The CSB found that the explosion was caused by a combustible polyethylene powder called ACcumist, that had accumulated above a drop ceiling. Some unknown event caused the accumulated dust to loft into the air where it was ignited, causing a huge explosion felt 25 miles away that destroyed the building and burned for days.
Accumist had been applied in a wet, slurry form, called "AC Slabdip," purchased from a company named Crystal, Inc, to rubber sheets to keep them from sticking together. The solution was then dried, using fans, and some of the dust was blown through the air. Although the main room was cleaned constantly, dust accumulated above the drop ceiling. Workers were aware of the dust accumulation above the ceiling, but had not been trained about the explosive properties of the dust.
West claimed that there was no way to know that the dust from the "Slabdip" slurry was explosive because the Crystal "Slabdip" MSDS did not contain warnings or refer users to NFPA 654, which provides guidance for preventing combustible dust explosions. The CSB investigation found, however, that West had in its possession MSDSs from the producer of ACcumist that contained cumbustible dust warnings, and that West had actually supplied the original batch of ACcumist to Crystal, formulated the first batch of Slabdip, and contracted with Crystal to manufacture the slurry. West claims that "Slabdip" and ACcumist are two unrelated products.
The CSB report determined four root causes of the accident at West: the company’s inadequate engineering assessment for combustible powders, inadequate consultation with fire safety standards, lack of appropriate review of material safety data sheets (MSDSs), and inadequate communication of dust hazards to workers.West CEO Don Morel stated that the company concluded, after a study of its own, that the explosion was a "result of a combination of unforeseen factors."
“If the good safety practices described in the National Fire Code and elsewhere had been followed at West, this tragic accident would likely have been avoided,” said CSB lead investigator Steve Selk. “We will therefore be recommending that the State of North Carolina make compliance with the dust code mandatory."
In addition to recommending that North Carolina’s Building Code Council adopt NFPA 654, the report calls on the state Department of Labor to identify the industries at risk for combustible dust explosions and conduct an educational outreach program to help prevent future accidents. The report urges increased training of North Carolina fire and building code officials on combustible dust hazards. It also recommends that West improve its material safety review procedures, revise its project engineering practices, communicate with its workers about combustible dust hazards, and follow safety practices contained in NFPA 654 at all company facilities that use combustible powders.
CSB investigators, disagree:
“If the good safety practices described in the National Fire Code and elsewhere had been followed at West, this tragic accident would likely have been avoided,” said CSB lead investigator Steve Selk. “We will therefore be recommending that the State of North Carolina make compliance with the dust code mandatory.”The CSB is also investigating two other fatal dust explosions, including a 2003 explosion at CTA Enterprises in Corbin, Kentucky that killed seven employees and injured 42. The CSB will spend the next year and a half conducting a comprehensive study of combustible dust hazards and what can be done to prevent them. There is currently no OSHA standard covering combustible dust in industry, with the exception of grain dust. NFPA 654 is a good preventive standard, although other fire codes are not as comprehensive and state enforcement of NFPA 654 is generally weak.
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