Thanks to the HEPA hygiene filter (EN 1822:1998), the vacuum cleaner exhaust air is cleaner than room air. Annual replacement recommended.The HEPA hygiene filter (EN 1822:1998) reliably filters the finest dirt such as pollen or allergy-triggering particles. It is therefore essential that the vacuum cleaner exhaust air is cleaner than the air in the area in which you are working. We recommend you change the filter once a year.