Will, if you mean in the absence of nitrogen ( your ccr exmample ),
maybe in a parabolic sense - it might get better and then worse ( the
"excitation" of higher ppo2's could feel like clarity ), but if you mean
with nitrogen in the mix, we have found it to be unusably narcotic in
cave diving situations. We no longer use nitrox to dive with betweeen
100-150 feet, we use trimix . We also put helium in the sitting still
deco gases, but that is for reducing damage more so than anything else,
since obviously we have real gas on our backs.

In fact, we do not even allow it in WKPP anymore based on our
experienece.

What was your ccr diluent in the example you give?

William M. Smithers wrote:
> 
> 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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