Comment by weaksauce

> Almost all of these review sites, not understanding the physics involved, believe a HEPA filter sieves particles down to a size of 0.3 microns, which implies that anything smaller passes on through.

To be fair, it took a pandemic for me to go to the literature of mask effectiveness and finally found the "on the filtration efficiency of fiberous filters" paper that showed the u shaped curve. it's not something that they scream from the hills about in their product brochures. That said it should be screamed from the hills.