The LWF Blog

Facilities Management & Fire Safety – Fire Safety Engineering & The Prescriptive Approach – Part 6

November 22, 2018 11:00 am

In LWF’s blog series for those who work in Facilities Management or who have an interest in or responsibility for fire safety, we have been looking at fire safety engineering. In part 5, we examined what might be described as the advantages of fire safety engineering over a prescriptive approach, culminating in the conclusion that fire engineering solutions aim to achieve the fire safety objectives involved, without following a prescriptive code of practice. In part 6, we continue from that point.


Fire safety engineering involves considering all the necessary practical measures required and provides an integrated package which addresses those requirements and works together, rather than a list of independent measures as would be the case with a prescriptive solution.


While fire engineering may not be the same as prescriptive fire measures, it can incorporate elements of prescriptive measures and often does. It can be that an overall fire safety solution for a building might be substantially prescriptive in nature but that a certain element of the building design requires a fire engineered approach. One element that commonly requires a fire engineered design is when the travel distance must exceed the prescriptive norms.


Fire safety engineering can be characterised by:


 A departure from prescription

 A ‘first principles’ approach

 The integration of different fire precautions to achieve a fire safety objective

 Calculation of one or more parameters


While the characterisations might sound straightforward, a ‘first principles’ approach is very involved. Fire Engineers have to approach the situation from the point of view of calculating the probability of fire, how the fire will develop, how it may spread and the effect of toxic gases and smoke, how the fire protection measures will perform, the potential for human reaction and the likely evacuation times.


Fire is such a complex element that we continue to expand our knowledge continually and cannot claim to have a complete understanding of every nuance. However, BS 7974:2001 – Application of fire safety engineering principles to the design of buildings. Code of practice codifies current knowledge and practice.

BS 7974 offers the following definition of fire safety engineering:


“(the) application of scientific and engineering principles to the protection of people, property and environment from fire”


The document provides a framework for a fire engineered approach and it is through this that a fire safety package can be assessed. There are a list of practice directions which work alongside the standard which contain guidance and information on how to undertake analysis of fire safety engineering in buildings.


PD 7974-0 is a guide to the design framework and fire safety engineering procedures.


PD 7974-1 Initiation and development of fire within the enclosure of origin.


PD 7974-2 Spread of smoke and toxic gases within and beyond the enclosure of origin.


PD 7974-3 Structural response and fire spread beyond the enclosure of origin.


PD 7974-4 Detection of fire and activation of fire protection systems.


PD 7974-5 Fire and rescue service intervention.


PD 7974-6 Evacuation.


PD 7974-7 Probabilistic fire risk assessment.


LWF will continue looking at Fire Safety Engineering and BS 7974 in part 7 of this series. In the meantime, if you have any questions about this blog, or wish to discuss your own project with one of our fire engineers, please contact us.


Lawrence Webster Forrest has been working with their clients for over 25 years to produce innovative and exciting building projects. If you would like further information on how LWF and fire strategies could assist you, please contact Peter Gyere on 020 8668 8663.


While care has been taken to ensure that information contained in LWF’s publications is true and correct at the time of publication, changes in circumstances after the time of publication may impact on the accuracy of this information.



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