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Peter van Reeuwijk wrote:
>
> Hi list,
>
> As far as the discussion went during my advanced nitrox course,
> it is not the oxygen that is going to kill you at that ppO2, but the fact
> that the convulsions resulting from that ppO2
> will likely get your reg out of your mouth, resulting in drowning.
> ppO2 = 3 ATA is used during hyperbaric treatments, if I listened careful
> enough.
> It won't kill you. The convulsions won't be something to look forward to,
> but you won't drown, since you are not in the water !
>
> > The point is that this is not a gas that one should keep
> > in reserve to breath at a depth greater than 80'.  Since
> > O2 Tox is related to PPO2, Time, and a whole host of
> > other factors one cannot say if one will tox with this
> > mix at 45m, but *I* certainly won't try it - that is
> > unless my only other chance is death.  Remember - a long
> > time ago a PPO2 of 3 ATA was the accepted limit - then
> > it went down to 2 ATA, now the (almost universally)
> > accepted limit for the working part of a dive is 1.4 PPO2
> > (1.6 PPO2 for deco).
> >
> > Carl
> >
> Peter van Reeuwijk
 
Peter,
 
You are essentially correct - it is loss of regulator and
subsequent drowning that kills you.
 
I believe that there is a period of limp unconsciousness
that occurs after the convulsion and it is this time during
which the regulator is often dropped out of the mouth.
I'm sure someone will correct me if I'm wrong.  But at this
point the discussion is academic.
 
You are correct though - a convulsion in a chamber is
not life threatening like it is underwater.  Remember
too, though, that people appear to have a much greater
ability to withstand a higher PPO2 in a chamber than
when in the water.  I think that Richard Pyle was once
subjected to something like 6 or 7 ATA Pure O2 in a
chamber (by accident).
 
In addition, there is an attendant loss of bouyancy control
(that's obvious, right?), so if you are slightly negative
you will be sinking, if you are slightly positive, you will
be rising.
 
Carl