UN 1234 — Methylal
Placard: Flammable. ERG Guide 127. Training/quick-reference only — use current ERG + SOP/SOG for incident-specific actions.
UN 1234 is Methylal, a Class 3 flammable liquid assigned to ERG Guide 127. It can generate vapors that ignite easily, travel to ignition sources and flash back.
Hazard overview: UN 1234 presents flammable vapor, flashback and container-heating hazards. Vapors are typically heavier than air and may collect in low, confined or sewer areas where ignition can cause a vapor explosion.
Response guidance: For a UN 1234 incident, responders should confirm the product using shipping papers, container markings, SDS and ERG Guide 127. Establish incident command, isolate the area, stay upwind and uphill, remove ignition sources when safe, keep vapors or runoff out of sewers and use compatible fire-control agents from a protected position.
Firefighter training notes: Training for UN 1234 should emphasize flammable liquid vapor travel, flashback, sewer vapor explosion risk, foam compatibility, container cooling and atmospheric monitoring. Common errors include standing downwind, allowing runoff into drains and ignoring low-area vapor collection. Use ERG 127, SDS and local SOP.
Regulatory context: Methylal is regulated as a hazardous material for transportation and emergency response purposes. Transportation, workplace exposure, spill reporting, waste handling, storage and environmental requirements may vary by formulation, quantity and jurisdiction. Verify current requirements through shipping papers, SDS, facility documents and applicable DOT, OSHA, EPA, NFPA, state or local authority guidance.
Storage & handling: Methylal should be stored in tightly closed compatible containers in a cool, dry, well-ventilated flammable-liquid storage area. Keep away from heat, sparks, open flames, oxidizers and incompatible materials, with bonding/grounding, secondary containment and drain protection where required.
UN 1234 Quick Details
Common Hazards of UN 1234
- HIGHLY FLAMMABLE: will be easily ignited by heat, sparks or flames.
- Vapors may form explosive mixtures with air.
- Vapors may travel to an ignition source and flash back.
- Most vapors are heavier than air and may spread along the ground into low or confined areas.
- Vapor explosion hazard exists indoors, outdoors or in sewers.
- Runoff to sewer may create fire or explosion hazard.
- Containers may rupture or explode when heated.
Chemical Identity & Physical Properties
Colorless, volatile liquid with a chloroform-like or ethereal odor. Highly mobile and evaporates readily at room temperature.
| Also known as | DimethoxymethaneFormalMethylene dimethyl etherDimethyl formal |
| CAS Number | 109-87-5 |
| Appearance | Colorless, volatile liquid with a chloroform-like or ethereal odor. Highly mobile and evaporates readily at room temperature. |
| Flash Point | -32°C (-26°F) |
| Boiling Point | 42°C (108°F) |
| Vapor Density | 2.6 (heavier than air) |
| Water Reactivity | Slightly soluble in water; no significant reaction |
Fireground Response Guidance — UN 1234
Extinguishing Media
PPE Requirements
Use positive-pressure SCBA for fire, heavy vapor or confined-space exposure. Chemical-resistant gloves, splash protection and protective clothing should be selected using SDS, product concentration and incident command.
Isolation & Evacuation
First Actions for a UN 1234 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 or walk through spilled liquid unless properly trained and wearing appropriate protective equipment.
- Ventilate closed spaces before entering, but only if properly trained, equipped and authorized by incident command.
- Isolate the spill or leak area for at least 50 meters (150 feet) in all directions.
- For large spills, fire involvement or strong vapor movement, expand isolation and consider downwind evacuation based on monitoring and incident command.
- Use ERG Guide 127, shipping papers, SDS and local SOP for protective actions and entry decisions.
📋 Copy & Share Field Card
UN 1234 — MethylalUse 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.