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A smoke detector is a device that detects smoke, typically as an indicator of fire.


Commercial, industrial and mass residential devices issue a signal to a fire alarm system, while household detectors, known as smoke alarms, generally issue a local audible and/or visual alarm from the detector itself.


Smoke detectors are typically housed in a disc shaped plastic enclosure about 6” (150mm) in diameter and 1” (25mm) thick but the shape can vary by manufacturer or product line.


Most smoke detectors work either by optical detection (photoelectric) or by physical (ionisation) process, while others use both detection methods to increase sensitivity to smoke.


Sensitive alarms can be used to detect, and thus deter, smoking in areas where it is banned such as toilets, schools, airplanes and pubs and restaurants.


Smoke detectors in large commercial, industrial and residential buildings are usually fired powered only by a single disposable battery.


An optical detector is a light sensor.  When used as a smoke detector, it includes a light source, a lens to collimate the light into a beam, and a photodiode or other photoelectric sensor at an angle to the beam as a light detector. 


In the absence of smoke, the light passes in front of the detector in a straight line.  When smoke particles, directing it at the sensor and thus triggering the alarm.


Also seen in large room, such as gyms or an auditorium, are devices that detect a projected beam.  A wall mounted unit sends out a beam which is either received by a separate monitoring device or reflected back via a mirror.  When the beam becomes less visible to the “eye” of the sensor, it sends an alarm signal to the fire alarm control panel.


A photoelectric smoke detection device is generally more responsive to fires that begin with a long period of smouldering.  Photoelectric alarms react slower to rapidly growing fires than ionisation alarms, but lab and field test have shown that photoelectric smoke alarms provide adequate warning for all types of fires and have been shown to be far less likely to be deactivated by occupants.

Fire & Smoke Alarms

There can be no compromise when it comes to fire safety. That’s why The Electrical Counter recommends and supply Aico smoke/heat detectors, Rafiki and ESP fire alarm systems.


Available online is a complete range of reliable and top quality fire protection systems, accompanied by smoke alarms, at excellent prices from The Electrical Counter. As well as this, we will delivery for free on orders over £90!

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