The charge size at which AIM Act Subpart C obligations attach. Appliances holding 15 pounds or more of an HFC — or of a substitute with a GWP above 53 — became subject to leak repair, leak inspection, recordkeeping, and reporting on January 1, 2026. Residential and light commercial AC and heat pumps are exempt. Section 608’s comparable threshold, for ozone-depleting refrigerants, is 50 pounds.