heliair

scu8astu

Ok here go's for my 1st thread.
i'm a meg trimix diver who only ever use's heliair, i find it easy to mix and much more flexible to use. but i have to say that at times when i've been on boats other rbr divers think that trimix is the better option.
but surely if i have a mix of 11/47 heliair then the rbr will mix it into trimix for me (by adding extra o2)to what ever level is right for a given sp. i'm sure i'm right about this . so why do i get funny looks when i'm out. also heliair is much more depth flexlible than trimix and you don't need o2 cleaned cylinders, everyones a winner.
so come on you lot tell me i'm wrong or agree with me i'd be intrested in your views


stuart

Stephane

Hi,

I don't see any failure in you way of thinking.
The only drawback of having a "weird" fO2 in your heliair is that when you flush with diluant, you have to do mathematics while reading the PpO2.
If you use a Tx20/something, it's much more easier. And even easier if you use heliox, for example Hx10/90.

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Stéphane

wedivebc

I have stopped adding O2 to my dil lately and can't really see a need for it since my breather can add the nessasary o2 during the dive.
I welcome funny looks from other divers though

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Cheers,

Dave....

Man is the only animal burdened with the knowledge he will eventually die

Dutchy

My bet is that OC divers will object to the high cost of He (especially in Europe) but on CCR who cares?

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Muzz

If he adds a little more helium in the mix it will come out 10/52. Then the math is even easier

teksimple

Heliair is great for stuff less than about 250'. After that I start getting narced, and the point of using helium is to get rid of the narcosis. So the main problem with heliair is it has too much nitrogen , and then not enough oxygen to be good for a decent bailout at a wide range of depths. Helitrox is the way to go for me, since its additional cost is negligible

Depth-junkie

10/52 heli-air it is for me

easy to mix and remix/calculate PPO2 at depth etc etc. 130bar helium top it up with air to 250bar and your good to go.

ATB
Gareth

lizardland

I'd thought about it too but then I figured that at the same depth a heliair is going to have a much lower fO2 than a true trimix aimed at that same depth which might make going SCR on heliair less than ideal. For example, I keep my max END to 25m, so 10/52 for me would be narc limited to 63m'ish but that's only 0.73pO2. With a true trimix I can aim it at 1.2 which means it's going to be longer between flushes if I go SCR so better use of onboard dil for bailout. I suppose you'd also use marginally less O2 in normal diving because your dil is going to be closer to your setpoint on arrival at depth.

For <30-50m diving I usually use heliair 17 though as I'm less concerned with SCR bailout.

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Janos

For normoxic depths I think it also adds risk if you have a hypoxic dil. I also like to have a high ppO2 on the bottom so I can SCR if needs be.

On the 'breather gas costs are so small that to me it makes no difference if I ask for 10/52 or 18/52.

Janos

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scu8astu

thanks for your comments, one question i have for you is what is helitrox and its mixing calculations