One worker was slightly injured in the Sept. 21 explosion, which produced a plume of yellow-orange smoke several hundred feet high at the Isotec plant in this Dayton suburb and blew off part of the roof.
Firefighters had been working with six employees to contain a nitric oxide leak when the explosion occurred. About 500 homes within a mile of the plant were evacuated for a day after the explosion.
The U.S. Chemical Safety and Hazard Investigation Board said Isotec managers knew about the explosive properties of nitric oxide, but did not thoroughly check their system to minimize the possibility of failure or properly design explosion shields.
The board also said there were two earlier leaks of nitric oxide, in 1998 and 1995. One resulted in an underground explosion.
``Our study found that these incidents were not reviewed adequately and did not result in appropriate corrective actions that might have prevented this larger explosion,'' said board member John Bresland.
George Bleazard, Isotec's corporate director of health and safety, said the explosion was accidental and could not have been predicted. However, he said the company will review the board's report as part of its ongoing safety analysis.
Bleazard noted that Isotec has permanently terminated production of nitric oxide at the plant.
Isotec, a division of Milwaukee-based Aldrich Chemical Co., used nitric oxide gas to produce isotopes medical researchers use to trace metabolic pathways inside the human body.
The board also said potential dangers at the plant were not adequately considered in making zoning changes that allowed the building of homes near the facility. And it said there were problems with emergency planning and notifying residents of the evacuation.
Miamisburg spokesman Gary Giles said the city was not made aware of the potential hazards at the plant when it zoned the area. He said the city's emergency workers responded quickly to the explosion and that police went door to door telling as many residents as they could to evacuate.
``Emergency events like this, by their nature, result in some level of confusion,'' Giles said
