Vinyl Chloride Monomer Explosion Lisa A. Long, James Lay, Katherine Leskin, Randy McClure, and Allen Smith U.S. Chemical Safety Board, 2175 K St, NW, Washington, DC 20037; lisa@convective.com (for correspondence) Published online 5 October 2007 in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/prs.10233 On April 23, 2004, an explosion and fire at the Formosa Plastics Corporation, Illiopolis, Illinois (For- mosa-IL) polyvinyl chloride (PVC) manufacturing fa- cility 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 smol- dering 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 subsid- iary of Formosa Plastics Corporation, USA (FPC USA), purchased the Illiopolis facility from Borden Chemical and operated it for 2 years before the incident. This article includes the incident’s root and contribut- ing causes, and CSB recommendations to prevent recur- rence. This paper represents the views of the authors. The full CSB report on this incident can be found at www.csb.gov. Ó 2007 American Institute of Chemical Engineers Process Saf Prog 27: 72–79, 2008 Keywords: vinyl chloride explosion; human factors BACKGROUND The Formosa-IL PVC plant was purchased from Borden Chemical, and included a commodity PVC resin process (PVC1) and a specialty PVC resin pro- cess (called ‘‘Paste’’). The reactor building (Figure 1) housed the PVC1 and Paste production areas. Formosa-IL produced PVC by the polymerization of VCM. VCM is a colorless gas with a mild, sweet odor, which the average person cannot smell at con- centrations below hazardous levels. VCM can ignite when its concentration in air is between 3.6% and 33% by volume. It has serious short and long-term health effects, and is a known human carcinogen. Two operators, a poly operator and a blaster oper- ator, were responsible for the reactor involved in this incident. The poly operator worked exclusively on the upper level of the building where the reactor controls and indicators were located, while the blaster operator worked on both the upper level and the lower level, where additional valve controls were located (Figure 2). To make a batch of PVC, the poly operator: • readied the reactor, • added the raw materials (liquefied VCM, water, suspending agents, and reaction initiators), • heated the reactor, • monitored the reactor temperature and pressure until the batch was complete, then • vented pressure from the reactor, and told the blaster operator to transfer the batch to the stripper. To transfer the batch to the stripper, the blaster op- erator opened the transfer and reactor bottom valves from the lower level (Figure 3). When the transfer was complete, the blaster opera- tor closed the transfer valve, and the poly operator purged the reactor of hazardous gases to prepare the reactor for cleaning. The blaster operator cleaned the reactor by • opening the reactor manway on the upper level, • power washing PVC residue from the reactor walls, and • opening the reactor bottom valve (if not left open from the transfer) and drain valve to empty the cleaning water to floor drains. Once the blaster operator finished cleaning the reac- tor, he closed the reactor bottom and drain valves, and gave the poly operator a completed checklist indicating that the reactor was ready for the next batch of PVC. REACTOR EMERGENCY PROCEDURES The reaction of VCM to form PVC generates heat. If this heat is not removed, a runaway reaction may occur, potentially increasing reactor pressure above Ó 2007 American Institute of Chemical Engineers 72 March 2008 Process Safety Progress (Vol.27, No.1)