The complexity in the analysis of fire evolution requires many years before the complete definition of a device able to simulate and predict them behaviour. Since the evolution of numerical simulations, there was the necessity to create a software able to analyse critical conditions generated by fire studying how control it. Many aspects must be considered such as the reaction of the species or the effects of the external environment on the fire itself because they can change its evolution in time. The case study considered in this research is the Frejus tunnel. It is one of the longest transalpine tunnels with a transversal ventilation system due by its length.