The introduction of Gateway 2 under the Building Safety Act and the creation of the Building Safety Regulator (BSR) has fundamentally changed how fire safety systems are reviewed and approved. This is nowhere more evident than in the design of smoke ventilation systems. Gateway 2 is not a conceptual checkpoint, it is a detailed design approval stage, requiring submissions that demonstrate how a building will actually function in a fire scenario.

Who does this apply to?

The Gateway 2 regime came into force in October 2023 and applies to new higher-risk building work submitted for building control approval from that date onwards. Buildings that were already built and occupied before this point are not subject to Gateway 2. Those existing buildings instead fall under the separate in-occupation duties introduced by Part 4 of the Building Safety Act 2022, which include requirements to register with the BSR, maintain a safety case, and engage with residents on building safety matters. The detailed design and approval obligations discussed in this article are therefore a new-build and design-stage concern.

For schemes currently in design, there is also an important upcoming deadline to be aware of. From September 2026, all Gateway 2 building control approval applications that adopt BS 9991:2024 must use the 2024 edition of the standard. Any scheme still referencing BS 9991:2015 at that point will need to demonstrate why, and show that compliance with Building Regulations is still achieved. Teams currently in early design should be working to the 2024 standard now.

A people-centric shift in smoke ventilation

One of the most important changes influencing smoke ventilation design is the move toward a more people-centric approach, as reinforced by BS 9991:2024. Buildings must now be designed to support the safe evacuation of all occupants, including those with impaired mobility. This has led to the requirement for evacuation lifts and in turn fundamentally changes the role of smoke ventilation systems.

Historically, smoke ventilation focused on protecting the stair core to maintain a clear escape route and support firefighting operations. Today, that is no longer sufficient. Designers must also ensure that the evacuation lift lobby remains clear of smoke ingress so that occupants who may need to wait for assisted evacuation can do so safely. This extension of protection significantly increases the complexity of system design and performance requirements.

Limitations of traditional approaches

The recently issued Smoke Control Association (SCA) guidance on Smoke Control to Common Escape Routes in Apartment Buildings (Flats and Maisonettes) has highlighted the risks associated with certain traditional approaches. For example, naturally ventilated corridor and lift lobby arrangements (“natural–natural” systems) may introduce unintended airflow interactions that compromise protected spaces. And in the majority of cases, a “natural-natural” configuration cannot be assumed to provide adequate protection without project-specific detailed assessment.

As per BS 9991:2024, it is no longer adequate for a mechanical smoke ventilation system (MSVS) to rely on comparative CFD (Computational Fluid Dynamics) analysis to show equivalence to a natural smoke shaft system. Designs must instead demonstrate that defined performance criteria are met — such as preventing smoke from entering the evacuation lift lobby.

Early specialist involvement is essential

Given this increasing complexity, the importance of early specialist involvement cannot be overstated. Smoke ventilation systems must be developed in coordination with the fire strategy, architectural layout, and building services design. A simplistic overview of the smoke ventilation design is unlikely to meet Gateway 2 expectations and could lead to non-approval.

Another important consideration under the Building Safety Act is that smoke ventilation systems now form part of the Fire and Emergency File. This requires designers to clearly document how the system operates, including control arrangements, equipment selection, cause and effect, and any interfaces with other building systems. As a result, the design must not only perform effectively in a fire scenario but also be presented in a way that can be readily understood and used by the responsible person and attending fire and rescue services.

A fundamental shift in mindset

Ultimately, Gateway 2 requires a shift in mindset. Smoke ventilation is no longer about demonstrating compliance with guidance in principle — it is about proving that a system will perform effectively in practice, under real fire conditions. With the September 2026 deadline for mandatory adoption of BS 9991:2024 approaching, the window for schemes to align their designs is narrowing. Engaging a smoke ventilation specialist early in the design process is essential to ensure that systems are fully integrated, compliant, and capable of delivering the required performance.