A photoelectric alarm, also called an optical or photoelectric smoke detector, is a type of fire alarm that uses a light beam and a photosensitive element to detect smoke. When smoke enters the chamber, it scatters the light, which is then detected by the photosensitive unit, triggering the alarm. Photoelectric alarms are particularly effective at detecting smoldering fires, which tend to produce more smoke and can be dangerous, especially when people are sleeping.
Detailed Explanation from Anka Security
How it works:
Photoelectric smoke detectors contain a light source (usually an LED) and a light sensor (a photodiode or phototransistor) inside the sensing chamber. The light source is angled toward the sensor so that the light doesn't usually shine directly onto the sensor. When smoke enters the chamber, it scatters the light, causing some of it to be reflected onto the sensor. The increase in light reaching the sensor triggers the alarm.
Effectiveness against smoldering fires:
Photoelectric alarms are generally more effective at detecting smoldering fires (fires that produce a lot of smoke but not much flame) than ionization alarms, which are more sensitive to fast-burning fires. Smoldering fires are more common in residential settings and can be particularly dangerous because they fill a room with smoke and toxic gases before flames show, giving people less time to escape.
Reduced False Alarms:
Photoelectric alarms are also known for producing fewer false alarms than ionization alarms, which can be triggered by, for example, cooking fumes or steam.
Interconnected Systems:
Photoelectric alarms are often designed to be part of an interconnected system, meaning that when one alarm detects smoke, all the alarms in the system will sound, providing early warning for larger homes or buildings.
Installation and Maintenance:
Photoelectric smoke detectors should be installed in bedrooms, hallways, and living spaces. They should be tested regularly (monthly is recommended) and the batteries replaced according to the manufacturer's instructions. Keeping the detectors clean is also important to prevent dust and debris from interfering with the sensors.