Exactly how deep is "Deep Air?"

[Superlyte27]

But his END was what? 400' or so ft?

I doubt it, what would be the point in Helium then.
I'm sure you know you can tailor helium to any END you want, from 4 percent Oxygen to 40 percent Oxygen. I'm only guessing, but considering his knowledge and financial backing, i'm certain he wasn't skimping. With 27 Bottles of gas on that dive, I'm pretty sure he was diving several mixes of HE. It would be stupid to have an END of 400' when you can have any END you want at any depth.

 

[DaleC]

You're playing too fast and loose with your stats.
Either your gripe is with people diving deep air or it's with people diving high END's regardless of the mixes they use.
Shecks name would not be in a list of the first but could be included in a list of the second.
I personally think both Exley and Shaw died from the physiological effects of extreme depth itself, and not neccisarily from the gas they were breathing.

 

[Superlyte27]

Manion's record was for the deepest ever dive on air. Exley's record (subsequently broken several times) was deepest ever dive on any gas mixture.

I'm pretty sure Exley's dive was deepest ever cave dive on any mix.

 

[Superlyte27]

You're playing too fast and loose with your stats.
Either your gripe is with people diving deep air or it's with people diving high END's irregardless of the mixes they use.
Shecks name would not be in a list of the first but could be included in a list of the second.
I personally think both Exley and Shaw died from the physiological effects of extreme depth itself, and not neccisarily from the gas they were breathing.

I agree. Sheck said himself that he "grayed" out on the previous dives at those depths. He started mixing argon to try to get used to the affects of the breathing mediums he was using. I guess ultimately it didn't work.

 

[PfcAJ]

I've always said the same thing: Deep air (to include high ENDs) is a bad idea. And irregardless isn't a word

Superlyte, I found this on the IUCRR website "Both Bowden and Exley selected a bottom mixthat would produce a tolerable PO2 of less than 2.0 atm and an equivalent narcosis depth (END, the equivalent depth on air) of 274f/84 m at 970 f/298 m. These levels were accepted by both diverssince the exposure to maximum depth would be brief (not that a higherPO2 would minimize the lengthy decompression at the cost ofincreasing the risk of CNS oxygen toxicity."

So you got me, the END was closer to 300', not 400'. My bad.

 

[PfcAJ]

After a reread, I found this:

"Exley had used some of his trimix 10.5/50travel mix for the descent, but would not have consumed gas down to 500 psi on that portion of the dive. The travel mix could have been lost to free flow, but more likely Exley breathed it when the supply of trimix 6/29 was exhausted. This was a "hot" mix at 879 f/270 m,where the PO2 would be 2.9 atm; the equivalent narcosis depth was 423f/130 m, and the gas density 21 g/l, equivalent to breathing air at487 f/154 m."

 

[DaleC]

Another way in which facts can "seem" to support an idea but where other factors may "actually" be at play came up during a recent chamber visit/lecture.

Conventional wisdom would say that most recreational DCS hits occur because divers violate their NDL's in some form or another and, therefore, one might lobby that reduced NDL limits should be implemented to improve diver safety. But in fact, the majority of DCS hits (according to the chamber Manager/MD occur because of undiagnosed PFO's or rapid ascents within NDL limits. The real solution (aside from the PFO's) is to reduce ascent rates, not NDL limits.

Deep air is like that. There are more factors at play (personal tolerances, conditioning, training/lack of training etc...) than just an artificial END. You may set an END and have everybody follow it but after He use becomes mainstream there could be just as many deaths as before. Divers going deeper with less training because of a reduced fear of narcossis, divers performing increasingly complex dives at depth because they are now on He, recreational depths dropping into the technical realm because of He use etc...

Is violating a preset END the real problem or is overdiving ones experience and training, irregardless of mix, the real culprit?

BTW, I don't have all the answers but I think I know some of the questions to ask.

PS. Thanks for the spelling lesson; I totally support your hypothesis now.

 

[ianr33]

After a reread, I found this:

"Exley had used some of his trimix 10.5/50travel mix for the descent, but would not have consumed gas down to 500 psi on that portion of the dive. The travel mix could have been lost to free flow, but more likely Exley breathed it when the supply of trimix 6/29 was exhausted. This was a "hot" mix at 879 f/270 m,where the PO2 would be 2.9 atm; the equivalent narcosis depth was 423f/130 m, and the gas density 21 g/l, equivalent to breathing air at487 f/154 m."

So?

If my remaining life was measured in seconds I would breathe anything I happened to have on me.

Would you DIR types rather die than use an END>100 ?

 

[captain]

Manion's record was for the deepest ever dive on air. Exley's record (subsequently broken several times) was deepest ever dive on any gas mixture.

Deepest open circuit scuba dive
Pascal Bernabé (Ralf Tech/WR1 Team) on July 5, 2005 descended to 1,083 feet (330 m). The dive took place near Propriano, Corsica.

 

[Superlyte27]

After a reread, I found this:

"Exley had used some of his trimix 10.5/50travel mix for the descent, but would not have consumed gas down to 500 psi on that portion of the dive. The travel mix could have been lost to free flow, but more likely Exley breathed it when the supply of trimix 6/29 was exhausted. This was a "hot" mix at 879 f/270 m,where the PO2 would be 2.9 atm; the equivalent narcosis depth was 423f/130 m, and the gas density 21 g/l, equivalent to breathing air at487 f/154 m."

So his death wasn't due to narcosis or caused by high END, but rather because he ran out of the optimal gas and decided that trying a riskier gas was better than giving up?