The LWF Blog
Fire Engineering Design and Risk Assessment – Provision of Firefighting Shafts – Part 49January 20, 2020 11:10 am
In LWF’s Fire Engineering blog series for Architects and others in the building design business, we have been discussing what provisions should be made for firefighting activities. In part 48, we looked at the recommendations for firefighting shafts made in Approved Document B, BS 9999 and NFPA 5000. In part 49, we talk about assessing the provision of firefighting shafts.
In the guidance documents mentioned, different criteria for the provision of firefighting shafts are given which depend upon factors such as the purpose of the building and the height of the uppermost floor. A firefighting shaft may consist of a protected enclosure containing lobbies and a staircase, or if the building is tall, or deep due to basement levels, the shaft may also include a firefighting lift.
It is, however, recommended that access to the accommodation from a firefighting lift or stair must be through a firefighting lobby, as a single fire door is not able to provide adequate protection to the firefighting stair and lift from a fire in the accommodation.
When preparing to tackle a fire on an upper storey of a building, the firefighters attending establish a bridgehead on an unaffected floor below the floor of fire origin, whether they reach the bridgehead floor via the stairs or a lift. The hose line is then deployed from the landing valve through the fire-resisting, self-closing doors into the accommodation where the fire is burning. This means, of course, that the door which is designed to stay close is held open by the diameter of the hose and smoke from the fire will be able to travel into the staircase. This is why firefighting shafts must have ventilation or extraction to the open air. An alternative method is to operate a pressurisation system which stops the smoke from entering.
As has been illustrated, the deployment of a hose line to the floor of fire origin compromises the fire protection between the fire floor and the staircase and with this in mind, it would seem pointlessly onerous to insist that a single fire door cannot provide adequate protection to the firefighting stair from a fire in the accommodation.
In part 50 of this series, LWF will continue to discuss how the provision of firefighting shafts can be assessed. In the meantime, if you have any questions about this blog, or wish to discuss your own project with one of our fire engineers, please contact us.
Lawrence Webster Forrest has been working with their clients for over 25 years to produce innovative and exciting building projects. If you would like further information on how LWF and fire strategies could assist you, please contact Peter Gyere on 0800 410 1130.
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.