UN 2346 — Butanedione
Placard: Flammable. ERG Guide 127. Training/quick-reference only — use current ERG + SOP/SOG for incident-specific actions.
UN 2346 is Butanedione, a volatile flammable diketone assigned to ERG Guide 127. Vapor ignition and respiratory exposure are the main emergency concerns.
Hazard overview: HIGHLY FLAMMABLE diketone 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 of concentrated vapor can seriously irritate or injure the respiratory tract.
Response guidance: For UN 2346, isolate the area, eliminate ignition sources, keep vapors out of drains and use SCBA in vapor or fire conditions. Cool containers from a protected distance and select foam/dry chemical/CO2 based on the SDS.
Firefighter training notes: Training for UN 2346 should emphasize vapor travel, low-area accumulation, sewer flashback, foam selection, ignition control, container cooling and vapor monitoring. Use ERG 127, SDS and local SOP.
Regulatory context: Butanedione 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: Butanedione should be stored in approved flammable-liquid containers with ventilation, bonding/grounding where required, spill containment and separation from heat, ignition sources, oxidizers and incompatible materials.
UN 2346 Quick Details
Common Hazards of UN 2346
- HIGHLY FLAMMABLE diketone 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 of concentrated vapor can seriously irritate or injure the respiratory tract.
- Vapor explosion hazard exists in drains, basements and confined areas.
- Runoff to sewers may create fire or explosion hazards.
- Fire may produce carbon monoxide and irritating/toxic smoke.
- Containers may rupture or explode when heated.
Chemical Identity & Physical Properties
Yellow to green liquid with a strong, pungent buttery odor. Exists as a liquid at room temperature.
| Also known as | Diacetyl2,3-ButanedioneBiacetylDimethyl diketoneDimethylglyoxal |
| CAS Number | 431-03-8 |
| Appearance | Yellow to green liquid with a strong, pungent buttery odor. Exists as a liquid at room temperature. |
| Flash Point | -2°C (28°F) |
| Boiling Point | 88°C (190°F) |
| Vapor Density | 3.0 (heavier than air) |
| Water Reactivity | Soluble in water; no violent reaction expected |
Fireground Response Guidance — UN 2346
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 2346 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; keep responders out of low vapor areas.
- Eliminate ignition sources if this can be done safely.
- Avoid breathing vapor, mist or smoke 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 127, SDS, shipping papers and air monitoring to set isolation, evacuation and entry decisions.
📋 Copy & Share Field Card
UN 2346 — ButanedioneUse 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.