to NFPA 660 Standard for Combustible Dust – Dust Hazard Analysis

Jess McCluer
Jess McCluer

This article is written by Jess McCluer, vice president of safety and regulatory affairs with the National Grain and Feed Association (NGFA), as a follow-up to a presentation on dust hazard analysis (DHA) and the consolidation of the National Fire Protection Association’s (NFPA) combustible dust standards.

The presentation – from CONVEY‘23 in late July – was given by Tim Meyer, Exponent, who serves as chair of the NFPA Technical Committee on Agricultural Dusts.

To view a recording of Meyer’s presentation, go to

For well over the past two years, NFPA has been working through the intricate process of making major changes to its current combustible dust standards. The purpose has been to clarify and consolidate multiple standards into a single, all-encompassing standard, which is designated as NFPA 660 Standard for Combustible Dusts. NFPA has its origins in the 1920s with some of the United States’ first combustible dust standards addressing sugar, cocoa, and flour for feed mills and terminal grain elevators.

NGFA and other industry groups are concerned about the potential for federal regulators to adopt this new standard.

Background on NFPA Standards 

The new NFPA 660 will consolidate the following NFPA standards:

• NFPA 61 – Standard for the Prevention of Fires and Dust Explosions in Agricultural and Food Processing Facilities (2020 latest version).

• NFPA 91 – Standard for Exhaust Systems for Air Conveying of Vapors, Gases, Mists, and Particulate Solids (2020).

• NFPA 484 – Standard for Combustible Metals (2022).

• NFPA 652 – Standard on the Fundamentals of Combustible Dust (2019).

• NFPA 654 – Standard for the Prevention of Fire and Dust Explosions from the Manufacturing, Processing, and Handling of Combustible Particulate Solids (2020).

• NFPA 655 – Standard for the Prevention of Sulfur Fires and Explosion (2017).

• NFPA 664 – Standard for the Prevention of Fires and Explosions in Wood Processing and Woodworking Facilities (2020).

Representatives from several organizations in the grain, feed, and processing industries serve on the NFPA 61 committee, including NGFA, the American Feed Industry Association (AFIA), the Grain Elevator and Processing Society (GEAPS), the National Oilseed and Processing Association (NOPA), the North American Millers’ Association (NAMA), the U.S. Beet Sugar Association (USBA), and the U.S. Poultry and Egg Association (USPEA).

The Occupational Safety and Health Administration (OSHA) can cite a facility under the General Duty clause for a variety of things, including excessive dust concentrations. But the NFPA standards, at least with regard to combustible dust, currently are voluntary, and compliance is not required under the OSHA Grain Handling Standard (29 CFR 1910.272).

Since the 1988 standard was implemented, NGFA has worked with OSHA officials to clarify compliance requirements and convey this information to the industry.

Instead, NFPA standards only apply to facilities if local authorities have adopted the standards within their jurisdiction (e.g., fire marshals or building code inspectors may adopt the standards and rely on them for enforcement purposes).

The NFPA standards specifically focus on mitigation and prevention and management systems. While OSHA has not formally adopted them, many insurance companies have adopted them as part of their policies to mitigate risks.

However, many believe that the primary reason NFPA 660 is being prepared is to make it easier for OSHA to adopt a single such standard – through direct adoption or incorporation by reference – since OSHA does not have any plans to publish its own combustible dust standard in the near future. NGFA, AFIA, GEAPS, NOPA, NAMA, USBA, and USPEA are particularly concerned about this prospect.

One problem is that the drafters of such so-called “voluntary” standards do not calculate their economic burdens, which is a requirement when drafting OSHA standards. Another danger is that OSHA might treat NFPA 660 as replacing the Grain Handling Standard.

At this time, NFPA 660 has not yet been finally adopted. The entire consolidation process will likely not be completed until sometime in 2024, which would make NFPA 660 a 2025 publication. In the meantime, the existing NFPA committees, as described above, will continue to meet to cover their chapters’ inclusion in the new standard.

