25,000 ft is the FAA's regulatory limit.
I'm saying that the re-breather mask is ineffective for anyone above a certain altitude. From what I remember during hypobaric chamber training, that altitude for a healthy, non-smoking, adult is somewhere between 30,000 and 35,000 ft.
Above 35,000 ft, using a re-breather device, like the drop down masks in the cabin, will result in blood O2 saturation levels below 70% with brain damage and death within a short period of time.
Last edited by wanabee777; 14th Mar 2016 at 20:39.