How Optical Smoke Alarms Work

How Optical Smoke Alarms Work

An optical smoke alarm (also called photo-electric smoke alarm) works using the light scatter principle. The alarm contains a pulsed Infra red LED which pulses a beam of light into the sensor chamber every 10 seconds to check for smoke particles.

When a fire breaks out smoke will enter the optical chamber through the opening vents. Smoke alarms from quality manufacturers have the chamber protected with insect screens to stop bugs entering and causing false alarms.

As the smoke enters the optical chamber, its particles cause the Infra red light to be scattered onto the photodiode light receptor.

Once the scattered light hits the photodiode light receptor a signal is sent to the integrated circuit which causes the alarm to sound alerting the occupants to the fire.