🚀 go-pugleaf

In article <1992Nov13.190025.6323@digi.lonestar.org> lvogt@digi.lonestar.org (Lee Vogt) writes:
>[Much discussion of the hows & whys of nitrogen narcosis deleted]
>
> [another poster wrote]
>>Nitrogen narcosis usually occurs at depths around 300 feet, or (at 30 ft to
>>the atm) a pressure change of ten atmospheres.
> ...
>Also, at 300 feet, the pressure would be 11 atmospheres, one atm/30 feet
>(roughly) *plus the one atm of pressure at the surface*.  Always forgot to
>add that one in myself, too...

Actually, you're both partly right.  The absolute pressure, including the
one atmosphere at the surface, is just a hair over ten atmospheres, not
eleven, since it's actually 33 feet of seawater (34 feet of fresh water)
that exerts a pressure of one atmosphere.  Nine times 33 is 297', plus
one atmosphere surface, is ten atmospheres.

The 10% error in that approximation throws the calculation by a whole
atmosphere once you get down to the 10 or 11 atmosphere range.

>I beg to differ on this point.  I recently completed a class in
>recreational SCUBA-diving (PADI program) and nitrogen narcosis was mentioned
>as typically occuring at around 100 feet, if memory serves me properly.  In
>any case, as the depth limit for recreational SCUBA is 130 ft maximum and 
>nitrogen narcosis is mentioned as a hazard in the course-book, the statement
>that 'nitrogen narcosis usually occurs ... around 300 feet' is in error.

100 feet is typical for the onset of nitrogen narcosis, although some
extremely sensitive individuals have noticed it as early as 60'.  However,
it gets worse with increased depth, so believe me, you'd be narked at
300'. :-)

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.
-- 
Anthony DeBoer       adb@geac.com | uunet!geac!adb | GEM: ANTHONY.DEBOER