My heart goes out to the families and victims of both central B.C.'s sawmill wood dust explosions. The inquest is now finished.
As a former industrial ventilation engineer I note that both explosions happened during winter's icy grip - to me this is not a coincidence. To control wood dust build-up, large volumes of inside air are extracted, but equal volumes of evenly-distributed tempered air (at 20C AND 30% RH [recommended by WorkSafeBC]) to replace the air extracted is just as important.
A relevant final report on Nova Scotia dust explosions concluded risk factors such as humidity levels and water content in materials can elevate the risk of explosion.
Moist dust requires a higher ignition temperature than dryer dust.
Also, when humidity levels are low, like those seen in winter months, dust can easily disperse and ignite, increasing the risk. In fact, industrial accident investigations by the U.S. Chemical Safety Board found that seven out of eight fatal combustible dust explosions from 1995 to 2009 occurred during cold winter months when these weather conditions were most prominent.
Ron C. Langille