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Trey, the previous posts on that matter do not contradict your statement, if we pay a closer look. When you switch to a ligter gas, e.g. to He-mix it will take some time for the "old" mix/gas to get replaced by the new one. In that time you load your tissues with more inert gas, the remaining old gas an the fast ingoing new one. But these switches happen on the way down. Normaly one does not get bend on the descend (at least to my knowledge, which is very limited). On the ascend you would either stay on He-mixes or switch to Nitrox or O2. That means He leaves your tissues quite fast and N2 is diffusing in your tissues rather slowly, no problem. So the whole issue is no issue at all. At least to my understanding. I just can not see how that would affect treatment in a hyperbaric chamber? I suppose the main issue with He-hits would be the very fast diffusion of He and the resulting severe bends. So their may be special time frames and recompression pressures in chambers for treatment of He-accidents. I is not clear to me why one should not breath Nitrox after a He hit. I can think of on explanation. Lets say you are bend on Trimix, on the way to the chamber you breath Nitrox (certainly you would breath O2 instead!). So you outgas He fast, take in N2 slowly. In the chamber you get recompressed and they may treat you with a He-mix. But you loaded your body with N2 from the Nitrox, a slow gas. So for a little time while starting to breath the He-mix your inertgas load consists of N2 (which is still not fully gone) and the fast He. Maybe this higher load can cause trouble? Again a non issue as you would try to breath O2 instead of Nitrox on the way to the chamber. I hope this will never happen to one of us. I hope I did not mix this up. Regards, Jens. Trey wrote: > > Total and complete bullshit. This is the stupidest thing I have read on here > in years. Partial pressures are not going to create bubbles, only absolute > differentials. Otherwise we would all get bent going to oxygen, right? You > obviously do not dive, do you. > > This is a fairy tale used to explain why misfits get bent. It is total and > complete bullshit. We in WKPP do dives involving five gas changes and the > fastest deco from saturation on the planet, and nobody gets bent in any > fashion. > > If this horseshit were even close to true, we would not be using deco gases, > now would we. > > -----Original Message----- > From: Alain Tésio [mailto:alain@on*.or*] > Sent: Thursday, April 19, 2001 6:38 PM > To: scottk@nw*.co*; Techlist > Subject: Re: Counter diffusion > > Counter diffusion occurs when switching gases, the common > picture is "isobaric counter diffusion" because bubbles > appear though you don't change the depth, which can't happen > in theory with no gas change : > when you change from nitrox to heliox, as helium diffuses > faster than nitrogen gases out, for some time the total > partial pressure of inert gases will increase which can > mean bubbles. > > It isn't something which is absolutely required to know > for tech diving, at least if you follow the common > procedures and don't play the random gas wizard, but it's > a must for hyperbaric specialists. > > They know how to deal with decompression illness with gases > other than air, at least in Europe when professional divers > use heliox for 30 years, however it may be a problem > in areas having experience only with recreational > diving. > > If there is one thing to remember, it is that you shouldn't > breath nitrox when you go to the chamber after of a > trimix accident. > > The other way is ok though, it's essentially a specialist > affair, but using heliox 50 for air accident is ok. > > Alain > > ----- Original Message ----- > From: "Scott" <scottk@nw*.co*> > To: "Techlist" <techdiver@aquanaut.com> > Cc: "Trey" <trey@ne*.co*> > Sent: Thursday, April 19, 2001 6:38 PM > Subject: Counter diffusion > > > George, > > > > Can you put the issues of "counter diffusion" into language a Jarhead can > > understand? > > > > I was accosted this past week by a "Master Diver" who warned us that "If > you > > have to take a chamber ride after breathing that shit (helium) it will > kill > > you." > > > > I was so stunned by his position and attitude that I just nodded and > > listened. > > > > Plus, I have no idea what counter diffusion is, or if or why it is an > issue > > to SCUBA divers. > > > > Scott > > > > -- > > 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'. > > -- > 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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