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Preliminary Findings Confirm Blast at West Pharmaceutical Services
in Kinston, NC, Was a Dust Explosion Fueled by Plastic Powder
Used in Manufacturing
(Kinston, NC - June 18, 2003) Investigators from the U.S. Chemical
Safety Board (CSB) told a community audience here tonight that
last January's massive blast at medical device maker West Pharmaceutical
Services, which killed six workers and injured dozens more, was
in fact an explosion of fine plastic powder used in the manufacturing
of rubber products.
The dust explosion occurred above an area where rubber strips
were coated with moistened polyethylene powder, investigators
told the audience at the Kinston High School Performing Arts Center
auditorium. Although made from a plastic similar to that in milk
jugs, the powder when dry is as fine as talcum and is capable
of forming explosive mixtures in air, according to CSB test results
made public today.
"We held this meeting to brief the community on our findings
to date and hear from members of the public who were affected,"
said CSB Chairman Carolyn Merritt, who presided at the session.
"The full Board will convene here in Kinston when the staff
investigation is concluded to issue our final safety recommendations
in this case. The Board is deeply concerned by this event and
the subsequent plant explosion in Corbin, Kentucky, which claimed
seven lives. The dangers of explosive dust are not well known,
and helping industry to understand this insidious hazard certainly
will be a priority."
According to CSB lead investigator Stephen Selk "Our testing
has now confirmed that actual polyethylene powder recovered from
the plant ruins is explosive when mixed with air. The material
contains enough energy to account for the level of destruction
we observed," Selk continued. He also noted the heavy damage
had thus far prevented his team from determining the source of
the ignition that triggered the dust explosion.
"The polyethylene powder was used as a nonstick coating
for rubber sheeting made at the plant," Selk added. "During
the production process, the plant's ventilation system drew fine
dust particles into the space above an unsealed, suspended ceiling,
where the dust settled and built up."
CSB Investigator Angela Blair told the group that on January
29 the five conditions necessary for a dust explosion were all
met at the West plant: fuel, oxygen, dispersion, confinement,
and ignition. "The dust was the fuel. Dispersed in the air,
it formed an explosive mixture," Blair said.
Blair explained that by installing a suspended or false ceiling
years earlier, the company had inadvertently created an area where
dust could accumulate out of view, and also created a space where
a dust explosion could occur and spread. It is for these reasons,
Blair added, that unsealed ceilings are not recommended where
hazardous dusts may be present.
Blair said investigators had recovered numerous ceiling tiles
that were scorched exclusively on the upper surface, confirming
the origin of the dust explosion within the overhead space. "Eyewitnesses
heard a sound like rolling thunder, as a rapidly expanding chain
of explosions moved through the ceiling space and literally tore
the building apart."
Blair and fellow investigator Lisa Long described the sequence
of events that ultimately led to the accumulation of dust. Raw
materials from a ground-level process area called the "kitchen"
were conveyed to a large mixer on the upper floor, where the rubber
was blended. The rubber mass was then dropped through a chute
to a mill back on the lower level, where it was rolled into flat
strips. The rubber strips were then fed through rollers and coated
using a tank of polyethylene powder slurried in water.
Ms. Blair said, "Once the rubber was dry, what remained
on the surface was a baby powder-like coating. But in the course
of drying the rubber, fans blew some of the fine powder into the
air. Much of the dust settled in the processing area, where the
company had a regular program to clean the dust from equipment,
walls, and floors. However, some dust also migrated through small
openings in the suspended ceiling, drawn by air conditioning intakes
located overhead. Over time the dust accumulated above the ceiling
-- out of normal view -- on tiles, conduits, ducts, and light
fixtures."
Lead investigator Selk pointed out that weeks prior to the explosion,
maintenance workers had seen layers of dust coating surfaces above
the suspended ceiling. "Tragically there was no recognition
of the explosion hazard posed by this accumulated dust,"
Selk said.
The CSB so far has conducted 93 detailed interviews of witnesses
to the West explosion, including plant workers and residents,
and participated in or reviewed the results of 177 additional
screening interviews conducted by the Bureau of Alcohol, Tobacco
and Firearms (ATF). The ATF investigation found the blast was
not the result of any criminal act.
The CSB is an independent federal agency that investigates chemical
accidents, determines root causes, and issues findings and safety
recommendations to prevent recurrence.
A report about West Pharmaceutical
Services Explosion
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