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
> >
> > --
> > Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'.
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> 
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