## 3 Results and Analyses
Contrary to our study, it was mineral dust; the filtration conditions also differed and did not apply to the conditions encountered in the furniture factory. The tests used a filtration speed of \(\mathrm{w}_{\mathrm{f}}=10\) cm\(\cdot\)s\({}^{-1}\) and a maximum pressure drop of 980 Pa, followed by a cleaning pulse. The quantity characterizing the pressure drop was thus the time interval between the pulses. The method of cleaning filter bags depending on the pressure drop is, in this case, different from that used in the filter dust collector in a furniture factory, from where the test bags were collected, where the cleaning pulse is applied at equal intervals regardless of the value of the pressure drop. This difference is very important from the point of view of the obtained data and makes it impossible to compare the results. As a result of the experiment, a differentiated mechanism of dust layer formation on the surface of the filter material was established, clearly indicating a significant influence of the type of non-woven fabric used in the course of the filtration process. However, due to the considerable differences between the experimental conditions and the filtration conditions used in the furniture factory, the results of this experiment are not entirely suitable for describing the phenomena occurring during the filtration of wood dust. Comparing the properties of various filtration nonwovens under the same filtration conditions was the aim of the studies by [PERSON], [PERSON], and [PERSON] (2016) [26]. Three types of filtering nonwovens were tested (polyester with a thermally treated surface, a filter with a PTFE membrane, and a filter with a polyester hydrophobic layer) that filter coal dust and operate at various airflow velocities. Among the velocities used, the closest  
Figure 5: The value of the K\({}_{2}\) coefficient depends on the working time and the type of bag. to that used in a furniture factory was 3 cm\(\cdot\)s\({}^{-1}\). The applied nonwovens had a similar basis weight, from 240 to 260 g\(\cdot\)m\({}^{-2}\). The airflow resistance through the clean non-woven fabric showed significantly different values for non-woven polyester with a thermally bonded surface of 8.91 Pa\(\cdot\)s\(\cdot\)cm\({}^{-1}\), a filter with a PTFE membrane of 42.57 Pa\(\cdot\)s\(\cdot\)cm\({}^{-1}\), and a filter with a polyester hydrophobic layer of 19.93 Pa\(\cdot\)s\(\cdot\)cm\({}^{-1}\). As a result of the research, a different value of the dust layer resistance during filtration was found, reaching values for the velocity of \(\mathrm{w_{f}}\) = 3 cm\(\cdot\)s\({}^{-1}\) and K\({}_{2}\) = 1.0 \(\times\) 10\({}^{-8}\) Pa\(\cdot\)s\(\cdot\)m\({}^{-2}\). It was undoubtedly influenced by different values of initial resistances and air properties. Because the experiment did not concern wood dust, the results cannot be used to describe phenomena occurring during filtration in furniture factories. The properties of the filter media used were also different. The primary conclusion that should be noted here is that the properties of the dust layer on the surface of the filtering material are differentiated by the value of the adhesion force to the filtering surface, which is different for each type of non-woven fabric. The dust on the polyester non-woven fabric with the thermally treated surface had the highest adhesion value. Earlier studies also showed that during the filtration of wood dust, thermal treatment of the surface of the filter material resulted in lower airflow resistance through the non-woven fabric [29]. The issues related to the influence of the surface finish of the filter fabric on the phenomena occurring during filtration were also the subject of studies by [PERSON] and [PERSON] (2015) [27]. They focused on comparing the filtration efficiency of polyester filter fabrics with and without a PTFE membrane. The experiment was conducted under the same conditions dust concentrations of 50 and 150 g\(\cdot\)m\({}^{-3}\) and \(\mathrm{w_{f}}\) = 2 m\(\cdot\)min\({}^{-1}\) (3.33 cm\(\cdot\)s\({}^{-1}\)).