Which are the three types of oxygen described for aircraft use?

• A. Emergency, supplementary oxygen, and first aid.
• B. Regular, medical, and industrial.
• C. Portable, fixed, and ambient.
• D. Breathing, combustion, and anesthetic.

Answer: (A)

Think about oxygen in aircraft in terms of the situation it serves. Emergency oxygen is there for a sudden loss of cabin pressure to protect everyone onboard; it’s part of the automatic safety systems and provides oxygen to occupants as the aircraft descends to a breathable altitude. Supplemental oxygen covers the need to maintain adequate oxygen levels when flying at higher altitudes where the cabin is not fully breathable; it can be carried in portable bottles or installed as a fixed system and is used when people would otherwise become hypoxic. First aid oxygen is a portable supply used to treat individuals with medical need for oxygen, such as hypoxia or distress, en route to medical help, without ventilating the entire cabin.

Other options mix terms that aren’t standard categories for onboard oxygen: some refer to where the oxygen comes from (portable vs fixed) or to unrelated uses (industrial or anesthetic), or to broad applications like breathing in general. Those don’t describe the three recognized on-aircraft types.