Technical diving

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Diver Trevor Jackson returning from a 600 ft (183 m) dive Trevor Jackson returns from SS Kyogle.jpg
Diver Trevor Jackson returning from a 600 ft (183 m) dive
Diver equipped for decompression dive Jeffrey phillips freeman before tech dive.jpg
Diver equipped for decompression dive

Technical diving (also referred to as tec diving or tech diving) is scuba diving that exceeds the agency-specified limits of recreational diving for non-professional purposes. Technical diving may expose the diver to hazards beyond those normally associated with recreational diving, and to a greater risk of serious injury or death. Risk may be reduced via appropriate skills, knowledge, and experience. Risk can also be managed by using suitable equipment and procedures. The skills may be developed through specialized training and experience. The equipment involves breathing gases other than air or standard nitrox mixtures, and multiple gas sources. [1]

Contents

The popularisation of the term technical diving has been credited to Michael Menduno, who was editor of the (now defunct) diving magazine aquaCorps Journal, [2] but the concept and term, technical diving, go back at least as far as 1977, [note 1] and divers have been engaging in what is now commonly referred to as technical diving for decades.

Origin

The popular use of the term technical diving can be traced back to 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. [3] [4] : 43 

More recently, recognizing that 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. [4] 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 the California Advisory Committee on Scientific and Technical Diving (CACSTD), to distinguish more complex modes of recreational diving from scientific diving for regulatory purposes. [4] : 43  In the US the Occupational Safety and Health Administration categorises diving which is not occupational as recreational diving for purposes of exemption from regulation. [5] [4] : 43  This is also the case in some other countries, including South Africa. [6]

Technical diving emerged between 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. [7]

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. [7] The military and commercial diving communities had large budgets, extensive infrastructure, and controlled diving operations, but 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 the technical diving community. [7]

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. [7]

There are places that no one has been to since 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 [7]

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 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. [7]

Definition

Technical diver during a decompression stop TechDiving NOAA.jpg
Technical diver during a decompression stop

There is some professional disagreement as to what exactly technical diving encompasses. [9] [10] [11] 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. [12] [13] [14] [15] [16] [17] Some training agencies classify penetration diving in wrecks and caves as technical diving. [18] Even those who agree on 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 the Sub-Aqua Association and other European agencies make staged decompression dives available, [26] : 2–3  and the SAA teaches modest staged decompression as part of its advanced training programme. [27] : A1-9–10 

Scope

The following table gives an overview of the activities that various agencies suggest to differentiate between technical and recreational diving:

Differences between recreational and technical diving
ActivityRecreationalTechnical
Deep diving Maximum depth of 40 metres (130 ft) or 50 metres (160 ft) [note 2] [28] Beyond 40 metres (130 ft) or 50 metres (160 ft) [29] [26]
Decompression diving [note 3] Some agencies define recreational diving as "No decompression" diving; others consider all dives to be decompression dives.Some agencies define technical diving as "Decompression diving"; others consider all dives to be decompression dives. [26]
Mixed gas diving Air and nitrox Nitrox, trimix, heliox and heliair. [30]
Gas switchingSingle gas usedMay switch between gases to accelerate decompression and/or "travel mixes" to permit descent carrying hypoxic gas mixes
Rebreathers Some agencies regard use of semi-closed rebreathers as recreational diving; [31] PADI TecRec, TDI, GUE, IANTD, SSI XR, IART, ISE, NAUI TEC, PSAI, UTD regard as technical diving. [32] [33]
Wreck diving Penetration limited to "light zone" or 30 metres (100 ft) depth + penetrationDeeper penetration
Cave diving Penetration limited to "light zone" or 30 metres (100 ft) depth + penetration [note 4] Deeper penetration, may involve complex navigation and decompression [34]
Ice diving Some recreational agencies regard ice diving as recreational diving [31] Others regard it as technical diving.[ citation needed ]
An example of wreck diving; A technical diver diving the Nasello wreck in Sardinia at 34m depth. Jeffrey Phillips Freeman dives Sardigna nasello 34m.jpg
An example of wreck diving; A technical diver diving the Nasello wreck in Sardinia at 34m depth.

