# Assessment of the Dust in Underground Coal Mine
## 4 Discussion
### Discussion on the Results of Respiratory Dust Measurement  
Assessing the obtained samples, we concluded that the workers of the wall cuttings are subject to the greatest exposure to dust. At this type of workplace, rocks are disaggregated over a large usable area. Every single work activity on the wall cuttings is characterized by high dust generation. The disaggregation itself is performed mechanically. Hence, the biggest contribution to the development of dust concentration is the insufficient rock sprinkling. We propose to carry out revisions of the sprinkling systems of mining shearers by employees of the machine and equipment maintenance. Performed revisions and detected deficiencies must be reported to the supervisor of the given workplace and the shift manager of the machine and equipment maintenance section. The level of staff expertise at the workplace also contributes significantly to the overall dust concentration at the wall cuttings. As there is a very limited number of experienced and trained specialists, there is an increased probability of non-professional, improper setting of the mining bodies of the shearer which results in imperfect separation of the rock with subsequent above-average dust formation. In the case of non-professional handling of the mechanical support, there is insufficient roof coal removal of the wall cuttings, which also results in above-average dust generation at the workplace. We recommend further training of newly hired employees and increasing the periodicity of employee retraining in the field of operating mining shearers and mechanical support. Figure 2: Belt conveyor TP 1000 without sprinkling device. Assessing the samples from mechanical boring, we concluded that the workers of the given workplace experience the greatest exposure to dust during the mechanical disaggregation of the coal seam. The biggest dust producer is the very act of disaggregating the rock. The disaggregation of the coal seam is carried out by the rotary movement of the boring rosette. With greater strength of the coal seam, there is above-average friction between the rosette and the seam and a large amount of dust is generated. In such a case, the sprinkling system of the mining shearer plays a key role. Unfortunately, when collecting samples, we found out that in most cases the sprinkling system was not working. The lack of expertise of the employees also played a significant role in the development of dust concentration. We propose the same measures for mechanical boring as for mechanical mining. Namely, the revision of sprinkling systems with the obligation to report the facts to the shift leader of the machine and equipment maintenance and also the increase in the periodicity of retraining employees for the operation of mining shearers [25; 26]. To protect employees from the impact of SiO\({}_{2}\) on the human body, we suggest conducting a more thorough geological survey of newly bored mine works. When verifying the thickness and structure of the layer, we suggest avoiding boring in the bedrock and in layers with a low energy value. We also recommend avoiding boring through old mine works, as these are already cut-off parts that are mostly covered with bedrock materials. With previous measurements, we pointed out the importance of measuring the respiratory component of dust to protect the respiratory tract of employees. Not only the respiratory component but also dust layers and stirred-up coal dust directly threaten the lives and health of miners. Coal dust, mainly due to its reactivity and small particle size, contributes to decrease of the lower explosive limit of flammable gases. By decreasing this limit, there is a direct threat to employees in the event of an explosion [27]. The leading place as the source of risk in any risk assessment would be occupied by dust layers. Due to the influence of the airflow, it is carried away from the source for long distances, where it settles on the lower part of the mining spaces when the speed of the airflow decreases.