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90-411: The popularisation of the term technical diving has been credited to Michael Menduno , who was editor of the (now defunct) diving magazine aquaCorps Journal , but the concept and term, technical diving , go back at least as far as 1977, and divers have been engaging in what is now commonly referred to as technical diving for decades. The popular use of the term technical diving can be traced back to

180-545: A 130-foot limit in its protocols and has never experienced any accidents or injuries during air dives between 130 feet and the deepest air dives that the scientific diving community permits, 190 feet, where the U.S. Navy Standard Air Tables shifts to the Exceptional Exposure Tables. In Europe, some countries set the recreational diving limit at 50 metres (160 ft), and that corresponds with the limit also imposed in some professional fields, such as police divers in

270-558: A Scientist Astronaut . Hamilton left the Air Force with and moved to Buffalo, New York , in 1964, where he met Heinz Schreiner and began his work on the undersea world as a scientist and director of the Ocean Systems environmental physiology and diving research lab in Tarrytown, New York . Hamilton investigated the effects of gases in hyperbaric and hypobaric environments which led to

360-669: A breathing gas, but other breathing gas mixtures are commonly used to manage specific problems. Some additional knowledge is required to understand the effects of these gases on the body during a dive and additional skills are needed to safely manage their use. One of the more divisive subjects in technical diving concerns using compressed air as a breathing gas on dives below 130 feet (40 m). Some training agencies still promote and teach courses using air up to depths of 60m. These include TDI, IANTD and DSAT/PADI. Others, including NAUI Tec, GUE, ISE and UTD consider that diving deeper than 100–130 feet (30–40 m), depending upon agency, on air

450-532: A different purpose, in that the objects to be removed are not intended to be recovered, just removed or reduced to a condition where they no longer constitute a hazard or obstruction. Many of the techniques and procedures used in clearance diving are also used in salvage work. The underside of the hull is an overhead environment with no direct vertical access to the surface. As such it constitutes an entrapment hazard, particularly under large vessels where it may be too dark due to low natural light or turbid water to see

540-422: A diver can train to overcome any measure of narcosis at a given depth or become tolerant of it. The Divers Alert Network does not endorse or reject deep air diving but does note the additional risks involved. Nitrox is a popular diving gas mix, that reduces the maximum allowable depth as compared to air. Nitrox also allows greater bottom time and shorter surface intervals by reducing the buildup of nitrogen in

630-512: A limited flow air supply, a sudden rapid descent could lead to severe helmet squeeze, but this is prevented by demand-supplied gas, and neck dams on later helmets, which allow water to flood the helmet until the gas supply catches up with the compression. Surface supply ensures that the gas supply will not run out suddenly due to high demand, which can deplete scuba supply to the extent that there may not be enough left to surface according to plan. Any sudden increase in depth can also cause barotrauma of

720-429: A low risk of out of air incidents, but it can be cumbersome, only allows a limited penetration distance based on available umbilical length and the ability of the diver to drag it along and the ability of the tenders to drag it back during exit, and can become snagged on obstructions or diverted through line traps. It may need one or more in-water tenders or guide hoops to avoid these problems, and it may not be possible for

810-554: A major restriction requires the diver to remove some equipment to fit through. A swim-through is an arch, lintel, or short, clear tunnel that has sufficient space to allow a diver to swim through and where the light of the opening at the far end is visible through the hole. It is technically an overhead environment, but one often entered by divers with only open water certification, if the risk of entrapment appears to be very low. Diving under moored ships , usually for inspection, maintenance and repair, or incidentally, when diving from one

900-431: A physical ceiling. This form of diving implies a much larger reliance on the redundancy of critical equipment and procedural training since the diver must stay underwater until it is safe to ascend or the diver has successfully exited the overhead environment. A diver at the end of a long or deep dive may need to do decompression stops to avoid decompression sickness , also known as "the bends". Metabolically inert gases in

990-399: A problem at depths of 100 feet (30 m) or greater, but this differs between divers. Increased depth also increases the partial pressure of oxygen and so increases the risk of oxygen toxicity. Technical diving often includes the use of breathing mixtures other than air to reduce these risks, and the additional complexity of managing a variety of breathing mixtures introduces other risks and

