Parameters that affect tenability conditions during fire emergency in metro tunnels

Underground spaces are characterized by special conditions and complexity, as well as by severe consequences in the event of an accident. Although the frequency of fire accidents in tunnels or metro stations is low, in worst cases they may lead to severe fatalities and damages. In order to have a more accurate prediction of fire impacts, most safety standards enforced worldwide suggest the development of special risk analyses. This needs to be made having in mind fire characteristics, geometrical and ventilation parameters so as to have an accurate view of the thermal and smoke propagation within the underground space. In this paper a parametric analysis is carried out, varying input values, crucial for fire risk analysis, like fire curve and heat release rate maximum (HRR max ), as well as ventilation and tunnel geometry. Key factors like visibility conditions, temperature and CO concentration are recorded through the fire dynamic simulation (FDS), in order to determine the conditions inside the metro tunnel. Furthermore, the fractional effective dose (FED) that occupants might receive in a period of time, in different positions inside the tunnel, is calculated. Based on the above, detailed data on the prevailing conditions are gathered and conclusions can be drawn regarding the influence of each parameter’s evolution on the tenability conditions inside the tunnel. Hence, the analysis can illuminate key issues to consider for performing an accurate risk analysis in an underground environment.