The LWF Blog

Fire Safety Engineering for Design – Means of Escape Design – Part 100

September 26, 2022 10:21 am

LWF’s Fire Safety Engineering blog series is written for Architects, building designers and others in the construction industry to highlight and promote discussion on all topics around fire engineering. In part 99, LWF considered the design and provision of alternative exits for means of escape based on criteria such as distance to be travelled and predicted occupancy. In part 100, we look at travel distances and how escape routes are protected with fire protection measures.

Travel distances are described in fire safety design codes as the maximum distance to be travelled by a building occupant to an exit. The travel distance must be measured as it would be walked, along the exit route and not in a straight line from one point to the exit.

Prior to the inside layout being planned for a building, the direct route from one point to the exit can be multiplied by 1.5 to give an approximation of the travel distance, which can be useful at that point in time.

Recommended maximum travel distances vary per occupancy type and also jurisdiction in which the project is built.

For example, the maximum recommended travel distance where escape is available in one direction only, for shops and commercial buildings is 18 metres according to ADB Volume 2, 15 metres from the Technical Handbook (Non-Domestic) and 23 metres from NFPA 101 (The US standard).

BS 9999 is the code of practice dealing with fire safety in the design, management and use of buildings. It allows for a risk-based approach to means of escape and travel distances which may allow longer travel distances than those prescribed in ADB Volume 2. The risk-based option is based on the geometry of the building and also the level of building management.

Fire protection measures for escape routes

Stairs on an escape route and some escape corridors need to be enclosed with fire-resisting construction to help prevent the passage of smoke and fire products into the escape route. A minimum fire resistance period of 30 minutes is recommended in most cases, although this may need to be increased in certain instances, for example, if the stairway also acts as a protected shaft providing separation between levels.

To help with preventing the ingress of smoke into protected escape routes, all elements should be sealed against smoke and doors should be fitted with smoke seals.

In part 101 of LWF’s series on fire engineering, we will continue to discuss fire protection measures for escape routes, starting with protected lobbies. 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 the LWF office 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.

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