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On Fri, 30 May 1997, William E. Sadler wrote: > There were a series of tests done on divers in Hawaii in the early 80's - > they tested divers from 30' to 300' at 10' intervals. They had a slate of > analytical problems of similar difficulty - equivalent to an IQ test. > Different ones for each depth, so you could not learn the activity by rote. > Turns out that divers become noticeably narced at 100' - almost everyone > shows something at that depth. By the time divers got to 300', most > everyone was at less than 25% of their former performance. The best was > about 30%. Surprised a lot of divers. Apparently, there are a goodly > number of people who do not feel the narc. I suspect that these are the > individuals who believe that they can 'adapt' - even though they think they > can, when tested objectively they cannot. > [WARNING - I am about to argue that for the experienced diver, deep air has a minor place in diving - if this topic offends you to the point of flame eruption, spare us all and don't read any further.] Actually, it's surprising that people retained even 25% of their higher analytical skills at 300' - I don't know of anyone who won't freely admit they're narced out of their mind on air at that depth - I know I am. The 100' statistic is more surprising, not a single experienced diver I've ever met, including myself, thinks they are even minimally impaired at that depth. I'd love to take a look at that study, if you can find it. Of course, there is the issue of how well the ability to solve complex analytical problems correlates to emergency resonse capability, but that's another point entirely... > I suspect that the reason that there is as little problem as there is, is > that people who are narced seem to be able to do things that they are > trained to do even when 'under the influence' - the problem comes when > there is something new to do, or an unexpected decision to make, or the > diver is new. Then they have a problem. So for the vast majority of dives > where nothing goes wrong - you're ok. But a simple problem can be your > undoing, whereas you could solve it at a shallower depth. Right. That's why divers who expose themselves to high N2 levels should practice emergency management skills until they become an almost reflexive response. It's like martial arts - if your reaction requires higher processing than at the brain stem, then you don't stand a chance in a real combat match - and the only way to get to that level of training is practice, practice, practice. I think that too many people think that practicing emergency management skills is something you need to do just so you can get a certification, rather than looking at it as an ongoing survival skill. I won't deco dive with anybody who doesn't feel the same way. Of course, there are always events which cannot be prepared for, but proper, disciplined, regular training (and a healthy fear of dying) will cover the 95% range. When considering deep air (assuming we're past the knee-jerk objection stage here), it basically boils down to the fact that N2 does impair at depth - only an idiot would argue otherwise. So when weighing the viability of deep air for a particular dive, it pays to consider risk factors associated with impairment. For example, I would personally never even think about deep air for deep penetration or other relatively complex tasks, or for extended duration, but for bouncing to the bottom of a pinnacle in calm open water, I do, and will continue to, consider air as a viable alternative. Let's do a reality check here: raise your hand if you are a certified trimix diver and can honestly say you never went to 170' on air before getting advanced certification. Right. I thought so. So "just don't do it" is not a reasonable position, people will do it anyway, and the more we try to scare them away without providing intelligent discussion, the more they'll just want to do it - technical divers and wannabees both want to see the way cool unknown - that is why they probably got interested in tech diving, and this is a mentality that will only accept limitation when it is plainly evident that the facts cannot be ignored. *Personal* risk assessment is the name of the game, and education (formal or otherwise) is the only way to shed light on risk factors. IANTD (I can't speak for the others) knows this, and their deep air course will usually be effective is dissuading the student from thinking about doing the Andrea Doria on air. Nearly everyone walks away from that course with a healthy respect for N2. -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send list subscription requests to `techdiver-request@aquanaut.com'.
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