What Is Performance-Based Fire Engineering?

UK building regulations provide two routes to demonstrating compliance with fire safety requirements. The prescriptive route follows the guidance in Approved Document B, BS 9991 or BS 9999, applying specific rules about travel distances, compartment sizes, fire resistance periods and other design parameters. The performance-based route uses engineering analysis to demonstrate that a building achieves the required level of life safety, even if it departs from the prescriptive guidance.

Performance-based fire engineering — also called fire engineering design or functional fire engineering — involves applying the principles and techniques of fire science to develop and justify alternative solutions for buildings where prescriptive codes cannot be directly applied or where the designer wants to achieve something that the prescriptive approach would not permit.

When Is Performance-Based Fire Engineering Used?

• Buildings with unusual geometry — atria, underground spaces, open-plan layouts — where prescriptive travel distances cannot be met
• Historic and listed buildings where prescriptive measures would damage architectural integrity
• Innovative or experimental building designs where no prescriptive code directly applies
• High-rise buildings where standard ADB guidance is insufficient or inappropriate
• Buildings where the prescriptive approach would require excessive passive fire protection that could be reduced through engineering analysis
• Mixed-use buildings with complex occupancy interactions

The BS 7974 Framework

In the UK, performance-based fire engineering is carried out under BS 7974 — the code of practice for the application of fire safety engineering principles to the design of buildings. BS 7974 establishes a framework for fire engineering that includes fire initiation and growth, fire containment, smoke hazard, fire detection and activation, active fire suppression, fire service intervention, occupant evacuation and structural response.

A BS 7974 fire engineering report sets out the engineering approach, the fire scenarios considered, the analysis methods used (which may include computational fire dynamics modelling), the results, and the conclusions on whether the performance criterion is met.

Fire Modelling

One of the most powerful tools in performance-based fire engineering is computational fluid dynamics (CFD) fire modelling — computer simulation of fire and smoke behaviour within a building. Fire modelling allows engineers to assess how smoke will behave in complex geometries, test the performance of smoke control systems, and evaluate the time available for evacuation against the time to hazardous conditions. Fire Safety Services uses industry-standard fire modelling tools for complex projects.