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> >The addition of 25% He to deco gases, except oxygen, has decreased the 
> reported incidences of
> >problems and discomfort that is traditionally associated with pulmonary
> >oxygen toxicity; however, this step has the potential to increase thermal
> >considerations and might extend decompression times--hence it would not be
> >recommended for "average" dives.
>
>What do you mean by "this step has the potential to increase thermal
>considerations"?
Mike,
The increase in thermal considerations is referring to the possibility of 
longer times in the water thereby exposing one's self to a greater heat 
loss through immersion and respiration.  NOTE:  This is relative to the 
chosen deco software, safety factors established, personal knowledge of 
physiology, etc.  For some people, due to varying combinations of the 
above, deco time is shorter, others it is longer.  Also note that this is 
done for much longer dives than most people will do.  Up to this point I 
have only spend 50 mins @ depth in Wakulla (approx 285) and have not had to 
do this.  Longer BT like 100+ min, at >285', might require such a step.  It 
was mentioned because it makes a difference and many varying people read 
this forum, chamber operators, sat divers, etc., perhaps others will 
benefit.  I WOULD NOT SAY THIS IS A NECESSARY STEP for most divers.

>  Do you mean that breathing helium makes you cold?
>I'm curious because the physics of the issue and practical experience
>show that breathing helium *does not* make you cold.

No, that is a very common topic though, and if I am not mistaken was just 
discussed on this forum recently.

>  Adding helium to your drysuit makes you cold, yes, but breathing it does 
> not for many of the same reasons you shouldn't put it in your drysuit.

This I agree with.  Next to He Ar is my favorite gas.
Thanks for questioning and don't hesitate to ask more.
Scott Hunsucker


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