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When dust goes 'Boom!'

By Mari-Len De Guzman

Dust accumulation may be a nuisance at home but in certain workplaces, dust is a deadly accident waiting to happen.

“Combustible dust is a bigger issue than most people recognize. People don’t know what they don’t know,” said Laurence Polley, president of C&R Engineered Solutions Inc. Polley was one of the speakers at the recent Education Day event hosted by the Toronto Chapter of the Canadian Society of Safety Engineers.

Dust fire occurs when combustible dust is ignited or exposed to a source of ignition, and there is oxygen present. While there is little data on combustible dust explosions in Canada, the United States has effectively documented this hazard in recent years.

In 2006, the U.S. Chemical Safety Board (CSB) embarked on a comprehensive review of combustible dust. The agency found that between 1981 and 2006, there have been 281 combustible dust fires in the U.S., killing 119 people and injuring more than 700.

“When there is dust explosion, there is typically multiple fatalities and injuries, and extensive damage to property,” Polley noted.

During the CSB study, investigators found that one of the biggest issues involving combustible dust is inadequate description of dust hazards on the material safety data sheet (MSDS), and a general lack of awareness among workers of these hazards.

Watch: Safety Tips on Preventing Combustible Dust Explosion

In Canada, the MSDS is a requirement under the Workplace Hazardous Materials Information System (WHMIS). According to Health Canada, although the Controlled Products Regulations do not specify criteria for the explosibility of dust, “this does not preclude the supplier’s obligation to disclose information relating to this hazard as required by the existing requirements of the CPR.”

In its Dust Explosibility information sheet, Health Canada indicates that, “where applicable, MSDSs are to identify this hazard and disclose information on the appropriate engineering controls to prevent these explosions through, for example, information provided in pertinent guidelines such as those recommended in the standard issued by the National Fire Protection Association.”

Polley said in addition to the lack of awareness, other factors can contribute to dust explosions, including improper or poor housekeeping. For example, the use of compressor or other dust movers to clean up dust is a bad idea, Polley said. Instead, a vacuum system should be used to clean and remove combustible dust.

Proper equipment and building design is also essential, especially for industries that have a high-risk of dust explosions. These industries include: metal processing; wood product manufacturing; chemical manufacturing; food and pharmaceutical production; grain storage; rubber and plastic products fabrication; coal-fired power plants.

Some examples of combustible dust materials are coal, chemicals, wood dust, rubber, grain dust, sugar, flour, and some metals such as aluminum.

In his CSSE presentation, Polley outlined some “engineering considerations” for workplaces at high risk of dust explosions:

•    Is a pre-start health and safety review (PSR) required?

•    If the PSR was done, have you followed up on the recommendations (e.g. battery charging areas)?

•    Has the hazardous area been assessed by an engineer for Ontario Electrical Safety Code classification? Is the electrical equipment approved for the classification?

•    Are your forklifts rated for the classified area (505)?

•    Are your flammable storage cabinets grounded?

•    Do you have a good quality grounding and bonding installation where required?

•    Is the grounding and bonding system checked and verified on a regular basis?

•    Do you use approved equipment for ventilation, dust collection and housekeeping?

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