The "95" in N95 refers to it filtering 95% of all particles in general, and particles with a diameter of 2.5 micrometers specifically. The relationship between

The "95" in N95 refers to it filtering 95% of all particles in general, and particles with a diameter of 2.5 micrometers specifically. The relationship between particle size and the ease of filtering them is U-shaped, not linear, with the dip at around 2.5 micrometers being the bottom of the trough.