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A fire fueled by sawdust damaged a Lisbon, N.H., furniture plant on Sept. 29.
Responders say a spark from the plant's boiler ignited sawdust on the roof of the DCI furniture plant. It took multiple departments an hour and a half to control the blaze, WCAX reports. Lisbon Fire Department's Lt. Dave Combs outlined the fire suppression techniques that kept the blaze from spreading:
"We had one crew go on the interior and try to attack from inside. We pushed the fire out this way and once we peeled the roof off, we were able to contain it to the roof," said Combs.
The roof was badly damaged, but the building remained intact.
A combustible material
Sawdust, along with many other industrial materials, wood, when finely powdered, can be ignited. If dust is airborne in high concentrations, electrostatic discharge from machinery, friction, hot surfaces, or fire are all potential triggers to an explosion.
Stationary dust, too, poses a threat – even in small amounts. The National Fire Protection Agency warns that as little as 1/32 of an inch covered over 5 percent of a room's surface area presents a significant explosion hazard.
This is because stationary dust on the floor can be lofted and ignited by an unrelated event. In a 2006 report, the U.S. Chemical Safety and Hazard Investigation Board defined this as a secondary dust explosion. Blast waves can continue lofting dust particles, triggering proceeding explosions.
The Chemical Safety Board report details a 2003 explosion at the West Pharmaceutical Services facility in North Carolina. One of the building's operations was the production of rubber syringe plungers. During the process, fine polyethylene powder was produced as a byproduct. Rather than fall to the ground, the plant's ventilation system drew some of the fine particles above a suspended ceiling where it collected.
Though some employees were aware of the dust, they were not trained about its hazards. Further, the Occupational Safety and Health Administration, the local fire department, an insurance underwriter, and an industrial hygienist all inspected the facility, but none identified the dust as a hazard.
Left undisturbed, the fine particles eventually accumulated to a height of a quarter of an inch, which was enough to trigger a deadly event.
On January 29, 2003 a small amount of dust ignited, causing an explosion that spread quickly across the facility. The design of the building allowed the blast to spread along the false ceiling, triggering secondary explosions as it moved. Six workers were killed and 38 were injured.
The CSB outlined lessons to be learned from the tragic event. Most vital is the need for good housekeeping. Minimizing dust accumulations by using dust collectors, eliminating flat surfaces or sealing hard-to-clean areas are effective techniques. Dust accumulated above a suspended ceiling, which also triggered the Lisbon, N.H., fire, can be reduced as a risk if the area is sealed shut.
Industrial Safety News brought to you by Safety Systems Technology, Inc., leaders in fire and gas detection.