What is your personal "Helium" Depth?

[Storker]

I think that the CO2 retention issues are pretty similar, [...] generally the guidelines seem to make sense for OC and CC.

That's what I was thinking, too, but since I know next to nothing about CCRs, I wanted to check if there was something I had no clue about that made a significant difference between OC and CC.

 

[ofg-1]

These days, 120 feet is my max without at least one mole of helium in my mix.

 

[oya]

These days, 120 feet is my max without at least one mole of helium in my mix.

Isn't the extra high-pitched squeaking of the helium mole annoying?

For me:
Same as most here. With the rebreather I've almost always got 10/50 in my dil because... well... why not?
130-150 I'm only going without He if it just isn't an option. Deeper than that I'm going to be very grumpy without it (though I probably won't remember being grumpy -- or very much of anything at all -- afterwards)

 

[Dr Simon Mitchell]

That reports seems to deal exclusively with CC. Would you use the same gas density guidelines on OC?

Hi Storker,

I have replied to a similar question in the parent thread. But yes, I think that would be a wise choice. I will clarify if necessary when I hear from Gavin.

Simon

 

[ofg-1]

Isn't the extra high-pitched squeaking of the helium mole annoying?

No, you are mistaking a mole of helium for a gerbil of helium.

 

[Rainer]

Depends on the dive. In the past, I've done air to 130' in warm, clear, open water and been fine. I've done air/28% in cold water at similar depths and been rather disoriented.

These days (all open water), I'd do 32% down to 110'. Anything deeper, and I'm adding helium.

 

[victorzamora]

I think that the CO2 retention issues are pretty similar, obviously CCR specific factors like WOB with counter lung placement etc will complicate the issue but generally the guidelines seem to make sense for OC and CC.

The way I see it is they're similar, but the decreased WOB on OC should improve CO2 retention. My guess would be that the guidelines provided in that paper are a great OC reference and would work fine, but the decreased WOB on OC would make those guidelines slightly (not sure how to quantify) more conservative.

No, you are mistaking a mole of helium for a gerbil of helium.

Easy mistake to make.

 

[exposure]

130 feet if open water, good viz and no penetration. In a very cold and silty quarry, with very bad viz (1m) I raise that up to 80 feet. I teach Air down to 165 feet on Air (PADI Tec 50) but I clearly explain that this is before the student move on to Trimix (temporary step).

 

[Storker]

These days, 120 feet is my max without at least one mole of helium in my mix.

So... If you go to 130' on an Al80, you'd prefer at least something like 20.8/0.2?









(For the benefit of those who didn't quite get this extremely nerdy joke - or pun: 1 mol - or "mole" - of any gas is 22.4L - or 0.8 cu.ft. at STP. Mix 79.2 cu.ft. of EAN20.9 with 0.8 cu.ft. of He to get 80 cu.ft., and your final mix will be approximately 20.8/0.2)

 

[Rainer]

130 feet if open water, good viz and no penetration. In a very cold and silty quarry, with very bad viz (1m) I raise that up to 80 feet. I teach Air down to 165 feet on Air (PADI Tec 50) but I clearly explain that this is before the student move on to Trimix (temporary step).

I'm sincerely curious about this. Why would you teach a diver absolutely new to diving this deep to use a mix you yourself say you wouldn't dive?