NFPA 660: Standard for Combustible Dusts and Particulate Solids

January 8, 2025|Compliance, Respiratory, Safety

“Pneumatic vacuums play a critical role in maintaining compliance with combustible dust (condust) regulations. The HafcoVac uses compressed air instead of electrical components, eliminating potential ignition sources and aligning with safety standards set by organizations like OSHA and NFPA. By effectively capturing and containing dust utilizing HEPA Filtration, the HafcoVac prevents dust accumulation and dispersion, ensuring that facilities adhere to guidelines designed to minimize explosion and fire risks. This proactive approach not only protects workers and assets, but also helps companies avoid fines and legal repercussions associated with non-compliance.” HAVCOVAC, www.hafcovac.com

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.

Why Dust and Particulate Standards are Important

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.

The force from combustible dust explosions has caused employee deaths, injuries, and destruction of entire buildings. 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. According to CSB reports, 14 workers were killed in a 2008 sugar dust explosion in Georgia¹ and, three workers were killed in a 2010 titanium dust explosion in West Virginia.²

As a result of these catastrophic incidents, OSHA initiated a Combustible Dust National Emphasis Program in 2007, and revised the NEP in 2008 and 2023. The NEP establishes policies and procedures for inspections at facilities that generate or handle combustible dusts that are likely to cause fire, flash fire, deflagration, and/or explosion hazards.³

Which Industries Have Combustible Dust Explosion Hazards?

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), and additive manufacturing and 3D printing.

What is the Purpose of NFPA 660?

The information and guidance contained in a number of existing combustible dust-related standards was consolidated into one, all-encompassing new standard in a Combustible Dust Document Consolidation Plan that was approved by the NFPA Standards Council. As part of the consolidation plan, NFPA 660 combined 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 remained the same, NFPA 660 included some changes to definitions and clarifications made to accommodate commodity-specific hazards and processes.

Hazard Assessment and Control Program Implementation

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.