MIELE H.E.P.A. FILTER The Active H.E.P.A. (High-Efficiency Particulate Air) filter not only captures and retains tiny, lung-damaging particles (including dust mite feces and pollen), it also uses the same Generally Activated Charcoal filter (GAC) that the Active Air Clean filter uses to absorb odors. This Miele filter conforms to the new stringent European standard for filtration (EN 1822) which means that it actually traps 99.99% of all particles as tiny as 0.3 of a micron. These filters are so well designed that they only need to be replaced after 50 hours of use, or approximately 12 months. There is also a convenient spot to write the date on the filter, which takes the guesswork out of when the filter should be replaced.