Sailors check breathing devices at sea.

Trimix scuba cylinder label

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 such as scuba equipment, surface supplied diving equipment, recompression chambers, high-altitude mountaineering, high-flying aircraft, submarines, space suits, spacecraft, medical life support and first aid equipment, and anaesthetic machines.[1][2][3]

Oxygen is the essential component for any breathing gas, at a partial pressure of between roughly 0.16 and 1.60 bar at the ambient pressure. The oxygen is usually the only metabolically active component unless the gas is an anaesthetic mixture. Some of the oxygen in the breathing gas is consumed by the metabolic processes, and the inert components are unchanged, and serve mainly to dilute the oxygen to an appropriate concentration, and are therefore also known as diluent gases. Most breathing gases therefore are a mixture of oxygen and one or more inert gases.[1][3] Other breathing gases have been developed to improve on the performance of ordinary air by reducing the risk of decompression sickness, reducing the duration of decompression stops, reducing nitrogen narcosis or allowing safer deep diving.[1][3]

A safe breathing gas for hyperbaric use has three essential features:

* It must contain sufficient oxygen to support life, consciousness and work rate of the breather.[1][2][3]
* It must not contain harmful contaminants. Carbon monoxide and carbon dioxide are common poisons which may contaminate breathing gases. There are many other possibilities.[1][2][3]
* It must not become toxic when being breathed at high pressure such as when underwater. Oxygen and nitrogen are examples of gases that become toxic under pressure.[1][2][3]

The techniques used to fill diving cylinders with gases other than air are called gas blending.[4][5]

Breathing gases for use at ambient pressures below normal atmospheric pressure are usually air enriched with oxygen to provide sufficient oxygen to maintain life and consciousness, or to allow higher levels of exertion than would be possible using air. It is common to provide the additional oxygen as a pure gas added to the breathing air at inhalation, or though a life-support system.

## Contents

* 1 For diving and other hyperbaric use
* 1.1 Breathing air
* 1.2 Classification by oxygen fraction
* 1.3 Individual component gases
* 1.3.1 Oxygen
* 1.3.2 Nitrogen
* 1.3.3 Helium
* 1.3.4 Neon
* 1.3.5 Hydrogen
* 1.4 Unwelcome components of breathing gases for diving
* 1.4.1 Argon
* 1.4.2 Carbon dioxide
* 1.4.3 Carbon monoxide
* 1.4.4 Hydrocarbons
* 1.5 Moisture content
* 1.6 Gas analysis
* 1.7 Breathing gas standards
* 1.8 Diving gas blending
* 2 Hypobaric breathing gases
* 3 Medical breathing gases
* 3.1 Oxygen therapy
* 3.2 Anaesthetic gases
* 3.2.1 Administration
* 4 See also
* 5 References
* 6 External links

## For diving and other hyperbaric use[edit | edit source]

A closed bell used for saturation diving showing emergency gas supply cylinders

These common diving breathing gases are used:

* Air is a mixture of 21% oxygen, 78% nitrogen, and approximately 1% other trace gases, primarily argon; to simplify calculations this last 1% is usually treated as if it were nitrogen. Being cheap and simple to use, it is the most common diving gas.[1][2][3] As its nitrogen component causes nitrogen narcosis, it is considered to have a safe depth limit of about 40 metres (130 feet) for most divers, although the maximum operating depth of air taking an allowable oxygen partial pressure of 1,6 bar is 66.2 metres (218 feet).[1][3][6] Breathing air is air meeting specified standards for contaminants.
* Pure oxygen is mainly used to speed the shallow decompression stops at the end of a military, commercial, or technical dive. Risk of acute oxygen toxicity increases rapidly at pressures greater than 6 metres sea water.[1][2][3][6] It was much used in frogmen's rebreathers, and is still used by attack swimmers.[2][6][7][8]
* Nitrox is a mixture of oxygen and air, and generally refers to mixtures which are more than 21% oxygen. It can be used as a tool to accelerate in-water decompression stops or to decrease the risk of decompression sickness and thus prolong a dive (a common misconception is that the diver can go deeper, this is not true owing to a shallower maximum operating depth than on conventional air).[1][2][3][9]
* Trimix is a mixture of oxygen, nitrogen and helium and is often used at depth in technical diving and commercial diving instead of air to reduce nitrogen narcosis and to avoid the dangers of oxygen toxicity.[1][2][3]
* Heliox is a mixture of oxygen and helium and is often used in the deep phase of a commercial deep dive to eliminate nitrogen narcosis.[1][2][3][10]
* Heliair is a form of trimix that is easily blended from helium and air without using pure oxygen. It always has a 21:79 ratio of oxygen to nitrogen; the balance of the mix is helium.[3][11]
* Hydreliox is a mixture of oxygen, helium, and hydrogen and is used for dives below 130 metres in commercial diving.[1][3][10][12][13]
* Hydrox, a gas mixture of hydrogen and oxygen, is used as a breathing gas in very deep diving.[1][3][10][12][14]
* Neox (also called neonox) is a mixture of oxygen and neon sometimes employed in deep commercial diving. It is rarely used due to its cost. Also, DCS symptoms produced by neon ("neox bends") have a poor reputation, being widely reported to be more severe than those produced by an exactly equivalent dive-table and mix with helium.[1][3][10][15]

Commonly accepted breathing gas container colour coding in the offshore diving industry.[16] Gas  | Symbol  | Typical shoulder colours  | Cylinder shoulder  | Quad upper frame/
frame valve end

|
|
|
|

Medical oxygen  | O2 |

| White  | White
Oxygen and helium mixtures
(Heliox)  | O2/He  |  | Brown and white
quarters or bands  | Brown and white
short (8 inches (20 cm))
alternating bands
Oxygen, helium and nitrogen
mixtures (Trimix)  | O2/He/N2 |  | Black, white and brown
quarters or bands  | Black, white and brown
short (8 inches (20 cm))
alternating bands
Oxygen and nitrogen mixtures
(Nitrox) including air  | N2/O2 |  | Black and white
quarters or bands  | Black and white
short (8 inches (20 cm))
alternating bands

### Breathing air[edit | edit source]

Breathing air is atmospheric air with a standard of purity suitable for human breathing in the specified application. For hyperbaric use the partial pressure of contaminants is increased in proportion to the absolute pressure, and must be limited to a safe composition for the depth or pressure range in which it is to be used.

### Classification by oxygen fraction[edit | edit source]

Breathing gases for diving are classified by oxygen fraction. The boundaries set by authorities may differ slightly, as the effects vary gradually with concentration and between people, and are not accurately predictable.[citation needed]

Normoxic
where the oxygen content does not differ greatly from that of air and allows continuous safe use at atmospheric pressure.[citation needed]
Hyperoxic, or oxygen enriched
where the oxygen content exceeds atmospheric levels, generally to a level where there is some measurable physiological effect over long term use, and sometimes requiring special procedures for handling due to increased fire hazard. The associated risks are oxygen toxicity at depth and fire, particularly in the breathing apparatus.[citation needed]
Hypoxic
where the oxygen content is less than that of air, generally to the extent that there is a significant risk of measurable physiological effect over the short term. The immediate risk is usually hypoxic incapacitation at or near the surface.[citation needed]

### Individual component gases[edit | edit source]

Breathing gases for diving are mixed from a small number of component gases which provide special characteristics to the mixture which are not available from atmospheric air.

#### Oxygen[edit | edit source]

For the main article on the medical use of oxygen, see oxygen therapy.

Oxygen (O2) must be present in every breathing gas.[1][2][3] This is because it is essential to the human body's metabolic process, which sustains life. The human body cannot store oxygen for later use as it does with food. If the body is deprived of oxygen for more than a few minutes, unconsciousness and death result. The tissues and organs within the body (notably the heart and brain) are damaged if deprived of oxygen for much longer than four minutes.

Filling a diving cylinder with pure oxygen costs around five times more than filling it with compressed air. As oxygen supports combustion and causes rust in diving cylinders, it should be handled with caution when gas blending.[4][5]

Oxygen has historically been obtained by fractional distillation of liquid air, but is increasingly obtained by non-cryogenic technologies such as pressure swing adsorption (PSA) and vacuum swing adsorption (VSA) technologies.[17]

The fraction of the oxygen component of a breathing gas mixture is sometimes used when naming the mix:

* hypoxic mixes, strictly, contain less than 21% oxygen, although often a boundary of 16% is used, and are designed only to be breathed at depth as a "bottom gas" where the higher pressure increases the partial pressure of oxygen to a safe level.[1][2][3] Trimix, Heliox and Heliair are gas blends commonly used for hypoxic mixes and are used in professional and technical diving as deep breathing gases.[1][3]
* normoxic mixes have the same proportion of oxygen as air, 21%.[1][3] The maximum operating depth of a normoxic mix could be as shallow as 47 metres (155 feet). Trimix with between 17% and 21% oxygen is often described as normoxic because it contains a high enough proportion of oxygen to be safe to breathe at the surface.
* hyperoxic mixes have more than 21% oxygen. Enriched Air Nitrox (EANx) is a typical hyperoxic breathing gas.[1][3][9] Hyperoxic mixtures, when compared to air, cause oxygen toxicity at shallower depths but can be used to shorten decompression stops by drawing dissolved inert gases out of the body more quickly.[6][9]

The fraction of the oxygen determines the greatest depth at which the mixture can safely be used to avoid oxygen toxicity. This depth is called the maximum operating depth.[1][3][6][9]

The concentration of oxygen in a gas mix depends on the fraction and the pressure of the mixture. It is expressed by the partial pressure of oxygen (PO2).[1][3][6][9]

The partial pressure of any component gas in a mixture is calculated as:

partial pressure = total absolute pressure × volume fraction of gas component

For the oxygen component,

PO2 = P × FO2

where:

PO2 = partial pressure of oxygen
P = total pressure
FO2 = volume fraction of oxygen content

The minimum safe partial pressure of oxygen in a breathing gas is commonly held to be 16 kPa (0.16 bar). Below this partial pressure the diver may be at risk of unconsciousness and death due to hypoxia, depending on factors including individual physiology and level of exertion. When a hypoxic mix is breathed in shallow water it may not have a high enough PO2 to keep the diver conscious. For this reason normoxic or hyperoxic "travel gases" are used at medium depth between the "bottom" and "decompression" phases of the dive.

