UN 2603 — Cycloheptatriene
Placard: Flammable. ERG Guide 131. Training/quick-reference only — use current ERG + SOP/SOG for incident-specific actions.
UN 2603 is Cycloheptatriene, a flammable hydrocarbon liquid assigned to ERG Guide 131. Vapor flashback and toxic exposure control are key priorities.
Hazard overview: 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. Inhalation or skin contact may cause irritation or toxic effects depending on exposure.
Response guidance: For UN 2603, isolate the area, eliminate ignition sources when flammable vapors are present and use SCBA. Keep vapors out of drains, cool containers from protection and select foam/dry chemical/CO2 from SDS and ERG 131.
Firefighter training notes: Training for UN 2603 should emphasize vapor travel, sewer flashback, foam selection, ignition control, SCBA use, decontamination, container cooling and runoff containment. Use ERG 131, SDS and local SOP.
Regulatory context: Cycloheptatriene 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: Cycloheptatriene should be stored in approved compatible containers with ventilation, secondary containment and separation from heat, ignition sources, oxidizers and incompatible materials according to SDS.
UN 2603 Quick Details
Common Hazards of UN 2603
- 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.
- Inhalation or skin contact may cause irritation or toxic effects depending on exposure.
- Liquid may float on water or spread as a separate layer, carrying contamination.
- Runoff to sewers may create fire, explosion and environmental hazards.
- Fire may produce carbon monoxide and irritating/toxic smoke.
- Container heating may cause rupture or violent release.
Chemical Identity & Physical Properties
Colorless to pale yellow liquid with a characteristic aromatic hydrocarbon odor. Volatile flammable liquid at room temperature.
| Also known as | 1,3,5-CycloheptatrieneCHTTropilideneCycloheptene trimer |
| CAS Number | 544-25-2 |
| Appearance | Colorless to pale yellow liquid with a characteristic aromatic hydrocarbon odor. Volatile flammable liquid at room temperature. |
| Flash Point | -6C (21F) |
| Boiling Point | 116-118C (241-244F) |
| Vapor Density | 3.2 (heavier than air) |
| Water Reactivity | No significant reaction; insoluble in water, floats on surface |
Fireground Response Guidance — UN 2603
Extinguishing Media
PPE Requirements
Use positive-pressure SCBA for vapor, smoke, 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 2603 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 131, SDS, shipping papers and monitoring to set isolation, evacuation and entry decisions.
📋 Copy & Share Field Card
UN 2603 — CycloheptatrieneUse 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.