Mailing List Archive Mailing List Archive
> 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... "Heliair" is a simple way to say "trimix gas mixtures with oxygen-to-nitrogen ratios of about 1:4". "Poor man's trimix" is another way of saying the same thing. The term refers to a specific set of trimixes that are essentially combinations of air and helium. The point I was trying to make in the message you quoted is that, if you use a trimix where the oxygen-to-nitrogen ratio exceeds 1:4 (e.g., 46% helium, 14% oxygen, 40% nitrogen), then you may be in for more narcosis than you bargain for if you only consider the nitrogen as a contributor to narcosis. Calculated the "old way", this mix would give you an EAD (equivalent air depth, a term used to relate predicted narcosis experienced while breathing trimix to a similar level of narcosis experienced while breathing air) of 132 feet when breathed at a depth of 300 feet. When you take into account the narcotic effect of oxygen, you would actually feel the narcotic equivalent of an air dive to about 145 feet. Doesn't seem like much difference, does it? But that's only if you believe that oxygen and nitrogen are equipotent for narcosis. If you believe what my experiences have taught me, then I predict on the trimix defined above at 300 feet, you would feel like you're at 160 or 170 feet on air. Now it starts to matter.... Aloha, Rich Richard Pyle deepreef@bi*.bi*.ha*.or* ******************************************************************* "WHATEVER happens to you when you willingly go underwater is COMPLETELY and ENTIRELY your own responsibility! If you cannot accept this responsibility, stay out of the water!" *******************************************************************
Navigate by Author:
[Previous]
[Next]
[Author Search Index]
Navigate by Subject:
[Previous]
[Next]
[Subject Search Index]
[Send Reply] [Send Message with New Topic]
[Search Selection] [Mailing List Home] [Home]