The U.S. Environmental Protection Agency (EPA) has proposed excluding two compounds from the definition of volatile organic compounds (VOC s) under the Clean Air Act (CAA) because they make a “negligible contribution” to the formation of ground-level ozone. 76 Fed. Reg. 64,059 (10/17/11). The two chemicals are trans-1,3,3,3-tetrafluoropropene, or HFO -1234ze, a refrigerant, propellant and blowing agent for insulating foam; and 2,3,3,3-tetrafluoropropene, or HFO -1234yf, a refrigerant for refrigeration and air conditioning. EPA issued its proposed rule excluding the compounds in response to petitions from Honeywell, Inc. EPA will accept comments on the proposal until November 16, 2011.