When do passenger oxygen masks deploy?

• A. 14,000 feet cabin altitude
• B. 12,000 feet
• C. 15,000 feet
• D. 16,000 feet

Answer: (A)

Passenger oxygen masks deploy automatically when the cabin altitude reaches about 14,000 feet. This threshold is chosen because, as the cabin loses pressurization, the air inside becomes dangerous to breathe, so masks are released to supply oxygen right away. The deployment is triggered by a cabin altitude sensor, not the aircraft’s external altitude, and the oxygen supply typically lasts about 12–15 minutes to give the descent time to a safer altitude. Other numbers don’t match the standard deployment trigger used in most commercial aircraft.