"Robert Moore" wrote in message

Above 40,000 feet (12 km), the time of useful consciousness is 12 to
25 seconds. (The shorter figure is for a person actively moving; the
longer
figure is for a person sitting quietly.)

The number that we were always taught in the airline business was that at
39,000', the time of useful conciousness was 18 seconds.

Bob, I was taught similar numbers. I based my estimate solely on anecdotal
reference provided by two friends, each of whom had "enjoyed" a rapid
decompression at high flight level -- one at 390 and one at 410. The fellow
at 390 was out of his seat getting coffee (small galley immediately behind
the jump seats on 747 freighters) when the cabin blew. They both related
similar sensations. They went right for the masks, and had them on quickly
[estimated 2-3 seconds for the guy in his seat, and 3-4 seconds for the
coffee drinker], but each said they felt "spacey" almost immediately. A
combination of fatigue, confusion, forced exhalation, etc., left each of
them, in separate instances, with the conviction that at somewhere around 10
seconds or so they probably would have lost the mental discipline to stay
focused and get the damn mask on. I have no personal experience that would
allow me to comment on their remarks.

John Gaquin