UN 1055 — Isobutylene
Placard: Flammable Gas. ERG Guide 115. Training/quick-reference only — use current ERG + SOP/SOG for incident-specific actions.
UN 1055 is Isobutylene, a Class 2 flammable gas assigned to ERG Guide 115. It can form explosive vapor-air mixtures, create flashback hazards and involve pressure containers that may rupture when heated.
Hazard overview: UN 1055 presents flammable vapor, flashback and pressure-container hazards. Released gas may migrate before ignition, and fire or heat can cause cylinders, tanks or relief devices to vent, rupture or rocket.
Response guidance: For a UN 1055 incident, responders should confirm the product using shipping papers, cylinder markings, SDS and ERG Guide 115. Establish incident command, isolate the area, stay upwind, eliminate ignition sources when safe, monitor for flammable gas and cool exposed containers from a protected position.
Firefighter training notes: Training for UN 1055 should emphasize flammable vapor behavior, flashback, low-area migration, cylinder heating, relief-device hazards and ignition control. Common errors include approaching through vapor, operating damaged valves, standing near cylinder ends and underestimating explosion potential in confined spaces. Use ERG 115, gas monitoring and local SOP.
Regulatory context: Isobutylene is regulated as a hazardous material for transportation and emergency response purposes. Cylinder, workplace exposure, storage, reporting and environmental requirements may vary by product, quantity and jurisdiction. Responders should verify current requirements through shipping papers, SDS, cylinder markings, facility documents and applicable DOT, OSHA, EPA, NFPA, state or local authority guidance.
Storage & handling: Isobutylene cylinders or containers should be stored secured, well ventilated and away from heat, ignition sources, oxidizers, incompatible gases and physical damage. Storage areas should control leaks, cylinder impact, unauthorized access and accumulation of gas in low or confined spaces.
UN 1055 Quick Details
Common Hazards of UN 1055
- EXTREMELY FLAMMABLE: will be easily ignited by heat, sparks or flames.
- Will form explosive mixtures with air.
- Vapors from liquefied gas may spread along the ground and collect in low or confined areas.
- Vapors may travel to an ignition source and flash back.
- Cylinders or pressure containers may vent, rupture or rocket when heated.
- Liquefied gas contact may cause frostbite or cold burns.
- Released gas can create a wide flammable atmosphere around damaged cylinders, valves or piping.
Chemical Identity & Physical Properties
Colorless gas with a faint petroleum-like odor. Shipped as a liquefied compressed gas under pressure.
| Also known as | 2-MethylpropeneIsobutene2-Methyl-1-propeneLiquefied petroleum gas (LPG component) |
| CAS Number | 115-11-7 |
| Appearance | Colorless gas with a faint petroleum-like odor. Shipped as a liquefied compressed gas under pressure. |
| Flash Point | -76C (-105F) |
| Boiling Point | -7C (20F) |
| Vapor Density | 1.9 (heavier than air) |
| Water Reactivity | No significant reaction with water; slightly soluble |
Fireground Response Guidance — UN 1055
Extinguishing Media
PPE Requirements
Use positive-pressure SCBA for fire, leak, vapor cloud or confined-space operations. Structural firefighting gear may protect against fire conditions, but responders should maintain distance from heated cylinders and follow incident command and local SOP.
Isolation & Evacuation
First Actions for a UN 1055 Incident
- CALL 911. Then call the emergency response telephone number on the shipping paper, if available.
- Keep unauthorized personnel away.
- Stay upwind, uphill and/or upstream.
- Do not touch damaged cylinders, tanks, valves or released material unless properly trained and equipped.
- Eliminate ignition sources if it is safe to do so.
- Many vapors from liquefied gas may spread along the ground and collect in low or confined areas.
- Isolate the spill or leak area for at least 100 meters (330 feet) in all directions.
- Consider initial evacuation for at least 800 meters (1/2 mile) for a large release, fire or heated container.
- Use ERG Guide 115, shipping papers, SDS, gas monitoring and incident command to set protective actions.
📋 Copy & Share Field Card
UN 1055 — IsobutyleneUse 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.