The maximum safe PO2 in a breathing gas depends on exposure time, the level of exercise and the security of the breathing equipment being used. It is typically between 100 kPa (1 bar) and 160 kPa (1.6 bar); for dives of less than three hours it is commonly considered to be 140 kPa (1.4 bar), although the U.S. Navy has been known to authorize dives with a PO2 of as much as 180 kPa (1.8 bar).[1][2][3][6][9] At high PO2 or longer exposures, the diver risks oxygen toxicity which may result in a seizure.[1][2] Each breathing gas has a maximum operating depth that is determined by its oxygen content.[1][2][3][6][9] For therapeutic recompression and hyperbaric oxygen therapy partial pressures of 2.8 bar are commonly used in the chamber, but there is no risk of drowning if the occupant loses consciousness.[2]

Oxygen analysers are used to measure the oxygen partial pressure in the gas mix.[4]

Divox  is breathing grade oxygen labelled for diving use. In the Netherlands, pure oxygen for breathing purposes is regarded as medicinal as opposed to industrial oxygen, such as that used in welding, and is only available on medical prescription. The diving industry registered Divox as a trademark for breathing grade oxygen to circumvent the strict rules concerning medicinal oxygen thus making it easier for (recreational) scuba divers to obtain oxygen for blending their breathing gas. In most countries, there is no difference in purity in medical oxygen and industrial oxygen, as they are produced by exactly the same methods and manufacturers, but labeled and filled differently. The chief difference between them is that the record-keeping trail is much more extensive for medical oxygen, to more easily identify the exact manufacturing trail of a "lot" or batch of oxygen, in case problems with its purity are discovered. Aviation grade oxygen is similar to medical oxygen, but may have a lower moisture content.[4]

#### Nitrogen[edit | edit source]

Nitrogen (N2) is a diatomic gas and the main component of air, the cheapest and most common breathing gas used for diving. It causes nitrogen narcosis in the diver, so its use is limited to shallower dives. Nitrogen can cause decompression sickness.[1][2][3][18]

Equivalent air depth is used to estimate the decompression requirements of a nitrox (oxygen/nitrogen) mixture. Equivalent narcotic depth is used to estimate the narcotic potency of trimix (oxygen/helium/nitrogen mixture). Many divers find that the level of narcosis caused by a 30 m (100 ft) dive, whilst breathing air, is a comfortable maximum.[1][2][3][19][20]

Nitrogen in a gas mix is almost always obtained by adding air to the mix.

#### Helium[edit | edit source]

2% Heliox storage quad. 2% oxygen by volume is sufficient at pressures exceeding 90 msw.

Helium (He) is an inert gas that is less narcotic than nitrogen at equivalent pressure (in fact there is no evidence for any narcosis from helium at all), so it is more suitable for deeper dives than nitrogen.[1][3] Helium is equally able to cause decompression sickness. At high pressures, helium also causes high-pressure nervous syndrome, which is a central nervous system irritation syndrome which is in some ways opposite to narcosis.[1][2][3][21]

Helium mixture fills are considerably more expensive than air fills due to the cost of helium and the cost of mixing and compressing the mix.[citation needed][clarification needed]

Helium is not suitable for dry suit inflation owing to its poor thermal insulation properties – compared to air, which is regarded as a reasonable insulator, helium has six times the thermal conductivity.[22] Helium's low molecular weight (monatomic MW=4, compared with diatomic nitrogen MW=28) increases the timbre of the breather's voice, which may impede communication.[1][3][23] This is because the speed of sound is faster in a lower molecular weight gas, which increases the resonance frequency of the vocal cords.[1][23] Helium leaks from damaged or faulty valves more readily than other gases because atoms of helium are smaller allowing them to pass through smaller gaps in seals.

Helium is found in significant amounts only in natural gas, from which it is extracted at low temperatures by fractional distillation.

#### Neon[edit | edit source]

"Neox" redirects here. For the Spanish broadcaster, see Neox (TV channel).

Neon (Ne) is an inert gas sometimes used in deep commercial diving but is very expensive.[1][3][10][15] Like helium, it is less narcotic than nitrogen, but unlike helium, it does not distort the diver's voice. Compared to helium, neon has superior thermal insulating properties.[24]

#### Hydrogen[edit | edit source]

Hydrogen (H2) has been used in deep diving gas mixes but is very explosive when mixed with more than about 4 to 5% oxygen (such as the oxygen found in breathing gas).[1][3][10][12] This limits use of hydrogen to deep dives and imposes complicated protocols to ensure that excess oxygen is cleared from the breathing equipment before breathing hydrogen starts. Like helium, it raises the timbre of the diver's voice. The hydrogen-oxygen mix when used as a diving gas is sometimes referred to as Hydrox. Mixtures containing both hydrogen and helium as diluents are termed Hydreliox.

### Unwelcome components of breathing gases for diving[edit | edit source]

Many gases are not suitable for use in diving breathing gases.[5][25] Here is an incomplete list of gases commonly present in a diving environment:

#### Argon[edit | edit source]

Argon (Ar) is an inert gas that is more narcotic than nitrogen, so is not generally suitable as a diving breathing gas.[26] Argox is used for decompression research.[1][3][27][28] It is sometimes used for dry suit inflation by divers whose primary breathing gas is helium-based, because of argon's good thermal insulation properties. Argon is more expensive than air or oxygen, but considerably less expensive than helium. Argon is a component of natural air, and constitutes 0.934% by volume of the Earth's atmosphere.[29]

#### Carbon dioxide[edit | edit source]

Carbon dioxide (CO2) is produced by the metabolism in the human body and can cause carbon dioxide poisoning.[25][30][31] When breathing gas is recycled in a rebreather or life support system, the carbon dioxide is removed by scrubbers before the gas is re-used.

#### Carbon monoxide[edit | edit source]

Carbon monoxide (CO) is produced by incomplete combustion.[1][2][5][25] See carbon monoxide poisoning. Four common sources are:

* Internal combustion engine exhaust gas containing CO in the air being drawn into a diving air compressor. CO in the intake air cannot be stopped by any filter. The exhausts of all internal combustion engines running on petroleum fuels contain some CO, and this is a particular problem on boats, where the intake of the compressor cannot be arbitrarily moved as far as desired from the engine and compressor exhausts.
* Heating of lubricants inside the compressor may vaporize them sufficiently to be available to a compressor intake or intake system line.
* In some cases hydrocarbon lubricating oil may be drawn into the compressor's cylinder directly through damaged or worn seals, and the oil may (and usually will) then undergo combustion, being ignited by the immense compression ratio and subsequent temperature rise. Since heavy oils don't burn well – especially when not atomized properly – incomplete combustion will result in carbon monoxide production.
* A similar process is thought[by whom?][original research?] to potentially happen to any particulate material, which contains "organic" (carbon-containing) matter, especially in cylinders which are used for hyperoxic gas mixtures. If the compressor air filter(s) fail, ordinary dust will be introduced to the cylinder, which contains organic matter (since it usually contains humus). A more severe danger is that air particulates on boats and industrial areas, where cylinders are filled, often contain carbon-particulate combustion products (these are what makes a dirt rag black), and these represent a more severe CO danger when introduced into a cylinder.[citation needed]

Carbon monoxide is generally avoided as far as is reasonably practicable by positioning of the air intake in uncontaminated air, filtration of particulates from the intake air, use of suitable compressor design and appropriate lubricants, and ensuring that running temperatures are not excessive. Where the residual risk is excessive, a hopcalite catalyst can be used in the high pressure filter to convert carbon monoxide into carbon dioxide, which is far less toxic.

#### Hydrocarbons[edit | edit source]

Hydrocarbons (CxHy) are present in compressor lubricants and fuels. They can enter diving cylinders as a result of contamination, leaks,[clarification needed] or due to incomplete combustion near the air intake.[2][4][5][25][32]

* They can act as a fuel in combustion increasing the risk of explosion, especially in high-oxygen gas mixtures.
* Inhaling oil mist can damage the lungs and ultimately cause the lungs to degenerate with severe lipid pneumonia[33] or emphysema.

### Moisture content[edit | edit source]

The process of compressing gas into a diving cylinder removes moisture from the gas.[5][25] This is good for corrosion prevention in the cylinder but means that the diver inhales very dry gas. The dry gas extracts moisture from the diver's lungs while underwater contributing to dehydration, which is also thought to be a predisposing risk factor of decompression sickness. It is also uncomfortable, causing a dry mouth and throat and making the diver thirsty. This problem is reduced in rebreathers because the soda lime reaction, which removes carbon dioxide, also puts moisture back into the breathing gas.[8] In hot climates, open circuit diving can accelerate heat exhaustion because of dehydration. Another concern with regard to moisture content is the tendency of moisture to condense as the gas is decompressed while passing through the regulator; this coupled with the extreme reduction in temperature, also due to the decompression can cause the moisture to solidify as ice. This icing up in a regulator can cause moving parts to seize and the regulator to fail or free flow. This is one of the reasons that scuba regulators are generally constructed from brass, and chrome plated (for protection). Brass, with its good thermal conductive properties, quickly conducts heat from the surrounding water to the cold, newly decompressed air, helping to prevent icing up.

### Gas analysis[edit | edit source]

Electro-galvanic fuel cell as used in a diving rebreather

Gas mixtures must generally be analysed either in process or after blending for quality control. This is particularly important for breathing gas mixtures where errors can affect the health and safety of the end user. It is difficult to detect most gases that are likely to be present in diving cylinders because they are colourless, odourless and tasteless. Electronic sensors exist for some gases, such as oxygen analysers, helium analyser, carbon monoxide detectors and carbon dioxide detectors.[2][4][5] Oxygen analysers are commonly found underwater in rebreathers.[8] Oxygen and helium analysers are often used on the surface during gas blending to determine the percentage of oxygen or helium in a breathing gas mix.[4] Chemical and other types of gas detection methods are not often used in recreational diving, but are used for periodical quality testing of compressed breathing air from diving air compressors.[4]

### Breathing gas standards[edit | edit source]

Standards for breathing gas quality are published by national and international organisations, and may be enforced in terms of legislation. In the UK, the Health and Safety Executive indicate that the requirements for breathing gases for divers are based on the BS EN 12021:2014. The specifications are listed for oxygen compatible air, nitrox mixtures produced by adding oxygen, removing nitrogen, or mixing nitrogen and oxygen, mixtures of helium and oxygen (heliox), mixtures of helium, nitrogen and oxygen (trimix), and pure oxygen, for both open circuit and reclaim systems, and for high pressure and low pressure supply (above and below 40 bar supply).[34]

Oxygen content is variable depending on the operating depth, but the tolerance depends on the gas fraction range, being ±0.25% for an oxygen fraction below 10% by volume, ±0.5% for a fraction between 10% and 20%, and ±1% for a fraction over 20%.[34]

Water content is limited by risks of icing of control valves, and corrosion of containment surfaces – higher humidity is not a physiological problem – and is generally a factor of dew point.[34]

Other specified contaminants are carbon dioxide, carbon monoxide, oil, and volatile hydrocarbons, which are limited by toxic effects. Other possible contaminants should be analysed based on risk assessment, and the required frequency of testing for contaminants is also based on risk assessment.[34]

In Australia breathing air quality is specified by Australian Standard 2299.1, Section 3.13 Breathing Gas Quality.[35]

### Diving gas blending[edit | edit source]

Main article: Gas blending for scuba diving

Air, oxygen and helium partial pressure gas blending system

Nitrox continuous blending compressor installation

Gas blending (or Gas mixing) of breathing gases for diving is the filling of gas cylinders with non-air breathing gases.

