1.0 Introduction On Smoke Detector
A smoke detector is a device that detects smoke, typically as an indicator of fire. Commercial, industrial an 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 disk shaped plastic enclosure about 150 millimetres (6in) in diameter and 25 millimeters (1 in) thick, but the shape can vary by manufacturer or product line. Most smoke detectors work either by optical detection (photo electric) or by physical process (ionization), while others use both detection methods to increase sensitivity to smoke.
Smoke detector in large commercial, industrial and residential buildings are usually powered by a central fire alarm system, which is energized by a power with a battery back up. However, in many single family detached and smaller multiple family housings, a smoke alarm is often powered only by a single disposable battery. Some smoke alarms use a carbon dioxide sensor or carbon monoxide sensor in order to detect extremely dangerous products of combustion.
Commercial smoke detectors are either conventional or analogue addressable and are wired up to security monitoring systems or fire Alarm Control Panels (FACP). These are the most common type of detector and usually cost a lot more than a household smoke alarm. They exist in most commercial and industrial facilities such as high rises, ships and trains. Conventional smoke are so called because they are the older type of smoke detectors.
The detector communicates with the fire alarm control panel simply by changing state from high impedance to low impedance when smoke is detected. Smoke detectors are typically wired together up to 40 detectors on each zone of loop and a single fire alarm control panel can usually monitor a number of zones or loops which can be arranged to correspond to different areas of a building. in the event of fire, the fire alarm control panel is able to identify which loop contains the detectors or detectors in alarm but its not able to identify which individual detector or detectors is in an alarm state.
Large, wide area indoor spaces present a challenge to traditional fire safety systems in order to effectively detect smoke over such a space, complex networks of multiple overlapping sensors will be required. Optical beam smoke detectors on the other hand are designed exactly for such situations — one single unit installed on a wall can detect smoke over an area of up to 1500m2 or 19800 sq ft. More coverage per detector means fewer detectors, with associated reductions to the time and cost of installation and wiring as well as lesser aesthetic intrusion.
There is already a lively debate about the relative merits and drawbacks of different detection systems. A common theme is that bean detector may not be as reliable or trouble free as other methods, however this is almost always to in correct installation.
Beams in fact, can be much more suitable for some situations than other detection systems, and this article will explain how to get the best from beams.
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