It's also a surface-borne virus, and so a mask alone is perhaps not that effective. This is why nurses and doctors wear not just masks, but gloves, eye protection, and gowns when treating active COVID patients.

However, wearing such biohazard-level protection isn't really plausible for daily use, and outdoors, transmission is negligible, so it probably makes little sense for people out for a walk to mask up. Maintaining good hand hygiene practices (i.e. wash hands immediately upon entering the home, and certainly before food preparation, don't touch your face with your hands, etc.) is probably more effective.

> It's also a surface-borne virus

This was a very early belief that turned out to be false.

Cite on the P100? I don't see how A: Oil resistance plays into it B: N95s are already 99.9%+ efficient at airborne covid particle sizes - certainly good enough that fit will be the primary factor. C: N(R)100s generally have higher breathing resistance.. that isn't ideal.

The main thing is that p100s tend to be elastomeric respirators, and those have a substantially better fit than traditional n95 respirators. I’m not going to go digging for the study right now (should be easy to find) but even heathcare workers who had previously fit tested with an n95 only had a bit over 50% chance to get a good seal in a realistic scenario, and it was far worse for people who had not fit tested. Every person who used the elastomeric respirators got a good seal.

Most people don’t do at home fit testing, and even if they do they aren’t testing in a real world situation where they are wearing the respirator for a long time, turning their heads, etc. Elastomerics are just enormously better in these situations.

A pre-covid randomized clinical trial that looked at whether N95s provided any meaningful additional protection against another aerosol-borne virus (flu) to healthcare workers working in outpatient settings found no benefit:

https://jamanetwork.com/journals/jama/fullarticle/2749214

Question: Is the use of N95 respirators or medical masks more effective in preventing influenza infection among outpatient health care personnel in close contact with patients with suspected respiratory illness?

Findings: In this pragmatic, cluster randomized clinical trial involving 2862 health care personnel, there was no significant difference in the incidence of laboratory-confirmed influenza among health care personnel with the use of N95 respirators (8.2%) vs medical masks (7.2%).

Meaning: As worn by health care personnel in this trial, use of N95 respirators, compared with medical masks, in the outpatient setting resulted in no significant difference in the rates of laboratory-confirmed influenza.

One person's cough may emit 10k aerosol particles. Another person's cough may emit 300k. Normal breathing also creates aerosol particles. And they can remain airborne for hours. Only one virion needs to make it through to initiate an infection. And nobody is wearing eye protection anyway and you can get infected with the flu or covid or any one of a wide range of other pathogens via the mucus membranes around your eyes.

I know that it seems as though masking ought to help reduce covid infections (and respirators definitely greatly reduce exposure to, for example, harmful dust particles for home renovators and industrial workers), but it doesn't. Yes, I know many experts and officials persist in claiming otherwise. They are wrong and either ill-informed or lying.