## 1 Introduction
Currently, calculation tools are capable of analyzing all the elements of interest, even in mines with complex ventilation circuits, such as those that are exploited with the room-and-pillar method. Thanks to the calculation speeds reached by modern computers, it is possible to consider various hypotheses on the following:  
* The location of the fire inside the mine and the ignition typology;
* The quantity and characteristics of the combustible materials that are present;
* Modifications to the ventilation circuit, such as intervening by interrupting the flow in certain areas of the mine by closing doors, putting up barriers, or by modifying the functioning of the primary fans of the mine. A detailed study of this type must lead to the definition of the following:  
* The behavior that miners must adopt inside the mine during a fire;
* The information that safety managers must provide for the ventilation system management and for the action of emergency teams;
* The maximum quantities and locations of the combustible substances that need to be stored underground;
* The monitoring systems of the environmental conditions (e.g., the airflow, temperature, and the air chemical composition in different sections of the mine) in order to be able to identify the start of a fire in time and to control its evolution;
* The alarm signals and communications among the people inside the mine, the personnel involved in the functioning of the main facilities of the mine, the safety managers, and the rescue teams;
* The safety tools that are necessary for attempting to extinguish the fire or to ensure the breathing of the miners during a fire. The application of numerical modeling in the analysis of the evolution of a fire in underground mining voids has already been successfully applied in the past [1; 6; 7; 8]. The same numerical methods were used to understand how the mine ventilation system is able to influence the fire over time. On the other hand, there are no cases in the literature for which numerical modeling has been used to define, in detail, the evacuation plans during an emergency, one which considers the propagation times of the smoke and the fire inside the mine, as well as the routes--with the necessary times--for the escape of the personnel. The safety of the mine, in fact, must be such as to provide all personnel (wherever they operate) with the means to undertake a risk-free escape toward the exit, in the event that a fire develops in any area of the mine. Currently, the development of numerical modeling and the availability of very powerful computers allows one to develop calculations in a dynamic field in an incredibly short time. In addition, the technology is such that the different conditions (such as the entity and position of the fires in a mine) and the evaluation of the results of these calculations are able to be analyzed in detail. In this work, the phases of analyzing fires and air flows inside a mine using modern numerical calculation programs are reported. An application relating to an underground gypsum quarry in the northwest of Italy is then presented and commented upon, with particular reference to the results that are useful for obtaining information on evacuation plans and emergency management during a possible underground fire. The calculation program that was used (Ventsim) is able to iteratively solve the flow and thermodynamic equations that govern a ventilation circuit, such as taking into account the variation in temperature and the gas composition following the presence of a fire, which can evolve over time in defined points of the circuit. The panels of the mine exploitation and the tunnels/shafts are simulated with one-dimensional elements of the ventilation circuit. These elements possess well-determined geometrical characteristics, which must respect [PERSON]'s current law in every instance of time that is analyzed during an underground fire.