The LWF Blog
Fire Safety Engineering for Design – Smoke Ventilation – Part 189
June 24, 2024 10:28 amLWF’s Fire Safety Engineering blog series is written for Architects, building designers and others in the construction industry to highlight and promote discussion on all topics around fire engineering. In part 188, LWF discussed smoke layer depth and suspended ceilings. In part 189, we talk about pressure differentials and smoke ventilation.
When designing smoke ventilation systems, pressurisation is an important issue. It is important that excessive pressure differentials are not created, beyond that which is required to make the system effective. Where excessive pressure is created in a pressurised area, the contrast between that and the depressurised space beyond could be so great that the force required to simply open a door is too great. The force required should adhere to regulatory or the manufacturer’s standards. Typical pressure requirements are 100 N in Europe or 67 N from NFPA 101.
As pressure differential systems are designed with the aim of maintaining tenability in the escape routes of a building (in the main), then a struggle to open a door due to a large pressure differential would be potentially dangerous to the building occupants.
At the early design stage, it may be difficult or impossible to calculate door opening forces. In such cases, the difference between pressurised and depressurised areas should be no more than 60 Pa in Europe.
There are some additional potential issues with pressurisation that should be borne in mind at the design stage. The potential for pressure difference between the area of fire origin and adjoining accommodation raises the risks of closed doors being opened, or adverse movement of smoke into adjoining spaces.
There is potential for unlatched doors to be pulled open by the pressure differential in two areas, when it is between 25 and 30 Pa. However, such concerns would be dependent upon the doorset, ironmongery and self-closing mechanism chosen and can be mitigated.
Further information and guidance on pressurisation systems can be found in BS EN 1201-6:2022 Smoke and heat control systems – Specification for pressure differential systems. Kits. which replaces BS EN 1201-6:2005 (withdrawn).
In part 190 of LWF’s series on fire engineering we will begin to look at the tenability criteria for smoke ventilation system design, beginning with smoke hazards. In the meantime, if you have any questions about this blog, or wish to discuss your own project with one of our fire engineers, please contact us.
Lawrence Webster Forrest has been working with their clients since 1986 to produce innovative and exciting building projects. If you would like further information on how LWF and fire strategies could assist you, please contact the LWF office on 0800 410 1130.
While care has been taken to ensure that information contained in LWF’s publications is true and correct at the time of publication, changes in circumstances after the time of publication may impact on the accuracy of this information.