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

[jayfree]

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!

 

[jonnythan]

You can... now figure out how much it would cost to fill a set of 130s of the stuff, not forgetting you'll need to boost..

 

[MSilvia]

Tell your friend that technical divers do something that's very much like that, although not always using 21% O2. As far as I know, the biggest problem is that helium is expensive. Most divers use enough helium to reduce the nitrogen content to a level that makes the gas have an narcotic potential equal to breathing air at a shallow depth.

Helium has to be off-gassed much like nitrogen though, so using a high He gas blend doesn't mean you can stay down indefinately or blow off decompression stops.

If he's interested, you might recommend he read up on trimix, heliox, and nitrox, and take classes along those lines when he's got a lot more experience.

 

[jonnythan]

Hint: going by Fill Express' prices (75 cents/cf for He and 30 cents/cf for O2), that's over $170, whereas prebanked 30/30 is less than half that.

I've asked this question and been told that it's way too expensive, difficult to fill, and has little benefit. I bet 79% He would do a great job of making you cold too.

 

[Mako Mark]

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

 

[wedivebc]

Hint: going by Fill Express' prices (75 cents/cf for He and 30 cents/cf for O2), that's over $170, whereas prebanked 30/30 is less than half that.

I've asked this question and been told that it's way too expensive, difficult to fill, and has little benefit. I bet 79% He would do a great job of making you cold too.

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

 

[jonnythan]

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

Why would you waste money on Nitrox when air is perfectly fine?

 

[wedivebc]

Why would you waste money on Nitrox when air is perfectly fine?

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

 

[Diver0001]

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 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..

 

[boomx5]

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

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