In the realm of fire safety, regulations, and standards are constantly evolving to ensure the utmost protection for building occupants. One notable change is the increased emphasis on pressurisation and fire safety, especially in single-stair buildings taller than 18 meters. The recently updated BS 9991:2021 standard highlights the importance of pressurisation systems, making them a mandatory requirement for qualifying structures. In this article, we delve into the implications of these regulations and explore the government’s latest recommendations.

BS 9991:2021 Advice

The BS 9991:2021 standard’s draft version introduces a significant shift in the approach to pressurisation and fire safety in single-stair buildings above 18 meters. Section 10.1 e) explicitly outlines the requirement for pressurisation, leaving no room for exceptions:

BS 9991:2021 Draft Version: section 10.1 e):

“The staircase and associated lobby should be protected with a pressurization system conforming to BS EN 12101-6 for a firefighting system (see Figure 19). The air intake for the system should be drawn in at ground storey level, or at a higher level if controlled from more than one façade. Natural ventilation or mechanical ventilation of the staircase and associated protected lobby should not be provided as alternatives to a BS EN 12101-6 pressurization system.”

This move is a proactive step to enhance the effectiveness of smoke control systems, recognising the pivotal role that pressurisation plays in ensuring the safety of occupants during a fire emergency.

Phasing Out Natural Systems

Another noteworthy aspect of the updated standard is the limitation placed on natural systems, which are now permissible only up to a maximum building height of 30 meters (see clause

BS 9991:2021 Draft Version: Clause

“Natural systems Natural smoke ventilation systems should be used only in buildings up to 30 m in height, with multiple stairs and with travel distances up to those recommended in Figure 8. For buildings over 30 m, and/or where travel distances are in excess of those recommended in Figure 8, a mechanical smoke ventilation system or pressure differential system should be used”

This signals a phasing out of natural shafts in favour of pressurisation for taller single-stair buildings. The rationale behind this change is rooted in the enhanced reliability and efficiency offered by pressurisation systems, particularly in high-rise structures.

Architectural Motivations and Collaborative Design for Pressurisation and Fire Safety

The inclusion of a secondary staircase as a fire safety measure impacts the available lettable space in a building. This, in turn, motivates architects to continue designing tall single-stair buildings. In such instances, collaboration with M&E consultants and specialist contractors becomes crucial. These professionals play a key role in ensuring that the necessary precautions, including pressurisation and fire safety systems, are seamlessly integrated into the building’s design.

The Golden Thread of Fire Safety

As the industry shifts towards more sophisticated fire safety measures, the concept of the “golden thread” will become essential. The golden thread refers to the key fire safety information that should be consistently maintained and easily accessible throughout a building’s life cycle. This includes details about fire safety features, strategies, and materials.

Early engagement and collaboration are the key to establishing the golden thread effectively. Design team members must proactively involve competent specialists at the project’s early stages. This collaboration ensures that the concept design aligns with the latest code requirements and integrates necessary fire safety features seamlessly.

Coordination with builders is also critical during the early stages of a project. This ensures the provision of suitable space for critical elements such as pressurisation supply shafts and air release shafts. Adequate plant space for fans and equipment, alongside allowances for associated electrical supplies, must be factored into the design to facilitate a smooth implementation of pressurisation systems.

Early-Stage Pressurisation and Fire Safety Challenges

One of the primary challenges architects and engineers face in the early stages of projects is accommodating all of the equipment associated with pressurisation systems. This includes air delivery ducts, air release shafts, pressure relief vents, and other critical components. Failure to make allowances for plant space during the initial planning phases can lead to severe problems later on, hindering the smooth integration of pressurisation systems into the building’s design.

System design is inherently complex and time-consuming. It requires careful consideration and expertise to ensure optimal functionality and compliance with safety standards. Recognising these challenges, we strongly advise the early engagement of a specialist designer. The involvement of a professional with expertise in pressurisation systems is crucial to ensuring that pressurisation systems align seamlessly with the latest code requirements.

Innovative Solutions for Pressurisation Systems

As the industry adapts to new fire safety standards, architects and engineers must face the challenges posed by pressurisation systems head-on. The emphasis on early engagement of specialist designers is step one in taking the proactive approach needed to ensure the seamless integration of pressurisation systems and, ultimately, the safety of building occupants during a fire emergency.

We’re here not just to equip you with knowldege, but also to lend an ear to any challenges you might face or questions you may have about pressurisation systems. Email our design team with your questions to start a conversation that lights the path to safer, smarter building designs.