Abstract: An electrical junction box has an interior electrical component container having a forward opening, and a second rearwardly opening container portion which opens rearwardly and is filled with insulating material. The housing is a one-piece unit preferably molded from fire-resistant fiberglass. The junction box is manufactured by molding a one-piece fiberglass housing, filling the rearwardly opening chamber with a fluid insulating material such as calcinated gypsum, allowing the insulating material to harden, and drilling a hole from the exterior of the unit into the interior chamber to permit wiring or conduits to extend to the box.

Abstract: An electrical box designed to minimize the potential for sound, smoke or fire traveling therethrough when wall-mounted and has an interior rigid housing and a molded non-combustible exterior casing. The casing is a unitary, single-piece sheathing, having openings only for attachment of line conduit. A tubular collar portion extends outwardly from the front opening of the box, and is easily cut or machined to conform to the adjacent wall surface.