The defining feature is whether the motor is integral to the vacuum unit itself. Central vacuum systems, where the motor and suction unit are installed remotely (e.g., in a utility room) and connected to inlets throughout a building, are the most common example. Portable units that plug into an external power supply but contain their own motor still classify as self-contained. The physical integration of the motor into the appliance body is the key classification test.

The power unit (motor and collection canister) of a central vacuum system typically classifies under 8508.60. Inlet valves, tubing, and fittings installed in walls are generally classified separately as parts under 8508.70 or, depending on their material and function, under other headings. Importers shipping complete system kits should consider whether the components are classifiable as a set or must be broken out individually.