Managing fire risk in high rise buildings – the case for bowtie safety cases
Multi-occupancy Higher Risk Residential Buildings (HRRBs) have the potential for significant societal impact, with a large number of people concentrated in a small space exposed to foreseeable events such as fire. This was all too starkly highlighted by the Grenfell Tower fire in London in June 2017, which caused the deaths of 72 people – the worst fire in the UK since the 1988 Piper Alpha disaster.
In her independent review of UK building regulations and fire safety following the Grenfell Tower fire (Ref. 1), Dame Judith Hackitt identifies deep flaws in the current system and proposes that the key principle of risk ownership and management needs to be applied alongside a simpler, outcomes-based regulatory framework.
A goal-setting, safety case approach as applied in major hazard industries, and in particular the use of bowtie analysis of significant risks, is one way of addressing Dame Judith’s recommendations. We consider some of the key themes contained in her report (reproduced in italics) and illustrate how a bowtie-based safety case may provide a practical, effective solution.
“There is lack of clarity…over where responsibility lies, exacerbated by… fragmentation…and precluding robust ownership of accountability.” HRRBs are “complex systems where the actions of many different people can compromise the integrity of that system.”
A fully developed bowtie analysis can be used to illustrate, clearly and unambiguously, the safety-critical responsibilities of the parties involved in an HRRB project, including the client, designer, contractor, owner and operator/maintainer. By coming together to build a bowtie model for potentially significant risks, all parties can agree and understand their contribution to the case for safety, and appreciate the contribution made by others as well as any constraints and conflicts that may arise. Collaboration is encouraged and thinking in ‘silos’ is reduced.
Furthermore, a properly completed bowtie analysis provides reassurance to other stakeholders, not least residents, about the safety of their home and demonstrates who is responsible for what when it comes to managing risks.
“Transparency of information and an audit trail all the way through the lifecycle of a building from the planning stage to occupation and
maintenance is essential.”
At the outset, the case for safety is made at a relatively high level, and would then evolve with the building, becoming more detailed and complete with each phase of the project (see Figure 1). The focus is on designing and constructing a safe HRRB, and then maintaining it and managing change so that it continues to be safe.
Change control is a key area for HRRBs where, historically, management of risks has been undermined. Changes may occur frequently during design, construction and ongoing occupation, with little or no thought given to, or even awareness of, the risk basis behind preceding decisions. The bowtie diagram can highlight those risk controls which are susceptible to deterioration as a result of poorly
thought through or inadequately managed modifications to a building’s design, construction, maintenance and operation.
BUILDINGS AS A SYSTEM
We must think of “buildings as a system so that we can consider the different layers of protection that may be required to make that building safe on a case-by-case basis.”
The completed bowtie diagram illustrates clearly, and in one place, the multiple layers of protection and how they are supported by safety critical activities and competencies, defined safety-critical equipment, and effective, documented management systems.
Figure 2 illustrates an extract from a bowtie for fire in a HRRB, including example mitigation controls defined at the design stage, enacted at the construction stage and maintained during the occupation stage to reduce the risk of multiple fatalities as low asis reasonably practicable.
EFFECTIVE USE OF RESOURCES
“The new framework is designed to create a more simple and effective mechanism for driving building safety.”
Whereas the risk levels in industries such as nuclear power generation or oil and gas extraction warrant a project-specific safety case and detailed analysis of the significant risks, any safety case approach for design and construction of HRRBs must be proportionate, reflecting the resources likely to be available. The bowtie approach for significant risks allows technical analysis to be captured, communicated, applied and re-applied in a straightforward and accessible manner.
The knowledge and experience already exists within the industry to create a generic bowtie model for HRRB fire risk management (such as that shown in Figure 2), which could then be made available through industry guidance. The generic model could be customised by specific projects to produce a true picture of the integrity of their proposed building against fire. It could be reviewed when modifications are proposed; and it could be used as an audit tool to assess periodically the building’s current condition, providing ongoing risk monitoring and assurance.
Properly implemented, a bowtie based safety case can provide a practical, effective solution to the many challenges associated with achieving fire safety of HRRBs.
1. Building a Safer Future – Independent Review of Building Regulations and Fire Safety: Final Report, May 2018.
This article first appeared in RISKworld Issue 33
Related consulting services:
BowTieXP Software (Basic & Advanced)
Principles of Regulatory Systems
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