Apparatus for limiting the amount of debris that is disbursed in and around a disc type wood chipper when the disc is being treated with high pressure air. The apparatus includes a casing that surrounds the chipper disc having a stationary section and a removable section that can be detached from the stationary section to provide access to about 90° of the disc. A shield is hinged to the stationary section of the disc that has a vertical wall and an arcuate cover that can be moved over the exposed section of the disc which contains and directs debris in the chippers exhaust system when removed by high pressure air that is directed at the front face of the disc.