The LWF Blog

Fire Safety Engineering for Design – Quantitative Risk Assessment – Part 64

January 24, 2022 12:36 pm

LWF’s Fire Safety Engineering blog series is written for Architects, building designers and others in the construction industry to highlight and promote discussion on all topics around fire engineering. In part 63, LWF discussed quantitative risk assessment (QRA) and cost-benefit analysis (CBA). In part 64, we continue to discuss QRA and CBA.

It was established in our last blog that some industries require guidance on the value (in currency) that society is willing to place on the prevention of a fatality. It is called the value of preventing a fatality (VPF) and can be used in a CBA to assess if the cost of a risk reduction measure is viable. Value multipliers may also be applied to the VPF when considering events which may result in multiple fatalities, such as could be the case with a fire.

Society is less tolerant of multiple fatalities than it is of one fatality, it is also expected that members of the public will be more protected than employees in the workplace.

A value multiplier may also be applied to the cost part of the analysis, this figure represents the level at which risk reduction measures are deemed ‘grossly disproportionate’.  As a rule of thumb, costs for risk reduction measures of less than three times the value of risk reduction achieved are to be considered reasonably practicable for implementation.

However, it is not the case that where the cost is three times (or more) greater than the value of risk reduction that would be achieved, that it can be disregarded under ALARP. There are other criteria to consider such as the potential concern from society or relevant good practice and requirements.

PD 7974-7:2019 Application of fire safety engineering principles to the design of buildings. Probabilistic risk assessment provides guidance on the application of probabilistic risk assessment. It suggests it is most appropriate to apply QRA and CBA where comparisons are made between alternative risk reduction measures – most commonly a fire-engineered solution compared to a prescriptive solution. The establishing of absolute quantified values for acceptability is less straightforward and where it must be achieved, the techniques and input data should be agreed with all those with an interest in controlling fire risk, including the relevant authorities, before proceeding.

In part 65 of LWF’s series on fire engineering, we will … 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 the LWF office on 0800 410 1130.

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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