From: mayne@phi.cs.fsu.edu (William Mayne)
Subject: Re: Human bodies explode in vacuum?
Reply-To: mayne@cs.fsu.edu
Organization: Florida State University Computer Science Department
Date: Tue, 17 Nov 92 19:36:10 GMT

In article <1992Nov17.153453.7235@digi.lonestar.org> lvogt@digi.lonestar.org (Lee Vogt) writes:
>In article <1992Nov16.145038.23449@geac.com> adb@geac.com (Anthony DeBoer) writes:
>
>>There are other problems, like oxygen toxicity, carbon dioxide buildup,
>>hypothermia, breathing difficulty due to increased gas density, etc.,
>>that also rear their ugly heads as you start getting really really deep,
>>although your PADI course wouldn't have mentioned these in any great
>>detail, if at all, since they're generally not factors yet at the 130'
>>they warned you never to exceed.

Has anyone here experienced breathing difficulty due to increased gas
density? I don't doubt that it can happen at extreme depths, though
replacing nitrogen and oxygen with helium as you need to do anyway
coincidentally reduces gas density. I have never experienced any
depth related difficulty in breathing, though I've been quite a bit
deeper than 130 feet on air. I have remembered to pay attention, too.
At what depth does this happen?

>Actually, all of these problems you mention were discussed in some detail.

Then either your idea of what constitutes "some detail" is different than
mine or your PADI course was much better than mine. When I took open water
narcosis was covered in a few sentences and the other topics mentioned
even less, if at all. On the other hand if you stay within PADI limits
it is easy to argue that such knowledge isn't very important.

>If I'm not mistaken, the 130' limit applies to ALL recreational SCUBA diving,
>as going deeper than that requires *planned* decompression stops, at which
>point it's no longer recreational, but professional, diving.

I disagree with the use of the word "professional" here. Nobody pays me
to dive. I know lots of cave and a few wreck divers who do technical diving
but aren't in any sense professional divers. Staged decompression certainly
takes some additional knowledge and preparation. But it is not so difficult
or dangerous that it deserves a reputation for being macho or elite.

>  The main 
>difference is that, due to the no-decompression-stop limit, a recreational
>SCUBA-diver can surface immediately if an equipment malfunction occurs.  The

I don't think that decompression is the only or even the main reason to
be cautious about going deep. I doubt that most people could do a
successful free ascent from 130 feet in case of total air loss, starting
without a fresh breath. At least it would be risky. Also air supply goes
quickly at depth and I'm told that some people actually don't have it
together well enough to monitor their time, depth, and air supply.

The 130 foot limit is rather arbitrary. The Navy established that because
the bottom time on a no-deco dive to 130 is so short that anything deeper
would be useless for their purposes. They wanted divers to spend some time
working, not just bounce down to take a look. Sport diving agencies just
followed suit.

Bill Mayne
Newsgroups: alt.folklore.science,sci.misc,rec.arts.startrek.tech,rec.scuba