Evolution of Air Sampling Smoke Detection
Author: Mike Clouthier
Let’s start at the beginning: In 1970, the Australian Commonwealth Scientific and Industrial Research Organization (CSIRO) used a nephelometer to carry out research into forest fires. The Australian Postmaster-General's Department (APO) then engaged the CSIRO to investigate technologies that could prevent service interruption due to fire. After selecting a sample site to carry out the needed research, 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 HVAC system, utilizing a chart-recorder output display.
At the conclusion of several weeks of testing, it was discovered that there was no commercially available fire detection technology suitable for preventing damage to telephone equipment. One technology that did show great promise however was the nephelometer itself.
In 1979, Xtralis, then IEI Pty Ltd. Of Australia, produced and sold an air sampling device they called VESDA (Very Early Smoke Detection Apparatus). The company redesigned the detector in 1982 to provide the reliability, features, size and reduced cost for export markets. ASD systems have gained popularity due to their ability to sense smoke long before a catastrophic incident.
Aspirated or Air Sampling Smoke Detection (ASD) is an active smoke detection system which uses an aspirator, fan or pump to draw in air through a network of pipes or tubes to detect smoke. The air samplings 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 are then processed through centralized monitoring stations within a few seconds.
Unlike passive smoke detection systems, including conventional smoke, flame and heat detectors, ASD systems actively draw smoke into the detector. ASD systems incorporate integrity monitoring to ensure a fault 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 reach the detection element.
Active Detection and Cumulative Sampling
Early on, for all the benefits of ASD over passive detection, it was cost prohibitive. Applications where ASD was used usually were restricted to Data Centres, Computer Rooms, Clean Rooms or Archive buildings. The cost of what was being protected usually warranted and justified the cost of ASD. Today, that cost differential has changed dramatically and, in many cases, ASD is more economical than conventional heat or smoke detection. That change came about due to technological advances, more aggressive supply management and productivity advancements.
ASD can now be used in a variety of vertical markets: Airports, Automotive, Banking, Education, Energy, Oil and gas, Finance, Government, Healthcare, Hospitality, Institutional, Manufacturing, Residential, Retail, Telecommunications, Transportation to name a few. As technology increased, so did the amount of square footage that an ASD detector could cover. This led to the ability to cover larger space, such as, warehouses and convention centres.
With the introduction of Flair Detection Technology and cumulative sampling, ASD detectors can now offer increased sensitivity – ranging from 0.0015 to 6% obscuration per square foot, up to 15 times greater over older ASD detectors, at least 3X better dust rejection, up to twice the longevity and up to 40% greater coverage in high airflow environments while maintaining consistent sensitivity over time.
Communication upgrades provide flexible networking and programming capabilities that reduce installation, commissioning, monitoring, and maintenance costs through extensive connectivity options and remote diagnostics tools.
New models of ASD can provide addressability with supervision with full microbore tube and system integrity monitoring including individual tube blockage, breakage, tube - sample point cleaning, and system leakage provides assured detection.
Aspirated gas detectors that connect to an ASD pipe networks can now detect flammable, toxic and oxygen gas hazards. Toxic chemical gases, such as, carbon monoxide, hydrogen sulphide, nitrogen dioxide, ammonia, etc can be detected. Oxygen depletion can be measured in hospitals. Off-gas events from lithium- ion batteries can be monitored and detected early.
With exciting innovations on the horizon; development of the ability to determine the type of smoke that is being produced through particulate analytics, advanced addressability, the ability to use an Aspirated smoke detector to determine the presence of airborne virus particles and many more, the ASD future looks to becoming more mainstream than ever before.
Xtralis by Honeywell