Air is the most common and only natural breathing gas. Temperature and layers The temperature of the Earth's atmosphere varies with altitude the mathematical relationship between temperature and altitude varies among five Other artificial gases, either pure gases or mixtures of gases, are used in breathing equipment and enclosed habitats such as SCUBA equipment, surface supplied diving equipment, recompression chambers, submarines, space suits, spacecraft and anaesthetic machines. A scuba set is an independent breathing set that provides a scuba diver with the Breathing gas necessary to breathe underwater during Scuba diving. Surface supplied diving (also known as Hooka diving refers to divers using equipment supplied with Breathing gas using an umbilical cord A recompression chamber is a Pressure vessel used to treat divers suffering from certain Diving disorders such as Decompression sickness. A submarine is a Watercraft that can operate independently below water as distinct from a Submersible that has only limited underwater capability A space suit is a complex system of Garments equipment and environmental systems designed to keep a person alive and comfortable in the harsh environment of outer space A spacecraft is a Vehicle or machine designed for Spaceflight. The anaesthetic machine (or anesthesia machine in America is used by Anaesthesiologists to support the administration of Anaesthesia.
Most breathing gases are a mixture of oxygen and one or more inert gases. All breathing gases are alternatives to air and have been developed to improve on the performance of air by reducing the risk of decompression sickness, reducing the duration of decompression stops, reducing nitrogen narcosis or allowing safer deep diving. Decompression sickness (DCS, the diver’s disease, the bends, caisson disease is the name given to a variety of symptoms suffered by a person A decompression stop is a period of time a diver must spend at a constant depth in shallow water at the end of a dive to safely eliminate absorbed Inert gases from Nitrogen narcosis or inert gas narcosis is a reversible alteration in Consciousness in scuba divers at depth The meaning of the term deep diving is a form of Technical diving.
A safe breathing gas has three essential features:
- it must contain sufficient oxygen to support the life, consciousness and work rate of the breather. Oxygen (from the Greek roots ὀξύς (oxys (acid literally "sharp" from the taste of acids and -γενής (-genēs (producer literally begetteris the
- it must not contain harmful gases. Carbon monoxide and carbon dioxide are common poisons in breathing gases. There are many others.
- it must not become toxic when being breathed at high pressure such as when underwater. Pressure (symbol 'p' is the force per unit Area applied to an object in a direction perpendicular to the surface Underwater is a term describing the realm below the surface of Water where the water exists in a natural feature (called a body of water) such as an Ocean Oxygen and nitrogen are examples of gases that become toxic under pressure. Oxygen (from the Greek roots ὀξύς (oxys (acid literally "sharp" from the taste of acids and -γενής (-genēs (producer literally begetteris the Nitrogen (ˈnaɪtɹəʤɪn is a Chemical element that has the symbol N and Atomic number 7 and Atomic weight 14 Toxicity is the degree to which a substance is able to damage an exposed organism
The techniques used to fill diving cylinders with gases other than air are called gas blending. A diving cylinder, scuba tank or diving tank is used to store and transport high Pressure Breathing gas as a component of SCUBA (Self-Contained Gas blending or gas mixing is the filling of Diving cylinders with non- Air Breathing gases such as Nitrox, Trimix and
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Common diving breathing gases
Common diving breathing gases are:
- Air is a mixture of 21% oxygen, 78% nitrogen, and approximately 1% other trace gases; to simplify calculations this last 1% is usually treated as if it were nitrogen. Oxygen (from the Greek roots ὀξύς (oxys (acid literally "sharp" from the taste of acids and -γενής (-genēs (producer literally begetteris the Nitrogen (ˈnaɪtɹəʤɪn is a Chemical element that has the symbol N and Atomic number 7 and Atomic weight 14 Being cheap and simple to use, it is the most common diving gas. 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.
