Point of no return on air, what is it?

[k374]

What, in your personal opinion, would be the minimum depth before you think it would be unlikely to return alive to the surface given a single AL80 with air at 3500psi at the surface. This is just for curiousity of course, I'm not planning to do my own version of Mythbusters with this data

[Wookie]

Bret Gilliam went deeper than 400 feet in Tongue of the Ocean back in the late '70's/Early '80's on a single 80 with air. Read all about it in his book Pioneer Of Diving by Brett Gilliam Dan Manion made it to 509 and back. These guys were superbly fit and acclimated to diving deep air.

[JeffG]

I'm surprised some people manage to live past 5 ft.

[NWGratefulDiver]

There is a wall a few miles from where I'm presently sitting where several people have successfully done bounce dives to beyond 200 fsw on single AL80's. However, in the past few years, two of those who attempted it didn't surface. One was found 10 months later, half buried in the silt at 205 fsw. The other one's still out there somewhere ...

... Bob (Grateful Diver)

[OldNSalty]

Seing how this is basic scuba I would just put out the rule-of -thumb that no deeper in feet then the cubic capacity of your tank so 80

but yea, obviously you can go much deeeper but I wouldn't care too.

So is 509 the answer or, if we are talking normal people, 200?

[Wookie]

Originally Posted by OldNSalty

Seing how this is basic scuba I would just put out the rule-of -thumb that no deeper in feet then the cubic capacity of your tank so 80

but yea, obviously you can go much deeeper but I wouldn't care too.

So is 509 the answer or, if we are talking normal people, 200?

I like your rule of thumb. For a diver with 0-25 dives, 80 seems deep enough.

[Cave Diver]

Originally Posted by k374

What, in your personal opinion, would be the minimum depth before you think it would be unlikely to return alive to the surface given a single AL80 with air at 3500psi at the surface. This is just for curiousity of course, I'm not planning to do my own version of Mythbusters with this data

I don't think there is any way to accurately answer this question.

There are too many variables between individual divers physiology. One may have a great SAC and make it to 250' and back with gas to spare. One may OxTox at 225'. One may have a PFO and take a DCS hit doing an ascent that is perfectly fine for another. There have been cases where diver's failed to make it back from dives of 65' or less.

[N2DeepInAz]

As a DM candidate, I'd have to tow the line and say to dive within your training and to not exceed the max depth of your training.

As for minimum depth, that would be the deepest point you've been trained to dive to, which for PADI would be 60ft for OW, 130ft for AOW.

[Gombessa]

Originally Posted by Wookie

Bret Gilliam went deeper than 400 feet in Tongue of the Ocean back in the late '70's/Early '80's on a single 80 with air. Read all about it in his book Pioneer Of Diving by Brett Gilliam Dan Manion made it to 509 and back. These guys were superbly fit and acclimated to diving deep air.

But if you dive there, beware of the wah-wah.

http://www.cisatlantic.com/trimix/AQ.../Wah-Raimo.htm

[NWGratefulDiver]

Originally Posted by OldNSalty

Seing how this is basic scuba I would just put out the rule-of -thumb that no deeper in feet then the cubic capacity of your tank so 80

That rule of thumb applies to new divers ... and for some very good reasons. More experienced divers, who have better gas consumption rates, solid skills, and knowledge of gas management can safely exceed those limits.

We have rules of thumb like that in diving to help keep new divers out of trouble. But ultimately it always boils down to using good judgment ... which one develops through experience.

... Bob (Grateful Diver)