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AGA ACSC, semiclosed rebreather
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Exotic diving gases

 

Author: Matti Anttila, Ph.D.
Copying etc. prohibited without prior written permission by the author.
Comments: matti@antti.la. Last update 02/Mar/2006.

In case the reader of this page has comments, questions etc, I'm happy to receive them
by e-mail or web form.




  [suomeksi suomeksi ]

Table of contents:

 1.  What's this page for?
 2.  Helium-based mixes: heliox and different trimix mixes
 3.  Exotic diving gases: hydreliox, hydrox, neox, neoquad, argox, xenonox, kryptonox etc. strange named gases
 3.1  Hydrogen (H2): hydreliox and hydrox
 3.2  Neon (Ne), neox and neoquad
 3.3  Argon (Ar), argox and argonox
 4.  Theoretically possible inert gases for diving
 4.1  Xenon (Xe) and xenonox
 4.2  Krypton (Kr) and kryptonox
 4.3  Radon (Rn)
 4.5  The isotopes of noble gases
 4.6  Compounds
 5  Liquid breathing
 6.  Narcotic factors of gases
 7.  Summary table
 8.  Where can I get training?
 9.  How to do decompression schedules for exotic gases?

!   Warning:

Scuba diving is a safe hobby, but without proper training, equipment and attitude it may endanger yours and your dive buddy's life. The author takes NO responsibility about the information of this page.

Contents:


1. What's this page for?

I've gathered some information about exotic diving gases to this page, which are very rarely used in diving.


2. What are heliox, heliair or trimix?

Heliox is a mixture of helium and oxygen (HELIum-OXygen). Heliox is used on deeper dives than it's possible to dive with regular air.

Trimix means a mix of three components ("tri" and "mix"), and usually when people talk about trimix, they mean the mix of oxygen, nitrogen and helium. Trimix is used in very deep dives instead of air to reduce the partial pressure of oxygen (to avoid oxygen toxicity) and nitrogen (to avoid nitrogen narcosis). Trimix is also being used as travel gas or deco gas, depending on the situation.
The percentages of gas components vary depending on the dive. The deeper one go, the less there will be oxygen and nitrogen, and the more there will be helium.
Trimix mixes are labeled for example as "Trimix 10 50" or "Trimix 10/50", where 10 represents the percentage of oxygen in the mix, and 50 is the percentage of helium.

Terms for different trimix gases and labels:

  • Hyperoxic trimix: Oxygen content is more than 21%.
  • Normoxic trimix: Oxygen content is 21%, same as air has.
  • Hypoxic trimix: Oxygen content is less than 21%.
  • Heliair is a mixture of helium and air (HELIum-AIR). Heliair contains always less oxygen than air (in percentage, so heliair has less than 21% oxygen).
  • Triox is an other name for hyperoxic trimix. See: http://www.sfdj.com/spring/triox.html

More info:
Take a look at Trimix and heliox diving page.
See also: http://www.cisatlantic.com/trimix/trimix.html


Helium (He) fact sheet:

Density:
Thermal conductivity:
Narcotic factor (He/N2):
Additional info:
0.1787 g/liter
0.1513 Wm-1K-1
0.23
webelements.com


3. Exotic diving gases: hydreliox, hydrox, neox, neoquad, argox, xenonox, kryptonox etc. strange named gases

Hydreliox is a mixture of hydrogen, oxygen and helium (hydrox = hydrogen + oxygen). Neox is a mixture of neon and oxygen. Neoquad is a mixture of four gases: helium, neon, nitrogen and oxygen. Argox is a mixture of argon and oxygen. These gases are very exotic and rare diving gases. These gases are used mostly in scientific research or in commercial diving.


