Abstract: A draft chamber is located within a clean room for sequentially immersing and processing carriers such as silicone wafers in a plurality of solution vessels provided in the draft chamber. In the draft chamber, a first air flow moves in a substantially horizontal direction from the front portion of the draft chamber toward the rear portion above the surfaces of solutions contained in chemical solution vessels which generate toxic gasses and a second air flow moves downward from the ceiling of the draft chamber. Thus, the toxic gasses generated from the chemical solution vessels are prevented from leaking into the clean room.