RiskXtraJune2019
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FIA Technical Briefing: Selection of Fire Detectors<br />
Designers must therefore consider carefully<br />
the types of false alarm risks present before<br />
selecting a detector.<br />
Process of selection<br />
The process for deciding the right type of<br />
detectors is a two-stage exercise. First, it’s<br />
important to analyse the fire risk and, from<br />
that, select the best detectors for detecting that<br />
type of risk.<br />
Fire risks can be defined as a material,<br />
substance or action that increases the<br />
likelihood of an accidental fire occurring. For<br />
example, electric wiring is a potential fire risk,<br />
which when burning produces smouldering<br />
white smoke. Using multi-sensor detectors or<br />
optical detection would be the best solution in<br />
this type of situation, though it needs to be<br />
considered against the second step.<br />
That second step in the process is to<br />
consider which non-fire phenomena are likely<br />
to arise within the specific areas to be<br />
protected – whether this is steam, smoke, dust,<br />
high ambient air flow or rapid thermal change.<br />
The type of detector selected can then be<br />
refined to ensure the correct balance between<br />
detection and the avoidance of false alarms.<br />
However, if you’re not familiar with the types<br />
of risks and the protection that different<br />
detectors offer, this may be difficult to<br />
evaluate. Thankfully, there’s help available<br />
from the Fire Industry Association (FIA).<br />
Assistance in the process<br />
The FIA has created a document entitled ‘Fire<br />
Alarm Detector Applications and Documentation<br />
of the System’ to assist with the process of<br />
selecting the right type of detector based on<br />
false and unwanted alarm risks.<br />
Initially created as part of the FIA’s input into<br />
the revision of BS 5839-1 (published in 2017),<br />
the organisation subsequently updated the<br />
document to ensure that detection<br />
technologies not included in the original text<br />
were also taken into account. Specifically,<br />
aspirating smoke detection, line type heat<br />
detection and beam detectors were added.<br />
The document is designed to help practising<br />
professionals choose the correct detection<br />
technology for use in specific situations, taking<br />
into account the fire risk present as well as<br />
possible sources of false alarms. This<br />
document is deliberately intended to assist<br />
with the task of selecting and clearly recording<br />
the type, sensitivity and settings chosen for all<br />
detectors (including multi-sensor detectors)<br />
relating to the perceived risks.<br />
The guide begins with a simple, easy-to-use<br />
flowchart to help aid the selection process and<br />
solidify each step since there are other factors<br />
beyond considering the fire risks and the risks<br />
for false alarms mentioned here.<br />
In addition, the document includes a Detector<br />
Selection Table. It’s a template to allow the<br />
documentation of the main risks and all<br />
decisions and reasoning behind the detection<br />
choices made, either during system design or<br />
at the time of any subsequent change to the<br />
fire detection regime. It’s intended to assist<br />
designers, commissioning engineers and<br />
service/maintenance technicians to keep good<br />
records of their detection choice decisions and<br />
the rationale underpinning them.<br />
False alarm risks<br />
Since fire risk matters as well, only detector<br />
types best suited for a particular risk should be<br />
used to detect the potential fire. To help with<br />
the selection, the document also includes a<br />
table focused on false alarm risks (ie steam,<br />
smoke, dust, sparks or naked flames, etc).<br />
The table is included to assist the system<br />
designer in the process of assessing which<br />
types of detectors are most likely to realise<br />
false alarms in given situations. This will enable<br />
the designer to be more aware and, ultimately,<br />
end up with a more informed decision.<br />
By following the guide carefully – and using it<br />
in conjunction with the similar information<br />
given in BS 5839-1 – fire detection and alarm<br />
system designers should be able to provide<br />
buildings and their end user occupants with a<br />
high level of fire protection.<br />
*If you wish to access ‘Fire<br />
Alarm Detector Applications<br />
and Documentation of the<br />
System’, the guide is<br />
available to download free of<br />
charge from the FIA’s<br />
website. Visit www.fia.uk.com<br />
Bernard Laluvein:<br />
Director of BEH Laluvein<br />
Consulting Ltd and Chairman of<br />
the Fire Industry Association’s<br />
Fire Detection and Alarms<br />
Council<br />
“Certain types of detector are designed to be very sensitive<br />
to certain products of fires. For example, optical smoke<br />
detectors respond very quickly to dense smoke”<br />
49<br />
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