Smoke detectors are required in areas which cannot be kept under constant physical surveillance. The areas protected with smoke detectors are the lavatories, cargo holds, crew rest areas and electronic avionics bays. Two types of systems are generally used - optical detection or ionising chemical process. In order to draw the pilot's attention for immediate action, most smoke detection systems illuminated red warning lights in the flight deck.

Note: Engines and APU employ heat based fire detectors and not smoke detectors.