The US standard divides masks into three categories:
N series: only used to protect non-oily particles, no time limit
R series: protection against oily and non-oily particles in a limited time, limited time for oily particles (8 hours)
P series: long-term use for simultaneous protection of oily and non-oily particles, time-consuming for oily particulates: 40 hours of cumulative use
According to the filtering effect, the filter material is divided into three grades:
Class 95: Minimum filtration efficiency ≥95%
Grade 99: Minimum filtration efficiency ≥99
100 grade: minimum filtration efficiency ≥99.97
European Standard (EN Standard)
European standards stipulate that all masks must have the ability to protect two types of particles:
FFP1; filtration efficiency ≥80%
FFP2: Filtration efficiency ≥94%
FFP3: Filtration efficiency ≥97%
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