BS 9991: 2024 – What’s new for smoke control?

At the end of 2024, a new update was published for BS 9991 - Fire safety in the design, management and use of residential buildings. Code of practice. This document gives clear guidance to ensure residential buildings provide proper life safety protection in the event of a fire. BS 9991: 2024 introduces a number of key updates around smoke control systems and it is important that anyone involved in designing, managing or maintaining fire safety systems are aware of these changes. 

What is BS 9991?

BS 9991 provides a best practice framework for ensuring fire safety in residential buildings and can be used to consider buildings at all stages in their life cycle from initial concept design, through to in-use management and extension. It applies to a range of residential buildings including dwellings, blocks of flats, certain accommodation blocks (such as student accommodation and residential care), specialised housing and care homes. The standard complements BS 9999: 2017 - Fire safety in the design, management and use of buildings. Code of practice which provides similar guidance for all other building types.

Both BS 9991 and BS 9999 provide more holistic guidance on fire safety than that contained within Approved Document B to the Building Regulations in England and Wales and Technical Handbook Section 2 – Fire to the Building Standards in Scotland, allowing project teams, building owners and facilities managers to achieve best practice in this area. This guidance is particularly valuable for larger and more complex projects.

What are the key changes for smoke control systems in BS 9991: 2024?

BS 9991: 2024 replaces the 2015 version of the standard and introduces a number of key changes for the specification of smoke control systems.

For residential buildings with a top storey over 18 meters

Automatic Opening Vents (AOVs) which open directly to the outside of the building should no longer be specified. Natural or mechanical smoke shafts are now recommended. In addition, any AOVs which open into ducts or shafts should be smoke control dampers.

For residential buildings with a top storey over 30 metres

Natural smoke shafts should not be used for protecting stair lobbies. Only mechanical smoke shafts are now recommended. These can either be extraction shafts or pressurisation systems.

For residential buildings with a top storey over 60 metres

The mechanical smoke extraction system must be designed in line with the pressure differential principles, methods and verifications contained within Annex D of BS EN 12101-13: 2022. This requires more complex, specialist modelling to ensure systems provide the necessary performance.

Lobby areas for evacuation lifts

All buildings with passenger lifts must now also have at least one evacuation lift per escape stairway (at the same location as each staircase). For buildings over 50 metres with a ‘stay put’ policy, all lifts must be designed to function as a firefighters lift and an evacuation lift. Appropriately sized evacuation lift lobbies should be provided for each of these lifts. For smoke ventilation purposes, this area should be given the same level of protection as a staircase. This may require the provision of additional smoke shafts to adjoining spaces.

Automation of smoke control system in stairwells

Smoke control systems should be designed to connect with, and respond automatically to, an alarm input without the need for further manual inputs. In almost all cases, there should be no override or manual input which impacts how the automatic system behaves. Where this is needed, it should override all alarms and completely stop the automatic function (typically only used where fire fighters deem the fire to be “over”).

Other things to keep in mind

Alongside these changes, the standard also introduces several changes to other aspects of building design which may impact the design, specification and maintenance of smoke control systems. These include:

• Requirements for sprinklers within all residential buildings with a storey above 11 metres and at least two protected staircases to be provided for buildings with a storey above 18 metres (in line with Approved Document B).
• New requirements for the planning and layout of flats and other internal spaces including lobbies and hallways, potentially impacting the positioning of smoke dampers and other measures.
• The introduction of Personal Emergency Evacuation Plans (PEEPs) which are developed and tailored to individuals who may have difficulty evacuating a building by the responsible person. The standard also highlights the need to ensure fire strategies for specialised housing and residential care buildings are based on realistic in-use management. This may impact evacuation times for a building, and require smoke control systems to be adjusted accordingly.

How Colt can help you to meet BS 9991: 2024

The wide range of changes introduced with BS 9991: 2024 mean it is vital that project teams engage with a smoke control expert at the earliest possible opportunity within the design process. Our team of expert engineers are here to help.

Through our extensive range of industry leading mechanical and natural smoke control solutions and years of expertise, we can design and develop smoke control systems which are tailored to your building and are fully compliant with the requirements of BS 9991:2024. This includes using in-house computational flow dynamics (CFD) software to develop pressurised systems to BS EN 12101-13: 2022.

With our UK wide network of trained service engineers, we can also provide dedicated service and maintenance packages for buildings in use. Giving you peace of mind that your smoke control systems will be regularly inspected and (where necessary) repaired by a Competent Maintainer. [DH1]

To discuss your project, get in touch with our teams below.