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Re: [Phys-L] under pressure



On 4/13/2014 12:36 PM, Anthony Lapinski wrote:
...is the air inside pressurized so they have enough oxygen to breathe
for a long time?

Both the pressure and composition are controlled.

Every 3 meters of water depth adds 1 bar of external pressure.
Pressurizing the capsule allows minimizes the pressure differential
and allows the craft to go deeper.

Both nitrogen and oxygen become problematic with increasing pressure.
Oxygen becomes toxic at a partial pressure of ~1.5 bar (7 bar air).
Nitrogen narcosis begins at a partial pressure of ~2 bar (2.5 bar
air). Deep divers and hyperbaric chambers use gases other than
nitrogen to prevent nitrogen narcosis and vary the amount of oxygen to
limit the oxygen partial pressure to less than 1 bar. Only helium and
neon have lower narcotic properties than nitrogen and are the
preferred diving gases.

Dr. Roy Jensen
(==========)-----------------------------------------¤
Lecturer, Chemistry
E5-33F, University of Alberta
780.248.1808