Optical Smoke Detectors : New Technology Fire Alarm System

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The optical smoke detector includes a light source like incandescent bulb or infrared LED, a lens throws light into a beam, and a photodiode or other photoelectric sensor.

An optical detector can be related to a light sensor. When an optical detector is being used like a smoke detector the following aspects are included:

1. A light source such as an incandescent bulb or an infrared LED is used.
2. A lens that throws light into a beam
3. A photodiode or other photoelectric sensor placed at an angle to a beam

Where there is no smoke the light tends to pass in front of the detector in a straight line. As soon as the smoke enters the optical chamber and crosses the path of the light beam the light gets scattered due to the smoke particles. This gets directed at the sensor and it triggers off the alarm.

These detectors are visible in the auditorium or gymnasium. They are installed to detect the projected beam. A beam is sent out by the unit installed in the wall. This beam is being received back by the receiver or it is reflected back through the mirror. An alarm signal is sent to the fire alarm control panel as soon as the beam gets less visible to the sensor’s ‘eye’.

The optical smoke detectors can detect particulate or the smoke that is being generated by the cool, smoky smoldering fires. Certain tests have indicated that these detectors detect particulates or smoke about 30 seconds later from the flaming hot fires than the ionization smoke detectors.

The optical smoke detectors are not so sensitive to false alarms arising out of the steam or cooking fumes that are generated from the kitchen. Or to steam that arises from the bathroom. For this purpose the ionization smoke alarms are more sensitive. That’s why they are also called “toast proof” smoke alarms.