There are a number of different ways to analyse evacuation of buildings. Standard fire safety guidance documents typically specify the width of exit routes (such as doors and stairs) based on the number of occupants. Some, more sophisticated documents, such as BS 9999, also incorporate factors such as the occupant characteristics and the fire risk within the building to modify those figures. These techniques are useful, simple approaches that give reasonable results for most buildings.

However, in certain situations it is necessary to predict the amount of time needed to evacuate a building (in fire engineering, this is referred to as the Required Safe Egress Time or RSET). This can be used in combination with smoke modelling, which can predict the time available before untenable conditions are reached (knows as the Available Safe Egress Time or ASET).

The combination of these techniques is often useful in unusual or complex buildings where the standard design guides would be inappropriate or compliance is impractical to achieve. By demonstrating that the evacuation is complete well before untenable conditions occur (i.e. the RSET is shorter than the ASET), ASEC engineers are capable of demonstrating that building designs are safe for occupants.

ASEC have extensive expertise in evacuation modelling, and in combining the results with smoke modelling as part of a fire strategy for almost all types of buildings.