Combustible Dust & Reactive Chemical Hazards

Combustible dust: a widespread, under-recognized hazard

Many materials that seem harmless in bulk — sugar, flour, grain, wood, plastics, pharmaceuticals, metals and many chemicals — can burn rapidly or explode when finely divided and dispersed in air. The U.S. Chemical Safety and Hazard Investigation Board has investigated numerous fatal dust incidents, many involving a secondary explosion: a small primary event lofts accumulated dust from ledges and beams, which then ignites and propagates through the building.

OSHA does not have a single comprehensive combustible dust standard, but it addresses dust hazards through the General Duty Clause, housekeeping and hazard communication requirements, and industry-specific standards such as grain handling. NFPA standards set the detailed expectations.

The dust explosion pentagon

A dust explosion requires five elements: combustible fuel (dust), an oxidant (usually air), an ignition source, dispersion of the dust in a cloud and confinement. Prevention and protection strategies work by removing or controlling one or more of these elements — for example housekeeping and dust collection, inerting, ignition source control, or explosion venting, suppression and isolation.

Dust hazard analysis (DHA)

NFPA standards require a dust hazard analysis for processes that handle combustible particulate solids. A DHA systematically examines each process system and building compartment to:

1. Determine combustibility and explosibility

   Using test data or justified assumptions for each material.

2. Identify fire, flash fire and explosion hazards

   Inside equipment such as dust collectors, silos, dryers, mills and conveyors, and in building areas with dust accumulation.

3. Evaluate existing safeguards

   Venting, suppression, isolation, inerting, ignition control, housekeeping and electrical area classification.

4. Recommend improvements

   Prioritized, practical recommendations, and the information needed to engineer them.

Understanding test data

Decisions about dust and reactive hazards depend on material-specific laboratory data. We help clients decide which tests are needed, interpret results and apply them in design:

Aetso Technical provides engineering assessment and interpretation. Laboratory testing is performed by qualified third-party laboratories; we can help define the test program and coordinate with the laboratory of your choice.

Reactive chemical hazards

Uncontrolled chemical reactions — runaway exotherms, decomposition, polymerization and reactions between incompatible materials — have caused many serious incidents. Many reactive hazards are not explicitly covered by the chemical lists in PSM and RMP, so they are easy to miss.

We support reactive hazard management in line with CCPS guidance, including:

• Screening materials and processes for reactivity hazards
• Chemical compatibility matrices for storage, handling and cleaning
• Evaluation of thermal stability data and time-to-maximum-rate considerations
• Identification of credible upset scenarios such as loss of cooling, mischarging and contamination
• Input to emergency relief design for runaway reactions

Typical deliverables

• Dust hazard analysis report
• Recommended test program and interpretation of results
• Housekeeping and accumulation guidance
• Chemical reactivity screening and compatibility matrix
• Recommendations for prevention, protection and isolation

Frequently asked questions