Performance-based approaches to fire safety for complex buildings

The objectives of fire safety extend beyond protecting human life from injury or death. They may also include minimising business disruption, reducing property damage, protecting organisational reputation and limiting environmental impacts. However, minimum statutory requirements primarily focus on life safety, making it important to consider broader fire safety objectives during the design process.

In England, the Building Regulations 2010 establish the functional fire safety requirements under Part B, covering means of warning and escape (B1), internal fire spread (B2 and B3), external fire spread (B4), and access and facilities for the fire service (B5).

Approved Document B provides practical guidance on meeting these requirements, while recognising that alternative approaches, including performance-based fire engineering, may be adopted to demonstrate compliance. For complex buildings, such as airports, atriums and very tall buildings, conventional prescriptive guidance may not adequately address the specific fire safety challenges, requiring a more tailored, performance-based approach.

BS 7974 and the International Fire Engineering Guidelines (IFEG) provide structured methodologies for developing performance-based fire safety strategies. These approaches involve defining fire safety objectives, identifying credible fire scenarios, undertaking appropriate engineering analyses and evaluating the proposed design against established performance criteria. The findings, assumptions, limitations and recommendations should be clearly documented within the fire engineering assessment.

Performance-based fire engineering may involve computational fluid dynamics (CFD) modelling to assess fire and smoke development, alongside evacuation analysis to evaluate occupants' ability to reach a place of safety under different fire scenarios. This commonly involves comparing the Available Safe Egress Time (ASET) with the Required Safe Egress Time (RSET), taking account of occupant characteristics, evacuation arrangements and tenability conditions.

Airports present unique fire safety challenges due to their complex operational and security requirements. Evacuation strategies must consider the segregation of screened and unscreened passengers, while maintaining appropriate means of escape. The interface between aircraft boarding bridges and terminal buildings also requires careful consideration of credible fire scenarios, including potential aviation fuel spill fires where relevant.

Very tall buildings present additional challenges due to their height, large occupant populations and potential mixed-use arrangements. Evacuation strategies may require phased evacuation, enhanced occupant notification systems and reliable communication arrangements for emergency responders. Firefighting operations are also more challenging, as external access to upper floors is limited, increasing reliance on internal firefighting facilities and water supplies. Furthermore, the pronounced stack effect in tall buildings can influence vertical smoke movement through shafts, stairwells and other openings, requiring careful consideration within the fire strategy.

Beyond these established building typologies, emerging technologies and sustainability commitments are introducing additional fire safety challenges. The increasing adoption of alternative energy systems, innovative construction materials and new building technologies requires fire engineers to remain informed of the latest research and industry developments, particularly where technological innovation is progressing faster than the development of relevant codes and standards.

Changing demographics, including Europe's ageing population, also highlight the growing importance of inclusive fire safety design. Fire strategies must increasingly consider not only accessibility but also egressibility, ensuring that evacuation arrangements adequately address occupants with varying mobility and assistance requirements.

These evolving challenges reinforce the importance of performance-based fire engineering, supported by sound engineering judgement, scientific evidence and a thorough understanding of the building's specific risks. By adopting a holistic approach to fire safety, engineers can develop solutions that accommodate architectural innovation, sustainability objectives and operational requirements without compromising the intended level of safety.

For more information about SOCOTEC's performance-based fire engineering services and our approach to developing fire strategies for complex buildings, please watch our webinar, Fire Strategies in Complex Buildings, or contact our Fire Engineering team.