Cub Driver wrote:

On 10 Mar 2004 21:12:59 -0800, (WaltBJ) wrote:

Rule of thumb - O2 over 10,000 feet.

It used to amuse me, in the days before the Eisenhower Tunnel, that
the highway over Loveland Pass in CO took the driver above the
altitude at which the USAF wanted pilots to use oxygen masks.

At Aspen of course we skied all winter at above 11,000 feet. (At
Loveland, the parking lot was higher than that.) Do you suppose that's
why ski bums are famously so unstable?

The difference being the rate at which you ascend from lower altitudes,
although the military's 10,000 foot rule seems very conservativ. IIRR,
even the FAA allows pilots to fly between 12,500 and 14,000 ft. for 1/2 an
hour without O2, and pax can do it indefinitely. Pity the poor fighter
pilots in WW1, who used to climb up to 17-20,000 feet without O2 and
patrol there for an hour or so in open, unheated cockpits. And suffered
massive headaches as a result.

Guy