I am just gonna drop this here as a reference guide to people who are confounded by letters and numbers.
N series masks (N – NOT oil resistant)
R series masks (Resists oil)
P series masks (oil “Proof”)
That’s what the letters are about, and that’s all they are about – their ability to filter out oil based contaminates in the air.
95 series masks – removes 95% of particles 0.3 microns or larger
99 series masks – removes 99% of particles 0.3 microns or larger
100 series masks – removes 99.97% of particles 0.3 microns or larger (This is HEPA level filtration)
Right now, N-95 masks are probably on back order at your local drug store due to the Chinese War Virus of 2020. Keep in mind that masks are used by industries other than Health Care, and masks can be found in some places that may not occur to you at first blush. Also keep in mind that N-95 masks are the minimum recommended effective face mask. The 99s and 100s, the R series and P series will all work as well as an N-95, albeit at a slightly higher price.
Wash your hands and keep them away from your face. Old advice, but it’s still true.