3.1 Hydrogen (H2), hydreliox and hydrox:

Hydrogen has been used succesfully in extremely deep dives (500 meters and more) with helium and oxygen. The COMEX (France) have studied the effects on divers of exposure to hydrogen-helium-oxygen at chamber depths to 2300 feet (701 m) (performed in 1992, test name: "HYDRA 10"), 1706 feet (520m) and in the ocean 1752 feet / 534m (performed in 1988, test name: "HYDRA 8"). The mixture of these three gases is called hydreliox. Logically, it doesn't really have any benefits to diving with open circuit SCUBA equipment (since it's not very good idea to dive to such depths, mentioden above, with OC...). More about COMEX's dives: http://www.under-water.co.uk/oct/comex.htm.
Hydrogen has also been used together with oxygen (hydrox), but this mixture is very explosive, if the percentage of oxygen is more than 4-5%. For this reason it's not possible to breathe this mix above 30 meters to avoid hypoxia.

Read more about hydrogen and diving:
  http://www.mindspring.com/~divegeek/mixhistory.htm
  http://www.divingheritage.com/modernairsupplykern.htm
  http://www.divingheritage.com/moderncomex.htm
  http://www.saa.org.uk/ratsnest/othermixedgases.html
In 1945 Arne Zetterström (Sweden) reached 535 feet (164 m) on a mixture of hydrogen, oxygen and nitrogen. Zetterström, who was 28 year old, lost his life in a hydreliox dive, because two military service persons, who were assisting him from the surface, misinterpreting the signals. There's also a book, written by Arne Zetterström and co-authored with Anders Lindén: "Arne Zetterström and the first hydrox dives", published by the Swedish National Defence Research Institute in 1985.


Hydrogen (H2) fact sheet:

Density:
Thermal conductivity:
Narcotic factor (H2/N2):
Additional info:
0.0899 g/liter
0.1805 Wm-1K-1
0.55
webelements.com


3.2 Neon (Ne), neox and neoquad:

Neon is less absorbed by body tissues than helium or nitrogen due to it's greater density, but it's also very expensive gas compared even to expensive helium. Instead of pure neon, there has also been use for crude neon mix, which is a mixture of 75% neon and 25% helium (crude neon is a by-product in air distillation). Neon as an inert gas seems not to have any narcotic effects in a dives less than 360 m depth, and it does not cause the distortion of voice like helium or hydrogen does. The density of neon limits it still mainly to depths less than 180 m, because neon is so slowly released from body tissues causing long decompression times. This is the reason why neon is mostly used in a short bounce-dives. Neon is mostly used together with oxygen (NEon+OXygen = "neox"), or with trimix (trimix = helium + oxygen + nitrogen) to make neoquad mix. DCS cases, where diver has breathed neon as an inert gas, are very hard to treat because of complex recompression schedules.

Mixed gas history: http://www.cisatlantic.com/trimix/aquacorps/mix/MixTimeline.htm


Neon (Ne) fact sheet:

Density:
Thermal conductivity:
Narcotic factor (Ne/N2):
Additional info:
0.853 g/liter
0.0491 Wm-1K-1
0.28
webelements.com




3.3 Argon (Ar), argox and argonox:

Argon is very narcotic gas (much more narcotic than nitrogen) and also very dense gas leading to breathing difficulties on very deep dives, but it does not cause the distortion of voice like helium or hydrogen does. In theory argon could be used as an decompression gas on shallow depths together with oxygen (argon + oxygen = "argox", argon+O2+N2 = "argonox") to reduce the inert gas absorbance into tissues on ~ 9-15 m decompression stops. Argox/argonox is not suitable for deeper dives due to the high narcotic effects.

Argox is still very rarely used and tested gas for breathing gas' inert component, and argon is mostly used pure as a dry suit inflation gas because of it's good thermal characteristics and relatively cheap price.

For more informartion about argon useage: [Click for more info]


Argon (Ar) fact sheet:

Density:
Thermal conductivity:
Narcotic factor (Ar/N2):
Additional info:
1.662 g/liter
0.01772 Wm-1K-1
2.33
webelements.com




4. Theoretically possible inert gases for diving

While regular gases like air, oxygen, nitrox and trimix are used in technical diving commonly, exotic gases mentioned above are very rare. However, there are still numerous gases which are theoretically possible for inert gas use. Some of them are listed below.