Filling cylinders with a mixture of gases has dangers for both the filler and the diver. During filling there is a risk of fire due to use of oxygen and a risk of explosion due to the use of high-pressure gases. The composition of the mix must be safe for the depth and duration of the planned dive. If the concentration of oxygen is too lean the diver may lose consciousness due to hypoxia and if it is too rich the diver may suffer oxygen toxicity. The concentration of inert gases, such as nitrogen and helium, are planned and checked to avoid nitrogen narcosis and decompression sickness.

Methods used include batch mixing by partial pressure or by mass fraction, and continuous blending processes. Completed blends are analysed for composition for the safety of the user. Gas blenders may be required by legislation to prove competence if filling for other persons.

## Hypobaric breathing gases[edit | edit source]

Astronaut in an Orlan space suit, outside the International Space Station

Breathing gases for use at reduced ambient pressure are used for high altitude flight in unpressurised aircraft, in space flight, particularly in space suits, and for high altitude mountaineering. In all these cases, the primary consideration is providing an adequate partial pressure of oxygen. In some cases the breathing gas has oxygen added to make up a sufficient concentration, and in other cases the breathing gas may be pure or nearly pure oxygen.[citation needed] Closed circuit systems may be used to conserve the breathing gas, which may be in limited supply - in the case of mountaineering the user must carry the supplemental oxygen, and in space flight the cost of lifting mass into orbit is very high.

## Medical breathing gases[edit | edit source]

Medical use of breathing gases other than air include oxygen therapy and anesthesia applications.

### Oxygen therapy[edit | edit source]

Main article: Oxygen therapy

A person wearing a simple face mask for oxygen therapy

Oxygen is required by people for normal cell metabolism.[36] Air is typically 21% oxygen by volume.[37] This is normally sufficient, but in some circumstances the oxygen supply to tissues is compromised.

Oxygen therapy, also known as supplemental oxygen, is the use of oxygen as a medical treatment.[38] This can include for low blood oxygen, carbon monoxide toxicity, cluster headaches, and to maintain enough oxygen while inhaled anesthetics are given.[39] Long term oxygen is often useful in people with chronically low oxygen such as from severe COPD or cystic fibrosis.[40][38] Oxygen can be given in a number of ways including nasal cannula, face mask, and inside a hyperbaric chamber.[41][42]

High concentrations of oxygen can cause oxygen toxicity such as lung damage or result in respiratory failure in those who are predisposed.[39][37] It can also dry out the nose and increase the risk of fires in those who smoke. The target oxygen saturation recommended depends on the condition being treated. In most conditions a saturation of 94-98% is recommended, while in those at risk of carbon dioxide retention saturations of 88-92% are preferred, and in those with carbon monoxide toxicity or cardiac arrest the saturation should be as high as possible.[38]

The use of oxygen in medicine become common around 1917.[43][44] It is on the World Health Organization's List of Essential Medicines.[45] The cost of home oxygen is about US$150 a month in Brazil and US$400 a month in the United States.[40] Home oxygen can be provided either by oxygen tanks or an oxygen concentrator.[38] Oxygen is believed to be the most common treatment given in hospitals in the developed world.[46][38]

### Anaesthetic gases[edit | edit source]

A vaporizer holds a liquid anesthetic and converts it to gas for inhalation (in this case sevoflurane)

An anaesthetic machine.

Bottles of sevoflurane, isoflurane, enflurane, and desflurane, the common fluorinated ether anaesthetics used in clinical practice. These agents are colour-coded for safety purposes. Note the special fitting for desflurane, which boils at room temperature.

The most common approach to general anaesthesia is through the use of inhaled general anesthetics. Each has its own potency which is correlated to its solubility in oil. This relationship exists because the drugs bind directly to cavities in proteins of the central nervous system,[clarification needed] although several theories of general anaesthetic action have been described. Inhalational anesthetics are thought to exact their effects on different parts of the central nervous system. For instance, the immobilizing effect of inhaled anesthetics results from an effect on the spinal cord whereas sedation, hypnosis and amnesia involve sites in the brain.[47]: 515

An inhalational anaesthetic is a chemical compound possessing general anaesthetic properties that can be delivered via inhalation. Agents of significant contemporary clinical interest include volatile anaesthetic agents such as isoflurane, sevoflurane and desflurane, and anaesthetic gases such as nitrous oxide and xenon.

#### Administration[edit | edit source]

Anaesthetic gases are administered by anaesthetists (a term which includes anaesthesiologists, nurse anaesthetists, and anaesthesiologist assistants) through an anaesthesia mask, laryngeal mask airway or tracheal tube connected to an anaesthetic vaporiser and an anaesthetic delivery system. The anaesthetic machine (UK English) or anesthesia machine (US English) or Boyle's machine is used to support the administration of anaesthesia. The most common type of anaesthetic machine in use in the developed world is the continuous-flow anaesthetic machine, which is designed to provide an accurate and continuous supply of medical gases (such as oxygen and nitrous oxide), mixed with an accurate concentration of anaesthetic vapour (such as isoflurane), and deliver this to the patient at a safe pressure and flow. Modern machines incorporate a ventilator, suction unit, and patient monitoring devices.[clarification needed][citation needed]

## See also[edit | edit source]

* Mechanical ventilation - Method to mechanically assist or replace spontaneous breathing
* Diving air compressor - Machine used to compress breathing air for use by underwater divers
* Diving cylinder - Cylinder to supply breathing gas for divers
* Booster pump - Machine to increase pressure of a fluid
* Industrial gas - Gaseous materials produced for use in industry

