Originally Posted by
OldnGrounded
Time of useful consciousness at FL400: 15-20 seconds. Probably less than that for me, with significant heart disease in my old age.
Emergency descent from FL400 to 10,000 ft: A lot longer.
Probably good to note that the "detectable injuries" to pax with non-functioning masks would likely range from significant permanent brain damage to death. Always important to consider when establishing risk factors.
Not a medic but I think the critical part is from 400 to 300 , at 4000 ft/min (typical emergency descent on most types) say 2- 3 min deprivation ; like a long underwater scuba dive ., brain damage ?
But from 30.000ft you get back a bit of oxygen , there are lots of people that climb the Himalayas without oxygen and they do not suffer brain damage.
But again I am not a brain specialist..
I just remember a decompression on a Spantax DC8 over the Netherlands from FL33 or 370 where half the O2 masks did bot deploy because stuck by nicotine tar .. Diverted to AMS. .. Nobody was injured, shocked yes, but most of the pax continued a few hours later to the Canaries...