UN 1001 — Acetylene, dissolved
Placard: Flammable Gas. ERG Guide 116. Training/quick-reference only — use current ERG + SOP/SOG for incident-specific actions.
UN 1001 is Acetylene, dissolved, a Class 2 flammable gas assigned to ERG Guide 116. It is an extremely flammable welding and cutting gas shipped dissolved in solvent inside cylinders, with serious flashback, explosion and cylinder-heating hazards.
Hazard overview: UN 1001 presents a severe flammable gas and cylinder explosion hazard. Acetylene forms explosive mixtures with air, ignites easily and can flash back to the leak source. Under heat, pressure or contamination, acetylene can become unstable, so fire-exposed cylinders require cautious isolation, cooling decisions and specialist assessment.
Response guidance: For a UN 1001 incident, responders should confirm the product using cylinder markings, shipping papers, SDS and ERG Guide 116. Establish incident command, isolate the area, remove ignition sources when safe, avoid operating damaged valves, cool fire-exposed cylinders from a protected position if directed by SOP, and consider withdrawal if cylinders are heated, venting or unstable.
Firefighter training notes: Training should emphasize acetylene cylinder construction, dissolved gas behavior, flashback, unstable decomposition and the danger of heated cylinders. Common tactical errors include moving fire-exposed cylinders too early, standing near valve ends, assuming a small flame means low risk, failing to isolate for cylinder rupture potential and ignoring ignition sources around leaking gas.
Regulatory context: Acetylene, dissolved, is regulated as a Class 2 flammable gas for transportation and emergency response purposes. Cylinder handling, storage, workplace fire protection and reporting requirements may apply depending on quantity, use and jurisdiction. Responders should verify current requirements through shipping papers, SDS, cylinder markings, facility documents and applicable DOT, OSHA, NFPA, state or local authority guidance.
Storage & handling: Acetylene cylinders should be stored upright, secured and well ventilated, away from heat, ignition sources, oxygen cylinders, oxidizers and physical damage. Cylinders should be protected from falling, valve damage and excessive temperature, with separation and fire protection practices maintained according to SDS, facility procedures and local code requirements.
UN 1001 Quick Details
Common Hazards of UN 1001
- EXTREMELY FLAMMABLE: will be easily ignited by heat, sparks or flames.
- Will form explosive mixtures with air.
- Acetylene may react explosively even without air under certain pressure, heat or contamination conditions.
- Vapors may travel to an ignition source and flash back.
- Gas is lighter than air but can still create explosion hazards in confined or poorly ventilated spaces.
- Cylinders exposed to fire may vent flammable gas or rupture when heated.
- Released gas can create a wide flammable atmosphere around damaged cylinders, valves or manifolds.
Chemical Identity & Physical Properties
Acetylene is a colorless gas that may have a faint ether-like odor when pure or a garlic-like odor when impure. It is lighter than air and is transported as a dissolved gas in cylinders, commonly with acetone or another solvent and porous filler for stability.
| Also known as | EthyneNarcylenVinyleneEthine |
| CAS Number | 74-86-2 |
| Appearance | Colorless gas with a faint ethereal odor when pure, garlic-like odor when impure. Lighter than air, shipped dissolved in acetone under pressure in cylinders. |
| Flash Point | Not applicable (gas) |
| Boiling Point | -84C (-119F) |
| Vapor Density | 0.9 (lighter than air) |
| Water Reactivity | No significant reaction with water; slightly soluble |
Fireground Response Guidance — UN 1001
Extinguishing Media
PPE Requirements
Responders should use positive-pressure SCBA for fire, leak or confined-space operations involving acetylene. Structural firefighting gear may protect against fire conditions, but approach, cooling and cylinder handling decisions should follow ERG 116, cylinder condition, incident command and local SOP.
Isolation & Evacuation
First Actions for a UN 1001 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.
- Eliminate ignition sources if it is safe to do so.
- Do not touch damaged cylinders, valves or released gas sources unless properly trained and equipped.
- Do not attempt to move fire-exposed acetylene cylinders unless directed by incident command and specialist guidance.
- 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) if fire, cylinder heating, major leak or explosion risk is present.
- Approach cylinders from the side, avoid valve ends, and operate only under incident command and local SOP.
📋 Copy & Share Field Card
UN 1001 — Acetylene, dissolvedUse 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.