[Western Phil]

0.3 microns = 300 nanometers. Size of COVID = 200 nanometers?

[IndispensableDestiny]

0.3 microns = 300 nanometers. Size of COVID = 200 nanometers?

0.3 microns, 300 nm, is the most challenging to remove (more or less). That's why NIOSH test standards are at that size. You can Google for the technical explanation.