Plain English Meaning
A small device in the cockpit or cabin that warns you if a poisonous gas called carbon monoxide is leaking into the air you are breathing.
Full Definition
A device installed in the cabin of an aircraft that senses the presence of carbon monoxide gas and warns the occupants before concentrations reach dangerous levels. Detectors range from simple chemical spot indicators that change color when exposed to carbon monoxide, to electronic units that produce an audible or visual alarm.
Context Anchor
Seen during preflight checks, cabin heat use, and maintenance checks of exhaust and cabin heating systems.
Derivation
Carbon monoxide is a gas made of one and one atom (mono- meaning 'one'). It is colorless, odorless, and toxic. A simply 'detects' or senses its presence, which is because a cannot see, smell, or taste it.