What is the difference between an industrial label and a heavy duty label?

Suppliers use the terms interchangeably and neither is a defined standard. “Heavy duty” is a marketing description; “industrial” usually implies a synthetic face material, a high-performance adhesive and a resin or subsurface print. Since neither term guarantees a performance level, compare data sheets instead: temperature range, chemical resistance list, peel adhesion on your substrate, and any UL 969 recognition.