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Smoke detector mounted on a ceiling. A smoke detector is a device that senses smoke, typically as an indicator of fire.Smoke detectors/alarms are usually housed in plastic enclosures, typically shaped like a disk about 125 millimetres (5 in) in diameter and 25 millimetres (1 in) thick, but shape and size vary.
Trouble conditions are often activated by a contaminated smoke detector or an electrical problem within the system. Trouble conditions are also activated by a zone being disabled, a circuit or NAC being disabled, low power on the backup battery, disabling of a notification appliance, ground faults, or short or open circuits. Usually the alarm ...
Automatically actuated devices can take many forms, and are intended to respond to any number of detectable physical changes associated with fire: convected thermal energy for a heat detector, products of combustion for a smoke detector, radiant energy for a flame detector, combustion gases for a fire gas detector, and operation of sprinklers ...
An aspirating smoke detector (ASD) is a system used in active fire protection, consisting of a central detection unit which draws air through a network of pipes to detect smoke. [1] The sampling chamber is based on a nephelometer that detects the presence of smoke particles suspended in air by detecting the light scattered by them in the chamber.
An optical beam smoke detector is a device that uses a projected beam of light to detect smoke across large areas, [1] typically as an indicator of fire. [2] They are used to detect fires in buildings where standard point smoke detectors would either be uneconomical [ 3 ] or restricted for use by the height of the building.
A flame detector is a sensor designed to detect and respond to the presence of a flame or fire, allowing flame detection.Responses to a detected flame depend on the installation, but can include sounding an alarm, deactivating a fuel line (such as a propane or a natural gas line), and activating a fire suppression system.
In an ionisation type smoke detector, ambient air is allowed to freely enter the ionization chamber. The chamber contains a small amount of americium-241, which is an emitter of alpha particles which produce a constant ion current. If smoke enters the detector, it disrupts this current because ions strike smoke particles and are neutralized ...
For smoke detectors according to EN 54-7 and fire detectors with smoke sensor (parts 12, 20 and 30 of EN 54) the test fires TF2, TF3, TF4 and TF5 are used. The EN 54-20 defines the following test fires with reduced fuel quantity for aspirating smoke detectors with enhanced or very high sensitivity (class A or B): TF2A and TF2B; TF3A and TF3B