The LWF Blog

Fire Safety for Facilities Management Personnel – Smoke Control – Part 259

July 1, 2024 10:50 am

Lawrence Webster Forrest (LWF) is a specialist fire engineering and fire risk management consultancy whose aim is to give information on best practice in fire safety for facilities management personnel through this blog series. In part 258, LWF discussed smoke containment by physical barriers. In part 259, we continue on the subject of smoke control by talking about smoke containment by pressurisation.

The control of smoke and prevention of smoke entering essential areas to preserve escape routes is especially important in large and complex builds. In a smaller building, an escape route may be as simple as a corridor with an exit door at the end. In a large and complex building, many floors may have to be traversed by the building’s occupants in order to effect a safe evacuation.

Smoke may be contained by physical barriers, as discussed in the last blog, but in some circumstances, they may not be able to offer a sufficiently high degree of protection. Some examples of buildings where physical barriers may be inappropriate are those where the number of staircases is insufficient for evacuation, or where the fire-fighting stairs cannot be naturally ventilated – or extend significantly below ground level.

Pressurisation may be a suitable alternative to prevent smoke entering important areas. Pressurisation involves the injection of air into escape route staircases or corridors in order to increase air pressure in the escape routes, when compared with surrounding accommodation. This excess pressure opposes and overcomes that which is created by the fire and permits a constant flow of air from the escape route into the accommodation, instead of the opposite way around which would cause the escape route to fill with smoke.

Doorways through which the air is to flow should not be fitted with smoke seals and the protected areas should have air relief vents, to allow the pressurising air to escape easily. This system has been thoroughly tested over time and has been found to work successfully in both test and actual fires.

Design parameters and guidance can be gained from BS EN 1201-6:2022 – Smoke and heat control systems – Specification for pressure differential systems. Kits (which replaced BS EN 1201-6:2005, which, in turn, replaced BS 5588-4). It should be read in conjunction with BS EN 1201-13:2022 Smoke and heat control systems – Pressure differential systems (PDS). Design and calculation methods, installation, acceptance testing, routine testing and maintenance.

In part 260 of this series, LWF will begin to discuss smoke ventilation. In the meantime, if you have any queries about your own facilities or wish to discuss this blog series, please contact LWF on freephone 0800 410 1130.

Lawrence Webster Forrest is a fire engineering consultancy based in Surrey with over 35 years’ experience, which provides a wide range of consultancy services to professionals involved in the design, development and construction and operation of buildings.

 

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.