Combustible Dust Summarized

 What is Combustible Dust?

Essentially, a combustible dust is any fine material that has the ability to catch fire and explode when mixed with air. Combustible dusts can be from:

  • most solid organic materials (such as sugar, flour, grain, wood, etc. )
  • many metals, and
  • some nonmetallic inorganic materials.

Some of these materials are not "normally" combustible, but they can burn or explode if the particles are the right size and in the right concentration.

Therefore any activity that creates dust should be investigated to see if there is a risk of that dust being combustible. Dust can collect on surfaces such as rafters, roofs, suspended ceilings, ducts, crevices, dust collectors, and other equipment. When the dust is disturbed and under certain circumstances, there is the potential for a serious explosion to occur. The build-up of even a very small amount of dust can cause serious damage.


Combustible Dust Illustration

What workplaces are at risk for a dust explosion?

Dust explosions have occurred in many different types of workplaces and industries, including:

  • Grain elevators
  • Food production
  • Chemical manufacturing (e.g. , rubber, plastics, pharmaceuticals)
  • Woodworking facilities
  • Metal processing (e.g. , zinc, magnesium, aluminum, iron)
  • Recycling facilities (e.g. , paper, plastics, metals), and
  • Coal-fired power plants.

Dusts are created when materials are transported, handled, processed, polished, ground and shaped. Dusts are also created by abrasive blasting, cutting, crushing, mixing, sifting or screening dry materials. The buildup of dried residue from the processing of wet materials can also generate dusts. Essentially, any workplace that generates dust is potentially at risk.

What you need to know right now (USA):

  • NFPA Standards are not law, but are used by OSHA as a guideline to determine safety hazards. The NFPA warns that more than 1/32 of an inch of dust over 5 percent of a room's surface area presents a significant explosion hazard.
  • Failure to comply can result in fines, but MOST importantly cause severe worker safety hazards
  • Combustible Dust is listed on OSHA's Active National & Special Emphasis Program Index - This means that OSHA has increased its enforcement activities for combustible dust. OSHA is aggressively targeting any facility that manufactures, processes, blends, conveys, repackages and/or handles combustible dust.
  • NFPA 652 applies to ALL facilities and operations that manufacture, process, blend, convey, repackage, generate, or handle combustible dusts or combustible dust particulate {not just classified (hazardous) locations}.
  • Dust Test Required: The absence of previous incidents cannot be used as the basis for deeming a particulate not combustible. Owner/operator is responsible, test results must be documented and provided to the AHJ (Authority Having Jurisdiction) upon request
  • Dust Hazard Analysis Required and completed by September 2018. Must show reasonable progress each year.
  • Vacuums are recommended as best way to mitigate combustible dust
  • Requires Class II Div. 2 Vacuums to manage spills and bulk materials

What you need to know right now (Canada)

  • Although there is currently no combustible dust hazard class under WHMIS, suppliers are required to declare all hazards of the product on MSDSs, as a condition of sale and importation.

Understanding Governing Bodies (USA)

    • OSHA- Stands for Occupational Safety and Health Administration-This is an agency of the United States Department of Labor whose mission is to prevent workplace deaths, injuries and illnesses.
    • NFPA- Stands for National Fire Protection Association- This is a global nonprofit organization devoted to eliminating death, injury, property and economic loss due to fire, electrical and related hazards.
    • NFIRS- Stands for National Fire Incident Reporting System- This is an online reporting system managed by the Department of Homeland Security Federal Emergency Management Agency and U.S. Fire Administration
    • NFIC- National Fire Information Council- This is an agency committed to enhancing public safety through the collection and dissemination of timely, accurate, and useable fire-related emergency response information
    • UL- Global independent safety science company offering expertise across three strategic businesses: Commercial & Industrial, Consumer and UL Ventures.
    • NRTL- Nationally Recognized Testing Laboratory Program- While many of the requirements for ATEX certification overlap with NFPA vacuum design requirements often relied upon during an OSHA inspection, the ATEX directive isn’t relevant in the United States. Instead, OSHA requires equipment to be certified by a NRTL. It must be noted that NRTL certifications and marks are issued based upon testing done to electrical codes and standards. There are currently no standards and no NRTL certifications specific to pneumatic vacuum equipment.

