What I don't understand about this question is that the flight deck crew only get 15 mins supply and the pax get 30 mins. This would mean that the flight deck crew are liable to be unconscious long before the pax(assuming smoke in the aircraft). I would have thought that these values should have been the other way around. Also I would have thought that when the crew bottle pressure fell below a set figure the pax bottle would give priority to the crew. After all, the pax stand a better chance of survival if the crew are alert and able to land the aircraft!
CC