40 CFR § 413.61 - Specialized definitions.
For the purpose of this subpart:
(a) The term sq m (“sq. ft.”) shall mean the area exposed to process chemicals expressed in square meters (square feet).
(b) The term operation shall mean any step in the chemical milling or etching processes in which metal is chemically or electrochemically removed from the work piece and which is followed by a rinse; this includes related metal cleaning operations which preceded chemical milling or etching, when each operation is followed by a rinse.