Fun fact: 0.3 micron particles are the most penetrating particles of any size, including smaller particles. It’s counterintuitive, but 0.1 micron particles will be filtered out more easily than 0.3 micron particles. [0] That’s in fact why all masks are rated this way, since it gives you the absolute worst case. It’s fair to say that an N95 would filter out at least 95% of all particles.

[0] Wikipedia graph showing this: https://en.wikipedia.org/wiki/HEPA#/media/File:Filteration_C...

Nice, I didn't know that.