New guidance has been issued because of concerns that inappropriate materials are being specified for smoke shafts.
In April, the Finishes and Interiors Sector (FIS) issued a safety alert concerning the use of gypsum-based systems in the construction of smoke shafts for mechanically ventilated systems in some high-rise buildings1.
It advised its members that tests for gypsum-based systems do not replicate the pressure-differential conditions or measure leakage, which may be required for this application.
The FIS and the Smoke Control Association (SCA)2 both recommend that materials for smoke control ducts and shafts are tested in accordance with BS EN 1366-8: Fire resistance tests for service installations. Smoke extraction ducts. This covers air leakage, integrity, insulation, and mechanical stability under pressure, the specific requirements of which are detailed in BS EN 13501-4.
The SCA says the standards are considered a minimum requirement to meet The Construction Products (Amendment etc.) (EU Exit) Regulations 2019.
In a Technical Note3 published in January, British Gypsum stated that while its GypWall Single Frame and Shaft systems are tested for fire resistance, they are not tested in accordance with BS EN 1366-8 or BS EN 12101-3, so it could not make any performance claims around these standards. BS EN 12101-3 is the specification for powered smoke and heat control ventilators.
British Gypsum’s guidance note says ‘systems should not be used as a replacement for ducting that has specific pressure requirements and is tested to different standards’.
The SCA statement says that, as buildings increase in height, there is competition for space, which can constrain the size of smoke ducts or shafts, leading to larger fans and increased negative pressures in shafts and ducts. It states that this makes it even more critical that materials are tested to withstand these conditions.
Guidance on the subject has also been published by the Association for Specialist Fire Protection4, and the Gypsum Products Association5.
Viewpoint: the CIBSE Fire Safety working group
When smoke shafts are designed as part of smoke control systems, CIBSE’s Fire Safety working group recommends:
- Functionality of the system design should be agreed at the outset of the building design and the shaft considered by the multidisciplinary design team at early design stages (RIBA 2 and before Gateway 1 of the Building Safety Act).
- Only one party should be the system ‘designer’, and they need to have the demonstrable competence to design the system and confirm the appropriateness of all elements within it. BS 7346-8 gives guidance on all the responsibilities and how they affect different parties.
- The designer needs to consider all applicable Building Regulations (such as the functional requirements of Part E, O, F, L, M and B) in the system design.
- The designer should use guidance applicable to the type of system chosen and follow a process such as BS 7346-8. They should also ensure that any relevant test evidence and classifications of the systems, their components and the construction materials are clear and appropriate.
- Any other professionals involved in specifications or installations that affect the design of the smoke control systems are advised to confirm with the designer to ensure that their elements meet the system designer’s requirements.
- Maintain a golden thread of information on the performance, specification, components, classifications, construction materials and installation.
- Keep commissioning records and maintenance information so that elements are maintained and serviced for the life-cycle of the project.
If you have topics you’d like the CIBSE Fire Safety working group to address, contact technical@cibse.org
References:
1 GypWall Systems and Smoke Shaft Guidance, British Gypsum, bit.ly/CJGypSm25
2 FIS Safety Alert: Suitability of gypsum-based systems in the construction of smoke shafts, Finishes and Interiors Sector, bit.ly/CJFISSh25
3 Reaction to fire classification for protected/smoke shaft walls. Interpretation of specific clauses within Approved Document B (AD. B), Gypsum Products Development Association, bit.ly/CJGPDA25
4 Position on smoke shaft construction materials , Advisory Note 36, Association for Specialist Fire Protection, bit.ly/CJASFP3625
5 SCA statement on smoke shaft construction materials, SCA bit.ly/CJSCASS25