Hazards and risk

One of the perceived differences between technical and other forms of recreational diving 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 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 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.[ citation needed ]

Depth

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 the surface or natural light. [29] 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 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 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. [35]

Inability to ascend directly

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 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. [36]

Decompression stops

Free floating decompression stop Tech diving decompression stop.jpg
Free floating decompression stop

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 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 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 is also referred to as a "soft", or "physiological" ceiling. [37]

Physical 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 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. [38] 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 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. [39] [40]

Extremely limited visibility

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.[ citation needed ] 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 the way out of an overhead environment before running out of gas is a safety-critical skill. [36]

Equipment

Technical diver with decompression gases in side-mounted stage cylinders Tec diver with sidemount tanks.JPG
Technical diver with decompression gases in side-mounted stage cylinders

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. [29] Because a decompression obligation prevents a diver in difficulty from surfacing immediately, there 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 the team. Stage cylinders may be dropped along the guideline for later use during the exit or for another dive. [41]

Equipment configuration

Technical divers preparing for a mixed-gas decompression dive. Note the backplate and wing setup with sidemounted decompression cylinders. Decompression Dive-Preparation.JPG
Technical divers preparing for a mixed-gas decompression dive. Note the backplate and wing setup with sidemounted decompression cylinders.

The usual configurations used for increased primary gas supply are manifolded or independent twin back mounted cylinders, multiple side mounted cylinders, or rebreathers. [29] Bailout and decompression gas may be included in these arrangements, or carried separately as side-mounted stage and decompression cylinders. Cylinders may carry 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. [42] [43]

Gas mixes

Technical diving can be done using air as a breathing gas, but other breathing gas mixtures are commonly used to manage specific problems. [29] 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. [44]

Deep air/extended range diving

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 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 the diving depth is limited to 30-45m. [45] [46]

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.[ citation needed ] The scientific diving community[ clarification needed ] has never specified 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,[ citation needed ] 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), [47] and that corresponds with the limit also imposed in some professional fields, such as police divers in the UK. The major French agencies all teach diving on air to 60 metres (200 ft) as part of their standard recreational certifications. [48] [49] [50]

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 a diver can train to overcome any measure of narcosis at a given depth or become tolerant of it. [51]

The Divers Alert Network does not endorse or reject deep air diving but does note the additional risks involved. [52]

Mixtures to reduce decompression time

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 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. [29]

Nitrox mixtures up to 100% oxygen are also used for accelerated decompression. [29]

Mixtures to reduce nitrogen narcosis

Increased pressure due to depth causes nitrogen to become narcotic, resulting in a reduced ability to react or think clearly. [29] By adding helium to the breathing mix, these effects can be reduced, as helium does not have the same narcotic properties at depth. [29] 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 is necessary to limit the effects of the narcosis. [29]

Mixtures to reduce oxygen toxicity

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) [29] The first sign of oxygen toxicity 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. [53]

These gas mixes can also lower the level of oxygen in 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. [29]

Safety

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, 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. [54] [55]

Some rebreather diving safety issues can be addressed by training, others may require a change in technical diver culture. A major safety issue 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 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. [5]

Accident modes

Several factors have been identified as predispositions to accidents in technical diving. The techniques and equipment are complex, which increases 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. [29]

Some errors and failures that have repeatedly been implicated in technical diving accidents include:

Failure to control depth 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 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 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 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 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 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 the ears and sinuses if the diver cannot equalize fast enough.

Accident statistics

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 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. [29]

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 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. [29]

Operations

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 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. [19] 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 the use of a stage or wet bell for the ascent and descent, and having a decompression chamber available at the surface. [56] In an emergency, the support team would provide rescue and if necessary search and recovery assistance. [19]

Training

Tech diver training Tech diver at lake Iso-Melkutin Finland 2013.jpg
Tech diver training

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 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. [57]

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.[ citation needed ]

Certification

Technical diving certification 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:

See also

Related Research Articles

Nitrox refers to any gas mixture composed of nitrogen and oxygen that contains less than 78% nitrogen. In the usual application, underwater diving, nitrox is normally distinguished from air and handled differently. The most common use of nitrox mixtures containing oxygen in higher proportions than atmospheric air is in scuba diving, where the reduced partial pressure of nitrogen is advantageous in reducing nitrogen uptake in the body's tissues, thereby extending the practicable underwater dive time by reducing the decompression requirement, or reducing the risk of decompression sickness. The two most common recreational diving nitrox mixes are 32% and 36% oxygen, which have maximum operating depths of about 110 feet and 95 feet (29 meters respectively.

