Unlike conventional fire detection systems, those based on VID technology use no traditional form of smoke, heat or flame detection device. Instead, VID systems work by automatically analysing images from CCTV cameras, looking for tell-tale characteristics in those images that indicate the presence of smoke and/or flames.
Some of the benefits of this approach are immediately apparent. For example, the images from the cameras can be used for building security as well as for fire detection, thereby eliminating the need for a separate security CCTV installation. In addition, a single camera can cover a wide area, so fewer cameras are needed than conventional detectors to protect a given area.
One of the most important benefits of VID systems is, however, slightly less obvious. Conventional smoke detectors, which are at the heart of most fire protection systems, can only react to smoke when it actually reaches the detector. In situations such as those involving buildings with high ceilings, it can take a long time for smoke from a fire to reach the detector - indeed, in some cases, it may never do so.
In these cases, conventional smoke detectors are ineffective in providing an early fire response. VID technology eliminates this problem because it is not necessary for smoke to reach the camera for it to be detected - all that is needed is for the camera to be able to see the smoke. While it might be argued that this is also true of projected beam smoke detectors, these provide a limited area of coverage and they are often difficult to install in appropriate locations because of obstructions like light fittings and building structural members. Aspirating systems are another alternative however again coverage can be limited and installation requires sampling pipes to be fitted around the area to be covered.
Large open areas with harsh and difficult environments are another challenge for fire detection systems. Areas such as aircraft hangars are subjected to continual changes in the atmosphere as the hangar doors are opened and closed and massive airflow changes can be caused by aircraft engines (Figure 1). Highly-flammable materials and many potential ignition sources make hangars particularly susceptible to fire and therefore an ideal candidate for VID systems. As with warehouses, the financial loss to assets in the event of a fire can be significant and potentially catastrophic for a business - so a reliable fire protection system is imperative.
The attractions of VID fire protection are clear, but how does this technology actually work in practice? The first point to note is that there are two ways of implementing VID. The first is to use standard CCTV cameras - which may already be in place - in conjunction with a DVR (digital video recorder) and VID software that analyses the images from these cameras to identify fire signatures.
This approach can work well and has obvious attractions if suitable cameras are already installed, but it is important to be aware of its limitations. If, for example, the DVR or software running the image analysis crashes, the whole fire protection system becomes ineffective. Another issue is that existing cameras will not usually be wired with fire-resistant cables, which means that the system may not meet regulatory requirements.
The second way of implementing VID technology is to use dedicated cameras with built-in image analysis capabilities. Such cameras are typically linked via an IP network to an NVR (network video recorder) situated at a monitoring station where their images can be used for security purposes. Crucially they are also directly linked to a fire control panel. If the camera detects a fire, it sends an alarm signal to the panel just as a conventional detector would (Figure 2).
There is no longer a single point of failure that can disable the whole fire protection system and even if the IP network is out of action, the cameras are still able to send alarm signals to the fire control panel. Finally, because these dedicated cameras are installed with fire protection in mind, fire-resistant cabling can be used to link the camera to the fire control panel.
So much for the theory, but how well does VID technology work in practice? Fike has commissioned independent research which involved 63 tests comparing the effectiveness and speed of response of a detector using VID technology with an air-sampling detector, a projected beam smoke detector, spot type ionisation and photoelectric smoke detectors, and a linear heat detector.
The VID system detected the fire in every test and, in 61 of the 63 tests it was the first detector to do so. The only other detector to respond to all of the fires was the air-sampling unit, and this responded significantly more slowly in all but one of the tests.
VID technology is attracting a lot of interest from insurers, who see it as providing fire protection that is demonstrably superior to that provided by conventional systems
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