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Carbon monoxide concentration in parts per million

Aviation Mechanic Airframe (AMA) practice question 8 of 9 on Airframe Fire Protection Systems. ACS element AM.II.M.K4 · difficulty: applied. Want to answer it in a timed quiz? Use the Aviation Mechanic Airframe (AMA) practice mode.

Question bank updated 2026-09-22

QUESTIONA carbon monoxide concentration of as little as 2 parts in 10,000 may produce headache, mental dullness, and physical lethargy within a few hours. Expressed in parts per million, what concentration is that?

  1. A20 parts per million
  2. B200 parts per million
  3. C2,000 parts per million
Show the answer and explanation

Correct answer: B. 200 parts per million

  • A — incorrect This value is ten times too small and would correspond to 2 parts in 100,000.
  • B — correct Two parts in 10,000 equals 200 parts in 1,000,000, because multiplying both terms of the ratio by 100 converts it to parts per million.
  • C — incorrect This value is ten times too large and would correspond to 2 parts in 1,000.

BACKGROUND

Carbon monoxide is a colorless, odorless gas produced by incomplete combustion, and its presence in breathing air can be deadly. Detectors are most often found on reciprocating engine aircraft with exhaust shroud heaters and on aircraft with combustion heaters; turbine bleed air is tapped upstream of the combustion chamber, so it poses no carbon monoxide threat. Exceedingly small amounts are dangerous if inhaled, and prolonged exposure or higher concentrations may cause death. Chemical color-change detectors are normally tan and darken toward grey or black in the presence of the gas, with transition time inversely related to concentration. At 50 parts per million the indication appears within 15 to 30 minutes, while 100 parts per million changes the color in as little as 2 to 5 minutes.

STUDY TIP

Practice converting the handbook's ratio expressions into parts per million; multiplying a "parts in 10,000" figure by 100 is the whole trick.

KEY POINTS

  • 2 parts in 10,000 equals 200 parts per million.
  • That level can cause headache and lethargy within a few hours.
  • Color-change detectors darken faster as concentration rises.

SOURCES

  • sources/ama-airframe/ch17.txt "Carbon Monoxide Detectors"
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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.