The LWF Blog

Fire Safety for Facilities Management Personnel – Smoke Control – Part 258

June 24, 2024 10:42 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 257, LWF talked the spread of smoke. In part 258, we continue discussing smoke containment by physical barriers.

The simplest means of containing smoke in an area is the use of physical barriers to its passage – walls and partitions. In a situation where all partitions enclosing a corridor extend to the level of any false ceiling or beyond, then smoke movement can be prevented in the early stages of a fire.

As the fire progresses and grows there is a need for the partitions to be fire-resistant, so that the smoke-control function can continue. Any penetrations in barriers, such as cabling, services etc. coming through a wall or partition should be adequately fire-stopped at the time of installation and maintained over time. This will help to ensure that smoke cannot pass through any gaps around the services.

Fire-resisting walls need to make contact with the underside of the structure above any suspended ceiling. To stop a fire-resisting wall at suspended ceiling height would simply channel the smoke (and possibly the fire as it spreads) in that direction.

Apertures in fire-resistant walls, such as doors should be fitted tightly in their frames to assist in limiting smoke spread in the early stages of a fire. Should a fire develop in the space, a pressure differential will be created between the space with the fire and the space beyond the door. This can result in smoke passing through gaps around the door and, therefore, the gaps should be minimal. A typical gap for a door in a frame needs to be no more than 3-4 mm.

Any door that is designed specifically to resist the passage of smoke should be fitted with smoke seals. As a fire develops and grows, any door expected to continue to resist smoke passage should be fire-resisting, which means they should have combined intumescent seals and smoke seals. Fire resistant doors are rated in the following manner – FD 60, which means a fire door with 60 minute resistance.

As some smoke leak is inevitable around a door, the fire design should consider two doors between the fire and the protected area, depending on the level of resilience required. This can protect an area such as a lift/stair lobby, single direction escape route or a fire-fighting staircase. In some cases, it is necessary to provide ventilation in the lobby to afford additional protection.

In part 259 of this series, LWF will discuss smoke containment by pressurisation. 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.