Hot isostatic presses (851411) apply both heat and high isostatic gas pressure simultaneously to consolidate or densify materials — a function distinct from conventional resistance-heated furnaces and ovens (851419), which apply heat alone. The pressure-application mechanism is the defining feature; equipment that only heats without simultaneous isostatic pressure falls under 851419 or another subheading.

Standalone induction or dielectric heating equipment for industrial use falls under 851440. However, if the induction heating coil is an integral part of a larger machine classified elsewhere (e.g., a forging press), it may be classified with that machine under the composite-goods or essential-character rules. The classification depends on whether the heating unit is presented separately or as a component of a complete machine.