About Smoke Detectors

Function

• The smoke detector is a device that identifies smoke in a given area. If smoke is detected, a loud alarm sounds to warn people of smoke and fire. Flashing lights oftentimes accompany the auditory alarm. Most detectors are cased in plastic and are installed into the ceiling or on walls in large open areas. Advanced smoke detectors can even alert the local fire department of a possible fire.

History of

• Fernando J. Dibble and Francis Robbins Upton invented the automatic electric fire alarm in 1890. For the next 70 years, only large buildings used smoke detectors because they were expensive and were cumbersome to install and repair. Part of the problem these initial units faced was their need of a constant power supply--much like a light bulb.

Evolution

• Duane D. Pearsall introduced the world's first home smoke detector in 1967. These units were much more practical because they were easy to install and could be powered by batteries. The first household smoke detectors were sensitive to changes in the air's ionization--caused by large amounts of smoke. Over time, companies developed sensors that detect photoelectric disturbances.

Type

• Smoke alarms with optical detectors use light sensors to discern between a safe environment and one filled with smoke. The infrared LED light shines through a lens toward a photoelectric sensor. Smoke disrupts the light, causing an alarm. Ionization detectors use americium 241. This element produces radiation that moves through an ionization chamber. A safe environment permits a consistent pulse of radiation between the detector's electrodes. Smoke will naturally absorb the americium's alpha particles and cause a disruption in the pulse, setting off the alarm. New models, like the VESDA detectors, are air-sampling detectors. These locate smoke particles with a sensitive optical device. These high-sensitivity smoke detectors are recommended as the best smoke alarms for houses.

Benefits

• It is estimated that smoke detectors save more than 10,000 lives each year around the world. Especially in large buildings, early detection can be the difference between a complete evacuation and a disaster. In addition to saving lives, smoke detectors can also lower insurance premiums on homeowners' insurance, renters' insurance and building insurance.