Passenger oxygen masks are rated to use up to what flight level?

• A. Flight level 250
• B. Flight level 200
• C. Flight level 300
• D. Flight level 350

Answer: (A)

Oxygen systems are designed to deliver breathable oxygen for a safe period during a decompression, long enough for the airplane to descend to a breathable altitude. The passenger emergency oxygen supply is sized and certified to maintain adequate oxygen up to flight level 250, which is 25,000 feet. Beyond that altitude, the fixed flow and capacity of the passenger masks aren’t sufficient to guarantee safe oxygenation for all passengers. So the rating is set at 25,000 feet to ensure the system can do its job effectively during the descent to a safer altitude.