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Combustible Dusts
Who Has a Combustible Dust Problem?
Many employers are unaware of a potential explosive dust hazard in their workplace. By identifying and controlling dust explosion hazards, injuries, deaths, and costly damage can be prevented. Some of the industries that could have a combustible dust hazard include:
- Agriculture
- Chemical
- Forest and furniture products
- Metal processing (e.g. aluminum, magnesium, zinc)
- Organic dust producers or users (e.g. working with fine dusts of candy, dried blood, paper, pulp, soap, spices, starch, sugar, flour, and feed)
- Paper products manufacturers
- Pharmaceuticals
- Plastics
- Producers or users of coal or other carbon dusts
- Recycling operations (e.g. metal, paper, and plastic recycling operations)
- Tire and rubber
- Textile
- Wastewater treatment (Biosolids)
- Wood dust producers
What Makes Combustible Dust an Explosion Hazard?
Combustible dusts become an explosion hazard when they are suspended in the air in the proper concentration in a confined or semi-confined vessel, area, or building.1 With the oxygen present in the air, all that is needed is an ignition source for an explosion to occur.
Many variables can affect the explosibility of a dust. To fully assess the risk of a dust explosion, it may be necessary to have the materials involved tested by a specialized lab.
Primary and Secondary Dust Explosions
An initial or primary dust explosion can lead to one or more secondary dust explosions within a facility. This can occur when the initial dust explosion in the processing equipment or vessel ruptures the enclosure and ignites settled dust in a nearby area. Such explosions have destroyed buildings, killed 119 workers and injured 718 workers since 1980.2 In many of these cases, the employers involved were unaware of the hazard.
OSHA National Emphasis Program
The Occupational Safety and Health Administration (OSHA) issued a directive (CPL 03-00-008) effective March 11, 2008 initiating a Combustible Dust National Emphasis Program (NEP). This program requires OSHA offices to specifically target businesses with dust explosion hazards.
Catastrophic Fires Have Occurred With the Following Kinds of Dusts
- Coal dust
- Nylon fiber
- Phenolic Resin dust
- Plastic (polyethylene) dust
- Resin for fiberglass
- Rubber dust
The National Fire Protection Association (NFPA) states, "Any industrial process that reduces a combustible material and some normally noncombustible materials to a finely divided state presents a potential for a serious fire or explosion."
Conduct a Hazard Analysis
You may have to seek professional help with the following:
- Recognize that you may have a combustible dust hazard.
- Look for processes that use, consume, or produce fine dusts.
- Look for accumulations of fine dust, including in hidden areas (such as inside ductwork or over suspended ceilings).
- Look for ways dusts can become dispersed in the air.
- Look for ignition sources.
- Consider dust collectors, hoppers, and other equipment that can confine a dust cloud.
- Investigate the thermal stability of stored products.
Control - The Main Control Methods
- Prevent dust accumulations.
- Install special electrical equipment in areas with potential for explosive concentrations of combustible dust (Class II locations).
- Select and use industrial trucks properly.
- Implement proper procedures for the maintenance of ovens and process equipment.
- Select and install equipment safety devices.
- Install explosion relief venting devices.
- Design buildings, equipment, and ventilation systems properly (including bonding and grounding).
Safety Management
- Investigate fires and incidents.
- Train employees on Hazard Communication (including combustible dust hazards).
- Implement Process Safety Management.
National Fire Protection Association (NFPA) Standards
Since neither OSHA nor Cal/OSHA has an integrated mandatory standard that covers combustible dust, employers must rely on the various NFPA standards for guidance which can be accessed at www.nfpa.org
Cal/OSHA Standards Regarding Combustible Dust
The following Cal/OSHA standards may apply: Electrical Safety Orders, Group 1, Low-Voltage Electrical Safety Orders, Article 59. Hazardous (Classified) Locations, T8 §3220, T8 §3221, T8 §3650, T8 §4324, T8 §5143, T8 §5151, T8 §5152, T8 §5153, T8 §5157, T8 §5174, T8 §5175, T8 §5178, T8 §5189, T8 §5194, T8 §5450 and T8 §5460.
Additional Information
1 Illustration from Oregon OSHA Combustible Dust Hazard Alert www.orosha.org
2 According to a 2006 Chemical Safety and Hazard Investigation Board study
The above evaluations and/or recommendations are for general guidance only and should not be relied
upon for legal compliance purposes. They are based solely on the information provided to us and relate
only to those conditions specifically discussed. We do not make any warranty, expressed or implied, that your workplace is safe or healthful or that it complies with all laws, regulations or standards.
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