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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.
This pattern, which is also used for smoke alarms, is named the Temporal-Three alarm signal, often referred to as "T-3" or "Code-3" (ISO 8201 and ANSI/ASA S3.41 Temporal Pattern) and produces an interrupted four count (three half second pulses, followed by a one and one half second pause, repeated for a minimum of 180 seconds).
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.
On September 4, 1992, BRK recalled all hardwired smoke alarms under the series 1839I and 2839I due to testing programs determining that corrosion could form on the alarm horn's electrical contacts, causing the piezo to fail to make any noise. [6] In May 2006, First Alert combination smoke alarms were recalled due to draining batteries rapidly. [7]
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.
False alarms can be caused by other hot surfaces and background thermal radiation in the area. Water on the detector's lens will greatly reduce the accuracy of the detector, as will exposure to direct sunlight. A special frequency range is 4.3 to 4.4 μm. This is a resonance frequency of CO 2.