Dust masks & face masks

Dust masks and face masks are disposable respirators that filter particles out of the air you breathe in. Under EN 149 they are graded into classes: in the standard aerosol test an FFP2 mask captures at least 94 percent and an FFP3 mask at least 99 percent of the test particle. That class describes the filter medium and says nothing about gases or vapours, which is what masks with changeable filters are for. Fit matters just as much, because air that leaks past the edge never passes through the filter.