SkyDrill

Carbon dioxide exposure hazard to the mechanic

Aviation Mechanic Airframe (AMA) practice question 3 of 9 on Airframe Fire Protection Systems. ACS element AM.II.M.R1 · difficulty: standard. Want to answer it in a timed quiz? Use the Aviation Mechanic Airframe (AMA) practice mode.

Question bank updated 2026-09-22

QUESTIONWhy must a mechanic avoid breathing carbon dioxide in fire extinguishing concentrations while working in a closed compartment?

  1. AIt is severely toxic even in very small amounts.
  2. BIt leaves a corrosive residue that damages the airway lining.
  3. CIt can cause unconsciousness and death by suffocation.
Show the answer and explanation

Correct answer: C. It can cause unconsciousness and death by suffocation.

  • A — incorrect The hazard is displacement of oxygen rather than severe toxicity; the agent itself is described as only mildly toxic.
  • B — incorrect Carbon dioxide does not react with most substances and is noncombustible; the discharge hazard is the atmosphere it creates, not a corrosive residue.
  • C — correct Carbon dioxide is considered only mildly toxic, but breathing it in fire extinguishing concentrations for 20 to 30 minutes can cause unconsciousness and death by suffocation.

BACKGROUND

Carbon dioxide extinguishes fire mainly by diluting the air and reducing its oxygen content so combustion is no longer supported. Because the gas is about one and a half times as heavy as air, it settles over burning surfaces and maintains a smothering atmosphere, which is exactly why it is dangerous to a person in the same enclosed space. The handbook notes that carbon dioxide is only mildly toxic, yet breathing it at extinguishing concentrations for 20 to 30 minutes can cause unconsciousness and death by suffocation. A discharge also produces severe cooling, with the remaining liquid chilled to about minus 110 degrees Fahrenheit and forming dry ice snow. The handbook also lists carbon dioxide as not recommended for hand-held extinguishers intended for internal aircraft use.

STUDY TIP

For agent safety questions, separate toxicity from asphyxiation; carbon dioxide harms by displacing oxygen in a confined space, not by poisoning.

KEY POINTS

  • Carbon dioxide extinguishes by reducing the oxygen content of the air.
  • Breathing it at extinguishing concentrations for 20 to 30 minutes can be fatal.
  • It is heavier than air, so it settles and lingers in enclosed spaces.

SOURCES

  • sources/ama-airframe/ch17.txt "Inert Cold Gases"
  • sources/ama-airframe/ch17.txt "Extinguisher Types"
Practice the Aviation Mechanic Airframe (AMA) test →Timed 100-question exam, by ACS area, or review your misses. Free.
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.