When must oxygen masks be removed after a decompression?

• A. Immediately after decompression
• B. When the cabin altitude is safe
• C. When the Flight Deck announces cabin altitude is safe
• D. After landing

Answer: (C)

During a decompression, oxygen masks are needed to prevent hypoxia, and you should keep them on until the crew confirms it’s safe to remove them. The key trigger is the flight deck announcing that cabin altitude is safe. They will have descended to a safe altitude, verified pressurization, and then issue clearance to remove masks. Removing them before that announcement could leave you without adequate oxygen if conditions haven’t stabilized, and waiting until after landing would miss the period when oxygen is still required. So the right behavior is to wait for the flight deck’s explicit indication that cabin altitude is safe.