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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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