Effect of gas density while deep diving

[rjack321]

Wouldn't it be nice if Deep Stops had disappeared that quickly...

But but but Rich Pyle!

In compare of 40 atm test with Neon (ρ=0.9) and use of Helium for standard mixes (ρ=0.17) - it is nothing (please, see smile at the end of my message)
Neon has weight of 36 g/l at 400m.
Helium has 6.8 g/l at 40m.
Five time bigger. And "human rabbits" has staying alive at the end.

P.S. Overbalanced Aqualung Legend (and Apeks then) was developed exactly to help with bigger gas mix density.

so basically you are ignoring science, got it!

 

[Swamp_monster]

Are you really talking about breathing gas density for non professional divers???
Also about "feeling" of gas density near 40m (120ft) depths???
Please, read this Forgotten experiment "Neon 400" Here really was a problems.
And forget about "problems" with gas density for others, than commercial deep divers..

I have read this and it is very interesting however... Newer data shows many different safety concerns and this experiment does not say anything about co2 retention with gas density. Regardless the testing is pretty incredible and makes me think there is much more testing to be done. Thanks for sharing, I will not be considering any data from this experiment in my diving though.

 

[Kay Dee]

Anyone who thinks they already have a gas density / work of breathing issue when diving OC air at or about 40m needs to buy themselves a better regulator!

Edit: It also should be noted that there is a difference between 'deep stops' and so-called 'Pyle stops' (as far as the deco profile goes), but many people seem to think they are one and the same. Not advocating for or against them, just want to 'register' the fact that there is a difference and the two should not be considered one and the same deco profile.

 

[fsardone]

Wouldn't it be nice if Deep Stops had disappeared that quickly...

You are an arsonist!
The issue is not the deep stop, is the aidea that stopping deep would shorten the shallow deco time .... this is really arson


Back on topic .... While on OC the only work you do is keep the 2nd stage walve open by creating a slight depression in the regulator. On CCR you need to keep all of the gas in the loop moving through the scrubber. It really makes a difference. Try to switch from diluent air to heliair at 40 meters. And you will have a revelating moment. Both for density and narcosis.

 

[Kay Dee]

On CCR you need to keep all of the gas in the loop moving through the scrubber. It really makes a difference

And there, as they say, lies the rub. Comparitively speaking, for the same gas (in this case air shall we say) the WOB is greater the deeper you go on a CCR as you are doing the work (or the W in WOB) as opposed to a mechanical assist - as it were - on OC almost 'forcing' the air into your mouth.

Hence why I would dive OC air deeper than CCR air (if I had too, which I don't).

 

[fsardone]

Hence why I would dive OC air deeper than CCR air (if I had too, which I don't).

Concur

 

[Lorenzoid]

Anyone who thinks they already have a gas density / work of breathing issue when diving OC air at or about 40m needs to buy themselves a better regulator!

Or more likely, needs to get their regulator tuned. It's my understanding that at that modest depth WOB doesn't vary among (properly tuned) regulators enough to be noticeable to most people.

 

[100days-a-year]

Haven't noticed any WOB issues on deep air or lean nitrox diving my Tabata regs. I feel more resistance in thicker wetsuits shallow.
There is a threshold I'm sure where WOB, CO2 retention and narcosis become an issue due to gas density but IME it's subjective.
I also reiterate that some folks are impaired @ PPN .79 and adding any diving or other task loading only compounds it.

 

[rsingler]

There is a threshold I'm sure where WOB, CO2 retention and narcosis become an issue due to gas density but IME it's subjective.

But if you are part of the population (10-30%) that does not automatically hyperventilate in response to elevated CO2, then you lose the trigger that alerts you to a CO2 hit before it's too late.

Perhaps there will eventually be a medical screen made available to divers that want to start Tec, to alert them that they're part of this population-at-risk. It would be an easy enough clinic to set up. Haven't thought about how many divers you'd have to see at what price to make it work financially, tho...

 

[100days-a-year]

Exactly, there are too many variables between divers physical condition, locations, gears etc..for me to accept a blanket limit that is shallower than many thousands if not some millions of dives have been safely completed to.