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Fire Safety for Facilities Management Personnel – Means of Escape – Part 120

October 18, 2021 11:54 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 119, LWF discussed the use of time rather than travel distance when designing means of escape provision. In part 120, we continue to look at means of escape in a fire engineered plan.

A critical factor in managing escape from fire is the time between ignition and evacuation. Early warning of a fire and an immediate response from building occupants can reduce the time taken dramatically. The time between ignition and evacuation only has true relevance in relation to the time between ignition and conditions in the escape route becoming untenable. Untenability in this instance indicates a significant hazard to life.

The ‘available safe egress time’ (ASET) is dependent on the rate of fire growth and the active and passive fire protection provision afforded to escape routes. An active fire protection provision might be sprinklers, a passive one might be self-closing fire doors and fire-resistant construction.

Certain building conditions and environments can mean that there will be more ‘available safe egress time’. A building with very high ceiling heights is likely to maintain tenability of conditions in the escape route for longer than a building with low ceiling heights, where the hot smoke layer will sit at a level the building occupants will come into contact with.

Equally, some functions and processes of a business are intrinsically more fire safe than others. A lack of fuel in the form of flammable stocks means the fire will not be able to grow as quickly as it would in a warehouse stocking rolls of flammable material.

The limitation of distance to be travelled in a fire situation to a place of safety is not always adequate. The design and layout of the interior is very important when everybody in a building is asked to leave it at the same time. In a small or crowded environment where a single, narrow exit door is provided, this can be dangerously insufficient and prevent occupants escaping safely within the ASET, despite being within an appropriate travel distance of the exit.

It is vital that the number and width of stairways and exits is sufficient for the potential number of building occupants.

In part 121 of this series, LWF will continue discussing means of escape. 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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