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NFPA 660 – Consolidated Combustible Dust Standards

“Maintaining effective housekeeping is a crucial and potent defense strategy against various workplace hazards, including the potential dangers associated with combustible dust. NFPA 660 not only advocates for cleaning techniques like vacuuming, but also establishes precise design criteria to guarantee that equipment is capable of handling the challenges posed by the collection of combustible dust. In the absence of a formal OSHA regulation, the guidance provided by NFPA 660 is indispensable for instructing our manufacturing clients on the identification, measurement, and, most importantly, the selection of the appropriate industrial vacuum to safely mitigate the risk associated with combustible dust.” Contact Nilfisk at 800-989-2235 or visit for more information.

Combustible dusts are fine particles that present an explosion hazard when suspended in air in certain conditions. Any combustible material can burn rapidly when in a finely divided form. If such a dust is suspended in air in the right concentration, under certain conditions, it can become explosible. Even materials that do not burn in larger pieces (such as aluminum or iron), given the proper conditions, can be explosible in dust form. Various types of food (e.g., candy, sugar, spice, starch, flour, feed), grain, tobacco, plastics, wood, paper, pulp, rubber, pesticides, pharmaceuticals, dyes, coal and metals (e.g., aluminum, chromium, iron, magnesium and zinc) can all be explosible in dust form.

The force from combustible dust explosions can cause employee deaths, injuries and damage – including the destruction of entire buildings. In many combustible dust incidents, employers and employees were unaware that a hazard even existed. Secondary explosions, which can occur when an initial explosion has dislodged more accumulated dust into the air, can be far more destructive than a primary explosion due to the increased quantity and concentration of dispersed combustible dust. Many deaths in past incidents, as well as other damage, have been caused by secondary explosions.

Combustible dust explosion hazards exist in a variety of industries, including: agriculture, chemicals, food (e.g., candy, sugar, spice, starch, flour, feed), grain, fertilizer, tobacco, plastics, wood, forestry, paper, pulp, rubber, furniture, textiles, pesticides, pharmaceuticals, tire and rubber manufacturing, dyes, coal, metal processing (e.g., aluminum, chromium, iron, magnesium, and zinc), recycling operations, fossil fuel power generation (coal), additive manufacturing and 3D printing.

A New Standard

The information and guidance contained in a number of existing combustible dust-related standards is being consolidated into one, all-encompassing new standard in a Combustible Dust Document Consolidation Plan that was approved by the National Fire Protection Agency (NFPA) Standards Council.  As part of the consolidation plan, NFPA 660 will combine the following standards:

  • NFPA 652: Standard on the Fundamentals of Combustible Dust
  • NFPA 484: Standard for Combustible Metals
  • NFPA 61: Standard for the Prevention of Fires and Dust Explosions in Agricultural and Food Processing Facilities, regarding Agriculture and Food
  • NFPA 654: Standard for the Prevention of Fire and Dust Explosions from the Manufacturing, Processing, and Handling of Combustible Particulate Solids
  • NFPA 655: Standard for Prevention of Sulfur Fires and Explosions
  • NFPA 664: Standard for the Prevention of Fires and Explosions in Wood Processing and Woodworking Facilities

Although a great deal of foundational information and guidance will remain the same, NFPA 660 will include some changes to definitions and clarifications made to accommodate commodity-specific hazards and processes.

Timeline of the Consolidation Process

  • The first draft had a public input closing date of January 5, 2023 and a first draft report posting date of October 25, 2023.
  • The second draft’s public comment closing date is January 4, 2024, with a report posting date of October 3, 2024.
  • The Motions Committee Report’s (NITMAM) closing date will be
    October 31, 2024. The NITMAM posting date is December 12, 2024.

Dust Explosion Prevention

Preventing combustible dust incidents begins with a thorough hazard assessment of material, operations, spaces and potential ignition sources. An inspection, housekeeping and control program should be implemented. Equipment such as dust collection systems and filters should be utilized, along with ventilation systems that minimize the escape of dust. Housekeeping must include regular cleaning of surfaces that accumulate dust, using cleaning methods that do not generate dust clouds, if ignition sources are present. Only vacuum cleaners approved for dust collection should be used.

Ignition control recommendations include the use of appropriate electrical equipment and wiring methods; and control of static electricity, smoking, open flames and sparks. Separator devices should be used to remove foreign materials capable of igniting combustibles from process materials. Heated surfaces and heating systems should be separated from dusts.

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