The determination of natural gas content in coal seams is essential to safe mining activities and to estimate gas resources. It is used to estimate methane emissions into workings, which is very important when using preventive measures of methane ignition and explosion. Methane content in a coal seam is mostly determined using a direct method. However, a problem with estimation of gas loss during collecting a sample in a mine occurs in each method. That gas loss is estimated using different procedures. In the Polish mining industry, methane content in a coal seam is mostly determined during roadway advancing faces in coal seams. The differences in procedures for determining methane content in coal in various laboratories gave rise to starting research into developing a new method. This article presents results of study of gas loss unification for the determination of methane content in coal seams. The research focused mainly on determining a uniform method for estimating gas loss using the early adsorption diffusion process. The method of coal sample saturation with methane was used to measure gas desorption rate. Saturation pressures of samples were determined for coal seams in the Upper-Silesian Coal Basin. The analysis of desorption results allowed to determine the dependence between methane content in a coal sample and the initial methane content in a coal seam. It was concluded that the desorption rate was highest within two minutes. For the procedure of coal sampling, gas loss was determined at 12% of both desorbed and residual gases. The presented research results gave rise to developing a uniform method for determining gas content used in Polish coal mining. The method was accepted as the national standard. Methodology using a new gas loss estimation procedure allows for achieving relatively fast results of the determination of methane content in coal seams, which is very important, especially in gassy mines.

The determination of methane content of coal seams is conducted in hard coal mines in order to assess the state of methane hazard but also to evaluate gas resources in the deposit. In the world’s mining industry, natural gas content in coal determination is usually based on direct methods. It remains the basic method in Poland as well. An important element in the determination procedure is the gas loss that occurs while collecting a sample for testing in underground conditions. In the method developed by the authors, which is a Polish standard, based on taking a sample in the form of drill cuttings, this loss was established at a level of 12%. Among researchers dealing with the methane content of coal, there are doubts related to the procedures adopted for coal sampling and the time which passes from taking a sample to enclosing it in a sealed container. Therefore, the studies were designed to evaluate the degree of degassing of the sample taken in the form of drill cuttings according to the standard procedure and in the form of the drill core from a coal mine roadway. The results show that the determinations made for the core coincide with the determinations made for the drill cutting samples, with the loss of gas taken into account.

Underground excavations in which an airflow is present are affected by both natural and technological sources of heat. As a result, the air flowing through the mine excavations is characterised by high temperatures, which—combined with high humidity—causes microclimatic conditions to deteriorate. Bad microclimatic conditions affect miners underground, causing a reduction of perception, concentration, attention, and perceptiveness. This negative influence of temperature and humidity on the human body is referred to as the climatic hazard. For this reason, the design of ventilation and air conditioning systems to be implemented in underground mining plants is an issue of increasing significance. This article investigates the performance of cooling systems in the Polish hard-coal mining industry. Based on the conducted research on air-cooling installations in six hard-coal mines, the actual efficiency of air-cooling is presented. The calculated values of cooling power were compared with the design intent. The obtained results have allowed identifying with greater precision the factors that diminish the efficiency of cooling systems in the mining plants under analysis. These factors may be treated on equal terms with key performance indicators (KPIs), which can be used to monitor the performance of cooling system components and to provide managers with high-level indicators on which decisions can be based.

Methane has a bad influence on safety in underground mines as it is emitted to the air during mining works. Appropriate identification of methane hazard is essential to determining methane hazard prevention methods, ventilation systems and methane drainage systems. Methane hazard is identified while roadways are driven and boreholes are drilled. Coalbed methane content is one of the parameters which is used to assess this threat. This is a requirement according to the Decree of the Minister of Economy dated 28 June 2002 on work safety and hygiene, operation and special firefighting protection in underground mines. For this purpose a new method for determining coalbed methane content in underground coal mines has been developed. This method consists of two stages - collecting samples in a mine and testing the sample in the laboratory. The stage of determining methane content in a coal sample in a laboratory is essential. This article presents the estimation of measurement uncertainty of determining methane content in a coal sample according to this methodology.

Methane drainage is used in Polish coal mines in order to reduce mine methane emissions as well as to keep methane concentration in mine workings at safe levels. This article describes methods of methane drainage during mining used in Polish coal mines. The first method involves drilling boreholes from tailgate roadway to an unstressed zone in roof or floor layers of a mined seam. It is the main method used in Polish mining, where both the location of drilled boreholes as well as their parameters are dependent on mining and ventilation systems of longwalls. The second method is based on drilling overlying drainage galleries in seams situated under or over the mined seam. This article compares these methods with regard to their effectiveness under mining conditions in Polish mines. High effectiveness of methane drainage of longwalls with different ventilation and methane drainage systems has been proven. The highest effectiveness of methane drainage has been observed for the system with overlying drainage gallery and with the parallel tailgate roadways. In case of classic U ventilation system of longwall panel, boreholes drilled from the tailgate roadway behind the longwall front are lost.

The article compares the climate conditions in an excavation with thermally insulated roof and sidewalls to the conditions when such insulation is absent. The analysis of the temperatures presented in the article consisted of limiting the heat transfer from the rock mass to the heading in one of the Polish coal mines. It is widely believed that the thermal insulation of heading sidewalls, through which fresh air is supplied, can substantially improve climate conditions. The article’s objective is to evaluate the impact of thermal insulation on the surface of the roof and sidewalls on the reduction in heat transfer from the strata with a high virgin temperature to mine air. Preventing the existing climate hazard involves higher costs of coal extraction, whereas the consequences of inadequate prevention threaten the health or life of the miners.