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JHeimann@sc*.gt*.co* writes:

> I have just set up an argon drysuit inflation system in anticipation of doing
> some trimix dives.
> 
> I am currently diving with a Viking Pro Surveyor drysuit, and use the dryhood
> that comes with the suit.  [... hood description ...]
> ...  One's head is thus surrounded by the same gas that one breathes, which
> may or may not be the same as the suit inflation gas.
> 
> My question to the net is, does anyone have experience using this type of
> dryhood in long, cold water dives with helium-based breathing mixes?  Does it
> cause one's head to freeze from the thermal conductivity of the helium, or
does
> the extra thermal protection afforded by argon suit inflation usually offset
> this?  My trimix instructor's repsonse when I asked him the question was "Hmm,
> let's try it and find out!", so I may answer my own question this week.  I
know
> I could always go back to a wethood, but I like the extra warmth and comfort
of
> the dryhood.

I dive with someone who uses this type of hood, although it is a DUI drysuit.
He is a fairly serious wreck diver (the type that de-kits to squeeze into engine
rooms) and has been diving the cold Scottish waters for a number of years and as
you might imagine has a fair bit of long deco experience. I will be in touch
with
him in the next couple of days so I'll find out if he has any experience with
this.

However, I just got a call from a commercial diving friend and I asked him about
it. Most of his diving is sat work and they use water heated suits but he has
used older dryhoods. He asked why you don't just pull the neck seal to the side
and fill the hood with argon? I don't know what the implications of this would
be
- would you trust a commercial diver? He wasn't sure if the trimix would be a
problem as he has never tried it in a hood. His final suggestion was to use a
semi-dry hood.

One suggestion he made was to flush all of the air out of the suit when you put
it on. Then fill it with argon and flush it again before going on your dive.

Alan

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