Understanding Governing Bodies (Canada)

  • CCOHS-Stands for Canadian Centre for Occupational Health and Safety- This is an agency of the Government of Canada whose vision is the elimination of work-related illnesses and injuries.
  • WHMIS- Stands for Workplace Hazardous Materials Information System- This is Canada's national hazard communication standard. The key elements of the system are hazard classification, cautionary labelling of containers, the provision of (material) safety data sheets (MSDSs) and worker education and training programs.
  • Alberta Occupational Health and Safety (OHS)- Works in consultation with industry to help prevent work-related injuries, illnesses and fatalities.
  • British Columbia- WorkSafeBC- The Occupational Health and Safety Regulation (OHSR)- The purpose is to promote occupational health and safety and to protect workers and other persons present at workplaces from work-related risks to their health, safety, and well-being.
  • Manitoba Labour Board- An independent and autonomous specialist tribunal responsible for the fair and efficient administration and adjudication of responsibilities assigned to it under all the various Acts including The Workplace Safety and Health Act.
  • New Brunswick-WorkSafeNB- New Brunswick law protects employers' and workers' rights under four pieces of legislation and their regulations: the Workplace Health, Safety and Compensation Commission and Workers' Compensation Appeals Tribunal Act, the Workers' Compensation Act, the Occupational Health and Safety Act, and the Firefighters' Compensation Act. WorkSafeNB is responsible for administering all four.
  • Newfoundland Labrador Occupational Health and Safety- The primary goal of the Occupational Health and Safety Division is accident and illness prevention.
  • Northwest Territories & Nunavut- WSCC- Workers' Safety and Compensation Commission of the Northwest Territories and Nunavut
  • Nova Scotia Occupational Health and Safety Division- The Occupational Health & Safety Division (OH&S) concentrates its efforts on safe and healthy workplaces, and work practices, and safety standards protecting the general public. The Division seeks to continuously improve the provision of its services.
  • Ontario Ministry of Labour- Enforces the Occupational Health and Safety Act.
  • Prince Edward Island- Workers Compensation Board (WCB) is responsible for administering workplace safety legislation on Prince Edward Island. This legislation is the Occupational Health and Safety (OHS) Act.
  • Quebec- CNESST- Committee on Standards, Equity, Health and Safety at Work- The CNESST is the body to which the Quebec government has entrusted the promotion of the rights and obligations of work. It ensures respect for workers and employers in Quebec.
  • Government of Saskatchewan- Labour Relations and Workplace Safety- The Ministry of Labour Relations and Workplace Safety (LRWS) encourages healthy, safe and productive workplaces by setting, promoting and enforcing employment and occupational health and safety standards.
  • Yukon Territory- Yukon Workers' Compensation Health and Safety Board- The Yukon Workers’ Compensation Health and Safety Board is funded solely by Yukon employers. Our job is preventing disability. We do that by providing compensation, service and support to Yukon workers injured on the job. We also promote workplace safety through training, inspection and compliance and investigations.
Understanding Codes & Standards
Understanding Certifications & Directives
  • ATEX Directive- Stands for atmospheres explosibles. It's a European Union directive from the European Committee for Standardization that covers "equipment and protective systems intended for use in potentially explosive atmospheres."
  • IECEx System- One of the IEC’s Conformity Assessment Systems. The IECEx Certified Equipment Scheme is a vast international arrangement established by the International Electrotechnical Commission (IEC) for mutual acceptance of test reports among participating certification organizations in the field of equipment for use in locations with potentially explosive atmospheres (Hazardous Locations). In addition to the evaluation of the equipment design, the Scheme also involves surveillance activities which are based on the requirements that the manufacturer’s quality system have to fulfill.
Understanding Dust Classifications
  • Class II Div 2-Class II locations are those that are hazardous because of the presence of combustible dust. Note that the dust must be present in sufficient quantities for a fire or explosion hazard to exist. The fact that there is some combustible dust present does not mean a Class II hazardous location exists. To be considered a “dust”, the combustible material must exist as a finely divided solid of 420 microns (0.420 mm) or less. Such a dust will pass through a No. 40 sieve. Just as in Class I, Division 1 and 2, the subdivision of Class II into Divisions 1 and 2 identifies the likelihood that there will be an explosion hazard.
  • Division 1 A Class II, Division 1 location exists where combustible dust is normally in suspension in the air in sufficient quantities to produce ignitable materials, or where mechanical failure or abnormal operation of equipment might cause an explosion or ignitable dust-air mixture to be produced, or where combustible dusts of an electrically conductive nature may be present in hazardous quantities (Group E). (Note – the term “hazardous quantities” is intended to mean those locations where the dust may not be in suspension in the air in sufficient quantity to cause an explosion, but might have settled on electrical equipment so that the electrically conductive particles can penetrate the openings in the equipment and cause an electrical failure.)
  • Division 2 -A Class II, Division location exists where combustible dust is not normally in the air in sufficient quantity to produce an explosion, and dust accumulations are not normally sufficient to interfere with the normal operation of electrical equipment. It includes locations where combustible dust may be in suspension in the air only as a result of infrequent malfunctioning of handling or processing equipment, and those locations where dust accumulation may be on or in the vicinity of the electrical equipment and may be sufficient to interfere with the safe dissipation of heat from the equipment, or may be ignitable by abnormal operation or failure of the electrical equipment.
  • Groups. Division into three groups in Class II locations is for the same reasons Class I locations are divided into Groups A, B, C and D: equipment design and area classification. However the three Class II groups (Groups E, F & G) are based on different characteristics than the four Class I groups because the design characteristics are different. In Class II locations, the ignition temperature of the dust, the electrical conductivity of the dust, and the thermal blanketing effect the dust can have on heat-producing equipment such as lighting fixtures and motors are the deciding factors in determining the Class II groups.

