Earlier quoted context omitted.
> 2. CDC (I believe) was claiming that N95 masks won't help as much as other masks. Later it turned out they just didn't want to create scarcity for N95 masks because hospitals need them. The messaging IIRC was a little more nuanced, but delivered poorly The US and other countries faced a mask shortage at the beginning of the pandemic. Masks don't provide absolute protection, but they do reduce viral load exposure (a…
It was especially confusing when my company at the time (in sfbay area) hired someone to tell us that masks won't help because viruses are small and also we'll be back in the office soon. :)
It's actually 0.3 micrometer particles that are most difficult to filter. Smaller than that, particles start to dance around and not move smoothly, because of Brownian motion, so they get stuck in the filtering fibers better.
https://www.researchgate.net/figure/Typical-filter-efficienc...