Nitrox - Trimix

[Chris H]

Such kind words from the President of said club

[Vtach]

Such kind words from the President of said club
[/quote]

That's funny shizzle!

Ya know, everyone has to have their token charity. ;D

[Dewit2it]

Being that I'm only air certified, I saw a documentary on a glacier that had an internal lake inside it.  They mentioned that they had to fill their suits with argon instead of the nitrox/trimix to prevent the additional intake of O2/N2 thru the skin, and messing up deco.  This was a high altitude dive.  Any truth to this?

I think this might have been on Nova a year or so ago. 

[Chris H]

Deleted for misinformation  I should have stayed at a Holiday in Express last night

[matt t.]

I'm going to take a wild stab at "Transdermal Counter Diffusion".
Hopefully someone with more knowledge will come along and explain it ;D.

[DiveCaptDean]

i googled it.........but i didnt have my star wars secret decoder ring with me at the time..so, i too like matt will let someone else try to explain....having to use argon not because of its better qualities for dry suit warmth, but rather because it may not absorb as quickly...in a high altitude dive.....seems a little fishy to me..but i am no expert

[Dewit2it]

I was wrong on the transdermal thing, but I knew it was some weird reason. 

It was a Nova episode on Mt. Blanc.  I found the transcript.  They couldn't use the nitrox as it could ignite the insulation under their drysuits.  Sounds like a high O2 mix for the 24 meter high altitude dive.

That could make the dive a LOT warmer! :o 

[Vtach]

Quite a bit of this information has to do with what is termed as "Isobaric Counter Diffusion" or ICD.  From my understanding, on a cellular level, it means that 2 dissimilar inert gases will move in opposing directions at an equal pressure (one going in and the other out).  It seems to be generally explained that mechanism for this movement is across a gradient from high concentration to low concentration (going back to the semi-permeable membrane stuff).  How rapid the movement across the gradient seems to be the unanswered question.  Some folks say it is based on diffusability and others say solubility.  Either way, ICD can work against you or work for you depending on how strategic you are with gas management.  From a diffusability perspective, if you are breathing a "light/rapid" gas at depth (Helium) and switch to a "heavy/slow" gas (nitrogen/air), you will only help to accelerate the removal of the helium.  However if you are breathing a "heavy/slow" gas at depth and switch to a "light/fast" gas you run a significant risk of becoming bent due to the "light" gas quickly saturating the tissue and pushing out the "heavy" and causing bubble formation.  Argon is a "heavy/slow" diffusing inert gas and by using it for suit inflation you help to reduce the risk of a "transdermal" counter diffusion when breathing/circulating a "light/fast" breathing mixture along with the benefit of thermal retention due to gas density and high insulating properties.

That's my synopsis of ICD as I understand it.  If anyone else out there can add or strike me down as a blasphemer, have at it ;D

[DiveCaptDean]

My vocabulary isnt any where near where it would need to be to do such a thing...i will pass on the offer..... ;D

[matt t.]

FTB!