Re: Misc. Questions

[email removed] writes:
> If the room is filled not with air, but with Oxygen only: - what
> atmospheric pressure should it be at to be safe? I believe that if
> the pressure is too high the atmosphere promotes any sort of minor
> spark into a serious fire/explosive hazard.

Humans are used to breathing area that is 80% N2, 20% O2. The air
pressure they breathe it at is 14.7 lbs/in^2. The partial pressure of O2
is about 0.20 * 14.7 lbs/in^2, or about 2.9 lbs/in^2. This is the
theoretical minimum air pressure that humans can sustain while still
being able to get adequate oxygen supply to their cells. The practical
minimum air pressure, however, tends to be higher than this -- for one
thing, altitude sickness may set in at this low a pressure (bodily
fluids filling up the lungs). Also, pure O2 is only wise for short
periods as it tends to oxidize the linings of one's lungs. I believe
that astronaut's space suits have them running about at 4-5 lbs/in^2,
and the cabins of early space craft at around 6-7 lbs/in^2.

I think the shuttle uses a O2/N2 mix that approximates earth atmosphere
at sea level. All that inert N2 adds a lot of weight but makes the
astronauts much more comfortable.

James