Section 721.4160 - Hexafluoropropylene oxide(a)Chemical substance and significant new use subject to reporting.(1) The chemical substance hexafluoropropylene oxide (HFPO), CAS Number 428-59-1 [Listed in TSCA Inventory as oxirane, trifluoro(trifluoromethyl)-] is subject to reporting under this section for the significant new use described in paragraph (a)(2) of this section.(2) The significant new use is any use other than as an intermediate in the manufacture of fluorinated substances in an enclosed process.(b)Specific requirements. The provisions of subpart A of this part apply to this section except as modified by this paragraph.(1)Definitions. In addition to the definitions in § 721.3 , the following definitions apply to this section: (i)Enclosed process means a process that is designed and operated so that there is no intentional release of any substance present in the process. A process with fugitive, inadvertent, or emergency relief releases remains an enclosed process so long as measures are taken to prevent worker exposure to and environmental contamination from the releases.52 FR 41300, Oct. 27, 1987. Redesignated at 53 FR 2845, Feb. 2, 1988. Further redesignated at 58 FR 29946, May 24, 1993, as amended at 58 FR 34204, June 23, 1993