To the editor;
The potential for explosive dust fires is well understood in many industries. When the forest industry was thriving, general mill clean-up was given a high priority where I worked.
When company profits got squeezed by unfavourable markets, clean-up was reduced to save money. Processing bone-dry beetle-killed trees increases the need for additional clean-up.
Several years ago I was involved in the installation and maintenance of a ‘baghouse’. This baghouse is a huge vacuum cleaner that is used to safely collect the powdery wood dust created when plywood is sanded.
The first line of defence against explosive combustion in a baghouse is an automated spark detecting system coupled to water nozzles.
The next defence is an automatic deluging of the inside of the baghouse by numerous sprinkler heads.
According to what I have read, dust explosions can occur in stages. If an ignition source occurs in a dusty area, a small explosion can result which might create a shock wave capable of shaking more dust off surrounding structures. If the dust-to-air mixture reaches a critical ratio, a secondary explosion can occur. Depending on the circumstances, a series of cascading explosions can occur in rapid, almost instantaneous, succession.
The BC mill owners and their insurance brokers knew there were risks, but tragically underestimated the hazards and the consequences. Hopefully lessons have been learned and similar mistakes will not be repeated.
Lloyd Atkins
Vernon, B.C.