## References[edit | edit source]

1. ↑ 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 1.10 1.11 1.12 1.13 1.14 1.15 1.16 1.17 1.18 1.19 1.20 1.21 1.22 1.23 1.24 1.25 1.26 1.27 1.28 1.29 1.30 1.31 1.32 1.33 1.34 Brubakk, A. O.; T. S. Neuman (2003). Bennett and Elliott's physiology and medicine of diving (5th Rev ed.). United States: Saunders Ltd. p. 800\. ISBN 978-0-7020-2571-6.
2. ↑ 2.00 2.01 2.02 2.03 2.04 2.05 2.06 2.07 2.08 2.09 2.10 2.11 2.12 2.13 2.14 2.15 2.16 2.17 2.18 2.19 2.20 2.21 US Navy Diving Manual, 6th revision. United States: US Naval Sea Systems Command. 2006. Archived from the original on 2008-05-02. Retrieved 2008-08-29.
3. ↑ 3.00 3.01 3.02 3.03 3.04 3.05 3.06 3.07 3.08 3.09 3.10 3.11 3.12 3.13 3.14 3.15 3.16 3.17 3.18 3.19 3.20 3.21 3.22 3.23 3.24 3.25 3.26 3.27 3.28 3.29 3.30 3.31 3.32 Tech Diver. "Exotic Gases". Archived from the original on 2008-09-14. Retrieved 2008-08-29.
4. ↑ 4.0 4.1 4.2 4.3 4.4 4.5 4.6 4.7 Harlow, V. (2002). Oxygen Hacker's Companion. Airspeed Press. ISBN 978-0-9678873-2-6.
5. ↑ 5.0 5.1 5.2 5.3 5.4 5.5 5.6 =Millar, I.L.; Mouldey, P.G. (2008). "Compressed breathing air – the potential for evil from within". Diving and Hyperbaric Medicine. South Pacific Underwater Medicine Society. 38 (2): 145–51. PMID 22692708. Archived from the original on 2010-12-25. Retrieved 2009-02-28.`{{cite journal}}`: CS1 maint: extra punctuation (link)
6. ↑ 6.0 6.1 6.2 6.3 6.4 6.5 6.6 6.7 Acott, Chris (1999). "Oxygen toxicity: A brief history of oxygen in diving". South Pacific Underwater Medicine Society Journal. 29 (3). ISSN 0813-1988. OCLC 16986801. Archived from the original on 2010-12-25. Retrieved 2008-08-29.
7. ↑ Butler, F.K. (2004). "Closed-circuit oxygen diving in the U.S. Navy". Undersea Hyperb Med. 31 (1): 3–20. PMID 15233156. Archived from the original on 2010-05-13. Retrieved 2008-08-29.
8. ↑ 8.0 8.1 8.2 Richardson, Drew; Menduno, Michael; Shreeves, Karl, eds. (1996). "Proceedings of Rebreather Forum 2.0". Diving Science and Technology Workshop.: 286. Archived from the original on 2010-12-25. Retrieved 2008-08-29.
9. ↑ 9.0 9.1 9.2 9.3 9.4 9.5 9.6 Lang, M.A. (2001). DAN Nitrox Workshop Proceedings. Durham, NC: Divers Alert Network. p. 197\. Archived from the original on 2008-10-24. Retrieved 2008-08-29.
10. ↑ 10.0 10.1 10.2 10.3 10.4 10.5 Hamilton Jr, Robert W.; Schreiner, Hans R., eds. (1975). Development of Decompression Procedures for Depths in Excess of 400 feet. Vol. 9th Undersea and Hyperbaric Medical Society Workshop. Bethesda, MD: Undersea and Hyperbaric Medical Society. p. 272\. Archived from the original on 2010-12-25. Retrieved 2008-08-29.
11. ↑ Bowen, Curt. "Heliair: Poor man's mix" (PDF). DeepTech. Archived (PDF) from the original on 2016-05-13. Retrieved 2010-01-13.
12. ↑ 12.0 12.1 12.2 Fife, William P. (1979). "The use of Non-Explosive mixtures of hydrogen and oxygen for diving". Texas A&M University Sea Grant. TAMU-SG-79-201.
13. ↑ Rostain, J. C.; Gardette-Chauffour, M. C.; Lemaire, C.; Naquet, R. (1988). "Effects of a H2-He-O2 mixture on the HPNS up to 450 msw". Undersea Biomed. Res. 15 (4): 257–70. ISSN 0093-5387. OCLC 2068005. PMID 3212843. Archived from the original on 2008-12-06. Retrieved 2008-08-29.
14. ↑ Brauer, R.W., ed. (1985). "Hydrogen as a Diving Gas". 33rd Undersea and Hyperbaric Medical Society Workshop. Undersea and Hyperbaric Medical Society (UHMS Publication Number 69(WS–HYD)3–1–87): 336 pages. Archived from the original on 2011-04-10. Retrieved 2008-09-16.
15. ↑ 15.0 15.1 Hamilton, Robert W. Jr; Powell, Michael R.; Kenyon, David J.; Freitag, M. (1974). "Neon Decompression". Tarrytown Labs Ltd NY. CRL-T-797. Archived from the original on 2010-12-25. Retrieved 2008-08-29.
16. ↑ Staff (2007). Marking and Colour Coding of Gas Cylinders, Quads and Banks for Diving Applications IMCA D043 (PDF). London, UK: International Marine Contractors Association. Retrieved 1 February 2016.[permanent dead link]
17. ↑ Universal Industrial Gases, Inc. (2003). "Non-Cryogenic Air Separation Processes". Archived from the original on 2018-10-03. Retrieved 2008-08-29.
18. ↑ Fowler, B.; Ackles, K.N.; Porlier, G. (1985). "Effects of inert gas narcosis on behavior--a critical review". Undersea Biomed. Res. 12 (4): 369–402. ISSN 0093-5387. OCLC 2068005. PMID 4082343. Archived from the original on 2010-12-25. Retrieved 2008-08-29.
19. ↑ Logan, J.A. (1961). "An evaluation of the equivalent air depth theory". United States Navy Experimental Diving Unit Technical Report. NEDU-RR-01-61. Archived from the original on 2010-12-25. Retrieved 2008-08-29.
20. ↑ Berghage, T.E.; McCraken, T.M. (December 1979). "Equivalent air depth: fact or fiction". Undersea Biomed Res. 6 (4): 379–84. PMID 538866. Archived from the original on 2010-12-25. Retrieved 2008-08-29.
21. ↑ Hunger Jr, W. L.; Bennett, P. B. (1974). "The causes, mechanisms and prevention of the high pressure nervous syndrome". Undersea Biomed. Res. 1 (1): 1–28. ISSN 0093-5387. OCLC 2068005. PMID 4619860. Archived from the original on 2010-12-25. Retrieved 2008-08-29.
22. ↑ "Thermal Conductivity of common Materials and Gases". Engineering Toolbox. Archived from the original on 2017-07-25. Retrieved 2017-02-18.
23. ↑ 23.0 23.1 Ackerman, M.J.; Maitland, G (December 1975). "Calculation of the relative speed of sound in a gas mixture". Undersea Biomed Res. 2 (4): 305–10. PMID 1226588. Archived from the original on 2011-01-27. Retrieved 2008-08-29.
24. ↑ U.S. Navy Diving Manual (7 ed.). Washington, DC: U.S. Government. 1 December 2016. pp. 2–15.
25. ↑ 25.0 25.1 25.2 25.3 25.4 NAVSEA (2005). "Cleaning and gas analysis for diving applications handbook". NAVSEA Technical Manual. NAVAL SEA SYSTEMS COMMAND. SS521-AK-HBK-010. Archived from the original on 2010-12-25. Retrieved 2008-08-29.
26. ↑ Rahn, H.; Rokitka, M.A. (March 1976). "Narcotic potency of N2, A, and N2O evaluated by the physical performance of mouse colonies at simulated depths". Undersea Biomed Res. 3 (1): 25–34. PMID 1273982. Archived from the original on 2010-12-25. Retrieved 2008-08-28.
27. ↑ D'Aoust, B.G.; Stayton, L.; Smith, L.S. (September 1980). "Separation of basic parameters of decompression using fingerling salmon". Undersea Biomed Res. 7 (3): 199–209. PMID 7423658. Archived from the original on 2010-12-25. Retrieved 2008-08-29.
28. ↑ Pilmanis, A.A.; Balldin, U.I.; Webb, J.T.; Krause, K.M. (December 2003). "Staged decompression to 3.5 psi using argon-oxygen and 100% oxygen breathing mixtures". Aviat Space Environ Med. 74 (12): 1243–50. PMID 14692466. Archived from the original on 2011-06-06. Retrieved 2008-08-29.
29. ↑ "Argon (Ar)". Encyclopædia Britannica. Archived from the original on 2 May 2015. Retrieved 14 January 2014.
30. ↑ Lambertsen, C. J. (1971). "Carbon Dioxide Tolerance and Toxicity". Environmental Biomedical Stress Data Center, Institute for Environmental Medicine, University of Pennsylvania Medical Center. Philadelphia, PA. IFEM Report No. 2-71. Archived from the original on 2011-07-24. Retrieved 2008-08-29.
31. ↑ Glatte, H. A. Jr; Motsay, G. J.; Welch, B. E. (1967). "Carbon Dioxide Tolerance Studies". Brooks AFB, TX School of Aerospace Medicine Technical Report. SAM-TR-67-77. Archived from the original on 2008-05-09. Retrieved 2008-08-29.
32. ↑ Rosales, K.R.; Shoffstall, M.S.; Stoltzfus, J.M. (2007). "Guide for Oxygen Compatibility Assessments on Oxygen Components and Systems". NASA, Johnson Space Center Technical Report. NASA/TM-2007-213740. Archived from the original on 2011-05-15. Retrieved 2008-08-29.
33. ↑ =Kizer, K.W.; Golden, JA (November 1987). "Lipoid pneumonitis in a commercial abalone diver". Undersea Biomedical Research. 14 (6): 545–52. PMID 3686744. Archived from the original on 2013-05-25. Retrieved 2013-04-02.`{{cite journal}}`: CS1 maint: extra punctuation (link)
34. ↑ 34.0 34.1 34.2 34.3 "Diver's breathing gas standard and the frequency of examination and tests: Diving Information Sheet No 9 (rev2)" (PDF). Health and Safety Executive. January 2018. Archived (PDF) from the original on 6 October 2018. Retrieved 6 October 2018.
35. ↑ Joint Technical Committee SF-017, Occupational Diving (21 December 2015). AS/NZS 2299.1:2015 Australian/New Zealand Standard Occupational diving operations, Part 1: Standard operational practice.`{{cite book}}`: CS1 maint: uses authors parameter (link)
36. ↑ Peate, Ian; Wild, Karen; Nair, Muralitharan (2014). Nursing Practice: Knowledge and Care. John Wiley & Sons. p. 572\. ISBN 9781118481363. Archived from the original on 2017-01-18. Retrieved 2020-05-27.
37. ↑ 37.0 37.1 Martin, Lawrence (1997). Scuba Diving Explained: Questions and Answers on Physiology and Medical Aspects of Scuba Diving. Lawrence Martin. p. H-1. ISBN 9780941332569. Archived from the original on 2017-01-18. Retrieved 2020-05-27.
38. ↑ 38.0 38.1 38.2 38.3 38.4 British national formulary : BNF 69 (69 ed.). British Medical Association. 2015. pp. 217–218, 302. ISBN 9780857111562.
39. ↑ 39.0 39.1 World Health Organization (2009). Stuart MC, Kouimtzi M, Hill SR (eds.). WHO Model Formulary 2008. World Health Organization. p. 20\. hdl:10665/44053. ISBN 9789241547659.
40. ↑ 40.0 40.1 Jamison, Dean T.; Breman, Joel G.; Measham, Anthony R.; Alleyne, George; Claeson, Mariam; Evans, David B.; Jha, Prabhat; Mills, Anne; Musgrove, Philip (2006). Disease Control Priorities in Developing Countries. World Bank Publications. p. 689\. ISBN 9780821361801. Archived from the original on 2017-05-10. Retrieved 2020-05-27.
41. ↑ Macintosh, Michael; Moore, Tracey (1999). Caring for the Seriously Ill Patient 2E (2 ed.). CRC Press. p. 57\. ISBN 9780340705827. Archived from the original on 2017-01-18. Retrieved 2020-05-27.
42. ↑ Dart, Richard C. (2004). Medical Toxicology. Lippincott Williams & Wilkins. pp. 217–219. ISBN 9780781728454. Archived from the original on 2017-01-18. Retrieved 2020-05-27.
43. ↑ Agasti, T. K. (2010). Textbook of Anesthesia for Postgraduates. JP Medical Ltd. p. 398\. ISBN 9789380704944. Archived from the original on 2017-05-10. Retrieved 2020-05-27.
44. ↑ Rushman, Geoffrey B.; Davies, N. J. H.; Atkinson, Richard Stuart (1996). A Short History of Anaesthesia: The First 150 Years. Butterworth-Heinemann. p. 39\. ISBN 9780750630665. Archived from the original on 2021-09-23. Retrieved 2020-05-27.
45. ↑ World Health Organization (2019). World Health Organization model list of essential medicines: 21st list 2019. Geneva: World Health Organization. hdl:10665/325771. WHO/MVP/EMP/IAU/2019.06. License: CC BY-NC-SA 3.0 IGO.
46. ↑ Wyatt, Jonathan P.; Illingworth, Robin N.; Graham, Colin A.; Hogg, Kerstin; Robertson, Colin; Clancy, Michael (2012). Oxford Handbook of Emergency Medicine. Oxford, England: Oxford University Press. p. 95\. ISBN 9780191016059. Archived from the original on 2017-01-18. Retrieved 2020-05-27.
47. ↑ Miller, Ronald D. (2010). Erikson, Lars I.; Fleisher, Lee A.; Wiener-Kronish, Jeanine P.; Young, William L (eds.). Miller's Anesthesia Seventh edition. Churchill Livingstone Elsevier. ISBN 978-0-443-06959-8.

## External links[edit | edit source]

*   * altitude.org. "Altitude oxygen calculator". altitude.org. Retrieved 2008-08-29.[permanent dead link]
* Westfalen (2004). "Fact sheet on Divox" (PDF) (in Dutch). Westfalen. Archived from the original (PDF) on 2011-07-24. Retrieved 2008-08-29.`{{cite web}}`: CS1 maint: unrecognized language (link)
* Taylor, L. "A Brief History Of Mixed Gas Diving". Archived from the original on 2008-05-29. Retrieved 2008-08-29.
* OSHA. "Commercial Diving Regulations (Standards - 29 CFR) - Mixed-gas diving. - 1910.426". U.S. Department of Labor, Occupational Safety & Health Administration. Archived from the original on 2008-09-20. Retrieved 2008-08-29.

