Lucifer Furnaces' model RD8-H14 Red Devil dual-chamber, heat-treating furnace is constructed with heavy-gauge, reinforced sheet steel. The 7-kW system features an upper hardening chamber and a lower tempering chamber, each measuring 9" × 12" × 14". Ceramic hearth plates support loads of 25 lbs. per square ft. in both chambers. The chambers are lined with 4 ½" of combined lightweight firebrick and mineral wool insulation for energy-efficient operation, the company says. Heavy-gauge, wire-wound heating elements in radiant panels heat the upper chamber to 2,200°F, and a rear-mounted, stainless steel, high-volume CFM fan assembly recirculates air at 1,200°F in the lower chamber. Both chambers have a horizontal swing door with a safety micro-switch to shut off power when the door is opened. Honeywell digital temperature controllers in a side-mounted NEMA 1 control panel control each chamber independently.