<span class="mw-page-title-main">Scuba set</span> Self-contained underwater breathing apparatus

A scuba set, originally just scuba, is any breathing apparatus that is entirely carried by an underwater diver and provides the diver with breathing gas at the ambient pressure. Scuba is an anacronym for self-contained underwater breathing apparatus. Although strictly speaking the scuba set is only the diving equipment that is required for providing breathing gas to the diver, general usage includes the harness or rigging by which it is carried and those accessories which are integral parts of the harness and breathing apparatus assembly, such as a jacket or wing style buoyancy compensator and instruments mounted in a combined housing with the pressure gauge. In the looser sense, scuba set has been used to refer to all the diving equipment used by the scuba diver, though this would more commonly and accurately be termed scuba equipment or scuba gear. Scuba is overwhelmingly the most common underwater breathing system used by recreational divers and is also used in professional diving when it provides advantages, usually of mobility and range, over surface-supplied diving systems and is allowed by the relevant legislation and code of practice.

<span class="mw-page-title-main">Trimix (breathing gas)</span> Breathing gas consisting of oxygen, helium and nitrogen

Trimix is a breathing gas consisting of oxygen, helium and nitrogen and is used in deep commercial diving, during the deep phase of dives carried out using technical diving techniques, and in advanced recreational diving.

<span class="mw-page-title-main">Deep diving</span> Underwater diving to a depth beyond the norm accepted by the associated community

Deep diving is underwater diving to a depth beyond the norm accepted by the associated community. In some cases this is a prescribed limit established by an authority, while in others it is associated with a level of certification or training, and it may vary depending on whether the diving is recreational, technical or commercial. Nitrogen narcosis becomes a hazard below 30 metres (98 ft) and hypoxic breathing gas is required below 60 metres (200 ft) to lessen the risk of oxygen toxicity. At much greater depths, breathing gases become supercritical fluids, making diving with conventional equipment effectively impossible regardless of the physiological effects on the human body. Air, for example, becomes a supercritical fluid below about 400 metres (1,300 ft).

<span class="mw-page-title-main">Breathing gas</span> Gas used for human respiration

A breathing gas is a mixture of gaseous chemical elements and compounds used for respiration. Air is the most common and only natural breathing gas, but other mixtures of gases, or pure oxygen, are also used in breathing equipment and enclosed habitats. Oxygen is the essential component for any breathing gas. Breathing gases for hyperbaric use have been developed to improve on the performance of ordinary air by reducing the risk of decompression sickness, reducing the duration of decompression, reducing nitrogen narcosis or allowing safer deep diving.

<span class="mw-page-title-main">Recreational diver training</span> Training process for people who do not dive at work

Recreational diver training is the process of developing knowledge and understanding of the basic principles, and the skills and procedures for the use of scuba equipment so that the diver is able to dive for recreational purposes with acceptable risk using the type of equipment and in similar conditions to those experienced during training.

<span class="mw-page-title-main">Recreational diving</span> Diving for the purpose of leisure and enjoyment, usually when using scuba equipment

Recreational diving or sport diving is diving for the purpose of leisure and enjoyment, usually when using scuba equipment. The term "recreational diving" may also be used in contradistinction to "technical diving", a more demanding aspect of recreational diving which requires more training and experience to develop the competence to reliably manage more complex equipment in the more hazardous conditions associated with the disciplines. Breath-hold diving for recreation also fits into the broader scope of the term, but this article covers the commonly used meaning of scuba diving for recreational purposes, where the diver is not constrained from making a direct near-vertical ascent to the surface at any point during the dive, and risk is considered low.

<span class="mw-page-title-main">Gas blending for scuba diving</span> Mixing and filling cylinders with breathing gases for use when scuba diving

Gas blending for scuba diving is the filling of diving cylinders with non-air breathing gases such as nitrox, trimix and heliox. Use of these gases is generally intended to improve overall safety of the planned dive, by reducing the risk of decompression sickness and/or nitrogen narcosis, and may improve ease of breathing.

