The LWF Blog

Facilities Management – Fire Detection and Fire Alarm Systems – Part 9.

August 4, 2016 2:47 pm

In our recent blog series for those who work in Facilities Management, we have been looking at Fire Detection and Fire Alarm Systems. In our last issue, part 8, we looked at how Aspirating Systems can be used to ‘sample’ the air for smoke in areas where a conventional system would not be practical, or indeed in protected properties where such a system is installed so as to be non-intrusive visually. In this blog, we will look at a few more different types of fire detection and how they might be utilised in practice.


A Flame Detector is basically a line of sight detector which works by detecting either the Infrared or UV radiation emitted by a flame. An infrared detector uses a solid state infrared sensor which detects and sounds an alarm only if the radiation ‘flickers’ at a frequency associated with fires. An Ultraviolet detector works on the same principle as a Geiger-Muller tube.


Flame detectors must be able to survey the entirety of the protected area without line of sight obstruction. Additionally, they are expensive to purchase and install and so are best used in those situations requiring specific flame detection, such as in a situation involving flammable liquids.


UV detectors can be used outdoors, for example, to provide coverage to external plant. More commonly now though, Infrared detectors which are ‘solar-blind’ are available. A standard infrared detector can be used for indoor applications too, in those instances where the ceiling height is significant and this might cause issues with standard smoke or heat detectors.


One of the more recent additions to the range of detectors available is that of the Combustion Gas Detector. They are designed to sense the gases which a fire produces, most commonly Carbon Monoxide, but there are other gases which could be detected.


A carbon monoxide fire detector sensor is an electrochemical cell, which should not be confused with a carbon monoxide detector often found in people’s homes to warn of faulty gas appliances, for instance.


While a carbon monoxide fire detector can be most useful, in that it is not likely to fall victim to many of the issues affecting other detectors – steam, dust etc. – it has one significant failing. Carbon Monoxide is produced by a fire when it is not burning efficiently, i.e., there is insufficient oxygen which is limiting the growth rate of the fire, but it would be less effective in the face of a flaming fire which has plenty of ventilation.


In next week’s blog, we will look at the centre of a fire alarm installation – the control equipment. 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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