The National Fire Protection Association (NFPA) deadline for completing a dust hazard analysis is September 7, 2020. The analysis must be repeated every five years. This is in conjunction with the Combustible Dust National Emphasis Program that was initiated after the Imperial Sugar dust explosion which occurred on February 7, 2008.

National Emphasis Program

There is no OSHA standard for combustible dust but OSHA will be use NFPA 654 in conjunction with the OSHA’s General Duty Clause (GDC) for enforcement. OSHA includes the wholesale recycling industry (NAICS 42393) to be one of the targeted industries in the National Emphasis Program and has conducted 58 comprehensive site inspections at scrap yards between January 1, 2013 and today. The overall compliance rate for those 58 facilities was 16.7%.

The Combustible Dust National Emphasis Program (NEP) began on March 11, 2008 and has been renewed and is still in effect. This means OSHA will focus more of its energy and resources on education and enforcement of standards related to combustible dust. The focus of the NEP is to give instruction to enforcement officers regarding inspection site selection, inspection procedures, and citation guidance. During the emergency phase of the pandemic, all programmed inspections, including Dust NEP inspections are on hold.

A copy of the NEP can be found online.

Where is the Risk?

NFPA guidelines and the OSHA NEP state that a dust layer 1/32 inch thick (about the thickness of a dime) spread over just 5% of the floor area of a facility is sufficient to pose a combustible dust hazard. Dust that settles on rafters and piping above the floor can account for as much as 10% of the floor area of a building. Cleaning these overhead and relatively inaccessible areas can be difficult and even dangerous. Instead of removing accumulations of combustible dust, preventing the escape of fugitive dust from process equipment is the safest, most effective method of reducing the risk of a combustible dust explosion.

According to Jeff Wanko, the EPA subject matter expert on combustible dust who recently spoke at ISRI’s ISEC meeting in June, explosion events have occurred in a wide range of industries and involved many types of combustible dusts, 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).
• Coal-fired power plants.

Mr. Wanko also stated:

• Dust hazards exist where size reduction occurs.
• Hazards exist inside equipment.
• Dust collectors.
• Ductwork
• Hammer mills, grinders, etc...
• Hazards exist outside of equipment.
• Accumulations from product loss or fugitive emissions.

Dust Events

Combustible dust is a particulate solid, 420 - 500 µm or smaller, that presents a fire or deflagration hazard when suspended in air or oxidizing atmosphere over a range of concentrations, regardless of particle morphology. Approximately 80% of dust events are fires and dust explosions are considered low likelihood/high consequence events with many of the worst events occurring in industries that were not considered at high risk to dust explosions.

In addition to the three parts of the traditional fire triangle (oxygen, heat, & fuel) a dust event also requires confinement and dispersion. A common occurrence in a dust explosion is the presence of a secondary explosion. The first explosion creates the dispersion necessary for a greater, and more catastrophic, secondary explosion. 

Example: https://www.youtube.com/watch?v=3d37Ca3E4fA&t=300s

Questions Enforcement Officers Are Likely to Ask

The following questions come from NEP Appendix B as instructions to enforcement officers

• What types of combustible dust does the facility have?
• Does the facility have a housekeeping program with regular cleaning frequencies established for floors and horizontal surfaces, such as ducts, pipes, hoods, ledges, and beams, to minimize dust accumulations within operating areas of the facility?
• Under the housekeeping program, is the dust on floors, structural members, and other surfaces removed concurrently with operations?
• Is there dust accumulation of 1/32 inch thick, or greater?
• For housekeeping violations, what are the dimensions of the room and the dimensions of the area covered with the dust?
• Are the dust-containing systems (ducts and dust collectors) designed in a manner that fugitive dusts are not allowed to accumulate in the work area?
• Are dust collectors greater than 8 cubic feet in volume located inside of buildings?
• If dust explosion hazards exist in rooms, buildings, or other enclosures, do such areas have explosion relief venting distributed over the exterior walls of buildings and enclosures?
• Is such venting directed to a safe location away from employees?
• Does the facility have isolation devices to prevent deflagration propagation between pieces of equipment connected by ductwork?
• Does the facility have an ignition control program, such as grounding and bonding and other methods, for dissipating any electrostatic charge that could be generated while transporting the dust through the ductwork?
• Does the facility have separator devices to remove foreign materials capable of igniting combustible dusts?
• Are electrically- powered cleaning devices, such as sweepers or vacuum cleaners used in dusty areas, approved for the hazard classification, as required under 1910.307(b)?
• Is smoking permitted only in safe designated areas?
• Are areas where smoking is prohibited posted with “No Smoking” signs?
• Is the exhaust from the dust collectors recycled?
• Does the dust collector system have spark detection and explosion/deflagration suppression systems? (There are other alternative measures.)
• Are all components of the dust collection system constructed of noncombustible materials?
• Are ducts designed to maintain sufficient velocity to ensure the transport of both coarse and fine particles?
• Are duct systems, dust collectors, and dust-producing machinery bonded and grounded to minimize accumulation of static electrical charge?
• Is metal ductwork used?
• In areas where a hazardous quantity of dust accumulates or is present in suspension in the air, does all electrical wiring and equipment comply with 1910.307(b) requirements?
• Does the facility allow hot work only in safe, designated areas?
• Are bulk storage containers constructed of noncombustible materials?
• Does the company use methods to dissipate static electricity, such as by bonding and grounding?
• Are employees who are involved in operating, maintaining, and supervising facilities that handle combustible dust trained in the hazards of the combustible dust?
• Are {MSDSs/SDSs} for the chemicals which could become combustible dust under normal operations available to employees?

Staff Recommendations

• Assess your facility for the presence of combustible dust.
• Conduct a dust hazard analysis if combustible dust is present in quantities sufficient to support an explosion hazard.
• Work through the same questions that an OSHA enforcement official will likely ask (see above)

Additional information:

• NFPA 61: Standard for Agricultural and Food Processing Facilities
• NFPA 484: Standard for Combustible Metals
• NFPA 652: Standard on the Fundamentals of Combustible Dust
• NFPA 654: Standard for Combustible Particulate Solids
• NFPA 655: Standard for Sulfur
• NFPA 664: Standard for Wood Processing and Wood Working
• Jeff Wanko presentation to ISEC June 30, 2020