When Is a Dust Hazard Analysis Required — and What OSHA Actually Enforces

PSSI
Jan 20
3 min read

Many food, pharmaceutical, and chemical manufacturing facilities maintain excellent housekeeping programs. Floors are clean, overheads are inspected, and visible dust accumulation is minimal. Yet serious combustible dust incidents and dust safety management failures continue to occur in facilities that believed they were managing the risk appropriately.

The reason is rarely a lack of awareness or effort. Instead, it is often a gap between what facilities believe their Dust Hazard Analysis (DHA) covers and the hazards that actually exist inside equipment and process systems.

This article explains what NFPA 660 expects from a DHA, how OSHA evaluates those expectations through the Combustible Dust National Emphasis Program (NEP), and where hidden hazards commonly exist.

Dust Hazard Analysis Requirements Under NFPA 660

NFPA 660, Standard for Combustible Dusts and Particulate Solids, consolidates former combustible dust standards into a single authoritative document for all industries. Key DHA requirements include:

Performing a Dust Hazard Analysis for facilities handling combustible dust hazards.
Reviewing and updating the DHA at least every five years.
Updating the DHA whenever materials, equipment, or processes change.
Maintaining DHA documentation over the life of the facility.

While most facilities understand that a DHA is necessary, the real value lies in evaluating hazards that are less visible, particularly inside process equipment such as dryers, sifters, blenders, dust collectors, and ductwork.

OSHA Enforcement: NEP and the General Duty Clause

OSHA does not have a single comprehensive combustible dust standard for general industry. Enforcement occurs through multiple mechanisms:

The General Duty Clause (Section 5(a)(1) of the OSH Act), which requires employers to provide a workplace free from recognized hazards that could cause death or serious injury.
Applicable OSHA standards covering housekeeping, electrical safety, hazard communication, ventilation, and mechanical integrity.
The Combustible Dust National Emphasis Program (NEP), which directs inspectors to high-risk facilities and focuses attention on dust hazards in both visible areas and enclosed equipment.

Under the NEP, OSHA inspectors routinely use NFPA 660 as a recognized guideline and reference for safe practices, showing that combustible dust hazards are recognized in the industry and that feasible safeguards exist. Facilities with a DHA that addresses internal equipment hazards, credible ignition sources, and process-specific operating conditions are better positioned to demonstrate compliance under the General Duty Clause.

Hidden Dust Hazards: Beyond Housekeeping

Housekeeping is Necessary, But Not Sufficient

Housekeeping remains one of the most effective preventive measures for combustible dust. Many food, pharmaceutical, and chemical plants maintain very clean floors, overheads, and visible surfaces.

However, many explosions originate inside enclosed equipment, where housekeeping cannot reach. These include:

Internal accumulations in dryers, mills, blenders, sifters, and mixers
Residual dust after shutdowns, cleaning, or changeovers
Deposits inside dust collectors, cyclones, plenums, and ductwork

A DHA must consider whether dust hazards exist in these hidden areas, as they are often the origin of initial ignition events.

Enclosure and Dust Control

Enclosures reduce fugitive dust in the facility environment, but they do not eliminate combustible dust hazards inside equipment. NFPA 660 requires that internal dust and potential ignition sources be evaluated even in enclosed or partially enclosed processes.

Characteristics of a Defensible Dust Hazard Analysis

A defensible DHA under NFPA 660 is a structured evaluation that:

Identifies combustible dust hazards by process, equipment, and operating mode
Evaluates credible ignition sources both inside and outside equipment
Considers normal operations as well as startup, shutdown, cleaning, and maintenance conditions
Assesses potential fire and explosion consequences, including secondary events
Documents the technical basis for selected safeguards

Additionally, NFPA 660 requires that the DHA be:

Site-specific, not generic
Maintained and retained over the life of the facility
Reviewed every five years and updated whenever process, material, or equipment changes occur

Proper documentation ensures that hazards were thoughtfully identified and that the facility can demonstrate compliance under the NEP and General Duty Clause.

Why Addressing Dust Hazards Matters Now

Regulatory scrutiny of combustible dust hazards remains high. OSHA inspectors, guided by the NEP, focus on facilities where combustible dust can accumulate, especially inside equipment and process enclosures. Facilities that delay reviewing or updating their DHA often do so until after a near-miss or inspection, when options are more limited and consequences are more severe.

Moving Forward

If your Dust Hazard Analysis has not been reviewed with a focus on internal equipment hazards and realistic operating conditions, it may not reflect the risks that NFPA 660 intends to address. A properly conducted DHA supports regulatory compliance, reduces operational risk, and provides a defensible basis for safety decisions — particularly in facilities where hazards are not always visible.