Build-up of chemical vapors cited in Danvers blast

US safety board is still assessing cause

Federal investigators have reached the preliminary conclusion that the build-up of chemical vapors inside a paint and ink factory in Danvers was the fuel that ignited a massive explosion in November that essentially destroyed a neighborhood in seconds, officials said yesterday.

The lead investigator from the Chemical Safety and Hazard Investigation Board also said that research is still underway into the possibility that natural gas collected inside the building.

But John B. Vorderbrueggen, the board's lead investigator, stressed that the most likely cause is solvent fumes building up inside the structure on Water Street that was used by two companies -- CAI Inc., a privately held company that manufactured inks, and Arnel Co., Inc., a custom paint maker. Both companies used highly explosive chemical solvents in manufacturing, he said.

"If you can't control the vapors, then you minimize them," he said. "In this situation, we apparently had neither of those features. We didn't minimize the vapors, and we didn't control the vapors. We didn't ventilate it safely out of the building. And then it found an ignition source."

He added, "The more probable fuel is one or more of the solvents that were being used by the companies inside the building," he said.

The 2:45 a.m. blast on Nov. 22 destroyed the building, damaged 70 houses and businesses, and left hundreds homeless. The Danversport neighborhood is still struggling to recover from the devastation.

In a statement released last night, CAI said the preliminary conclusions were unexpected. "We are surprised by the remarks of the US Chemical Safety Board, given the Board's previous public statements that a final determination of cause could take as long as one year," the statement said. "Given the complexity and size of this explosion, as well as the extent of scientific analysis and sophisticated computer modeling that remains to be completed, it is simply too early in the investigative process to determine with any degree of certainty what caused the blast."

An Arnel Co., Inc. spokesperson could not be reached for comment.

A spokeswoman for State Fire Marshal Stephen D. Coan said the state inquiry into the cause and origin of the blast continues and has not yet reached any conclusion.

In a phone interview, Vorderbrueggen said there are two theories on how the solvent fumes may have concentrated.

He said the first theory is that a leaking drum of solvents spewed fumes into the structure and were not properly ventilated by the building's systems.

The second idea, he said, is that a worker left a heat source going on the open-topped vats that the companies used to mix and make their products when the last person left the facility at 6 p.m. that day. During the succeeding hours, the fumes built up, he said.

Because the building was destroyed, Vorderbrueggen said, investigators may never learn what ignited the fumes. He said the companies appeared to have taken steps prior to the blast to properly ventilate the building and to use electrical systems that reduced the occurrence of random sparks.

He said the companies have provided the board with the recipes for their products. Investigators will now try to recreate conditions inside the plant in a laboratory to further confirm their preliminary conclusions.

Vorderbrueggen said natural gas cannot yet be completely eliminated because evidence of natural gas was found in soil testing performed after the explosion. He said it was not clear whether that gas was naturally occurring from decomposing vegetation or leakage from gas networks in the neighborhood.

The neighborhood is host to a high-pressure transmission line and to gas services to houses in the neighborhood. The factory did not use gas, but was heated with oil, he said.

The board hopes to discuss more detailed findings during a community meeting in the spring, Vorderbrueggen said.