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On Sun, 22 Aug 1999, Joel Markwell wrote:
> 
> Unless there is some new info that someone on here has (which I'd love to
> see), the general assumption is that Nitrox does not reduce narcosis, though
> it isn't definitive. Divers subjectively report both, that it's MORE and
> that it's LESS narcotic.

No, no new info, but I'll definitely report in on the LESS side.
There is absolutely no doubt in my mind that at relatively
low PO2's, O2 is less narcotic than N2.  This is easy to
verify on a CCR.  You go down to say 130ft, and breathe the
PO2 down to around .4.  Then jack it up to 1.6.  Voila - in
two minutes, your head is noticeably clearer.   

Note that in terms of breathing air (assuming O2 is non-narcotic)
0.4 is and EAD of 156ft, while 1.6 is an EAD of 105ft.  And
that's exactly what it feels like when you do the exercise.

Yes, different people report different things, which amazes
me, because the difference is so immediately noticeable.
Perhaps the issue is that the difference in ambient PO2
of air at narcotic depths (like 130), isn't all that
dramatically different from a safe nitrox at the same depth.
You need a rebreather to get a low swing like 0.4 (or you
need to partially fill your OC tank with pure nitrogen).

At any rate, the issue is kindof silly anyway, if you think
about it.  The difference in calculated END between considering
O2 narcotic or not narcotic is fairly small for air and nitrox, 
and once you cross over into trimix depths, it's particularly 
irrelevant.

-Will


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