<span class="mw-page-title-main">Scuba diving</span> Swimming underwater, breathing gas carried by the diver

Scuba diving is a mode of underwater diving whereby divers use breathing equipment that is completely independent of a surface breathing gas supply, and therefore has a limited but variable endurance. The name scuba is an acronym for "Self-Contained Underwater Breathing Apparatus" and was coined by Christian J. Lambertsen in a patent submitted in 1952. Scuba divers carry their own source of breathing gas, usually compressed air, affording them greater independence and movement than surface-supplied divers, and more time underwater than free divers. Although the use of compressed air is common, a gas blend with a higher oxygen content, known as enriched air or nitrox, has become popular due to the reduced nitrogen intake during long or repetitive dives. Also, breathing gas diluted with helium may be used to reduce the effects of nitrogen narcosis during deeper dives.

Equivalent narcotic depth (END) (historically also equivalent nitrogen depth) is used in technical diving as a way of estimating the narcotic effect of a breathing gas mixture, such as nitrox, heliox or trimix. The method is used, for a given breathing gas mix and dive depth, to calculate the equivalent depth which would produce about the same narcotic effect when breathing air.

<span class="mw-page-title-main">Scuba gas planning</span> Estimation of breathing gas mixtures and quantities required for a planned dive profile

Scuba gas planning is the aspect of dive planning and of gas management which deals with the calculation or estimation of the amounts and mixtures of gases to be used for a planned dive. It may assume that the dive profile, including decompression, is known, but the process may be iterative, involving changes to the dive profile as a consequence of the gas requirement calculation, or changes to the gas mixtures chosen. Use of calculated reserves based on planned dive profile and estimated gas consumption rates rather than an arbitrary pressure is sometimes referred to as rock bottom gas management. The purpose of gas planning is to ensure that for all reasonably foreseeable contingencies, the divers of a team have sufficient breathing gas to safely return to a place where more breathing gas is available. In almost all cases this will be the surface.

<span class="mw-page-title-main">Dive planning</span> The process of planning an underwater diving operation

Dive planning is the process of planning an underwater diving operation. The purpose of dive planning is to increase the probability that a dive will be completed safely and the goals achieved. Some form of planning is done for most underwater dives, but the complexity and detail considered may vary enormously.

<span class="mw-page-title-main">Scuba gas management</span> Logistical aspects of scuba breathing gas

Scuba gas management is the aspect of scuba diving which includes the gas planning, blending, filling, analysing, marking, storage, and transportation of gas cylinders for a dive, the monitoring and switching of breathing gases during a dive, efficient and correct use of the gas, and the provision of emergency gas to another member of the dive team. The primary aim is to ensure that everyone has enough to breathe of a gas suitable for the current depth at all times, and is aware of the gas mixture in use and its effect on decompression obligations, nitrogen narcosis, and oxygen toxicity risk. Some of these functions may be delegated to others, such as the filling of cylinders, or transportation to the dive site, but others are the direct responsibility of the diver using the gas.

<span class="mw-page-title-main">Decompression equipment</span> Equipment used by divers to facilitate decompression

There are several categories of decompression equipment used to help divers decompress, which is the process required to allow divers to return to the surface safely after spending time underwater at higher ambient pressures.

<span class="mw-page-title-main">History of scuba diving</span>

The history of scuba diving is closely linked with the history of the equipment. By the turn of the twentieth century, two basic architectures for underwater breathing apparatus had been pioneered; open-circuit surface supplied equipment where the diver's exhaled gas is vented directly into the water, and closed-circuit breathing apparatus where the diver's carbon dioxide is filtered from the exhaled breathing gas, which is then recirculated, and more gas added to replenish the oxygen content. Closed circuit equipment was more easily adapted to scuba in the absence of reliable, portable, and economical high pressure gas storage vessels. By the mid-twentieth century, high pressure cylinders were available and two systems for scuba had emerged: open-circuit scuba where the diver's exhaled breath is vented directly into the water, and closed-circuit scuba where the carbon dioxide is removed from the diver's exhaled breath which has oxygen added and is recirculated. Oxygen rebreathers are severely depth limited due to oxygen toxicity risk, which increases with depth, and the available systems for mixed gas rebreathers were fairly bulky and designed for use with diving helmets. The first commercially practical scuba rebreather was designed and built by the diving engineer Henry Fleuss in 1878, while working for Siebe Gorman in London. His self contained breathing apparatus consisted of a rubber mask connected to a breathing bag, with an estimated 50–60% oxygen supplied from a copper tank and carbon dioxide scrubbed by passing it through a bundle of rope yarn soaked in a solution of caustic potash. During the 1930s and all through World War II, the British, Italians and Germans developed and extensively used oxygen rebreathers to equip the first frogmen. In the U.S. Major Christian J. Lambertsen invented a free-swimming oxygen rebreather. In 1952 he patented a modification of his apparatus, this time named SCUBA, an acronym for "self-contained underwater breathing apparatus," which became the generic English word for autonomous breathing equipment for diving, and later for the activity using the equipment. After World War II, military frogmen continued to use rebreathers since they do not make bubbles which would give away the presence of the divers. The high percentage of oxygen used by these early rebreather systems limited the depth at which they could be used due to the risk of convulsions caused by acute oxygen toxicity.

