A filter housing (10) for a filter unit (50) with a substantially semicylindrical air filter (52). The housing includes an air inlet (20) and an engine air outlet (40). The filter housing (10) has a top aperture (12) for introducing and taking out the filter unit (50), and a cover (30) to close the top aperture (12), a bottom aperture (16) to be closed and opened by a closed filter bottom (70) of the filter unit (50) being introduced or taken out. Also, a filter unit for such a filter housing is disclosed.