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1080-418: A real possibility of not being able to see the way out, along with sufficient emergency gas to compensate for any single catastrophic breathing gas supply failure at any time during the planned course of a penetration dive. Surface supplied diving reduces the risk of getting lost under an overhead, as the umbilical provides a reliable guideline back to the entry point, and a reliable source of breathing gas with

1170-441: A reduced ability to react or think clearly. By adding helium to the breathing mix, these effects can be reduced, as helium does not have the same narcotic properties at depth. Helitrox/triox proponents argue that the defining risk for air and nitrox diving depth should be nitrogen narcosis , and suggest that when the partial pressure of nitrogen reaches approximately 4.0 ATA, which occurs at about 130 feet (40 m) for air, helium

1260-423: A reel jam when deploying an inflatable decompression buoy, and the reel is clipped on, the diver may not be able to manage several simultaneously accelerating buoyancy malfunctions. Dual bladder buoyancy compensators can contain air inadvertently added to the backup bladder, which the diver does not release as it is not supposed to be there in the first place. All of these failures can be either avoided altogether or

1350-415: A secondary risk while mitigating a primary risk, such as the complexity of gas management needed to reduce the risk of a fatal gas supply failure, or the use of gases potentially unbreathable for some parts of a dive profile to reduce the risk of harm caused by oxygen toxicity, nitrogen narcosis or decompression sickness for the whole operation. Reduction of secondary risks may also affect equipment choice, but

1440-410: A technical diving challenge. Underwater caves have a wide range of physical features, and can contain fauna not found elsewhere. Several organisations dedicated to cave diving safety and exploration exist, and several agencies provide specialised training in the skills and procedures considered necessary for acceptable safety. Cavern diving is an arbitrarily defined, limited scope activity of diving in

1530-402: A topographical feature which is open to at least one side, but obstructed overhead, and deep enough for a diver to be under the overhang, or as severe as a major restriction deep inside a cave or wreck. A restriction is a space through which it is possible for a diver to pass with some difficulty due to a lack of space. A minor restriction is too small for two divers to swim through together,

1620-469: A variety of gases depending on when and where they will be used, and as some may not support life if used at the wrong depth, they are marked for positive identification of the contents. Managing the larger number of cylinders is an additional task loading on the diver. Cylinders are usually labeled with the gas mixture and will also be marked with the maximum operating depth and if applicable, minimum operating depth . Technical diving can be done using air as

1710-462: A way of exploring flooded caves for scientific investigation, or for the search for and recovery of divers or, as in the 2018 Thai cave rescue , other cave users. The equipment used varies depending on the circumstances, and ranges from breath hold to surface supplied , but almost all cave-diving is done using scuba equipment , often in specialised configurations with redundancies such as sidemount or backmounted twinset. Recreational cave-diving

1800-408: Is a class of confinement which restricts the diver from free vertical access to the surface. An overhead environment may also be a confined space , in which the diver is restricted in their ability to maneuver, and is roughly the opposite of open water . Confinement can influence diver safety and the ability of the diver to perform the required task. Some types of confinement improve safety by limiting

1890-414: Is a need for redundancy of breathing equipment. Technical divers usually carry at least two independent breathing gas sources, each with its own gas delivery system. In the event of a failure of one set, the second set is available as a back-up system. The backup system should allow the diver to safely return to the surface from any point of the planned dive, but may involve the intervention of other divers in

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1980-417: Is also a hazard of crushing if the clearance is small and the tide range is large. The main generic hazards of penetration diving are being unable to navigate back to the surface and running out of breathing gas before reaching the surface. Both of these hazards are well mitigated by the use of surface supplied breathing equipment, but at the cost of seriously reduced mobility and extremely restricted range, to

2070-431: Is also considered penetration diving if the ship is large. In some cases the gap between the ship and the bottom or the jetty or dock can be quite small and the visibility may be poor. Fatal accidents have occurred when a diver has run out of air trying to find the way out from under a large flat-bottomed vessel in low visibility. Cave-diving is underwater diving in water-filled caves . It may be done as an extreme sport,

