This action proposes to revise EPA's definition of Volatile Organic Compounds (VOC) for purposes of preparing State Implementation Plans (SIPs) to attain the National Ambient Air Quality Standards (NAAQS) for ozone. The action would add Hexafluoro-2- Butene (also known as HFO-1336mzz-E) to the list of compounds excluded from the definition of VOC on the basis that this compound makes a negligible contribution to tropospheric ozone formation. VOC exemption petition submitted by Chemours on 11/30/2016.