The use of Petri nets and a two-zone model for fire scene reconstruction

Fire scene investigation relies on in situ investigation (observations that take place where the fire occurred) and laboratory analysis. Nowadays the role and place of fire modelling in fire forensic investigation are debated within the forensic community. The main objective of this work is to propose a methodology to consider the stochastic aspect of fire development in a specific case by using fire modelling. Therefore, a stochastic fire safety engineering tool so-called SCHEMA-SI (Stochastic Computation and Hybrid Event Modelling Approach-Sécurité Incendie) developed at the CSTB (French Scientific and Technical Construction Centre) has been used to reconstruct a fire scene that occurred in 2007 in a senior care facility situated in the Paris suburb (France). In this case study, several fire scenarios were generated with SCHEMA-SI from probabilistic data in order to perform fire scene investigation. Each scenario is composed on one hand by a succession of dated events and on the other hand by physical quantities time-evolution at different locations in the building (heat release rate, temperature, interface height…). The objective of this work was to find the scenarios which allow getting an acceptable agreement between the calculated values and the observations from the real situation in the fire scene. Among the thousands of fire scenarios generated, 20% were compliant with the fire scene observations. The analysis of these compliant scenarios gave a better idea of what might have happened in the care facility. At the end, the contribution of numerical simulation in a fire scene analysis is discussed.

► We used an original engineering tool for fire scene reconstruction called SCHEMA-SI. ► SCHEMA-SI uses Petri nets and a 2-zone model to compute thousands of fire scenarios. ► These scenarios are then compared to evidences found in a fire scene. ► As a result, only 20% of the scenarios have emerged as consistent with observations. ► Consistent scenarios are analysed to determine what happen during the fire accident.