The LWF Blog

Fire Safety for Facilities Management Personnel – Means of Escape – Part 119

October 11, 2021 12:12 pm

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 118, LWF discussed Direct Distance before looking at exit capacity. In part 119, we look at the use of time rather than travel distance.

When limiting travel distances along an escape route, what we are really attempting to do is to limit the exposure of building occupants to the effects of fire. A fire engineered solution, therefore, sets out to limit the time a person is exposed rather than the distance. The use of time rather than travel distance is also incorporated into BS 9999.

In a fire-engineered solution, the time required for people to reach a place of relative safety after a fire starts is compared with the time available for escape following fire ignition.

The time required for escape depends on various elements:

  • The time taken to detect the fire – whether by fire detectors or people
  • The time for an alarm to be raised – whether automatic or manual
  • Pre-movement time – when people respond to the sound of the alarm
  • Travel time – time taken to reach a place of relative safety

It should be noted that if a fire is discovered by an individual rather than detected by a fire alarm, the time taken for them to raise an alarm can be variable and dependent on circumstances, abilities, state of mind and many other variables.

Only the final part of the four points above incorporates travel distance. In practice, the time between fire ignition and final evacuation is often governed more by the time for detection and the time taken for people to respond to the alarm signal.

Building occupants do not always take appropriate action to evacuate after hearing the fire alarm, sometimes they discuss it, try to get confirmation that there actually is a fire, finish their phone calls, collect personal belongings or go in search of friends or family members.

Effective fire safety training for staff helps to minimise delays, but cannot eradicate it in visitors to the building.

Extended travel distances may be possible in a fire engineered solution in cases where there is an early warning of a fire through an automatic fire detection system and in environments where there is a high likelihood of a prompt response by building occupants. Equally, active and passive fire protection methods used inside the building can mitigate the additional risk of a longer travel distance as part of a fire safety engineered solution.

In part 120 of this series, LWF will continue to look at means of escape in a fire engineered plan. 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 25 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.

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