At about 11:30 a.m. on November 17, 2003, an uncontrolled decomposition reaction in a batch scrubber released chlorine gas into the air at the DPC Enterprises, L.P. (DPC) chlorine repackaging facility in Glendale, Arizona. Hazardous emissions continued for about six hours. Residents and workers in a 1.5 square mile zone were told to evacuate, and 11 police officers and five members of the community sought medical treatment for exposure to chlorine.

KEY ISSUES:
• MATCHING SAFEGUARDS TO RISK
• OPERATING PROCEDURES
• REACTIVE HAZARDS
• EMERGENCY RESPONSE

ROOT CAUSES:
1. Corporate standards relied solely on procedural safeguards against scrubber over-chlorination.
2. Corporate hazard assessment process did not identify or address the consequences of failure to follow the bleach manufacturing SOP, including potential off-site consequences.
3. Internal PSM/RMP audit program did not detect deficiencies in operating procedures, training, operating practice, process safety information, and hazard assessment.

Image Credit: CSB