How do electric carbon monoxide detectors work? How does the electric carbon monoxide detector in cabin or cockpit on aircraft work?
There are three major types of carbon monoxide senors.


Biomimetic: A gel changes color when it absorbs carbon
monoxide.
Metal oxide semiconductor: When the chip's circuit detects
carbon monoxide, electrical resistance decreases, and this 
triggers an alarm.
Electrochemical: Electrodes immersed in a chemical solution
sense changes in current when they come into contact with carbon
monoxide, and this change triggers the alarm.