On April 23, 2004, an explosion and fire at the Formosa Plastics Corporation, Illiopolis, Illinois (Formosa-IL) polyvinyl chloride (PVC) manufacturing facility killed five and severely injured three workers. The explosion and fire destroyed most of the reactor facility and adjacent warehouse and ignited PVC resins stored in the warehouse. The plume of smoke from the smoldering fire drifted over the community and resulted in an evacuation that lasted 48 h. Vinyl chloride (VCM), a highly flammable chemical and known carcinogen, and the major component in the facility's manufacturing process, was the primary fuel for the initial fire and explosion. Formosa-IL used VCM to manufacture a variety of PVC resins in 24 heated and pressurized reactors. Formosa-IL, a wholly owned subsidiary of Formosa Plastics Corporation, USA (FPC USA), purchased the Illiopolis facility from Borden Chemical and operated it for similar to 2 years before the incident. This article includes the incident's root and contributing causes. and CSB recommendations to prevent recurrence. This paper represents the views of the authors. The full CSB report on this incident can be found at www.csb.gov.