(b) The oxygen system must be free from hazards in itself, in its method of operation, and its effect upon other components.
(c) There must be a means to allow the crew to readily determine, during the flight, the quantity of oxygen available in each source of supply.
(d) Each required flight crewmember must be provided with—
(1) Demand oxygen equipment if the airplane is to be certificated for operation above 25,000 feet.
(2) Pressure demand oxygen equipment if the airplane is to be certificated for operation above 40,000 feet.
(e) There must be a means, readily available to the crew in flight, to turn on and to shut off the oxygen supply at the high pressure source. This shutoff requirement does not apply to chemical oxygen generators.
[Amdt. 23–9, 35 FR 6386, Apr. 21, 1970, as amended by Amdt. 23–43, 58 FR 18978, Apr. 9, 1993]