Confirm where the debris is located
Dust at a register can originate at the grille, in the duct, or from conditions in the room, so its presence does not by itself establish the need for full-system cleaning. Inspection can identify whether material is visibly accumulated in supply or return sections and whether it extends beyond an accessible opening. That evidence defines the appropriate scope and helps avoid treating unrelated airflow or equipment concerns as a duct-cleaning problem.
