Filter - Ventilogic LS PlusFilter Ventilogic LS Plus This filter cassette contains a fine dust filter for the valve logic, ventimotion, ventilogic logic LS plus. The fine filter should be replaced every 1000 operating hours. Clean dust filter change fine filter. 1. Take off the filter compartment lid. 2. Remove the coarse dust filter from out of the filter compartment lid and clean it with clean running water until there are no residues. 3. Change the fine filter if required.