This edition of NFPA 660 was approved as an American National Standard on December 6, 2024.
NFPA 660 was written by consolidating the requirements of NFPA 652, Standard on the Fundamentals of Combustible Dust; NFPA 61, Standard for the Prevention of Fires and Dust Explosions in Agricultural and Food Processing Facilities; NFPA 484, Standard for Combustible Metals; 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; and NFPA 654, Standard for the Prevention of Fire and Dust Explosions from the Manufacturing, Processing, and Handling of Combustible Particulate Solids, and making them into individual chapters in NFPA 660, so that this standard provides safety requirements for all combustible dusts and particulate solids.
One effect of this consolidation is that the definitions and terminology from each document have been standardized and are all found in Chapter 3, and fundamental requirements that apply to all of the industries or commodities covered by NFPA 660 are located in the first 10 chapters. Annex material in A.1.3 explains the organization of this combined document and how to determine the requirements for a piece of equipment, building, or facility.
The 2025 edition of NFPA 660 also includes some changes from the last editions of the source documents, including but not limited to the following:
Requirements from the industry- or commodity-specific standards that were deemed to be fundamental have been moved to the first 10 chapters.
Requirements that are covered in the fundamental chapters have been removed from the industry- and commodity-specific chapters.
Terminology for “deflagration vent/venting” was made consistent throughout.
Terminology for types of sulfur size reduction machinery was updated.
Terms such as transient releases, management of change, operational readiness review, and explosive- and propellant-actuated devices have been defined.
Requirements for operational readiness reviews have been added.
New requirements have been added to evaluate self heating, thermal instability, water reactivity, and chemical reactivity hazards.
Information has been added to document who is qualified to perform a DHA.
Text has been added throughout Chapter 8 and the annexes to address the level of protection provided by flame-resistant garments.
Elements of general safety training and job-specific training and frequency of refresher training have been specified.
Requirements for bonding and grounding of housekeeping equipment have been clarified.
Resistance limits for flexible connectors have been updated.
References to risk assessments and DHAs have been edited for consistency throughout.
Industrial hygiene exposure limits have been referenced for recycling of AMS exhaust to buildings.
Changes in Chapter 21 clarify what kind of flexible connectors can be used in agricultural and food processing facilities.
DHA requirements for existing processes and facility compartments in agricultural and food processing facilities have been revised.
Guidance on responding to silo fires has been added.
Test standards for portable vacuum cleaners used with combustible metals have been provided.
Additive manufacturing requirements in Chapter 22 were updated.
Changes in Chapters 23 and 25 clarify when manifolding of dust collection ducts is permitted.
Guidance for spark detection systems has been updated.
An annex has been added to assist in calculating the thermal dose to personnel from flash fires and building compartment deflagrations.
The technical committees would like to recognize two long-standing technical committee members, Erdem Ural and Robert Zalosh, who were instrumental in the development of several NFPA standards and passed away during the final stages of development of NFPA 660. Each having served more than 25 years on NFPA committees, they both had an incredible impact on the explosion protection and combustible dust industry, and their presence is deeply missed.
Finally, this edition of NFPA 660 is dedicated to workers who have suffered injuries or lost their lives from the hazards of combustible dusts, in the hope that it will help prevent such tragedies in the future.
CLICK HERE to purchase this new NFPA standard