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An aspirating smoke detector (ASD), consists 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 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, Safe Fire Detection's ProSeries and Xtralis ASD systems.^[2]

Aspirating smoke detectors are highly sensitive, and can detect smoke before it is even visible to the human eye.

In 2010, IMS Research named Xtralis the world’s leading supplier of ASD in the fire detection market. According to the report, Xtralis accounted for more than 50 percent of the global ASD market in 2009. Xtralis manufactures both VESDA and ICAM ASDs. Both product lines provide very early warning smoke detection to continuously sample air for even the smallest traces of smoke.^[3]

History [link]

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]

In 1979, Xtralis, then IEI Pty Ltd., launched the world’s first-ever air sampling device called VESDA (Very Early Smoke Detection Apparatus). The company completely redesigned the detector in 1982 to provide the necessary reliability, features, size and reduced cost for export markets.

There are more than 1.5 million fires annually in the U.S. alone, according to the Society for Fire Protection Engineers. Fires result in an estimated $10 billion in property loss each year, the organization reports. ASD systems have gained popularity due to their ability to sense smoke long before a catastrophic incident.^[5]

Design [link]

This section requires expansion.

ASD design corrects shortcomings of conventional smoke detectors by using sampling pipe with multiple holes. The air samples are captured and filtered, removing any contaminants or dust to avoid false alarms and then processed by a centralized, highly sensitive laser detection unit. If smoke is detected, the systems alarm is triggered, and signals then are processed through centralized monitoring stations within a few seconds.^[6]

Unlike traditional passive smoke detection systems including spot detectors, ASD systems actively draw smoke to the detector. Furthermore, ASD systems incorporate various levels of integrity monitoring to ensure an alert is raised at any time the ASD’s ability to detect smoke is compromised. This is not the case with passive devices that are generally only electrically monitored with no ability to determine if smoke can actually reach the detection element.

ASD systems incorporate more than one level of alarm, generally configurable. This allows an ASD system to provide very early warning of an event, prompting investigation at the earliest smouldering stage of a fire when it is easily addressed. Other alarm levels may be configured to provide fire alarm inputs to fire systems as well as releasing suppression systems. ASD alarm sensitivities are configurable and can be programmed to levels ranging from thousands of times more sensitive than a conventional detector, to much less sensitive.

Installation and placement [link]

This section requires expansion.

ASDs are suitable for 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 gases. Often, normal point detectors will recognise the danger too late, as smoke often does not reach the ceiling quick enough for a fire to be detected in a timely fashion.^[7]

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.^[8]

High sensitivity does not mean that ASD can't be used in dusty or dirty environments as long as appropriate design, installation and maintenance processes are followed. Most ASD products can accommodate a broad range of environments and applications – from both confined and open spaces to the cleanest or dirtiest environment, including telecomm, control rooms, waste treatment, mining and more.

Statistics show that in some countries,a fire breaks out every two seconds.The consequences can be devastating-and even being well-insured is of little help.The only solution is to detect fire as early as possible so action can be taken before they spread and cause damage.

See also [link]

• Smoke detector
• Heat detector
• Carbon monoxide detector

References [link]

^[9]

External links [link]

• Three Wavelength Integrating