Hydrochlorofluorocarbon. A physical blowing agent containing at least one carbon, one fluorine, and one chlorine atom in its structure (for example: HCFC-141b). Effective January 1, 2005, the U.S. Environmental Protection Administration (EPA) issued a "Use Ban" regulation on HCFC-141b blowing agent, meaning that SPF systems containing HCFC141b could not be domestically produced or imported, under penalty of law, after this date. The regulation also required that any existing inventory of finished product containing HCFC 141-b could not be applied after June 30, 2005.