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There is smoke without fire
A COMPANY claims to have developed a new fire-detection system that is the first in the world to use the images from video cameras to detect smoke by analyzing its particular patterns.
The company, D-Tec (formerly known as Intelligent Security, based near London), has been awarded a Queen’s Award for Enterprise in recognition of its development of systems for detecting fire in otherwise difficult-to-protect industrial areas.
D-Tec claims that its video smoke detection (VSD) system is designed specifically for use in big areas, such as aircraft hangers and warehouses.
The early detection of smoke in high and very large areas, or where high airflows are present (and even in external areas) has always posed a problem to fire safety professionals. Practically, it is just not possible to place detectors close enough to the area of risk to provide an effective level of fire detection.
Conventional point smoke detection placed in a normal office environment will always be close to the source of the fire and smoke will be detected quickly and effectively. Place the same detection in a voluminous area such as a warehouse and there is a high reliance on the smoke overcoming distance, stratification and temperature layering before being detected. Consequently, in this type of environment, conventional methods of smoke detection are often found to be lacking.
D-Tec maintains that, with the development of VSD technology, the economical protection of these critical areas is now a reality. The company says that, in situations ranging from power stations, historic buildings, road tunnels, rail depots, warehouses, shopping malls and aircraft hangers, VSD offers effective protection from fire. The ability to “look in” also allows for detection within hazardous or toxic areas.
VSD is based on the computer analysis of video images provided by standard closed-circuit television (CCTV) cameras. Using advanced image-processing technology and extensive detection and known false alarm phenomena algorithms, VSD automatically identifies the particular motion pattern of smoke and alerts the system operator to its presence in the shortest time possible.
By effectively detecting smoke at its source, VSD does not rely on the proximity of smoke to a detector and therefore is unconstrained by distance. Whether the camera is mounted 10 metres or 100 metres from a risk area, VSD will detect smoke in the same amount of time.
The system rapidly detects smoke by looking for small areas of change within an image. These areas of change are then passed through a series of filters that seek particular characteristics that can be associated with smoke behaviour.
VSD can process video information from up to eight cameras simultaneously. The video hardware is designed to allow simultaneous real-time digitising of all eight images and which means no information is lost or delayed. All alarm condition images are logged, time and date-stamped and stored within the system’s memory,
An example of a successful installation of the system exists at London Underground’s Stratford market maintenance depot.
After experiencing extensive false alarms with a new fire-detection system, it became necessary to re-evaluate its design and decide on possible radical modifications. The problem lay specifically with the high-level beam detectors that mainly triggered through misalignment caused by building movements, sunlight, particulate contamination and even flying pigeons.
Protection of an area of this size (190 metres long, 110m wide and 30m high) using a high-level beam detection system was initially accepted as the right design for this type and size of building. But, as the false alarm situation worsened, the system finally had to be turned off.
D-Tec was invited to find a solution to the problem and replaced the high-level beam detectors with a VSD system. This had been trialled in other areas of the London Underground network but had not been used before in this particular application.
Considering the problems, a very exacting specification was put together for the replacement system. More than 80 smoke tests were carried out to prove the effectiveness of the VSD system under various operational conditions, including the deployment of steam-cleaning machines used for cleaning the rolling stock and varying lighting conditions.
Eventually, a 24-channel VSD system was installed comprising a 24-camera system, linked by fibre-optic cable to the main operations’ room. The incorporation of VSD into Stratford market’s overall fire strategy has resulted in effective and trouble-free protection. According to D-Tec, since the installation of the VSD system, there has only been one recorded unwanted alarm and that occurred during the initial setting-up period prior to system handover.
One of D-Tec’s latest installations is in the stunning new Swiss Re building that is the headquarters of the global reinsurers. The 180-metre-high, 40-storey building has added a striking landmark to the City of London’s skyline. D-Tec’s VSD system has been fitted in the spiralling light wells on the floors being fitted out with offices and in the reception and lift area in the entrance lobby.
D-Tec believe that the VSD system has provided a technological breakthrough in fire detection and the company now plans to develop and adapt the system so that it can operate over the Internet.
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