You can also order original and third-party filters online. It starts at 19 euros and goes up to 39 euros - so it's much cheaper. The basic question is whether you want or need to change the filters after 145 days. If you only want to reduce the house dust, you can knock out or vacuum out the filter and continue to use it - but the error message will remain. However, if you use something like activated carbon, the filter performance is exhausted and the filter should be changed.

Filters should be changed after 145 days, the unit indicates. Filters can also be bought here, the standard filter and the special filter for allergy sufferers. Costs 50 to 60 CHF. However, I can't tell you why these filters are shown as replacement parts in the product itself. But they are easy to find with the search here