☣️ DOT Hazmat Classification
Flammable Solids
Materials that ignite easily, react with water, or spontaneously combust—avoid incompatible actions.
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DOT CLASS 4
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Common Hazards — Class 4
- Rapid ignition and difficult extinguishment
- Water-reactive hazards (some products)
- Self-heating / spontaneous ignition
How to Recognize Class 4
- Placards indicating Class 4.x
- Powders, granules, or packaged solids
- Heat/smoke without obvious flame source
First Actions Before Hazmat Team Arrives
Initial priorities for DOT Hazmat Class 4 (Flammable Solids) incidents. These are general guidelines — always verify with shipping papers, consult the current ERG, and follow your SOP/SOG.
- Identify product markings; avoid incompatible extinguishing agents
- Isolate and stage upwind
- Request Hazmat for unknown reactive solids
- Use ERG + SOP for extinguishment guidance
- Prepare for rekindle and extended operations
What NOT To Do — Class 4
- Do not apply water to unknown reactive solids
- Do not disturb powders without PPE/controls
- Do not assume normal Class A behavior
Common Examples — Class 4 Flammable Solids
Reactive metals (varies)Self-heating materialsCertain powdersMatches (varies)
These are representative examples only. Product-specific hazards vary — always confirm via shipping papers and current ERG.
Common UN Numbers in Class 4 (Flammable Solids)
UN 1183EthyldichlorosilaneUN 1242MethyldichlorosilaneUN 1295TrichlorosilaneUN 1309Aluminum powder, coatedUN 1310Ammonium picrate, wetted with not less than 10% waterUN 1312BorneolUN 1313Calcium resinateUN 1314Calcium resinate, fusedUN 1318Cobalt resinate, precipitatedUN 1320Dinitrophenol, wetted with not less than 15% waterUN 1321Dinitrophenolates, wetted with not less than 15% waterUN 1322Dinitroresorcinol, wetted with not less than 15% waterUN 1323FerroceriumUN 1324Films, nitrocellulose baseUN 1325Flammable solid, organic, n.o.s.
More UN numbers discoverable via the Hazmat Hub. Always consult current ERG + SOP/SOG for operations.
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FAQ — DOT Hazmat Class 4 (Flammable Solids)
Certain solids react with water to release heat or flammable/toxic gases—product-specific guidance is essential.
Isolate, identify from distance, request Hazmat, consult ERG/SOP before committing.
Yes—self-heating and deep-seated involvement can cause repeated ignition.
Sources: DOT/PHMSA hazard class concepts, NFPA 704 overview, and ERG usage principles. This guide does not reproduce ERG guide text — always consult the current ERG for incident-specific protective actions.