Definition
A condition in which carbon monoxide (CO) — a colorless, odorless, tasteless gas produced by incomplete combustion of fuel — is inhaled and binds to hemoglobin in the blood, blocking oxygen from being carried to the body's tissues. In aviation, it most commonly results from exhaust gases leaking into the cabin through a cracked or corroded exhaust shroud used by the cabin heating system. Symptoms include headache, drowsiness, dizziness, blurred vision, and impaired judgment, progressing to unconsciousness and death if exposure continues.
Plain English
It happens when exhaust fumes leak into the cabin and the pilot breathes in a poisonous gas that stops the blood from carrying oxygen. The pilot may feel sleepy, dizzy, or get a headache without realizing why, and can pass out if they don't get fresh air.
Context Anchor
Seen in discussions of exhaust heating systems, cabin heat use, and pilot health hazards during flight.
Derivation
Carbon monoxide is named from 'carbon' (the element) and 'monoxide,' meaning a compound with one oxygen atom (mono- = one, from Greek). The name itself signals that it is one oxygen short of carbon dioxide (CO2), the harmless gas you exhale — and that one missing oxygen is what makes it toxic, because the molecule grabs onto hemoglobin where oxygen should go.
Why Pilots Care
Incapacitation from carbon monoxide can lead to loss of control or an off-airport landing with little warning.
Grounding Statement
If cabin heat is on and exhaust gas leaks into the heated air, the cockpit can fill with a dangerous gas even though nothing looks or smells wrong.
Intuition Check
Do not assume carbon monoxide poisoning will smell like exhaust or smoke. Carbon monoxide itself has no odor, so symptoms or a detector may be the first warning.
Example Sentence 1
After noticing a headache and slight dizziness on a winter flight with the cabin heat on, the pilot suspected carbon monoxide poisoning, shut off the heat, opened the fresh air vents, and diverted to the nearest airport.
Example Sentence 2
A working carbon monoxide detector provides an early alert before symptoms of carbon monoxide poisoning appear.