How should electromagnetic compatibility be specified for industrial heating elements?

Electromagnetic compatibility of an industrial heating element is set by its duty, not by a catalogue label. The resistive load itself is quiet; the real sources are power controllers, solid-state relays and long control cables. Specify supply phases, voltage, wattage, sheath diameter and material, surface load, ingress protection, lead length and shielding or earthing, then require the supplier to supply conducted and radiated test data under switching transients. Check that sensors and controllers hold steady readings during heater cycling, and verify insulation, leakage current and temperature fluctuation on site.