4.1 Xenon (Xe) and xenonox

Xenon (Xe) is a noble gas and non-toxic, therefore it could be used as an inert gas in breathing mixture together with oxygen (xenonox), but xenon is also very narcotic gas (it's an anesthesic gas too...) and that's why there's no real use for diving. Xenon is actually 25 times as narcotic as nitrogen. For a dry suit gas xenon could be nice, because it has very good thermal characteristics, but is has not been tested for that purpose enough. Xenon is also very, very expensive gas!

Krypton (Kr) (oxygen + krypton = kryptonox) causes dizziness, and it's not suitable for diving. Radon (Rn) is radioactive gas, and obviously not suitable for diving.


Xenon (Xe) fact sheet:

Density:
Thermal conductivity:
Narcotic factor (Xe/N2):
Additional info:
5.59 g/liter
0.00565 Wm-1K-1
25.64
webelements.com




4.2 Krypton (Kr) and kryptonox

Krypton is a noble gas, but not suitable for diving use. Krypton (Kr) (oxygen + krypton = kryptonox) causes dizziness. Krypton is also very expensive gas.


Krypton (Kr) fact sheet:

Density:
Thermal conductivity:
Narcotic factor (Kr/N2):
Additional info:
3.553 g/liter
0.00943 Wm-1K-1
7.14
webelements.com




4.3 Radon (Rn)

Radon (Rn) is the heaviest gas, and chemically it is completely inert. However, it is radioactive (its longest lived isotope has a half-life of only 3.8 days), and obviously not suitable for diving. By numbers only, radon could be good choice for dry suit inflation gas because of it's great thermal insulation properties.


Radon (Rn) fact sheet:

Density:
Thermal conductivity:
Narcotic factor (Rn/N2):
Additional info:
9.73 g/liter
0.00361 Wm-1K-1
?
webelements.com




4.4 The isotopes of noble gases

Isotopes of a chemical element are atoms whose nuclei have the same atomic number (Z), but different atomic weights (A). The word isotope meaning at the same place, refers to the fact that isotopes are located at the same place on the periodic table.

Deuterium (H22) is a heavier isotope of normal hydrogen (protium, H12), but too expensive to use in diving.


4.5 Compounds


5. Liquid breathing

Liquid breathing (fluid breathing) is only performed in scientific research studies and medical treatments. The fluid, which is used in breathing, is called "LiquiVent®". There are plenty of information available in the Internet:

About the "Abyss" movie: http://www.scienceweb.org/movies/abyss.html
LiquiVent: http://www.allp.com/LiquiVent/lv.htm
Google: http://www.google.com/search?q=liquid+breathing
Bibliography about liquid breathing: http://www.mindspring.com/~divegeek/biblios/liquid.htm


6. Narcotic factors of gases:

Narcotic factors of gases:

  (Chemical sign, name, factors (divide by / multiply by) )

  He, helium, 4.26 / 0.23
  Ne, neon, 3.58 / 0.28
  H2, hydrogen, 1.83 / 0.55
  N2, nitrogen, 1 / 1
  Ar, argon, 0.43 / 2.33
  Kr, krypton, 0.14 / 7.14
  Xe, xenon, 0.039 / 25.64

(Source: "The Physiology and Medicine of Diving" by Peter Bennett and David Elliott, 4th edition, 1993, W.B.Saunders Company Ltd, London.)

The table above is based on narcotic effect of air (=1). So, for example, xenon (as diluent gas in same percentage as nitrogen in air) in breathing mix is 25.64 times as narcotic as nitrogen. Or helium is 4.26 times less narcotic than nitrogen, etc.
It is also good to know, than oxygen is narcotic in high partial pressures. Some sources claim it to be as narcotic than nitrogen (Bill Hamilton, http://www.tekniskdykking.org/tekniskdykking/artikler/aqua/RWHNitrox.htm.


