Why Your Business Needs Open-Area Smoke Detection

By Xtralis, leading global provider of powerful solutions for the very early and reliable detection, remote video verification, and rapid, effective response to smoke, gas and security threats.

Open-areas spaces and buildings such as stadiums, large atria, airports and rail stations, hotels and convention centers and warehouses present unique challenges to traditional fire detection systems.

They demand a fire detection solution that is sensitive to diluted smoke but that is non-intrusive on the space. While traditional beam detectors are incredibly effective in most circumstances and can surpass spot-detector performance, in a large open-area a traditional beam detector can be easily fooled and trigger false alarms.

A classical beam detector uses two units, called a transmitter and a receiver. Inside the transmitter a light source (typically an infra-red LED) flashes periodically. Light from the LED is then focused into a tight beam by a lens, and a finely adjustable mechanism allows the beam to be directed from where the transmitter is mounted at one end of a room towards the receiver or reflector(s) at the other end.

However, traditional beam detectors are primarily difficult when it comes to alignment (the initial alignment needs to be accurate to about 0.1 degrees of movement) and are prone to false alarms triggered by objects such as banners, balloons or even birds entering the beam path, dust in the air or insects such as moths crawling on the optical surfaces of the transmitter, receiver or reflector.

These objects break the beam and set of the alarm. Normal building movement caused by temperature changes will also affect alignment and interfere with the effectiveness of the system. Simply put, in an open-area there is just more space and more chances for something to get in the way of the beam.

However, a new approach known as Open-area Smoke Imaging Detection (OSID) has been invented to help overcome the challenges of open-areas fire detection without sacrificing quality or safety.

OSID measures the extinction along a light beam caused by smoke particles along the direct path of the light beam, just like a traditional projected beam smoke detector, except that by using dual wavelengths and image processing many of the limitations of traditional smoke detection systems.

OSID uses both ultra-violet (UV) and infra-red (IR) wavelengths outside the human visible range to better identify real smoke compared to larger objects such as fork-lift trucks, insects and dust; thus reducing opportunities for false alarms.

If any actual smoke enters the beam the small particles in the smoke will reduce the UV light transmission more significantly than the IR light transmission, whereas dust & objects affect both equally.

The software can examine the strengths of these signals, and how they change over time, and make a determination of whether to raise an alarm or to flag a trouble condition.

This appropriate use of UV as well as IR light both reduces the probability of a false alarm and enhances the sensitivity to small particle smokes, which has often been relatively low on traditional optical detectors.

In fire detection the most important trade-off is the reliable detection of actual fire threats while minimizing the cost, disruption and perhaps most importantly the loss of credibility caused by false alarms. Too many false alarms lull your employees into a false sense of security and they learn to disregard the system designed to keep them save!

The life safety industry strives to improve methods to reliably and economically identify false stimuli such as dust, steam and macroscopic objects while ensuring a safe response to real threats. OSID provides all the accuracy any open-area building could need without sounding a false alarm every 10 minutes.

Xtralis will be showcasing the VESDA VLQ Aspirating Smoke Detector on stand D950 at FIREX International 2015

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