- Pure oxygen is mainly used to speed the shallow decompression stops at the end of a technical dive. Technical diving (sometimes referred to a Tec diving) is a form of Scuba diving that exceeds the scope of Recreational diving (although the vast majority It was much used in frogmen's rebreathers. A frogman is someone who is trained to dive or swim in a military capacity often in combat A rebreather is a type of Breathing set that provides a Breathing gas containing Oxygen and recycled exhaled gas
- Nitrox is a mixture of oxygen and air, and generally refers to mixtures which are more than 21% oxygen. Nitrox refers to any gas mixture composed (excluding trace gases of nitrogen and oxygen this includes normal Air which is approximately 78% Nitrogen It is mainly used instead of air to accelerate decompression or to decrease the risk of decompression sickness. Decompression sickness (DCS, the diver’s disease, the bends, caisson disease is the name given to a variety of symptoms suffered by a person
- 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. Helium ( He) is a colorless odorless tasteless non-toxic Inert Monatomic Chemical Technical diving (sometimes referred to a Tec diving) is a form of Scuba diving that exceeds the scope of Recreational diving (although the vast majority Hardhat diving redirects here Often "hardhat diving" is used to specifically mean diving in the old-type Standard diving dress.
- 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. See Heliox (cryogenic equipment for another use of the word Heliox Heliox is a Breathing gas composed of a mixture of
- Heliair is a form of trimix that is easily blended from helium and air without using pure oxygen. Heliair is a Breathing gas consisting of mixture of Oxygen, Nitrogen and Helium and is often used during the deep phase of dives carried out It always has a 21:79 ratio of oxygen to nitrogen; the balance of the mix is helium.
- Hydreliox is a mixture of oxygen, helium, and hydrogen and is used for dives below 130 metres in commercial diving. Hydreliox is an exotic Breathing gas mixture of Helium, Oxygen and a small amount of Hydrogen. Hydrogen (ˈhaɪdrədʒən is the Chemical element with Atomic number 1
- Neox (also called neonox) is a mixture of oxygen and neon sometimes employed for in deep commercial diving. Air is the most common and only natural breathing gas. Other artificial gases either pure gases or mixtures of gases are used in breathing equipment and enclosed habitats such Neon (ˈniːɒn is the Chemical element that has the symbol Ne and Atomic number 10 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. For more information on this and some of the other gases above, see the article on exotic diving gases in the external link provided at the end of this article.
Individual component gases
Oxygen
Oxygen (O2) must be present in every breathing gas. Oxygen (from the Greek roots ὀξύς (oxys (acid literally "sharp" from the taste of acids and -γενής (-genēs (producer literally begetteris the This is because it is essential to the human body's metabolic process, which sustains life. The human body is the entire physical and mental structure of a Human Organism. Metabolism is the set of Chemical reactions that occur in living Organisms in order to maintain 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. Tissue is a cellular organizational level intermediate between cells and a complete organism In Biology, an organ ( Latin: organum, "instrument tool" from Greek όργανον - organon "organ instrument
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. A diving cylinder, scuba tank or diving tank is used to store and transport high Pressure Breathing gas as a component of SCUBA (Self-Contained Gas blending or gas mixing is the filling of Diving cylinders with non- Air Breathing gases such as Nitrox, Trimix and
Oxygen has historically been obtained by fractional distillation of liquid air, but is increasingly obtained by non cryogenic technolgies such as pressure swing adsorption (PSA) and vacuum-pressure swing adsorption (VPSA) technolgies [1]. Fractional distillation is the separation of a mixture into its component parts or fractions such as in separating Chemical compounds by their Boiling point by heating Liquid Air was the brand name of an unusual Automobile produced by a joint American / English concern between 1899 and 1902 Pressure Swing Adsorption (PSA is a technology used to separate some gas species from a mixture of gases under pressure according to the species' molecular characteristics and affinity
Fraction of oxygen
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. In a mixture of Ideal gases each gas has a partial pressure which is the pressure which the gas would have if it alone occupied the volume Trimix, Heliox and Heliair create typical hypoxic mixes and are used in technical diving as deep breathing gases. See Heliox (cryogenic equipment for another use of the word Heliox Heliox is a Breathing gas composed of a mixture of Heliair is a Breathing gas consisting of mixture of Oxygen, Nitrogen and Helium and is often used during the deep phase of dives carried out Technical diving (sometimes referred to a Tec diving) is a form of Scuba diving that exceeds the scope of Recreational diving (although the vast majority
