An exhausted air dispensing device for a hydraulic power nailer includes a ring engaged with a flange extending from a recessed area defined in an end cap of the body of the nailer. The flange has a plurality of notches which communicate with a passage from which the exhausted air of the nailer flows. The flange has a plurality of blocks extending from the ring and located in alignment with the notches in the flange so that the speed of the exhausted air is reduced when the exhausted air blows against the blocks. A cover has an opening defined in a periphery of the cover which is rotatably engaged with the recessed area. A positioning pin biasedly extends from the end cap and the cover has a plurality of dents in the bottom thereof so that the positioning pin is engaged with one of the dents of the cover.