A filter's ability to capture particles depends on a number of variables and filtration mechanisms. Contrary to popular belief, porous plastic and fiber filters do not simply capture all particles above a certain particle size via mechanical sieving. Rather, their filtration effeciencies benefit from the cumulative effects of interception, inertial impaction, diffusion and electrostatics filtration mechanisms. In order to better understand filtration theory and the separation techniques responsible for this phenomenon, please review the Filtration tutorial* or one of the individual properties listed below for a summary of filtration terms.