AIM Text
- Carbon monoxide is a colorless, odorless, and tasteless gas contained in exhaust fumes. When breathed even in minute quantities over a period of time, it can significantly reduce the ability of the blood to carry oxygen. Consequently, effects of hypoxia occur.
- Most heaters in light aircraft work by air flowing over the manifold. Use of these heaters while exhaust fumes are escaping through manifold cracks and seals is responsible every year for several nonfatal and fatal aircraft accidents from carbon monoxide poisoning.
- A pilot who detects the odor of exhaust or experiences symptoms of headache, drowsiness, or dizziness while using the heater should suspect carbon monoxide poisoning, and immediately shut off the heater and open air vents. If symptoms are severe or continue after landing, medical treatment should be sought.
Source: FAA Aeronautical Information Manual · current edition · paragraph 8-1-4.
Research Notes
AIM 8-1-4 covers Carbon Monoxide (CO) Poisoning — odorless, deadly gas that can leak into the cabin.
Source: Aircraft cabin heaters, exhaust system leaks. Cabin heat passes through a heater muff over the exhaust — a crack or leak admits CO into the cabin.
Why deadly: CO binds to hemoglobin 200-300 times more strongly than oxygen. Once bound, the hemoglobin cannot carry oxygen. Even low CO concentrations cause progressive impairment.
Symptoms: Headache, dizziness, drowsiness, nausea. Progresses to confusion, loss of consciousness, death.
Detection: CO detectors (chemical strip type or electronic). Required in some aircraft, recommended in all. Modern electronic detectors alert at 35-50 ppm.
Response: Turn off cabin heat. Open vents/windows for ventilation. Land at nearest airport. Get medical attention.