The LWF Blog

Means of Escape Series | Part Two – Effective Evacution

March 26, 2014 11:33 am

This short blog series looks at fire safety in terms of means of escape; how building evacuation in case of fire should be considered at the earliest opportunity – during the design of the building. The intended use of the building and its likely occupancy was discussed in the first of this series and this second blog looks at design of the escape routes themselves and methods of evacuation.

Consideration of the following areas will help to guide your fire evacuation design:

Travel distance

Travel distance is defined as the actual distance to be travelled by a person from any point within a floor area to the nearest storey exit, having regard to the internal layout of walls, partitions and fittings. The travel distances vary with the type of premises under consideration and can be found in Approved Document B (ADB).  

All buildings are different and present different degrees of fire risk based on their type. As such, the  travel distances allowed in offices are higher than those allowed in enclosed plant rooms. 

It is common within existing premises which were designed prior to the application of current design standards, and also in the design of new buildings, that travel distances are in excess of that recommended by the Building Regulations – ADB. These non-compliances must therefore be justified and compensated for using a fire engineering approach.

Width of escape routes

The width of escape routes and final exit doors is an additional element in the design of means of escape. The escape width is the driving factor which determines the evacuation flow of people through a door, corridor and stair. Approved Document B provides guidance on the escape widths to be used, based upon the number of occupants to evacuate.

Simultaneous and phased evacuations

Most buildings in the UK are designed for the simultaneous evacuation of their occupants. This strategy requires the means of escape to be designed accordingly and can physically allow for the safe evacuation of the maximum number of people who are calculated to be present in the building at any one time.

As a different type of strategy, a phased evacuation may be adopted. In a phased evacuation situation, the first people to be evacuated are those with reduced mobility and those people occupying the storeys directly affected by the fire – usually the floor of fire origin and the floor above.  This is commonly the case in high rise and residential buildings. 

Healthcare premises have a similar strategy, whereby the phased evacuation is based on a compartment by compartment basis, with ‘Evacuation’ and ‘Alert’ zones. When adopting a phased evacuation strategy, the maximum number of people to be evacuated at any one time is limited compared to simultaneous evacuations. 

This short series on evacuation design will continue next week with the third and final part – Fire engineering solutions.

In the meantime, if you would like to discuss this blog further, or would like our input on your project, please call Peter Gyere on 020 8668 8663.

LWF are fire engineering and fire risk management consultants with over twenty five years experience in the development of fire engineered technology and the application of fire safety standards including fire engineered techniques.