Fire Safety - That looks like smoke...05 April 2005

By observing the behaviour of smoke as it rises, a vision system can give early warning of a fire developing, long before it becomes serious. It is especially useful in large areas, such as big factories and aircraft hangars, and where there is a layer of hot air, ordinarily just underneath the roof, blanketing sensors.

The D-Tec Video Smoke Detector is a suite of software, running on an industrial PC, which interprets the behaviour of moving objects on video images from surveillance systems.

Intelligent Security, from which D-Tec is spun out, was one of the pioneers of motion detection for civilian security. The technique was invented in about 1950 for military purposes, and declassified in about 1960. One of the company's systems in a nuclear power station detected some smoke and triggered an alarm. The operators then paid for the development of a system for use in turbine halls which would respond only to smoke.

The algorithms which are used to solve this problem analyse the motion of moving groups of pixels in real time. Smoke behaves differently from other moving objects because it pulsates as it builds up and develops 'fingers' along its edges. The code is completely stable and reliable, but D-Tec's engineers can still tweak settings at customer locations to cope with unexpected problems. Sales manager Mike Bell tells Plant Engineer that "98% of the time it is not necessary to visit the main parts of the algorithm," but occasionally it is necessary to cope with unusual circumstances, such as the behaviour of trees on open sites: in windy conditions these can sometimes behave in a similar manner to smoke.

Nonetheless, the system is at last beginning to be accepted by industry as the solution of choice for large areas. Recent uses have been at the Athens Olympics, where it was used to observe the forest and scrubland surrounding the site of the rowing events, and in the spiralling light wells in London's 30 St Mary Axe (alias The Gherkin) which provide natural ventilation. Other recent sales include oilfields in Azerbaijan, London Underground's Stratford Market Depot and road tunnels in Italy.

The latest development is FireVu, an Internet Protocol system that only uses bandwidth when there is an alarm, when it sends an image. The system analyses up to 25 frames per second and is provided with 1.2TB of hard disk storage, allowing archiving of about a month's data. Technology exists to send stored images to the Fire Brigade or a mobile phone, and to allow operators to wind back through images to see just when and where a fire started. This is both useful during the incident - when it can be used to direct firefighters to the seat of a problem - and after the event.

The technology won the company a Queen's Award for Enterprise in the Innovation category in 2003, and is the basis of a British Standard, BS 5839 Part 1 2002, Visual Smoke Detection. The firm is based in High Wycombe. The company's FireVu video fire detection system is the latest in a series of video fire surveillance system analysis techniques. It can be made to work with other technologies such as: vehicle incident detection, number plate recognition, and facial recognition. At present, Bell recommends that because of the amount of number crunching required, each function needs to be undertaken on a separate processing unit, although they can all be run on the same original video stream. www.dtec-fire.com

SOE

Related Websites
www.dtec-fire.com

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