Comments by GC Miles, Fire Engineering Consultant

Prescriptive: These are experience based. They are based on the experience of Britain in the Second World War. Generally they consider burnout of the whole compartment, because in those days fire suppression and intervention techniques had not been developed much past the fire hose stage.

Probabilistic: This a statistical approaches to fire safety in Buildings. This is where the likelihood and severity of fire starts is related to the size and function of the building in question. It will be covered in the forthcoming BS 7974/7 and is an important part of fire engineering

Fire Engineering: This is the application of science to fire safety judgements, BS 7974 Parts 1-6. It is termed deterministic as there is a definite causal relationship between a given set of assumptions and the likely outcomes in the event of a fire. It also encompasses the life of a building and its conditions of use. This leads in to Risk Assessment. The causal relationships are equations relating fire parameters and typically allow predictions of the following relevant events:

-Ignition time
-Detection time
-Alarm time
-Recognition time of danger
-Pre-movement time for escapees
-Evacuation time
-Approach time for tenability limits for breathing
-Approach time for visibility limits for escape
-Time to flashover and ventilation control
-Time for suppression devices to deploy
-Time for damage to property to become significant
-Time for Brigade to intervene and control situation