February 6, 2025
NFPA 660: Standard for Combustible Dusts and Particulate Solids - What You Need To Know
There’s a new combustible dust standard in town!
NFPA 660: Standard for Combustible Dusts and Particulate Solids has officially been released, with an effective date of December 6, 2024. This represents a long-anticipated effort to streamline combustible dust safety standards and make it easier for companies to understand and meet the requirements. This article provides an overview of NFPA 660 and what you need to do to make sure you’re in compliance.
Why do we need a combustible dust standard?
Combustible dust poses a serious risk because seemingly harmless particles, when dispersed in air at the right concentration, can ignite and cause explosions. These dusts are present in a wide range of industrial processing facilities, from wood processing to food manufacturing, and the explosions they cause can be devastating, levelling buildings and killing workers.
The good news is that these explosions are 100% preventable through proper dust control. Combustible dust standards detail exactly what companies need to do to avoid catastrophic incidents.
Learn more in our ebook: Stay Safe From Combustible Dust and Worst-Case Scenarios
What is NFPA 660?
NFPA 660 is a new comprehensive standard issued by the National Fire Protection Association. Previously, there were six different standards addressing combustible dust hazards: NFPA 652, which outlined the fundamentals, and five industry- and commodity-specific standards:
- NFPA 61: Standard for the Prevention of Fires and Dust Explosions in Agricultural and Feed Processing Facilities
- NFPA 484: Standard for Combustible Metals
- NFPA 652: Standard Fundamental of Combustible Dust
- NFPA 654: Standard for the Prevention of Fire and Dust Explosions from 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
NFPA 660 consolidates all of these into one, streamlining the terminology and resolving conflicts between the fundamentals standard and the industry- and commodity-specific ones. It doesn't make major changes to the compliance requirements. Rather, it clarifies them to make it easier for companies in all industries to keep their workers and their facilities safe.
What are the general requirements for handling combustible dust?
NFPA 660, like the standards it replaces, lays out processes and best practices for mitigating combustible dust hazards. On a high level, these requirements encompass four main steps:
- Determine the combustibility and explosibility hazards of materials in your facility – This requires having your dust tested or using representative historical or published data, if applicable.
- Identify and assess fire and explosion hazards – Companies must conduct a Dust Hazards Analysis (DHA) for all new and existing processes and facility compartments. The DHA must be reviewed and updated at least every 5 years.
- Manage the identified hazards – Once you’ve identified your dust hazards, you must take steps to manage them. This includes implementing preventive measures and engineering controls as well as a housekeeping program to minimize dust accumulation.
- Communicate the hazards to affected personnel – Provide training and education to all workers involved in handling, processes, or managing combustible materials. In addition, develop an emergency response plan to prepare for and respond to fires and explosions caused by combustible dust.
What’s different between NFPA 660 and the previous standards it consolidates?
While NFPA 660 doesn’t make any major changes, there are some minor updates – especially to the commodity-specific standards – that you may need to be aware of, depending on your industry. Here are a few of them:
- Information has been added concerning who is qualified to perform a DHA.
- DHA requirements have been revised for agricultural and food processing facilities.
- Information about safety training has been specified.
- Requirements for bonding and grounding of housekeeping equipment have been clarified.
- Test standards for portable vacuum cleaners used with combustible metals have been provided.
Please note that this list is not comprehensive – refer to the full standard and your safety experts for complete information.
How can you ensure you’re in compliance?
If you have a robust combustible dust mitigation program in place – meaning one that complied with the previous NFPA standards – you’re already in a good position. Review NFPA 660, focusing on any updates relevant to your industry or commodity, and then keep up the good work!
If you don’t yet have a program in place, there’s no time to waste. OSHA, along with other regulatory agencies, frequently uses NFPA combustible dust standards during their inspections, usually by citing the General Duty Clause, which holds employers responsible for keeping workers safe “from recognized hazards that are causing or are likely to cause death or serious physical harm.” Combustible dust is a recognized hazard that, if not properly controlled, can become likely to cause death or serious physical harm.
How to mitigate combustible dust hazards through housekeeping
Your housekeeping plan is one of the most powerful tools you have for controlling combustible dust. As long as this dust isn’t allowed to accumulate, it won’t become a fire or explosion risk.
Housekeeping requirements
NFPA 660 lays out general housekeeping requirements to keep dust from accumulating above the critical threshold (this threshold differs depending on the industry or commodity being processed – refer to Chapters 21-24 for details).
- Facilities must have a documented housekeeping and inspection program in place, with established frequency and accumulation goals.
- The cleaning methods you select must be based on the characteristics and quality of the material present, and they must reduce the potential for creating a combustible dust cloud.
- Vacuuming is the preferred cleaning method. Only where vacuuming isn’t feasible are alternate methods, such as sweeping and water washdown, permitted.
Industrial combustible dust vacuums
NFPA 660 clarifies the requirements for the vacuums used to collect potentially combustible dusts and particulates.
- Vacuums used in a hazardous (classified) location MUST be listed for that environment.
- Vacuums used to collect combustible materials in unclassified locations must also conform to certain design requirements.
Key design requirements for industrial combustible dust vacuums:
- Construction materials must be conductive.
- Hoses and vacuum tools must be static dissipative or conductive.
- All static dissipative or conductive components (including wands and attachments) must be bounded and grounded.
- Fans or blowers are on the clean side of the primary filtration media or wet separation chamber; electrical motors are also on the clean side unless listed for Class II or Class III Division 1 locations
- Paper filters are not allowed when picking up liquids or wet materials.
While NFPA 660 represents a significant step forward in simplifying combustible dust standards, its success ultimately depends on proper implementation at the facility level. Now is the time to review your current dust management programs, update your procedures, and ensure your equipment meets the new requirements. Remember that combustible dust incidents are entirely preventable with proper controls and consistent housekeeping. By understanding and implementing the requirements outlined in NFPA 660, you're not just achieving compliance – you're creating a safer workplace for everyone.
Nilfisk’s industrial vacuums are built to meet or exceed all regulatory requirements for collecting combustible dust. Contact us to explore your options for compliant housekeeping equipment.