Pressure regulation

[SFreihof <SFreihof@aol.com>]

In your mail you asked: 
> Also to the people building dry subs, how do you regulate the fresh air
supply >and internal pressure? I've spent many sleepless nights thinking about
it (it's >better than counting sheep) and have come up with a way to do it but
I probably >just re-invented the wheel.

My understanding is that you merely replace O-2  consumed, since CO-2 produced
is absorbed by the scrubber (lithium hydroxide, e.g.).  There is no net
increase in pressure, and I assume you need only to keep the partial pressure
(i.e. percentage) of oxygen within certain limits.  Also, it is wise to
monitor the percentage of CO-2.

I'm not sure you can do this simply with a sensitive demand type regulator,
because I would expect the hull flex at depth to increase the total pressure
in the cabin above 1 atm.  I would think you must monitor % 0xygen.

I am sure there are ways of doing this automatically and maybe some components
of scuba type rebreather system could be used.  These systems are now
commercially available, but probably expensive.

I'm curious what method you devised?  Please share your design ideas, unless
you intend to patent, of course.

Who out there can offer some guidance?

Stan Freihofer