CSB: Lack of Safeguards Led to Massive CAI Explosion

A massive explosion and fire at the CAI/Arnel ink and paint products manufacturing facility in November 2006 occurred because CAI lacked safeguards such as alarms and automatic shutoffs that would have prevented a 10,000-pound mixture of flammable solvents from overheating, investigators from the U.S. Chemical Safety Board (CSB) stated in a final draft report.

Steam heat to the mixing tank was most likely inadvertently left on by an operator before he left for the day. As the temperature increased, vapor escaped from the mixing tank, built up in the unventilated building, ignited, and exploded.

CSB investigators said that ink manufacturer CAI did not follow regulations or appropriate good practices for the handling of flammable solvents, and the report proposes changes to national fire codes and to state licensing and inspection procedures to improve the safety and oversight of facilities handling hazardous materials.

Investigators said that on the night of the accident, ink base materials -- including a volatile mixture of heptane and propyl alcohol -- continued to heat and then boil after all the employees left work late in the afternoon. The heating was controlled by a single, manual valve that needed to be closed by an operator to prevent the 3,000-gallon tank from overheating.

The building ventilation system was turned off at the end of the workday -- a routine procedure -- and vapor coming out of the unsealed tank spread throughout the production area and then ignited from an undetermined source, possibly a spark from an electrical device. The blast from the Nov. 22, 2006, explosion ripped through the adjacent Danversport neighborhood; at least 16 homes and three businesses were damaged beyond repair, and approximately 10 residents required hospital treatment for cuts and bruises.

"The community damage was the worst we have seen in the ten-year history of the Chemical Safety Board," said CSB board Member William Wright, who accompanied the investigative team to the accident site.

The facility, shared by ink manufacturer CAI and paint manufacturer Arnel, was completely destroyed by the explosion and ensuing fire and has not been rebuilt.

Wright said, "The immediate cause of the accident was the overheating of a highly flammable mixture for many hours. We found an underlying cause was CAI's failure to conduct a hazard analysis or other systematic review to ensure flammable liquids were safely handled during the manufacturing process."

"The company did not have automated process controls, alarms, or other safeguards in place. The standard practice at the company was to shut off ventilation at night -- to retain heat in the building and to allay residential complaints about fan noise," Wright said. "When the mixture continued to overheat -- absent automatic shutoffs and proper ventilation -- the vapor accumulated and filled much of the building over a period of hours. Without safeguards, it is likely that a small but foreseeable human error led to disaster."

CSB Lead Investigator John Vorderbrueggen, P.E., stated that Massachusetts state fire regulations and local enforcement should be improved to better protect communities and employees. He said, "The existing Massachusetts fire codes -- as well as federal OSHA standards -- have requirements for ventilation of flammable vapors to prevent dangerous accumulations inside structures. But Massachusetts has not adopted the most current national fire codes for flammable liquids. Our investigation also found that while the state requires local fire departments to periodically inspect facilities that handle flammable materials, the laws do not specify any inspection frequency or criteria for conducting those inspections."

More information on the CSB investigation can be found at www.csb.gov.

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