Smoke detectors appear in homes, mounted on ceilings and walls. These devices maintain a steady presence, operating around the clock.
Inside each unit, the air sampling process runs continuously. Small amounts of surrounding air enter a sensing chamber without pause. The chamber examines this air flow moment by moment.
This examination repeats in an unbroken sequence. Air moves in, passes through the chamber, and moves out, only for fresh air to follow immediately. The cycle sustains itself through a constant power supply.
The process operates independently of any observation or interaction. It persists through days and nights, unaffected by presence in the room or activity nearby.
The smoke detector exists as a system upheld by this ongoing air sampling activity.