Article Archive
Blast Report Issued
Ink-mixing tank left heating overnight allowed solvent vapor to accumulate
Volume 23. No 4

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

?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 the ink manufacturer did not follow regulations or appropriate good practices for the handling of flammable solvents, and the CSB 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 explosion occurred at approximately 2:46 a.m. on Nov. 22, 2006.

The blast ripped through the adjacent Danversport neighborhood, waking sleeping residents as windows were blown into bedrooms and shattered, ceilings fell, and belongings and appliances flew about. The blast wave damaged scores of homes. At least 16 homes and three businesses were damaged beyond repair, and approximately ten 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 the ink manufacturer and a paint manufacturer, was completely destroyed by the explosion and ensuing fire and has not been rebuilt. The paint manufacturer ceased operations, while the ink manufacturer continued to produce water-based inks at another facility.

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 (the company'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., said Massachusetts state fire regulations and local enforcement should be improved to better protect communities and employees.

"The existing Massachusetts fire codes - as well as federal OSHA standards - have requirements for ventilation of flammable vapors to prevent dangerous accumulations inside structures," Vorderbrueggen said. "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."

The destroyed 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.

Under the General Laws of Massachusetts, the plant was required to have land-use licenses for flammable materials. The only license, first issued to a predecessor company in 1944 and re-registered annually thereafter, initially authorized the presence of 250 gallons of "lacquer." In 1955, the property owners were granted an amended license by the Danvers Board of Selectmen to store and use 6,000 gallons of "miscellaneous" flammable materials.

By the time of the accident in 2006, the registration record on file with the Town of Danvers referenced a "license" to store and handle up to 11,500 gallons of "miscellaneous" flammable materials. However, the CSB found no record of such a license in the Danvers town files. Therefore, the CSB concluded, the current licensed amount was 6,000 gallons, well below the more than 20,000 gallons of flammable liquid and more than 50,000 pounds of flammable solid, nitrocellulose, stored on site.

The CSB found Massachusetts law to be unclear on the requirements and procedures for towns to approve requests for increasing the amounts of flammables to be stored at industrial sites, including whether or how adjacent property owners should be notified of intended increases. The investigation also pointed out that the state's licensing and registration forms do not require information on the specific types and quantities of materials stored.

A CSB survey of six Massachusetts municipalities - including Boston, Worcester, Springfield, Danvers, Leominster, and Georgetown - found significant variability in how state licensing and registration laws are applied. Although the six municipalities issued a total of more than 400 flammable materials licenses, only two reported ever having denied a license application.

In addition to a license, Massachusetts regulations require companies to obtain separate permits from the local fire department for the storage of flammable liquids, gases and solids. However, at the time of the explosion in Danvers, no permits had been obtained by or issued to CAI or Arnel, except an expired permit for underground storage tanks. The lack of permits had not been previously identified by the fire department.

Based on the quantities of flammable materials used, the ink manufacturer (not the paint manufacturer) was required to comply with OSHA's Process Safety Management standard, which would have required the company to conduct a process hazard analysis. Such a review could have identified the need for more sophisticated process control equipment, operator checklists and continuous building ventilation. The standard also required the use of written operating procedures, which can reduce the occurrence of human errors.

However, the ink manufacturer's management stated the company was not aware of the Process Safety Management standard's existence and had not implemented its requirements. OSHA had not inspected the facility prior to the accident.

Finally, the report stated that national model fire codes developed by the National Fire Protection Association (NFPA) and the International Code Council (ICC) did not provide sufficient safeguards for flammable liquids heated inside buildings. The standards - which were voluntary unless specifically adopted by states and localities - contained ambiguous language concerning process vessels and did not explicitly require automatic shutdown or cooling systems to prevent accidental overheating and the uncontrolled release of flammable vapor.

The CSB investigated a similar accident in 2006 at a Chicago-area concrete products company, where a vessel filled with heptane accidentally overheated inside an unventilated building, causing an explosion that killed a driver and caused property damage.

The investigation report made numerous safety recommendations, which will be considered by the Board. The report called on the NFPA (based in Quincy, MA) 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 liquids from overheating.

The report called on 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 called 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), to develop standards and a mandatory frequency for fire department inspections of manufacturing facilities, and to require license and registration forms to specifically list the type and quantity of each hazardous material.

Pending completion of the recommended changes at the state level, the report called for the Town of Danvers to undertake similar initiatives for certification, licensing and inspection. Additionally, specific safety recommendations were directed to CAI, in the event the company resumes solvent-based processing at another location. The draft report's findings, statements of cause and recommendations were all subject to approval by a vote of the board and were subject to change.

The CSB is an independent federal agency charged with investigating industrial chemical accidents. The agency's board members are appointed by the president and confirmed by the Senate. CSB investigations look into all aspects of chemical accidents, including physical causes such as equipment failure as well as inadequacies in regulations, industry standards and safety management systems.

The board does not issue citations or fines but does make safety recommendations to plants, industry organizations, labor groups and regulatory agencies such as OSHA and EPA. Visit the CSB Web site at


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F: (979) 690-7562

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