>>11439385No, they don't fucking work. Mostly because it's impossible to get a seal around one of those things. They're fine for keeping most of the dust out of your lungs when sanding shit, and they'll keep you from hacking all over everyone near you of you're sick, but they do not stop enough viral particles to keep you safe.
https://moscow.sci-hub.si/2357/1ce69f8b60e1c2ac12c0a52412db56a8/makisonbooth2013.pdf#view=FitHTesting found that the BEST mask (one with an integrated visor) with a perfect fit only gave a 55 fold reduction, and they still found plenty of influenza on the inner side. This isn't a coronavirus specific test, but there's no reason to believe the results would be much different. And understand, this test was under ideal conditions with a perfect fit on an unmoving head. These masks have too much blow by to protect you completely.
I haven't found any virus specific studies on proper respirators, but a full face industrial respirator with a four point harness and rubber face seal will perform far better. You can do a vacuum check with these to ensure your fit is good, and the filters are most commonly P100 with an activated charcoal medium for nuisance organic compounds. These filters won't let viral particles through.
In industrial terms, a half mask respirator is allowed a protection factor of 10 (interior concentration / external concentration of 1-3um particles). Those moon suits you see CDC workers wearing sometimes are 25. Full face respirators are given a factor of 50. Surgical masks can't be qualified at any level because they're just fucking worthless. These protection factors are the minimum protection, not best case scenario. As in, the lowest it could be while you still think it's working. In practice, you're more likely to get a factor of 200-600 if you're wearing the mask correctly. If you want a reduction of 1,000 or more, you need supplied air from a bottle or external source.
