGY?

With the exception of mixed gases, deeper decompression tables intended for diving and a few saturation interventions, the caisson/tunnel industry in the United States has been reluctant to adopt the methods of deep diving technology that would likely improve intervention safety and productivity. Transferring these methods to tunnel work is technically and culturally challenging, because increased work time at higher pressures would require decompression times longer than the four hours under pressure permitted by existing union rules. But several new methods for improving tunnel construction are possible.

Constant oxygen partial pressure (PO2) decompression

Careful oxygen management during a hyperbaric exposure can help optimise decompression time. Commercial and military diving operations with heliox have taken advantage of higher PO2s while at pressure. During decompression, divers typically shift to air at a lower pressure and decompress on air thereafter. The PO2 at pressure, which is determined by the breathing equipment and length of the exposure, is typically 1.1–1.4 bar at pressure but, for fire safety, not greater than 21 percent by volume during decompression. If no additional oxygen is added, the PO2 will drop proportionally to the pressure, and more decompression will be required, which is a significant disadvantage. But by using rebreathing equipment, oxygen may be added continuously during decompression to arrive at an optimal PO2, usually above 1.0 bar. The drawbacks of diving with rebreathers are requirements for multiple units, weight, awkwardness and accidental damage through “manhandling” within the lock or TBM. A hybrid approach would be to provide OEA (or mixed gas for deep dives) at pressure through an open-circuit mask or regulator mouthpiece. During decompression in the lock, workers would shift to a closed-circuit rebreather. A recirculating loop driven by a blower would condition the workers’ breathing gas (and the gas in the lock), remove carbon dioxide (CO2) and odors, maintain a constant PO2 and keep workers warm during decompression.

Replacing helium with crude neon

In 1972 scientists and engineers at Union Carbide’s Ocean Systems Inc. (OSI) perfected the use of neon as a replacement for helium in mid-range commercial diving to about 25 bar (815 fsw) and tested the concept in three open-water commercial dives to 640 fsw. Differences in decompression time between helium and neon were small, and a mixture of 33 percent neon (Ne), 33 percent helium (He) and 33 percent nitrogen (N2) appeared close to optimal for 160-250 fsw, with the oxygen (O2) percentage controlled during shallow decompression to avoid oxygen toxicity. Neon also has advantages over helium, including lower cost, warmer breathing gas, better drysuit thermal insulation and improved speech intelligibility.
As an economical alternative to the optimal mix, a lower grade of crude neon (50 percent Ne) containing N2 and O2 might be used without going through the costly scrubbing process to eliminate the other component gases that are needed anyway. Gas companies would tune their stacks to create an economical flow of crude neon in a range of about 50 percent Ne, 25 percent N2, 20 percent He and the balance O2 from the tail gas of their current “liquid air” distillation stacks. Once gas companies tuned their process for this economical mixture, special decompression tables would be developed.

Probabilistic decompression

Every dive profile has a finite DCS probability that can serve as a tool for comparing and selecting optimal decompression schedules. DCS probability also depends on factors such as thermal state and exercise that are very different between diving and compressed-air work. Understanding these effects will require further study based on recorded pressure-time profiles and DCS outcomes.

While there is no agreed-upon acceptable DCS probability, lower probabilities such as 0.025 percent are often considered appropriate for serious DCS such as paralysis, while 2 percent is more acceptable for joint pain. The lack of an absolute acceptable probability standard is addressed in the British concept of “as low as reasonably practicable” (ALARP). Since absolute elimination of DCS cannot be guaranteed, ALARP does not impose requirements that cannot be fulfilled, although preventive and protective actions appropriate to the risks are expected when possible.

