Originally Posted by
freespeed2
It is relevant since 100% O2 still will not supply the O2 at sufficient pressure to assist breathing. 'Normal' is a mix of O2 and cabin air, '100%' is all O2, 'EMER' is O2 forced out of the mask under pressure to inflate the lungs at high altitude.
It is not a matter of the percentage quantity of O2 being delivered. It is the fact that the lungs cannot inflate to inhale the O2 with the reduced partial pressure at that altitude. I've flown GIV for 10 years. It has the standard 'modern jet' crew mask.
Your comment highlights my point about the masks that was pointed out to us during the course; most pilots think 100% will prevent hypoxia at high altitude. It won't.
It will at airline/GA altitudes.
100% O2 will supply sufficient pressure for a fit human to remain usefully conscious at high commercial levels as explained from a tech point of view elsewhere. Positive pressure breathing is only used on military high alt aircraft (and Concorde). The continuous pressure system on a commercial jet is NOT a positive pressure breathing system which also requires specialist training to use. If you are under the impression that your biz jet system is a positive pressure set then please consult your tech manual. Urgently.