- normoxic mixes have the same proportion of oxygen as air, 21%. 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 a more oxygen than 21%. Enriched Air Nitrox (EANx) is a typical hyperoxic breathing gas. Nitrox refers to any gas mixture composed (excluding trace gases of nitrogen and oxygen this includes normal Air which is approximately 78% Nitrogen 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. Oxygen toxicity or oxygen toxicity syndrome (also known as the " Paul Bert effect" or the "Lorrain Smith effect" describes harmful effects caused A decompression stop is a period of time a diver must spend at a constant depth in shallow water at the end of a dive to safely eliminate absorbed Inert gases from
The fraction of the oxygen determines the deepest the mixture gas can safely be used to avoid oxygen toxicity. Oxygen toxicity or oxygen toxicity syndrome (also known as the " Paul Bert effect" or the "Lorrain Smith effect" describes harmful effects caused This depth is called the maximum operating depth. In Technical diving, the maximum operating depth (MOD of a Breathing gas is the depth at which the Partial pressure of Oxygen (ppO2
Partial pressure of oxygen
The concentration of oxygen in a gas mix depends on both the fraction and the pressure of the mixture. It is expressed by the partial pressure of oxygen (ppO2). In a mixture of Ideal gases each gas has a partial pressure which is the pressure which the gas would have if it alone occupied the volume
The partial pressure of any component gas in a mixture is calculated as:
- partial pressure = total absolute pressure x volume fraction of gas component
For the oxygen component:
- ppO2 = P x FO2
| where: | |
| ppO2 | = partial pressure of oxygen |
|---|---|
| P | = total pressure |
| FO2 | = volume fraction of oxygen |
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. Chronic Hypoxia is a pathological condition in which the body as a whole ( generalized hypoxia) or region of the body ( tissue hypoxia) is deprived of adequate When a hypoxic mix is breathed in shallow water it may not have a high enough ppO2 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 ppO2 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) but for dives of less than three hours is commonly considered to be 140 kPa (1. 4 bar), although the U. S. Navy has been known to authorize dives with a ppO2 of as much as 180 kPa (1. 8 bar). At high ppO2 or longer exposures, the diver risks oxygen toxicity including a seizure similar to an epileptic fit. An epileptic seizure is caused by excessive and/or hypersynchronous electrical Neuronal activity and is usually self-limiting Each breathing gas has a maximum operating depth that is determined by its oxygen content. In Technical diving, the maximum operating depth (MOD of a Breathing gas is the depth at which the Partial pressure of Oxygen (ppO2
Oxygen analysers measure the ppO2 in the gas mix. An electro-galvanic fuel cell is an electrical device used to measure the concentration of Oxygen gas in Scuba diving and Medical equipment
Divox
"Divox" is oxygen. Oxygen (from the Greek roots ὀξύς (oxys (acid literally "sharp" from the taste of acids and -γενής (-genēs (producer literally begetteris the 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 Netherlands ( Dutch:, ˈnedərlɑnt is the European part of the Kingdom of the Netherlands, which consists of the Netherlands the Netherlands Welding is a fabrication process that joins materials usually Metals or Thermoplastics by causing coalescence. A prescription (℞ is a health-care program implemented by a Physician or other medical practitioner in the form of instructions that govern the plan of care for an individual The diving industry "created" Divox and registered it as a trademark to circumvent the strict rules concerning medicinal oxygen thus making it easier for (recreational) scuba divers to obtain oxygen for blending their breathing gas. A trademark or trade mark, represented by the symbols ™ and ®, or mark is a distinctive sign or indicator used by an individual Scuba diving is swimming underwater, or taking part in another activity while using a Scuba set. 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 tanked differently. The chief difference between them is that the paper record-keeping trail is much more extensive for medical oxygen, in order to more easily identify the exact manufacturing trail of a "lot" of oxygen, in case problems are later found with its purity.
Nitrogen
Nitrogen (N2) is an diatomic gas and the main component of air, the cheapest and most common breathing gas used for diving. Nitrogen (ˈnaɪtɹəʤɪn is a Chemical element that has the symbol N and Atomic number 7 and Atomic weight 14 Temperature and layers The temperature of the Earth's atmosphere varies with altitude the mathematical relationship between temperature and altitude varies among five It causes nitrogen narcosis in the diver, so its use is limited to shallower dives. Nitrogen narcosis or inert gas narcosis is a reversible alteration in Consciousness in scuba divers at depth Nitrogen can cause decompression sickness. Decompression sickness (DCS, the diver’s disease, the bends, caisson disease is the name given to a variety of symptoms suffered by a person
Equivalent air depth is often used to help design a breathing gas mix by determining the maximum nitrogen content for a particular depth of dive. In Technical diving, the equivalent air depth (EAD is a way of expressing the narcotic effect of specific Breathing gas mixtures that contain Nitrogen Many divers find that the level of narcosis caused by a 30-metre (100-foot) dive, whilst breathing air, is a comfortable maximum. The partial pressure of nitrogen at this depth on air is 316 kPa (3. 16 bar) (Fraction of nitrogen x absolute pressure = 0. 79 x 400 kPa). So, what fraction of nitrogen would cause the same narcosis at 60 metres? The answer is 45% nitrogen. (316 kPa/700 kPa)
Nitrogen in a gas mix is almost always obtained by adding air to the mix.
