Video Fire Detection (VFD) is a field-proven technology for detecting fires, which offers a whole range of benefits including fast and reliable response, effective protection in difficult applications such as aircraft hangars, excellent value for money and the bonus of providing CCTV images for security purposes. Andrew Bradley of Fike Safety Technology explains.
One of the most demanding environments that fire protection designers and building managers face is that of aircraft hangars. Not only do they create a very difficult technological challenge for fire detection systems, but the potential loss of high value assets or business continuity is vast. 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. Highly-flammable materials and many potential ignition sources make hangars particularly susceptible to fire. It is imperative therefore, to deploy fire protection solutions that offer reliable and very early detection capability that is cost effective to install in the very large area of hangars or cargo areas.
Unlike conventional fire detection systems, those based on VFD technology use no traditional form of smoke, heat or flame detection device. Instead, VFD 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. Incident response is also vastly improved, as the operator can view the live scene and initiate an investigation and/or intervention before the automatic extinguishing/suppression system is operated. This is an extremely important issue as quite often more damage is caused to the warehouse stock from the sprinkler water or extinguishant than the fire itself.
One of the most important benefits of VFD 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. VFD technology eliminates this problem because it is not necessary for smoke to reach the camera for it to be detected – all that’s 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.
The attractions of VFD 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 VFD. The first is to use standard CCTV cameras – which may already be in place – in conjunction with a Digital Video Recorder (DVR) and VFD 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 VFD technology is to use dedicated cameras with built-in image analysis capabilities. Such cameras are typically linked via an IP network to a Network Video Recorder (NVR) situated at a monitoring station where their images can be used for security purposes, but 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.
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 VFD technology work in practice? Fike has commissioned independent research which involved 63 tests comparing the effectiveness and speed of response of a detector using VFD technology with an air-sampling detector, a projected beam smoke detector, spot type ionisation and photoelectric smoke detectors, and a linear heat detector.
The VFD 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 slower in all but one of the tests. VFD 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.