In a sheet processing apparatus that performs processing for sheets after image formation such as sorting or stapling of the sheets, sheets conveyed into a waiting tray are temporarily stopped while being kept clamped by a driving roller and a pinch roller in the waiting tray and the clamping is once released. The paper-enclosed filter media units are preferably pre-filled off-site and transported to the installation site via commercial vehicle. The system utilizes the entered information to provide users with public opinion and projection data.