Unvented Solvents Led To Explosion

Trapped solvent vapors at a Massachusetts paint and ink factory led to an early-morning explosion on November 22, 2006, that injured 10 residents and damaged more than 100 homes and buildings up to a mile from the blast, says the Chemical Safety & Hazard Investigation Board (CSB). In a preliminary report, CSB said the accident's "immediate cause" was plant owners CAI and Arnel's routine practice of turning off a solvent-ventilating system at the workday's end at the Danvers facility. The plant produced solvent-based stains, coatings, and printing inks. The board believes a 3,000-gal mixing tank had been left to stir overnight after being charged with powdered resin and flammable solvents, including heptane and propyl alcohol, while being heated by a steam piping system. The tank likely overheated, and with the ventilation system turned off, flammable vapors built up and eventually found an ignition source. The explosion's timing at 2:45 AM was "fortuitous," said CSB Chairman Carolyn W. Merritt, because workers and residents could have easily been killed had the blast occurred during the day. More information is available at www.csb.gov.