The invention described herein is a fire protection device in the form of an insert designed to be quickly installed in new or existing electrical boxes located in firewalls. This insert is comprised of a material designed to withstand high direct heat and serve as a barrier to the passage of direct heat or smoke and gases through firewalls rated under ASTM E-119. The insert features a flanged open end which overlaps any gaps between the existing electrical box and the wall. The back wall of the insert box may have either openings to permit wires to pass through to the electrical device or a plug-harness assembly which obviates the use of holes in the back of the insert box.