Combustible dust explosion risk is one of the most challenging issues fire safety professionals face today. On January 20, 2012 in Burns Lake, British Columbia, we were reminded why.

Shortly after 8pm, there was a combustible dust explosion and subsequent fire at the British Columbian mill run by Babine Forest Products. The blast killed two workers, injured 20 more, and caused immense physical damage to the facility. This tragedy rocked the small town and left many grasping for an explanation. An investigation by WorkSafeBC was concluded earlier this year, offering several insights into the incident, including yet another illustration of the importance of identifying the presence of combustible dust in the work place, and rigorously managing it within safe boundaries.

What factors contributed to the disaster?

In the months prior, local mills had been rushing to process local beetle-killed wood. Mountain pine beetles had caused quite a few headaches in the industry due to their destruction of local trees. In addition, beetle-killed wood is significantly drier, exacerbating the risk for large amounts of dust becoming airborne during processing.

But, beetles weren’t the only issue. Dramatically cold temperatures had caused a number of problems in the mill, including burst pipes and the clogging of wood waste removal systems. The backed-up wood waste provided ample fuel once the fire had been ignited. Additionally, one of the workers who was killed in the incident may have been performing routine checks of the building’s systems when he was caught in the blast. These checks were increased due to the harsh winter weather.

The breakdown of these various systems likely made the dust problem worse in the hours leading up to the incident, with significant sawdust accumulations piling on much of the equipment. Much like the sand pile in the bottom of an hourglass, as additional wood “fines” accumulated on the piles, they would eventually slide down the pile to surfaces and equipment below.

Some of these fines had fallen onto and infiltrated a V-belt guard on a drive motor reducer assembly for a waste conveyor. According to the WorkSafeBC report, the dust fire was initiated by heat from “friction within the motor-reducer V-belt guard.” Constant friction ignited the sawdust which began to smolder and eventually resulted in a flaming fire.  At some point, the flames from the fire were able to ignite a sufficient concentration of airborne dust—perhaps from another “landslide” of dust off the surface of the accumulation piles above, to initiate a deflagration resulting in an explosion within the basement space. This initial event in-turn caused several other secondary explosions that ultimately destroyed the sawmill building.

Could this have been prevented?

The Babine sawmill explosion is tragic not only due to its destruction of life and property, but also due to the fact that it could have been prevented. WorkSafeBC found the mill’s dust removal measures to be “ineffective in controlling airborne dust and the accumulation of other fine dusts in the sawmill”, the culprit that ultimately killed two workers.

Records show that Babine Forest Products had contacted a safety expert in the months preceding the blast, but that individual had not warned of a potential catastrophe. Rather, the company had been advised that employees were being exposed to excessive amounts of dust beyond permissible exposure limits for health and hygiene. They had been instructed to remedy the situation by the end of January, 2012, a date that is sadly inadequate in hindsight.

Further, the measures taken to combat airborne dust and dust accumulations were simply not good enough. Unfortunately, tragedy struck before the true gravity of this problem came to light. The Burns Lake mill explosion was a major wakeup call to others in the industry and a profound case study in fire prevention. In the next post, we’ll discuss the more nuanced causes that led up to the incident, how to recognize them and how to ultimately prevent future accidents.