UN 2601 — Cyclobutane
Placard: Flammable Gas. ERG Guide 115. Training/quick-reference only — use current ERG + SOP/SOG for incident-specific actions.
Cyclobutane is an extremely flammable liquefied gas. Response priorities are ignition control, vapor monitoring, cylinder cooling and prevention of confined-space explosions.
Hazard overview: A release can form a heavy vapor cloud that moves along the ground and ignites at a distance. Heated cylinders can fail violently, and cold liquid contact can injure skin.
Response guidance: Evacuate the vapor area, eliminate ignition sources and stop the leak only if safe. Cool containers from maximum distance and do not extinguish a burning gas leak unless the flow can be stopped.
Firefighter training notes: Training should emphasize flammable gas leak tactics, vapor cloud control, BLEVE awareness and the rule against extinguishing gas flames unless the leak can be stopped.
Regulatory context: UN 2601 is Cyclobutane, Class 2.1 flammable gas. Verify cylinder markings, quantity and emergency shutoff information from shipping papers and SDS.
Storage & handling: Store cylinders secured, ventilated and away from heat, oxidizers and ignition sources. Protect valves from impact and keep containers out of direct sun or fire exposure.
UN 2601 Quick Details
Common Hazards of UN 2601
- Extremely flammable liquefied gas; vapors can ignite easily and flash back.
- Vapors are heavier than air and may travel along the ground to ignition sources.
- Released liquid or cold gas can cause frostbite.
- Cylinders may rupture or BLEVE when heated in a fire.
- Vapor clouds can explode in confined spaces, sewers or low areas.
- Fire may produce carbon monoxide and carbon dioxide.
- Static discharge, sparks, open flames and hot surfaces can ignite the release.
Chemical Identity & Physical Properties
Cyclobutane is a liquefied compressed gas. It is colorless and forms flammable vapor that can collect in low areas.
| Also known as | TetramethyleneCyclobutane gasCB |
| CAS Number | 287-23-0 |
| Appearance | Colorless gas with a mild petroleum-like odor. Exists as a compressed liquefied gas under pressure at room temperature. |
| Flash Point | -10C (14F) |
| Boiling Point | 13C (55F) |
| Vapor Density | 1.9 (heavier than air) |
| Water Reactivity | No significant chemical reaction with water expected; water spray can help cool containers and reduce vapor concentration when used safely. |
Fireground Response Guidance — UN 2601
Extinguishing Media
PPE Requirements
Use SCBA and full protective clothing for fire conditions. For leaks, use flammable gas monitoring, flame-resistant protection and frostbite protection where liquid contact is possible.
Isolation & Evacuation
First Actions for a UN 2601 Incident
- Call 911 and the emergency response number shown on shipping papers; confirm the material with ERG, SDS and container markings.
- Keep unauthorized personnel away and establish hot, warm and cold zones before entry.
- Stay upwind, uphill and upstream; avoid low areas where vapors, dust or runoff may collect.
- Avoid breathing vapors, dust, mist or decomposition products and prevent skin or eye contact.
- Do not touch damaged packages or containers unless properly trained and wearing suitable chemical PPE.
- Ventilate confined spaces only after atmospheric monitoring and only with trained, equipped personnel.
- Use ERG Guide 115, SDS, shipping papers and monitoring results for isolation, PPE and fire-control decisions.
📋 Copy & Share Field Card
UN 2601 — CyclobutaneUse 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.