The LWF Blog
Facilities Management & Fire Safety – Smoke Control – Part 5November 2, 2017 2:54 pm
In this blog series for those who work in Facilities Management or who have an interest in or responsibility for Fire Safety, LWF has been looking into smoke control in buildings. In part 4, we established that there were some structural features which could help to keep smoke from spreading into vital areas of a building and which could help protect an escape route, for instance. In part 5, we’re going to look at smoke containment through pressurization, before moving on to smoke ventilation.
It may be that a physical barrier, such as a fire-resistant door with smoke seals, might be insufficient to keep smoke away from important areas in some circumstances. An increased level of protection might be needed in buildings where there are other issues with escape times, such as a reduced number of staircases, or where there cannot be natural ventilation.
Pressurization means that air is mechanically introduced (via a fan) into escape routes such as staircases or corridors, which in turn increases the air pressure in the escape routes. The heightened pressure in the escape route area means that air is forced outwards through any possible gaps into the other areas and that therefore, smoke cannot seep through into the escape route itself. In such an environment, it is important that the doors leading to the escape area from other areas are not fitted with smoke seals and that the protected area should have air relief vents as appropriate.
Further guidance on how smoke containment by air pressure works and can be implemented is to be found in BS EN 12101-6:2005 – Smoke and heat control systems. Specification for pressure differential systems.
Smoke ventilation can also be the practice of providing openable windows and vents in the accommodation and stairways of a building, for the use of the Fire Service. In a standard staircase, a vent of sufficient size is provided at the top, whereas in a fire-fighting staircase ventilation should be provided at the top and at each storey landing, or at the final exit if this leads to open air. It is also important that the lobbies leading to the stairway are ventilated too. While ventilation to open air is the ideal, it is not always possible due to building placement or design and in these cases, smoke shafts may be used.
The common aim of such ventilation is to provide safe access to the Fire Service, or to purge the building of smoke following the extinguishing of the fire. In some instances, smoke control is used to assist in the protection of escape routes, this however requires very detailed consideration.
In Part 6 of this series, LWF will continue to look at smoke ventilation, how it works and the practical applications. In the meantime, if you have any queries about your own facilities or wish to discuss this blog series, please contact Peter Gyere in the first instance on 0208 668 8663.
Lawrence Webster Forrest is a fire engineering consultancy based in Surrey with over 25 years’ experience, which provides a wide range of consultancy services to professionals involved in the design, development and construction and operation of buildings.