NFPA 660 has 10 general chapters, followed by industry- or commodity-specific chapters for agricultural dusts, combustible metals, combustible solids, sulfur, and wood dust. The current configuration of the new standard (subject to modifications) will be as follows:

• Chapters 1-9 will cover the fundamentals of combustible dust.

• Chapters 10-14 will cover what are currently commodity-specific standards. However, these chapters will not include the requirements covered in Chapters 1 through 9, only the information necessary to cover any conflicts between the fundamentals and commodity-specific requirements.

The remaining chapters are subject to revision but will include:

• Appendix information for the fundamental chapters and individual commodity-specific chapters. How this will be logistically covered has not been determined.

• Additional appendix information to provide users with extensive data on typical explosivity characteristics of various materials, examples of DHAs, and other topics to assist the reader in understanding combustible dust compliance requirements.

Burdensome Requirements

The requirements for DHA and management-of-change (MOC) procedures that originated in the chemical industry are of primary concern to the grain, feed, and processing industries.

Both the DHA and MOC are very burdensome (for example, they will require company capital to purchase new equipment) and yet have no justifiable application to the agricultural sector. The standard is also 881 pages long.

The DHA requirement in NFPA 660 was modeled after the process hazard analysis requirement that OSHA imposed on the chemical industry. It would require that every owner of a facility with combustible dust write a “systematic” evaluation of every scenario in which a dust ignition could occur and how it will be prevented. The requirement is not justified in the agricultural sector.

The chemical industry often uses novel chemicals, and has varied and complex chemical processes, the behavior of which can often be difficult to predict. By contrast, the ignition behavior of agricultural dusts and their handling equipment and processes are not complex, have long been known, and have remained essentially unchanged for centuries.

The DHA provision in NFPA 660 will impose onerous costs in equipment and employee time. Many small entities will be forced to hire expensive consultants to review processes that already are well understood.

The chemical industry’s experience indicates that the DHA requirement will be an enforcement nightmare. When an injury occurs, OSHA asks for a copy of the analysis.

If the analysis did not anticipate the accident, a citation is issued for an incomplete analysis – no matter how conscientiously it was prepared. If the analysis did anticipate the accident, a “willful” citation and massive penalty are issued for not preventing it.

Some might think that the language permitting the use of a “checklist” form in the annex will relieve users of the burden of the provision. It will not. The annex form – containing 12 pages of fine print – essentially regurgitates every requirement of the DHA provisions.

Some might rely on the statement in NFPA 660’s annex that: “It is not the intent of this standard to require users to apply the Process Hazard Analysis provisions of OSHA regulations in 29 CFR 1910.119, ‘Process Safety Management of Highly Hazardous Chemicals,’ in developing a [DHA].” The statement is illusory.

NFPA 660’s dust hazard analysis provisions are just as onerous as the process hazard analysis provisions in OSHA’s standard. The MOC requirements in NFPA 660 were modeled after one OSHA imposed on the chemical industry that would require every owner of a facility with combustible dust to conduct a formal evaluation of every single change (other than a replacement in kind) to the facility or its equipment. Every change, no matter how minor, must be evaluated. OSHA has even taken the position that staffing and budget changes must undergo an MOC if it would affect the safety of the process. Unions have taken advantage of this to prevent downsizing of workforces in chemical plants. The requirement is not justified in the agricultural sector. Again, the reasons for it pertain only to the chemical industry, which can have such complex and novel chemicals and processes that the slightest change might unpredictably cause a catastrophic accident.

• The NFPA 660 draft is too long and complex to be usable by ordinary people who will be expected to comply. It is not only 881 pages long, but much of the material is irrelevant to those in the agricultural sector and those using wood dust, sulfur dust, and combustible metallic dusts.

Today, the specialized user can purchase only the short standard applicable to their industry or dust. But if NFPA 660 is adopted, then every user would be required to purchase the 881-page-long publication, which NGFA and the other organizations consider economically burdensome.

The first draft of NFPA 660 was made available to the public for review and comment. The NFPA 61 committee met in February to review and provide feedback on the proposed changes to the standards. The revised draft will be available for public comment this fall so the committee once again can review the proposed changes and make their final recommendations when they meet again in early 2024.