CAI/Arnel left a solvent tank heating overnight and leveled a Danvers neighborhood

At about 2:46 a.m. on November 22, 2006, an explosion ripped through the CAI/Arnel ink and paint plant in Danvers, Massachusetts and flattened parts of the Danversport neighborhood. The U.S. Chemical Safety Board found that a 3,000-gallon mixing tank holding 10,000 pounds of heptane and propyl alcohol had been left heating on a single manual steam valve after the operator went home. Ventilation was shut off every night — the company's routine, meant to retain heat and quiet fan noise for neighbors — so vapor from the unsealed tank accumulated for hours until something ignited it.

The blast, compared by officials to a 2,000-pound bomb, was felt in New Hampshire and knocked the steeple off a church half a mile away. At least 16 homes and three businesses were damaged beyond repair, about ten residents were treated at hospitals, and the fire department evacuated more than 300 people from a half-mile radius. No one was killed — Governor Mitt Romney called it a Thanksgiving miracle — and the CSB said the community damage was the worst in its ten-year history. The plant was destroyed. Arnel ceased operations; CAI later resumed making water-based inks in Georgetown.

The CSB's final report, approved May 13, 2008, found CAI had never conducted a hazard analysis and had no automated controls or alarms. The licensing trail was worse: the property's flammable-materials license, first issued in 1944, covered 250 gallons of lacquer, then 6,000 gallons of 'miscellaneous' flammables from 1955 — while the site held more than 20,000 gallons of flammable liquids and over 50,000 pounds of nitrocellulose. The town had no record of the 11,500-gallon license the company referenced, and the last fire inspection, in 2002, looked only at the new sprinkler system.

16 homes and 3 businesses damaged beyond repair; 300 residents evacuated; plant destroyed; Arnel never reopened

CAI ran flammable-solvent batch heating on a single manual valve with no alarms or automatic shutoffs, so safety depended on one operator remembering one task every evening.

The company's own nightly routine shut off building ventilation, guaranteeing that any leak would accumulate in a sealed structure for hours.

The company never performed a hazard analysis, so no one had ever mapped what an overnight boil-off of heptane and alcohol would do inside the building.

The regulatory layer failed in parallel: a grandfathered license capped the site at 6,000 gallons while it stored over 20,000, and the last inspection checked only the sprinklers.

A single manual valve is not a safeguard. If a process can hurt people while nobody is there, it needs automatic shutoffs, alarms and ventilation that keep running when the workers go home.

The CSB Board approved the final report at a community meeting in Danvers on May 13, 2008, recommending changes to national fire codes and to Massachusetts licensing and inspection procedures. The companies paid a large settlement, and the site later became a boat yard. Arnel never returned; the Danversport block was rebuilt with new homes, and residents still gather each November — ten years on, trading memories of fleeing in dress shoes because their sneakers were full of glass.