Combustible Dust Incident Under Investigation by US CSB

The US Chemical Safety Board (CSB) is investigating the fatal explosions and fire that occurred July 29 at a facility in Fremont, Nebraska. A father and his two daughters were inside the facility and were fatally injured.

The facility produced animal bedding and wood fuel pellets for heating from wood waste. The local fire marshal’s office said the incident was caused by an accidental dust fire.

Dust as a Workplace Safety Hazard

OSHA’s Hazard Communication (HazCom) Standard defines combustible dust as “finely divided solid particulates of a substance or mixture that pose a flash-fire hazard or explosion hazard when dispersed in air or other oxidizing media.” [29 CFR 1910.1200]

Under the same Standard, combustible dust is also explicitly included in the definition of hazardous chemical: “Hazardous chemical means any chemical which is classified as a physical hazard or a health hazard, a simple asphyxiant, combustible dust, or hazard not otherwise classified.”

Dusts known to cause these hazards include metal dust, wood dust, coal and other carbon dusts, plastic dust and additives, biosolids, organic dust (sugar, flour, soap, dried blood, etc.), and certain textile materials.

This video shows what happened during a 2008 combustible dust explosion that killed 14 people and injured 38 others.


 

The US CSB identified 281 combustible dust incidents between 1980 and 2005 that led to the deaths of 119 workers, injured 718, and extensively damaged numerous industrial facilities. OSHA, Combustible Dust: An Explosion Hazard

What OSHA Regulations Apply to Combustible Dust?

While there is no specific OSHA standard for combustible dust, the Agency relies on multiple workplace health & safety requirements, as well as the General Duty Clause of the OSH Act, to cite violations.

If dust is found accumulated on surfaces or in material storage areas, for example, OSHA may cite the employer for housekeeping violations under the general industry standards for Walking-Working Surfaces (§1910.22(a)(1)–(2)) or Materials Handling and Storage (§1910.176(c)).

OSHA may also cite an employer for noncompliance with workplace ventilation standards in §1910.94, personal protective equipment (PPE) requirements in §1910.132, or hazard communication information and training requirements in §1910.1200 for hazardous chemicals, among others.

Combustible Dust and the OSH Act General Duty Clause

The General Duty Clause of the OSH Act (Section 5(a)(1)) requires employers to provide a workplace for employees that is free of recognized hazards that can cause serious injury or illness. In its 2023 combustible dust directive for enforcement personnel, OSHA lists scenarios that could result in a citation for a violation of the General Duty Clause related to combustible dust. 

The following are examples of workplace conditions for which a general duty clause citation (see Appendix C for sample citations) may be issued:

• Problems related to dust collectors, e.g., dust collection equipment located inside the building (however, there are some exceptions) and dust collectors returning air back inside the building.

• Ductwork-related problems, e.g., the ductwork not being grounded and ductwork not constructed of metal.

• Improperly designed deflagration venting (venting to areas where employees are likely to be exposed to explosion/deflagration hazards).

• Processing and material handling equipment, such as mixers, blenders, pulverizers, mills, dryers, ovens, filters, dust collectors, pneumatic conveyors, and screw conveyors, that are not protected by deflagration suppression systems.

• Blowers, collection systems, and exhaust systems used at sawmills that are not designed, constructed, or maintained properly.

Tags: combustible dust, CSB, osha