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Will, this effect is called "fear" - what more of these guys need - not pre hpns. It comes from the sudden realization that you are doing something very stupid, and then the environment becomes more facinating than the fear. For those who have no real insterest in being there, narcosis would be a welcome respite. We use the helium because we want to be there and we want to see it all. If I want to get high, I can do that on land. William M. Smithers wrote: > > On Fri, 20 Aug 1999 tgunther@co*.co* wrote: > > > May I assume, than, that your gas profile of choice (from shallow to deeper > > depths) would be: > > > > Nitrox -----> Trimix -------> Heliox > > Tod, HeliOx is probably the perfect gas for the extreme dives > that George and the WKPP do. That is, about 280ffw. However, > there's an effect which is currently unrecognized in the > scientific literature when diving HeliOx beyond about 250-280fsw. > > It's what a few of us call "the anti-narc", and has also been referred > to as "pre-HPNS". You feel like you've had about four cups of espresso, > and generally feel scattered as a result. > > Proper HPNS (shaking limbs, etc) doesn't set in until much deeper > (around 500-600ft), but it's not just me - several people have noticed > problems as shallow as 240. > > The simple answer (long accepted among commercial divers in dealing with > actual HPNS) is to squirt in a couple or few percent of nitrogen. This > seems to offset the effect. > > So, the answer to me, in order of descending depth, is > Nitrox-->trimix-->heliox-->trimix. That sequence factors > in gas cost, as well as efficiency. > > -Will > > -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
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