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Smoke detectors

Smoke detectors are devices that are used to help in detecting smoke and preventing fires. They are installed in commercial buildings, factories, hotels and homes. These devices will normally be connected to an alarm system which will be triggered when smoke or fire is detected. Most smoke detectors will operate using photoelectric sensing or by ionizing detection. Some smoke detectors will use both for increased sensitivity.

A photoelectric smoke detector uses optical detection. It has an LED light source and a light sensor. Under normal conditions, the light from the LED will travel in front of the light sensor in a straight line. However, when smoke is present, the light from the LED will be scattered, and this will be detected by the light sensor, triggering the alarm.

Ionizing smoke detectors are able to detect smoke particles that are very small and cannot be seen by the naked eye. It has Americium-241 radioactive isotopes and 2 electrodes. Under normal conditions, the radiation will permit a small current to pass in between the electrodes. However, when smoke is present between the electrodes, the ionization is reduced and the fire alarm triggered. Although ionizing smoke detectors are cheaper than photoelectric smoke detectors, they are more prone to nuisance triggers.