Exactly how deep is "Deep Air?"

[Slamfire]

well he is on the deep air death list...
just sayin'

Even if you could magically remove all narcosis at 879ft there are still so many more highly dangerous factors that could quickly dispose of a diver at that depth. I can't come even close to comparing my diving with the kind of diving Sheck was doing. It's not even in the vicinity of what we've been discussing on this thread where the low 200's is the higher range being discussed here.

I could just as easily say David Shaw is on the deep Trimix death list... Besides being disrespectful to Shaw, it points to a deceitful implication that Trimix killed him.

 

[boulderjohn]

I could just as easily say David Shaw is on the deep Trimix death list... Besides being disrespectful to Shaw, it points to a deceitful implication that Trimix killed him.

There are at least to fallacies at play in these conversations. The single cause fallacy, and the post hoc fallacy.

Exley's book mentions only "depth blackout" as a danger in deep diving. His book does not mention PPO2, narcosis, or CO2 buildup. (I read an article not long ago which suggested that the WOB at great depths created more CO2 than it released through exhalation.)

Note that I am not taking a particular side here--I wold just like the discussion to stay accurate and logical.

 

[grf88]

Let's consider two groups of hypothetical divers. The first group have been convinced that diving with an END of greater than 100 feet is dangerous. As a result of this preconditioning they are seriously impaired at depth greater than 120 feet. The second group have received no such preconditioning but have been made aware of various techniques that can reduce the impact of narcosis. This group happily dive to 150 feet on air on a regular basis with very little difficulty. They have also been trained to recognize the onset of impairment so they can ascend when necessary.

Both groups are now regularly diving wrecks in the 100 to 150 foot range, the first group on trimix and the second group on air. The price of helium now rises to $5.00 cu.ft., don't for one minute think that is impossible in some locations it is that much and more. 50% of the first group decide that they can only afford to continue their activities by switching to a rebreather. The second group just continue what they were doing. Based on present statistics which group can be expected to have the highest fatality rate. If you believe that it is the first group you would have to conclude that to teach that using air deeper than 100 feet is dangerous is irresponsible.

 

[Blackwood]

50% of the first group decide that they can only afford to continue their activities by switching to a rebreather. The second group just continue what they were doing. Based on present statistics which group can be expected to have the highest fatality rate. If you believe that it is the first group you would have to conclude that to teach that using air deeper than 100 feet is dangerous is irresponsible.

I'm confused.

Which is "The second group"? The Deep Air group or the other 50% of the first (Trimix) group?

Either way, how does rebreather vs open circuit in any way lead to a conclusion that teaching air past 100' is dangerous?

 

[DCBC]

Let's consider two groups of hypothetical divers...

I understand where you're coming from, but the difficulty with this question is that it only considers the breathing mixture and other considerations are not factored into the equation. How about experience of these divers?

If Group 1 consisted of divers with 100 hours of experience, they were fat, out-of-shape and were breathing "Trimix" and Group 2 were ex-Navy divers with 10,000 + hours underwater, in good condition and breathing "Air," I think my money would be on Group 2 (especially if all the dives were on the Andria Doria at 220')

Does this indicate that air is safer than Trimix? No. It does indicate that there is much more involved in deep diving than the gas the diver's breathe. I think this is what some people are missing. Too much emphasis is on the mixture and not enough on how much experience a diver should have before going deep in the first-place.

When the finger is pointed at Sheck as a casualty, I can't help but shake my head. The vast majority of divers today have no idea what it takes to do a really deep dive. Some even feel superior that they have a Trimix card; big deal. I tell my students that the card in their pocket wont get them out of a problem when things go bump in the night, death isn't impressed by credentials. A level head, teamwork and your experience is the best hope. If a diver believes that Trimix is going to keep him safe, he may end up being surprised.

 

[boulderjohn]

I would have been interested in a slight variation of this poll, perhaps requiring two polls.

1. To what depth would you normally limit ENDs, assuming you have reasonable access to an appropriate mix?

2. To what depth would you be willing to dive with air, assuming you do not have reasonable access to an appropriate mix and conditions were appropriate? (Use your own definitions of reasonable access (cost / presence) appropriate conditions. In other words, after what depth you would not dive with air no matter what the situation?

 

[grf88]

I'm confused.

Which is "The second group"? The Deep Air group or the other 50% of the first (Trimix) group?

Either way, how does rebreather vs open circuit in any way lead to a conclusion that teaching air past 100' is dangerous?

The second group is the group diving air to 100-150. Not deep air in my books.

The post was really more to demonstrate that suggesting people should not be taught to dive past 100 feet except on trimix, taking no additional factors in consideration, is just plain dumb.

 

[TSandM]

That's a good revision of the question, John.

For me, below 100 feet I'd prefer helium, but in warm, clear tropical water with no overhead or deco considerations, I have gone to 130 on air.

 

[Blackwood]

The post was really more to demonstrate that suggesting people should not be taught to dive past 100 feet except on trimix, taking no additional factors in consideration, is just plain dumb.

Boy, I didn't get that at all. Thanks for clarifying.

 

[grf88]

Boy, I didn't get that at all. Thanks for clarifying.

I should have used :mooner: at the end of my post as I had originally planned.