## 1 Introduction  
Fires are one of the most critical risks that must be considered in underground mines. Despite significant efforts made in recent years regarding prevention and control systems, the frequency of mine fires does not appear to have decreased. This is likely due to newly introduced materials, the presence of large quantities of fuels, and ever-increasing mechanization [1, 2]. Among the most serious mining disasters, many are due to fires inside underground mines, possibly accompanied (either preceded or followed) by explosions of various types due to the presence of methane gas or explosive dust. In particular, among the 10 most serious mining disasters in history, 4 were caused or contributed to by a fire inside the underground mine (URL [[https://www.amsj.com.au/](https://www.amsj.com.au/)]([https://www.amsj.com.au/](https://www.amsj.com.au/)) (accessed on 5 December 2022)): Benxihu colliery, Liaoning (China), April 1942 (1549 deaths); Laobaidong colliery, Datong (China), May 1960 (682 deaths); Senghenydd Colliery, Caerphilly (Wales, UK), 14 October 1913 (440 deaths); and Wankie Coal Mine, Hwange (Zimbabwe), June 1972 (426 deaths). The leading cause of the loss of life in a mine fire is found in the miners' inhalation of toxic gases, mainly carbon monoxide [3]. In fact, during a fire, the people who are present in the mine must evacuate to a safe place [4]. However, the path to be taken can also be very long, and the possibility that the fumes or high air temperatures that the personnel on the escape route or in the work site will encounter is not remote. The analysis of the ventilation of a mine during a fire plays a crucial role. The flow of air and, therefore, of oxygen that reaches the fire affects its behavior. However, the increase in air temperature and the physical characteristics of the produced gases also modify the ventilation circuit in those relevant zones of the mine. From an analytical point of view, it is possible to simulate the fire in an underground cavity with a linear development using simplified calculation methods. When knowing, in fact, what thermal power is reached by the fire in a determined time t from the initiation, it is then possible to determine the temperature of the air that is downstream of the fire, as well as the characteristics of the flow (e.g., pressures, speeds, and flow rates). Such a simplified approach is generally applicable to underground voids with a linear or simple development. This can be achieved by introducing certain simplifying assumptions, such as the total absence of heat exchange with the surrounding rock mass. For the purposes of evaluating, in detail, the evolution of a possible fire and the path of the fumes over time, it is necessary to resort to numerical modeling [5; 6; 7; 8]. Through doing this, all the influential elements are considered, such as the characteristics and quantities of the combustible materials that are present; the amount and type of produced fumes; the entity of the emitted thermal power; the characteristics of the ventilation circuit; and the type and functioning of the mine fans. When conducting a numerical model, it is essential to understand the following:  
* The time required to ensure securing the miners. This should be understood in order to plan the monitoring system, as well as to plan the communication between the safety managers and the workers in the underground levels;
* The evolution of the fire and the possible involvement of the mine areas upstream and downstream of it; this information is helpful in guiding the action of emergency teams to rescue people or to fight the fire in order to contain or extinguish it;
* The usefulness of a possible intervention with the ventilation system, to enhance the airflow or even to interrupt or reverse it; the choices are challenging to make because they should depend on the knowledge of the chemical-physical and thermodynamic conditions of the fire, as well as an assessment of the position of people and the combustible materials in the mine.