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> > Oh boy someone reinventing physiol & physics again. > > Anesthetic effect of N2 inhibiting 'feeling cold'. > Huh! > Suggest U read a bit about heat conduction before > pontificating w/ gradoise ideas. > > Simple - put your hand on a piece of metal @ rm > temp. > How does it feel? Cold - voila a concept xplained. > Apply that to HeOx, w/ its rapidly diffusing (read > heat conducting) component & that is why breathing > HeOx feels colder though net respiratory heat loss > is > actually < relative to air or nitrox breathing > Safe bubbles > Esat Atikkan > > --- Steve Hogan <Steve.Hogan@tr*.co*> wrote: > > > > 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'. > __________________________________________________ Do You Yahoo!? Talk to your friends online with Yahoo! Messenger. http://im.yahoo.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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