HEPA filters block particles smaller than it's rated size, and they block those particles more easily than larger particles because of Brownian motion and the physics of electrostatically capturing particles.
They can block smaller particles, yes. But it’s non-deterministic. More importantly, they don’t block all or even most of the smaller particles. If they did, then they would be rated for the smaller particles that they are blocking.
N95 filters are rated based on how many 0.3-micron particles they can block. They are rated for that particle size because that particle size is the hardest particle size to block and therefore serves as a proper test of the filter's efficiency.
If you look at a graph of the blocking efficiency of an N95 filter vs particle size, that graph is a curvy "V" shape, with the bottom of that "V" being at 0.3 microns.
bradknowles|4 years ago
ddxxdd|4 years ago
If you look at a graph of the blocking efficiency of an N95 filter vs particle size, that graph is a curvy "V" shape, with the bottom of that "V" being at 0.3 microns.