Re: Oxygen

Date:         12 May 99 02:48:47 
From:         James Matthew Weber <>
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At 10:11 PM 4/29/99 +0000, you wrote:
>Can anyone tell me how we survive breathing oxygen above 12K in aircraft
>without oxygen masks??

There is a vast difference between oxygen requirement in a heavy
exercise situation as opposed to sitting down doing essentially nothing
in an aircraft. Human lungs are designed to support reasonably high
levels of exertion, which translates into addition capability at low
demand, just as an aircraft at low weight can fly higher than one at
MGTOW.  The net effect is that lung capacity is about 3 times what is
normally required (many people survive and live fully functional lives
after one lung has been removed as a result of cancer for instance).

That suggests that survival is possible, although exercise tolerance
would be greatly reduced, at atmospheric pressures down to at least 1/3
atmosphere (about 10 inches of mercury, or 335 millibars). 12,000 feet
under normal circumstances is about 19 inches of mercury. People
actually live at altitudes well in excess of this in South America and
in the Himalayas in the Asian Sub continent.

Altitudes in excess of 12000 feet can be a problem for people with
respiratory diseases who has greatly reduced lung function.

James Matthew Weber  1 602 315 6520   Fax 1 602 638 1316