☣️ UN 3231 • CLASS 4
Self-reactive liquid type B, temperature controlled
Placard: Flammable Solid. Training/quick-reference only — use current ERG + SOP/SOG for incident-specific actions.
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⚠️ This page is a quick-reference aid. For real incidents: stage upwind, isolate, deny entry, request Hazmat early, and consult the current ERG + SOP/SOG.
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Quick details
UN 3231
Class: 4
Placard type: Flammable Solid
ERG: Guide 150 (check current ERG)
Isolation: ERG 150: Initial isolation 100m (330 ft) all directions; for fire, isolate 800m (0.5 mi) all directions; evacuate if cargo or storage gets hot; maintain control temperature at all times
Chemical & Response Details
| Also known as | Self-reactive liquid type BOrganic peroxide type B liquidTemperature-controlled self-reactive substanceSADT-controlled liquid |
| Appearance | Variable appearance depending on specific formulation; typically a liquid organic compound that requires temperature control during transport. May be colorless to yellow with characteristic organic odor. |
| Flash Point | Variable by formulation, typically low (<23C/73F for many formulations) |
| Boiling Point | Variable by formulation, typically 50-200C (122-392F) |
| Vapor Density | Variable by formulation, typically >1 (heavier than air) |
| Water Reactivity | Generally no violent reaction with water, but water may affect thermal stability; avoid uncontrolled dilution |
| Extinguishing | Dry chemical, CO2, alcohol-resistant foam for small fires; large fires may require flooding quantities of water from distance |
| PPE | ⚠️ Level B minimum with SCBA; full chemical protective suit if leak or spill; maintain thermal protection due to decomposition hazards |
| Isolation | ERG 150: Initial isolation 100m (330 ft) all directions; for fire, isolate 800m (0.5 mi) all directions; evacuate if cargo or storage gets hot; maintain control temperature at all times |
Chemical details are general reference only. Always verify with current SDS, ERG, and SOP/SOG.
Common hazards (high level)
- Self-decomposition, self-polymerization, or self-ignition may be triggered by heat, chemical
- Self-accelerating decomposition may occur if the specific "control temperature" is not maintained.
- These materials are particularly sensitive to temperature rises. Above a given "Control Temperature"
- May be ignited by heat, sparks or flames.
- Those substances designated with a (P) may polymerize explosively when heated or involved in a fire.
- Some may decompose explosively when heated or involved in a fire.
- May burn violently. Decomposition or polymerization may be self-accelerating and produce large
- Vapors or dust may form explosive mixtures with air.
First actions (field-minded)
- CALL 911. Then call emergency response telephone number on shipping paper. If shipping paper
- Keep unauthorized personnel away.
- Stay upwind, uphill and/or upstream.
- Isolate spill or leak area in all directions for at least 50 meters (150 feet) for liquids and at least 25 meters
- Consider initial evacuation for at least 250 meters (800 feet) in all directions.
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UN 3231 — Self-reactive liquid type B, temperature HAZMAT RADIO NOTE — UN 3231
Product: Self-reactive liquid type B, temperature controlled
Class 4 / Flammable Solid / ERG 150
PPE: Level B minimum with SCBA; full chemical protective suit if leak or spill; maintain thermal protection due to decomposition hazards
ISOLATION: ERG 150: Initial isolation 100m (330 ft) all directions; for fire, isolate 800m (0.5 mi) all directions; evacuate if cargo or storage gets hot; maintain control temperature at all times
ACTION: Stage upwind · Isolate · Deny entry · Request HazmatRADIO
Use for: Quick radio or face-to-face size-up. Short, structured, field-ready.
=== IC HAZMAT BRIEFING ===
UN 3231 — Self-reactive liquid type B, temperature controlled
Class: 4 | Placard: Flammable Solid | ERG Guide: 150
Appearance: Variable appearance depending on specific formulation; typically a liquid organic compound that requires temperature control during transport. May be colorless to yellow with characteristic organic odor.
Water Reactivity: Generally no violent reaction with water, but water may affect thermal stability; avoid uncontrolled dilution
Extinguishing: Dry chemical, CO2, alcohol-resistant foam for small fires; large fires may require flooding quantities of water from distance
PPE: Level B minimum with SCBA; full chemical protective suit if leak or spill; maintain thermal protection due to decomposition hazards
Isolation: ERG 150: Initial isolation 100m (330 ft) all directions; for fire, isolate 800m (0.5 mi) all directions; evacuate if cargo or storage gets hot; maintain control temperature at all times
— Key Hazards —
• Self-decomposition, self-polymerization, or self-ignition may be triggered by heat, chemical
• Self-accelerating decomposition may occur if the specific "control temperature" is not maintained.
• These materials are particularly sensitive to temperature rises. Above a given "Control Temperature"
— First Actions —
• CALL 911. Then call emergency response telephone number on shipping paper. If shipping paper
• Keep unauthorized personnel away.
• Stay upwind, uphill and/or upstream.
• Isolate spill or leak area in all directions for at least 50 meters (150 feet) for liquids and at least 25 meters
SOURCE: allfirefighter.com/hazmat/un/3231 | Always use current ERG + SOP/SOGIC BRIEFING
Use for: Incident command briefing, staging area whiteboard, or pre-entry team brief. Full chemical + response details.
UN3231 Self-reactive liquid type B, temperature controlled Cls4 ERG150 | allfirefighter.com/hazmat/un/3231SMS / 160 CHAR
Use for: Quick text to command or incoming units. Fits in a single SMS. Includes link to full page.
⚠️ Quick-reference only. Always use current ERG + SOP/SOG for incident-specific actions. Page: https://allfirefighter.com/hazmat/un/3231
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FAQ
Self-decomposition, self-polymerization, or self-ignition may be triggered by heat, chemical Self-accelerating decomposition may occur if the specific "control temperature" is not maintained. These materials are particularly sensitive to temperature rises. Above a given "Control Temperature" May be ignited by heat, sparks or flames. Those substances designated with a (P) may polymerize explosively when heated or involved in a fire. Some may decompose explosively when heated or involved in a fire. May burn violently. Decomposition or polymerization may be self-accelerating and produce large Vapors or dust may form explosive mixtures with air.
CALL 911. Then call emergency response telephone number on shipping paper. If shipping paper Keep unauthorized personnel away. Stay upwind, uphill and/or upstream.
Level B minimum with SCBA; full chemical protective suit if leak or spill; maintain thermal protection due to decomposition hazards
No. This is a training/quick-reference aid only. Always consult the current ERG Guide 150 and your department SOP/SOG for incident-specific protective actions.
Sources (high level): DOT/PHMSA marking & class concepts + ERG usage principles. This page does not reproduce ERG guide text—always consult the current ERG for incident-specific protective actions.