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N95 masks work very well for filtering out viruses and similar sized particles. See for instance
"A filtration efficiency value for pathogens (influenza A, rhinovirus 14, bacteriophage ΦΧ174, and S. aureus) of >99.6% was achieved by the test mask, regardless of configuration tested. This value reflected the ability of the mask to exclude infectious agents, including respiratory viruses. Similar, albeit more variable, results were obtained when genomic copies of influenza A virus and rhinovirus were monitored rather than infectious virus. The filtration efficiency of the test mask for surrogate pathogens was similar, regardless of the challenge microbial agents’ size (ranging from 27–30 nm for bacteriophage and rhinoviruses to 2,000 nm for S. aureus)."
For the smallest types of particles there are better masks available. Naturally having a hazmat suit with a positive pressure, rubber seal etc. is preferable to just a mask, but the masks significantly reduce the particulate matter (including viruses) inhaled.
There is nothing "magical" about virus particles nor N95 masks. Any fine mesh presenting a high probability of the particle sticking and sufficient mesh-particle bonding strength will reduce the amount of particulate matter that is inhaled to a significant degree, especially when the fluid/gas flow through the mesh is low.
Interestingly regions of the world with a tradition of face mask use (often using disposable masks that are discarded after use) such as East Asia have much lower rates of Covid-19 death than places that do not use such masks.