So commies at #OSHA say: 0.3-micrometer|.00001-micrometer, its all the same in mask-land.
So the point in standards is?

https://www.cdc.gov/niosh/docs/96-101/appendices.html
"The 0.3-micrometer diameter used..
..is approximately the most penetrating particle size for particulate filters. Although it seems contrary to expectation, smaller particles do not penetrate as readily as 0.3-micrometer particles. Therefore, these respirators will filter all other particle sizes at least as well as the certified efficiency level."