What You Need to Know About Dust Explosions

Over time, the accumulation of dust may become extensive. Those surfaces that are highly visible often are cleaned on a periodic basis and may present a very minimal hazard. However, “hidden” surfaces generally are overlooked. These include support steel, roof support members and trusses, equipment surfaces above eye level, light fixtures and elevated ductwork, piping or cable trays.

These problem areas are the areas that will draw the attention of OSHA inspectors and are the areas that safety professionals should concentrate on cleaning.⁴ The watchword in reducing the risk of dust explosions is housekeeping: cleaning up dust accumulation in all areas, visible or hidden.

The second aspect of reducing the dust explosion risk is to identify the hazardous nature of the accumulated dusts. Not all dusts present a fire or explosion risk. While it is preferred that all accumulated dusts be cleaned up for safety reasons, the emphasis here is to concentrate on those dusts that present a real fire or explosion risk.

Conduct an inventory of all the powdered materials within the facility and review material safety data sheets (MSDS) to determine if a risk already has been identified. In the event the MSDS is incomplete or if no MSDS exists for the powder under review, physical hazard testing may need to be conducted. Several NFPA publications^2,5,6,7 provide additional information on explosive and combustible materials. Of course, a hazard may be assumed to exist for all unidentified materials and a cleanup undertaken anyway.

Eliminating the problems involves the general housekeeping chores discussed above, but goes beyond that to address the sources of the primary dust and ignition sources. This involves a review of the process and process equipment to minimize any openings where dust can escape and to eliminate sources of heat, sparks, combustion, etc. wherever possible. To facilitate this process, OSHA and the Chemical Safety Board rely on the NFPA and their collection of codes, standards and guidelines, which will be discussed in Part 2 of this article.

References:

1. U.S Chemical Safety and Hazard Investigation Board, July 29, 2008.

2. NFPA 68-2007, Standard on Explosion Protection by Deflagration Venting, National Fire Protection Association, 2006.

3. NFPA 654-2006, Prevention of Fire and Dust Explosions from the Manufacturing, Processing and Handling of Combustible Particulate Solids, National Fire Protection Association, 2006.

4. CPL 03-00-008 Combustible Dust National Emphasis Program, 03/11/2008, U.S. Department of Labor, Occupational Safety and Health Administration, Washington, D.C.

5. NFPA 484-2009, Combustible Metals, National Fire Protection Association, 2009.

6. NFPA 495-2006, Explosive Materials Code, National Fire Protection Association, 2006.

7. NFPA 499-2008, Classification of Combustible Dusts and of Hazardous (Classified) Locations for Electrical Installations in Chemical Process Areas, National Fire Protection Association, 2008.

Michael Maxwell is vice president of engineering and technology and manager of applications for Griffin Filters LLC. He received a B.S. in Chemical Engineering from Iowa State University and an MBA from Lewis University. He has over 36 years of experience in dust collection design, application and installation, and has been a member of the National Fire Protection Association since 1994.