Our bathroom fan filter was worn out and very dirty with cigarette smoke from the previous tenant¹, so we removed it. We could replace it, but why does a bathroom fan need a filter in the first place? What harm would be done if we continue using our bathroom fan without a filter?
The bathroom is a windowless room on the inside of an apartment in a 1990s apartment block in Germany with 12 units in the building in total. I suspect the ducts lead to a shared pipe system through which the air goes outside. The fan is a maico, but I don’t know the exact model.
I found some discussion in German on focus, urbia, and vermieter-forum, but no clear conclusion, nor does this English language usenet discussion. DIY stores do not appear to have bathroom fan filters widely available, although they do exist for sale, for example