2160-406: Is also referred to as a "soft", or "physiological" ceiling. These types of physical overhead, or "hard" or "environmental" ceiling can prevent the diver from surfacing directly: In all three of these situations, a guide line or lifeline from the exit to the diver is the standard method of reducing the risk of being unable to find the way out. A lifeline fixed to the diver is more reliable as it

2250-441: Is critical during decompression, where the inability to stay at the correct depth due to excessive buoyancy is associated with a high risk of decompression sickness and a raised risk of barotrauma of ascent. There are several ways that excessive buoyancy can be caused, some of which can be managed by the diver if prompt and correct action is taken, and others that cannot be corrected. This problem may be caused by poor planning, in that

2340-437: Is generally considered to be a type of technical diving due to the lack of a free surface during large parts of the dive, and often involves planned decompression stops. A distinction is made by recreational diver training agencies between cave-diving and cavern-diving, where cavern diving is deemed to be diving in those parts of a cave where the exit to open water can be seen by natural light. An arbitrary distance limit to

2430-447: Is generally not considered salvage work, though some recovery of artifacts may be done by recreational divers. Most salvage diving is commercial work, or military work, depending on the diving contractor and the purpose for the salvage operation, Similar underwater work may be done by divers as part of forensic investigations into accidents, in which case the procedures may be more closely allied with underwater archaeology than

2520-597: Is generally redundancy designed into the system. This redundancy is intended to allow a safe termination of the dive if it occurs underwater, by eliminating a critical failure point. Diving with a unit that already has a malfunction, means that there is a single critical point of failure in that unit, which could cause a life-threatening emergency if another item in the critical path were to fail. The risk may increase by orders of magnitude. Several factors have been identified as predispositions to accidents in technical diving. The techniques and equipment are complex, which increases

2610-438: Is issued by several recreational diver training agencies, under a variety of names, often with considerable overlap or in some cases split into depth ranges. The certification titles vary between agencies but can be categorized as: Robert William Hamilton Jr. Robert William Hamilton Jr. (1930 – 16 September 2011), known as Bill , was an American physiologist known for his work in hyperbaric physiology . He

2700-480: Is largely skill-based. Training of technical divers includes procedures that are known from experience to be effective in handling the most common contingencies. Divers proficient in these emergency drills are less likely to be overwhelmed by the circumstances when things do not go according to plan, and are less likely to panic. Technical dives may be defined as being dives deeper than about 130 feet (40 m) or dives in an overhead environment with no direct access to

2790-417: Is managed by equipment configuration and procedural training. To reduce nitrogen narcosis , it is common to use trimix which uses helium to replace some of the nitrogen in the diver's breathing mixture, or heliox , in which there is no nitrogen. Technical dives may alternatively be defined as dives where the diver cannot safely ascend directly to the surface either due to a mandatory decompression stop or

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2880-402: Is necessary to limit the effects of the narcosis. Technical dives may also be characterised by the use of hypoxic breathing gas mixtures, including hypoxic trimix , heliox , and heliair . A diver breathing normal air (with 21% oxygen) will be exposed to increased risk of central nervous system oxygen toxicity at depths greater than about 180 feet (55 m) The first sign of oxygen toxicity

2970-405: Is not easy to lose, and is often used when diving under ice, where the line is unlikely to snag and the distance is reasonably short, and can be tended by a person at the surface. Static guidelines are more suitable when a lifeline is likely to snag on the environment or on other divers in the group, and may be left in situ to be used for other dives, or recovered on the way out by winding back onto

3060-437: Is some professional disagreement as to what exactly technical diving encompasses. Nitrox diving and rebreather diving were originally considered technical, but this is no longer universally the case as several certification agencies now offer Recreational Nitrox and recreational rebreather training and certification. Some training agencies classify penetration diving in wrecks and caves as technical diving. Even those who agree on

3150-430: Is that many divers become complacent as they become more familiar with the equipment, and begin to neglect predive checklists while assembling and preparing the equipment for use - procedures that are officially part of all rebreather training programs. There can also be a tendency to neglect post-dive maintenance, and some divers will dive knowing that there are functional problems with the unit, because they know that there

3240-424: Is the associated hazards, of which there are more associated with technical diving, and risk, which is often, but not always greater in technical diving. Hazards are the circumstances that may cause harm, and risk is the likelihood of the harm actually occurring. The hazards are partly due to the extended scope of technical diving, and partly associated with the equipment used. In some cases, the equipment used presents

