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> >> I'm confused... again. What is Heliair? Air, which is basically 2 >> gasses. Helium, 1 more gas. Sounds like trimix to me. A friend of >> mine who did quite a few dives with the late Mr. Exley, tells me how >> Sheck use to say, "you should use Heliair instead of trimix." Why you >> ask? He said it was "more natural." Huh? What? Please explain.... > >I'm not sure what the deal with "more natural" is. Given Sheck's >experience with high levels of narcosis I suspect he meant that the >specific subtlties of narcosis experienced on "heliair" more closely >correspond to those experienced on air at comparable EADs, than the >narcotic effects of other trimixes. But that's an entirely different topic... > Sheck's primary argument (during my training sessions) for using Heliair was that it is easy to analyse. If you mix two known gas mix, you only need to analyze one gas. In the present situation, analyzing O2 allows to determine the amount of helium and also the amount of nitrogen. On the other hand, if you mix O2, Air and Helium, according to him, analyzing the O2 content before the dive would reveal little about the N2 and the He content. Therefore, you would not know with what Trimix you dive. To have a proper analysis, it would be required to analyze either the N2 or the He content (leaving only one gas to determine by calculation). BTW, Heliair is a specific type of Trimix just as Air is a specific Nitrox. Michel Therrien m.therrien@ne*.qc*.ca*
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