On October 24, the US Chemical Safety and Hazard Investigation Board (which uses the truncated acronym CSB) issued a “Call to Action: Combustible Dust” seeking information about what it has long considered a major industrial hazard. Since 1980 CSB has identified hundreds of industrial accidents involving dust that have injured nearly 1000 workers and killed more than one hundred. In 2006 CSB issued 4 formal recommendations to the Occupational Safety and Health Administration (OSHA) to enhance that agency’s regulation of occupational hazards from combustible dust – particularly from possible fires or explosions, with mixed responses.
What are Combustible Dusts and Their Hazards?
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What is Combustible Dust?
OSHA guidance presents the basic proposition that combustible dusts are any that will burn in air, and notes the National Fire Protection Association’s (NFPA’s) more formal definition of “Any finely divided solid material that is 420 microns or smaller in diameter (material passing a U.S. No. 40 Standard Sieve) and presents a fire or explosion hazard when dispersed and ignited in air.” Many materials can qualify:
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Organic materials – coal, sawdust, grain, flour, starch, sugar, powdered milk, cocoa, coffee, and pollen
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Inorganic materials - metal dust, such as aluminum and magnesium.
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Where Might Hazardous Accumulations Occur?
Hazardous accumulations can occur in storage of larger volume particles of the same materials (grain dust in grain silos have been identified in many explosions), or when lax housekeeping allows dusts to accumulate near work areas or in ducts.
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What Events Can Produce Fires and Explosions?
A suitable ignition source in an area with combustible dust can lead to catastrophic fires and explosions. These include fires, sparks, and even overheated machinery. Incidents have occurred in working areas where an incident that might have stayed small was exacerbated when dusts caught fire or exploded. They have also occurred in relatively isolated storage areas and ventilation ducts where the dusts were the primary hazard.
What do OSHA and State OSH Agencies Require?
OSHA recognizes that combustible dusts create workplace hazards, but has not issued separate standards for their management (OSHA issued an advance notice of proposed rulemaking in 2009 but has taken no significant action on that proposal since 2011). OSHA does offer guidance, including a Safety and Health Information Bulletin that borrows from NFPA Standard 654 and provides:
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Background Information – about the hazard, and types of locations.
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Facility Dust Hazard Assessment – which should consider:
- Materials that can be combustible when finely divided.
- Processes which use, consume, or produce combustible dusts.
- Open areas where combustible dusts may build up.
- Hidden areas where combustible dusts may accumulate.
- Means by which dust may be dispersed in the air.
- Potential ignition sources.
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Dust Control:
- Minimize escape of dust from process equipment or ventilation systems
- Use dust collection systems and filters
- Utilize surfaces that minimize dust accumulation and facilitate cleaning
- Provide access to all hidden areas to permit inspection
- Inspect regularly for dust residues in open and hidden areas
- Clean dust residues regularly
- Use cleaning methods that do not generate dust clouds, if ignition sources are present
- Use vacuum cleaners approved for dust collection
- Locate relief valves away from dust hazard areas
- Develop and implement a hazardous dust inspection, testing, housekeeping, and control program (preferably in writing with established frequency and methods)
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Ignition Control:
- Use appropriate electrical equipment and wiring methods
- Control static electricity, including bonding of equipment to ground
- Control smoking, open flames, and sparks
- Control mechanical sparks and friction
- Use separator devices to remove foreign materials capable of igniting combustibles from process materials
- Separate heated surfaces from dusts
- Separate heating systems from dusts
- Proper use and type of industrial trucks
- Proper use of cartridge activated tools
- Adequately maintain all the above equipment.
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Damage Control
What More is CSB Seeking?
As I noted above, CSB sent OSHA four recommendations in 2006. One was that OSHA issue a combustible dust standard, which hasn’t happened. OSHA did respond to other recommendations, by identifying combustible dust as a physical hazard category in its Hazard Communication Standard (HCS; done as part of major revisions in 2012) and communicating with the United Nations’ Globally Harmonized System (GHS; the basis for the 2012 HCS revisions), by offering training on combustible dust hazards and management, and by providing a Special Emphasis Program that targets enforcement efforts.
CSB’s new Call to Action is framed as a significant information gathering effort “to gather insights and feedback from those most directly involved with combustible dust hazards.” The document asks the following specific questions:-
In real-world working conditions, where dust is an inherent aspect of the operation, can a workplace be both dusty and safe?
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In such working environments — where the amount of ambient/fugitive dust cannot be wholly eliminated 100 percent of the time — how does an individual or organization distinguish between an acceptable or safe dust level and one that has been exceeded? How often does judgment or experience play a role in such decisions? Should it?
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How are hazards associated with combustible dust communicated and taught to workers? What systems have organizations successfully used to help their employees recognize and address dust hazards?
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What are some of the challenges you face when implementing industry guidance or standards pertaining to dust control/management?
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If companies/facilities need to use separate or different approaches in order to comply with both sanitation standards for product quality or food safety and those associated with dust explosion prevention, then how do you determine what takes priority? Is the guidance clear?
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How should the effectiveness of housekeeping be measured? What methods work best (e.g., cleaning methods, staffing, schedules)?
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As equipment is used and ages, it requires mechanical integrity to maintain safe and efficient operability. How does inspection, maintenance, and overall mechanical integrity efforts play a role in dust accumulations, and how are organizations minimizing such contributions in the workplace?
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What are some of the challenges to maintaining effective dust collection systems?
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How common are dust fires in the workplace that do not result in an explosion? Does this create a false sense of security?
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Are workers empowered to report issues when they feel something needs to change with regard to dust accumulation? What processes are in place to make these concerns known?
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How can combustible dust operators, industry standard organizations, and regulators better share information to prevent future incidents?
The CSB will review all responses submitted by November 26, 2018, and use the information provided to explore the conditions that influence the control and management of combustible dust.
Self-Assessment Checklist
Has the organization surveyed its operations to determine if any might lead to the accumulation of dusts?If so, has the organization evaluated those dust accumulations to determine if any are combustible dusts?
Have any of the organization’s operations suffered a fire or explosion involving combustible dust?
Has the organization established workplace housekeeping, hygiene or other programs to prevent hazardous accumulations of combustible dusts?
Has the organization implemented those programs, including self-inspections and periodic reviews to assess their accomplishments?
Where Can I Go For More Information?
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OSHA’s Combustible Dust – An Explosion Hazards safety and health topic portal
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CSB’s Release/Link for Combustible Dust Call to Action
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NFPA Codes and Standards (see NFPA 652 (Standard on the Fundamentals of Combustible Dust), NFPA 654 (Standard for the Prevention of Fire and Dust Explosions from the Manufacturing, Processing, and Handling of Combustible Particulate Solids)
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CalOSHA’s Combustible Dust standard
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About the Author
Jon Elliott is President of Touchstone Environmental and has been a major contributor to STP’s product range for over 25 years. He was involved in developing Environmental Compliance: A Simplified National Guide and The Complete Guide to Environmental Law.
Mr. Elliott has a diverse educational background. In addition to his Juris Doctor (University of California, Boalt Hall School of Law, 1981), he holds a Master of Public Policy (Goldman School of Public Policy [GSPP], UC Berkeley, 1980), and a Bachelor of Science in Mechanical Engineering (Princeton University, 1977).
Mr. Elliott is active in professional and community organizations. In addition, he is a past chairman of the Board of Directors of the GSPP Alumni Association, and past member of the Executive Committee of the State Bar of California's Environmental Law Section (including past chair of its Legislative Committee).
You may contact Mr. Elliott directly at: tei@ix.netcom.com