For Part 91 General Aviation operations the required flight crew must use supplemental oxygen for any portion of the flight that exceeds 30 minutes above a cabin pressure altitude of 12,500 feet mean sea level (MSL) up to and including 14,000 feet (MSL).
For best protection, you are encouraged to use supplemental oxygen above 10,000 feet MSL. At night, because vision is particularly sensitive to diminished oxygen, a prudent rule is to use supplemental oxygen when flying above 6,000 feet MSL. So, when you fly at high altitudes, supplemental oxygen is the only solution.
These requirements are the following: 12,500 FT MSL to 14,001 FT MSL (for more than 30 minutes): Crew must be on oxygen. 14,000 FT MSL to 15,000 FT MSL: All crew must be on oxygen. Above 15,000 FT MSL: Oxygen must also be provided to passengers but they are not required to use it.
(ii) Above 15,000 feet MSL, oxygen to each occupant of the aircraft, other than the pilots, for one hour unless, at all times during flight above that altitude, the aircraft can safely descend to 15,000 feet MSL within four minutes, in which case only a 30-minute supply is required.
In aeronautics, hypoxia typically results from a decompression or lack of pressurisation of the aircraft cabin. Hypoxia occurs within a few minutes if the cabin pressure altitude rises to between 5,000-6,000 m (about 16,000 - 20,000 ft).
The only oxygen equipment allowed on an airplane is the portable oxygen concentrator (POC). If you need oxygen in flight, you must take a portable oxygen concentrator with you, and , you must let your airline know ahead of time. They may require a doctor's letter to verify the need for the POC on the plane.
Cabin Oxygen System Each container has an electrical latching mechanism that opens automatically to allow the masks to drop, if the cabin pressure altitude exceeds 14,000 ft (+250, -750 ft). Chemical generators produce the oxygen.