Risk Tolerability Limits for Fire Engineering Design: Methodology and Reference Case Study

A simple framework for setting risk tolerability limits is proposed following a literature review of risk acceptance in fire safety engineering and a feedback round with international fire safety professionals. The framework provides practical guidance for the application of international fire safety guidance, such as the recently published UK guidance document on probabilistic risk assessment for the fire design of buildings, PD 7974-7:2019, which provides a state-of-the-art framework to assess adequate safety for complex fire engineering designs. However, the application of this guidance document is hindered by two main constraints: (1) PD7974-7:2019 requires risk tolerability limits to be set, but lacks guidance on defining them for a specific building project, and (2) no reference case studies are given that demonstrate the application of PRA methods to fire engineering design. In order to help fill this gap, a risk tolerability framework is developed and proposed herein. Finally, it is applied to a reference case study of a UK office building. Considering the developed framework, further research needs are identified. It is expected that the proposed risk tolerability framework and the presented reference case study can support the application of PRA to fire engineering design and ease stakeholder communication on setting risk tolerability limits.