This is not necessarily the same thing as particulate masks, at least as far as priorities. Obviously some masks filter both well, but the priorities may differ. For example, particulate masks have a release valve, which AFAICT is not ideal for protecting other people from me if I wear it, although of course, protecting yourself from disease with a mask is not valueless to others in that you cannot transmit a disease you do not have.
Jeremy Howard, Cloth masks can protect the wearer:
As we all know now, the science shows that DIY masks are particularly good at protecting those around you in case you’re infected with COVID-19. But that does’t mean that you ca’t do a lot to protect yourself too.
Unfortunately, many public health bodies still incorrectly claim that there is no evidence that DIY masks are useful at protecting the wearer. There’s actually plenty of evidence they can. Effective protection for the wearer of a mask depends on three critical things:
Much more useful summary and advice there, now published (Brooks 2021).
Fixthemask notes some bonus hacks, including using a rubber band to keep masks snug. If you do’t want to hunt for weird filter types on ebay, there is the smart air guide which ranks normal fabrics and household filters.
How to Double Mask Correctly covers double masking, the latest, low-lift version of mask upgrades.
Why so much confusion around masks? Probably several reasons, but here is an interesting one: The 60-Year-Old Scientific Screwup That Helped Covid Kill documents the argument and confusion about what size particles can transmit viruses and the lineage of some cargo-cult science that helped the misunderstandings take too long to settle.
i.e. against pollution. See particulate masks.
A difficult problem, due to the many confounders. At a population level, efficacy is unclear according to the best approximation to meta-reviews that can be contrived (Talic et al. 2021). Some studies report no effect for recent variants, which seems to be about the paucity of RCTs for this question. Certainly it is contentious (Vainshelboim 2021). Also there are some interesting decision theory angles (Muller 2021).