Fire Alarms And Smoke Detectors
Smoke detectors have become a common safety device in several public places, homes and offices. A smoke detector is an electrical device that can raise a sound alarm in case of a fire, by detecting the presence of smoke in the air. There are two types of smoke detectors, namely optical detector and ionization detector. However, due to environmental concerns, many do not prefer ionization detectors as they emit small quantities of radiation.
In fire alarms, an optical detector emits a light beam, and a photoelectric sensor is placed at right angles to the final point of the beam. When the smoke reaches inside the detector, the light beam is refracted or scattered, and as a result, is received by the photoelectric sensors. The advantage of an optical detector is that it can be used over a wide area, by placing the emitter and the receiver in a straight line. When there is any emission of smoke, the light beam gets refracted, and an insufficient quantity of the beam reaches the sensor, triggering an alarm.
An ionization detector consists of electrodes from which a current is passed constantly. When smoke enters the chamber, it absorbs the alpha particles and disrupts the flow of current, thereby triggers the alarm.