RE: [PSUBS-MAILIST] Viewport Question.

["Jon Wallace" <jon@psubs.org>]

Hi Dan,

Great discussion, and I think Jay's idea of coming up with a "standard" by
continuing to talk about this is a very good idea.  A couple of things come
to my mind based upon the scenario you present.  The first is that there
needs to be some consideration of CO2 effects.  You can pump in all the air
you want assuming you can deal with the internal pressure, but if the CO2
reaches a critical partial pressure no amount of fresh air is going to help
you.  Assuming you are stuck for a long time, you really would need to have
a scrubber to take care of CO2.  I continue to believe that our scrubber
project to adapt micropore products for personal subs is the best way to
bring a quality CO2 solution to the psubs market.  It's possible that if the
air exchange of taking in fresh air and dumping the stale air is efficient
enough, then CO2 build-up might be contained enough to survive the ordeal.
But that would require some testing to determine how feasible a solution it
really is.

Have you talked with your dive club about using oxygen instead of air.  At
least this would help reduce the effects of internal pressure if they could
feed it in at a reasonable rate since you would metabolize the oxygen and
not have other elements taking up space in the cabin.

Lastly, you would have to be careful with the increased pressure in the
cabin and the partial pressure of O2 as they were pumping air into the sub.
As barometric pressure increases in the cabin, a large increase in PPO2
could kill you (oxygen poisoning).

All in all, I agree with your philosophy that if all else is lost it
probably can't hurt to have some external means of trying to keep you alive,
even if there were subsequent side effects when you were finally rescued.  I
think what we need to do is analyze all the alternatives and determine the
best set of parameters that will provide the best results.  This is
definately a worthwhile project and it would be great if you, Jay, and
anyone else interested in this issue could build a team and come back with a
proposal that we issue as an RFP, and subsequently add to our Standards and
Guidelines.

Regarding the type of fitting, Jay makes some good points about the tire
valve.  However, the Coast Guard must be able to guide us on what type of
valve would be effective.  If commercial vessels have standardized and are
using them, why can't we?  Then it would just be a matter of working with
your local divers to ensure they have the adapters that will be needed in
the event of an emergency.

Jon



-----Original Message-----
From: owner-personal_submersibles@psubs.org
[mailto:owner-personal_submersibles@psubs.org]On Behalf Of Dan. H.
Sent: Sunday, January 06, 2008 1:22 PM
To: personal_submersibles@psubs.org
Subject: Re: [PSUBS-MAILIST] Viewport Question.


Jay,

The rescuers suggestion of an air inlet was more to offer some additional
time to be submerged, in case of entanglement or what ever.  The team
already has a setup to inject air in a tire valve type fitting.  I may be
wrong in my thinking ,but wouldn't newly injected air dilute the stale air
in a stranded sub?  Even better, if the person in the sub was conscious,
they could breath directly from the inlet and exhale in the sub.

I know it would increase the internal pressure unless the stale air was
pumped out, but increasing the internal pressure may be the least of your
worries if your trapped inside for a while.

The way my sub is set up now, I could receive air through my snorkel inlet,
but I would have to be conscious to open the valve inside the sub.  The
rescuers could unscrew the external float valve and screw on an adaptor with
a tire valve in it. Then once I open the internal snorkel valve, the air
would come through.

Am I correct?
Dan H.





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