Helium the Perfect Diver's Gas

[M_Bipartitus]

I hope that's the case. Commercial divers have experienced HPNS well before 500' with slow descents. With the rapid descents of recreational divers, Personally I'd be concerned after 350'.

There are very few divers who go past 300 feet for recreation. I can only think of a handful of divers in non-commerical divers who have been to 500 feet.

 

[ianr33]

While agreeing that sub 300 foot dives are not exactly common I suspect that hundreds of divers have been past 500 feet.

 

[hobodiver]

I have to second the opinion that the size of helium atoms doesn't necessarily mean it forms small bubbles.

 

[lamont]

Given that this is asked in the Technical Diving forum ... no.

Anyone diving at the tech level should have solid buoyancy control skills, and a fundamental understanding of why slow ascents are important.

I would, however, recommend that someone who's a newer or an occasional vacation diver consider the drawbacks of using helium until they've gained enough practical experience to solidify their basic skills ...

... Bob (Grateful Diver)

Why not make DIRF or Intro to Tech also Helium cards?

Divers who pass those courses should be able to avoid blowing up from 100' to the surface directly, and should be able to do something approximating minimum deco stops.

 

[Rhone Man]

While agreeing that sub 300 foot dives are not exactly common I suspect that hundreds of divers have been past 500 feet.

I'll take the "under" on hundreds. There are not too many that go that deep.

 

[Rhone Man]

Pump up the arg-ox and let's go diving!

I remember suggesting to an instructor once that if they wanted students to experience narcosis, blending some arg-ox would be the safest way to do it (assuming the instructor wasn't breathing it too...). She looked at me like I was from Mars.

 

[Blackwood]

I remember suggesting to an instructor once that if they wanted students to experience narcosis, blending some arg-ox would be the safest way to do it (assuming the instructor wasn't breathing it too...). She looked at me like I was from Mars.

I saw a guy dressed as a scuba diwver this Halloween. His tanks (dubs) were marked Nitrous Oxide. I suppose that could work too

 

[DCBC]

I have to second the opinion that the size of helium atoms doesn't necessarily mean it forms small bubbles.

I was the Diving Operations Officer (Navy) at DCIEM when we were developing the Helium decompression tables to 100 meters; which replaced the U.S. Navy Tables. It was observed by the hyperbaric physicians at that time, that bubbles were detected (doppler testing) on every dive. The off-gassing bubbles varied in size and amount.

With Helium, the bubbles were found to be smaller and given off at a faster rate than those of air. Although this thread isn't a proper venue for discussing the research, the following link will give you some insight into doppler bubble testing (http://rebreatherpro.typepad.com/Bubblesdcs.pdf). Dr. Sawatzky's thesis had more information on these specifics.

BTW, I was one of the divers mentioned that contracted a Type I DCS hit during the testing process. Hope this helps some.

 

[hobodiver]

With Helium, the bubbles were found to be smaller and given off at a faster rate than those of air. Although this thread isn't a proper venue for discussing the research, the following link will give you some insight into doppler bubble testing (http://rebreatherpro.typepad.com/Bubblesdcs.pdf). Dr. Sawatzky's thesis had more information on these specifics.

That may well be, but that doesn't mean it's because of the size of the helium atoms. Assuming the bubbles weren't exactly the same size, there was a 50% chance of them being smaller vs. larger.

 

[rjack321]

That may well be, but that doesn't mean it's because of the size of the helium atoms. Assuming the bubbles weren't exactly the same size, there was a 50% chance of them being smaller vs. larger.

Its not due to chance, the smaller bubble size of helium is fairly well established. "Proving" why is not so simple since many there are too many variables with N2 and no way to eliminate those variable.

Most plausible reasoning: Lower solubility = fewer moles of gas = smaller bubbles. Or possibly because helium is a true inert gas and can't actually dissolve like (e.g.) salts dissolve into a polar liquid like water.