Many ore mines that have an active aerodynamic connection of underground workings with the surface through the caving zone are ventilated by the injection-suction method. In this method, by regulating the operation of the suction and discharge fan, it is possible to create in the area adjacent to the caving, the so-called zone of zero depression. In this zone, the effective depression is extremely low, so there should be neither air suction from the surface nor air escape from the mine to the surface. The actual large size of the caving area and the occurrence of local natural draughts do not allow for the complete elimination of air movement through the caving. Air may move upward in one part of the caving and downward in another, but in much smaller quantities than with a single fan. Thus, the zero-depression zone created by the blower-suction method of ventilation serves as a measure to control air suction through the caving zone. At mines in the northern regions, the position of the zero depression zone plays an important role in improving the atmospheric conditions of these mines, reducing the entry of cold air from the surface ...

Recently the methods of calculation of methane emission based on the value of natural gas content of coal are becoming more and more widespread. This is the result of numerous studies in the field of methane emission in coal mines carried out in our country ...

Methane emission within the extraction panel depends on the operation of mining machines, atmospheric pressure fluctuations, collapse of the main roof rocks, non‑uniformity of air supply, etc. Regardless of the influence of these factors, the methane content in the outgoing air stream of the panel should not exceed 1%. Consequently, it is necessary to supply to the panel such amount of air Qcalc that would ensure compliance with the requirements of the Safety Rules for any combinations of these factors.

The Pechora Coal Research Institute has established that the mines of the Vorkutskoye field are characterized by high methane abundance, which increases with the transition of mining operations to deeper horizons. However, the methane content of the mine as a whole, determined by the mining‑statistical method, cannot characterize the value of methane emission, for example, in stoping and preparatory faces under different mining and geological conditions. For example, gas emission within the limits of a stoping area when developing a single seam, a seam with satellites or a seam developed in two seams will be sharply different. Because gas emission at greater depths will create significant difficulties in ventilating the workings and may require special measures to control gas emission, it is necessary to have a clear understanding of the nature of gas emission under different mining and geologic conditions.