Originally Posted By: Cindy Abbott

Here are the oxygen levels in air (as compared to at sea level) - continued:
15000 ft - 58%
21500 ft - 45% (camp 2)
23500 ft - 42% (camp 3)
26100 ft - 38% (camp 4)
29035 ft - 33% (summit)

For those who might possibly care, one can get basically these numbers using the following simple equation, which is derivable from elementary physics:
P(h) = P(0)*exp(-h/h0).
Here P is barometric pressure, h is height above sea level, P(0) = 760 Torr is barometric pressure at sea level, and h0 = 7990 m = 26200 ft.