In the digital age fire detection and alarm systems are being integrated into other building systems. These so-called ‘smart’ systems offer advantages in terms of efficiency, provided the necessary safeguards are in place to ensure, for example, that a person on a terminal in the human resources department does not mistakenly access the fire alarm system via a LAN and leave portions of it disconnected.
“Integration means different things to different people,” says Fire Protection Association Australia, Fire Detection and Alarm Systems National Committee chairman, Kjell Jawerth, who is also technical manager-fire detection at Tyco Safety Products. “In some countries the fire detection and alarm system can be embedded into other systems - share the same hardware and software as, for example, a security system or building management system,” he says. “However, the more complex the total system, the higher the risk of failure due to either component random breakdown, or human operator or software programming errors. With such a fully integrated system, if repairs are required, all systems have to be shut down, including the fire detection and alarm system, even though there may be no faults in the dedicated part of the fire detection system.
“Australian Standards takes the view that both the fire detection and alarm system and the sound system for emergency purposes must each be able to be switched off for repairs without affecting the other, nor can it be dependent on any other system in the building. However, integration of the form where the fire alarm conditions are transmitted to, a security system, building management system, lift control, and mechanical ventilation systems is a common practice and fully permitted. The signal is only one way - from the fire detection system to the other systems.”
In the US, experts say that as fire detection systems become more integrated into other building systems, the role of fire alarm systems will expand beyond detecting fire and notifying building occupants and the fire service, so that the sensor currently used to control lighting in a room and security could be used to indicate to firefighters that a room is unoccupied, sparing them the time and danger of checking that room for a potential rescue. There are, however, potential problems says Jawerth: “This form of integration is possible by feeding the fire alarm signal and security signals to a common head end such as a colour graphic display. This, and other building status information, can assist a fire response team to more effectively respond to a fire. However, a fire in an unoccupied room must be attended with the same urgency as it may be the seat of the fire. The room may have had sleeping occupants and the lighting control system may not indicate their presence. The infrared radiation from a fire will probably also mask body heat from occupants. Systems like this will require more training of firefighters and a more knowledge of the building, which may not be practical. The fire detection and alarm system must remain independent of any other system for operational reliability.”
Another suggested benefit of integration is that the security switch on a door could be used to confirm to firefighters responding to a working fire, the integrity of the fire doors. “Fire detection systems are often used to release locked security doors in case of fire,” Jawerth explains. “The confirmation that the doors have opened may be of value to the firefighters, but is better displayed on a separate and independent system. However, security and lighting communication circuits are not normally rated to withstand the heat of fire, so the accuracy of such signals during fire cannot be relied upon. Fire-rating of all wiring would be considered too costly in most systems – however, performance-based fire engineering may be able to justify it in some cases. Fire detection and alarm system integration with the alarm monitoring centre and the fire response centre is also worth considering so that firefighters can have up-to-date information of the fire development while they are travelling to the scene.
The latest in fire detection and alarm systems, according to Jarweth, is advances in detection technology to more accurately detect real fires and provide greater immunity to deceptive phenomena. “Combined photoelectric and heat detection has made it possible to eliminate the need for the ionisation chamber smoke detector (ICSD) where there is a significant risk of fast-developing flaming fires. This also provides better detection of smouldering fires that the ICSD cannot provide.
“Using advanced fuzzy logic algorithms has also improved immunity to deceptive phenomena, reducing the risk of unwanted alarms. Where the sensor combination and interaction is freely configurable by the fire detection control equipment, they have been called ‘virtual’ detectors as a number of effective detection modes can be configured with just one detector unit. However, some deceptive phenomena produce what looks like smoke – for example steam and cooking fumes which, when persistent, may still give unwanted alarms. It has been said that carbon monoxide gas and heat are the only true indicators of fire, and when these sensors are combined in one detector that responds to slow smouldering fires and flaming fire, it forms an almost ideal fire detector that is totally immune to steam and so on.
“However, for smoke management, where sensing of visible smoke is necessary for early escape or to activate smoke control to maintain visibility in exit path, photoelectric smoke detection is still needed.”
Fire Protection Association Australia is the country’s major technical and educational fire safety organisation. On 28 April it will hold a seminar on building codes and Australian Standards relating to passive fire and smoke containment.For further details visit www.fpaa.com.au