The overall efficiency of an air fi

The overall efficiency of an air filter is the result of a combination of 4
basic filtration mechanisms (sieving, inertia, interception and diffusion),
so that the efficiency curve of an air filter adopts a characteristic V
shape showing a minimum level of efficiency. This minimum efficiency
corresponds to a particle size called MPPS (Most Penetrating Particle
Size). In other words, the MPPS is the particle size that is the most
difficult to stop. The MPPS is situated between 0.1 and 0.2 μm
depending on the filter type, and the speed of air flow through the
filtering media