CONCLUSION
Further progress in tunnelling technology through the application of advancements in diving research may be achievable. How long this might take remains to be seen. AD

Categories

 2023
immersion and bubble formation 2009 232bar 24Hours AGE AIDA Accident management Accidents Acid reflux Acute ailments Adam Sokolski Advanced courses Rescue diver Aerobic exercise After anaesthesia Aged divers Air Ambulance Air Quality Air consumption Air exchange centre Air hose failure Air supply Airway control Air Alert Diver December 2022 Alert Diver Magazine Alert Diver March 2023 Algorithms Alice Cattaneo Alice Modolo Alopecia Alternate Airsources use Alternater Air Source Alternative gas mix Altitude changes Altitude diving Altitude sickness Aluminium Oxide Ama divers Amino acids Amos Nachoum Anaerobic Metabolism Anilao Animal intelligence Animal life Annual renewal Antarctica Anxiety Apea Apex predators Apnea addicts Apnea Apnoea Aqua corps Aquatic creatures Aquatic life Aquatics and Scuba Diving Archaeology Argonaut octopus Argonauts Argon Arrythmia Arterial Gas Embolisms Arterial gas embolism Arthroscopic surgery Aspirin Audible signals Aurel hygiene Australian Flat backed Australia Aviation o2 BCD BHP BLS BOSS400 BWARF Baacterial infections Back adjustment Back pain Back treatment Backextensors Backmount CCR Badages Bag valve mask Bags Bahamas Bail out cylinder Balancing Bandaids Barbell back squat Barometric pressure Barotrauma Barry Skinstad Basic Life Support Basslets Batteries Beach entry Beached coral Becky Kaga Schott Becky Kagan Schott Beluga whales Bench press Bends Benign prostate hyperplasia Benzophenones Beth Neale Beyond Standards Big Sur Bilikiki Tours Biophysics Black Water Photography Black Blood flow Blood pressure Blood thinners Blue Desert Blue Wilderness Blue economy Blue heron Bridge Bluff Blurred vision Boat diving Boat etiquette Boat safety Boats Bobbit worm Boesmans gat Boesmansgat Bonaire Bone fractures Bouyancy compensators Bouyancy control device Bouyancy controls Boyle's Law Boyle\'s Law Bradycardia Brain Brandon Cole Breast Cancer Breath Hold Diving Breath hold diver Breath holding Breath hold Breath-hold Breathing Gas Breathing gas contamination Breathing oxygen Breathing Breathold diving Bright Bank Broken bones Bruising Bubble detection Bubbleformation Buddy Exercise Buddy checks Buoyancy Burn wounds Burnshield Burns Business B CCR CE markings CGASA CMAS CNS CO2 COVID-19 Updates COVID-19 COVID CPR CSI Cabin pressure Caissons diseas California Camera equipment Camera settings Cameras Cancer Remission Cancer treatments Cancer Cannabis and diving Cannabis Cape Diver Research Cape Nudibranchs Cape Town Dive Festival Cape Town Dive Sites Cape Town CapeTown Carbon Monoxide Carbon dioxide Cardiac Health Cardiac research Cardiaccompromise Cardio health Cardiological Cardiomyopathy Caribbean Carmel Bay Carribean Conservation Catalina Island Cave Cave diving Cave divers Cave diving Cave exploration Caves Cave Cenotes Ceotes Challenging Environments Chamber Locations Chamber Safety Chamber maintenance Chamber medical staff Chamber science Chamber treatment Chamber Charging batteries Charles' Law Charles\' Law Charles\\\' Law Charles\\\\\\\' Law Charles\\\\\\\\\\\\\\\' Law Charlie Warland Chemotherapy Chest compressions Children diving Chiropractic Chlorophll Chokka Run Christina Mittermeier Chuck Davis Chuuk lagoon Citizen Conservation Citizen sciences Citizen science Clean Air Cleaning products Cleeve Robertson Climate change Closed Circuit Rebreathers Closed Circuit Rebreather Clothing Cmmunity partnership Coastal diving Coastalexcursion Cold Water Cold care Cold sores ColdWater Cold Commercial Fishing Commercial diving Commercial operations Commercial schools Common consideration Common understanding Communication Compact Cameras Composition Compressed Air Compressed gas Compressor operators Compressors Concussion Congestive heart Faiture Consercation Conservation Photographer Conservation