* v
* t
* e

Underwater diving

* Diving modes
* Atmospheric pressure diving
* Freediving
* Saturation diving
* Scuba diving
* Snorkeling
* Surface oriented diving
* Surface-supplied diving
* Unmanned diving

Diving equipment

* Cleaning and disinfection of personal diving equipment
* Human factors in diving equipment design

| Basic equipment|

* Diving mask
* Snorkel
* Swimfin

|

Breathing gas|

* Bailout gas
* Bottom gas
* Breathing air
* Decompression gas
* Emergency gas supply
* Heliox
* Nitrox
* Oxygen
* Travel gas
* Trimix

Buoyancy and
trim equipment|

* Buoyancy compensator
* Power inflator
* Dump valve
* Diving weighting system
* Ankle weights
* Integrated weights
* Trim weights
* Weight belt

Decompression
equipment|

* Decompression buoy
* Decompression cylinder
* Decompression trapeze
* Dive computer
* Diving shot
* Jersey upline
* Jonline

Diving suit|

* Atmospheric diving suit
* Dry suit
* Sladen suit
* Standard diving suit
* Rash vest
* Wetsuit
* Dive skins
* Hot-water suit

Helmets
and masks|

* Anti-fog
* Diving helmet
* Free-flow helmet
* Lightweight demand helmet
* Orinasal mask
* Reclaim helmet
* Shallow water helmet
* Standard diving helmet
* Diving mask
* Band mask
* Full-face mask
* Half mask

Instrumentation|

* Bottom timer
* Depth gauge
* Dive computer
* Dive timer
* Diving watch
* Helium release valve
* Pneumofathometer
* Submersible pressure gauge

Mobility
equipment|

* Diving bell
* Closed bell
* Wet bell
* Diving stage
* Swimfin
* Monofin
* PowerSwim
* Towboard

| Diver
propulsion
vehicle|

* Advanced SEAL Delivery System
* Cosmos CE2F series
* Dry Combat Submersible
* Human torpedo
* Motorised Submersible Canoe
* Necker Nymph
* R-2 Mala-class swimmer delivery vehicle
* SEAL Delivery Vehicle
* Shallow Water Combat Submersible
* Siluro San Bartolomeo
* Wet Nellie
* Wet sub

|

Safety
equipment|

* Alternative air source
* Octopus regulator
* Pony bottle
* Bolt snap
* Buddy line
* Dive light
* Diver's cutting tool
* Diver's knife
* Diver's telephone
* Through-water communications
* Diving bell
* Diving safety harness
* Emergency gas supply
* Bailout block
* Bailout bottle
* Lifeline
* Screw gate carabiner
* Emergency locator beacon
* Rescue tether
* Safety helmet
* Shark-proof cage
* Snoopy loop
* Navigation equipment
* Distance line
* Diving compass
* Dive reel
* Line marker
* Surface marker buoy
* Silt screw

Underwater
breathing
apparatus|

* Atmospheric diving suit
* Diving cylinder
* Burst disc
* Diving cylinder valve
* Diving helmet
* Reclaim helmet
* Diving regulator
* Mechanism of diving regulators
* Regulator malfunction
* Regulator freeze
* Single-hose regulator
* Twin-hose regulator
* Full face diving mask

| Open-circuit
scuba|

* Scuba set
* Bailout bottle
* Decompression cylinder
* Independent doubles
* Manifolded twin set
* Scuba manifold
* Pony bottle
* Scuba configuration
* Sidemount
* Sling cylinder

|

Diving
rebreathers|

* Carbon dioxide scrubber
* Carleton CDBA
* CDLSE
* Cryogenic rebreather
* CUMA
* DSEA
* Dolphin
* Electro-galvanic oxygen sensor
* FROGS
* Halcyon PVR-BASC
* Halcyon RB80
* IDA71
* Interspiro DCSC
* KISS
* LAR-5
* LAR-6
* LAR-V
* LARU
* Porpoise
* Ray
* Siebe Gorman CDBA
* Siva
* Viper

Surface-supplied
diving equipment|

* Air line
* Diver's umbilical
* Diving air compressor
* Gas panel
* Hookah
* Scuba replacement
* Sea Trek
* Snuba
* Standard diving dress

Escape set|

* Davis Submerged Escape Apparatus
* Momsen lung
* Steinke hood
* Submarine Escape Immersion Equipment

Diving
equipment
manufacturers|

* AP Diving
* Apeks
* Aqua Lung America
* Aqua Lung/La Spirotechnique
* Beuchat
* René Cavalero
* Cis-Lunar
* Cressi-Sub
* Dacor
* DESCO
* Dive Xtras
* Divex
* Diving Unlimited International
* Drägerwerk
* Fenzy
* Maurice Fernez
* Technisub
* Oscar Gugen
* Heinke
* HeinrichsWeikamp
* Johnson Outdoors
* Mares
* Morse Diving
* Nemrod
* Oceanic Worldwide
* Porpoise
* Sub Sea Systems
* Shearwater Research
* Siebe Gorman
* Submarine Products
* Suunto

Diving support equipment

| Access equipment|

* Boarding stirrup
* Diver lift
* Diving bell
* Diving ladder
* Diving platform (scuba)
* Diving stage
* Downline
* Jackstay
* Launch and recovery system
* Messenger line
* Moon pool

|

Breathing gas
handling|

* Air filtration
* Activated carbon
* Hopcalite
* Molecular sieve
* Silica gel
* Booster pump
* Carbon dioxide scrubber
* Cascade filling system
* Diver's pump
* Diving air compressor
* Diving air filter
* Water separator
* High pressure breathing air compressor
* Low pressure breathing air compressor
* Gas blending
* Gas blending for scuba diving
* Gas panel
* Gas reclaim system
* Gas storage bank
* Gas storage quad
* Gas storage tube
* Helium analyzer
* Nitrox production
* Membrane gas separation
* Pressure swing adsorption
* Oxygen analyser
* Oxygen compatibility

Decompression
equipment|

* Built-in breathing system
* Decompression tables
* Diving bell
* Bell cursor
* Closed bell
* Clump weight
* Launch and recovery system
* Wet bell
* Diving chamber
* Diving stage
* Recreational Dive Planner
* Saturation system

Platforms|

* Dive boat
* Canoe and kayak diving
* Combat Rubber Raiding Craft
* Liveaboard
* Subskimmer
* Diving support vessel
* HMS Challenger (K07)

| Underwater
habitat|

* Aquarius Reef Base
* Continental Shelf Station Two
* Helgoland Habitat
* Jules' Undersea Lodge
* Scott Carpenter Space Analog Station
* SEALAB
* Tektite habitat

|

Remotely operated
underwater vehicles|

* 8A4-class ROUV
* ABISMO
* Atlantis ROV Team
* CURV
* Deep Drone
* Épaulard
* Global Explorer ROV
* Goldfish-class ROUV
* Kaikō ROV
* Kaşif ROUV
* Long-Term Mine Reconnaissance System
* Mini Rover ROV
* OpenROV
* ROV KIEL 6000
* ROV PHOCA
* Scorpio ROV
* Sea Dragon-class ROV
* Seabed tractor
* Seafox drone
* Seahorse ROUV
* SeaPerch
* SJT-class ROUV
* T1200 Trenching Unit
* VideoRay UROVs

Safety equipment|

* Diver down flag
* Diving shot
* Hyperbaric lifeboat
* Hyperbaric stretcher
* Jackstay
* Jonline
* Reserve gas supply

General|

* Diving spread
* Air spread
* Saturation spread
* Hot water system
* Sonar
* Underwater acoustic positioning system
* Underwater acoustic communication

Freediving

| Activities|

* Aquathlon
* Apnoea finswimming
* Freediving
* Haenyeo
* Pearl hunting
* Ama
* Snorkeling
* Spearfishing
* Underwater football
* Underwater hockey
* Underwater ice hockey
* Underwater rugby
* Underwater target shooting

|

Competitions|

* Nordic Deep
* Vertical Blue
* Disciplines
* Constant weight (CWT)
* Constant weight without fins (CNF)
* Dynamic apnea (DYN)
* Dynamic apnea without fins (DNF)
* Free immersion (FIM)
* No-limits apnea (NLT)
* Static apnea (STA)
* Skandalopetra diving
* Variable weight apnea (VWT)
* Variable weight apnea without fins

Equipment|

* Diving mask
* Diving suit
* Hawaiian sling
* Polespear
* Snorkel (swimming)
* Speargun
* Swimfins
* Monofin
* Water polo cap

Freedivers|

* Deborah Andollo
* Peppo Biscarini
* Sara Campbell
* Derya Can Göçen
* Goran Čolak
* Carlos Coste
* Robert Croft
* Mandy-Rae Cruickshank
* Yasemin Dalkılıç
* Leonardo D'Imporzano
* Flavia Eberhard
* Şahika Ercümen
* Emma Farrell
* Francisco Ferreras
* Pierre Frolla
* Flavia Eberhard
* Mehgan Heaney-Grier
* Elisabeth Kristoffersen
* Loïc Leferme
* Enzo Maiorca
* Jacques Mayol
* Audrey Mestre
* Karol Meyer
* Stéphane Mifsud
* Alexey Molchanov
* Natalia Molchanova
* Dave Mullins
* Patrick Musimu
* Guillaume Néry
* Herbert Nitsch
* Umberto Pelizzari
* Annelie Pompe
* Michal Risian
* Stig Severinsen
* Tom Sietas
* Aharon Solomons
* Martin Štěpánek
* Walter Steyn
* Tanya Streeter
* William Trubridge
* Devrim Cenk Ulusoy
* Danai Varveri
* Alessia Zecchini
* Nataliia Zharkova

Hazards|

* Barotrauma
* Drowning
* Freediving blackout
* Deep-water blackout
* Shallow-water blackout
* Hypercapnia
* Hypothermia

Historical|

* Ama
* Octopus wrestling
* Swimming at the 1900 Summer Olympics – Men's underwater swimming

Organisations|

* AIDA International
* Scuba Schools International
* Australian Underwater Federation
* British Freediving Association
* Confédération Mondiale des Activités Subaquatiques
* Fédération Française d'Études et de Sports Sous-Marins
* Performance Freediving International

Professional diving

| Occupations|

* Ama
* Commercial diver
* Commercial offshore diver
* Hazmat diver
* Divemaster
* Diving instructor
* Diving safety officer
* Diving superintendent
* Diving supervisor
* Haenyeo
* Media diver
* Police diver
* Public safety diver
* Scientific diver
* Underwater archaeologist

| Military diving|

* Army engineer diver
* Clearance diver
* Frogman
* List of military diving units
* Royal Navy ships diver
* Special Boat Service
* United States military divers
* U.S. Navy diver
* U.S.Navy master diver
* United States Navy SEALs
* Underwater Demolition Team

|

Underwater work|

* Commercial offshore diving
* Dive leader
* Diver training
* Recreational diver training
* Hyperbaric welding
* Media diving
* Nondestructive testing
* Pearl hunting
* Police diving
* Potable water diving
* Public safety diving
* Scientific diving
* Ships husbandry
* Sponge diving
* Submarine pipeline
* Underwater archaeology
* Archaeology of shipwrecks
* Underwater construction
* Offshore construction
* Underwater demolition
* Underwater photography
* Underwater search and recovery
* Underwater videography

| Salvage diving|

* SS Egypt
* Kronan
* La Belle
* SS Laurentic
* RMS Lusitania
* Mars
* Mary Rose
* USS Monitor
* HMS Royal George
* Vasa

|

Diving contractors|

* COMEX
* Helix Energy Solutions Group

Tools & equipment|

* Abrasive waterjet
* Airlift
* Baited remote underwater video
* In-water surface cleaning
* Brush cart
* Cavitation cleaning
* Pressure washing
* Pigging
* Lifting bag
* Remotely operated underwater vehicle
* Thermal lance
* Tremie
* Water jetting

