UN 2249 — Dichlorodimethyl ether, symmetrical
Placard: Toxic. ERG Guide 131. Training/quick-reference only — use current ERG + SOP/SOG for incident-specific actions.
UN 2249 is Dichlorodimethyl ether, symmetrical, an extremely toxic chlorinated ether assigned to ERG Guide 131. It is volatile, flammable and a serious carcinogenic exposure concern.
Hazard overview: EXTREMELY TOXIC chlorinated ether; may be fatal if inhaled, ingested or absorbed through skin. Known potent carcinogenic concern; avoid all vapor, liquid and contaminated-surface exposure. Highly volatile and flammable; vapors may form explosive mixtures with air.
Response guidance: For a UN 2249 incident, verify the product with shipping papers, container markings, SDS and ERG Guide 131. Establish incident command, isolate the area, stay upwind, control ignition or incompatibility hazards, prevent runoff, dust or vapor spread and base entry/fire-control actions on monitoring and local SOP.
Firefighter training notes: Training for UN 2249 should emphasize toxic skin/vapor/dust exposure, contaminated clothing, toxic fire products, decontamination waste and runoff containment. Use ERG 131, SDS and local SOP.
Regulatory context: Dichlorodimethyl ether, symmetrical is regulated as a hazardous material for transportation and emergency response purposes. Storage, workplace exposure, emergency planning, spill reporting, waste handling and environmental requirements vary by exact product, concentration, quantity and jurisdiction. Verify current requirements through shipping papers, SDS, container markings and applicable DOT, OSHA, EPA, NFPA, state or local authority guidance.
Storage & handling: Dichlorodimethyl ether, symmetrical should be stored in tightly closed compatible containers in a secure toxic/corrosive-material area with secondary containment, restricted access, ventilation and waste/decontamination planning according to SDS.
UN 2249 Quick Details
Common Hazards of UN 2249
- EXTREMELY TOXIC chlorinated ether; may be fatal if inhaled, ingested or absorbed through skin.
- Known potent carcinogenic concern; avoid all vapor, liquid and contaminated-surface exposure.
- Highly volatile and flammable; vapors may form explosive mixtures with air.
- Hydrolyzes in water or moisture to formaldehyde and hydrochloric acid.
- Vapors are heavier than air and may collect in low or confined areas.
- Fire may produce hydrogen chloride, phosgene-type gases and other toxic/corrosive decomposition products.
- Runoff may carry toxic chlorinated contamination.
Chemical Identity & Physical Properties
Colorless to pale yellow liquid with a suffocating, irritating odor. Volatile at room temperature.
| Also known as | Bis(chloromethyl) etherBCMEChloromethyl ethersym-Dichloromethyl etherOxybis(chloromethane) |
| CAS Number | 542-88-1 |
| Appearance | Colorless to pale yellow liquid with a suffocating, irritating odor. Volatile at room temperature. |
| Flash Point | Not applicable (highly volatile, flammable liquid) |
| Boiling Point | 106C (223F) |
| Vapor Density | 3.9 (heavier than air) |
| Water Reactivity | Hydrolyzes slowly in water, releasing formaldehyde and hydrochloric acid |
Fireground Response Guidance — UN 2249
Extinguishing Media
PPE Requirements
Use positive-pressure SCBA and fully encapsulating chemical protective clothing for close entry or unknown concentrations. Level A is appropriate for significant vapor/liquid exposure due to extreme toxicity and carcinogenic concern.
Isolation & Evacuation
First Actions for a UN 2249 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.
- Avoid breathing vapors, dust, mist, smoke or fumes and avoid skin or eye contact.
- Eliminate ignition sources if safe and keep vapors and runoff out of drains, sewers, basements and low areas.
- Do not touch damaged containers or spilled material unless properly trained and wearing appropriate protective equipment.
- Ventilate closed spaces before entering, but only if properly trained, equipped, monitored and authorized by incident command.
- Isolate the spill or release area and expand the perimeter for fire involvement, vapor spread, dust generation, water reaction or unknown product identity.
- Use ERG Guide 131, shipping papers, SDS, air monitoring and incident command for protective actions.
📋 Copy & Share Field Card
UN 2249 — Dichlorodimethyl ether, symmetricalUse 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.