Helium
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. Helium ( He) is a colorless odorless tasteless non-toxic Inert Monatomic Chemical Helium is equally able to cause decompression sickness. Decompression sickness (DCS, the diver’s disease, the bends, caisson disease is the name given to a variety of symptoms suffered by a person At high pressures, helium also causes High Pressure Nervous Syndrome, which is a CNS irritation syndrome which is in some ways opposite to narcosis. High pressure nervous syndrome ( HPNS) is a Neurological and Physiological diving disorder that results when a diver spends too much
Helium fills typically cost ten times more than an equivalent air fill.
Helium is not very suitable for dry suit inflation due to its poor thermal insulation properties — helium is a very good conductor of heat (compared to air which is a rather poor, making it more of an insulator). A dry suit or drysuit provides Thermal insulation or passive thermal protection to the wearer while immersed in water and is worn by divers, The term thermal insulation can refer to materials used to reduce the rate of Heat transfer, or the methods and processes used to reduce heat transfer Helium's low molecular weight (monatomic MW=4, compared with diatomic nitrogen MW=28) increases the pitch of the breather's voice, which may impede communication. This is because the speed of sound is faster in a lower molecular weight gas, which increases the resonance frequency of the vocal cords. 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. For other uses see Valve (disambiguation. For the electronic component see Thermionic valve. A mechanical seal is a device which helps join systems or mechanisms together by preventing leakage (e
Helium is found in significant amounts only in natural gas, from which it is extracted at low temperatures by fractional distillation. Natural gas is a Gaseous Fossil fuel consisting primarily of Methane but including significant quantities of Ethane, Propane,
Neon
Neon (Ne) is an inert gas sometimes used in deep commercial diving but is very expensive. Neon (ˈniːɒn is the Chemical element that has the symbol Ne and Atomic number 10 Hardhat diving redirects here Often "hardhat diving" is used to specifically mean diving in the old-type Standard diving dress. Like helium, it is less narcotic than nitrogen, but unlike helium, it does not distort the diver's voice.
Hydrogen
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). Hydrogen (ˈhaɪdrədʒən is the Chemical element with Atomic number 1 This limits use of hydrogen to deep dives and imposes complicated protocols to insure that oxygen is cleared from the lungs, the blood stream and the breathing equipment before breathing hydrogen starts. Like helium, it increases the pitch of the diver's voice. See Exotic diving gases. Tech Diver Web. Retrieved on Jan 9, 2005. Events 475 - Byzantine Emperor Zeno is forced to flee his capital at Constantinople. Year 2005 ( MMV) was a Common year starting on Saturday (link displays full calendar of the Gregorian calendar.
Unwelcome components of breathing gases
Many gases are not suitable for use in diving breathing gases. Here is an incomplete list of gases commonly present in a diving environment:
Argon
Argon (Ar) is an inert gas that is more narcotic than nitrogen, so is not suitable as a diving breathing gas. This article pertains to the chemical element For other uses see Argon (disambiguation. 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. A diving suit is a garment or device designed to protect a diver from the Underwater environment Argon is more expensive than air or oxygen, but considerably less expensive than helium.
