The Nov. 22, 2006 explosion occurred when a 10,000-pound mixture of flammable solvents overheated in an unattended building. According to CSB’s report, it appears an operator inadvertently left the steam heat on the mixing tank 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. 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.
An Explosive Situation
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 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, but when vapor came out of the unsealed tank, it spread throughout the production area and then ignited from an undetermined source, possibly a spark from an electrical device.
The blast ripped through the adjacent Danversport neighborhood, waking sleeping residents as windows shattered, ceilings fell and belongings and appliances flew about. At least 16 homes and three businesses were damaged beyond repair, and approximately 10 residents required hospital treatment for cuts and bruises. The fire department ordered the evacuation of more than 300 residents within a half-mile radius of the facility.
"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. "As others have noted, this explosion had a serious potential for life-threatening injuries and fatalities."
The facility, shared by ink manufacturer CAI and paint manufacturer Arnel, was completely destroyed by the explosion and fire and has not been rebuilt. Arnel ceased operations, while CAI continues to produce water-based inks at a facility in Georgetown, Mass.
CSB: CAI Lacked Safeguards
“The immediate cause of the accident was the overheating of a highly flammable mixture for many hours,” Wright said. “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."
Wright added that the company did not have automated process controls, alarms or other safeguards in place. The company’s standard practice was to shut off ventilation at night to retain heat in the building and to allay residential complaints about fan noise. But when the mixture continued to overheat, the lack of automatic shutoffs and proper ventilation allowed 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,” Wright said.
Improved Fire Codes Needed
CSB Lead Investigator John Vorderbrueggen, P.E., said Massachusetts state fire regulations and local enforcement should be improved to better protect communities and employees. He said that while existing state fire codes and OSHA standards have requirements for ventilation of flammable vapors, 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,” Vorderbrueggen said.
The CAI/Arnel facility was last inspected by the fire department in 2002, but the inspection focused on a newly installed fire suppression system and did not identify fire code or permitting violations. In addition to the inadequate ventilation that contributed to the accident, non-causal fire code violations included improper venting of flammable storage containers, use of improper hoses for flammable service and lack of fire walls.
The report stated that national model fire codes developed by the National Fire Protection Association (NFPA) and the International Code Council (ICC) do not provide sufficient safeguards for flammable liquids heated inside buildings. These voluntary standards contain ambiguous language concerning process vessels and do not explicitly require automatic shutdown or cooling systems to prevent accidental overheating and the uncontrolled release of flammable vapor, CSB said.
CSB’s report calls on the NFPA and the ICC to revise the national fire codes to prohibit the heating of flammable liquids inside buildings in unsealed tanks that do not vent outside and to require automatic safeguards to prevent overheating.
The report also advises the Massachusetts legislature to require companies to certify compliance with state fire codes and safety regulations, to require public input before allowing companies to increase the quantities of licensed flammable materials and to require the Office of the State Fire Marshal to audit localities' compliance with licensing and permitting requirements.
Other proposed recommendations call on the state's Office of Public Safety to adopt current national fire codes for handling flammable liquids (NFPA 30) and manufacturing of coatings (NFPA 35). It also proposes developing standards and a mandatory frequency for fire department inspections of manufacturing facilities, as well as requiring license and registration forms to specifically list the type and quantity of each hazardous material.
Specific safety recommendations were directed to CAI in the event the company resumes solvent-based processing at another location.
On May 13, CSB voted to approve the draft investigative report and safety recommendations. The report, along with a new 10-minute video of the explosion and its impact on the community, can be found on CSB’s Web site, http://www.csb.gov.