ANDOVER — A small explosion and leak of a potentially toxic gas forced the evacuation of a building housing a military and civilian contractor and brought a response by a hazmat team yesterday. There were no reported casualties.
"We didn't know exactly what we were dealing with," Andover Fire Chief Michael Mansfield said.
The explosion and leak occurred around 11:30 a.m. in a room on the north side of the building at 20 New England Business Center Drive, occupied by Physical Sciences Inc.
Mansfield said no one was in the room at the time of the explosion.
He said a vapor cloud was emanating from the building when firefighters arrived, prompting a call to the state's District 6 hazmat team.
The incident was elevated to a Tier 2 hazardous material response (the second-lowest requiring a short-term response, according to the state's Department of Public Safety Web site.) Tier 1 is the lowest, Tier 4 the highest.
Around 4 p.m., the scene was cleared and everything was deemed safe, Mansfield said. Andover Health Director Thomas Carbone and representatives from the Massachusetts Department of Environmental Protection and the U.S. Environmental Protection Agency were at the scene.
Mansfield was unsure how many people were evacuated. Early estimates were 30 to 40.
The north side of the building faces the Wyndham Hotel, which was advised to shut its windows, shut off air-conditioners, and keep everyone inside.
Mansfield identified the gas as boron trichloride, which he described as being colorless, toxic, nonflammable and corrosive.
He said the responders didn't have immediate access to a material safety data sheet, which would have helped determine more quickly what materials were in the room.
Mansfield said no one was exposed to the gas because of the quick actions of an employee who heard the explosion from another lab and rushed to close the door after seeing a haze in the room and pulling an alarm, which alerted the Fire Department.
Mansfield said an investigation will continue.
Physical Sciences Inc., or PSI, provides contract research and development services in a wide range of technical areas to both government and commercial customers, according to the company's website.
Staff writers Bill Kirk and Jim Patten contributed to this report.
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