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You guys should try diving the stuff instead offering up opinion without experience. The fallacy is that helium makes one lose heat is just that, a fallacy. The reference is that most people go from diving air (or NTX) with its inherent narcotic (and anesthetic) properties and are lulled into thinking that helium makes them feel colder. What is really happening is with the air and NTX dives, the anesthetic effect of the nitrogen masks the cold feeling that people diving with a decent amount of helium will "sense". They are no colder, just able to sense more because those diving with helium are more alert. Try a dive using a NTX (or air) mix first, then do the same dive again using mix. Use the proper thermal protection (none of this wetsuit stuff so one gets chilled and artificailly throws off the results) Then try it again in the other order. Steve > -----Original Message----- > From: Brian Greenberg [mailto:grnbrg@cc*.UM*.CA*] > Sent: Tuesday, March 14, 2000 9:43 AM > To: mjblackmd@ya*.co* > Cc: techdiver@aquanaut.com > Subject: Re: Helium > > > Michael J. Black writes: > > Ben Wiseley wrote: > > > I read somewhere that you needed the narcotic properties > of nitrogen > > > to off-set some effect of helium... (snip) But for > recreational divers > > > would heliox be preferred (assuming money was no object)? > In other > > > words... if money didn't matter at all would diving to 60 feet on > > > heliox be safer than air? > > > > The disadvantages of helium include increased conductive heat loss, > > Not true. Helium is indeed more conductive than nitrogen, > which is why > it should not be used as a suit gas. However, conductive > heat loss through > the lungs is actually less with helium, as the heat capacity > of helium > is lower than nitrogen. In fact, a given volume of HE will > absorb about > 70% of the heat than an equivalent volume of N2, so net > effect is that > HE mixes may feel cooler, but in fact bleed off less heat > than nitrogen mixes. > > Cp (HE) -- 20.786 Joules / Kelvin Mole > Cp (N2) -- 29.12 Joules / Kelvin Mole > > CAVEAT: While I've done the math, I've never actually done a > mix dive. Yet. > :) > > Brian. > (Armchair diving at it's best.) > -- > grnbrg@cc*.um*.ca* > -- > Send mail for the `techdiver' mailing list to > `techdiver@aquanaut.com'. > Send subscribe/unsubscribe requests to > `techdiver-request@aquanaut.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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