UN 1239 — Methyl chloromethyl ether
Placard: Toxic. ERG Guide 131. Training/quick-reference only — use current ERG + SOP/SOG for incident-specific actions.
Methyl chloromethyl ether is a highly volatile and toxic substance that can be fatal if inhaled, ingested, or absorbed through the skin. It is a colorless liquid with a pungent and irritating odor, requiring immediate attention in case of an emergency.
Hazard overview: Inhalation or contact with methyl chloromethyl ether will irritate or burn skin and eyes, and may cause respiratory problems. Prolonged exposure can lead to serious health issues, including cancer, due to its carcinogenic properties.
Response guidance: In case of an emergency, evacuate the area immediately and call for professional help, wearing Level A protective gear, including SCBA and impervious suit. Isolate the area within 100m in all directions and evacuate 800m downwind if there is a large spill or fire.
UN 1239 Quick Details
Common Hazards of UN 1239
- TOXIC; may be fatal if inhaled, ingested or absorbed through skin.
- Inhalation or contact with some of these materials will irritate or burn skin and eyes.
- Methyl chloroacetate (UN2295) is an eye irritant/lachrymator (causes flow of tears).
- Fire will produce irritating, corrosive and/or toxic gases.
- Vapors may cause dizziness or asphyxiation, especially when in closed or confined areas.
- Runoff from fire control or dilution water may cause environmental contamination.
- HIGHLY FLAMMABLE: Will be easily ignited by heat, sparks or flames.
- Vapors may form explosive mixtures with air.
Chemical Identity & Physical Properties
Methyl chloromethyl ether is a colorless liquid with a pungent and irritating odor, highly volatile at room temperature.
| Also known as | Chloromethyl methyl etherCMMEChlorodimethyl etherMonochlorodimethyl ether |
| CAS Number | 107-30-2 |
| Appearance | Colorless liquid with a pungent, irritating odor. Highly volatile at room temperature. |
| Flash Point | -8C (18F) |
| Boiling Point | 59C (138F) |
| Vapor Density | 2.8 (heavier than air) |
| Water Reactivity | Decomposes slowly in water, producing HCl and formaldehyde; avoid prolonged contact |
Fireground Response Guidance — UN 1239
Extinguishing Media
PPE Requirements
Level A protective gear, including SCBA and impervious suit, is required when handling methyl chloromethyl ether due to its toxic and carcinogenic properties.
Isolation & Evacuation
First Actions for a UN 1239 Incident
- Keep unauthorized personnel away.
- Stay upwind, uphill and/or upstream.
- Ventilate closed spaces before entering, but only if properly trained and equipped.
- Isolate spill or leak area for at least 50 meters (150 feet) in all directions.
- For highlighted materials: see Table 1 - Initial Isolation and Protective Action Distances.
- For non-highlighted materials: increase the immediate precautionary measure distance, in the downwind
📋 Copy & Share Field Card
UN 1239 — Methyl chloromethyl etherUse 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.