photography Conservation Contact lenses Contaminants Contaminated air Coping with cold Coral Bleaching event Coral Conservation Coral Reefs Coral Restoration Coral bleaching Coral preservation CoralGroupers Corals Core strength Corona virus Coro Coservation Costamed Chamber Courtactions Cozumel Cradiac valvular Crime scene Cristina Mittermeier Crocodile Crohns disease Crowns Crystal build up Crystallizing hoses Cubs Cutaneous decompression Cutting tools Cylinder Ruptures Cylinder capacity Cylinder handwheel Cylinder safety Cylinder valves Cylinder weight Cylinders DAN Courses DAN Europe DAN Profile DAN Researchers DAN hotline service DAN insure DAN medics DAN members DAN report DANTraining DCI DCS Decompressions sickness DCS theories DCS DEMP DM training DNA DPV DReams DSMB Daan verhoeven Dahab Dalton's Law Dalton\'s Law Dalton\\\'s Law Dalton\\\\\\\'s Law Dalton\\\\\\\\\\\\\\\'s Law Danel Wenzel Dangerous Marinelife Dauin island Dave McCowan David Doubilet Dean's Blue Hole Dean\'s Blue Hole Deco dives Decompression Illness Decompression Sickness Decompression Stress Decompression benenfits Decompression chamber Decompression illsnes Decompression ilness Decompression limits Decompression treatment Decompression Decomression sickness Decorator crabs Deep Freediving Deep diving Deep water exploration Deepest SCUBA Dive Delayed Offgassing Dennis Guichard Dental Depth limits Dever Health Diadema Response Team Diagnosis Diaphragms Diets Diopter Dirty water Discomfort Diseases Disinfectants Disinfection Disorientation Distraction Dive Accident Dive Action Dive Buddy Dive Centre Dive Chamber Dive Chmber Dive Computer Dive Destinations Dive Destination Dive Fitness # fit to dive @Dive health Dive H Dive Industry Dive Instruction Dive Instructor Dive Lights Dive Masters Dive Medical Form Dive Medical Dive Practices Dive Professionals Dive Pros Dive Rescue Dive Research Dive Safari Dive Safety Tips Dive South Africa Dive Taiwan Dive Training Dive Travel Wakatobi Dive Travel Dive accidents Dive bell Dive buddies Dive caves Dive centre rules Dive communications Dive computers Dive courses Dive cover Dive cylinder Aluminium Dive equipment Dive excursions Dive exercise Dive exeriences Dive experience Dive fitness Dive gear Dive heallth Dive health Dive in Africa Dive insurance Dive leaders Dive masks Dive medical insurance Dive medicals Dive medicines Dive medicine Dive operators Dive opportunities Dive planning Dive point Dive procedures Dive safety 101 Dive safety briefing Dive safety Dive safe Dive skills Dive staff Dive teams Dive travels DiveLIVE DiveTravel Diveleader training Diveleaders Divelights Diver Ethisc Diver Food Diver Health Diver Profile Diver Travel Diver education Diver infliencers Diver on surface Diver recall Diverover 50 Divers Alert Diversafety Divers Divesites Diving Divas Diving Equipment Diving Family Diving Fatalities Diving Feet Diving Helmets Diving Kids Diving Programs Diving Trauma Diving career Diving emergencies Diving emergency management Diving etiquette Diving fit Diving guidelines Diving history Diving injuries Diving science Diving suspended Diving Dizziness Dizzyness Documentary photography Dolphins Domestic Donating Blood Donation Doug Perrine Dowels Dr Rob Schneider Drift diving Drysuit diving Drysuit valves Drysuits Dur4ban Undersea club Durban Dynamic environment Dyperbaric medicines EAPs EAP EKG EMS EN standards Ear barotrauma Ear pressure Ear wax Ears injuries Eat fish Eco friendly Ecowise Education Electronic Elizabeth Bockheim Embolisms Emergency Action Plan Emergency Planning Emergency action planning Emergency contact Emergency decompression Emergency plans Emergency treatments Emergency underwater Oxygen Recompression Emergency Endurance Entry Envenomations Enviromental Protection Environmental factors Environmental impact Environmental managment Environmental stewardship Equalisation Equalise Equalization Equipment care Equipment failure Equipment hygiene Equipment inspection Equipment