3330-437: Is unacceptably risky. They promote the use of mixtures containing helium to limit the apparent narcotic depth to their agency specified limit should be used for dives beyond a certain limit. Even though TDI and IANTD teach courses using air up to depths of 60m, they also offer courses include "helitrox" "recreational trimix" and "advance recreational trimix" that also use mixtures containing helium to mitigate narcotic concerns when

3420-478: Is used mainly by recreational and technical divers. Professional divers, when diving on a shipwreck, generally refer to the specific task, such as salvage work, accident investigation or archaeological survey. Although most wreck dive sites are at shipwrecks, there is an increasing trend to scuttle retired ships to create artificial reef sites . Diving to crashed aircraft can also be considered wreck diving. The recreation of wreck diving makes no distinction as to how

3510-413: Is usually a convulsion without warning which usually results in death when the demand valve mouthpiece falls out and the victim drowns. Sometimes the diver may get warning symptoms before the convulsion. These can include visual and auditory hallucinations, nausea, twitching (especially in the face and hands), irritability and mood swings, and dizziness. These gas mixes can also lower the level of oxygen in

3600-642: The California Advisory Committee on Scientific and Technical Diving (CACSTD), to distinguish more complex modes of recreational diving from scientific diving for regulatory purposes. In the US the Occupational Safety and Health Administration categorises diving which is not occupational as recreational diving for purposes of exemption from regulation. This is also the case in some other countries, including South Africa. Technical diving emerged between

3690-537: The Sub-Aqua Association and other European agencies make staged decompression dives available, and the SAA teaches modest staged decompression as part of its advanced training programme. The following table gives an overview of the activities that various agencies suggest to differentiate between technical and recreational diving: One of the perceived differences between technical and other forms of recreational diving

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3780-588: The University of Minnesota . Hamilton served as a fighter pilot in the U.S. Air Force in the Korean War and Vietnam , earning the rank of major . He was also awarded the Distinguished Flying Cross , Air Medal , and other decorations. He helped solve equipment problems on unsuccessful bailouts as a Life Support Officer, which earned him a National Academy of Sciences recommendation to NASA as

3870-421: The 60–125 m depth range, and doing decompression on oxygen. The details of many of these dives were not disclosed by the divers as these dives were considered experimental and dangerous. The divers who conducted these dives did not consider them suitable for the ordinary person, but necessary to extend the frontiers of exploration, and there were no consensus guidelines for scuba diving beyond 40 m. There

3960-482: The NOAA Diving Manual. R.W. Hamilton contributed to, and authored, a large number of scientific and technical papers, reports, and diving medical and safety workshop Proceedings. Some of these are listed here: Penetration diving An overhead or penetration diving environment is where the diver enters a space from which there is no direct, purely vertical ascent to the safety of breathable atmosphere at

4050-694: The UK. The major French agencies all teach diving on air to 60 metres (200 ft) as part of their standard recreational certifications. Deep air proponents base the depth limit of air diving upon the risk of oxygen toxicity . Accordingly, they view the limit as being the depth at which partial pressure of oxygen reaches 1.4 ATA, which occurs at about 186 feet (57 m). Both sides of the community tend to present self-supporting data. Divers trained and experienced in deep air diving report fewer problems with narcosis than those trained and experienced in mixed gas diving trimix/heliox, though scientific evidence does not show that

4140-493: The USA happened to technical divers. It is not known how many technical dives this was spread over, but it was considered likely that technical divers are at greater risk. The techniques and associated equipment that have been developed to overcome the limitations of conventional single-cylinder, open-circuit scuba diving are necessarily more complex and subject to error, and technical dives are often done in more dangerous environments, so

4230-485: The ability of the diver to move into higher risk areas, others limit the ability of the diver to maneuver, to perform the task of the dive, or to escape to a place of safety in an emergency. The usual types of recreational penetration diving are cave diving , cavern diving , ice diving and wreck penetration diving . Professional divers may also penetrate culverts , intakes such as penstocks , sewers , and under floating ships. An overhead may be as minor as an overhang ,

