The LWF Blog

Fire Engineering Design and Risk Assessment – Fire Safety Management – Part 30

May 26, 2020 11:56 am

In LWFs Fire Engineering blog series for Architects and others involved in building design, we have been looking at those activities of a company which can be classed as fire safety management. In part 29, LWF looked at the content of fire emergency plans. In part 30, we discuss evacuation management.

Typically, within a small, simple building, most fire alarm systems will be configured to operate as a ‘single stage’ operation. This means that when a call point is activated or a detector detects smoke, all alarm sounders within the building are triggered to operate at the same time, thereby indicating the necessity for immediate evacuation.

In large or complex buildings, the option to have a staged or phased alarm and evacuation procedure may be more suitable. In this circumstance, the operation of a call point or detector gives alarm sounder warning for evacuation in the zone or storey affected (and typically the floor above), and sends an ‘alert’ warning signal to the remainder of the building. It should be noted that a staged or phased evacuation will require additional building fire precautions.

The areas of the building which have not yet evacuated can continue to operate as normal, however they will continue to receive the alert warning. Some stages systems are manually escalated, i.e. the decision to evacuate is taken by the management or the Fire Service, however the majority are automatically escalated to ensure that occupants are not held within the building for excessive periods.

For systems of this type to work effectively, it is important that sufficient means of communication are in place to serve the storeys or zones contained within the building. This will typically be a voice alarm system, which is used to control the evacuation process instead of standard alarm sounders.

A phased evacuation can be undertaken, in which the different parts of the building are evacuated in a controlled series of phases. Initially, the fire-affected storey or zone and floor above would be evacuated (in addition to any basement levels and the ground floor), and following on from that, the remainder of the building in stages. A phased evacuation system requires at least a two-stage alarm system capable of giving ‘alert’ and ‘evacuate’ signals, or ‘staff alarm’ and ‘evacuate’ signals. Most commonly, a voice alarm system is used.

In a building designed for phased evacuation, the escape stairs will have been designed specifically for phased evacuation, with the evacuation process being coordinated from a fire control centre where the person responsible will direct the process through the use of a public address/voice alarm system and colour CCTV where appropriate.

In part 31, LWF will continue to discuss evacuation management and will touch on horizontal evacuation, before beginning to look at management of a fire emergency. 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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