significance Evacuations Evacuation Evaluations Even Breath Evironmetaly friendly Exercise Exercising Exhaustion Exploration dives Exposure Protection Extended divetime Extinction Extinguisher Extreme treatments Eye injuries Eye protection FAQ Face computer Factor V Leiden Failures FalseBay Diving Fatigue Faulty equipment Feet Femal diver Female divers Fenivir Fetus development Field practice Filling stations Fillings Fin Foot Fins Fire Coral Fire Safety Fire extinguisher Firefighting Fires First Aid Equipment First Aid Kit First Aid Trainig First Aid Training First Aid kits First Aid Fish Identification Fish Life Fishing Fish Fit to dive Fitness Levels Fitness Training Fitness evaluation Fitness to dive Fitnesstrainng Fitness Flying Focus lights Food Footissues Foundations Fractures Francesca Diaco Francois Burman Fred Buyle Fredive Free Student cover Free diving Free flow Freedive Competition Rules Freedive Competiton Freedive INstructor Freedive Safety Freedive Training Freedive competition Freedive computer Freedive modes Freedive rescue procedures Freediver Staff Instructor Freediver Freedive Freediving Instructors Freediving performance Freediving Fun Divers Zanzibar Fur rade Galapagos Gar Waterman Gardens of The Queen Gas Density Gas Planning Gas consumption Gas emboli Gas laws Gas management Gas mixes GasPerformance Gasblends Gases Gass bubbles Gastoeusophagus Gastric bypass Gastroenterologist Gas Gear Servicing Georgina Jones Germs Geyer Bank Giant Kelp Forest Giant Kelp Giant stride Girls that Scba Gobies Golden fish Gordon Hiles Great White Sharks Green sea turtle Green turles Greenlings Guidebook Guinness World Record Gutt irritations HBOT HBO HCV HELP HIRA HMLI HMS Britanica Haemorhoid treatment Hand signals Harry Chammas Havanna Hawaii Hawksbill Hazard Description Hazardous Marine life Hazardous marinelife Head injuries Headaches Health practitioner Healthy Food Heart Attack Heart Health Heart Rate monitor Heart fitness Heart rates Heart rate Heart Heat loss Heat stress Helen Walne Heliox Helium Gas Helium Hematoma Hemodynamic Hepatitis C Hepatitus B Hiatal Hernia High Pressure vessels High pressure hoses High temperatures Hilmar Luckhoff Hip strength Hip surgery Hippocampus History Hole in the heart Hood Hot Human diver Humans Hydrate Hydration Hydrogen Hydroids Hydrostatic pressure Hygiene Hyperbaric Chamber Hyperbaric Oxygen Treatments Hyperbaric Oxygen Hyperbaric research Hyperbaric treatment Hyperbarics Hypertension Hypothermia Hypoxia I-52 found INclusivity IdentiFin Imaging Immersion Immine systems In Water Recompression Increased pressure Indemnity form Indian Ocean Indigo SCuba Indonesia Inert gas Infections Infra red Imaging Inhaca Ocean Alliance Injections Inner ear Instinct Instruction Instructors Insulation Insurance policy Insurance Integrated Physiology International travel International Internship programs Internship Interval training Investigations Irritation Irukandji Syndrome Islamorada Isotta housing Italy Itchy Rash Its OK Jellyfish Jennifer Hayes Jill Heinerth Joanna Wyrebek John Vowles Joint pain Joshua Journal for Technical Diving Junior Open Water Diver KZN South Coast KZN Karen van den Oever Kate Jonker KateJonker Kelp Forest Kelp forests KelpForests Ken Finlay Kenya Kidneys Kids scubadiver Komati Springs KwaZulu Natal Kwazulu-Natal LED lights LED Labour laws Lake Huron Lara Lambiase Laryngospasm Lauren Arthur Leanne Walmsley Learning to dive Leatherbacks Leatherback Legal Network Legal advice Legislation Lembeh Straights Lenses Leslie Lwaney Leukemis Liability Insurance Liability Risks Liability releases Liability Life expectancy Lifestyle Lighting equipment Lighting Lightroom editing Lights Lionfish Live aboard diving Liveaboard Liver Toxicity Liver diseas Liz Louw Llandudno Loss of consciousness Lost at sea Lost divers Low Visability Low blood platelets Low blood pressure Low pressure deterioration Low volume masks Lumpsuckers Lung Irritation Lung flexibility Lung function Lung