Injured was cleaning out Kiln 5 coating pocket when he thought he smelled something burning and went down into the cooler pit. Injured walked to Kiln 2 and turned around to exit after inspecting the area. As he walked toward Kiln 5, he slipped and fell to the walkway jarring his back. Injured was treated initially on 7/6, however the injury did not become reportable until 7/13.