I'm not a specialist, but if you find yourself in a chamber, you may not
have successfully decompressed when you came up. A poorly trained chamber
operator can make things worse or kill you regardless of what you were
breathing. I think that addresses the original issue that the "Master Diver"
confused with some sort of fact.

In the water, inappropriate gas switches (those made without adequate
decompression with the previous mix) can result in the formation of bubbles
through a process called counterdiffusion. The same can happen in a chamber
and if the mix breathed in the chamber doesn't match that of the chamber
atmosphere, counterdiffusion can occur through the skin.

Hope this helps.

> -----Original Message-----
> From: Alain Tésio [mailto:alain@on*.or*]
> Sent: Friday, April 20, 2001 6:13 AM
> To: Techlist
> Subject: Re: RE: Counter diffusion
>
>
> Is there a real hyperbaric specialist who can back me up ?
> I'm bored to read always the same replies for wkpp
> guys who are full of themselves and shout louder.
>
>
>
> --------------------------- Contents of original message
> --------------------------
>
> Subject: RE: Counter diffusion
> Date: Fri Apr 20, 2001 04:53 AM
> From: Trey <trey@ne*.co*>
>
>
> > 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'.
> >
> > --
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>
>
>
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