DOT Hazmat Class 4: Flammable Solids
Materials that ignite easily, react with water, or spontaneously combust—avoid incompatible actions.
DOT Hazard Class 4 At a Glance
DOT Hazard Class 4 covers Flammable Solids. Materials that ignite easily, react with water, or spontaneously combust—avoid incompatible actions. Common examples include Reactive metals (varies), Self-heating materials, Certain powders, Matches (varies). Use this guide for placard recognition, hazards, first actions, ERG context, and related UN numbers.
Common Hazards of Class 4 Flammable Solids
- Rapid ignition and difficult extinguishment
- Water-reactive hazards (some products)
- Self-heating / spontaneous ignition
How to Recognize Class 4 Flammable Solids
- Placards indicating Class 4.x
- Powders, granules, or packaged solids
- Heat/smoke without obvious flame source
First Actions for Class 4 Flammable Solids Incidents
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
Critical Don'ts for Class 4 Flammable Solids
- Do not apply water to unknown reactive solids
- Do not disturb powders without PPE/controls
- Do not assume normal Class A behavior
Common Products & Examples — Class 4 Flammable Solids
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)
More UN numbers discoverable via the Hazmat Hub. Always consult current ERG + SOP/SOG for operations.