The pore size of any porous filter medium is one of the essential factors influencing the success of a filtration process. This parameter determines what can or cannot pass through the medium, dictates the minimum particle size a filter can remove, and undoubtedly affects the flow rate. The pore size correlates with the filtration efficiency of a filter medium – the larger the pore size, the lower the filtration efficiency. However, such a correlation is rarely supported by experimental data and described by any empirical equations. Therefore, the main goal of the presented work is to accomplish the following tasks: 1) to measure the pore size and air permeability of various types of nonwoven filter media with a capillary flow porometer; 2) to measure the filtration efficiency (penetration and resistance) by an automated filter tester; 3) to find and investigate the correlations between the pore size, air permeability and filtration efficiency.

12 nonwoven filter media samples from various suppliers were tested in this work. The scanning electron microscope was used to investigate the morphology of the studied samples. POROLUX^TM Cito pressure scan porometer was used to measure the pore size and air permeability, Porefil^TM was used as the wetting liquid and shape factor 1 was applied to the pore diameter calculations. ATI 100X Automated Filter Tester was used to determine the penetration and resistance of two aerosol reagents, such as salt and paraffin. Moreover, three different flow rates - 32, 50 and 75 l/min – for the tests with paraffin were tested.

The porometry measurement results revealed that ...