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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'.
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