İpek Yavuz KONAK

on 04 December 2017

Detectors are one of the fundamental components of a fire detection system. They detect fire in the first seconds of incident and send fire alarm signal to the control panel. Detector types vary depending on which indication of fire they detect and the detection principle.

Fire has three main indications: Smoke, heat and flame. Smoke detectors are classified as optical smoke detector, ionized smoke detector and beam type smoke detector. Optical smoke detectors are the most frequently used smoke detectors. They are used in residences, hospitals, hotels, shopping malls etc. They are secret heroes who save us from devastating damages of fire.

Let’s talk about how optical smoke detectors work

First of all, we should examine the structure of an optical smoke detector. It has Infrared LED, photodiode light receptor in an optical chamber.

Optical smoke detector’s detection is based on light-scattering principle. In normal state, IR LED emits Infrared light beams. There is a barrier in optical chamber that prevents IR lights from reaching photodiode.

In case of fire, smoke particles get into optical chamber of smoke detector. IR lights coming from IR LED refracts and scatters onto the photodiode. When scattered IR light beams reach photodiode, optical smoke detector sends fire alarm signal to fire alarm control panel.

Since detection principle of optical smoke detectors is based on light-scattering of particles in optical chamber, smoke detectors should not be used in places where there is vapour, dust and exhaust fumes in order to prevent false alarms.