In relation to oxygen mask deployment, which statement is true?

• A. Oxygen masks deploy only on the ground
• B. Oxygen masks deploy when the cabin loses pressurization or in certain emergency scenarios requiring supplemental oxygen
• C. Oxygen masks deploy only during routine maintenance
• D. Oxygen masks deploy to fill the cabin with breathable air

Answer: (B)

Oxygen masks are a safety feature activated when the cabin environment can’t provide enough breathable air. In normal flight the cabin is pressurized, but if the cabin pressure is lost (a rapid decompression) or there’s an emergency that requires supplemental oxygen, the masks automatically drop from the overhead panels so passengers and crew can breathe. A typical trigger is when the cabin altitude rises to about 14,000 feet, prompting the system to deploy. They’re not used on the ground, they aren’t deployed only for routine maintenance, and they aren’t meant to fill the cabin with breathable air—each mask provides a personal supply of oxygen for a short duration to allow for a safe descent or to reach breathable air conditions.