    Group E dusts include the metal dusts, such as aluminum and magnesium. In addition to being highly abrasive, and thus likely to cause overheating of motor bearings if the dust gets into the bearing. Group E dusts are electrically conductive and if they are allowed to enter an enclosure, they can cause electrical failure of the equipment

    Group F dusts are carbonaceous, the primary dust in this group being coal dust. (*also coal dust and carbon black). These dusts have somewhat lower ignition temperatures than the Group E dusts and a layer of Group F dust has a higher thermal insulating value than the layer of Group E dust, thus requiring a more careful control of the temperature on the surface of the material. Such dusts are semi-conductive but this is not usually a factor for equipment rated 600 volts and less.

    Group G dusts include plastic dusts, most chemical dusts and food and grain dusts. They are not electrically conductive. These dusts, in general, have the highest thermal insulating characteristics and the lowest ignition temperatures. Thus dust-ignition proof equipment for use in Group G atmospheres must have the lowest surface temperatures to prevent ignition of a layer by the heat generated by the equipment.

Combustible Dust Groups

Types of Dust

Types of Dust OSHA Poster

Understanding Dust Analysis

  • Documented dust tests are REQUIRED.
  • Dust Hazard Analysis (DHA) are REQUIRED. This is a systematic review to identify and evaluate the potential fire, flash fire, or explosion hazards associated with the presence of one or more combustible particulate solids in a process or facility. The review documents must be kept on file to document safe handling of combustible dust.
  • Dust Hazard Analysis (DHA) must be completed by September 2018 (3 years from effective date of standard) for existing facilities.
  • Vacuum equipment must meet certain design requirements, even if you're not in a classified (hazardous) area.
  • NFPA 652 applies to all facilities and operations that manufacture, process, blend, convey, repackage, generate, or handle combustible dusts or combustible particulate solid. Not just classified (hazardous) locations.
  • NFPA 652 says that a dust test is required. The absence of previous incidents cannot be used as the basis for deeming a particulate not combustible (section 5.2)
  • Owner/operator of a facility is responsible for determining the combustibility of material
  • Test results, historical and published data must be kept on file at all times

Understanding the Risks

  • Combustible dust fires happen every day. People are injured and killed.
  • OSHA can cite and fine you if you're violating NFPA standards for combustible dust
  • Effective August 1, 2016 OSHA increased its maximum penalties for the first time since 1990 and they continue to raise fines annually to keep pace with inflation
  • OSHA can cite employers under the General Duty Clause (GDC) when workers are exposed to hazards not currently addressed in OSHA Standards.
    • There must be a hazard
    • The hazard must be recognized
    • The hazard causes or is likely to cause serious harm or death; and
    • The hazard must be correctable
  • OSHA can fine a facility for selecting inappropriate equipment to clean combustible dust.

Understanding the Statistics

  • The U.S. Chemical Safety and Hazard Investigation Board (CSB) identified 281 combustible dust incidents between 1980 and 2005 that led to the deaths of 119 workers, injured 718 and extensively damaged numerous industrial facilities
  • In just one year 2011 there were more than 500 combustible dust fires and explosions reported to the NFIRS
  • 20% of all OSHA fines fall within the "Housekeeping" section and is the third most frequently cited violations during inspections. Consists of 18 different standards that can be used to cite against.

How to Prevent OSHA Fines

  • Understand the top violations, assess your workplace and re-evaluate your safety program
  • Hazard Recognition Training can be a great baseline to ensure workers have basic safety training topics covered
  • Obtain certifications on topics and hazards that are especially risky for your workers


OSHA Penalties 2017

How to Clean Combustible Dust from High Spaces

Please see SkyVac A37 G