A cleaning unit (A) includes a movable cart (20) which carries a cleaning system for cleaning baked-on residues from walls (10) of a sterilizer chamber (12). Alkaline and acid cleaning solutions (180, 182), for removing organic and inorganic residues, respectively, from the chamber, are stored in a multi-compartment container carried by the cart and having two storage compartments (52, 54). The alkaline and acid solutions are sequentially sprayed over the chamber walls and returned to their respective compartments. After cleaning is complete, a wall (200) which separates the two compartments is punctured. The two cleaning fluids are thereby mixed together to form a neutral or near neutral solution which is disposable in a sanitary sewer system without further treatment.