Accelerated decompression on an argon mix?

[rjack321]

Um, and argon costs me more than helium.

Silly dive shop

As of last week, my gas supplier argon price was about 65% of my helium price.

 

[Rainer]

Shop He price is about $1/cf (I get it from Roger for about half that, and his cost is closer to 35c/cf). Shop Ar price is $1.50/cf. Little demand for the latter here in SoCal.

Silly dive shop

As of last week, my gas supplier argon price was about 65% of my helium price.

 

[Cave Diver]

Well, is it -- and if so, Why is it? My understanding that the issue is that 100% O2 is good because it has no N2 or He -- well neither would the Ar mix. As long as there is no N2 or He you have maximized the gradient -- at least that is my understanding.

RhoneMan -- Interesting question and one that begs for thoughtful responses.

Because Oxygen is metabolized by the body and it's not an inert gas that has to eventually come out of solution. One inert gas may have advantages over another inert gas, but none are going to be as effective or efficient as something that doesn't have to be off gassed.

 

[fppf]

Lots of na sayers for sure, man.

Anyway, here is an article for research in space sciences. Most people don't know, but astronauts need to decompress from the shuttle atmosphere to make an EVA. The space suits only have about 4.5 PSIA of internal pressure while the shuttle is held at 14.7 PSIA or normal atmosphere. The procedures followed use oxygen currently. This study looked at using an Argon oxygen mix for there decompression to 3.5 PSIA for mars missions. They found a significant increase in DCS incidence when argon was used over pure oxygen.

Staged decompression to 3.5 psi using argon-oxygen and 100% oxygen breathing mixtures

 

[rjack321]

Because Oxygen is metabolized by the body and it's not an inert gas that has to eventually come out of solution. One inert gas may have advantages over another inert gas, but none are going to be as effective or efficient as something that doesn't have to be off gassed.

Something relatively insoluble and non-narcotic could work, like neon. But you are making deco way more complicated and even more "arty" than it already is by adding neon to your deco mixes. There aren't alot of neon tables nevermind trimix bottom gas to neo-ox deco tables.

Oxygen works, it ain't broke, there's very little to fix here.

 

[rjack321]

Argon is wicked soluble in addition to being narcotic as all getup. If you breath it any deeper than 20ft you will of course offgas the N2 but will latter need to eventually offgas the argon.

Unfavorable results after preoxygenation with ARGOX indicate argon on-gassing was significant.

Staged decompression to 3.5 psi using argon-oxygen and 100% oxygen breathing mixtures

What he said

 

[Blackwood]

Shop Ar price is $1.50/cf. Little demand for the latter here in SoCal.

Plus it's usually sold in smaller quantities (6CF being most common down here), and even given the higher unit cost the total always seems like a bargain relative to 70+CF of Helium.

 

[Bubbletrubble]

100% o2 is the best treatment for dcs.

Well, is it -- and if so, Why is it? My understanding that the issue is that 100% O2 is good because it has no N2 or He -- well neither would the Ar mix. As long as there is no N2 or He you have maximized the gradient -- at least that is my understanding.

@Peter Guy: The fact that 100% O2 lacks any nitrogen or helium is not the only reason that pure oxygen is used for DCS treatment. Don't forget about the metabolic requirement for oxygen in the tissues. Breathing 100% O2 kills two birds with one stone, so to speak. Furthermore, we don't know to what extent breathing pure oxygen might improve cell signaling on a molecular level.

Argon cannot work the same kind of "magic" on the human body that oxygen can.

[Edited later: I see that Cave Diver just mentioned that oxygen can be metabolized whereas argon cannot.]

 

[Blackwood]

Because Oxygen is metabolized by the body and it's not an inert gas that has to eventually come out of solution. One inert gas may have advantages over another inert gas, but none are going to be as effective or efficient as something that doesn't have to be off gassed.

We don't metabolize oxygen with nearly 100% efficiency, and even if we did, we'd still have to get rid of the byproducts.

I can't point to it now, but I do remember reading some tests where they bent patients on pure oxygen.

 

[TSandM]

Interesting . . . the results of the space study certainly raise a suspicion in my mind that solubility may be more important than anything else. One of O2's qualities is that it is really very poorly soluble, and this is true of He as well. Hmm.