Major changes ahead for NFPA combustible dust standards

For well over a year, the National Fire Protection Agency (NFPA) has been proceeding with the intricate process of making major changes to the current combustible dust standards. The purpose is to clarify and consolidate the combustible dust standards into a single, all-encompassing standard, which is currently being designated as NFPA 660 (though that designation could change). No title has been formally determined for the new standard.

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 latest version)
• NFPA 484 Standard for Combustible Metals (2022 latest version)
• NFPA 652 Standard on the Fundamentals of Combustible Dust (2019 latest version)
• NFPA 654 Standard for the Prevention of Fire and Dust Explosions from the Manufacturing, Processing, and Handling of Combustible Particulate Solids (2020 latest version)
• NFPA 655 Standard for the Prevention of Sulfur Fires and Explosion (2017 latest version)
• NFPA 664 Standard for the Prevention of Fires and Explosions in Wood Processing and Woodworking Facilities (2020 latest version).

There is some debate whether NFPA 91 and 655 should be included or left as separate standards since they cover specific topics or commodities. At this time NFPA 91 will likely be left as a standalone standard since it covers both non-combustible and combustible items. The future of NFPA 655 has not been clarified, but it is likely to be included in the new NFPA 660 consolidated standard.

It is important to understand the difference between the current NFPA 652, which is considered the fundamentals standard, and NFPA 61, 484, 654, 655 and 664, which are considered commodity-specific standards for combustible dusts.

Status and configuration of the new standard

The first draft of NFPA 660 has been developed, and upon approval by NFPA’s Standards Council, it will be made available to the public for review and comment. If your company handles combustible dusts, it is imperative that you review the draft to see how the standard will apply to your facility. If you do not agree with any part of the first draft, the time to initiate a change is during the public comment period. (Be sure to follow the process correctly.) There are no guarantees that a change will be made, but all public comments are reviewed multiple times. This first draft will likely be available in 2022.

However, this concerns only the main body (Chapters 1 through 9) of the new standard, which covers the fundamentals of combustible dust. Each of the commodity-specific standards committees will be required to review their current standard and resolve any conflicts with Chapters 1 through 9. When this process is completed, these chapters (10 through 14) will be included in the first draft to allow for public comment.

The new NFPA 660 standard will be a sizable document, as it combines all the previous documents with all their pertinent information. However, it allows users to have all the required information on combustible dust compliance in one document rather than having to purchase multiple documents to determine how to comply with combustible dust standards. For example, if your company processes foods and you need information on combustible dust compliance for pneumatic conveying, centralized vacuum cleaning and dust collection, currently you must refer to NFPA 61, 654 and 652 to make sure you cover all pertinent requirements. NFPA 660 will have all that information in one standard.

The current configuration of the new standard (subject to modifications) will be as follows:

• Chapters 1 through 9 will cover the fundamentals of combustible dust.
• Chapters 10 through 14 will cover what are currently the 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:

1. The appendix information for the fundamentals chapters and individual commodity-specific chapters. How this will be logistically covered has not been determined.
2. Additional appendix information to provide users with extensive data on typical explosivity characteristics of various materials, examples of dust hazards analyses (DHAs) and other topics to assist the reader in understanding the combustible dust compliance requirements.

Projected changes

The following sections describe the significant changes made to the combustible dust standards during the process of consolidating the existing standards into the new NFPA 660 standard. Please note that this information is subject to modification.

A. Chapters 1 through 9 will contain the fundamentals of combustible dust. These fundamental requirements will in most cases be similar to what is already in NFPA 652. However, there will be some significant differences, which will range from clarification of wording to revision to elimination as follows.

Chapter 1 Administration. No significant changes were made other than to inform users that this document covers all the fundamental and commodity-specific requirements for combustible dust compliance.

Chapter 2 Reference Publications. No significant changes were made. This chapter will include all the referenced materials in the NFPA 660 standard.

Chapter 3 Definitions. Significant changes are required to include all the definitions pertinent to the fundamentals and the commodity-specific chapters. Some additional new definitions will also be included. 

Chapter 4 General Requirements. Some relatively minor changes were made, primarily to improve wording and clarify meaning.

