UN 2458 — Hexadiene
Placard: Flammable. ERG Guide 130. Training/quick-reference only — use current ERG + SOP/SOG for incident-specific actions.
UN 2458 is Hexadiene, a highly flammable hydrocarbon liquid assigned to ERG Guide 130. Heavy vapors can travel to ignition sources and flash back.
Hazard overview: HIGHLY FLAMMABLE hydrocarbon liquid; vapors may ignite and form explosive mixtures with air. Vapors are heavier than air and may travel to ignition sources and flash back. Vapor explosion hazard exists in drains, sewers, basements and confined areas.
Response guidance: For UN 2458, isolate the area, avoid skin contact and use SCBA where vapor, dust, gas or fire is present. Control ignition or contamination hazards and contain runoff using SDS and ERG 130.
Firefighter training notes: Training for UN 2458 should emphasize exposure routes, SCBA use, vapor/dust monitoring, fire behavior, decontamination, runoff containment and SDS verification. Use ERG 130, SDS and local SOP.
Regulatory context: Hexadiene is regulated as a hazardous material for transport and emergency response. Storage, exposure, spill reporting, waste and fire-code duties depend on quantity, concentration and jurisdiction; verify shipping papers, SDS and local authority requirements.
Storage & handling: Hexadiene should be stored in tightly closed compatible containers with ventilation, secondary containment, restricted access and SDS-based segregation from incompatible materials.
UN 2458 Quick Details
Common Hazards of UN 2458
- HIGHLY FLAMMABLE hydrocarbon liquid; vapors may ignite and form explosive mixtures with air.
- Vapors are heavier than air and may travel to ignition sources and flash back.
- Vapor explosion hazard exists in drains, sewers, basements and confined areas.
- Liquid is insoluble or slightly soluble and may float, spreading fire or contamination.
- Runoff to sewers may create fire or explosion hazards.
- Containers may rupture or explode when heated.
- Some diene/isomer entries may polymerize or vary by isomer; verify SDS and inhibitor status.
Chemical Identity & Physical Properties
Colorless liquid with a mild hydrocarbon odor. Lighter than water and insoluble in water.
| Also known as | 1,5-HexadieneHexa-1,5-dieneDiallylBiallyl |
| CAS Number | 592-48-3 |
| Appearance | Colorless liquid with a mild hydrocarbon odor. Lighter than water and insoluble in water. |
| Flash Point | -26°C (-15°F) |
| Boiling Point | 59-60°C (138-140°F) |
| Vapor Density | 2.8 (heavier than air) |
| Water Reactivity | No significant reaction; insoluble in water |
Fireground Response Guidance — UN 2458
Extinguishing Media
PPE Requirements
Use positive-pressure SCBA for vapor, fire or confined-space exposure. Wear chemical-resistant gloves, eye/face protection and flame-resistant protection as appropriate.
Isolation & Evacuation
First Actions for a UN 2458 Incident
- Call 911 and the emergency response number on the shipping paper, if available.
- Keep unauthorized personnel away and establish incident command.
- Stay upwind, uphill and upstream.
- Eliminate ignition sources if this can be done safely.
- Avoid breathing vapor, dust, gas, mist, smoke or fumes and avoid skin or eye contact.
- Do not touch damaged containers or spilled material without proper training and PPE.
- Ventilate confined spaces only after monitoring and only if properly trained and equipped.
- Use ERG Guide 130, SDS, shipping papers and monitoring to set isolation, evacuation and entry decisions.
📋 Copy & Share Field Card
UN 2458 — HexadieneUse 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.