<span class="mw-page-title-main">Outline of underwater diving</span> List of articles related to underwater diving grouped by topical relevance

The following outline is provided as an overview of and topical guide to underwater diving:

References

  1. ↑ Richardson, Drew (2003). "Taking 'tec' to 'rec': the future of technical diving" (PDF). South Pacific Underwater Medicine Society Journal. 33 (4). Retrieved 28 March 2023.
  2. ↑ Gilliam, Bret (1995-01-25). Deep Diving. p. 15. ISBN   978-0-922769-31-5 . Retrieved 2009-09-14.
  3. ↑ Menduno, Michael (July 2019). "The Technical Diving Revolution – part 2". DIVER Magazine.
  4. 1 2 3 4 Yount, David E.; Maiken, Eric B.; Baker, Erik C. (2000). Lang, M.A.; Lehner, C.E. (eds.). Implications of the Varying Permeability Model for Reverse Dive Profiles. Proceedings of the Reverse Dive Profiles Workshop, October 29–30, 1999. Washington, D.C.: Smithsonian Institution. pp. 29–60.
  5. 1 2 Menduno, Michael (18–20 May 2012). Vann, Richard D.; Denoble, Petar J.; Pollock, Neal W. (eds.). Building a consumer rebreather market: Lessons from the technical diving revolution (PDF). Rebreather Forum 3 Proceedings. Durham, North Carolina: AAUS/DAN/PADI. pp. 2–23. ISBN   978-0-9800423-9-9.
  6. ↑ "Diving Regulations 2009". Occupational Health and Safety Act 85 of 1993 – Regulations and Notices – Government Notice R41. Pretoria: Government Printer. Archived from the original on 2016-11-04. Retrieved 3 November 2016– via Southern African Legal Information Institute.
  7. 1 2 3 4 5 6 Menduno, Michael (June 2019). "The Technical Diving Revolution – part 2". DIVER Magazine.
  8. ↑ Menduno, Michael (August 2019). "The Technical Diving Revolution – part 3". DIVER Magazine.
  9. ↑ Gorman, Des F. (1992). "High-tech diving". South Pacific Underwater Medicine Society Journal. 22 (1).
  10. ↑ Gorman, Des F. (1995). "Safe Limits: A International Dive Symposium. Introduction". South Pacific Underwater Medicine Society Journal. 25 (1). Archived from the original on April 15, 2013. Retrieved 2009-08-07.{{cite journal}}: CS1 maint: unfit URL (link)
  11. ↑ Hamilton, R. W. Jr. (1996). "What is technical diving? (letter to editor)". South Pacific Underwater Medicine Society Journal. 26 (1).
  12. ↑ Rossier, Robert N. (January 2000). Recreational Nitrox Diving (1 ed.). Best Publishing Company. ISBN   978-0941332835.
  13. ↑ Douglas, Eric (2011). "Nitrox". Alert Diver online - Fall 2011. Divers Alert Network. Archived from the original on 31 May 2016. Retrieved 25 April 2016.
  14. ↑ Staff (2016). "Recreational Diver Level 1 - Nitrox diver". Global Underwater Explorers website. Global Underwater Explorers. Retrieved 25 April 2016.
  15. ↑ Menduno, Michael (2014). "Rise of the Recreational Rebreather". Diver magazine - online. Diver magazine. Retrieved 25 April 2016.
  16. ↑ Staff (2016). "Explorer rebreather". Hollis website. Hollis. Archived from the original on 20 April 2016. Retrieved 25 April 2016.
  17. ↑ Staff (2016). "Rebreather diver". PADI website. PADI. Retrieved 25 April 2016.
  18. ↑ "What is "Technical" Diving?". ANDI. 2015. Retrieved 31 July 2016.
  19. 1 2 3 Gurr, Kevin (August 2008). "13: Operational safety". In Mount, Tom; Dituri, Joseph (eds.). Exploration and Mixed Gas Diving Encyclopedia (1st ed.). Miami Shores, Florida: International Association of Nitrox Divers. p. 173. ISBN   978-0-915539-10-9.
  20. ↑ Staff. "Technical Diving". www.naui.org. National Association of Underwater Instructors. Retrieved 14 January 2017.
  21. ↑ "Technical Diving". NOAA. 24 February 2006. Retrieved 25 September 2008.
