The LWF Blog
Facilities Management & Fire Safety – Smoke Control – Part 4October 26, 2017 12:16 pm
In LWF’s blog series for those who work in Facilities Management or who have an interest in or responsibility for fire safety, we have been recently looking at smoke control. In Part 3 of the series, some of the objectives of smoke control were outlined along with the two main methods of achieving control – containment or ventilation. In Part 4, we will look at how physical barriers work to control smoke.
Smoke containment can be achieved by building smoke control measures into a building at the design stage. These are fundamental measures such as walls and partitions. A corridor, for example, can contain smoke if the walls enclosing the corridor extend up to at least the level of any false ceiling and beyond to the underside of the structure above a suspended ceiling.
As a fire progresses, the heat means that the partitions must be fire-resisting in order to continue to provide smoke blocking or fire blocking functions.
The effectiveness of fire-resistant partitions in a build is subject to a certain level of understanding on the part of the building owner, occupier and any trades who are asked to work on or in the building. For instance, the passage through fire-resistant surfaces of any service – pipework, ducts, leads and cables – must be undertaken by only those who understand the necessity of any penetration being subject to fire-stopping, to prevent the leakage of smoke through any gaps, or the passage of fire from one compartment to the next.
If all non-avoidable apertures are fire-stopped, then we must turn our attention to the next possible passage of smoke from one area to the next – doorways. A tightly fitting door can assist in stopping the passage of smoke through any gaps around the door itself. However, as the fire develops, a pressure difference between the smoke-filled area and the clear air beyond the door builds and can result in smoke passing through the gap around the door. A standard door therefore should have a gap of no more than 3 or 4 mm.
A door which is designed to stop the spread of smoke should be fitted with smoke seals and in cases where it is necessary for the door to control smoke or the spread of fire for any duration, it should be a fire-resisting door. Such doors are indicated by the code FD30 or FD60 which allow 30 or 60 minutes fire-resistance.
A two-door separation principle is often used, whereby two doors are used in a corridor, for instance, creating a lobby as an additional buffer against the spread of smoke. This is especially common in the area before an escape or fire-fighting staircase and can be used in combination with ventilation of the lobby to provide additional protection.
In Part 5 of the series, we will look at smoke containment by pressurization. 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.