CSB Issues Final Report in 2004 Explosion at Sterigenics International Facility in Ontario, California: Notes Lack of Engineering Controls, Understanding of Process Hazards

March 30, 2006

Washington, DC, March 30, 2006 - The U.S. Chemical Safety and Hazard Investigation Board (CSB) today released its final investigation report into the August 19, 2004, explosion that injured four employees and severely damaged a medical products sterilization facility in Ontario, California, disrupting its operations for nine months.

The report says that the lack of engineering controls, lack of process hazard understanding, and use of untreated window glass in the control room were among the causes leading to the explosion and injuries at Sterigenics International Inc., when ethylene oxide gas, used for medical product sterilization, was ignited by the flames in a pollution control device called a catalytic oxidizer.

CSB Lead Investigator Randy McClure said, "Our investigation revealed several factors that led to the explosion. The company did not conduct a thorough explosion hazard analysis, did not ensure that a maintenance supervisor with the authority to override safety systems understood the potential dangers involved in the process, and did not have adequate engineering controls in place to prevent an explosion."

The investigation determined that the ethylene oxide, which is highly explosive, was not properly removed from the sterilization chamber because a maintenance supervisor authorized technicians to bypass a critical safety step, called "gas washing." In addition, investigators determined that Sterigenics did not ensure that the maintenance supervisor understood the hazards of the process before entrusting him with the authority to bypass critical safety systems.

The report also noted that the facility was not designed with engineering controls such as explosive concentration monitoring systems, which would have prevented the explosive gas from reaching the catalytic oxidizer. Other CSB findings indicated that Sterigenics did not conduct a thorough explosion hazard analysis, or adopt earlier recommendations from the National Institute for Occupational Safety and Health (NIOSH) and the National Fire Protection Association (NFPA). Those recommendations stated that sterilization facilities should address the explosion hazard presented by catalytic oxidizers by implementing additional engineering controls.

CSB Board Member John Bresland said, "Oxidizers are commonly used for reducing air pollution. However, they have been the source of many explosions. There is a serious risk if the fuel-air mixture is too concentrated. Facilities with oxidizers should use multiple layers of protection - such as gas monitors, safety interlocks, and alarms - to prevent a single mistake from leading to an explosion."

The Board recommended that the NFPA, which creates fire codes used widely around the country, require additional safeguards to prevent explosions at ethylene oxide facilities, specifically: gas concentration monitoring equipment, alarms, and explosion damage control devices. The Board recommended that Sterigenics install similar safety devices and improve its employee training and hazard analysis programs.

The CSB has produced a video report on the incident, including a computer-generated animation describing the accident scenario as well as CSB safety recommendations, which may be viewed at the agency's website, CSB.gov. A DVD including this and six other CSB safety videos may be obtained at no charge by filling out a request form on the website.

The CSB is an independent federal agency charged with investigating industrial chemical accidents. The agency's board members are appointed by the president and confirmed by the Senate. CSB investigations look into all aspects of chemical accidents, including physical causes such as equipment failure as well as inadequacies in safety management systems, regulations, and industry standards.

The Board does not issue citations or fines but does make safety recommendations to plants, industry organizations, labor groups, and regulatory agencies such as OSHA and EPA. Visit our website, www.csb.gov.

For more information, contact:

Public Affairs Specialist Lindsey Heyl 202-261-3614 or cell 202-725-2204; cell 202-577-8448; or Director of Public Affairs Dr. Daniel Horowitz, 202-261-7613, cell 202-441-6074.


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