Controlling Combustible Dust: Focus on Food

23 Feb
sugar refinery

Food Safety / Safety

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There is a wide range of agricultural and food products that create fire and explosion risks and hazards, including flour, grain, sugar, spices, cereal, flavoring additives, and many more. Dusts produced in any industry present challenges, but when manufacturing and processing food products, dusts can create the following major threats:

  • Airborne dust can cause serious harm to human (employee) health by causing physical ailments ranging from dermatitis to occupational asthma to lung cancer.
  • Dust can create the potential for cross contamination and encourage the spread of pathogens and allergens within the food processing plant.
  • Dust may become combustible and serve as the source for explosions that harm workers, damage machinery, and destroy buildings/corporate reputation.

About Combustible Dust

The food industry is responsible for the largest percentage of combustible dust incidents in the U.S.—ranging anywhere from 24-43% depending on the timeframe and the source. One of the most notable combustible dust incidents in history involved a secondary explosion at the Imperial Sugar refinery in 2008, which killed 14 people and injured 40.

According to the Occupational Safety and Health Administration’s (OSHA) definition, combustible dust is “a solid material composed of distinct particles or pieces, regardless of size, shape, or chemical composition, which presents a fire or deflagration hazard when suspended in air or some other oxidizing medium over a range of concentrations.”

A dust explosion occurs when all five elements of the Dust Explosion Pentagon are present:

  • Ignition source
  • Oxygen
  • Confined area
  • Suspended cloud
  • Explosive dust

Combustible Dust Standards

The devastating 2008 sugar refinery explosion prompted the development of OSHA’s Combustible Dust National Emphasis Program (NEP), and yet, some 14 years later, there is still no combustible dust regulation. That doesn’t mean, however, that there are no standards for managing and controlling combustible dust. In fact, there are several agencies involved in ensuring the food industry is appropriately managing the various hazards associated with combustible dust, including:

  • National Fire Protection Association (NFPA)
  • OSHA
  • U.S. Food and Drug Administration (FDA)

NFPA Codes

NFPA sets standards regarding combustible dust. In fact, there are at least ten NFPA standards related to combustible dust (NFPA 61, 68, 69, 77, 484, 499, 652, 655, 664, 654). While these standards and codes are not law, per se, they are enforced by OSHA and referenced extensively. Most insurance agencies and local fire codes state that NFPA standards shall be followed as code.

NFPA’s most recent Standard on the Fundamentals of Combustible Dust (NFPA 652) covers the fundamental requirements for managing combustible dust fires and explosions and is an excellent starting point. NFPA 652 requires owners/operators to:

  • Determine the dust’s combustibility and explosibility hazards based on laboratory testing or historical facility data.
  • Conduct a Dust Hazard Analysis (DHA) to identify and evaluate potential dust fire and explosion hazards based on Kst (i.e., explosibility) values. Note: The DHA is a relatively new requirement—similar to OSHA’s Process Hazard Analysis as part of the Process Safety Management (PSM) program—used to assess risk and determine the required level of fire and explosion protection from combustible dust.
  • Manage all the identified fire, flash fire, and explosion hazards identified in the DHA.
  • Establish a written safety management system, including operating procedures and practices, training, incident investigation, and employee participation, to prevent and protect against the hazards.

NFPA 61 – Standard for the Prevention of Fires and Dust Explosions in Agricultural and Food Processing Facilities specifically covers facilities engaged in dry agricultural bulk materials or manufacturing and handling starch.

OSHA National Emphasis Program (NEP)

While OSHA has no formal standard for managing combustible dust, the agency published the Combustible Dust NEP in 2009, which outlines policies and procedures for inspecting workplaces that create or handle combustible dusts. The NEP heavily references the standards published by NFPA. It also references several other OSHA standards, including:

  • 1910.22 Housekeeping
  • 1910.307 Hazardous Locations
  • 1910.1200 Hazard Communication
  • 1910.269 Electric Power Generation, Transmission, and Distribution
  • 1910.272 Grain Handling Facilities
  • General Duty Clause, Section 5(a)(1) of the OSH Act

The General Duty Clause may be the most important of these, as it essentially gives OSHA the right to issue a citation any time employers fail to keep their employees safe from recognized hazards, including those hazards associated with combustible dust. Companies must control dust emissions to protect workers from exposure. If OSHA determines that even a very low Kst (i.e., low explosibility) dust is present in a facility with no explosion protection in place, the agency will issue citations and fines for lack of compliance.

Incidentally, OSHA published the Occupational Exposure to Flavoring Substances – Safety & Health Information Bulletin (SHIB) in 2010, cautioning that volatile organic compounds (VOCs) and respirable dust may be produced when handling many powdered flavoring formulations or spices. Inhalation of these substances may result in exposure directly to the small airways of the lungs.

FDA: Food Safety Modernization Act (FSMA)

In addition to meeting NFPA standards and OSHA guidelines, food companies must meet the requirements of FDA’s Food Safety Modernization Act (FSMA). FSMA requires food processing facilities to implement measures to ensure contamination hazards will be minimized or prevented. This includes developing a Hazard Analysis and Critical Control Points (HACCP) Plan with preventive controls for processes, food allergens, foreign objects, sanitation, and supply chain, as well as complying with Good Manufacturing Practices (GMPs).

Best Practices

Combustible dust itself is not avoidable, but the related consequences are. When it comes down to it, poor housekeeping is the biggest root cause of combustible dust issues. Many risks and hazards can be avoided by effectively cleaning the facility and equipment to remove contaminants before they become widely dispersed. Diligent housekeeping, combined with installing a dust collection system that is properly designed for the operation, can significantly reduce airborne dust and help mitigate a primary or more deadly secondary explosion.

If you work in the food industry, combustible dust is a concern. Make sure you understand the applicability of all the standards and codes, particularly the requirements under the various NFPA standards. The following may be required to keep your facility in compliance and your employees safe:

  • Laboratory screening to determine if your powders are combustible or explosible.
  • DHA to identify and evaluate potential dust fire, flash fire, and explosion hazards.
  • Full analytical testing to determine explosion strength (Kst), minimum ignition energy, maximum safe storage temperature, and more.
  • A written management system that documents operating procedures and practices for the ongoing management of dust fire, flash fire, and explosion hazards.
  • Initial and ongoing training for operating, engineering, and management staff to build competency and understanding.

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