Actually, there is a whole class of face masks that "work". N95, N99 and N100 are statistically effective against 95%, 99% and 100% of dust particles, respectively. Assuming proper fit.
Then you have P95, P99 and P100 that look exactly the same but also work against oil-based aerosols (e.g. if you're spraying paint). These are frequently what you get from a hardware store.
Now all these are actually filtration efficiency classes. So you can get a P100 mask that looks like this [1] or one that looks like this [2]. Obviously [2] gives better protection, even though they are the same class.
For the big full face or half face respirators, you can also get rectangular multi-gas filters (e.g. for organic vapors, acid gases etc) that you can also get pink rectangular aerosol filters for.
Edit: forgot to mention that all these are US NIOSH class numbers. In Europe you'll find mostly-equivalent ratings to P95/P99/P100 specified as P1/P2/P3 (or FFP1 etc.).
Then you have P95, P99 and P100 that look exactly the same but also work against oil-based aerosols (e.g. if you're spraying paint). These are frequently what you get from a hardware store.
Now all these are actually filtration efficiency classes. So you can get a P100 mask that looks like this [1] or one that looks like this [2]. Obviously [2] gives better protection, even though they are the same class.
[1] https://www.amazon.com/3M-P100-Disposable-Particulate-Respir...
[2] https://www.amazon.com/3M-Respirator-Reusable-Particulate-Re...
For the big full face or half face respirators, you can also get rectangular multi-gas filters (e.g. for organic vapors, acid gases etc) that you can also get pink rectangular aerosol filters for.
Edit: forgot to mention that all these are US NIOSH class numbers. In Europe you'll find mostly-equivalent ratings to P95/P99/P100 specified as P1/P2/P3 (or FFP1 etc.).