Board Investigators Returning to Site of Recent Gas Explosion near Dayton, Ohio

September 29, 2003

(Washington, DC - September 29, 2003) Investigators from the U.S. Chemical Safety Board (CSB) are returning today to the site of last week's violent explosion at the Isotec chemical manufacturing plant in Miamisburg, Ohio, southwest of Dayton.

The explosion ruptured a carbon monoxide pipe and ignited the gas, prompting a precautionary evacuation that affected about 2000 residents within a mile of the plant. CSB lead investigator John Vorderbrueggen and Board member John Bresland were en route back to the site and were expected to meet with concerned citizens today. The effectiveness of the emergency response and the evacuation order are important issues in the case, investigators say.

The September 21st explosion occurred in a 300-foot tall underground distillation tower, which Isotec used to separate nitrogen and oxygen from nitric oxide, a chemically reactive gas. The incident happened about two hours after an alarm sounded, indicating a process upset in the tower. Workers found a vacuum pump was releasing nitrogen dioxide, a poisonous gas which forms when nitric oxide contacts air. With firefighters standing by at the ready, workers were beginning to off-load the nitric oxide from the tower when a powerful explosion occurred, causing one injury and leaving a 20-foot-wide crater where the tower reached ground level. The internal workings of the column were destroyed, and debris was scattered over a wide area.

Isotec is a subsidiary of Sigma-Aldrich, a leading supplier of research and diagnostic chemicals. Isotec produces special forms of oxygen and nitrogen, known as stable isotopes; the materials are not radioactive. The Miamisburg plant is regulated under the U.S. Occupational Safety and Health Administration's Process Safety Management (PSM) standard, due to the toxicity of the chemicals stored and used at the site. The facility remains shut down in the wake of the accident.

The CSB is an independent federal agency charged with investigating industrial chemical accidents. CSB investigations look into all aspects of such events, including physical causes such as equipment failure as well as inadequacies in safety management systems. Typically, the investigations involve extensive witness interviews, examination of physical evidence, and chemical and forensic testing. 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 to prevent future accidents. Further information about the CSB is available from

For additional information contact Daniel Horowitz at (202) 441-6074 or Sandy Gilmour at (202) 251-5496.


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