Chapter 5 Hazard Identification. This chapter covers material testing and identifying the hazards associated with the tested materials. Changes center on clarifying how to determine what type of sample is needed and how it should be taken for representative testing results, the use of historical data and general understanding of the requirements.

Chapter 6 Performance-Based Design Option. The purpose of this section is to provide a method for users to properly evaluate and control combustible dust hazards that do not fit within a reasonable use of prescriptive methods. Some changes were made to clarify requirements for users.

Chapter 7 Dust Hazards Analysis (DHA). For existing facilities, a DHA should already have been completed, as the 5-year time period will have expired for all commodity-specific facilities. This chapter makes it clear that all existing and new facilities and processes that handle combustible dusts must have a completed DHA. Additional clarifications and information were provided for this chapter.

Chapter 8 Management Systems. This chapter covers hazard mitigating methods, including management-of-change, emergency procedures, housekeeping and hot work, that do not require prescriptive solutions (such as those covered in Chapter 9). Some changes were made, but these were mostly for clarification or to apply the requirement in a more “fundamental” way.

Chapter 9 Hazard Management: Mitigation and Prevention. This chapter was changed significantly due mainly to the recognition that some of the requirements are highly influenced by differences in the hazards associated with various commodity-specific processes — for example, metals versus food versus wood. Changes include:

1. Risk assessment is now applicable to all the requirements covered in Chapter 9.

2. Building construction requirements were not significantly changed, but the wording was improved for clarification.

3. Significant changes were made in the chapter’s equipment design portion:

        a.        No significant changes were made in the requirements for pneumatic conveying, centralized vacuum cleaning or dust collection systems.

        b.       The portable vacuum cleaning equipment sections were clarified.

        c.        Many equipment items, such as bucket elevators, feeders, screw conveyors and drag conveyors, were referred to the commodity-specific chapters due to the differences in use of these items for various commodities.

        d.       Other equipment items, such as mixers and dryers, do have some fundamental requirements, but most are referred to the commodity-specific chapters.

4. Wording improvements and clarifications were provided for the remaining portion of the chapter.

5. The 8-cubic-foot exemption was retained but with significant disagreement among committee members.

B. Chapters 10 through 14 are the commodity-specific chapters, which are expected to be revised as follows.

Chapter 10 (NPFA 61). Expect some significant resolving of conflicts on DHAs, equipment design and some items specifically included in the current NFPA 61 such as the ingredient transfer system exemption.

Chapter 11 (NFPA 484). Revisions to NFPA 484 will be the most difficult of all the commodity-specific chapter revisions due to the extreme range of hazards associated with various metals — legacy metals such as titanium compared to iron or carbon steel, for example. There will be multiple conflicts with the fundamentals chapters due to this wide range of hazards and to ensure that users fully understand the significance.

Chapter 12 (NFPA 654). Minimal changes and conflicts are expected. This will likely be the least changed chapter.

Chapter 13 (NFPA 655 — Sulfur). Minimal changes are expected.

Chapter 14 (NFPA 664). There will be some conflicts that need resolution, but changes will likely be minimal from the existing standard.

C. For the remainder of the new standard, the difficulty will be in coordinating the various appendix items. It is likely that this portion of the standard will not be significantly changed until NFPA 660 is published and going through its second cycle. Effort is being concentrated on the requirements and not the appendix items, which are only recommended and not required.

Timeline for completion

The entire consolidation process will likely not be completed until sometime in 2023, which would make NFPA 660 a 2024 publication. In the meantime, the existing NFPA committees will continue to meet to cover their chapters.

Once the NFPA 660 standard is published, it is also likely to become a code, much like NFPA 70 became the National Electric Code. Since OSHA has no current plans to establish their own combustible dust requirements, NPFA 660 will be the sole source on combustible dust compliance.

Jack Osborn ([email protected]) is a senior project engineer at Airdusco Engineering and Design Services (Airdusco EDS) and a member of Processing’s editorial advisory board. He has over 46 years of experience in dust collection systems, pneumatic conveying, centralized vacuum cleaning and various bulk handling and processing systems, and is a participating member of all six NFPA combustible dust committees.