According to OSHA, since 1980, more than 130 workers have been killed and more than 780 injured in combustible dust explosions. Recent incidents have significantly heightened awareness of combustible dust hazards:

• 1999: Natural gas explosion resulted in coal dust explosion—6 fatalities and 14 injuries;
• 2002: Rubber fabricating plant: 5 Fatalities and 6 Injuries—caused by dust accumulation;
• 2003: West Pharmaceuticals: 6 Deaths, numerous injuries, hundreds of job losses—plastic powder accumulated above suspended ceiling;
• 2008: Imperial Sugar: Sugar dust explosion—14 fatalities and 36 injuries

Combustible Dust Fundamentals

Elements needed for dust explosion:

1. Combustible dust (Fuel)
2. Ignition source (Heat)
3. Oxygen in air (Oxidizer)

Additional Elements Required:

1. Dispersion in sufficient quantity/concentration
2. Confinement of dust cloud

OSHA and combustible dust

Due to the large number of combustible dust explosions previously discussed, OSHA has implemented a national emphasis program on combustible dust: CPL 03-00-008. In addition, on October 21, 2009 federal OSHA published an Advance Notice of Proposed Rulemaking (ANPR) as a preliminary step in the development of a combustible dust standard. Several of my clients have recently been contacted by OSHA concerning combustible dust safety.

Performing the combustible dust assessment

The first step in determining if a combustible dust hazard may exist at your facility is to perform a combustible dust assessment of your facility. Are combustibles dusts present at your facility? Is your industry normally associated as a combustible dust hazard?     

What is a combustible dust?

NFPA 654 (2013 Edition): “Standard for the Prevention of Fire and Dust Explosions from the Manufacturing, Processing, and Handling of Combustible Particulate Solids” defines a combustible dust as follows: “A finely divided combustible particulate solid that presents a flash fire hazard or explosion hazard when suspended in air or the process-specific oxidizing medium over a range of concentrations.” In addition, a combustible particulate solid is defined as: “Any solid material composed of distinct particles or pieces, regardless of size, shape, or chemical composition that presents a fire hazard.“

Typical dusts of concern

• Metal Dust – Such as Aluminum and Magnesium
• Wood Dust
• Coal and Other Carbon Dusts
• Plastic Dust and Additives
• Biosolids
• Organic Dust – Sugar, Flour, Paper, Soap, Dried Blood (e.g., slaughterhouses)
• Certain Textile Materials

Typical industries handling combustible dust

• Agriculture
• Food Products
• Chemicals
• Textiles
• Forest and Furniture Products
• Metal Processing
• Tire and Rubber Manufacturing
• Paper Products
• Pharmaceuticals
• Wastewater Treatment
• Recycling Operations (metal, paper, and plastic)
• Coal Dust – Coal Handling and Processing Operations

Safe Work Practices

If you handle combustible dusts you need to ensure safe work practices are utilized to minimize the potential for an explosion:

• Electrical Wiring: Must be Class II, Division (I or II), Group E, F, or G;
• Dust Control: Implement dust control measures to minimize dust release and accumulation – particularly on overhead structures;
• Ignition Control: Minimize sources of ignition that could result in an incident;
• Damage Controls: Equipment design to minimize danger/damage from an explosion;
• Training: Educate all affected employees (hourly and management) in hazards of combustible dusts and safe work practices

References

Listed below are OSHA and National Fire Protection Association (NFPA) standards and codes addressing combustible dust safety.

OSHA References

• Combustible Dust National Emphasis Program: CPL 03-00-008
• 29 CFR 1910.22 (Housekeeping)
• 29 CFR 1910.176 (c) [Housekeeping in Storage Areas]
• 29 CFR 1910.272 (Grain Handling Facilities)
• 29 CFR 1910.307 [Hazardous (classified) locations.]

NFPA References

• NFPA 61: “Standard for the Prevention of Fires and Dust Explosions in Agricultural and Food Processing Facilities”
• NFPA 68: “Standard on Explosion Protection by Deflagration Venting”
• NFPA 69: “Standard on Explosion Prevention Systems”
• NFPA 70: “National Electrical Code”
• NFPA 499: “Classification of Combustible Dusts and of Hazardous (Classified) Locations for Electrical Installations in Chemical Process Areas”
• NFPA 654: “Standard for the Prevention of Fire and Dust Explosions from the Manufacturing, Processing, and Handling of Combustible Particulate Solids”
• NFPA 664: “Standard for the Prevention of Fires and Explosions in Wood Processing and Woodworking Facilities”

Summary

From an employee as well as facility standpoint, combustible dusts pose a serious safety risk for many companies. Make sure you are prepared by assessing the risk at your facility and following combustible dust safe handling practices.

Contact us with questions on this article or to schedule a combustible dust assessment at your facility.

If you have any questions concerning this article or other safety issues, please contact W. Jon Wallace, “The Safety Guru”, at 919.933.5548 or by e-mail