☣️ UN 2256 • CLASS 3
UN 2256 — Cyclohexene
Placard: Flammable. ERG Guide 130. Training/quick-reference only — use current ERG + SOP/SOG for incident-specific actions.
🚒☣️
⚠️ 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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UN 2256 Quick Details
UN 2256
Product name: Cyclohexene
DOT Class: 3
Placard type: Flammable
ERG Guide: 130 (check current ERG)
Initial isolation: ERG 130: Initially isolate 50m in all directions; for large spills isolate 800m downwind; evacuate immediate area if fire
Common Hazards of UN 2256
- HIGHLY FLAMMABLE: Will be easily ignited by heat, sparks or flames.
- Vapors may form explosive mixtures with air.
- Vapors may travel to source of ignition and flash back.
- Most vapors are heavier than air. They will spread along the ground and collect in low or confined areas
- Vapor explosion hazard indoors, outdoors or in sewers.
- Those substances designated with a (P) may polymerize explosively when heated or involved in a fire.
- Runoff to sewer may create fire or explosion hazard.
- Containers may explode when heated.
Chemical Identity & Physical Properties
| Also known as | Tetrahydrobenzene1,2,3,4-TetrahydrobenzeneHexanaphthyleneBenzene tetrahydride |
| CAS Number | 110-83-8 |
| Appearance | Colorless liquid with a sweet, aromatic odor similar to gasoline. Exists as a liquid at room temperature. |
| Flash Point | -6°C (21°F) |
| Boiling Point | 83°C (181°F) |
| Vapor Density | 2.8 (heavier than air) |
| Water Reactivity | Insoluble in water; no significant reaction. Floats on water. |
Chemical details are general reference only. Always verify with current SDS, ERG, and SOP/SOG.
Fireground Response Guidance — UN 2256
Extinguishing Media
AFFF foam, alcohol-resistant foam, CO2, dry chemical, water spray for cooling
PPE Requirements
⚠️ Level B minimum for spill response; SCBA required in vapor areas or confined spaces; chemical-resistant gloves and suit
Isolation & Evacuation
ERG 130: Initially isolate 50m in all directions; for large spills isolate 800m downwind; evacuate immediate area if fire
Always confirm protective actions with the current edition of the Emergency Response Guidebook (ERG Guide 130).
First Actions for a UN 2256 Incident
- CALL 911. Then call emergency response telephone number on shipping paper. If shipping paper
- Keep unauthorized personnel away.
- Stay upwind, uphill and/or upstream.
- Ventilate closed spaces before entering, but only if properly trained and equipped.
- Isolate spill or leak area for at least 50 meters (150 feet) in all directions.
- Consider initial downwind evacuation for at least 300 meters (1000 feet).
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UN 2256 — CyclohexeneHAZMAT RADIO NOTE — UN 2256
Product: Cyclohexene
Class 3 / Flammable / ERG 130
PPE: Level B minimum for spill response; SCBA required in vapor areas or confined spaces; chemical-resistant gloves and suit
ISOLATION: ERG 130: Initially isolate 50m in all directions; for large spills isolate 800m downwind; evacuate immediate area if fire
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 2256 — Cyclohexene
Class: 3 | Placard: Flammable | ERG Guide: 130
Appearance: Colorless liquid with a sweet, aromatic odor similar to gasoline. Exists as a liquid at room temperature.
Water Reactivity: Insoluble in water; no significant reaction. Floats on water.
Extinguishing: AFFF foam, alcohol-resistant foam, CO2, dry chemical, water spray for cooling
PPE: Level B minimum for spill response; SCBA required in vapor areas or confined spaces; chemical-resistant gloves and suit
Isolation: ERG 130: Initially isolate 50m in all directions; for large spills isolate 800m downwind; evacuate immediate area if fire
— Key Hazards —
• HIGHLY FLAMMABLE: Will be easily ignited by heat, sparks or flames.
• Vapors may form explosive mixtures with air.
• Vapors may travel to source of ignition and flash back.
— 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.
• Ventilate closed spaces before entering, but only if properly trained and equipped.
SOURCE: allfirefighter.com/hazmat/un/2256 | Always use current ERG + SOP/SOGIC BRIEFING
Use for: Incident command briefing, staging area whiteboard, or pre-entry team brief. Full chemical + response details.
UN2256 Cyclohexene Cls3 ERG130 | ERG 130: Initially isolate 50m in all directions; for large spills isolate 800m | allfirefighter.com/hazmat/un/2256SMS / 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/2256
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Frequently Asked Questions about UN 2256
HIGHLY FLAMMABLE: Will be easily ignited by heat, sparks or flames. Vapors may form explosive mixtures with air. Vapors may travel to source of ignition and flash back. Most vapors are heavier than air. They will spread along the ground and collect in low or confined areas Vapor explosion hazard indoors, outdoors or in sewers. Those substances designated with a (P) may polymerize explosively when heated or involved in a fire. Runoff to sewer may create fire or explosion hazard. Containers may explode when heated.
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 for spill response; SCBA required in vapor areas or confined spaces; chemical-resistant gloves and suit
Water reactivity: Insoluble in water; no significant reaction. Floats on water.. Recommended extinguishing: AFFF foam, alcohol-resistant foam, CO2, dry chemical, water spray for cooling.
ERG Guide 130 recommendation: ERG 130: Initially isolate 50m in all directions; for large spills isolate 800m downwind; evacuate immediate area if fire
No. This is a training/quick-reference aid only. Always consult the current ERG Guide 130 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.