Abstract: A retrofit grille frame for retrofitting an existing ventilation assembly used in security settings comprises a frame having an outer periphery sized larger than an opening for the existing ventilation assembly. The frame has at least one inner edge defining a vent opening in the frame. The vent opening is free of any projection of substantial length extending inwardly from any inner edge. The frame has a grille member receiving portion defined on an inner side for receiving a grille member and retaining the grille member in place when the frame is installed and at least one attachment portion capable of receiving a fastener for attaching the frame and a grille member to the existing ventilation assembly.