  22. ↑ PADI, Enriched Air Diving, page 91. ISBN   978-1-878663-31-3
  23. ↑ Staff. "Technical Diving International". Our story. SDI - TDI - ERDI. Retrieved 17 January 2017.
  24. ↑ Staff (2 December 2011). "Recreational Diving, Recreational Technical Diving and Snorkelling Code of Practice 2011" (PDF). Queensland Government Gazette. The State of Queensland (Department of Justice and Attorney-General). Retrieved 25 April 2017.
  25. ↑ "Technical diving - British Sub-Aqua Club" . Retrieved 2 October 2017.
  26. 1 2 3 Cole, Bob (March 2008). "System Definitions". The Bühlmann Deep-Stop System Handbook. Sub-Aqua Association. pp. 2–2, 2–3. ISBN   978-0953290482.
  27. ↑ Cole, Bob (2009). "Appendix 1 - Overview". Student Diver Tool Box. Sub-Aqua Association. pp. A1–9–10. ISBN   978-0-9532904-9-9.
  28. ↑ "PADI Deep Diver". Archived from the original on 2002-12-05.
  29. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 Mitchell, S. J. (1 May 2004). In: Moon, R.E.; Piantadosi, C.A.; Camporesi, E.M. (eds.). Technical Diving. Dr. Peter Bennett Symposium Proceedings. (Report). Durham, N.C.: Divers Alert Network.
  30. ↑ Carney, Brian; Bissett, Donna (2012). A guide to advanced nitrox : the full spectrum of nitrox mixtures. Jensen Beach, Florida: Technical Diving International. ISBN   978-1931451758. OCLC   990167469.
  31. 1 2 Staff (2024). "Diver-Level Courses". PADI website. PADI. Retrieved 9 May 2024.
  32. ↑ "RESA". Rebreather Education & Safety Association. Retrieved 2017-11-21.
  33. ↑ "Technical Diver Courses | NAUI Worldwide. Dive Safety Through Education". NAUI. Retrieved 2017-11-21.
  34. ↑ Dreher, Richard (2013). Diving in overhead environments : your complete guide to cavern and cave diving. Jensen Beach, FL, USA: Technical Diving International. ISBN   978-1931451710. OCLC   985481420.
  35. ↑ Doolette, David J. (August 2008). "2: Inert Gas Narcosis". In Mount, Tom; Dituri, Joseph (eds.). Exploration and Mixed Gas Diving Encyclopedia (1st ed.). Miami Shores, Florida: International Association of Nitrox Divers. pp. 33–40. ISBN   978-0-915539-10-9.
  36. 1 2 Tydeman, Bill. "What is Technical Diving?". Viking Dives. Retrieved 15 March 2024.
  37. ↑ Gilliam, Bret (March 2015). "Soft Ceilings Can Be Just As Hard". Tech Diving Mag (18). www.techdivingmag.com: 3–6.
  38. ↑ Lang, M. A.; Sayer, M.D.J., eds. (2007). Proceedings of the International Polar Diving Workshop (PDF). Svalbard: Smithsonian Institution. pp. 211–213. Retrieved 28 March 2023.
  39. ↑ Devos, Fred; Le Maillot, Chris; Riordan, Daniel (2004). "Introduction to Guideline Procedures - Part 2: Methods" (PDF). DIRquest. 5 (4). Global Underwater Explorers . Retrieved 2016-06-21.
  40. ↑ Exley, Sheck (1977). Basic Cave Diving: A Blueprint for Survival. National Speleological Society Cave Diving Section. ISBN   99946-633-7-2.
  41. ↑ Staff (13 April 2010). "Using Multiple Cylinders". Sport Diver. PADI Diving Society. Retrieved 3 January 2017.
  42. ↑ Mount, Tom (August 2008). "11: Dive Planning". In Mount, Tom; Dituri, Joseph (eds.). Exploration and Mixed Gas Diving Encyclopedia (1st ed.). Miami Shores, Florida: International Association of Nitrox Divers. pp. 113–158. ISBN   978-0-915539-10-9.
  43. ↑ Mount, Tom (August 2008). "9: Equipment Configuration". In Mount, Tom; Dituri, Joseph (eds.). Exploration and Mixed Gas Diving Encyclopedia (1st ed.). Miami Shores, Florida: International Association of Nitrox Divers. pp. 91–106. ISBN   978-0-915539-10-9.
  44. ↑ Beresford, M.; Southwood, P. (2006). CMAS-ISA Normoxic Trimix Manual (4th ed.). Pretoria, South Africa: CMAS Instructors South Africa.