4320-400: The amateur diving community had a more trial-and-error approach to the use of mixed gas and rebreathers. Consequently, a relatively large number of fatal incidents occurred during the early years, before a reasonably reliable set of operating procedures and standards began to emerge, making the movement somewhat controversial, both within the mainstream diving establishment and between sectors of

4410-436: The broad definitions of technical diving may disagree on the precise boundaries between technical and recreational diving. The European diving agencies tend to draw the line between recreational and technical diving at 50 metres (160 ft) and many, as noted for BSAC above, teach staged decompression diving as an integral part of recreational training, rather than as a fundamental change of scope. The Bühlmann tables used by

4500-558: The consequences of an error or malfunction are greater. Although the skill levels and training of technical divers are generally significantly higher than those of recreational divers, there are indications that technical divers, in general, are at higher risk, and that closed circuit rebreather diving may be particularly dangerous. Relatively complex technical diving operations may be planned and run like an expedition, or professional diving operation, with surface and in-water support personnel providing direct assistance or on stand-by to assist

4590-448: The cover story of the first issue of aquaCorps magazine (1990–1996), in early 1990, titled Call it "High-Tech" Diving by Bill Hamilton , describing the current state of recreational diving beyond the generally accepted limits, such as deep, decompression and mixed gas diving. By mid-1991, the magazine was using the term technical diving , as an analogy to the established term technical (rock) climbing . More recently, recognizing that

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4680-460: The dawn of time. We can’t see what’s there. We can see what’s on the dark side of the moon or what’s on Mars, but you can’t see what’s in the back of a cave unless you go there. Sheck Exley, Exley on Mix , aquaCorps #4, Jan 1992 The urge to go where no one has gone before has always been a driving force for explorers, and the 1980s was a time of intense exploration by the cave-diving community, some of whom were doing relatively long air dives in

4770-458: The development of decompression modelling tools and operational procedures for divers, astronauts, hyperbaric chambers, and tunnel and caisson workers. He was both the physiologist and test subject on the first manned laboratory saturation diving to the continental shelf pressure of 12 ATA (200 msw) in 1965. He founded Hamilton Research, Ltd. (1976), for decompression and hyperbaric research, which developed procedures and techniques to mitigate

4860-427: The dive takes place under ice . Because diving under ice places the diver in an overhead environment typically with only a single entry/exit point, it requires special procedures and equipment. Ice diving is done for purposes of recreation, scientific research, public safety (usually search and rescue/recovery) and other professional or commercial reasons. The most obvious hazards of ice diving are getting lost under

4950-406: The diver may underestimate the weight loss of using up the breathing gas in all the cylinders, by losing ballast weights during the dive, or by inflation problems with buoyancy compensator or drysuit, or both. Insufficient ballast weight to allow neutral buoyancy at the shallowest decompression stop with nearly empty cylinders is an example of a buoyancy problem that can generally not be corrected by

5040-438: The diver or diving team must be able to troubleshoot and solve the problem underwater. This requires planning, situational awareness, and redundancy in critical equipment, and is facilitated by skill and experience in appropriate procedures for managing reasonably foreseeable contingencies. Some rebreather diving safety issues can be addressed by training, others may require a change in technical diver culture. A major safety issue

5130-405: The diver's breathing gas, such as nitrogen and helium , are absorbed into body tissues when breathed under high pressure, mainly during the deep phase of the dive. These dissolved gases must be released slowly from the body tissues by controlling the ascent rate to restrict the formation and growth of bubbles. This is usually done by pausing or "doing stops" at various depths during the ascent to

5220-465: The diver's tissues. This is accomplished by increasing the percentage of oxygen in the breathing gas. The depth limit of a nitrox mixture is governed by the partial pressure of oxygen, which is generally limited to 1.4 to 1.6 bar depending on the activity of the diver and duration of exposure. Nitrox mixtures up to 100% oxygen are also used for accelerated decompression . Increased pressure due to depth causes nitrogen to become narcotic , resulting in

5310-428: The diver. If an empty cylinder is positively buoyant, the diver may jettison it and allow it to float away, but if the empty cylinders are negatively buoyant, jettisoning them will exacerbate the problem, making the diver even more buoyant. Drysuit and buoyancy compensator inflation can cause runaway ascent, which can usually be managed if corrected immediately. If the initial problem is caused by loss of ballast weights or

