EN 143 sets the requirements for replaceable particle filters fitted to EN 140 or EN 136 masks. They capture solid and liquid aerosols — dust, fume, fibres, mist, bacteria and viruses.
Classes
| Class | Filtration efficiency | Typical use |
|---|---|---|
| P1 | ≥80% | Coarse, non-toxic dust |
| P2 | ≥94% | Wood dust, quartz, bioaerosols |
| P3 | ≥99.95% | Asbestos, toxic metals, carcinogens |
The R and NR marking
A filter is marked R (reusable, may be used for more than one shift) or NR (non-reusable, single shift). An R filter is additionally tested after exposure to a liquid aerosol, which is the harder test.
A particle filter should be changed when breathing resistance becomes noticeably higher. Unlike a gas filter, a loaded particle filter actually filters better than a new one — but breathing gets harder, and that is the signal to replace it.