American Standard (NIOSH Standard)
American standards divide masks into three categories:
Class N is only used to protect non-oily particles (eg N95)
R class for the limited time to protect both oily and non-oily particles (eg: R95)
P class for a long time for the simultaneous protection of oily and non-oily particles (eg: P95)
European Standard (EN Standard)
The European standard stipulates that all masks must have the ability to protect both particles:
FFP1 filtration efficiency greater than or equal to 80%
FFP2 filtration efficiency greater than or equal to 94%
FFP3 filtration efficiency greater than or equal to 97%