Michael, everything you wrote you' find in my post, if not that
explicitely.
Counterdiffusion has played a role in commercial diving, in chamber and
bell environments, especially with Argon as a shielding gas, and in
relation to suit filling gases, chamber gases others than the diver
breathed. If you do not know that, you know nothing'bout commercial
diving.
If you want to know more , get informed, perhaps call Dr. Faesecke in
Hamburg.
It is right, for rec tec diving it is a theoretical issue, as Bernd
Aspacher clearly has pointed out in his contributions ( though for some
this may have seemed to be between the lines only).
But even so, learning about theoretical effects can sometimes lead to
better understanding of gas physics, or decompression theory.
Practice without theory sometimes renders dumb, theory without practice
blind.

Michael Waldbrenner schrieb:
> 
> Matthias now you are killing me !
> The isobaric counterdiffusion has as much to do with diving as
> a cow with laying eggs ....
> OK, IN THEORY you might be fully saturated with Nitrogen and then breathe
> Heliox and THEN might have a problem
> when doing this ISOBAR, but only the dumbest dude would even think about
> that !
> This is soooo far beyond imagination.....
> I often argued with Bernd Aspacher about this one...this is really beyond
> reality !
> This is the same as his statements that AIR is a good Bailout-Gas for
> Technical Diving...
> 
> I really think that here we are exactly in the discussion about things some
> DO and write about it
> and some write about theory and don´t do it !
> 
> Whom would you trust for going diving ?
> 
> Michael
> 
> -----Ursprüngliche Nachricht-----
> Von: mat.voss@t-*.de* [mailto:mat.voss@t-*.de*]
> Gesendet: Freitag, 20. April 2001 13:55
> An: Trey
> Cc: Alain Tésio; scottk@nw*.co*; Techlist
> Betreff: Re: Counter diffusion
> 
> You are wrong, Trey, and Alain is right.
> I would only modify the essence to :
> If bubbles occur during a static gas change, this happens because of
> counterdiffusion, and because of a certain choice of gases, and switch
> depth.
> It can be avoided if the above conditions are not met.
> If you need know more, get in touch with Dr. Aspacher ( he wrote a
> monography on isobaric counterdiffusion, there you may find the evidence
> , and why some ( few) are affected, majority not.
> Bühlmann ( page 67-71), Lambertsen et.al., Lettnin, ( page 223) / Imbert
> proved, that the sum of partial pressures , when certain conditions are
> met, can be eqal or greater than ambient pressure.
> However, this holds mostly for chamber situations.
> 
> Horseshit physicians and PH D's, arent't they ?
> 
> Matthias
> 
> Trey schrieb:
> >
> > 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
> > >
> > > --
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> >
> > --
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> >
> > --
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