This is one of the most important aspects of underground mining to ensure safe mining. 📍 Basic objectives of mine ventilation systems: (1) To provide airflows of sufficient quantity and quality to provide oxygen in the working area. (2) To dilute contaminants(hazardous gases and dust) to safe concentrations and remove them from the mine. (3) To ensure the appropriate quality of the composition of the atmosphere within the mine, in terms of oxygen content and dilution of noxious gases. (4) To ensure sufficient climatic conditions, in terms of temperature and humidity. 📍 Origins of gas mixtures present in mining operations : 1- Endogenous origin : gases contained in the reservoir and/or in the surrounding rock before exploitation. The composition of these gas mixtures is linked to the nature and geological environment of the materials extracted.These gases are continuously released during mining, through an expansion mechanism, and migrate into the atmosphere of the underground workings. 2- Exogenous origin: these are gases produced by specific chemical reactions during mining activity. Most often these are carbon monoxide and dioxide produced by the oxidation of certain ores and hydrogen sulphide produced by the decomposition of sulphurous materials such as wood; various gases linked to the use of explosives and combustion engine machinery. 📍Ventilation principle for underground mines. The general principle is to supply fresh air in sufficient quantities to all parts of the mine that are still active, and to evacuate used air to the surface. Mine ventilation is classically achieved through : (1) A main ventilation system that ensures the continuous introduction of atmospheric air and the discharge of used air to the surface via the return structures (shafts). The air circulation is ensured by main fans of variable power and flow installed on the inlet or return structures. The main ventilation system is most often suction, more rarely blowing. (2) Secondary ventilation, which recovers fresh air from the main ventilation circuits and provides local ventilation in specific areas. This is achieved by means of secondary fans and circulation ducts. 📍Elements of mine ventilation systems: + Interconnected airways and working zones within the mine. + Connections to the surface. + Fans to produce airflow. + Control devices to ensure that the air courses around the mine as required. 📍Main factors in sizing ventilation - Geometry of the mining network; - Mining method and method of blasting (by explosives or mechanised); - Nature and volumes of gases present (mineralogical and geochemical characterisation of the deposit and surrounding rocks); - Number of people employed.