  45. ↑ "TDI Helitrox Diver". SDI | TDI | ERDI. Retrieved 2017-11-21.
  46. ↑ IANTD. "IANTD World Headquarters - Advanced Recreational Trimix Diver (OC, Rebreather)" . Retrieved 2017-11-21.
  47. ↑ Brittain, Colin (2004). "Diving Air and Deep Diving". Let's Dive: Sub-Aqua Association Club Diver Manual (2nd ed.). Wigan, UK: Dive Print. p. 80. ISBN   0-9532904-3-3. The Association strongly endorses a maximum depth of 50 metres (50 metres (160 ft))
  48. ↑ Staff (15 November 2016). "Plongeur Encadre 60 m" (PDF). Manuel de Formation Technique (in French). FFESSM. p. 1. Retrieved 17 January 2017. Le plongeur titulaire de la qualification PE60 est capable d'évoluer en exploration dans l'espace 0 - 60 m au sein d'une palanquée prise en charge par un Guide de Palanquée (E4)
  49. ↑ Commission Formation (August 2012). "Plongeur autonome 60m" (PDF). Manuel du Moniteur (in French). FSGT. p. 52. Archived from the original (PDF) on 4 August 2016. Retrieved 17 January 2017. Ce module doit permettre de compléter l'expérience d'un plongeur autonome confirmé qui souhaiterait évoluer à l'air et en sécurité dans l'espace sub-lointain (40 à 60m).
  50. ↑ "Les brevets de plongeur et les qualifications". Cursus Air (in French). ANMP. Retrieved 17 January 2017.
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  53. ↑ NOAA Diving Program (U.S.) (28 Feb 2001). Joiner, James T. (ed.). NOAA Diving Manual, Diving for Science and Technology (4th ed.). Silver Spring, Maryland: National Oceanic and Atmospheric Administration, Office of Oceanic and Atmospheric Research, National Undersea Research Program. ISBN   978-0-941332-70-5. CD-ROM prepared and distributed by the National Technical Information Service (NTIS)in partnership with NOAA and Best Publishing Company
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  55. ↑ Jablonski, Jarrod (2006). Doing it Right: The Fundamentals of Better Diving. Global Underwater Explorers. ISBN   0-9713267-0-3.
  56. ↑ Bishop, Leigh (6 May 2020). "The Logistics of Exploration". www.dansa.org. DAN Southern Africa. Retrieved 26 March 2023.
  57. ↑ "SSI TechXR - Technical diving program". Scuba Schools International. Retrieved 2009-06-22.

Footnotes

  1. ↑ In his 1989 book, Advanced Wreck Diving, author and technical diver, Gary Gentile, commented that there was no accepted term for divers who dived beyond agency-specified recreational limits for non-professional purposes. Revised editions use the term technical diving, and Gary Gentile published a further book in 1999 entitled The Technical Diving Handbook.
  2. ↑ Some recreational diving agencies recommend diving no deeper than 30 metres (100 ft), and suggest an absolute limit of 40 metres (130 ft). This has changed over time, and the PADI Deep Diver certification changed from 18 to 30 m max, to 18 to 40 m.
  3. ↑ There is a reasonable body of professional opinion that considers decompression diving to be the sole differentiator for "technical" diving, but another body of professional opinion that considers all dives to be decompression dives. The distinction is between dives for which there is no obligatory decompression stop, and dives for which the decompression planning system (dive computer or schedule) indicates a requirement for a decompression stop. The same dive profile may or may not require a stop, depending on the system used to monitor the profile and the algorithm chosen to model decompression requirements.
  4. ↑ Some certification agencies prefer to the term "cavern diving" to cave penetration within recreational diving limits.
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