Underwater
weapons|

* Limpet mine
* Speargun
* Hawaiian sling
* Polespear

| Underwater
firearm|

* Gyrojet
* Mk 1 Underwater Defense Gun
* Powerhead
* Underwater pistols
* Heckler & Koch P11
* SPP-1 underwater pistol
* Underwater revolvers
* AAI underwater revolver
* Underwater rifles
* ADS amphibious rifle
* APS underwater rifle
* ASM-DT amphibious rifle

|

Recreational diving

| Specialties|

* Altitude diving
* Cave diving
* Deep diving
* Ice diving
* Muck diving
* Open-water diving
* Rebreather diving
* Sidemount diving
* Solo diving
* Technical diving
* Underwater photography
* Wreck diving

|

Diver
organisations|

* British Sub-Aqua Club (BSAC)
* Cave Divers Association of Australia (CDAA)
* Cave Diving Group (CDG)
* Comhairle Fo-Thuinn (CFT)
* Confédération Mondiale des Activités Subaquatiques (CMAS)
* Federación Española de Actividades Subacuáticas (FEDAS)
* Fédération Française d'Études et de Sports Sous-Marins (FFESSM)
* International Association for Handicapped Divers (IAHD)
* National Association for Cave Diving (NACD)
* Woodville Karst Plain Project (WKPP)

Diving tourism
industry|

* Dive center
* Environmental impact of recreational diving
* Scuba diving tourism
* Shark tourism
* Sinking ships for wreck diving sites

Diving events
and festivals|

* Diversnight
* Underwater Bike Race

Recreational
dive sites|

| Reef diving
regions|

* Aliwal Shoal Marine Protected Area
* Arrecifes de Cozumel National Park
* Edmonds Underwater Park
* Great Barrier Reef
* iSimangaliso Marine Protected Area
* Poor Knights Islands
* Table Mountain National Park Marine Protected Area

|

Reef dive
sites|

* Artificial reef
* Gibraltar Artificial Reef
* Shark River Reef
* Osborne Reef
* Fanadir
* Gamul Kebir
* Palancar Reef
* Underwater artworks
* Cancún Underwater Museum
* Christ of the Abyss
* Molinere Underwater Sculpture Park

Wreck diving
regions|

* Chuuk Lagoon
* Edmonds Underwater Park
* Finger Lakes Underwater Preserve Association
* Maritime Heritage Trail – Battle of Saipan
* Michigan Underwater Preserves
* Robben Island Marine Protected Area
* Table Mountain National Park Marine Protected Area
* Tulagi
* Tulamben
* Whitefish Point Underwater Preserve
* Wreck Alley, San Diego

Wreck dive
sites|

* HMS A1
* HMS A3
* USS Aaron Ward
* Abessinia
* Aeolian Sky
* Albert C. Field
* Andrea Doria
* Antilla
* Antilles
* Aquila
* USS Arkansas
* Bianca C.
* SS Binnendijk
* HMS Boadicea
* Booya
* HMSAS Bloemfontein
* Breda
* HMAS Brisbane
* HMHS Britannic
* Bungsberg
* HMAS Canberra
* Carl D. Bradley
* Carnatic
* SMS Dresden
* Dunraven
* Eastfield
* HMT Elk
* Ellengowan
* RMS Empress of Ireland
* HMS Falmouth
* Fifi
* SS Francisco Morazan
* Fujikawa Maru
* Fumizuki
* SATS General Botha
* USNS General Hoyt S. Vandenberg
* HMS Ghurka
* Glen Strathallan
* SAS Good Hope
* Gothenburg
* Herzogin Cecilie
* Hilma Hooker
* Hispania
* HMS Hood
* HMAS Hobart
* Igara
* James Eagan Layne
* Captain Keith Tibbetts
* King Cruiser
* SMS Kronprinz
* Kyarra
* HMS Laforey
* USAT Liberty
* Louis Sheid
* USS LST-507
* SMS Markgraf
* Mikhail Lermontov
* HMS M2
* Maine
* Maloja
* HMS Maori
* Marguerite
* SS Mauna Loa
* USAT Meigs
* Mendi
* USCGC Mohawk
* Mohegan
* RMS Moldavia
* HMS Montagu
* MV RMS Mulheim
* Nagato
* Oceana
* USS Oriskany
* Oslofjord
* P29
* P31
* Pedernales
* Persier
* HMAS Perth
* SAS Pietermaritzburg
* Piłsudski
* Pool Fisher
* HMS Port Napier
* Preußen
* President Coolidge
* PS Queen Victoria
* Radaas
* Rainbow Warrior
* RMS Rhone
* Rondo
* Rosehill
* Rotorua
* Royal Adelaide
* Royal Charter
* Rozi
* HMS Safari
* Salem Express
* USS Saratoga
* USS Scuffle
* HMS Scylla
* HMS Sidon
* USS Spiegel Grove
* Stanegarth
* Stanwood
* Stella
* HMAS Swan
* USS Tarpon
* Thesis
* Thistlegorm
* Toa Maru
* Torrey Canyon
* SAS Transvaal
* U-40
* U-352
* U-1195
* Um El Faroud
* Varvassi
* Walter L M Russ
* Washingtonian (1913)
* HMNZS Wellington
* USS Yancey
* Yongala
* Zenobia
* Zealandia
* Zingara

Cave diving
sites|

* Blauhöhle
* Chinhoyi Caves
* Devil's Throat at Punta Sur
* Engelbrecht Cave
* Fossil Cave
* Jordbrugrotta
* Piccaninnie Ponds
* Pluragrotta
* Pollatoomary
* Sistema Ox Bel Ha
* Sistema Sac Actun
* Sistema Dos Ojos
* Sistema Nohoch Nah Chich

Freshwater
dives|

* Dutch Springs
* Ewens Ponds
* Little Blue Lake

Training sites|

* Capernwray Dive Centre
* Deepspot
* National Diving and Activity Centre
* Stoney Cove

Open ocean
diving|

* Blue-water diving
* Black-water diving

Diving safety

* Human factors in diving equipment design
* Human factors in diving safety
* Life-support system
* Safety-critical system
* Scuba diving fatalities

| Diving
hazards|

* List of diving hazards and precautions
* Environmental
* Current
* Delta-P
* Entanglement hazard
* Overhead
* Silt out
* Wave action
* Equipment
* Freeflow
* Use of breathing equipment in an underwater environment
* Failure of diving equipment other than breathing apparatus
* Single point of failure
* Physiological
* Cold shock response
* Decompression
* Nitrogen narcosis
* Oxygen toxicity
* Seasickness
* Uncontrolled decompression
* Diver behaviour and competence
* Lack of competence
* Overconfidence effect
* Panic
* Task loading
* Trait anxiety
* Willful violation

| Consequences|

* Barotrauma
* Decompression sickness
* Drowning
* Hypothermia
* Hypoxia
* Hypercapnia
* Hyperthermia

|

Diving
procedures|

* Ascending and descending
* Emergency ascent
* Boat diving
* Canoe and kayak diving
* Buddy diving
* buddy check
* Decompression
* Decompression practice
* Pyle stop
* Ratio decompression
* Dive briefing
* Dive log
* Dive planning
* Scuba gas planning
* Diver communications
* Diving hand signals
* Diving line signals
* Diver voice communications
* Diver rescue
* Diver training
* Doing It Right
* Drift diving
* Gas blending for scuba diving
* Night diving
* Solo diving
* Water safety

Risk
management|

* Checklist
* Hazard identification and risk assessment
* Hazard analysis
* Job safety analysis
* Risk assessment
* Risk control
* Hierarchy of hazard controls
* Incident pit
* Lockout–tagout
* Permit To Work
* Redundancy
* Safety data sheet
* Situation awareness

| Diving team|

* Bellman
* Chamber operator
* Diver medical technician
* Diver's attendant
* Diving supervisor
* Diving systems technician
* Gas man
* Life support technician
* Stand-by diver

|

Equipment
safety|

* Breathing gas quality
* Testing and inspection of diving cylinders
* Hydrostatic test
* Sustained load cracking
* Diving regulator
* Breathing performance of regulators

Occupational
safety and
health|

* Approaches to safety
* Job safety analysis
* Risk assessment
* Toolbox talk
* Housekeeping
* Association of Diving Contractors International
* Code of practice
* Contingency plan
* Diving regulations
* Emergency procedure
* Emergency response plan
* Evacuation plan
* Hazardous Materials Identification System
* Hierarchy of hazard controls
* Administrative controls
* Engineering controls
* Hazard elimination
* Hazard substitution
* Personal protective equipment
* International Marine Contractors Association
* Occupational hazard
* Biological hazard
* Chemical hazard
* Physical hazard
* Psychosocial hazard
* Occupational hygiene
* Exposure assessment
* Occupational exposure limit
* Workplace health surveillance
* Safety culture
* Code of practice
* Diving safety officer
* Diving superintendent
* Health and safety representative
* Operations manual
* Safety meeting
* Standard operating procedure

Diving medicine

| Diving
disorders|

* List of signs and symptoms of diving disorders
* Cramp
* Motion sickness
* Surfer's ear

| Pressure
related|

* Alternobaric vertigo
* Barostriction
* Barotrauma
* Air embolism
* Aerosinusitis
* Barodontalgia
* Dental barotrauma
* Pulmonary barotrauma
* Compression arthralgia
* Decompression illness
* Dysbarism

| Oxygen|

* Freediving blackout
* Hyperoxia
* Hypoxia
* Oxygen toxicity

|

Inert gases|

* Avascular necrosis
* Decompression sickness
* Isobaric counterdiffusion
* Taravana
* Dysbaric osteonecrosis
* High-pressure nervous syndrome
* Hydrogen narcosis
* Nitrogen narcosis

Carbon dioxide|

* Hypercapnia
* Hypocapnia

Breathing gas
contaminants|

* Carbon monoxide poisoning

Immersion
related|

* Asphyxia
* Drowning
* Hypothermia
* Immersion diuresis
* Instinctive drowning response
* Laryngospasm
* Salt water aspiration syndrome
* Swimming-induced pulmonary edema

Treatment|

* Demand valve oxygen therapy
* First aid
* Hyperbaric medicine
* Hyperbaric treatment schedules
* In-water recompression
* Oxygen therapy
* Therapeutic recompression

Personnel|

* Diving Medical Examiner
* Diving Medical Practitioner
* Diving Medical Technician
* Hyperbaric nursing

Screening|

* Atrial septal defect
* Effects of drugs on fitness to dive
* Fitness to dive
* Psychological fitness to dive

Research|

| Researchers in
diving physiology
and medicine|

* Arthur J. Bachrach
* Albert R. Behnke
* Paul Bert
* George F. Bond
* Robert Boyle
* Albert A. Bühlmann
* John R. Clarke
* Guybon Chesney Castell Damant
* Kenneth William Donald
* William Paul Fife
* John Scott Haldane
* Robert William Hamilton Jr.
* Leonard Erskine Hill
* Brian Andrew Hills
* Felix Hoppe-Seyler
* Christian J. Lambertsen
* Simon Mitchell
* Charles Momsen
* John Rawlins R.N.
* Charles Wesley Shilling
* Edward D. Thalmann
* Jacques Triger

|

Diving medical
research
organisations|

* Aerospace Medical Association
* Divers Alert Network (DAN)
* Diving Diseases Research Centre (DDRC)
* Diving Medical Advisory Council (DMAC)
* European Diving Technology Committee (EDTC)
* European Underwater and Baromedical Society (EUBS)
* National Board of Diving and Hyperbaric Medical Technology
* Naval Submarine Medical Research Laboratory
* Royal Australian Navy School of Underwater Medicine
* Rubicon Foundation
* South Pacific Underwater Medicine Society (SPUMS)
* Southern African Underwater and Hyperbaric Medical Association (SAUHMA)
* Undersea and Hyperbaric Medical Society (UHMS)
* United States Navy Experimental Diving Unit (NEDU)