5400-473: The diving depth is limited to 30-45m. Such courses used to be referred to as "deep air" courses, but are now commonly called "extended range" courses. The 130 ft limit entered the recreation and technical communities in the USA from the military diving community where it was the depth at which the US Navy recommended shifting from scuba to surface-supplied air. The scientific diving community has never specified

5490-407: The ears and sinuses if the diver cannot equalize fast enough. There is very little reliable data describing the demographics, activities and accidents of the technical diving population. Conclusions about accident rates must be considered tentative. The 2003 DAN report on decompression illness and dive fatalities indicates that 9.8% of all cases of decompression illness and 20% of diving fatalities in

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5580-591: The effects of High Pressure Neurological Syndrome , and the Diving Computational Analysis Program (DCAP), which he co-developed with David J. Kenyon. Hamilton was the principal investigator of the NOAA Repex Oxygen Exposure tables to assist divers in avoiding oxygen toxicity . These became the basis for most oxygen exposure calculation methods used for saturation and repetitive diving exposures to oxygen in breathing mixtures. In

5670-436: The exit. There are some applications where scuba diving is appropriate and surface-supplied diving is not, and other where the converse is true. In other applications either may be appropriate, and the mode is chosen to suit the specific circumstances. In all cases risk is managed by appropriate planning , skills, training and choice of equipment. Penetration diving is also known as diving in overhead environments , which

5760-487: The expedition divers. Surface support might include surface stand-by divers, boat crew, porters, emergency medical personnel, and gas blenders. In-water support may provide supplementary breathing gas, monitor divers during long decompression stops, and provide communications services between the surface team and the expedition divers. In some cases the risk assessment may persuade the dive team to use similar equipment to that used in professional diving, such as ROV monitoring or

5850-406: The extent that some penetration activities are impossible on surface supply. For scuba diving, the risk of getting lost and running out of breathing gas is real and significant. These are the most common factors recorded in diving deaths in penetration diving. The use of a continuous guideline leading to open water is recognised as the most important safety precaution in any overhead environment with

5940-419: The ice, hypothermia, and regulator failure due to freezing. Scuba divers are generally tethered for safety. This means that the diver wears a harness to which a line is secured, and the other end of the line is secured above the surface and monitored by an attendant. Surface supplied equipment inherently provides a tether, and reduces the risks of regulator first stage freezing as the first stage can be managed by

6030-634: The late 1980s, he developed project-specific custom decompression tables . His work with decompression tables, physiological effects of gases, and methods of managing exposure to oxygen, helped to open up the new field of technical diving . This included work with the National Oceanographic and Atmospheric Administration (NOAA) developing "Monitor Mix" breathing gas for dives to the USS Monitor . This breathing gas became NOAA Trimix I, with decompression tables designed by Bill Hamilton published in

6120-825: The market include Split-Face Diving (UTD), InnerSpace Explorers (ISE) and Diving Science and Technology (DSAT), the technical arm of Professional Association of Diving Instructors (PADI). The Scuba Schools International (SSI) Technical Diving Program (TechXR – Technical eXtended Range) was launched in 2005. British Sub-Aqua Club (BSAC) training has always had a technical element to its higher qualifications, however, it has recently begun to introduce more technical level Skill Development Courses into all its training schemes by introducing technical awareness into its lowest level qualification of Ocean Diver, for example, and nitrox training will become mandatory. It has also recently introduced trimix qualifications and continues to develop closed-circuit training. Technical diving certification

6210-641: The mid-1980s and the mid-to-late-1990s, and much of the history of its development was recorded in aquaCorps , started by Michael Menduno to provide a forum for these aspects of diving that most recreational diving magazines of the time refused to cover. At the time, amateur scuba divers were exploring the physiological limits of diving using air. Technical divers looked for ways to extend the limits of air dives, and for ways to extend breathing gas supplies as they went deeper and stayed down longer. The military and commercial diving communities had large budgets, extensive infrastructure, and controlled diving operations, but

