That's not right.ConsoleWatcher wrote: ↑ N95 masks only filter out 95% of harmful air particles. If you breath enough affected air, you can still catch it.
That's why healthcare workers who work with COVID-infected people are getting it themselves at a high rate, whereas period who had incidental contact with someone who had it (such as passing them in a grocery store) do not.
N95 mask will at worse filter out 95% of the particles in the air (whether they are harmful or not) that are 0.3 microns in size. While the virus itself is approx 0.125 microns , the virus doesn't float around by itself - the virus needs to be attached to some other particle - ie water droplet, mucus, protein particles - which are generally larger than the 0.3 microns in size. Therefore, the N95 mask works by filtering the particle the virus is typically attached to but not the virus itself.
Here's a great fact checked article on N95 mask and why they work in this case - Fact check: No, N95 filters are not too large to stop COVID-19 particles
As for the reason why health care workers still catch it, no real study has been done that I'm aware of but most like due to failures in product or procedures - ie a defective N95 mask or that the mask wasn't put on correctly so that it has a perfect seal around the nose and mouth, cross contamination of PPE, disinfectant processes were ineffective or not followed - and in an infectious environment like a COVID ward, the virus concentration in the air (or load) is many times higher than in other situations so it's possible that the virus may have entered the body through the eyes even with a face shield since it's not sealed around the eyes.