Helium the Perfect Diver's Gas

[Blackwood]

DEMA effectively tried to ban it in 1991 without any scientific basis.

I could see them trying to ban helium since it makes high performance regs irrelevant

[joking]

 

[rjack321]

The liability could be an issue. I recall one shop that made me wait until the cylinder cooled to room temperature and then sit there for 5 minutes as their O2 meter "stabilized" for the confirmation of the mix. I'd hate to think what they would do if it there was He in the mix.

Its definately not hard to have trimix stratify, esp. in a longer narrower cylinder like an Al40. 5mins is actually far too little time depending on the rate they were filled (turbulent mixing) and the mix percentage. I usually lay my trimix fills on their side and leave them overnight before analysis.

Nitrox mixes much faster as the density of O2 and air is pretty similar. Although I kinda doubt this has much to do with perceptions about trimix "safety".

 

[rjack321]

I could see them trying to ban helium since it makes high performance regs irrelevant

[joking]

I know you were joking but its a good point. I've used unbalanced 2nd stages and similar "lesser" regs at some deeper depths (170') and thought they breathed just fine. There's definitely a deep = expensive high performance perception that is perpetuated by Navy air testing protocols etc at insane depths (insane depths for air that is)

 

[M_Bipartitus]

Sorry, I didn't specify. It was a 32% nitrox fill in an Al80. The reason I mentioned it, is that I found waiting for the tank to cool and then running 2l/min through the O2 meter for 5 minutes to be overkill for a Nitrox fill. My point, which I failed to make, was that the shop's concerns about liability caused excessive "safety procedures." If helium were used the recreational OW setting, it would likely be worse. If it maters that specific shop does not have any tech divers, nor do they fill trimix.

Its definately not hard to have trimix stratify, esp. in a longer narrower cylinder like an Al40. 5mins is actually far too little time depending on the rate they were filled (turbulent mixing) and the mix percentage. I usually lay my trimix fills on their side and leave them overnight before analysis.

Nitrox mixes much faster as the density of O2 and air is pretty similar. Although I kinda doubt this has much to do with perceptions about trimix "safety".

 

[Cave Diver]

"Helium will bend you more than nitrogen" from a fast ascent is a bit of a myth.
Rubicon Research Repository: Item 123456789/6582
and
Rubicon Research Repository: Item 123456789/6496

even under rapid "explosive" (5 second) decompression from >200ft trimix diving guinea pigs had 1.6x more nitrogen in their arterial blood gases. I wish I knew the mixes being dove, but the bottom line is that helium isn't very soluble so there's not as many moles to offgas. Fewer moles of gas in smaller bubbles to begin with = lower DCS risk not more.

Interesting data. How about the ICD arguements? Any thoughts?

 

[rjack321]

Interesting data. How about the ICD arguements? Any thoughts?

As examples, I switch from:
EAN50 to 18/45 at 30ft,
from 35/25 to 15/55 at 80ft,
both for backgas breaks.

And from 100% onto 18/45 or 15/55 for backgas breaks at 20ft too.

I think ICD is real, but its not an issue affecting (most) sport deco divers doing reasonably typical profiles/switches. It is a commercial/saturation/chamber deco consideration.

It might be a consideration if you are doing very deep stops/switches on mixes with >100ft ENDs. But the mixes+switches in common OC use today aren't extreme enough to manifest ICD. e.g. combinations of 15/55, 16/50, 35/25, 32%, 50%, 100% don't generate ICD. You need a deep switch from air back onto 10/70 or something like that. And people aren't using air for deco starting at 200+ft anymore ala Exley in Zacaton

 

[boulderjohn]

To return to the original question, I will echo those who say cost and then add availability. There are a lot of places where you just can't get it, whatever the cost.

That is a concern I have with the idea of training people to use nothing but standard gases, meaning some variety of nitrox, helitrox, or trimix on every dive. There are times that even nitrox is not available. Some people always dive in areas where there is always a shop nearby with big banks of EAN 32 ready to go, but a lot of us don't. Here in Colorado nitrox diving is very rare because most of our diving is shallow, and the shops that will blend it for you don't have any just hanging around.

The problem becomes even greater with helium. If you want a local helium mix, you really have to know somebody or do it yourself.

When we do technical training, we have to drive hundreds of miles to the nearest suitable site, and when we do we have to bring our own industrial bottles of helium and oxygen with us, and you need a lot of that stuff on a 3 day trip.

 

[Trace Malinowski]

Just having been to Bermuda this week, the captain of one dive boat told me that he never reopened his nitrox fill station after the hurricane due to prohibitive costs. Graham Mattocks at Triangle Diving told me that a storage bottle of helium costs him nearly $800.00 so much of his technical diving for exploration employs deep air. They already are using Optima rebreathers mostly to film the aggregate of black grouper to the islands, but these may be used for deeper exploration in the future.

I think that the availability of rebreathers will make helium diving more friendly in places such as Bermuda in which it is expensive to obtain because the additional costs to the diving consumer will be kept within reason.

I also think that winds of change are blowing within the diving industry in which adventure, exploration, and personalities from the technical world will be leading a crusade away from the present failing marketing model of DEMA and new heroes and legends will appear that will capture both the imagination of the public and the ears of the industry. The future of diving is rebreather technology and helium mixtures.

 

[hobodiver]

I seem to recall reading somewhere that because helium is a "fast" gas, it is more likely to produce a type II DCS hit.

 

[Peter Guy]

I'm more than a bit confused by the OP. Is this not the person who has been arguing for deep air? That we all should be diving deep air so that we can get acclimated to narcosis?

Color me confused.

But back to the OP's question -- Why not teach Helium from the getgo?

A. It doesn't take a rocket scientist know that He is a LOT more expensive than other gases.

B. Advantage -- what is the advantage of an He mix over 32% at most "real" recreational depths? Anything much above 100' seems to be OK for most divers so why even add He to the mix?

Yes, this is technical diving forum but the OP talked about He mixes for "open-circuit and CCR diving at all depths" so it would appear to be an appropriate response here.

C. Is there any Technical Diving Agency that does NOT teach He use for deep dives? I'm not saying they might not also teach deep air, but don't they all teach Trimix? If they do, doesn't this negate the OP's premise?