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Safety Board Issues Report on Nitric Oxide Accident

August 30, 2004 | A version of this story appeared in Volume 82, Issue 35

Isotec and its parent, Sigma-Aldrich Corp., failed to analyze potential process hazards or to learn from two previous accidents, according to a recent Chemical Safety & Hazard Investigation Board report of a severe accident that occurred at the firm's plant in Miamisburg, Ohio, a year ago. In September 2003, early on a Sunday morning, a 300-foot, belowground, nitric oxide distillation column exploded at the facility, resulting in one injury and the evacuation of 2,000 nearby residents. The explosion damaged several plant buildings, including a 52,000-lb carbon monoxide storage tank that began leaking and caught fire. The company chilled NO liquid (below –241 °F) to separate and extract NO molecules that contain stable nitrogen isotopes for use in medical and other applications. Because of extensive damage, the board was unable to identify the accident's exact cause but concluded that a hole had developed somewhere in 2,200 feet of distillation column piping, releasing explosive liquid NO into the column's vacuum jacket. The board found that the company's hazard analysis for the process was inadequate and it had failed to fully investigate two earlier piping leaks that resulted in similar but smaller explosions. The report also found fault with the community's emergency planning and notification system, as residents were either unaware of the evacuation order or unclear about how to respond. The plant, the board said, was once surrounded by farmland but now is near homes due to zoning decisions that failed to note the facility's potential danger. The report is available at


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