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Halon prohibited on combustible metal fires

Aviation Mechanic Airframe (AMA) practice question 4 of 9 on Airframe Fire Protection Systems. ACS element AM.II.M.R2 · difficulty: recall. Want to answer it in a timed quiz? Use the Aviation Mechanic Airframe (AMA) practice mode.

Question bank updated 2026-09-22

QUESTIONOn which class of fire must Halon extinguishing agents not be used?

  1. AClass B, flammable liquid fires
  2. BClass D, combustible metal fires
  3. CClass C, energized electrical fires
Show the answer and explanation

Correct answer: B. Class D, combustible metal fires

  • A — incorrect Class B fires involving flammable liquids are among the fires Halons control appropriately.
  • B — correct Halons must not be used on a Class D fire because the agent may react vigorously with the burning metal.
  • C — incorrect Halons are electrically nonconducting and are appropriate for fires in energized electrical equipment.

BACKGROUND

Two Halons are used in aviation: Halon 1301, a total flooding agent, and Halon 1211, a streaming agent. They became the agents of choice because they are extremely effective per unit of weight over a wide range of conditions, leave no residue, are electrically nonconducting, and have relatively low toxicity. Halons appropriately control Class A, B, and C fires, but they must not be applied to a Class D fire involving combustible metals such as magnesium, titanium, zirconium, sodium, lithium, and potassium, since the agent may react vigorously with the burning metal. Halon production has been banned by international agreement because these agents deplete the ozone layer, although aviation has been granted an exemption. Compliant replacement agents found to date include the halocarbons HCFC Blend B, HFC-227ea, and HFC-236fa.

STUDY TIP

Fix the rule "Halons cover A, B, and C, never D" in mind, and remember that specialized dry powder is the agent reserved for burning metals.

KEY POINTS

  • Halons are appropriate for Class A, B, and C fires only.
  • Applying Halon to burning metal may cause a vigorous reaction.
  • Halon 1301 floods a zone; Halon 1211 is the streaming agent.

SOURCES

  • sources/ama-airframe/ch17.txt "Halogenated Hydrocarbons"
  • sources/ama-airframe/ch17.txt "Classes of Fires"
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MORE ON AIRFRAME FIRE PROTECTION SYSTEMS

SkyDrill is not affiliated with the FAA. This is an original practice item based on FAA-H-8083-31B Aviation Maintenance Technician Handbook – Airframe, and 14 CFR part 43. Regulations and handbooks are revised; confirm details against the current edition.