On May 3, 2021, the Environmental Protection Agency (EPA) proposed a rule to create an allowance trading program to phase down the production and consumption of hydrofluorocarbons (HFCs). HFCs became widely used in air-conditioning and refrigeration equipment as substitutes for ozone-depleting substances, but they are powerful greenhouse gases. The HFC rule was proposed pursuant to the American Innovation and Manufacturing Act, which was enacted in December 2020.