US lab examining dust from Canadian sawmill, but blast cause still unknown
04 May 2012
Samples of sawdust from the Babine Forest Products sawmill in Burns Lake, British Columbia, which was the scene of devastating explosion on January 20, have been sent to a specialist laboratory in the USA, according to WorkSafe BC.
"If this (dust) is identified as being critical, that would give us the information to look at what happened and what we should do differently,” Roberta Ellis, vice-president of investigations at WorkSafe, said during an investigation update on May 3.
She said investigators have narrowed down potential fuel sources to dust, natural gas or propane, and are trying to find out whether a hot surface, friction from motors or saw blades, or electricity sparked the blast. They are also looking into whether production levels, the type of wood processed at the mill, the facility's ventilation system or the extremely cold weather increased the risk of an explosion.
"We are not looking at one single element in isolation," Ellis said. "We are looking at how they [could have] potentially caused this catastrophic event."
The type of wood being milled prior to the incident is also being examined, amid growing speculation that the processing of beetle-kill wood, known to produce a fine dry powder, has been responsible for a string of recent mill blasts.
The Burns Lake explosion killed two mill workers and injured 19, while another in Prince George on April 23 killed two and injured 12. WorkSafe is also investigating two non-fatal blasts last year at mills in Williams Lake and Armstrong, which went unreported to the agency.
Following the Burns Lake incident, WorkSafe ordered the inspection of 70 mills across the province to ensure safety standards were being met. Of those inspected, 90 violation orders were issued.
Freeman said the Prince George site was one of those inspected - on March 15. An earlier inspection report, dated Februry 6, noted that an accumulation of wood dust, and the requirement to prevent build-up was discussed with the mill managers. It was noted at the time that the airborne concentration of wood dust appeared to be below the exposure limit.
Ellis said the investigation into the Burns Lake explosion will take another two to three months. Arson and lightning strikes have been ruled out as an ignition source, she said, adding that nothing indicates hot oil, hydraulic oil, gear oil, or oxygen and acetylene served as fuel sources. Exhaust and ventilation systems are also being looked at, as is the effect extreme cold weather may have had on the mill's water pipes and misters.
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