link we KNOW the size distribution of respiratory aerosols--we have since the 80's. We also know how they can--and cannot--be filtered. They range from ~100 nm - 1 micron, with more than half smaller than 0.28 microns (280 nm), and the majority between 0.2 and 0.5 microns--a range that has a special name called "Most Penetrating Particles," (MPPs), that should give you an idea of the challenge. This size distribution is nearly identical to that of cigarette smoke, where the majority of particles cluster around the 0.2 – 0.25 micron range. Fewer than 0.1% of respiratory aerosols are above 5 microns. It is likewise known that particles over 5 microns carry less than 0.1% of virus (not a coincidence). Beyond that, multiple studies for flu and COVID have shown that when 5+ micron aerosols carry virus, that virus is non-replicating and non-infectious.