6300-479: The mix to reduce the danger of oxygen toxicity. Once the oxygen is reduced below about 18% the mix is known as a hypoxic mix as it does not contain enough oxygen to be used safely at the surface. Technical diving encompasses multiple aspects of diving, that typically share a lack of direct access to the surface, which may be caused by physical constraints, like an overhead environment , or physiological, like decompression obligation . In case of emergency, therefore,

6390-438: The more basic procedures of advantageous cost/benefit expected in commercial and military operations. Savage work that may require penetration of flooded internal spaces or diving under the vessel includes surveys of underwater damage, patching, shoring and other reinforcement, and attachment of lifting gear. Clearance diving, the removal of obstructions and hazards to navigation, is closely related to salvage diving, but has

6480-401: The naturally illuminated part of underwater caves, where the risk of getting lost is small, as the exit can be seen, and the equipment needed is reduced due to the limited distance to surface air. It is defined as a recreational diving activity as opposed to a technical diving activity on the grounds of low risk and basic equipment requirements. Ice diving is a type of penetration diving where

6570-445: The open water surface may also be specified. Equipment , procedures , and the requisite skills have been developed to reduce the risk of becoming lost in a flooded cave, and consequently drowning when the breathing gas supply runs out. The equipment aspect largely involves the provision of an adequate breathing gas supply to cover reasonably foreseeable contingencies, redundant dive lights and other safety critical equipment, and

6660-1091: The reel. Guidelines may be very much longer than lifelines, and may be branched and marked. They are used as standard practice for cave diving and wreck penetration. Technical dives in waters where the diver's vision is severely impeded by low-visibility conditions, caused by turbidity or silt out and low light conditions due to depth or enclosure, require greater competence. The combination of low visibility and strong current can make dives in these conditions extremely hazardous, particularly in an overhead environment, and greater skill and reliable and familiar equipment are needed to manage this risk. Limited visibility diving can cause disorientation, potentially leading to loss of sense of direction, loss of effective buoyancy control, etc. Divers in extremely limited visibility situations depend on their instruments such as dive lights , pressure gauges, compass, depth gauge , bottom timer, dive computer, etc., and guidelines for orientation and information. Training for cave and wreck diving includes techniques for managing extreme low visibility, as finding

6750-443: The risk minimized by configuration choices, procedural methods, and correct response to the initial problem. Failure to control depth due to insufficient buoyancy can also lead to scuba accidents. It is less of a problem with surface-supplied diving as the depth that the diver can sink to is limited by the umbilical length, and a sudden or rapid descent can often be quickly stopped by the tender. In early diving using copper helmets and

6840-621: The risk of errors or omissions - the task loading for a closed circuit rebreather diver during critical phases of a dive is greater than for open circuit scuba equipment, The circumstances of technical diving generally mean that errors or omissions are likely to have more serious consequences than in normal recreational diving, and there is a tendency towards competitiveness and risk-taking among many technical divers which appears to have contributed to some well-publicized accidents. Some errors and failures that have repeatedly been implicated in technical diving accidents include: Failure to control depth

6930-437: The standby diver to reach the diver within an acceptable time in an emergency. Another possible problem is hydrodynamic drag in a current. All critical life-support equipment must be sufficiently redundant to allow escape in any reasonably foreseeable failure scenario. Skills and procedures have been developed for managing the hazards and foreseeable contingencies associated with different circumstances of penetration diving and

7020-535: The surface or natural light. Such environments may include fresh and saltwater caves and the interiors of shipwrecks. In many cases, technical dives also include planned decompression carried out over a number of stages during a controlled ascent to the surface at the end of the dive. The depth-based definition is based on risk caused by the progressive impairment of mental competence with the increasing partial pressure of respired nitrogen. Breathing air under pressure causes nitrogen narcosis that usually starts to become

7110-432: The surface team, and the breathing gas supply is less limited. For the surface support team, the hazards include freezing temperatures and falling through thin ice. Penetration diving in shipwrecks is done as a recreational activity and as a professional activity in salvage and clearance work. Wreck diving is recreational diving where the wreckage of ships , aircraft and other artificial structures are explored. The term

7200-403: The surface. Cave diving , wreck diving , ice diving and diving inside or under other natural or artificial underwater structures or enclosures are examples. The restriction on direct ascent increases the risk of diving under an overhead, and this is usually addressed by adaptations of procedures and use of equipment such as redundant breathing gas sources and guide lines to indicate the route to

