Combustible Dust Hazard Analysis Under NFPA 652, 654, and 660
If a fire department inspector, your insurer, or a corporate safety team has asked for a “DHA,” they are asking for a combustible dust hazard analysis.
If a fire department inspector, your insurer, or a corporate safety team has asked for a “DHA,” they are asking for a combustible dust hazard analysis. It is a written study that evaluates each process where dust is generated, handled, or accumulates, identifies where that dust could ignite or deflagrate, and documents the safeguards that prevent it.
There is no single OSHA combustible-dust standard. Cal/OSHA enforces these hazards through the employer-duty requirement (Labor Code §6400(a)) and IIPP standard (8 CCR §3203), treating the NFPA family of standards as recognized industry practice. For most California facilities, that means NFPA 652, NFPA 654, and (as of December 2024) NFPA 660, which now consolidates both.
For the broader regulatory picture, including who needs a DHA in California and how the work gets triggered, see our dust hazard analysis in California guide.
What a Combustible Dust Hazard Analysis Actually Does
A combustible dust hazard analysis answers two questions at once. First, is your dust capable of deflagration? (Lab combustibility testing answers that one.) Second, do the conditions in your facility (how dust is generated, conveyed, collected, and cleaned) create the ignition and accumulation scenarios that could turn a deflagration into a fire, flash event, or secondary dust explosion?
The analysis walks each process: receiving, storage, conveying, milling or grinding, mixing, dust collection, bagging, cleanup. For each, the team documents the dust generated, the ignition sources present, the deflagration safeguards already in place, and any gaps against the applicable NFPA chapter.
A DHA is the written record. It is not a remediation project. It tells you what needs to change, against which standard, and in what order.
If your dust has not been confirmed combustible through lab testing, that step comes before the DHA. See combustible dust testing and sampling for what those lab determinations cover and when a go/no-go combustibility report is enough on its own.
Where NFPA 652 and 654 Stand Today
NFPA 652 was the “fundamentals” standard for combustible dust. It set the baseline DHA requirement, the five-year reanalysis cycle, and the framework for evaluating combustible dust hazards across industries. NFPA 654 was the industry-specific standard for manufacturing, processing, and handling of combustible particulate solids.
In late 2024, NFPA published NFPA 660: Standard for Combustible Dusts and Particulate Solids. NFPA 660 consolidates NFPA 652 and 654 (along with NFPA 61 for agriculture and food processing, 484 for combustible metals, 655 for sulfur, and 664 for wood processing) into one document. The fundamentals moved into the early chapters; the industry-specific requirements moved into commodity-specific chapters of the same standard.
NFPA 652 is no longer being updated. Inspectors, insurers, and corporate safety programs that previously cited 652 and 654 are migrating their references to NFPA 660.
What this means for a California facility: a DHA written to NFPA 652/654 is still a valid technical document, and the underlying requirements carried forward almost unchanged. New analyses and five-year revalidations should now reference NFPA 660 and the commodity chapter that applies to your operation.
What the DHA Process Looks Like
A typical CDMS DHA engagement runs in four phases:
Scoping call.
We review what processes are in scope, whether combustibility has been confirmed for your specific dusts, and whether any lab sampling needs to be added to the proposal as a separate line item.
Site walkthrough.
Our consultant walks each in-scope process, photographs dust accumulation points, reviews ignition source controls, and interviews operators about housekeeping practices and abnormal conditions.
Analysis.
Each process is evaluated against the relevant chapter of NFPA 660 (or the legacy NFPA 652/654 framework when the client requests it). Findings are organized by process, with safeguards documented and gaps flagged.
Report.
A written DHA report is delivered with findings, references to the applicable NFPA sections, recommended controls, and a revalidation schedule.
The deliverable ends at the report. We do not require an ongoing engagement or insist on implementing every recommendation as part of the same project. Many California facilities tell us their previous DHA vendors wanted to manage the program post-report; CDMS scopes the analysis narrowly to the report itself, and the client handles implementation with their own team or contractors.
California Enforcement Context
Cal/OSHA enforces combustible dust hazards primarily through the General Duty Clause (Labor Code §6400(a), which requires every employer to furnish a safe place of employment) and the Injury and Illness Prevention Program standard (8 CCR §3203). When an inspector finds dust accumulations on overhead surfaces, inside electrical enclosures, or near ignition sources, the citation typically pairs the General Duty Clause with NFPA standards as the recognized industry practice.
Your local CUPA (which may be a county environmental health department, fire department, or another local agency depending on jurisdiction) has its own interest in combustible dust. After a small fire, a near miss, or a routine inspection, fire department staff frequently ask for a DHA before signing off on subsequent work. This is the most common path California facilities arrive at our door: the inspector asked for it, the facility had not heard of NFPA 652/660 before, and there is a deadline.
When we walk a California food, metal, or woodworking facility, the deficiencies we find most often are not the obvious ones at floor level. It is dust on overhead pipe runs and cable trays, dust collectors located inside buildings without explosion isolation or venting to a safe location, and housekeeping schedules that look complete on paper but have not been verified in months.
The Five-Year Reanalysis Cycle
NFPA 652 introduced a five-year DHA reanalysis requirement, and NFPA 660 carries it forward. Every five years, and whenever a material, process, or equipment change happens, the analysis has to be reviewed and updated.
This is not a repeat of the original study. It is a structured technical review of whether the assumptions in the original DHA still match what is happening on the floor. If your facility added a new mill, switched dust suppliers, changed dust collection equipment, or modified housekeeping practices, the reanalysis captures those changes and updates the hazard scenarios.
If your last DHA was completed in 2020 or 2021, you are inside the reanalysis window now. If it was written to NFPA 652/654, the revalidation is the natural point to bring the references current to NFPA 660.
What the Report Includes
A CDMS combustible dust hazard analysis report covers:
- Each in-scope process with photos, dust descriptions, and lab data (where applicable)
- An ignition source survey (electrical, mechanical, hot work, static, friction)
- Deflagration safeguards in place and gaps against NFPA 660
- A housekeeping evaluation against the applicable commodity chapter
- Prioritized findings with referenced safeguards
- A revalidation schedule
The report is the deliverable. What you do with the findings is your decision. Facilities that need help implementing the recommended controls can re-engage; many handle implementation on their own with the report as their roadmap.
For a deeper look at the hazard-identification methods sometimes used in larger process-safety studies (HAZOP, What-If, and LOPA), see DHA methods: HAZOP, What-If, and LOPA. For most dust-focused DHAs in California, these methods are recognized but not required; NFPA 660’s documented review of each process is what an inspector or insurer expects to see.
Trusted throughout California
BSY started working with CDMS last year after our in-house EHS person departed the company. CDMS reviewed our existing operational permits as well as any additional Federal, State and Local regulations that could apply and helped us to create a comprehensive compliance calendar to track regulatory deadlines and submittal due dates. The CDMS team does an excellent job of tracking everything and can be relied upon to complete the forms accurately and assist with submittals, allowing me to focus on our business.
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