An evaluation of the role of fire extinguishers

71. All categories are exhibiting pronounced downward trends with the number of fires in communal
living premises attended by the FRS falling by 50%.
The role and influence of fire growth modelling
72. Published data regarding the size of a fire is helpful in providing a reference point for the final
extent of a dwelling fire. If the fire was extinguished quickly by whatever means, then the end
state may closely resemble the fire as it was on discovery or when being tackled. However, if there
were delays in sourcing/preparing extinguishing medium or its application was ineffective in
tackling the fire for any reason, then it may not. Given that most fires are contained to the item
first ignited or the room of origin, it is likely that there is not much difference between size at
discovery and when extinguished.
73. Only one study was found that provided an insight into the size of fire from discovery onwards,
capturing this information in survey form. The lack of data from real fires, despite its ready
availability and benefits, means reliance is placed on other means. And yet, an accurate knowledge
of typical fire development behaviour is an essential requirement for meaningful risk assessments.
74. Within the literature, there is an active and extensive body of work addressing various aspects of
fire and fire development, either as a natural or applied science. A number of these seek to
develop a ‘standard’ fire growth curve model. This is clearly an extensive subject, but a brief
overview of its role is useful in considering dwelling/HMO fires.
75. By necessity, the models are usually underpinned by data collected from fires created for the
purpose and set under controlled but often artificial conditions. This approach obviously has many
advantages. Not least, the ability to install equipment to record different aspects of the fire and to
plan when the fire will occur. However, they do have limitations in their ability to replicate real fire
conditions and development. Some of these discrepancies have been exposed through the
ongoing Grenfell Inquiry.
76. Typically, controlled tests produce a pattern of fire growth and decay, often with indicative timings
for the duration of each phase. Examples of the application of the resultant fire development
models include testing scenarios in relation to fire safety for new building designs or to assess
mass evacuation plans. As many of these relate to unique premises with customised fire safety
arrangements, the modelling approach is an appropriate, proportionate and cost-effective option.
77. Quantifying and standardising predicted fire development also underpins influential concepts such
as the ‘Available Safe Egress Time’ (ASET) or ‘Required Safe Egress Time’ (RSET). Their efficacy
relies largely on the assumption that the public/occupants would respond in line with official
assumptions. Further, they assume the fire development to be the dominant feature, and one
largely unaffected by the actions of the occupants/public, which is not supported by the evidence.
78. The models are also used to identify the time after which it is believed anyone trapped in the
building is unlikely to survive. This is informed mainly from fatal fire studies and knowledge about
survivors is notably limited. For example, a recent literature review found no studies that
focussed on the behaviours and motivations of children who survived fires. This has
important ramifications for fire safety across multiple policy areas.
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