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Primer – VESDA Systems

Facilities Management comes with a suite of impressive acronyms, but few have the straightforward charm of VESDA, or Very Early Smoke Detection Apparatus. This system is used primarily in data centres and other environments where fire or contamination would pose a mission-critical threat.


The idea of using air quality as a measure of fire risk was borne of a series of experiments carried out by the CSIRO right here in Australia in the 70’s. The agency was tasked with using a nephelometer to investigate the causes of forest fires. A nephelometer is an instrument that uses light to detect the concentration of particulates suspended in air (or other media). In this context, the nephelometer was identified as an ASD (Aspirating Smoke Detector).


Irish company Xtralis was the first to take the idea of an ASD and make it into a commercial product in 1979. VESDA remains a trademark of Xtralis, but has also become shorthand for any number of similar systems offered by competitors.


A VESDA system is made up of a series of pipes with very fine holes, which are placed in the target environment to take in air for constant sampling. The air is filtered back into a device that is basically a nephelometer, in that it examines the sample for the presence of smoke. As VESDA systems have become more sophisticated, several additional layers of protection have been added. For instance, if the VESDA cannot detect air coming through, it will alarm.

This is contrasted with conventional smoke detectors, which will only respond to the presence of smoke that has had the time to rise to the detectors, and thermal sensors which will detect the heat from a fire. Both of these systems rely on a fire to already be combusted to trigger the alarm, which would be far too late in a data centre or other environment laden with sensitive electronic devices, like some labs. VESDA systems are also deployed in environments where highly combustible goods are stored, such as petroleum storage facilities and some weapons batteries.


The most common issue for facilities managers and other personnel who have VESDA systems in their portfolio is that they’re simply too good. Many contracts rely on VESDA apparatus to be set at a high level of sensitivity, which leads to many false positives that can interrupt your day, or worse- trigger expensive responses like fire suppression or brigade calls. 

It’s important that your fire engineers create a realistic specification for the deployment of VESDA -when correctly calibrated, VESDA systems can be useful in environments where you wouldn’t expect, including accommodation, where they may be used to allow for quick response to bad odors. It’s an expensive way of doing it, but it can be done.


Where to buy

Almost any fire systems team can supply, install and maintain a VESDA or general ASD system. Wormald and Honeywell are two major suppliers of complete installation and maintenance programs.

Regulation and Maintenance

VESDA maintenance is governed by Australian Standards 1603 and 1670. The best practice for maintenance will vary depending on the deployment, but the basic requirements are:


1.       Check detector and filter: hardware dependent, refer to manufacturer recommendation

2.       Check Power Supply: 6 months

3.       Inspect pipe Network: 6 months

4.       Check air flow to each pipe: Every visit, including reactive maintenance calls. Otherwise monthly

5.       Perform System Integrity Smoke Test: 12 months

6.       Clean Sampling Points: 24 months

7.       Flush Pipe Network: 24 months


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