How does a fire alarm detect smoke?

Answer 1

Smoke detectors work in several ways.

A point to point smoke detector detects smoke when the beam projected by the transmitter is obscured in a measurable way and detected by the receiver.

A photoelectric detector sees smoke particles inside the detection chamber of the smoke detector because light inside the chamber is scattered in a measurable way.

An ionization smoke detector detects smoke because the smoke particles change the 'charge' on the detection plate inside the smoke detector.

Answer 2

There are numerous ways to electronically detect smoke.

Among the most reliable means:

• Movement of charged particles forms a current, and the change in current can be interpreted as "smoke".
• Heavy smoke is opaque and can disrupt a light beam either inside a small detector or stretched all the way around a room, using mirrors and lasers.

There are also many ways to detect the heat associated with a fire.

Answer 3

Smoke detectors work by deflect the light from smoke particles onto the photoelectric cell, thus generating a current and triggering the alarm.