Max FHe in a mix

[kris979]

Hi,

I was wondering if there are any restrictions, considerations, or calculations wrt the amount of Helium you can put in your mix.

Thanks,
kris

 

[tbone1004]

none at all, heliox is used in many industries for extremely deep diving. There are physiological issues with extremely high helium percentages, but we are talking in the 90's for deeper than 200m, not "normal" technical diving depths.

 

[Alaskan Scuba Dude]

Minimum 16% 02 in the mix if you're considering breathing He on dry land.

 

[Alaskan Scuba Dude]

Minimum 16% O2 in the mix if you're considering breathing He on dry land.


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[Wibble]

I was wondering if there are any restrictions, considerations, or calculations wrt the amount of Helium you can put in your mix.

Not as such.
Obviously you need to have sufficient oxygen to sustain life, i.e. not hypoxic.
Expense is the main constraint.
Some nitrogen is required even in extreme depths.

What sort of depths are you thinking about?

 

[rjack321]

Hi,

I was wondering if there are any restrictions, considerations, or calculations wrt the amount of Helium you can put in your mix.

Thanks,
kris

high pressure nervous syndrome (HPNS) is a consideration for extremely deep dives in the 200m+ range. But those are basically the realms of commercial divers in diving bells and such - not joe or jane schmo the sport diver. Slowing the rate of descent, or adding another inert gas to the helium-O2 mix can sometimes be used to mitigate these impacts, either small amounts of nitrogen or hydrogen. So yes there are physiological limits and considerations.

 

[broncobowsher]

There can be issues when switching mixes with vastly different levels of Helium. I would have to refresh myself on the gas diffusion rules. I will likely be corrected on this, but don't go from a 90% He mix to straight air. Or is it the other way around?

 

[GiraffeMarineSalvage]

There can be issues when switching mixes with vastly different levels of Helium. I would have to refresh myself on the gas diffusion rules. I will likely be corrected on this, but don't go from a 90% He mix to straight air. Or is it the other way around?

It's way above my pay grade (or current personal experience) but I think the issue you're thinking of is "isobaric counter diffusion" (ICD)?
ie dramatically oversimplified avoid dramatic gas mix changes on technical dives (and if you know enough to safely be doing those types of dives you either know enough it's practically instinct or you can factor that consideration into your gas/bailout choices?).

 

[broncobowsher]

It's way above my pay grade (or current personal experience) but I think the issue you're thinking of is "isobaric counter diffusion" (ICD)?
ie dramatically oversimplified avoid dramatic gas mix changes on technical dives (and if you know enough to safely be doing those types of dives you either know enough it's practically instinct or you can factor that consideration into your gas/bailout choices?).

Yes, that's it. All my reference books are packed away, getting ready to move.

This is not something I have to deal with at my depth of diving as well, but know of it. If someone is looking what an extremely high level of Helium can be used up to, figured they should know that they can't do extreme switches of gas as well.

 

[Wibble]

This thread has some pertinent information

Doc Deep dies during dive.

Split from another thread. Dr. Guy Garman died during his deep record attempt. This thread has been split into the Accidents forum in order to allow for stricter moderation Scubaboard friends I'm saddened to say that today's attempt at a world record deep dive ended in tragedy. Dr. Guy...

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