Quote: (Originally Posted by
James Appel)
I was wondering (and no I havent taken any tri-mix classes as evident perhaps by this question), but why don't people use a 79% helium 21% oxygen mixture as regular normal air diluent getting rid of the nitrogen completely, removing all nitrogen from the loop? And if your doing deep dives and using a diluent with less oxy, WHY use nitrogen at all?
Stupid is as stupid does...........
Some people do it is called Heliox, the disadvantages are
1) that it costs more as some "waste" is inevitable and you need compatible bailout mixes as well.
2) The deco is longer than with trimix/heliair as you off gas both the gases at the same time...
3) You dont get narked
4) There is possibly more likelyhood of OxTox as there is no narcosis buffer against it
5) Requires a booster pump to achieve high pressure He fills
I have not yet done anything that 10/50 was not appropriate for, however there are plenty of people here who have been way deeper.
If you use Heliox, like using heliair, you dont need a trimix analyser to do top ups, other advantages would be that cylinders dont get exposed to nasty compressor oil, and I supppose the gas density in the loop would be even lower so the WOB would be less.
Have to wait for a proper madman to come along and give you a more detailed answer!