Carbon dioxide
Carbon dioxide (CO2) is produced by the metabolism in the human body and causes carbon dioxide poisoning. Carbon dioxide ( Chemical formula:) is a Chemical compound composed of two Oxygen Atoms covalently bonded to a single Metabolism is the set of Chemical reactions that occur in living Organisms in order to maintain Life. The human body is the entire physical and mental structure of a Human Organism. Hypercapnia or hypercapnea (from the Greek hyper = "above" and kapnos = " Smoke " also known as hypercarbia is
Carbon monoxide
Carbon monoxide (CO) is produced by incomplete combustion. Carbon monoxide, with the chemical formula CO is a colorless odorless tasteless yet highly toxic Gas. Combustion or burning is a complex sequence of Exothermic chemical reactions between a Fuel and an Oxidant accompanied by the production of See carbon monoxide poisoning. Carbon monoxide poisoning occurs after the inhalation of Carbon monoxide gas Four common sources are:
- Internal combustion engine exhaust gas containing CO in the air being drawn into a diving air compressor. The internal combustion engine is an engine in which the Combustion of Fuel and an Oxidizer (typically air occurs in a confined space called a Exhaust gas is Flue gas which occurs as a result of the Combustion of fuels such as Natural gas, Gasoline /petrol Diesel, Fuel A Diving Air Compressor is a Gas compressor that can fill Diving cylinders with high- Pressure Air pure enough to be used as a Breathing gas CO in the intake air cannot be stopped by any filter. 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. A lubricant (sometimes referred to as a "Lube" is a substance (often a liquid introduced between two moving surfaces to reduce the Friction between them improving
- 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 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). Dust is a general name for minute Solid particles with Diameters less than 500 micrometers. Humus (Origin 1790–1800 Latin: earth ground) is the organic material in Soil lending it a dark brown or black colouration 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.
Hydrocarbons
Hydrocarbons (CxHy) are present in compressor lubricants and fuels. In Organic chemistry, a hydrocarbon is an Organic compound consisting entirely of Hydrogen and Carbon. Fuel is any material that is burned or altered in order to obtain energy They can enter diving cylinders as a result of contamination, leaks, or due to incomplete combustion near the air intake.
- They can act as a fuel in combustion increasing the risk of explosion, especially in high-oxygen gas mixtures. Fuel is any material that is burned or altered in order to obtain energy An explosion is a sudden increase in Volume and release of Energy in an extreme manner usually with the generation of high Temperatures and the release
- Inhaling oil mist can damage the lungs and ultimately cause the lungs to degenerate with severe emphysema. lung is the essential Respiration organ in air-breathing Animals including most Tetrapods a few Fish and a few Snails The most primitive Emphysema is a chronic obstructive Pulmonary disease ( COPD) formerly termed a chronic obstructive Lung disease (COLD
Moisture content
The process of compressing gas into a diving cylinder removes moisture from the gas. A Diving Air Compressor is a Gas compressor that can fill Diving cylinders with high- Pressure Air pure enough to be used as a Breathing gas This is good for corrosion prevention in the cylinder but means that the diver inhales very dry gas. Corrosion means the breaking down of essential properties in a material due to Chemical reactions with its surroundings 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. Dehydration ( hypohydration) is the removal of Water ( hydro in ancient Greek) from an object Decompression sickness (DCS, the diver’s disease, the bends, caisson disease is the name given to a variety of symptoms suffered by a person 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 to remove carbon dioxide puts moisture back into the breathing gas. A rebreather is a type of Breathing set that provides a Breathing gas containing Oxygen and recycled exhaled gas Soda lime is a mixture of Chemicals used in granular form in closed breathing environments such as General anaesthesia, Submarines Rebreathers In hot, tropical climates, open circuit diving can accelerate heat exhaustion because of dehydration. Hyperthermia, in its advanced state referred to as heat stroke or sunstroke, is an acute condition which occurs when the Body produces or absorbs more
Gas detection and measurement
Divers find it 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. An electro-galvanic fuel cell is an electrical device used to measure the concentration of Oxygen gas in Scuba diving and Medical equipment A carbon monoxide detector or CO detector is a device that detects the presence of the Toxic gas Carbon monoxide (CO a colorless and odorless compound Oxygen analysers are commonly found underwater in rebreathers. A rebreather is a type of Breathing set that provides a Breathing gas containing Oxygen and recycled exhaled gas 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. Gas blending or gas mixing is the filling of Diving cylinders with non- Air Breathing gases such as Nitrox, Trimix and Chemical and other types of gas detection methods are not often used in recreational diving.
External links
- Dutch language fact sheet on Divox
- An online model of the partial pressure of oxygen
- Link to an article with more info about some of the more exotic diving and breathing gases
- A Brief History Of Mixed Gas Diving, by Larry Taylor
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