| | Hydro-Thermal Corp (Waukesha, WI) Direct steam contact liquid & slurry heaters, steel & fiber drum deheading equipment, water heating systems | |
| | Industrial Combustion Engineer (Gary, IN) Industrial ovens, furnaces & air heaters | |
| | Industrial Systems Corp (Medina, OH) Electric, tubular, strip & process heaters, kilns, baking & gas ovens | |
| | Industrial Temperature Control (Dearborn, MI) Thermocouples, electric heaters & timers, custom control panels & temperature controllers | |
| | Infrared Internationale/N Amer (Comstock Park, MI) Ceramic infrared heaters | |
| | ITW Chronotherm (Elmhurst, IL) PTC heaters | |
| | Johanson OMS Inc (Edgewater, FL) Flexible electric heaters & controls | |
| | Kalglo Electronics Co Inc (Bethlehem, PA) Electronic controls, heaters, meters, voltage suppressors & line conditioners | |
| | Keil, William Manufacturing Co (Warren, MI) Electric branding irons, electric knife heaters & small tool work | |
| | Kemco Engineering Corp (Freeport, IL) Special equipment, custom production tables & air make-up heaters designing & building | |
| | Kemco Systems Inc (Clearwater, FL) Manufacturers hot water heaters, hot & cold water tanks, water conservation, recycling, hot water & heat reclaiming systems | |
| | Kutrieb Parts & Service (Chetek, WI) Distributor of oil furnace & heaters; parts & services | |
| | Laboratory Craftsmen Inc (Beloit, WI) Laboratory apparatus: chemical-flask heaters, portable power controls, magnetic stirrer, hotplates | |
| | Lenan Corp (Janesville, WI) Commercial waste oil heaters | |
| | Lintern, A R Inc (Redford, MI) Automotive hot water heaters, business & truck underseat heaters, van heaters, roof vents, heating & cooling units, defogging fans & defrosters | |
