UN 2474 — Thiophosgene
Placard: Toxic. ERG Guide 156. Training/quick-reference only — use current ERG + SOP/SOG for incident-specific actions.
UN 2474 is Thiophosgene, an extremely toxic corrosive volatile liquid assigned to ERG Guide 156. Moisture reaction and heavy vapor control are critical.
Hazard overview: EXTREMELY TOXIC and CORROSIVE volatile liquid; inhalation, ingestion or skin contact may be fatal. Reacts with water or moist air to release hydrogen chloride, hydrogen sulfide and other toxic/corrosive gases. Vapors are much heavier than air and may collect in low or confined areas.
Response guidance: For UN 2474, isolate the spill, stay upwind and use SCBA with chemical protection. Control moisture contact, contain acidic/toxic runoff and use dry compatible agents under SDS and ERG 156 guidance.
Firefighter training notes: Training for UN 2474 should emphasize water-reactive corrosive fuming, dry-agent selection, SCBA/Level A decisions, decontamination and acidic/toxic runoff control. Use ERG 156, SDS and local SOP.
Regulatory context: Thiophosgene is regulated as a hazardous material for transport and emergency response. Storage, exposure, spill reporting, waste and fire-code duties depend on quantity, concentration and jurisdiction; verify shipping papers, SDS and local authority requirements.
Storage & handling: Thiophosgene should be stored dry in tightly closed compatible containers away from water, moisture, bases, oxidizers/reducing agents where incompatible, heat and unauthorized access. Provide secondary containment.
UN 2474 Quick Details
Common Hazards of UN 2474
- EXTREMELY TOXIC and CORROSIVE volatile liquid; inhalation, ingestion or skin contact may be fatal.
- Reacts with water or moist air to release hydrogen chloride, hydrogen sulfide and other toxic/corrosive gases.
- Vapors are much heavier than air and may collect in low or confined areas.
- Combustible material: may burn but does not ignite readily; heated vapors may form explosive mixtures.
- Fire may produce hydrogen chloride, sulfur oxides, phosgene-type gases and other toxic smoke.
- Runoff may be acidic, toxic and corrosive.
- Containers may rupture or fail when heated or contaminated with water.
Chemical Identity & Physical Properties
Reddish-brown to yellow liquid with a suffocating, pungent odor. Volatile liquid at room temperature, readily vaporizes.
| Also known as | Thiocarbonyl chlorideCarbonothioic dichlorideCSCl2Thiophosgene gas |
| CAS Number | 463-71-8 |
| Appearance | Reddish-brown to yellow liquid with a suffocating, pungent odor. Volatile liquid at room temperature, readily vaporizes. |
| Flash Point | Not applicable (reacts with moisture, decomposes before conventional flash point) |
| Boiling Point | 73C (163F) |
| Vapor Density | 4.0 (much heavier than air) |
| Water Reactivity | Reacts with water and moisture releasing HCl, H2S, and other toxic/corrosive gases; avoid water contact |
Fireground Response Guidance — UN 2474
Extinguishing Media
PPE Requirements
Use positive-pressure SCBA and fully encapsulating chemical protective clothing for close entry or unknown concentrations. Protect against severe toxic/corrosive vapor and splash exposure.
Isolation & Evacuation
First Actions for a UN 2474 Incident
- Call 911 and the emergency response number on the shipping paper, if available.
- Keep unauthorized personnel away and establish incident command.
- Stay upwind, uphill and upstream.
- Avoid breathing vapor, dust, mist, smoke or fumes and avoid skin or eye contact.
- Keep water contact controlled because moisture can increase heat release, corrosive fuming or toxic gas formation.
- Do not touch damaged containers or spilled material without proper training and PPE.
- Ventilate confined spaces only after monitoring and only if properly trained and equipped.
- Use ERG Guide 156, SDS, shipping papers and monitoring to set isolation, evacuation and entry decisions.
📋 Copy & Share Field Card
UN 2474 — ThiophosgeneUse 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.