SkyDrill

Why medical oxygen is not used in aircraft

Aviation Mechanic General (AMG) practice question 20 of 26 on Ground Operations and Servicing. ACS element AM.I.F.R5 · difficulty: standard. Want to answer it in a timed quiz? Use the Aviation Mechanic General (AMG) practice mode.

Question bank updated 2026-09-22

QUESTIONA mechanic has only medical oxygen available to service an aircraft breathing oxygen system. Why is medical oxygen not acceptable?

  1. AIt contains impurities that can make the crew sick.
  2. BIts purity is too high for aircraft regulators.
  3. CIt contains water that can freeze at altitude.
Show the answer and explanation

Correct answer: C. It contains water that can freeze at altitude.

  • A — incorrect Impurities that can sicken the crew are the problem with industrial oxygen; the handbook describes medical oxygen as pure.
  • B — incorrect The handbook raises no concern about excessive purity; the issue with medical oxygen is its water content.
  • C — correct Medical oxygen, although pure, contains water that can freeze in the cold temperatures found at the altitudes where oxygen is needed.

BACKGROUND

Oxygen is commercially available in three general types: aviator's breathing, industrial, and medical. Only oxygen marked Aviator's Breathing Oxygen that meets Federal Specification BB-0-925A, Grade A, or its equivalent is to be used in aircraft breathing oxygen systems. Industrial oxygen may contain impurities that could make the pilot, crew, or passengers sick. Medical oxygen, although pure, contains water that can freeze in the cold temperatures found at the altitudes where oxygen is necessary. Only qualified and authorized persons service aircraft oxygen systems, and the highest standard of cleanliness is required because oxygen combines with oil or grease to form an explosive mixture.

STUDY TIP

Attach one defect to each non-aviation oxygen type: industrial has impurities, medical has water.

KEY POINTS

  • Use only Aviator's Breathing Oxygen meeting BB-0-925A Grade A or equivalent.
  • Industrial oxygen may contain impurities that make people sick.
  • Medical oxygen contains water that can freeze at altitude.

SOURCES

  • FAA-H-8083-30B ch01 "Oxygen Servicing Equipment"
Practice the Aviation Mechanic General (AMG) test →Timed 60-question exam, by ACS area, or review your misses. Free.
MORE ON GROUND OPERATIONS AND SERVICING

SkyDrill is not affiliated with the FAA. This is an original practice item based on FAA-H-8083-30B Aviation Maintenance Technician Handbook – General, 14 CFR part 43 and part 65. Regulations and handbooks are revised; confirm details against the current edition.