UN 1238 — Methyl chloroformate
Placard: Toxic. ERG Guide 155. Training/quick-reference only — use current ERG + SOP/SOG for incident-specific actions.
UN 1238 is Methyl chloroformate, a toxic flammable liquid assigned to ERG Guide 155. It creates both vapor-ignition and exposure hazards, so responders should verify the exact product with shipping papers and SDS before close action.
Hazard overview: UN 1238 presents combined toxic exposure and flammable liquid hazards. Vapors can form explosive mixtures and collect in low or sewer areas, while liquid or vapor contact may injure skin, eyes or respiratory tissue.
Response guidance: For a UN 1238 incident, responders should confirm the product using shipping papers, container markings, SDS and ERG Guide 155. 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 1238 should emphasize combined toxicity, skin absorption, vapor travel, ignition control, air monitoring and decontamination. Common errors include treating the incident only as a fire, relying on odor and entering vapor areas without SCBA. Use ERG 155, SDS and incident command.
Regulatory context: Methyl chloroformate is regulated as a hazardous material and may have additional occupational exposure, environmental and waste controls because of toxicity as well as flammability. Verify current requirements through shipping papers, SDS, facility documents and applicable DOT, OSHA, EPA, NFPA, state or local authority guidance.
Storage & handling: Methyl chloroformate should be stored in tightly closed compatible containers in a cool, dry, well-ventilated flammable-liquid area with exposure controls, secondary containment and drain protection. Keep away from heat, ignition sources, oxidizers and incompatible materials.
UN 1238 Quick Details
Common Hazards of UN 1238
- TOXIC and FLAMMABLE; may be harmful or fatal if inhaled, ingested or absorbed through skin.
- Vapors may form explosive mixtures with air and travel to an ignition source.
- Vapors are heavier than air and may collect in low, confined or sewer areas.
- Liquid or vapor may irritate or injure eyes, skin and respiratory tissue.
- Fire may produce irritating, corrosive and/or toxic gases.
- Runoff from fire control or spill control may cause environmental contamination.
- Containers may rupture or explode when heated.
Chemical Identity & Physical Properties
Colorless liquid with a pungent, irritating odor. Denser than water and volatile at room temperature.
| Also known as | Chloromethyl formateFormic acid chloromethyl esterMethyl chlorocarbonateMethylchloroformateMCF |
| CAS Number | 79-22-1 |
| Appearance | Colorless liquid with a pungent, irritating odor. Denser than water and volatile at room temperature. |
| Flash Point | 12°C (54°F) |
| Boiling Point | 71°C (160°F) |
| Vapor Density | 3.3 (heavier than air) |
| Water Reactivity | Reacts slowly with water, releasing HCl and CO2; avoid direct water contact, use water spray carefully |
Fireground Response Guidance — UN 1238
Extinguishing Media
PPE Requirements
Use positive-pressure SCBA for vapor, fire or confined-space exposure. Chemical-resistant gloves, boots, splash protection and protective clothing should be selected using SDS, monitoring results and incident command because inhalation or skin absorption may be serious.
Isolation & Evacuation
First Actions for a UN 1238 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.
- Avoid breathing vapors and avoid skin or eye contact with liquid.
- 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 155, shipping papers, SDS and local SOP for protective actions and entry decisions.
📋 Copy & Share Field Card
UN 1238 — Methyl chloroformateUse 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.