injuries Lung over expansion Lung squeeze Lung surgery Lung MOD MOzambique diving MPA Macro photography Mafia Island Maintenance Malaria Mammalian Dive Response Mammalian effect Manatees Mandarin Fish Marfan syndrome Marine Biologist Marine Biology Marine Mega fauna Marine Science Marine Scientists Marine conservation Marine parks Marine plants Marinelife Marinescience Mark Barker Markus Dirschi Marlin Marne protecte areas Mask clearing Masks Mask Master scuba diver Matty Smith Maximum operating depth Medical FAQ Medical Q Medical emergencies Medical forms Medical oxygen Medical questionaire Medical statement Medical team Medicalquestionaires Medicalresearch Medicalstudents Medication Mehgan Heaney-Grier Membership benefits Menopause Menstruation Mental health Mermaid Danii Mesophotic Metotrexate Mexico Michael Aw Micro Photography Microbubbles Middle ear pressure Mike Bartick Military front press Military Misool Resort Raja Ampat Mixed Gas Mnemba Ataol Mono Fins Mooring lines More pressure Motion sickness Motionsickness Mount Kilimanjaro Mozambique Muck Diving Muscle pain Mycobacterium marinum NDL limits NSRI Narcosis National Geographic Nature Nausea Nauticam Ambassadors Nauticam Ambassador Nautilus Navigation Ndibranchs Neck pain Neoprene layers Neuro assessments Neurocognitive research Neurological assessments Neuromotor exercises New Caledonia Nichola Bird Nicorette Nicotine Nitrogen Narcosis Nitrogen build up Nitrox No Decompression Limits No-decompression limits No-decompression Non-nano zinc oxide Non-rebreather Mask Non-smoking Nondiving related illness Nonrebreather masks Normal Air North Sulawesi Northern Taiwan Nosebleeds Nudibranchs Nuno Gomes Nutrition O2 enriched O2 oxygen provider. O2 providers O2 servicing O2 treatments O2treatments OOxygen maintenance Ocean Alliance Ocean Projects Ocean Research Ocean animals Ocean clean up Ocean community Ocean conservation Ocean life Ocean mammals Ocean migrations Ocean pollution Oceangate Ocean Octopus Oil contamination Olive Ridley Open Ocean Open water divers Operatorethics Optical focus Oral contraseptives Orbital implants Oronasal mask Osteonecrosis Otters Out and about Out of air Outer ears Outreach Overhead Envirenments Oxygen Administration Oxygen Cylinder Oxygen Toxicity Oxygen Units Oxygen deficit Oxygen deicit Oxygen dificiency Oxygen ears Oxygen equipment Oxygen explosions Oxygen kit Oxygen masks Oxygen providers Oxygen safety Oxygen supplies Oxygen supply Oxygen systems Oxygen therapy Oxygen treatment Oxygen P J Prinsloo PADI Freedivers PFI PFOs PFO PJP Tech PTSD Paper Nautilus Paralysis Parentalsupervision Part 3 Partner Training Patent foramen ovale PatentForamen Ovale Pemba Island Peri-peri Divers Personal Perspective Petar Denoble Peter Lindholm Philippine Islands Philippines Phillipines Photographers Photographer Photography tips Photography Physical Fitness Physioball Physiology Physiotherapy Pills Pilot Whale Pistons Planning Plastic pollution Plastic Plimsoll Interface Pneumonia Pneumothorax Poison Pole fishing Polka Dot Bat fish Pollution Pool Diving Pool chemicals Pool maintenance Pool workout Pools Post traumatic Post-dive Potuguese man-of-war Pre-dive fitness Pre-dive Predive check Pregnancy Pregnant divers Preparation Prepared diver Press Release Preventions ProDive Port Elizabeth Product scuba nudi Professional rights Protection Provider course Psycological Pulmanologist Pulmonary Barotrauma Pulmonary Bleb Pulmonary Edema Pulmonary Hypertension Pulse Punture wounds Pure Air Pure Apnea Purge Quit Smoking Q RAID South Africa RCAP REEF RMV ROS Radio communications Range of motion Rashes Reactive oxygen species Rebreather diving Rebreatherdive Recces Rechargeable batteries. Rechargeable Recompression chamber Recompression treatment Recompression Recreational dives Recycle Red SEA Reef Chcek Reef Conservation Reef Environmental Education Foundation Reef protection Reef safe Reef surveyors Refractive correction Regal Sea Goddesses Regulator failure