7. Summary table:

gas chem. sign / ingredients use price.:
(10ltr*200bar)
(Finnish price converted to US dollars)
other
air 78,1%N2, 20,8%O2,
0,9%Ar, 0,2% other
common diving gas ~$ 5 compressed air is the most common gas for diving
nitrox oxygen (O2) and nitrogen (N2) mixture hyperoxic nitrox: see below: EANx.
hypoxic nitrox: longer bottom times on 50-60 m dives. This gas was used mainly decades ago on commercial dives. Oxygen percentage is less than 21%.
hypoxic nitrox:
~ $8-15
hypoxic nitrox gives you stronger nitrogen narcosis and longer decompression, but it reduces the CNS% load
EANx / enriched air oxygen (O2) and nitrogen (N2) mixture oxygen percentage more than 21% ~ $6-15 commonly used
oxygen O2 decompression gas ~ $8-15 maximum diving depth 6 m
trimix oxygen (O2), nitrogen (N2) and helium (He) mixture deep diving gas ~ $8-100 depending of helium percentage used on deep dives for reducing the partial pressure of oxygen and nitrogen narcosis
heliox oxygen (O2) and helium (He) mixture deep diving gas ~ $50-100 used on deep dives for reducing the partial pressure of oxygen and nitrogen narcosis
argon Ar dry suit gas ~ $10-30 dry suit gas, mostly used with trimix (which is not suitable for dry suit gas due to it's high thermal conductivity)
argox oxygen (O2) and argon (Ar) mixture decompression gas ~ $10-30 used on ~9-15 m decompression stops, see above "argox"
hydrox oxygen (O2) and hydrogen (H2) mixture deep diving gas ? $ explosive, mixture not breathable above 30 meters
hydreliox oxygen (O2), heliumin (He) and hydrogen (H2) mixture deep diving gas ? $ explosive, mixture not breathable on shallow waters
neox oxygen (O2) and neon (Ne) mixture deep diving gas ~ $2000 rarely used, very expensive
neoquad trimix and neon mixture deep diving gas ~ $2000 rarely used, very expensive
xenon pure xenon (Xe) N/A, (dry suit gas?) ~ $4500 very good thermal insulator, but too expensive
xenonox xenon (Xe) and oxygen mixture useless for diving ~ $4500 extremely narcotic
kryptonox krypton (Kr) and oxygen mixture useless for diving ~ $8000 extremely narcotic


8. Where can I get training?

There is not really training courses for exotic diving gases, which are described in this page. Diving with hydrogen or neon is very rare, mostly commercial or related to some sort of experiences (and though dangerous...). Training courses for other gases than ordinary air:

Training agencies for nitrox and trimix diving:

GUE (http://www.gue.com):
For example: Tech Diver 1-3 courses.

IANTD (http://www.iantd.com):
Basic Nitrox Diver, Advanced Nitrox Diver, Technical Diver, Normoxic Trimix Diver and Trimix Diver courses.

DSAT (http://www.padi.com):
Tec Deep Diver and Tec Trimix Diver course.

PADI (http://www.padi.com):
Enriched Air Nitrox Diver Specialty course.

CMAS (http://www.cmas.org):

NAUI


9. How to do decompression schedules for exotic gases?

Making your own decompression schedules requires thorough understanding of decompression theory and inert gas properties. There are several web-based decompression tables for air and nitrox diving. Nowadays, several decompression software include helium. You may try Google with keywords "decompression software" and see how many links to different deco SW there are!

However, not many decompression software include exotic gases, like neon or argon. I'm not aware of any software that includes krypton, xenon or others strange gases (and there is really no need for them, too..).

Departure decompression software has neon option too (in addition to air, nitrox, heliox or trimix dive planning).

For argon, Abyssmal's Abyss decompression software included it, but the SW manufacturer's website is not anymore working. See this image and company's web site.


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