British Columbia does not directly monitor for risk of dust explosions in sawmills or other industrial settings, leaving it up to employers to ensure that they control hazards in the workplace.
Following a deadly explosion at the Babine Forest Products mill two weeks ago, WorkSafe BC confirmed that its regulations governing combustible dust contain no specific limits, leaving employers to extrapolate what is safe from guidelines.
Investigators are now trying to piece together what triggered the Jan. 20 blast that killed two men and injured 19 other workers. As one line of inquiry, they'll be seeking the testimony of safety inspectors who had observed unusually dry sawdust in the mill in recent months.
"There isn't an agency that has a mandate to monitor airborne explosive limits. It's the employers' responsibility in the province of B.C. to ensure a healthy and safe workplace," said Al Johnson, WorkSafe BC's regional director. "As the regulator responsible to ensure compliance, if we believe they are not doing that then we'll go in and evaluate … but it's fairly infrequent that we do that."
Mr. Johnson said enforcement is a subjective affair. "The regulation is performance-based. They are not allowed to let dust accumulate to a level that could cause combustibility."
WorkSafe BC inspectors did measure air quality at the mill in November and concluded that workers were exposed to unsafe levels of dust in the air. The mill was ordered to remedy the problem by the end of January.
But those levels of airborne dust were far from potentially explosive levels, according to a U.S. expert in dust explosions.
John Astad of the Combustible Dust Policy Institute said that the probability and severity of combustible-dust fires and explosion rise when the moisture content falls in a raw material used in an industrial operation. Mr. Astad said there are hundreds of combustible dust-related fires in U.S. industrial facilities each year, but only a small number of explosions. Those incidents rarely cause injury or death. Catastrophic explosions are very rare.
Sawmill owners are expected to maintain regular "housekeeping" to remove dust buildup. He agreed that a small explosion from any number of sources can shake free surface dust in the building, triggering a larger explosion. "That's the fire mechanics of a dust explosion," Mr. Johnson said. "But at this particular site, it's too early to speculate. The investigation will look at all of those things."
Investigators are also reviewing the findings of a B.C. Safety Authority report following a small dust explosion that led to a major fire at the mill last February. However, the sawmill wasn't inspected by the local fire department because it was built on a native reserve.
Jim McBridge, the Burn Lake fire chief, said in an e-mailed response that his crews carried out "familiarity tours" to ensure they knew where fire hydrants and hoses were laid out. But, he added: "As the mill site is outside my area of jurisdiction, we have never carried out a formal fire inspection."
He said that responsibility was left to WorkSafe BC and the B.C. Safety Authority, which inspects electric, rail and gas systems.
Editor's note: John Astad of the Combustible Dust Policy Institute said that the probability and severity of combustible-dust fires and explosions rise when the moisture content falls in a raw material used in an industrial operation. He did not refer specifically to the sawmill in Burns Lake, B.C. nor to the risk posed by drier wood from trees killed by pine beetles. Mr. Astad said there are hundreds of combustible dust-related fires in U.S. industrial facilities each year, but only a small number of explosions. Those incidents rarely cause injury or death. Catastrophic explosions are very rare. Incorrect information appeared in an earlier version of this story. This version has been corrected.