Zone Models

Zone models are simple computer models that divide the considered fire compartments into separate zones, where the condition in each zone is assumed to be uniform. The simplest model is a one-zone model for post-flashover fires, in which the conditions within the compartment are assumed to be uniform and represented by a single temperature. The early one-zone models were developed in 1970s (Pettersson, Magnusson & Thor 1976; Babrauskas & Williamson 1978). Since then, zone models have gone through major development to multi-zones and multi-compartment for modelling localized and pre-flashover fires.

The theoretical background of zone models is the conservation of mass and energy in fire compartments. Basically, the models take into account of rate of heat release of combustible materials, fire plume, mass flow, smoke movement and gas temperatures. They rely on some assumptions concerning the physics of fire behaviour and smoke movement suggested by experimental observation of real fires in compartments. The zone models also model the fire compartments in more detail, compared to that for parametric fires and time equivalence methods. The geometry of compartments, as well as the dimensions and locations of openings, can be modelled easily.

The zone models require expertise in defining the correct input data and assessing the feasibility of the calculated results.

This section will briefly discuss the one-zone and two-zone models.