Photoelectric smoke detectors detect smoke by using a light beam and a sensor. When smoke enters the detection chamber, it scatters light, causing some of it to hit the sensor and trigger the alarm.
Here’s a more detailed explanation put together for you by Anka Security:

1. Light Source:

Photoelectric smoke detectors contain a light source, usually an LED, which emits a beam of light.

2. Detection Chamber:

This beam is directed into the detection chamber, usually at an angle to the sensor.

3. Light Scattering:

When smoke particles enter the chamber, they scatter the light in all directions.

4. Sensor Detection:

The scattered light is then detected by a photocell or light sensor in the chamber.

5. Alarm Activation:

If the amount of scattered light reaching the sensor reaches a certain threshold, the detector’s alarm activates, alerting occupants of a potential fire.

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