UN 3246 — Methanesulphonyl chloride
Placard: Toxic. ERG Guide 156. Training/quick-reference only — use current ERG + SOP/SOG for incident-specific actions.
UN 3246 Methanesulphonyl chloride is assigned to ERG Guide 156 for initial emergency response. Clear to pale yellow liquid with a pungent, irritating odor. Fuming liquid at room temperature due to reaction with atmospheric moisture. Verify the exact product from shipping papers and SDS before selecting tactics.
Hazard overview: Primary hazards: a water-reactive hazardous material that can release flammable, toxic or corrosive gases. Combustible material: may burn but does not ignite readily. Substance will react with water (some violently) releasing flammable, toxic or corrosive gases and runoff.
Response guidance: For a UN 3246 incident, isolate the area, keep unauthorized personnel away, stay upwind/uphill and confirm the exact material from shipping papers and SDS. Avoid direct water or foam unless incident command confirms compatibility; use dry agents such as dry chemical, dry sand, lime or soda ash when specified. Follow ERG Guide 156 and local incident command procedures.
UN 3246 Quick Details
Common Hazards of UN 3246
- Combustible material: may burn but does not ignite readily.
- Substance will react with water (some violently) releasing flammable, toxic or corrosive gases and runoff.
- When heated, vapors may form explosive mixtures with air indoors, outdoors and in sewers.
- Most vapors are heavier than air; they spread along the ground and collect in low or confined areas.
- Vapors may travel to source of ignition and flash back.
- Corrosives in contact with metals may evolve flammable hydrogen gas.
- Containers may explode when heated or if contaminated with water.
- TOXIC and/or CORROSIVE; inhalation, ingestion or contact with vapors, dusts or substance may cause severe injury.
Chemical Identity & Physical Properties
Clear to pale yellow liquid with a pungent, irritating odor. Fuming liquid at room temperature due to reaction with atmospheric moisture.
| Also known as | Mesyl chlorideMethanesulfonyl chlorideMSCMethylsulfonyl chloride |
| CAS Number | 124-63-0 |
| Appearance | Clear to pale yellow liquid with a pungent, irritating odor. Fuming liquid at room temperature due to reaction with atmospheric moisture. |
| Flash Point | 110C (230F) |
| Boiling Point | 161-164C (322-327F) |
| Vapor Density | 3.97 (heavier than air) |
| Water Reactivity | Reacts violently with water releasing HCl fumes and heat; do not apply water directly to substance |
Fireground Response Guidance — UN 3246
Extinguishing Media
PPE Requirements
Level B minimum; SCBA required; full chemical-resistant suit due to corrosive fumes and skin hazard
Isolation & Evacuation
First Actions for a UN 3246 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.
- Ventilate closed spaces before entering, but only if properly trained and equipped.
- Isolate spill or leak area in all directions for at least 50 meters (150 feet) for liquids and 25 meters (75 feet) for solids.
- For highlighted materials: see Table 1 - Initial Isolation and Protective Action Distances.
- For non-highlighted materials, increase the initial isolation distance in the downwind direction as needed.
📋 Copy & Share Field Card
UN 3246 — Methanesulphonyl chlorideUse 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.