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A major problem associated with the use of helium is body heat loss, which is caused in part by the fact that the thermal conductivity of helium is approximately six times that of air. Helium has a higher thermal conductivity than nitrogen, but because of its lower density has less thermal capacity; its thermal properties make it unfavorable in cases where it is used inside a diving suit. Helium is a very poor insulator. Mixtures containing helium feel colder for the diver to breathe, but because helium is a lighter gas with less thermal capacity, breathing a helium mixture may actually remove less heat from the diver than an equivalent nitrogen-based mixture. It has been determined that in order to avoid hypothermia breathing gas has to be heated for divers working at depths deeper than, say, 500 fsw (150 msw). This well-established effect suggests that helium is the major cause of the heat loss, but in fact it is not possible to breathe air at these depths at all, so helium gets the blame by default. Heat loss in the breathing gas relies on a combination of both heat capacity and conductivity, but definitive research to partition the relative importance of these two effects in breathing gas heat loss has not yet been done. At 09:49 PM 9/28/1998 -0700, John Walker wrote: >> Oops, He chill factor. I don't thnk so unless U R using it in suit >> (now tht qualifies as dumb). >> >> Once again: Heliox does not increase respiratory heat loss. >> Yes Joel that is a fact. > > > Esat, try diving. Their is tooo a chill factor even when you use a >light He mix. I have noticed this while switching back to mix for my >breaks on O2 usually within 1 minute. Its very noticable and you can >see for yourself once you put down the tech books and go diving. > > John >-- >Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. >Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'. > Joel D. Silverstein Scuba Training + Travel Co. http://www.NitroxDiver.com -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
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