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OSHA term · Glossary

Combustible Dust

Fine particles of a solid material that can catch fire and, when suspended in air at the right concentration, explode (deflagrate). Many everyday materials become combustible dust in finely divided form — wood, flour, sugar, grain, coal, plastics, and metals like aluminum and magnesium. OSHA has no single comprehensive combustible dust standard; it addresses the hazard through the General Duty Clause, the Hazard Communication Standard, and specific standards, alongside NFPA consensus standards.

Also known as: explosible dust, deflagrable dust

Combustible Dust at a glance

  • Five elements for a dust explosion (the “dust explosion pentagon”): fuel (dust), oxygen, ignition source, dispersion (suspension in air), and confinement.
  • Common materials: wood, flour, sugar, grain, coal, paper, plastics, and metals (aluminum, magnesium, iron, zinc).
  • No single comprehensive OSHA standard — covered via the General Duty Clause, HCS (labels/SDS for the dust hazard), and standards like housekeeping (1910.22) and grain handling (1910.272).
  • Secondary explosions — dust shaken loose by an initial blast — are what make dust events catastrophic.

In plain English

Ordinary materials — flour, sawdust, sugar, metal powder — that become explosive when ground into fine dust and thrown into the air. A small first flash can shake more dust loose and trigger a much bigger secondary explosion.

What the source says, in summary

Any combustible material can burn rapidly when in a finely divided form. If such a dust is suspended in air in the right concentration, under certain conditions, it can become explosible.
OSHA — Combustible DustSummarized, not quoted: read the source for its operative wording.

In context

An enforcement, recordkeeping, or general-duty concept under the Occupational Safety and Health Act and 29 CFR. These terms define how OSHA inspects, cites, and penalizes employers.

29 CFR Chapter XVII

Example

In a sugar refinery, accumulated dust on rafters is disturbed and suspended by an initial flash; confined inside the building, it ignites in a devastating secondary explosion. The 2008 Imperial Sugar disaster followed exactly this pattern — a small primary event lofting layered dust into a far larger blast.

Why it matters

Combustible dust explosions are among the deadliest industrial events, and they hinge on housekeeping most facilities underestimate — a thin layer of accumulated dust is enough fuel. Because there's no one OSHA dust standard, employers must piece together the General Duty Clause, HCS, and NFPA standards, which makes dust hazards a frequent (and serious) enforcement gap.

Why “clean” facilities still explode

The danger isn't the dust cloud you can see — it's the thin layer settled on beams, ledges, and equipment. A minor primary deflagration disturbs that settled dust, suspends it, and sets off a secondary explosion far larger than the first. That's why housekeeping (removing accumulation) is the core control, not just ventilation.

The dust explosion pentagon (all five required)

ElementRole
FuelCombustible dust in finely divided form
OxygenOxidizer in the surrounding air
IgnitionSpark, flame, hot surface, static
DispersionDust suspended in a cloud at the right concentration
ConfinementEnclosure that lets pressure build

Combustible Dust: frequently asked questions

What is combustible dust?
Fine solid particles that can burn and, when suspended in air at the right concentration, explode. Everyday materials — wood, flour, sugar, grain, coal, plastics, and certain metals — become combustible dust in finely divided form.
What conditions are needed for a dust explosion?
Five, known as the dust explosion pentagon: fuel (the dust), oxygen, an ignition source, dispersion (dust suspended in air), and confinement. Remove any one and a deflagration can't develop into an explosion.
Is there an OSHA combustible dust standard?
There is no single comprehensive standard. OSHA addresses combustible dust through the General Duty Clause, the Hazard Communication Standard, and specific standards (like housekeeping and grain handling), supported by NFPA consensus standards.

Related terms

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Governing OSHA standards

More OSHA terms

Abatement

The action an employer takes to fix a cited violation or eliminate a hazard OSHA identified during an inspection. The citation sets an abatement date, the deadline to correct the hazard, and within 10 calendar days after that date the employer must certify to OSHA that the violation was abated. Failure to abate accrues additional penalties of up to $16,550 per day.

Area Director

The senior OSHA official in charge of a specific OSHA Area Office — the local unit that runs inspections and enforcement in its geographic territory. The Area Director has the authority to issue citations, propose penalties, hold informal conferences with employers, and approve settlement agreements. When a Compliance Safety and Health Officer (CSHO) completes an inspection, it's the Area Director who ultimately issues the citation.

Bureau of Labor Statistics (BLS)

The federal statistical agency within the U.S. Department of Labor that collects, analyzes, and publishes data on workplace injuries, illnesses, and fatalities. BLS conducts the annual Survey of Occupational Injuries and Illnesses (SOII) — compiled from employer OSHA 300 logs — and the Census of Fatal Occupational Injuries (CFOI). SOII data drives OSHA's Site-Specific Targeting (SST) program: establishments whose DART rates significantly exceed their BLS industry average are placed on the SST inspection list.

Competent Person

Under OSHA's construction standards, a person who is capable of identifying existing and predictable hazards in the surroundings or working conditions, and who has the authorization to take prompt corrective measures to eliminate them. The role requires both knowledge and the authority to act, and is mandated by name in many specific standards — excavations, scaffolds, fall protection, asbestos, and more.

Citation

The formal written notice OSHA issues to an employer after an inspection, describing each alleged violation, the standard cited, the proposed penalty, and the date by which the hazard must be corrected (abated). OSHA must issue a citation with reasonable promptness and no later than six months after the violation occurred.

Closing Conference

The meeting at the end of an OSHA inspection where the compliance officer confers with the employer and informally advises them of any apparent violations found. Importantly, the closing conference discusses what was observed and the employer's rights — but it does NOT state final citations or penalties, which come later in the written Citation and Notification of Penalty.

Compliance Officer (CSHO)

An OSHA Compliance Safety and Health Officer — the inspector who conducts workplace inspections. A CSHO presents credentials (a photo ID and a serial number), holds the opening conference, performs the walkaround, collects evidence, interviews employees, and recommends citations. CSHOs are either safety specialists or industrial hygienists.

Contest

An employer's formal challenge to an OSHA citation, penalty, or abatement date. To contest, the employer must file a written Notice of Contest with the OSHA Area Director within 15 working days of receiving the Citation and Notification of Penalty. Filing sends the case to the independent Occupational Safety and Health Review Commission (OSHRC); missing the deadline makes the citation a final, un-appealable order.

Sources & verification

Reviewed by HazComFast against eCFR, OSHA.gov, NIOSH, and the Federal Register. Last reviewed 2026-10-05. This glossary is general information, not legal advice; OSHA State-Plan states (e.g. California, Michigan) may adopt stricter requirements.

Put Combustible Dust into practice

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