Acetone thiosemicarbazone

Acetone thiosemicarbazone is a chemical compound with the molecular formula C₄H₉N₃S. It is used in the plastics industry in the manufacture of polyvinyl chloride (PVC) to terminate the polymerization process.

It is classified as an extremely hazardous substance in the United States as defined in Section 302 of the U.S. Emergency Planning and Community Right-to-Know Act (42 U.S.C. 11002), and is subject to strict reporting requirements by facilities which produce, store, or use it in significant quantities.