Law

* Civil liability in recreational diving
* Diving regulations
* Duty of care
* List of legislation regulating underwater diving
* Investigation of diving accidents
* UNESCO Convention on the Protection of the Underwater Cultural Heritage

History of underwater diving

* History of decompression research and development
* History of scuba diving
* List of researchers in underwater diving
* Timeline of diving technology
* Underwater diving in popular culture

| Archeological
sites|

* SS Commodore
* USS Monitor
* Queen Anne's Revenge
* Whydah Gally

|

Underwater art
and artists|

* The Diver
* Jason deCaires Taylor

Engineers
and inventors|

* William Beebe
* Georges Beuchat
* John R. Clarke
* Jacques Cousteau
* Charles Anthony Deane
* John Deane
* Ted Eldred
* Henry Fleuss
* Émile Gagnan
* Joseph-Martin Cabirol
* Christian J. Lambertsen
* Yves Le Prieur
* John Lethbridge
* Ernest William Moir
* Joseph Salim Peress
* Auguste Piccard
* Willard Franklyn Searle
* Augustus Siebe
* Jacques Triger

Equipment|

* Aqua-Lung
* RV Calypso
* SP-350 Denise
* Nikonos
* Porpoise regulator
* Standard diving dress
* Vintage scuba

Military and
covert operations|

* Raid on Alexandria (1941)
* Sinking of the Rainbow Warrior

Scientific projects|

* 1992 cageless shark-diving expedition
* Mission 31

Incidents|

| Dive boat incidents|

* Sinking of MV Conception
* Fire on MV Red Sea Aggressor

|

Diver rescues|

* Alpazat cave rescue
* Tham Luang cave rescue

Early diving|

* John Day (carpenter)
* Charles Spalding
* Ebenezer Watson

Freediving fatalities|

* Loïc Leferme
* Audrey Mestre
* Nicholas Mevoli
* Natalia Molchanova

Offshore
diving incidents|

* Byford Dolphin diving bell accident
* Drill Master diving accident
* Star Canopus diving accident
* Stena Seaspread diving accident
* Venture One diving accident
* Waage Drill II diving accident
* Wildrake diving accident

Professional
diving fatalities|

* Roger Baldwin
* John Bennett
* Victor F. Guiel Jr.
* Craig M. Hoffman
* Peter Henry Michael Holmes
* Johnson Sea Link accident
* Edwin Clayton Link
* Gerard Anthony Prangley
* Pier Skipness
* Robert John Smyth
* Albert D. Stover
* Richard A. Walker
* Lothar Michael Ward
* Joachim Wendler
* Bradley Westell
* Arne Zetterström

Scuba diving
fatalities|

* Ricardo Armbruster
* Allan Bridge
* David Bright
* Berry L. Cannon
* Cotton Coulson
* Cláudio Coutinho
* E. Yale Dawson
* Deon Dreyer
* Milan Dufek
* Sheck Exley
* Maurice Fargues
* Fernando Garfella Palmer
* Guy Garman
* Steve Irwin
* Jim Jones
* Henry Way Kendall
* Artur Kozłowski
* Chris and Chrissy Rouse
* Kirsty MacColl
* Agnes Milowka
* François de Roubaix
* Dave Shaw
* Wesley C. Skiles
* Dewey Smith
* Rob Stewart
* Esbjörn Svensson
* Josef Velek

Publications

| Manuals|

* NOAA Diving Manual
* U.S. Navy Diving Manual
* Basic Cave Diving: A Blueprint for Survival
* Underwater Handbook
* Bennett and Elliott's physiology and medicine of diving
* Encyclopedia of Recreational Diving
* The new science of skin and scuba diving
* Professional Diver's Handbook
* Basic Scuba

|

Standards and
Codes of Practice|

* Code of Practice for Scientific Diving (UNESCO)
* DIN 7876
* IMCA Code of Practice for Offshore Diving
* ISO 24801 Recreational diving services — Requirements for the training of recreational scuba divers

General non-fiction|

* The Darkness Beckons
* Goldfinder
* The Last Dive
* Shadow Divers
* The Silent World: A Story of Undersea Discovery and Adventure

Research|

* List of Divers Alert Network publications

Dive guides|

Training and registration

| Diver
training|

* Competence and assessment
* Competency-based learning
* Refresher training
* Skill assessment
* Diver training standard
* Diving instructor
* Diving school
* Occupational diver training
* Commercial diver training
* Military diver training
* Public safety diver training
* Scientific diver training
* Recreational diver training
* Introductory diving
* Teaching method
* Muscle memory
* Overlearning
* Stress exposure training

| Skills|

* Combat sidestroke
* Diver navigation
* Diver trim
* Ear clearing
* Frenzel maneuver
* Valsalva maneuver
* Finning techniques
* Scuba skills
* Buddy breathing
* Low impact diving
* Diamond Reef System
* Surface-supplied diving skills
* Underwater searches

|

Recreational
scuba
certification
levels|

| Core diving skills|

* Advanced Open Water Diver
* Autonomous diver
* CMAS* scuba diver
* CMAS** scuba diver
* Introductory diving
* Low Impact Diver
* Master Scuba Diver
* Open Water Diver
* Supervised diver

|

Leadership skills|

* Dive leader
* Divemaster
* Diving instructor
* Master Instructor

Specialist skills|

* Rescue Diver
* Solo diver

Diver training
certification
and registration
organisations|

* European Underwater Federation (EUF)
* International Diving Regulators and Certifiers Forum (IDRCF)
* International Diving Schools Association (IDSA)
* International Marine Contractors Association (IMCA)
* List of diver certification organizations
* National Oceanic and Atmospheric Administration (NOAA)
* Nautical Archaeology Society
* Universal Referral Program
* World Recreational Scuba Training Council (WRSTC)

| Commercial diver
certification
authorities|

* Australian Diver Accreditation Scheme (ADAS)
* Commercial diver registration in South Africa
* Divers Institute of Technology
* Health and Safety Executive (HSE)
* Department of Employment and Labour

|

Commercial diving
schools|

* Divers Academy International
* Norwegian diver school

Free-diving
certification
agencies|

* AIDA International (AIDA)
* Confédération Mondiale des Activités Subaquatiques (CMAS)
* Performance Freediving International (PI)
* Scuba Schools International (SSI)

Recreational scuba
certification
agencies|

* American Canadian Underwater Certifications (ACUC)
* American Nitrox Divers International (ANDI)
* Association nationale des moniteurs de plongée (ANMP)
* British Sub-Aqua Club (BSAC)
* Comhairle Fo-Thuinn (CFT)
* Confédération Mondiale des Activités Subaquatiques (CMAS)
* Federación Española de Actividades Subacuáticas (FEDAS)
* Fédération Française d'Études et de Sports Sous-Marins (FFESSM)
* Federazione Italiana Attività Subacquee (FIAS)
* Global Underwater Explorers (GUE)
* International Association for Handicapped Divers (IAHD)
* International Association of Nitrox and Technical Divers (IANTD)
* International Diving Educators Association (IDEA)
* Israeli Diving Federation (TIDF)
* National Academy of Scuba Educators (NASE)
* National Association of Underwater Instructors (NAUI)
* Nederlandse Onderwatersport Bond (NOB)
* Professional Association of Diving Instructors (PADI)
* Professional Diving Instructors Corporation (PDIC)
* Sub-Aqua Association (SAA)
* Scuba Diving International (SDI)
* Scuba Educators International (SEI)
* Scottish Sub Aqua Club (ScotSAC)
* Scuba Schools International (SSI)
* Türkiye Sualtı Sporları Federasyonu (TSSF)
* United Diving Instructors (UDI)
* YMCA SCUBA Program

Scientific diver
certification
authorities|

* American Academy of Underwater Sciences (AAUS)
* CMAS Scientific Committee

Technical
certification
agencies|

* American Nitrox Divers International (ANDI)
* British Sub-Aqua Club (BSAC)
* Confédération Mondiale des Activités Subaquatiques (CMAS)
* Diving Science and Technology (DSAT)
* Federazione Italiana Attività Subacquee (FIAS)
* International Association of Nitrox and Technical Divers (IANTD)
* Professional Association of Diving Instructors (PADI)
* Professional Diving Instructors Corporation (PDIC)
* Trimix Scuba Association (TSA)
* Technical Extended Range (TXR)

| Cave
diving|

* Cave Divers Association of Australia (CDAA)
* Cave Diving Group (CDG)
* Global Underwater Explorers (GUE)
* National Association for Cave Diving (NACD)
* National Speleological Society#Cave Diving Group (CDG)
* National Association of Underwater Instructors (NAUI)
* Technical Diving International (TDI)

|

Underwater sports

| Surface snorkeling|

* Finswimming

|

Snorkeling/breath-hold|

* Spearfishing
* Underwater football
* Underwater hockey
* Australia
* Turkey
* Underwater rugby
* Colombia
* United States
* Underwater target shooting

Breath-hold|

* Aquathlon
* Apnoea finswimming
* Freediving
* Underwater ice hockey

Open Circuit Scuba|

* Immersion finswimming
* Sport diving
* Underwater cycling
* Underwater orienteering
* Underwater photography

Rebreather|

* Underwater photography

Sports governing
organisations
and federations|

* International
* AIDA International
* Confédération Mondiale des Activités Subaquatiques)
* National
* AIDA Hellas
* Australian Underwater Federation
* British Freediving Association
* British Octopush Association
* British Underwater Sports Association
* Comhairle Fo-Thuinn
* Federación Española de Actividades Subacuáticas
* Fédération Française d'Études et de Sports Sous-Marins
* South African Underwater Sports Federation
* Türkiye Sualtı Sporları Federasyonu
* Underwater Society of America)

Competitions|

* 14th CMAS Underwater Photography World Championship

Underwater divers

| Pioneers
of diving|

* Eduard Admetlla i Lázaro
* Aquanaut
* James F. Cahill
* Jacques Cousteau
* Billy Deans
* Dottie Frazier
* Hans Hass
* Dick Rutkowski
* Teseo Tesei
* Arne Zetterström

|

Underwater
scientists
archaeologists and
environmentalists|

* Michael Arbuthnot
* Robert Ballard
* George Bass
* Mensun Bound
* Louis Boutan
* Hugh Bradner
* Cathy Church
* Eugenie Clark
* James P. Delgado
* Sylvia Earle
* John Christopher Fine
* George R. Fischer
* Anders Franzén
* Honor Frost
* Fernando Garfella Palmer
* David Gibbins
* Graham Jessop
* Swietenia Puspa Lestari
* Pilar Luna
* Robert F. Marx
* Anna Marguerite McCann
* Innes McCartney
* Charles T. Meide
* David Moore
* Mark M. Newell
* Lyuba Ognenova-Marinova
* John Peter Oleson
* Mendel L. Peterson
* Richard Pyle
* William R. Royal
* Margaret Rule
* Gunter Schöbel
* Stephanie Schwabe
* Myriam Seco
* E. Lee Spence
* Robert Sténuit
* Peter Throckmorton

