# Assessment of the Dust in Underground Coal Mine
## 2 Materials and Methods
The main ventilation exhaust works usually ranged from 10 m\({}^{2}\)-14 m\({}^{2}\) depending on the reinforcement, subsoil, or superstructure in which they were built. The airflow volume is largely influenced by the mine's ventilation system. Decree 21/1989 [6] states that ventilation of the mine must be ensured by at least one main intake mine work and at least one main exhalation mine work. At least one horizon of the intake mine work must be excavated at the level of the lowest mined point of the given mine. The lowest horizon of the main exhalation pit must be bored at the level of the uppermost excavated horizon of the given mine. This method ensures natural ventilation when the main fans fail. However, the decree further states that the ventilation of the mine for permanent operation must be continuous, induced artificially, and with negative pressure. It also states that on the main exhaust pit, this ventilation must be provided by a pair of main fans, where one is in operation and the other in backup, and they also have replacement fans of the same performance located in the same fan station. They must also be capable of switching automatically and ensuring the reversal of mine winds. This ventilation system provides the advantage that the induced vacuum of the main fans pulls gaseous pollutants from the rock massif or old mine work. With the failure of the main fans and the fact that the barometric pressure is higher in the mine, the barometric pressure in such a failure pushes gaseous pollutants into the rock massif or old mine works. The volume of airflow was measured roughly once every three days, and the measurement of airflow needed for the ventilation balance was done twice a month. Respiratory dust measurements at the wall cutting were undertaken based on an internal request from the Production Management Unit and a request from the Occupational Health Service based in Bojnice in January 2023. The measurements were carried out on mechanized cutting of 111 021-95 of staff team X1 and the mechanized boring in the corridor 111 123-05 of staff team X2. Two CIP 10 devices were used for the measurements, attached to the 2 employees in the breathing zone. CIP 10 devices ATEX have CIP-R inlet and 10 L per min sampling flow rate. Dust exposure to employees of individual work operations or the total dust concentration of the workplace was measured with the given devices. These are devices that, based on a magnetic field, attract dust particles directly to the measuring zone of the device. The device captures these particles. The measurement output is the amount of captured dust particles per monitored time--in our case, this was a 9.5-h work shift in mine operation. Measurements were made over a long period of time and in continuous operation to capture all work operations at the given workplace. Therefore, we could express measurements for an average workplace occupation by individual employees. Subsequently, we took the captured amounts of dust from individual measurements from the devices, which were only quantitatively weighed and stored. After the measurement, there were calculated average amounts of dust captured on the dust meter, the airflow volume passing through the workplace, and the length of the work shift. After this evaluation, the samples were sent to testing laboratories to determine the siliceous components in the given sample [7; 13; 14]. Samples from the devices were collected at shift intervals and submitted to SLUBN. Under SLUBN test laboratory conditions, the total specific gravity of dust and its respiratory fraction were measured at the active workstations in question. The results found after seven measurements were sent by SLUBN to the Occupational Health Service in Bojnice for evaluation. Specific samples were subsequently sent to the chemical laboratories in Ostrava to detect the presence of SiO\({}_{2}\). For the respiratory component and also for the measurement of total dust concentration, the measurements were given in units of mg\(\cdot\)m\({}^{-3}\).