
Verify if the duct cleaner follows NADCA's standards for air duct cleaning and NAIMA's recommended practice for ducts containing fiberglass lining or constructed of fiberglass duct board.

Verify if the duct cleaner installs access doors in sheet metal ducts attached with more than just duct tape, e.g., screws, rivets, mastic, etc.

Verify if the duct cleaner checks whether there is air leakage through access doors, which may be slight or non-existent. Such air leakage can damage the duct.