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Aircraft systems and instrumentsQuestion 638 of 934

Which statement about carbon monoxide in exhaust gases is correct?

  1. It has no odor or color and is very hard to detect
  2. It has a strong smell that warns the pilot
  3. It is harmless in small amounts at altitude
  4. It is lighter than air and leaves through the vents
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Correct answer: It has no odor or color and is very hard to detect

To make sure exhaust gases are expelled correctly, the exhaust system must be in good condition and free of cracks.

Source: Pilot's Handbook of Aeronautical Knowledge (FAA-H-8083-25C), Chapter 7: Aircraft Systems — Exhaust Systems, page 178

Practice aircraft systems and instruments

Questions last reviewed: 18 October 2026