The LWF Blog

Facilities Management – Fire Detection & Fire Alarm Systems – Alarm Devices – Part 14

September 8, 2016 9:22 am

In our recent blog series for those who work in Facilities Management, we have been looking at fire detection and fire alarm systems generally and most recently, the different types of alarm devices in use. Today we will give an overview of radio-linked systems before looking at the different types of fire detection and alarm systems in use.


Although the majority of fire alarm systems are wired – they literally are connected by wires in order to communicate – a radio-linked system is one which does not need wires. The elements of the system are connected by radio.

A radio system might be used in a building where aesthetics are important and a wired system would be considered intrusive to the décor or architecture. In other circumstances, a radio system might be used to provide protection of an emergency or temporary nature, because of the ease of installation.


While communication between devices on such a system is wireless, the trigger devices and sounders must both be locally powered. The disadvantage is that detectors and call points must therefore be fitted with an internal primary battery, along with a back-up primary battery power source. This means that significant maintenance is required to ensure that the batteries are changed in advance of them losing charge.


In the case of alarm sounders, while they could be powered by mains electricity, because of the nature of the system (wireless), they too are often powered by internal batteries and triggered by radio communication.


If a radio system is being contemplated for use in a building, it is important that a suitability assessment takes place. This comprises testing for radio signal strength throughout all appropriate areas of the property and thorough checks that no other radio waves will interfere with the signals.


In some buildings, where the nature of the construction is such that radio waves do not travel well, it may be that radio repeater units can be installed, which will help to boost the signal in weaker areas.


Types of Fire Detection and Fire Alarm Systems


While the subject of types of fire detection and fire alarm system is a complex one, there are fundamentally only two types of system – conventional and addressable. These systems differ in the way they communicate with the control and indicating equipment (CIE).


A conventional system (also known as non-addressable) receives a signal from one of the detector units indicating a fire, but the CIE is not able to pinpoint which device has sent the signal, only the zone of detection. For this reason, there are restrictions on zone size and type of area, laid out in BS 5839:1.


An addressable system is able to individually identify the source of the alarm and so be more accurate in pinpointing the location of the fire.


In next week’s blog we will continue looking at types of fire detection and fire alarm systems. In the meantime, if you have any queries about your own facilities or wish to discuss this blog series, please contact Peter Gyere in the first instance on 0208 668 8663.


Lawrence Webster Forrest is a fire engineering consultancy based in Surrey with over 25 years’ experience, which provides a wide range of consultancy services to professionals involved in the design, development and construction and operation of buildings.


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