Raising the alarm

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Cooper offers a combined sounder, beacon and detector in a single unit.

The first signal that most people will have of a fire in a building is when the alarm system sounds. Whether it is by siren, voice or flashing beacon, this alert is essential to a building's overall life safety system. How alarms are installed and operated must also be carefully considered to enable any fire to be quickly contained and eliminated, while ensuring the safe evacuation of the building occupants. And with the preference for high-rise buildings in the Middle East, ensuring that an effective system is installed has become even more important.

But with many different fire alarms available on the market, how do you decide which should be installed on a particular project?

Fire alarm systems fall broadly into two categories: conventional and analogue addressable. One of the main differences between these types is in the ease of locating any fire. Tyco Middle East business development manager Craig Nixon explains: "It's really to do with the identification of alarms: with conventional systems you may have a zone that could consist of up to 20 detectors, but [the fire alarm panel] wouldn't tell you which particular detector was in alarm mode, it indicates the zone only; with an addressable system [the system] pinpoints exactly which detector is in alarm.

This difference is due to the intelligence of the two systems and their installation.

With a typical conventional system the detector will send a signal to the fire alarm panel when a preset condition is reached; the panel in turn triggers the alarm sounders. Detectors are normally connected to the fire control panel via dedicated circuits, with each representing an area or zone in a building. Each zone may include a number of detectors, however the alarm panel will give the same signal regardless of which unit operates an alarm.

With an analogue addressable system the detectors are connected on a single loop that may cover several areas. However each detector has a unique address, so when it is triggered the fire alarm panel can identify the specific point in the building where the fire is occurring.

"The benefits of the analogue addressable system is that you can pinpoint the location of where the fire has been detected or the likelihood of a fire," confirms Bhasker Iyer, regional sales leader, Honeywell Building Solutions Middle East. "In a non-addressable installation, detectors are in one of two states - normal or alarm - individual detectors are not identified or given a specific address or location in the building," adds Hochiki Europe export sales manager Pervez Khan.

A third product type is that of digital addressable reports Tyco's Jonathan Gilbert. "The advantage of that type of system is that it's more robust," Gilbert states. "If you have electrical interference the current can change and you may get wrong readings [with analogue addressable systems]. Whereas a digital system like Tyco's MX Digital uses frequency shift key signalling which is unlikely to get interfered with by electricity," he adds.

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