U.s. Chemical Safety and Hazard Investigation Board

Investigation Report: Chlorine Release (16 Medically Evaluated, Community Evacuated) U.s. Chemical Safety and Hazard Investigation Board

On November 17, 2003, a chlorine gas release at DPC Enterprises (DPC) in Glendale, Arizona, led to the evacuation of 1.5 square miles of Glendale and Phoenix. Five residents and 11 police officers sought medical attention for symptoms of chlorine exposure and were treated and released. The DPC Enterprises facility in Glendale repackages chlorine from railcars into smaller containers. DPC captures chlorine vented from these operations in one of two caustic scrubbers that also produce household bleach for sale as a byproduct. The U. S. Chemical Safety and Hazard Investigation Board (CSB) determined that excess chlorine vented to the scrubber, where it completely depleted the active scrubbing material (caustic) and over-chlorinated the scrubber. The resulting bleach decomposition reaction released a cloud of toxic gases into the surrounding community. Emissions continued at a decreasing rate for about six hours. The incident ended when workers injected additional caustic into the scrubber to stop the decomposition reaction.