'On April 23, 2004, five workers died and two others were seriously injured when an explosion occurred in a polyvinyl chloride (PVC) production unit at Formosa Plastics in Illiopolis, Illinois, east of Springfield. The accident occurred when an operator overrode a critical valve safety interlock on a pressurized vessel making polyvinyl chloride. Vinyl chloride liquid and vapor discharged into the plant and was ignited, resulting in a massive explosion. This one forced a community evacuation and lighted fires that burned for several days at the plant.'
'The CSB's final report on this investigation concluded that company and previous owner did not adequately plan for consequences of human error.'
This video is associated with a computerized animation of the likely scenario of events leading to the explosion.
Other related resources on the
CSB website, including the computerized animation.