What are Photoelectric Smoke Alarms?

Mary McMahon

Photoelectric smoke alarms are smoke alarms which use changes in a beam of light as an indicator of a fire. These sensitive smoke alarms are ideal for detecting smoldering fires which may burn slowly at low temperatures, such as mattress and furniture fires, or fires lurking underneath rugs and in drapes. A photoelectric sensor is also included in dual sensor smoke alarms, special smoke alarms which are designed to react to multiple types of fires. Many hardware stores sell photoelectric smoke alarms, and some fire safety organizations and fire departments distribute them for free as a public service.

Woman with a flower
Woman with a flower

Any type of smoke alarm should be checked at least twice a year to ensure that it is working properly. It is also a good idea to change the batteries when you check your smoke alarm; many people check their smoke alarms when the time changes, as this biannual event already requires the adjustment of other household electronics. If you aren't sure about how to check your smoke alarm, check the owner's manual or ask your fire department for help.

The inner workings of a photoelectric smoke alarm include a light emitting diode (LED) and a small sensor which is calibrated to register subtle changes in the beam of light created by the LED. Under normal conditions, the light remains clear and steady. When particles of smoke enter the air, however, the beam of light is obscured. Depending on the style of photoelectric smoke alarm, the sensor reads light which scatters as a result of smoky conditions, or it registers a sudden obscurity in the beam.

When the sensors in photoelectric smoke alarms register particulates in the air, they trigger a loud alarm which may beep, whoop, or make other obnoxious, very noticeable noises. The sound alerts the occupants of an area, indicating that they should quickly leave the area or ascertain the source of the smoke which is causing the smoke alarm to go off. In some cases, photoelectric smoke alarms may be triggered by smoky cooking, incense, or similar conditions, in which case the smoke alarm can be turned off and reset.

While photoelectric smoke alarms are a great fire safety tool, it is important to remember to keep fully charged fire extinguishers in convenient locations around the house to ensure that you can put out small fires. The best choice for a fire extinguisher is a combination fire extinguisher which can handle multiple types of fires, such as an ABC extinguisher which can put out grease fires, electrical fires, and fires caused by basic combustibles like paper products.

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