NFPA 660: A unified standard for better combustible dust risk management

Although most National Fire Protection Association (NFPA) standards have addressed combustible and explosive dust hazards for decades, NFPA 660 represents a major step forward in assessing and managing risks.

This document was developed by grouping all “industry-specific” NFPA standards into a unified and cohesive framework. These safety requirements were previously divided across the following standards:

• NFPA 61 for agricultural and food processing facilities

• NFPA 484 for the production, processing, finishing, handling, recycling, storage and use of all metals and alloys that pose a risk of combustion or deflagration.

• NFPA 654 for manufacturing, processing and handling combustible particulate solids.

• NFPA 655 for processing and handling sulfur in solid or molten form.

• NFPA 664 for wood processing and woodworking facilities

These standards are now obsolete. They are part of the plan to consolidate combustible dust documents, which was recently completed with the publication of the first edition of NFPA 660. Chapters 21 to 25 focus on specific industries and include requirements for each (e.g., Chapter 21 – Agricultural and Food Processing, Chapter 24 – Wood Processing and Woodworking).

It’s important to note that technical standards such as NFPA 68, NFPA 69 and NFPA 77 are not included in the consolidation plan and therefore remain independent and valid documents that must continue to be followed and applied.

In terms of analysis, the fundamental elements in identifying and assessing risks and hazards associated with combustible dusts are included and reinforced in NFPA 660. These elements were previously spread across various industry-specific standards and in NFPA 652 – Standard on the Fundamentals of Combustible Dust, which has served as the main reference since 2015. NFPA 660 now brings together the general definitions, key requirements and objectives, hazard identification and the risk analysis process, known as Dust Hazard Analysis (DHA), in the first 10 chapters (Fundamentals). The terminology has also been updated, with several technical definitions now standardized. These include definitions for ignitable fibres (non-deflagrable but still a potential fire hazard), combustible fibres (deflagrable), combustible dust (finely divided combustible solids presenting a deflagration risk) and combustible particulate solids (solid fragments likely to produce combustible dust).

It’s also worth noting that the concept of a management of change, or MOC, is now clearly defined as a system that “requires the evaluation of proposed changes to process materials, staffing, job tasks, technology, equipment, procedures, and facilities to evaluate the potential safety significance of the change, to identify any additional needed safety controls, and to identify changes to other management systems required to safely implement the change.” This type of analysis serves to:

• Assess the potential safety impact of the proposed change on processes and operations.

• Determine whether additional safety controls or safeguards are needed.

• Identify any changes in other existing management systems to implement the proposed change safely.

Together, these principles and definitions not only eliminate many of the disparities and inconsistencies found in now outdated standards, but also help resolve any remaining conflicts. This approach for managing such conflicts is based on the following rules (Section 1.6):

1. The principles set out in industry-specific chapters take precedence over those in the fundamentals (Chapters 1 to 10).
2. If an industry-specific chapter explicitly prohibits a fundamental requirement in Chapters 1 to 10, that prohibition must apply.
3. In the absence of specific requirements or prohibitions (or in the case of “Reserved” sections), the fundamental principles from Chapters 1 to 10 must apply.
4. An industry-specific chapter may be used to establish requirements not addressed in Chapters 1 to 10.

This unification makes it easier to understand and define the risks associated with combustible dust. It also offers a more consistent approach for achieving compliance in industrial facilities.

NFPA 660 is written and designed so regulatory authorities can adopt it as a code. This means that some Canadian provinces and territories may choose to adopt it directly or refer to it in their legislation.

In Québec, the only jurisdiction in North America (including Canada and the United States) to take this approach, industry-specific NFPA standards, such as NFPA 61, NFPA 484, NFPA 654 and NFPA 664, have been included in the wording of Section 58 and have been enforceable since the 2007 revision of the Regulation Respecting Occupational Health and Safety (CNESST, LRQ S-2.1, r. 13). Since the previous standards are now obsolete, it’s very likely that the authority will soon incorporate NFPA 660 into its regulations, particularly by updating Section 58.

In other Canadian provinces and territories, and in most U.S. states, unless new approaches are adopted, NFPA 660 will likely remain a recognized technical reference, without becoming a regulatory requirement. It will therefore be important to monitor how local occupational health and safety authorities develop their approaches (e.g., WorkSafeBC, Alberta Occupational Health and Safety, Ontario Ministry of Labour, Immigration, Training and Skills Development and the U.S. Occupational Safety and Health Administration).

The presence of dust accumulations is one of the main criteria evaluated by representatives of occupational health and safety authorities in North America (see next figure); It is important to remember that excessive accumulations of (fine) dust can lead to a second deflagration hazard (or second explosion hazard), an event with consequences that are most likely catastrophic.

One thing is certain: Companies must become familiar with NFPA 660 requirements and prepare to apply them, both for new projects and for existing facilities.

NFPA 660 introduces new requirements for more comprehensive analyses and stronger safety measures in industrial facilities. These include obligations to:

• Train personnel (initial and refresher training).

• Perform operational readiness review (ORR) before each restart.

