The invention concerns an analyzer, typically for analyzing body fluids, which has one or several exchangeable cassettes (consumables) that contain operating liquids, operating materials and/or consumables and can be inserted into corresponding holders of the analyzer, wherein the analyzer has a system for exchanging ambient air which has a filter unit on the inlet side of the analyzer to filter the ambient air that needs to be exchanged. The filter unit is integrated into at least one of the exchangeable cassettes in order to minimize the amount of maintenance for the analyzer.