The usual argument is that a mask catches aerosol droplets. There was a demo video with green laser lights illuminating speech droplet dispersal with and without mask and there was a big difference. BUT, likely not anywhere near all droplets are of that size. Smaller ones will get through, or even evaporate quickly and the content gets through. That'd not be visible in that laser show. Now, this is my conjecture, IDK about the droplet size distribution during articulation or just exhaling. If you exhale through a mask in the cold in circumstances when you see fog without mask and with mask, it seems that a lot humidity (presumably with virus) is going through the mask.
Anyway, there are studies showing they have little effect for preventing respiratory viral spread.
why doesnt anyone ever mention the size difference between the virus and the size of the holes in the mask?
The usual argument is that a mask catches aerosol droplets. There was a demo video with green laser lights illuminating speech droplet dispersal with and without mask and there was a big difference. BUT, likely not anywhere near all droplets are of that size. Smaller ones will get through, or even evaporate quickly and the content gets through. That'd not be visible in that laser show. Now, this is my conjecture, IDK about the droplet size distribution during articulation or just exhaling. If you exhale through a mask in the cold in circumstances when you see fog without mask and with mask, it seems that a lot humidity (presumably with virus) is going through the mask.
Anyway, there are studies showing they have little effect for preventing respiratory viral spread.