In practical use, smoke detectors "sense" smoke by detecting and reacting to particles of combustion in the air. However in some cases when the smoke detector is mounted high on the ceiling a fire can grow to a dangerous size before the sensor activates. A relatively new technology called Video Image Smoke Detection (VISD) uses cameras in conjunction with software to actually see the smoke in extremely early stages, rather than waiting for it to arrive full force.
NFPA 72 first placed the installation and maintenance requirements for Video Image Smoke Detection (VISD) in its 2007 edition. While the 2010 rules are unchanged, the equipment has continued to improve. In case you haven't seen them at your distributor, VISD is a software-based method of smoke detection that can use existing analog cameras or purpose-made digital video cameras. Able to see into large areas with high ceilings, VISD is finding a strong market niche in warehouses, commercial properties and other vast expanses of space.
Up the protection and detection
Since my last column on video imaging smoke and fire detection back in 2008 there have been two important industry events that have impacted this technology. First, Fike Corporation purchased axonX which was a premier VISD manufacturer, giving greater credence to the new technology as being here to stay. Secondly, axonX/Fike had its VISD camera listed by FM to ANSI/UL 268 (the system-type, spot smoke detector standard). Since NFPA 72 states "video image smoke detection systems and all of the components thereof, including hardware and software, shall be listed for the purpose of smoke detection," a big hurdle for wider acceptance has been crossed.
Where you have guards or safety personnel watching a facility you can now add another level of protection with the technology. No one will argue that it's not a lot of fun to sit in front of video monitors watching security camera feeds. Even if the scenes are constantly changing, the human mind can only take so much before the mental strain diminishes concentration and effectiveness. Current video technology can provide pixel-changing motion detection so the camera can guard unchanging warehouses, parking lots, empty hallways, closed stores and mall scenes and has become almost a requirement for guards tasked with watching cameras hours on end.
With VISD you can provide smoke/flame detection capability to your customer's existing analog camera systems. This can be accomplished by installing a listed DVR running the same motion detection technology they are currently using for security purposes, along with additional listed software to detect smoke/flames. Smoke drifting in a large open space can be difficult to see on-screen even when a good camera image is displayed. However, the VISD camera can see smoke that is barely noticeable to safety/security personnel. (A trouble signal is produced when light levels fall below the required minimum for smoke detection. Cameras listed for flame detection are not light-dependent.) Once detected, the fire plume is outlined on the monitor to help alert the viewer. Keep in mind that the fire does not have to grow large enough to drive smoke very high in the room or even up to the ceiling.
IP cameras as smoke sensors
If your customer has many cameras at several facilities they can add a DVR to the corporate LAN or send VISD alarm images over the Internet for remote playback and verification. For customers considering adding security cameras to their facility, you can offer individual VISD protection using standalone IP cameras.
Think of these IP cameras as four-wire, addressable smoke detectors because that's pretty much what they are. Because of their embedded software, these cameras can make the alarm decision independently and use built-in dry alarm and trouble contacts to activate the premises fire alarm system. When connecting these cameras to a listed VISD local processor, the IP camera can make use of power over Ethernet (PoE) to simplify the installation, or the cameras may be powered directly from a FACU or fire alarm control unit.