On Monday, September 18, 2000 12:01 AM, Lee Bell wrote:

(snip)
> Because I've been taught that the first
> sign of CNS toxicity may be convulsions, which are highly likely to be
> fatal, I prefer to forgo the experience.

Lee!  That was beautifully put - and deserved to have a big smiley after it!
:-)

>N2, which I agree is more
> insidious, is something I have experienced and something I'm better able
to
> detect and adjust for before it leads me to do something deadly.  In
truth,
> I don't set a hard limit for narcosis.  Rather I monitor it's effects,
> setting the limit for each dive, during each dive.
>
> On my deepest dive to 175 fsw, I was not dangerously impaired.  I was,
> however, impaired enough that I didn't stay there long.  I've been
> sufficiently impaired to head for shallower water at 128 fsw and, on at
> least one occasion, as shallow as 90 fsw.  I may not ever reach my PPO2
> limit of 185 feet on air, and that's OK.  It's a limit, not a goal.

It's a subtle difference but one that - at a personal level and as somebody
who's susceptible to narcosis - I'd still consider high.  :-)

I still believe that the caution shown by so many in terms of PPO2 is never
balanced by a similar concern with the partial pressure of Nitrogen.

A couple of years ago there was a rebreather death on the Great Barrier
Reef.  (The victim relied on a membrane system to charge his cylinder with a
nitrox mix.  He failed to analyse the O2 content in the cylinder.  The
membrane system had pumped air rather than nitrox!!).  The Coroner suggested
a Code of Practice be implemented for "Recreational Technical Diving".  The
Draft of that Code is now out for public comment and review.

For those interested, it can be viewed at:
http://www.dtir.qld.gov.au/hs/papers/icp011.pdf

I find some of the points controversial.  Particularly the maximum partial
pressure of Nitrogen when discussing mixed gas.  (I'm not altogether certain
that I agree with the requirements for a "Supervisor" either!)  :-)

>As I
> believe I stated in my previous post. if/when I decide to dive to
> exceptlonal depths more often or to depths greater than my personal air
> limit, I'll learn to do so in a way to reduce both nitrogen and oxygen
> risks.

It continues to amaze me at just how much there is still to learn about
diving!  :-)

Strike