A wood chipper includes a housing having an inlet opening and a discharge outlet with a chipper disk rotatably mounted in the housing and having a chipper knife mounted on a front face thereof adjacent a chipper slot extending through the disk. A plurality of fins are mounted on the back face of the chipper disk. An inlet hopper is connected to the inlet opening and a blow back shield is mounted in the upper end portion of the hopper with the shield including an outer layer of clear synthetic material extending across the hopper and an inner layer of synthetic material extending part way underneath the length of the layer of clear synthetic material. The inner layer may be provided with a safety warning thereon which is visible through the outer layer of clear synthetic material. A discharge chute is connected to the discharge outlet which has inwardly angled plates around part thereof. Vent holes are provided in a wall of the housing which add air flow to the wood chipper when it is being operated.