Aspirating smoke detector
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An aspirating smoke detector (ASD), consists of a central detection unit which sucks air through a network of pipes to detect smoke. [1] The sampling chamber is based on a nephelometer that is capable of detecting the presence of smoke particles suspended in air by detecting the light scattered by them in the chamber.
In most cases aspirating smoke detectors require a fan unit to draw in a representative sample of air from the protected area through its network of pipes, such as is the case for Wagner and Xtralis ASD systems. [2]
Aspirating smoke detectors are highly sensitive, and can detect smoke before it is even visible to the human eye. They are not recommended for use in unstable environments due to the wide range of particle sizes that are detected. This does not mean they can't be used in dusty/dirty environments, as long as the levels of aerosol remain stable. [3]
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[edit] History
In 1970 the Australian Commonwealth Scientific and Industrial Research Organisation (CSIRO) used a nephelometer to carry out research into forest fires. Subsequently, the Australian Postmaster-General's Department (Later becoming Australia Post and Telstra) engaged the CSIRO to investigate technologies that could prevent service interruption due to fire.
After selecting a sample site to carry out research, the CSIRO suggested that the nephelometer should be used as the benchmark for the APO fire tests. This was installed to monitor smoke levels within the return-air ducts of the mechanical ventilation system, utilising a chart-recorder output display.
At the conclusion of several weeks of testing, it was discovered that there was not one commercially-available fire detection technology suitable for preventing major damage to telephone equipment. One technology that did show great promise however was the nephelometer itself. [4]
[edit] Design
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[edit] Installation and placement
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ASDs are suitable for stable environments where a highly sensitive rapid smoke detection capability is required. This makes them suitable in clean rooms; areas which contain goods easily damaged by fire, such as tobacco, electronic rooms and highly flammable liquid and gasses. Often, normal point detectors will recognise the danger too later, as smoke often does not reach the ceiling quick enough for a fire to be detected in a timely fashion. [5]
As they can be easily hidden, pipe networks are suitable in environments where point detectors can be considered aesthetically displeasing, such as offices, apartments and hotel rooms. This factor also makes them suitable in locations where point detectors can be easily tampered with, such as in correctional facilities. [6]
[edit] See also
[edit] References
- ^ "Aspirating Smoke Detectors (ASD)". Siemens. http://www.buildingtechnologies.siemens.com/products_systems/fire_safety/fire_safety_products/special_detection/aspirating_smoke_detectors_asd.htm. Retrieved on 2009-05-11.
- ^ "VESDA Systems". Fire Security Services. http://www.firesecurity.co.nz/vesda.html. Retrieved on 2009-05-11.
- ^ "Advantages of Air Sampling Smoke Detection Systems". Wagner. http://www.wagner.de/fire-detection/operation/disadvantages-of-point-type-detectors/index.html?L=2. Retrieved on 2009-05-11.
- ^ "The HISTORY of VESDA and MONITAIR". Cole Innovation & Design. http://www.coleindesign.com/products_article.html. Retrieved on 2009-05-11.
- ^ "VESDA: Clean Rooms". xtralis. http://xtralis.com/file.cfm?id=452. Retrieved on 2009-05-11.
- ^ "VESDA: Correctional Facilities". xtralis. http://xtralis.com/file.cfm?id=445. Retrieved on 2009-05-11.
