05 Oct New guidance

Over the past decade, there have been substantial advancements related to fire risk assessment through research and practical experience. In recognition of these advancements, the SFPE has embarked upon and is now nearing completion of its second edition of the SFPE Engineering Guide to Fire Risk Assessment. Francisco loglar, Phd, PE, and Victor Ontiveros, Phd, Jensen Hughes explore the guide further.

Risk and fire risk assessment

The Guide defines risk as the potential for realising unwanted adverse conditions and considering scenarios and their associated likelihoods and consequences. Risk is a quantitative or qualitative measure of fire-incident loss potential for fire protection engineering applications in event likelihood and aggregate consequences.

Fire risk assessment includes evaluating risks associated with fires affecting buildings, facilities, or processes. Fire risk assessment is used to:

• Select an appropriate design considering the fire risk and cost associated with various alternatives.
• Manage the fire
• Inform resolutions of a regulatory process, such as evaluating code compliance, etc.

Revised fire risk assessment process

The general overview of a fire risk assessment process is captured in the revised Guide. The flowchart covers four distinct phases of a fire risk assessment:

Phase 1-   Planning. The first four activities are associated with the planning phase of a fire risk assessment. These activities clearly define the scope and objectives, collect the information necessary to perform the analysis, identify the risk assessment methods, and define the acceptance or tolerance criteria governing the process.

Phase 2 – Execution. The risk assessment proceeds with the technical work, including a hazards analysis, definition, characterisation of the scenarios, and the risk evaluation.

Phase 3 – Risk Communication. Once the risk evaluation process is completed, the next phase is risk communication.

Phase 4-   In Service. The fourth phase is residual risk management and monitoring, where conditions governing the risk are monitored to identify configurations associated with risk increases that may not be mitigated.

Risk assessment method selection

The risk assessment method relates to the detail to which each scenario is described and quantified concerning the level of potential risk. The analysis can range from qualitative to quantitative, including semi-quantitative approaches.

Qualitative analysis is the evaluation of risk without explicit numerical quantification. In a qualitative assessment, fire risk is evaluated based on the merits of specific designs versus the postulated potential fire events. Qualitative risk methods may be appropriate for evaluating conditions associated with simple systems or configurations with established risk levels. A semi-quantitative analysis refers to the evaluation of risk with simplified quantitative elements supporting assessment.

This approach may be appropriate for evaluating configurations with minor deviations from code or best practices and risk trade-off implications.

Finally, a quantitative analysis is a complete quantification of frequencies and consequences to produce numerical risk levels. The need for a quantitative assessment often arises when evaluating novel, challenging, or complex configurations with significant risk trade-offs.

Acceptance or tolerance criteria

Fire risk assessment involves the need to establish a target risk (i.e., a criterion for tolerance or acceptability). When considering stakeholders’ views, risks are perceived differently. For example, potentially catastrophic risks are perceived differently than less severe ones, and an occupancy where hundreds of people are at risk due to a single fire is perceived differently than an occupancy where only one person is at risk due to a single fire.

The risk matrix

A common approach for representing a risk assessment is a risk matrix. A risk matrix is also a tool for summarising stakeholders’ viewpoints on risk levels (e.g., the combination of high consequence-low probability events). A risk matrix is an effective visual tool for communicating risk and serves as a basis for decision-making in fire risk assessment. The risk matrix shows likelihood (typically frequency or sometimes probability) on one axis and consequences on the other axis. Frequency and consequences are both classified into categories.

Frequencies and consequences governing the risk are threshold levels for decision-making purposes and are independent of the fire protection system and features governing the risk of individual scenarios. The risk of each scenario is determined by considering the fire protection system and applicable features. This element of the fire risk assessment was expanded significantly in the new Guide.

Fire risk estimation

Risk estimation describes how the frequency and consequences for each fire scenario are developed and then combined to characterise the risk used for decision making. The risk estimation process generally produces a table of fire scenarios listing the corresponding frequency and consequence assessments and their corresponding risk estimates. The fire scenario’s frequency and consequence are evaluated in levels corresponding to a risk matrix. This requires identifying and characterising the factors affecting fire scenario likelihood and the corresponding consequences using a structured, systematic approach that can be reviewed, reproduced, and maintained.

Risk evaluation

Risk evaluation and acceptability compares the assessed risk for an individual or group of scenarios with an acceptance criterion typically defined in the risk matrix and agreed upon by stakeholders. The revised Guide describes how risks could be evaluated against a reference value of individual and societal risk derived for a code-compliant building, facility, or process. In this case, the resulting risk should not exceed the reference value, which is implicitly considered acceptable based on code compliance or using the ‘as low as reasonably possible'(ALARP) principle. The comparison is represented as a decision point in the process of determining if the risk associated with a given scenario(s) is ‘acceptable’ or ‘tolerable’.

Sensitivity and uncertainty analysis

Applying a fire risk assessment requires simplifying assumptions using limited data, eliciting engineering judgment, and using analytical or empirical models. In addition, conservative assumptions and input variables are sometimes used to ensure a margin of safety in the results. The revised Guide provides comprehensive steps that focus on sensitivity and uncertainty analysis necessary to assess the impact of these analytical decisions on the study results, so recommendations are made considering their effects.

Documentation and risk communication

Once the evaluation process is complete, the risk assessment should be adequately documented and communicated to stakeholders so it can be monitored. The revised version of the Guide provides the engineer with guidance on documenting and communicating risk.

Residual risk management and monitoring

The residual risk must be managed, and the risk assessment should be routinely monitored to ensure its applicability. A new section of the Guide discusses why this is important. For example, residual risk management relates to what to do with the risk level resulting from the analysis: accept it as it is, transfer it, or reduce it further. Risk monitoring refers to identifying risk-contributing elements to ensure that risk estimates are maintained over time as conditions in the building or facility change.