Scuba record
holders|

* Pascal Bernabé
* Jim Bowden
* Mark Ellyatt
* Sheck Exley
* Nuno Gomes
* Claudia Serpieri
* Krzysztof Starnawski

Underwater
filmmakers
and presenters|

* Samir Alhafith
* David Attenborough
* Ramón Bravo
* Jean-Michel Cousteau
* Richie Kohler
* Ivan Tors
* Andrew Wight

Underwater
photographers|

* Tamara Benitez
* Georges Beuchat
* Adrian Biddle
* Jonathan Bird
* Eric Cheng
* Neville Coleman
* Jacques Cousteau
* John D. Craig
* Ben Cropp
* Bernard Delemotte
* David Doubilet
* John Christopher Fine
* Dermot FitzGerald
* Rodney Fox
* Ric Frazier
* Stephen Frink
* Peter Gimbel
* Monty Halls
* Hans Hass
* Henry Way Kendall
* Rudie Kuiter
* Joseph B. MacInnis
* Luis Marden
* Agnes Milowka
* Noel Monkman
* Steve Parish
* Zale Parry
* Pierre Petit
* Leni Riefenstahl
* Peter Scoones
* Brian Skerry
* Wesley C. Skiles
* E. Lee Spence
* Philippe Tailliez
* Ron Taylor
* Valerie Taylor
* Albert Tillman
* John Veltri
* Stan Waterman
* Michele Westmorland
* John Ernest Williamson
* J. Lamar Worzel

Underwater
explorers|

* Caves
* Graham Balcombe
* Sheck Exley
* Martyn Farr
* Jochen Hasenmayer
* Jill Heinerth
* Jarrod Jablonski
* William Hogarth Main
* Tom Mount
* Jack Sheppard
* Bill Stone
* Reefs
*   * Wrecks
* Leigh Bishop
* John Chatterton
* Clive Cussler
* Bill Nagle
* Aristotelis Zervoudis

Aquanauts|

* Andrew Abercromby
* Joseph M. Acaba
* Clayton Anderson
* Richard R. Arnold
* Serena Auñón-Chancellor
* Michael Barratt (astronaut)
* Robert L. Behnken
* Randolph Bresnik
* Timothy J. Broderick
* Justin Brown
* Berry L. Cannon
* Scott Carpenter
* Gregory Chamitoff
* Steve Chappell
* Catherine Coleman
* Robin Cook
* Craig B. Cooper
* Fabien Cousteau
* Philippe Cousteau
* Timothy Creamer
* Jonathan Dory
* Pedro Duque
* Sylvia Earle
* Jeanette Epps
* Sheck Exley
* Albert Falco
* Andrew J. Feustel
* Michael Fincke
* Satoshi Furukawa
* Ronald J. Garan Jr.
* Michael L. Gernhardt
* Christopher E. Gerty
* David Gruber
* Chris Hadfield
* Jeremy Hansen
* José M. Hernández
* John Herrington
* Paul Hill
* Akihiko Hoshide
* Mark Hulsbeck
* Emma Hwang
* Norishige Kanai
* Les Kaufman
* Scott Kelly
* Karen Kohanowich
* Timothy Kopra
* Dominic Landucci
* Jon Lindbergh
* Kjell N. Lindgren
* Michael López-Alegría
* Joseph B. MacInnis
* Sandra Magnus
* Thomas Marshburn
* Matthias Maurer
* K. Megan McArthur
* Craig McKinley
* Jessica Meir
* Simone Melchior
* Dorothy Metcalf-Lindenburger
* Andreas Mogensen
* Karen Nyberg
* John D. Olivas
* Takuya Onishi
* Luca Parmitano
* Nicholas Patrick
* Tim Peake
* Thomas Pesquet
* Marc Reagan
* Garrett Reisman
* Kathleen Rubins
* Dick Rutkowski
* Tara Ruttley
* David Saint-Jacques
* Josef Schmid
* Robert Sheats
* Dewey Smith
* Steve Squyres
* Heidemarie Stefanyshyn-Piper
* Robert Sténuit
* Hervé Stevenin
* Nicole Stott
* James Talacek
* Daniel M. Tani
* Robert Thirsk
* Bill Todd
* Mark T. Vande Hei
* Koichi Wakata
* Rex J. Walheim
* Shannon Walker
* John Morgan Wells
* Joachim Wendler
* Douglas H. Wheelock
* Peggy Whitson
* Dafydd Williams
* Jeffrey Williams
* Sunita Williams
* Gregory R. Wiseman
* Kimiya Yui

Writers and journalists|

* Michael C. Barnette
* Victor Berge
* Philippe Diolé
* Gary Gentile
* Bret Gilliam
* Bob Halstead
* Trevor Jackson
* Steve Lewis
* John Mattera

Rescuers|

* Craig Challen
* Richard Harris
* Rick Stanton
* John Volanthen

Frogmen|

* Lionel Crabb

Commercial salvors|

* Keith Jessop

Science of underwater diving

| Diving
physics|

* Breathing performance of regulators
* Buoyancy
* Archimedes' principle
* Neutral buoyancy
* Concentration
* Diffusion
* Molecular diffusion
* Force
* Oxygen fraction
* Permeation
* Psychrometric constant
* Solubility
* Henry's law
* Saturation
* Solution
* Supersaturation
* Surface tension
* Hydrophobe
* Surfactant
* Temperature
* Torricellian chamber
* Underwater acoustics
* Modulated ultrasound
* Underwater vision
* Snell's law
* Underwater computer vision
* Weight
* Apparent weight

| Gas laws|

* Amontons's law
* Boyle's law
* Charles's law
* Combined gas law
* Dalton's law
* Gay-Lussac's law
* Ideal gas law

|

Pressure|

* Absolute pressure
* Ambient pressure
* Atmospheric pressure
* Gauge pressure
* Hydrostatic pressure
* Metre sea water
* Partial pressure

Diving
physiology|

* Artificial gills
* Cold shock response
* Diving reflex
* Equivalent narcotic depth
* Lipid
* Maximum operating depth
* Metabolism
* Physiological response to water immersion
* Tissue
* Underwater vision

| Circulatory
system|

* Blood shift
* Patent foramen ovale
* Perfusion
* Pulmonary circulation
* Systemic circulation

|

Decompression
theory|

* Decompression models:
* Bühlmann decompression algorithm
* Haldane's decompression model
* Reduced gradient bubble model
* Thalmann algorithm
* Thermodynamic model of decompression
* Varying Permeability Model
* Equivalent air depth
* Equivalent narcotic depth
* Oxygen window in diving decompression
* Physiology of decompression

Respiration|

* Blood–air barrier
* Breathing
* CO₂ retention
* Dead space
* Gas exchange
* Hypocapnia
* Respiratory exchange ratio
* Respiratory quotient
* Respiratory system
* Work of breathing

Diving
environment|

| Classification|

* List of diving environments by type
* Altitude diving
* Benign water diving
* Confined water diving
* Deep diving
* Inland diving
* Inshore diving
* Muck diving
* Night diving
* Open-water diving
* Black-water diving
* Blue-water diving
* Penetration diving
* Cave diving
* Ice diving
* Wreck diving
* Recreational dive sites
* Underwater environment

|

Impact|

* Environmental impact of recreational diving
* Low impact diving

Environmental
factors|

* Algal bloom
* Currents:
* Current
* Longshore drift
* Ocean current
* Rip current
* Tidal race
* Undertow
* Upwelling
* Ekman transport
* Halocline
* Reef
* Coral reef
* Stratification
* Thermocline
* Tides
* Turbidity
* Wind wave
* Breaking wave
* Surf
* Surge
* Wave shoaling

Other

* Bathysphere
* Defense against swimmer incursions
* Diver detection sonar
* Offshore survey
* Underwater domain awareness

| Awards and events|

* Hans Hass Award
* International Scuba Diving Hall of Fame
* London Diving Chamber Dive Lectures
* NOGI Awards

|

Deep-submergence
vehicle|

* Aluminaut
* DSV Alvin
* American submarine NR-1
* Bathyscaphe
* Archimède
* FNRS-2
* FNRS-3
* FNRS-4
* Harmony class bathyscaphe
* Sea Pole-class bathyscaphe
* Trieste II
* Deepsea Challenger
* Ictineu 3
* JAGO
* Jiaolong
* Konsul-class submersible
* DSV Limiting Factor
* Russian submarine Losharik
* Mir
* Nautile
* Pisces-class deep submergence vehicle
* DSV Sea Cliff
* DSV Shinkai
* DSV Shinkai 2000
* DSV Shinkai 6500
* DSV Turtle
* DSV-5 Nemo

| Deep-submergence
rescue vehicle|

* LR5
* LR7
* MSM-1
* Mystic-class deep-submergence rescue vehicle
* DSRV-1 Mystic
* DSRV-2 Avalon
* NATO Submarine Rescue System
* Priz-class deep-submergence rescue vehicle
* Russian deep submergence rescue vehicle AS-28
* Russian submarine AS-34
* ASRV Remora
* SRV-300
* Submarine Rescue Diving Recompression System
* Type 7103 DSRV
* URF (Swedish Navy)

|

Special
interest
groups|

* Artificial Reef Society of British Columbia
* CMAS Europe
* Coral Reef Alliance
* Diving Equipment and Marketing Association
* Divers Alert Network
* Green Fins
* Historical Diving Society
* Karst Underwater Research
* Nautical Archaeology Program
* Nautical Archaeology Society
* Naval Air Command Sub Aqua Club
* Project AWARE
* Reef Check
* Reef Life Survey
* Rubicon Foundation
* Save Ontario Shipwrecks
* SeaKeys
* Sea Research Society
* Society for Underwater Historical Research
* Society for Underwater Technology
* Underwater Archaeology Branch, Naval History & Heritage Command

Submarine escape
and rescue|

* Escape trunk
* International Submarine Escape and Rescue Liaison Office
* McCann Rescue Chamber
* Submarine Escape and Rescue system (Royal Swedish Navy)
* Submarine escape training facility
* Submarine Escape Training Facility (Australia)
* Submarine rescue ship

Neutral buoyancy
facilities for
Astronaut training|

* Neutral Buoyancy Laboratory
* Neutral buoyancy pool
* Neutral buoyancy simulation as a training aid
* Neutral Buoyancy Simulator
* Space Systems Laboratory
* Yuri Gagarin Cosmonaut Training Center

Other|

* Nautilus Productions

* Category
* Commons
*   * Glossary
* Indexes: dive sites
* divers
* diving
*   * Outline
* Portal

*[v]: View this template
*[t]: Discuss this template
*[e]: Edit this template