7290-400: The surface. Most technical divers breathe oxygen enriched breathing gas mixtures such as nitrox and pure oxygen during long-duration decompression, as this increases the rate of inert gas elimination. Elimination of inert gases continues during the surface intervals (time spent on the surface between dives), which must be considered when planning subsequent dives. A decompression obligation

7380-715: The team. Stage cylinders may be dropped along the guideline for later use during the exit or for another dive. A stage cylinder is an additional cylinder filled with a type of breathing gas. Stage cylinders are sometimes used to extend a technical diver's time underwater or to speed up the decompression process. They can also be used to fill lift bags while underwater. The usual configurations used for increased primary gas supply are manifolded or independent twin back mounted cylinders, multiple side mounted cylinders, or rebreathers . Bailout and decompression gas may be included in these arrangements, or carried separately as side-mounted stage and decompression cylinders. Cylinders may carry

7470-438: The technical diving community. While the motivation to extend the depth and duration range by military and commercial divers was mainly driven by operational needs to get the job done, the motivation to exceed recreational diving depths and endurance ranges was more driven by the urge to explore otherwise inaccessible places, which could not at the time be reached by any other means. There are places that no one has been to since

7560-471: The term was already in use by the Royal Navy for rebreather diving, Hamilton redefined technical diving as diving with more than one breathing gas or with a rebreather. Richard Pyle (1999) defined a technical diver as "anyone who routinely conducts dives with staged stops during an ascent as suggested by a given decompression algorithm". The term technical diving was also used in the US as far back as 1977 by

7650-461: The use of a continuous guideline leading the divers back out of the overhead environment . The skills and procedures include effective management of the equipment, and procedures to recover from foreseeable contingencies and emergencies, both by individual divers, and by the teams that dive together. Despite these risks, water-filled caves attract scuba divers, cavers , and speleologists due to their often unexplored nature, and present divers with

7740-857: The use of a stage or wet bell for the ascent and descent, and having a decompression chamber available at the surface. In an emergency, the support team would provide rescue and if necessary search and recovery assistance. Technical diving requires specialized equipment and training. There are many technical training organizations: see the Technical Diving section in the list of diver certification organizations . Technical Diving International (TDI), Global Underwater Explorers (GUE), Professional Scuba Association International (PSAI), International Association of Nitrox and Technical Divers (IANTD) and National Association of Underwater Instructors (NAUI) were popular as of 2009. Professional Technical and Recreational Diving (ProTec) joined in 1997. Recent entries into

7830-604: The vessel ended up on the bottom. Some wreck diving involves penetration of the wreckage, making a direct ascent to the surface impossible for a part of the dive. Salvage diving is the diving work associated with the recovery of all or part of ships, their cargoes , aircraft, and other vehicles and structures which have sunk or fallen into water. In the case of ships it may also refer to repair work done to make an abandoned or distressed but still floating vessel more suitable for towing or propulsion under its own power. The recreational/technical activity known as wreck diving

7920-413: The way out of an overhead environment before running out of gas is a safety-critical skill. Technical divers may use diving equipment other than the usual single cylinder open circuit scuba equipment used by recreational divers. Typically, technical dives take longer than average recreational scuba dives. Because a decompression obligation prevents a diver in difficulty from surfacing immediately, there

8010-413: The way to the side of the hull. The bottom of the largest ships is mostly flat and featureless, exacerbating the problem, and as the plating is almost always steel, a magnetic compass is not reliable for navigation. Only surface-supplied diving is authorised for this work in most jurisdictions, as this not only secures the diver's breathing gas supply, but also provides a guideline to the exit point. There

8100-448: Was predeceased by his first wife Beverly, son Beto and daughter Kitty. He was survived by his wife Kathryn (née Faulkner) of nearly 40 years, daughters Lucy and Sally, grandsons, Felix, Bobby, Zach, Tyler and Truman. He earned his degree in liberal arts at the University of Texas , followed by a master's degree in animal reproductive biology at Texas A&M . He earned his Doctoral degree in physiology and biophysics in 1964 from

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