The LWF Blog

Fire Safety for Facilities Management Personnel – Smoke Control – Part 260

July 8, 2024 10:39 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 259, LWF discussed smoke control by talking about smoke containment by pressurisation. In part 260, we begin to talk about smoke ventilation.

It is considered normal to provide openable windows in accommodation and staircases to act as smoke ventilation. An alternative to openable windows with most staircases is placement of a suitably-sized vent at the top.

In the case of firefighting stairways, ventilation at the top and at each storey, or ventilation at the top and a final exit to open air at the bottom should normally be provided, unless the staircase is pressurised. The ventilation provided will be controlled by attending firefighters.

The lobbies to stairways should also be provided with ventilation facilities, which may be openable windows where possible, or smoke shafts may be provided.

The ventilation options installed are not intended to aid means of escape, but rather to be of assistance to the fire and rescue service at a stage following evacuation. Ventilation is to provide a smoke-free access route to the fire service, or to clear the building of smoke after the fire is extinguished.

In large-volume warehouses of single storey, and similar, smoke ventilation is provided as an aid to the fire service in order to keep the smoke layer at a sufficient height. This allows better visibility at head height and below.

Ventilation facilities usually comprise vents which operate automatically when a fusible link melts. However, there are also smoke vents that operate when the smoke detection system is activated or by manual controls.  Powered smoke extraction may also be an option, but the installation would require reliable power supplies, fire-protected wiring and fans that can withstand high temperatures. Powered extraction will, however, operate whatever the external wind pressures may be, whereas natural ventilation is susceptible to wind simply blowing the smoke back into the area.

Not all smoke ventilation systems are employed for post-evacuation purposes. In large shopping centres, for instance, ventilation systems with powered extraction may be required to maintain a smoke-free area at head height and below during evacuation of the centre. The same applies to large single-storey retail premises and in situations where the footprint of the building is sufficiently large to preclude normal travel distances for evacuation.

In part 261 of this series, LWF will continue to discuss smoke ventilation in terms of atrium buildings. 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.