OSHA Must Address Combustible Dust Events

By Laurel Maloy, contributing writer, Food Online

Are you overlooking this potentially-fatal and highly-dangerous aspect of your food processing facility?  OSHA has downgraded its importance, but your company should not

Between 1980 and 2013 the U.S. Chemical Safety Board (CSB) has documented 331 incidents of explosions and fire due to combustible dust. These preventable accidents caused the deaths of 148 people and injured almost 900. The data is lacking for years between 2005 and 2008, though the trend is increasing, with the five years leading up to 2013 accounting for 29 deaths and 161 injuries.

Related: Handling Combustible Dusts

The CSB has been pressing the Occupational Safety and Health Administration (OSHA) to publish a comprehensive standard on the issue of combustible dust — in fact, this is the first item on CSB’s Most Wanted Safety Improvement list. Since 2008, when then Senator Obama said it was “long past time” for OSHA to act on a combustible dust rule, it has been on OSHA’s “To-Do” list. OSHA made some inquiries in April of 2009, leading everyone to believe rulemaking was in progress. However, there has been no rule drafted or published. Now, more than six years after the fact, we find this critical issue has been relegated to OSHA’s “long-term actions” category.  Just before Thanksgiving 2014, the White House silently released its regulatory agenda, officially downgrading this potentially deadly and volatile safety concern.   

The dusts food processors must be concerned with are from grain, powdered milk, flour, cocoa, starch, cellulose, sugar, maltodextrin, and other sources. The National Fire Protection Association (NFPA) defines a combustible dust as “a particulate solid that when suspended in air or some other oxidizing medium over a range of concentrations, regardless of its size or shape, presents a deflagration or fire hazard.” The gist of the matter is that any particle with a surface area to volume ratio greater than that of a 420 micrometer (μm) diameter sphere, as well as those having a 420 μm effective diameter or smaller, should be considered combustible. 

It doesn’t take much for an explosion to occur. A dust explosion has three elements:

1. Combustible dust is the fuel source
2. Any electrostatic charge, hot surface, pilot light, glowing ember, electric current, flame, or frictional heat will be the ignition source
3. The oxidizer is simply oxygen in the air

With these three elements in place, only two other conditions are required to create an environment favorable to a dust explosion. A dust cloud — created when dust particles are suspended in the air in high quantities — is the first requirement. The second is confinement within an area, such as a building, room, vessel, or even inside processing equipment. The explosions can then exponentially get worse, the primary explosion dislodging additional dust or damaging a collection system, contributing to and creating ever larger explosions. For anyone to escape unscathed is highly unusual, unless the area is not staffed at the time.

Related: Mitigating Dust Explosion Risks In Solid Powder Processing

Though food processors utilize Hazard Analysis and Critical Control Points (HACCP) to assess the potential for foodborne pathogenic contamination — HACCP would be an effective tool with which to monitor and control the potential for combustible dust accumulation and explosion. It is first necessary to recognize those finely milled materials that are capable of combustion, and then to examine the processes that use or produce them. OSHA has a Combustible Dust Poster available, listing more than 60 food-based combustible dusts. Finally, identification and actionable Critical Control Points (CCP) would include identifying these three elements:

1. Both open and hidden areas where combustible dusts may accumulate
2. The means by which the dust is dispersed into the air and how to control or minimize it
3. Potential sources for ignition or spark and how to damper or remove the threat

OSHA’s poster also discusses the measures by which dust and ignition can be controlled, as well as prevention and protection procedures your facility can take. However, this poster, along with the information it contains, has proven to be largely ineffective when it comes to reducing the incidents of combustible dust explosions. It is, however, an exceptional starting point for making a hazard assessment of your facility in regard to combustible dust.

Bear in mind that all of the potentially combustible dusts are not included on the poster. The material’s Material Safety Data Sheet (MSDS) may, or may not, provide the information necessary to determine the combustibility of a substance’s dust. Appropriate testing must be performed to definitively determine the explosive capacity of a particular type of dust. If your facility uses or creates any finely milled food products, testing is definitely an appropriate first action. Then, based upon test results, establish preventive measures with diligent housekeeping and administrative procedures put in place. Combustible dust explosions are fundamentally preventable; there is no good excuse for an accident that could have been prevented.