• Upgrade the emergency response plan (ERP) to include a specific section on combustible dust.

• Clearly define self-heating hazards.

Owners of industrial facilities must develop and implement a training program that highlights potential exposure to hazards related to combustible dusts, combustible particulate solids and ignitable or combustible (deflagrable) fibres. This program must be provided to plant employees, contractors, temporary workers and visitors who may be exposed to combustible dust hazards or could trigger hazardous situations. In addition to general information and site- or process-specific details, the training must clearly describe workplace hazards, applicable emergency response plans (e.g., evacuation) and established safety rules. It must also provide an overview of how safety devices function when workers may be affected (e.g., deflagration vents, mechanical isolation valves, chemical suppression systems). Refresher training must be provided at least every three years.

Owners must also ensure an operational readiness review, or ORR, is conducted to ensure the safe startup of new systems or processes, or the safe restart of existing facilities that have been modified or temporarily or permanently shut down. This review verifies that all required controls and safety devices are in place and that all safety tasks and functions have been completed.

Owners must also ensure an ERP is drawn up and implemented to guide emergency response actions in the event of a fire, flash fire or combustible dust deflagration. This plan complements existing provincial and territorial occupational health and safety requirements (such as the RSST in Québec) and aligns with recommendations such as those in the CAN/CSA Z.731 standard – Emergency Preparedness and Response. According to Chapter 10 of NFPA 660, the emergency response plan must be reviewed and validated at least once a year and must include:

• Methods of communication and emergency telephone numbers

• Designated assembly areas.

• Names of those responsible for notifying emergency services (e.g., fire department) and those who meet off-site emergency responders to help coordinate the response

• Facility layout drawings, showing evacuation routes, locations of hazardous chemical storage areas and fire protection equipment

• Safety data sheets (SDSs) for chemicals or hazardous materials

• Clear roles and responsibilities for everyone involved in the emergency response

Facilities must develop and implement an ERP for all new sites, and this requirement also applies retroactively to existing operations.

As part of hazard identification, owners must pay special attention to the risk of self-heating in the presence of combustible particulate solids and combustible dust. This hazard can occur in silos and other storage equipment, as well as in areas of the process or equipment where materials may build up during normal or abnormal operating conditions (e.g., blocked chutes, plugged dust collection ducts). A self-heating hazard is considered likely and must be controlled if at least one of the following conditions applies:

• More than 1,000 kg of combustible particulate solids are stored or transported in bulk (refer to next figure)

• More than 10 kg of high-temperature material exits a dryer and is collected in a bin or hopper

• A self-heating scenario has been identified during the risk analysis

The BBA team provides unique, cutting-edge technical support in this area, including onsite sampling, laboratory testing, hazard confirmation, identification of possible control solutions and preparation of safety procedures. To find out more, read our technical article about self-heating (upcoming) and refer to the EN-15188:2020 standard.

Following the publication of the NFPA 660 standard, the owner of a North American plant in which combustible dusts are used, produced or generated must ensure that a DHA covering all its facilities is carried out in the short term, or that any analysis carried out in recent years is updated. The following actions should be part of the measures to be implemented:

1. Personnel training: Provide adequate and comprehensive training to plant personnel as well as contractors, temporary workers and visitors (risks associated with combustible dust); refresher training must be provided at least every three (3) years.
2. Operational readiness review (ORR): Ensure the safe start-up of new systems or the safe restart of existing facilities that have been modified or whose activity has been temporarily interrupted (e.g., annual plant shutdown).
3. Emergency planning and response plan: Identify and supervise the actions to be taken in the event of a fire, flash fire or combustible dust explosion, and integrate them into the existing plan; the emergency response plan must be reviewed and validated at least annually.
4. Self-heating hazard evaluation: Pay particular attention to the phenomenon of self-heating that may occur in the presence of combustible solid particles and combustible dusts (e.g., bulk storage, high-temperature equipment).
5. Management of change (MOC): Ensure the identification and control of the impact on risk management of any planned modification and in particular likely to affect the nature or properties of the materials present, human resources, the tasks performed by personnel, technology and process equipment, procedures or facilities.

NFPA 660 is a crucial, unified resource for companies and industrial facilities that produce or handle flammable or combustible fibres (deflagrable), combustible dust, or combustible particulate solids. This standard consolidates key definitions and methodologies for hazard and risk assessments (fundamental principles) and introduces new requirements, including a clear definition of a change management system, along with new evaluation requirements for risks related to self-heating, thermal instability, water reactivity and chemical reactivity of the materials involved. NFPA 660 also includes an informal and comprehensive appendix (Appendix Y) with laboratory test data showing the properties of various combustible dusts across industries.

Whether you need to update your risk analysis, perform a new one based on NFPA 660 standards, deliver comprehensive and relevant training to your teams, assess self-heating risks, or implement or update your procedures (e.g., ORR, ERP), BBA's team of experts has been there for you for over 25 years!

Are you unsure how the new standard could affect your operations? Do you have any questions or concerns? Contact our team of experts; we’re here to help you understand what changes you need to make.