Argox

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Argox is the informal name for a scuba diving breathing gas consisting of argon and oxygen. Occasionally the term argonox has been used to mean the same mix. The blend may consist of varying fractions of argon and oxygen, depending on its intended use. The mixture is made with the same gas blending techniques used to make nitrox, except that for argox, the argon is added to the initial pure oxygen partial-fill, instead of air.

Contents

Argox is essentially a theoretical diving gas, being rarely, if ever, used, and usually thought to have no practical applications where its benefits outweigh its drawbacks.[ citation needed ]

Possible uses

Human exploration of Mars

Argox, or half-argox/half-nitrox is a possible oxygen mixture for human exploration of Mars due to the relative abundance of argon in the Martian atmosphere. The Martian atmosphere is composed of approximately: 95% CO2, 1.9% argon, 1.9% nitrogen. While it is possible for humans to breathe pure oxygen, a pure oxygen atmosphere was implicated in the Apollo 1 fire. As such, Mars habitats may have a need for additional gases. One possibility is to take nitrogen and argon from the atmosphere of Mars; however, they are hard to separate from each other. As a result, a Mars habitat may use 40% argon, 40% nitrogen, and 20% oxygen. Another concept for breathing air is to use re-usable amine bead carbon dioxide scrubbers. While one carbon dioxide scrubber filters the astronauts' air, the other is vented to the Mars atmosphere. [1] [2]

Drysuit inflation

The helium in the breathing gas trimix, which is used to avoid nitrogen narcosis on deep dives, gives the gas a high thermal conductivity compared with air, making it inappropriate for drysuit inflation. Divers breathing trimix with drysuits usually inflate their drysuits with their decompression gas (usually nitrox or oxygen). A few carry yet another small cylinder, dedicated to drysuit inflation, containing argon. [3]

A second class of divers at intermediate depths of 30–45 metres (100–150 ft) which do not require trimix sometimes carry a pony bottle for emergencies, as is taught in many deep diving courses. Such second bottles are often 3 litres, and may be mounted in various ways from tank bracket to sling mounting. This second bottle can be used for argox, if a drysuit is used.[ original research? ]

Some[ who? ] argue that an argox blend with oxygen content similar to that of air could be used as a suit inflation gas in place of pure argon, as such a blend would only have a slightly higher thermal conductivity than pure argon, and unlike pure argon, would be breathable in an emergency. However, there are many problems with the use of suit inflation gas as an emergency breathing gas. Argon is a very narcotic gas, meaning that it could only be breathed at comparatively shallow depths above 20 metres (66 ft). However, in an emergency this is enough for adequate decompression time at typical decompression levels between 3 metres (10 ft) and 9 metres (30 ft), and would save a diver from a direct ascent. The small size of typical very small suit inflation cylinders mean that their contents would quickly be exhausted if breathed, but this is not so of larger ponies.

The thermal conductivity of argon is 68% of that of air or nitrox, hence its use in drysuit inflation. Using argox 20% would slightly degrade this to 74% of that of air.

Argon is far more narcotic (about 2.3 times more) than the cheaper and more readily available nitrogen at depth, so it loses out to nitrogen in all roles as a primary breathing gas. If the maximum operating depth for air owing to narcosis is taken to be 40 metres (130 ft), then for 20% argox (20% O2, 80% Ar) it would be 14.5 metres (48 ft). [lower-alpha 1]

Decompression gas

It has been theorised on the basis of the theory of isobaric counterdiffusion that argon, because of its higher molecular mass compared with nitrogen (40 vs. 28 u), may cause less inert gas on-loading, if used as a decompression gas, instead of nitrox. [4] The MOD of argox mixes containing more than about 47% oxygen are limited by oxygen MOD (assuming 1.5 atm ppO2) rather than by argon narcosis MOD. The maximal MOD for argox mixes occurs at 47% oxygen and 53% argon, and is about 73 fsw (22 m). This depth is the theoretical maximum which can be safely attained with any two-component argon/oxygen mix: a larger fraction of oxygen than about 50% will result in oxygen toxicity before this depth, and a larger fraction of argon than about 50% will result in argon narcosis before this depth.

However, as argox is more narcotic than nitrogen (causing it to be more dangerous if a decompression mix is accidentally breathed), and because argox is moderately more expensive than nitrox, and mostly because there has been little research done into the actual (vs. theoretical) physiological aspects of breathing argon during decompression, argox is not currently recommended by any professional agency for this purpose. [5]

Although there is little research relating to divers decompressing using argon mixes, there have been scientific studies of astronauts decompressing using argox. The provisional results of those studies indicated higher levels of decompression sickness when argox was used, rather than pure oxygen; however, using pure oxygen is not an option for decompression at the pressures for which argox would be used in diving, and no direct comparison of argon to nitrogen was done. [6] There is also a certain amount of anecdotal evidence within the diving community that informal experimentation with decompression on argon mixtures has resulted in a high incidence of decompression sickness, but no formal studies. [7]

See also

Notes

  1. ↑ Assuming oxygen, nitrogen and air all have roughly equal narcotic potential, and argon is 2.3 times that, the pressure (P) at which the narcotic potential of 20% argox is the same as air at 5 bar (i.e. 40 metres) can be found from P x (0.2 + (0.8 x 2.3)) = 5. That gives P=2.45 bar, which corresponds to 14.5 metres.

