79%Helium - 21% O2 blending? Why not?

[jonnythan]

I find the advantage of nitrox justifys the slightly higher expense.

There's your answer.

 

[jayfree]

Thanks to all! I thought possible... but wasn't sure

 

[ERP]

Not sure why you would waste $85 for a gas that is only usable to 120fsw?Nitrox fill are less than $10

I don't dive triox frequently, but I have done so for training and IMO the difference is very noticeable, at least in 40 degree water at 90 ft or so.

Do a 100+ft dive on 32% then do the same dive on 30/30. IME I enjoyed the dive more on the 30/30 largely because of the lack of narcosis.

Having said that I wouldn't pay $85 to do most dives on 30/30, but it's a question of what a clear head is worth to you. And that's probably as dependant on the dive and the diver as much as anything.

30/30 fills around here are also a lot less than $85.

 

[wedivebc]

I actually only pay about half that. Also, when I get my blending station put together it will be even less.

I blend my own trimix and for deeper dives the expense of helium is a nessesity. For 120ft dives I won't waste my money. Just don't see the benefit being worth the expense.

 

[BCS]

it might be a bit cold too. Or consider buying a thicker pair of undies.

I know this is off topic but relevant to breathing helium, as long as you don't use it to inflate your suit, it doesn't cool the body anymore than breathing air.

dive safe!---brando

 

[Otter]

Divers use mixes like that. It eliminates nitrogen problems but you get helium problems in the trade. On balance you don't win anything with heliox (that's what it's called) unless you dive really deep.

R..

As long as its not REALLY REALLY deep, due to HPNS.

Summarizing....HE/O2 mixes within Recreational Depths....

1) Since you need to off-gas Helium much the same as Nitrogen, you aren't buying much in terms of no decompression limits...and in fact, helium is far less forgiving of missed stops and fast ascents. It would be more effective to use Nitrox to increase your bottom time

2) Main benefit of using helium over air would occur in the 100' - 130' range where you could lower you effective narcotic depth (rule of thumb is an END of 100'). Some might say the Nitrox helps here, but it doesn't as O2 has as much (possibly more) narcotic effect as nitrogen.

3) Helium is WAY more expensive than Air or Nitrox and is relatively rare. If we could just stop kids from getting helium balloons, we'd all be better

4) Your question specifically addresses a 79/21 mix -- which is fine within recreational limits. However, to go deeper (say 185+), you need to decrease the FO2 (percentage of O2) to avoid Oxygen Toxicity. As you decrease the FO2, you quickly find you don't have enough O2 to sustain life at shallower depths, so you introduce travel gasses and switching.....and enter the realms of Technical Diving.

 

[boomx5]

I blend my own trimix and for deeper dives the expense of helium is a nessesity. For 120ft dives I won't waste my money. Just don't see the benefit being worth the expense.

I see it as very justifiable since it makes the dive more enjoyabe. You know, when you're not narced but your buddy is...that alone is worth the price of admission.

 

[jbd]

An anesthesiologist friend of mine who is going through open water cert asked me: Why can't one use/blend 21% O2 and 79% Helium as a diving mix? He says they use that mix in medicine quite frequently and would seem to eliminate the Nitrogen problems.....
Thanks!

Divers don't have insurance companies paying for the fills

From the above responses it seems a pricey way to dive for little if any benefit, from a safety perspective, based on statisitcs.

 

[MSilvia]

it seems a pricey way to dive for little if any benefit

Unless you're diving outside of standard recreational limits. If you're going to be spending time below 130', you may not want to go without it.

 

[Mako Mark]

I know this is off topic but relevant to breathing helium, as long as you don't use it to inflate your suit, it doesn't cool the body anymore than breathing air.

dive safe!---brando

err really? my understanding is that it does, through the lungs.

A rebreather doesnt have anything to do with your suit either, but it keeps you significantly warmer because you are breathing gas warmed by the chemical reaction of scrubber material.

You wouldnt want to use helium for suit inflation, it is a contentious subject, but Isobaric counterdifusion "could" potentially cause this problem. Personally I have never heard a confirmed example of this.