Regulators Regulator Remote areas Remote dive locations Remote islands Renewable Rental gear Report incidents Rescue Divers Rescue Procedure Rescue breathing Rescue breaths Rescue diver Rescue skills Rescue skill Rescue training Rescue Researcher profile Research Respitory Minute Volume Resume diving Return To Diving Return to diving Reuseable items Review Rhinopias Risk Assessments Risk assesments Risk assessment Risk elements Risk management Risk mitigation Risks of Seizures River diving Riviera Maya Roatan Marine Park Roatan Ronblom Rubber ducks SABS 019 SAC SMB SRC SafariLive Safe diving practices Safety Concerns Safety Divers Safety Gear Safety Stop Safety in Air Safety SaherSafe Barrier Salisbury Island Salish Seas Salty Wanderer Sanitising Sanne Volja Sara Andreotti Sara Banderby Sara Campbell Sardine Run Sargassum sea Saturation Diving Saturation diver Save our seas Schrimps Science of diving Science Scoliosis Scombroid Poisoning Scorpion Fish Scuba Air Quality Scuba Guru Scuba Injury Scuba Instructor Scuba children Scuba divers Scuba dive Scuba diving Scuba education Scuba gear Scuba health Scubalearners Scubalife Sea Horses Sea Turtles Sea rescue Sea slugs Seagrass Sealcolonies Sealife Seals Seasickness Seaweeds Seaweed Sea Self Rescue Send Nudi Shallow Water Blackout Shallow dives Shark Protection Shark Research Shark conservation Shark diving Shark specialist Sharks Shipwrecks Shit Happens Shore entries Shoulder strength Sidemount Sideplank Signalling devices Signs and Symptoms Silty bottoms Sit-ups Sixgill Sharks Skills in action Skin Bends Skin outbreak Skin rash Smart phone photography Snells Window Snorkeling Snorkels Social Distancing Sodwana Bay Solomon Islands Sonnier bank South Africa Southern Sea Otters SpareAir Special Operations Special forces units Sperm Whales Spinal Bend Spinal bends Spinal cord DCS Spinal dura Spinal pain Spinner dolphins Spleen Splits Sports medicine Squeezes Squid Run Stability exercise Stage cylinder Standars Static breath hold Statin Mediction Stay Fit Stay Warm Steel Stefan Randig Stents Step ups Stephen Frink Stepping up Stobes Stockton Rush Stonetown Stretch band exercise Stretch bands Stretching Strobe Lighting Strobes Stroke Submerge tech Submerged Sudafed Sulawesi Sun protection Sun screen Sunscreen Supplemental oxygen Surface Air Consumption Surface Consumption Rate Surface Marker Buoys Surface supplied Air Surfaced Surfers Surgeries Surgery Survivor Suspension training Swim Fitness Swimmers health SwimmingIn wateractivities Swimming Sylvia Earl Symbiosis Symbiosys TRavel safety Tabata protocol Talya Davidoff Tank valve Tanzania Tara Panton Tattoes Tchnical diving Team Awareness Tec Clark Tec divers Tec diving Tech diving Technical Diving Technical diver Technical divng Temperature Homeostatis The Bends The Cavettes The Produce The Titanic Wreck The Wild Coast The greatest Shoal The silent world The truth Thermal Notions Thermoregulation Thomas Peschak Thresher shark Thunder Bay National Marine Sanctuary Tides Tips and trick Tonga Tooth squeeze Transplants Trashbag Trauma Travel Safe Travel destinations Travel smarter Travel tips Travel Tropical Coastal Management Tulamben Tullum Tulum. Tumbatu Island Tuna Tunnelling Turks and Caicos Turtles Tweezers Ultrsound Umkomaas Unconscious ascent Unconscious diver Unconsciousness Underground waterways Underground work Underseaa world Underwaater Photos Underwater Photography Underwater Photograper Underwater Photograpgraphy Underwater Photographer Manirelife Underwater Photographers Underwater Research Underwater camera Underwater critters Underwater floral Gardens Underwater hockey Underwater imaging Underwater lights Underwater models Underwater photographer Underwater photography Underwater photos Underwater pho Underwater sound Underwatercommunications Underwater Underwtaer photography University of Stellenbosch Unresponsive Urchins Urinary retention. VGE Vacations Vaccines Vagus nerve Valsalva manoeuvers Valve stem