Related Research Articles

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

<span class="mw-page-title-main">Nitrogen narcosis</span> Reversible narcotic effects of respiratory nitrogen at elevated partial pressures

Narcosis while diving is a reversible alteration in consciousness that occurs while diving at depth. It is caused by the anesthetic effect of certain gases at high partial pressure. The Greek word νάρκωσις (narkōsis), "the act of making numb", is derived from νάρκη (narkē), "numbness, torpor", a term used by Homer and Hippocrates. Narcosis produces a state similar to drunkenness, or nitrous oxide inhalation. It can occur during shallow dives, but does not usually become noticeable at depths less than 30 metres (98 ft).

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

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

Heliox is a breathing gas mixture of helium (He) and oxygen (O2). It is used as a medical treatment for patients with difficulty breathing because this mixture generates less resistance than atmospheric air when passing through the airways of the lungs, and thus requires less effort by a patient to breathe in and out of the lungs. It is also used as a breathing gas diluent for deep ambient pressure diving as it is not narcotic at high pressure, and for its low work of breathing.

<span class="mw-page-title-main">Technical diving</span> Extended scope recreational diving

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

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

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

Diving physics, or the physics of underwater diving is the basic aspects of physics which describe the effects of the underwater environment on the underwater diver and their equipment, and the effects of blending, compressing, and storing breathing gas mixtures, and supplying them for use at ambient pressure. These effects are mostly consequences of immersion in water, the hydrostatic pressure of depth and the effects of pressure and temperature on breathing gases. An understanding of the physics behind is useful when considering the physiological effects of diving, breathing gas planning and management, diver buoyancy control and trim, and the hazards and risks of diving.

In underwater diving activities such as saturation diving, technical diving and nitrox diving, the maximum operating depth (MOD) of a breathing gas is the depth below which the partial pressure of oxygen (pO2) of the gas mix exceeds an acceptable limit. This limit is based on risk of central nervous system oxygen toxicity, and is somewhat arbitrary, and varies depending on the diver training agency or Code of Practice, the level of underwater exertion expected and the planned duration of the dive, but is normally in the range of 1.2 to 1.6 bar.

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

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

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

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

High-pressure nervous syndrome is a neurological and physiological diving disorder which can result when a diver descends below about 500 feet (150 m) using a breathing gas containing helium. The effects experienced, and the severity of those effects, depend on the rate of descent, the depth and the percentage of helium.

Hydreliox is an exotic breathing gas mixture of hydrogen, helium, and oxygen. For the Hydra VIII mission at 50 atmospheres of ambient pressure, the mixture used was 49% hydrogen, 50.2% helium, and 0.8% oxygen.

In physiology, isobaric counterdiffusion (ICD) is the diffusion of different gases into and out of tissues while under a constant ambient pressure, after a change of gas composition, and the physiological effects of this phenomenon. The term inert gas counterdiffusion is sometimes used as a synonym, but can also be applied to situations where the ambient pressure changes. It has relevance in mixed gas diving and anesthesiology.

Hydrox, a gas mixture of hydrogen and oxygen, is occasionally used as an experimental breathing gas in very deep diving. It allows divers to descend several hundred metres. Hydrox has been used experimentally in surface supplied, saturation, and scuba diving, both on open circuit and with closed circuit rebreathers.

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

<span class="mw-page-title-main">Helium analyzer</span> Instrument to measure the concentration of helium in a gas mixture

A Helium analyzer is an instrument used to identify the presence and concentration of helium in a mixture of gases. In Technical diving where breathing gas mixtures known as Trimix comprising oxygen, helium and nitrogen are used, it is necessary to know the fraction of helium in the mixture to reliably calculate decompression schedules for dives using that mixture.

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

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

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

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

Human physiology of underwater diving is the physiological influences of the underwater environment on the human diver, and adaptations to operating underwater, both during breath-hold dives and while breathing at ambient pressure from a suitable breathing gas supply. It, therefore, includes the range of physiological effects generally limited to human ambient pressure divers either freediving or using underwater breathing apparatus. Several factors influence the diver, including immersion, exposure to the water, the limitations of breath-hold endurance, variations in ambient pressure, the effects of breathing gases at raised ambient pressure, effects caused by the use of breathing apparatus, and sensory impairment. All of these may affect diver performance and safety.

References

  1. ↑ "The Caves of Mars - Martian Air Breathing Mice". highmars.org. Archived from the original on 24 July 2007. Retrieved 12 June 2015
  2. ↑ Courtland, Rachel (30 September 2015). "Suiting Up for the Red Planet". IEEE Spectrum. 52 (10): 36–38. doi:10.1109/MSPEC.2015.7274192. S2CID   46224902 . Retrieved 9 January 2019.
  3. ↑ Nuckols, Marshall L; Giblo, J; Wood-Putnam, JL (2008). "Thermal characteristics of diving garments when using argon as a suit inflation gas (abstract)". Undersea and Hyperbaric Medicine. 35 (4). Archived from the original on 2009-04-12. Retrieved 2008-10-24.{{cite journal}}: CS1 maint: unfit URL (link)
  4. ↑ D'Aoust BG, Stayton L, Smith LS (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 April 23, 2009. Retrieved 2008-08-28.{{cite journal}}: CS1 maint: unfit URL (link)
  5. ↑ Rahn H, Rokitka MA (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 April 27, 2009. Retrieved 2008-08-28.{{cite journal}}: CS1 maint: unfit URL (link)
  6. ↑ Pilmanis Andrew A, Balldin UI, Webb James T, Krause KM (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 . Retrieved 2008-08-28.
  7. ↑ Scubaboard.com (2010-03-25). "Accelerated decompression on an argon mix?" . Retrieved 2011-02-02.
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