The findings appear to dampen speculation that sawdust from overly dry beetle-kill logs may have been responsible for the disasters.
Last month, WorksafeBC sent green wood dust samples to a lab in the U.S. to be compared against dust from beetle-kill wood.
The results show that when dust from green wood — wood that was felled when the tree was still alive—has a moisture content under five per cent, and when the dust particle is of a certain size, it can be just as explosive as beetle-kill wood when ignited.
Jeff Dolan, WorksafeBC's director of investigation, said the lab results are not specific to the mill explosions that happened earlier this year at Burns Lake and Prince George, where the establishments were processing primarily beetle-kill wood.
But they do serve as a warning to mills to be more vigilant about the combustibiilty of both green wood dust and beetle-kill wood dust, he said.
"The evidence we're receiving as the investigation proceeds is all dust, under circumstances, can have that volatility," he told reporters on Thursday.
"The mills still in operation can't consider themselves excluded because they're not milling beetle-kill wood."
The explosions killed four workers.
Alan Little, 43 and Glenn Roche, 46, died at the Lakeland Mills explosion in Prince George in April.
The victims of the Babine Forest Products mill fire in Burns Lake three months prior were 45-year-old Robert Luggie and 42-year-old Carl Charlie.
In May, WorksafeBC ordered all of B.C.'s 300 or so mills to immediately get a grip on any dust problems. Mills were told they had fewer than two weeks to conduct a thorough inspection and implement an effective combustible dust control problem.
At the time, Dean Colville, a former sawmill worker who is now with the United Steelworkers' Union, said as more beetle-killed wood is being cut, sawmills are relying more heavily on processing the dead trees, causing what he said were "bomb-like" conditions.
Dolan didn't dismiss the anecdotes.
"We're confident that beetle-kill wood is explosive, but we want to make sure we have the scientific evidence to support that," he said.
Roberta Ellis, WorksafeBC's vice president of corporate services, said she expects the results of the two mill explosion investigations will be released in the fall.Suggest a correction