Under what condition are occupants required to use supplemental oxygen in a civil aircraft?

Under what condition are occupants required to use supplemental oxygen in a civil aircraft?

• A. Only above 20,000 ft MSL
• B. Once above 15,000 ft MSL
• C. Only above 18,000 ft MSL
• D. No requirement

Answer: (B)

The main idea here is that as altitude increases, the air has less oxygen, which can lead to hypoxia. To prevent that, regulations require occupants to use supplemental oxygen once the cabin altitude reaches a specific mark. That threshold is 15,000 feet MSL. So, above 15,000 ft MSL, everyone on board must have access to and use supplemental oxygen. Below that altitude, there isn’t a mandatory oxygen requirement for normal operations, though pilots may choose to use oxygen for comfort or safety if needed.

The main idea here is that as altitude increases, the air has less oxygen, which can lead to hypoxia. To prevent that, regulations require occupants to use supplemental oxygen once the cabin altitude reaches a specific mark. That threshold is 15,000 feet MSL. So, above 15,000 ft MSL, everyone on board must have access to and use supplemental oxygen. Below that altitude, there isn’t a mandatory oxygen requirement for normal operations, though pilots may choose to use oxygen for comfort or safety if needed.