Smoke detectors are devices which sense the smoke and give the signal to the fire control panel. There are of two type, Photoelectric Detectors and Ionization Detectors.
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Photoelectric Detectors
> The Optical Smoke Or Photoelectric Type Smoke Detector, uses a light source to detect smoke.
> The Infra-Red LED is a lens that shoots a beam over a large area.
> If smoke is present in the room, it enters the optical chamber, having smoke particles scatter and sensor sets of the alarm.
> In very large areas where a smoke detector is placed, there are two optical detectors that send the straight line of infra-red beam from a sender to a receiver.
> Optical Smoke Detectors are less sensitive to false alarm fire, such as minor smoke from candles, cooking, steam etc.
Ionization Detectors
> Ionization smoke detectors detect smoke even it is too small to naked eye
> It is a best and cheap alternative for Photoelectric detector
> Through alpha radiation, the ionization smoke detector passes through the air-filled space container allowing flow of electrons.
> However if any smoke gets inside the chamber and absorbs the alpha particles, it lowers the level of ionization, hurting the flow of electrodes, thus setting off the alarm.
> More commonly placed in accommodation areas.