seals Vape Vaping Vasopressors Vasvagal Syncope Venous gas emboli Ventilate Venting Verna van Schak Veterinarian Videography Vincenzo Ferri. Virus infections Volatile fuels WWII wrecks War stories Wash gear Washout treatments Wastewater Watchman device Water Resistance Water Weakness Weck Weigang Xu Weightloss Weights West Papua Western Cape Diving Wet Lenses Wet diving bell Wetsuit fitting Wetsuites Wetsuits Wetsuit White balance Whitetpped Sharks Wide Angle Photos Wide angles Wildlife park Wildlife Winter Wits Underwater Club Wolf Eels Woman and diving Woman in diving Woman's Health Womans health Woman Women In Diving SA Women and Diving Women in Freediving Women in diving Womens Month Womens health Work of Breathing Workout World Deeepst Dive Record World Records Wound dressings Wreck History Wreck divers Wreck dive Wreck diving Wreck exploration Wreckdiving Wrecks Wrist technology Yachts Yoga Youth diver Zandile Ndholvu Zanzibar Zoology Zooplankton \ Blennies abrasion absolute pressure acoustic neuroma excision adverse seas air-cushioned alert diver altitude alveolar walls anemia antibiotics anticoagulants antiseptics ascent bandages barodontalgia bent-over barbell rows bioassays biodiversity bloodcells blue carbon body art breathing air calories burn canal blockage cannabis oil carbon dioxide toxicity cardiovascular career developments cerebrospinal fluid cervical spine checklist chemo port children child chronic obstructive pulmonary disease clearances closed circuit scuba compressed gass coral growth corrective lenses crystalweed currents cuts cylinder filling daggaolie dagga dead lift decompression algorithms decongestants decongestion deep dive training dehydration discovery dive clubs dive injuries dive medicing dive ready child dive reflex dive tribe divecomputers diver in distress diver rescue diver training dive diving attraction diving hoods doctors dolphns domestic travel dri-suits drowning dry mucous membranes dry suits dry e-cigarettes ear spaces earplugs ears elearning electrocardiogram electrolyte imbalance electroytes emergency action plans emergency assessment emergency training environmentally friendly equalising equalizing exposure injuries eyes fEMAL DIVERS fire rescue fish watching fitness Balance fitnes flexible tubing frediving freedivers gas bubble gas poisoning gastric acid gene expression health heartburn heron bridge histidine hospital humidity hypobaric hypoxia immersion and bubble formation immersion pulmonary edema (IPE informal education isopropyl alcohol jaundice join DAN knee lanyard laparoscopic surgery life jackets longevity lower stress lox oxygen level lungs malaise mamalian effect marielife marine pathogens medical Questions medical issues medical procedures medical risk assesment medications mental challenge mental preparedness micro-organisims micro minor illness mucous membranes multilineage dysplasia myelodysplasia nasal steroids nasal near drowning nematocysts neurological newdivers nitrogen bubbles no tanx off-gassed operating theatre operations orthopeadic otitis media out planting outgas pain parameters perforation phillippines phrenic nerve physical challenges pinched nerves plasters pneumoperitoneum polyester-TPU polyether-TPU post dive posture prescription mask preserve prevention professional emergency responders proper equalization psychoactive pulmonary barotrauma. pulmonary injury. pulmunary barotrauma pure oxygen radiation rebreather mask rebreathers retinal detachment risk areas safety stops saturation scissors scuba equipment scuba sea goddesses single use sinus infections situationalawarenes smoking snorkeling. spearfishing spliff sterilising stings strength sub-aquatic sunscreen lotion swimmer's ear swimmer\'s ear swimmers ears tattoo care tecnical diver thermal protection tissue damage toxicity trachea training travel Insurance trimix tympanic membrane unified standards upcycled upwelling virtual coach vision impaired vomiting warmers water quality zinc oxide