On April 28, 2022, the U.S. Environmental Protection Agency (EPA) published a proposed rule seeking comments in response to a petition requesting the revision of the EPA's regulatory definition of volatile organic compounds (VOC) to exempt trans-1,1,1,4,4,4- hexafluorobut-2-ene (also known as HFO-1336mzz(E); CAS number 66711-86- 2). The EPA is now taking final action to revise the regulatory definition of VOC under the Clean Air Act (CAA). This final action adds HFO-1336mzz(E) to the list of compounds excluded from the regulatory definition of VOC on the basis that this compound makes a negligible contribution to tropospheric ozone (O<INF>3</INF>) formation.