UN 3221 — Self-reactive liquid type B
Placard: Flammable Solid. ERG Guide 149. Training/quick-reference only — use current ERG + SOP/SOG for incident-specific actions.
UN 3221 is Self-reactive liquid type B, a thermally unstable self-reactive material. The response depends on type, package size and temperature-control data.
Hazard overview: Self-reactive substances can decompose without external oxygen. Heat, contamination or loss of temperature control can lead to rapid pressure rise, fire or explosion.
Response guidance: Isolate the area, keep people away from container ends and control temperature if safe. Use ERG 149, SDS and shipping papers to confirm SADT, emergency temperature and compatible extinguishing methods.
Firefighter training notes: Train responders to recognize self-reactive materials, SADT concerns, temperature control needs and explosive decomposition risk under fire exposure.
Regulatory context: Self-reactive substances are regulated by type and temperature-control requirements; verify classification, control temperature and emergency control temperature where listed.
Storage & handling: Store under specified temperature limits, away from heat, sunlight, contamination and incompatible chemicals. Verify stabilization and emergency temperature controls.
UN 3221 Quick Details
Common Hazards of UN 3221
- Self-reactive material can undergo self-accelerating decomposition if heated or contaminated.
- May burn violently and produce large amounts of heat, smoke or gas.
- Containers may rupture, vent or explode when decomposition begins.
- Vapors, dust or decomposition products may be toxic or irritating.
- Fire, friction, impact or incompatible chemicals can trigger decomposition.
- Some formulations require temperature control; verify SADT and emergency temperature data.
- Exact formulation and inhibitor/stabilizer status must be confirmed before response.
Chemical Identity & Physical Properties
Variable appearance depending on specific formulation; typically clear to colored liquids that are thermally unstable organic compounds capable of exothermic decomposition without external oxygen.
| Also known as | Self-reactive liquid type BOrganic peroxide type B liquidSelf-accelerating decomposition liquidSADT liquid |
| Appearance | Variable appearance depending on specific formulation; typically clear to colored liquids that are thermally unstable organic compounds capable of exothermic decomposition without external oxygen. |
| Flash Point | Variable by formulation, typically <23C (<73F) for flammable self-reactive liquids |
| Boiling Point | Variable by formulation, many decompose before boiling |
| Vapor Density | Variable by formulation, typically >1 (heavier than air) |
| Water Reactivity | Generally no violent water reaction, but avoid introducing water which may affect thermal stability |
Fireground Response Guidance — UN 3221
Extinguishing Media
PPE Requirements
Use SCBA and protective clothing. For active decomposition, fire involvement or unknown formulation, use remote operations and specialist hazmat support rather than close entry.
Isolation & Evacuation
First Actions for a UN 3221 Incident
- Call 911 and the emergency response number on the shipping paper, if available.
- Keep unauthorized personnel away and establish incident command before close approach.
- Stay upwind, uphill and upstream; avoid low areas where vapors or gases may collect.
- Avoid breathing vapors, dust, smoke or decomposition products and avoid skin or eye contact.
- Do not touch damaged containers or spilled material without appropriate PPE and monitoring.
- Ventilate confined spaces only if trained, equipped and authorized by incident command.
- Use ERG, SDS, shipping papers and atmospheric/radiation monitoring for final isolation and control decisions.
📋 Copy & Share Field Card
UN 3221 — Self-reactive liquid type BUse for: Quick radio or face-to-face size-up. Short, structured, field-ready.
Use for: Incident command briefing, staging area whiteboard, or pre-entry team brief.
Use for: Quick text to command or incoming units. Fits in a single SMS.