Thanks for the link, Simon. Interesting information.
Time of Useful Consciousness
Altitude TOUC
(feet)
15,000 30 minutes or more
18,000 20-30 minutes
22,000 5-10 minutes
25,000 3-5 minutes
28,000 2.5-3 minutes
30,000 1-3 minutes
35,000 30-60 seconds
40,000 15-20 seconds
45,000 9-15 seconds
50,000 6-9 seconds