Chemical Safety Board Releases Report about California Explosion

April 3, 2006
A lack of engineering controls and poor understanding of process hazards, in addition to the use of untreated window glass, were some of the causes of an explosion at a California sterilization facility.

According to a final report released by the Chemical Safety and Hazard Investigation Board (CSB), the August 2004 explosion at Sterigenics International occurred when ethylene oxide a volatile gas came into contact with flames in a pollution control device called a catalytic oxidizer. Four workers were injured.

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

According to the report, a maintenance supervisor authorized technicians to bypass a critical safety step, called "gas washing," which caused the ethylene oxide to not be removed from the sterilization chamber. Other CSB findings indicated that Sterigenics did not conduct a thorough explosion hazard analysis or adopt earlier recommendations from National Institute for Occupational Safety and Health (NIOSH) and the National Fire Protection Association (NFPA), which stated that sterilization facilities should address the explosion hazard from catalytic oxidizers by implementing additional engineering controls.

CSB recommended that Sterigenics require additional safeguards such as gas concentration monitoring equipment, alarms and explosion damage control devices. Also, the board asked the company to improve its employee training and hazard analysis programs.

A call to Sterigenics for comment was not returned.

Oxidizers are commonly used for reducing air pollution, but have caused many explosions as well, said John Bresland, CSB board member. He claims this is why multiple layers of protection such as gas monitors, alarms, etc. are necessary to prevent further mishaps from reoccurring.

CSB also produced a video report on the incident, including computer-generated animation describing the accident scenario as well as CSB safety recommendations. This can be viewed on the CSB Web site at

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