The LWF Blog

Fire Safety Engineering for Design – Fire Engineering Design Approaches – Part 115

January 16, 2023 11:54 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 114, LWF began to look at the pre-movement time in a fire situation and discussed the first part – recognition time. In part 115, we consider the second part of pre-movement time – response time.

The response time of an individual in a fire situation can be classed as the time between that person recognising the fire alarm or other alert and beginning to respond to them, but before they start to move towards an exit. Along with the recognition time, this time can range from a matter of seconds to however many minutes, depending upon the circumstances.

The response time will involve the cessation of normal activities and an increase in other activities related to the fire emergency. For example:

  • They may look to find out the source of the fire or determine the veracity of the fire alarm
  • They may set about stopping machinery processes or production
  • They may stop to secure money from a till
  • A search may be undertaken for their children or family members
  • Coats and bags may be collected and put on
  • Personal belongings may be gathered
  • They may undertake first-aid firefighting

It should be noted that the listing of potential activities is not exclusive and its inclusion does not apply the activity is appropriate or sensible given the circumstances of a fire. Any delay should be minimised or eradicated where possible and staff fire safety training should address any real issues.

The design approach requires that pre-movement times are estimated and planned for and while it is possible to introduce recognition time and response time to an evacuation model to estimate the total pre-movement time, it can be difficult to do so accurately given the lack of available reliable data and the range of potential behaviours.

Distributions may be derived for total pre-movement time from staged evacuations or the investigation of historical incidents.

In part 116 of LWF’s series on fire engineering we will look at how the design approach can take into account pre-movement times and what factors should be considered for inclusion. 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 since 1986 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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