(1) Cleaning tool. An item used to aid cleaning, such as wiping rags, brushes, mops, scrapers, or water jets.

(2) Industrial cleaning solvent. Any liquid containing a volatile organic compound (VOC) used to facilitate the removal of foreign materials from a surface.

(3) Unit operation. An industrial operation, classified or grouped according to its function in an operating environment, such as mixing or holding vessels, tanks, reactors, floors or other surfaces to be cleaned.

(4) Unit operation systems. The ensemble of equipment around which a material balance is performed. It includes all possible points/sources that could result in losses to the atmosphere as a result of the equipment being cleaned, including losses during dispensing of cleaning materials, losses from residual cleaning materials on or in cleaning tools, and losses from storing cleaning materials.