Okay. According to you, "Time of useful consciousness at 35,000 feet is about 20 seconds." You can fly the plane down to where there's oxygen in 2 to 3 minutes -- which is between 6 and 9 times longer that the period of "useful consciousness" (whatever that is). And how long does it take for oxygen deprivation to result in permanent dain bramage
I'm no medical expert, but I don't think 10 minutes exposure to the pressure at 35,000 feet is enough time to deprive someone of oxygen to the extent that brain damage will occur. My best guess is that a person will pass out, which will cause a lower respiration and heart rate. I believe that this lower rate will allow a person to survive "a long time" without supplemental O2. I base this guess on the fact that many people have climbed Everest without using supplemental O2. Granted, they are in excellent physical condition at the start, and they have many days to acclimate to the higher altitude, but they are still strongly exerting themselves at high altitude. So, based on the irrefutable scientific proof (
![grin =D](http://www.armedpolitesociety.com/Smileys/default/grin.gif)
), I think most everyone can survive for 10 minutes at 39,000 feet.
In any case, the plane should be rapidly descending. Even at a cabin altitude of 25,000, there should be enough pressure to get the oxygen into your blood.
Hawkmoon, flight crews are by regulation supposed to have oxygen supplies for any flight above (Fly320s- is it 12,500 feet? It's been a while.)
Yes, basically, but it applies to the cabin pressure altitude. I am not required to use O2 during normal operations except under certain conditions. The cabin pressure in the A320 never exceeds 8,000.