UN 2474 — Thiophosgene
Placard: Toxic. ERG Guide 156. Training/quick-reference only — use current ERG + SOP/SOG for incident-specific actions.
UN 2474 At a Glance
UN 2474 (Thiophosgene) is listed as DOT Class 6 Toxic and is assigned to ERG Guide 156. Use this page to review placard data, common hazards, PPE notes, isolation context, first actions, and related UN numbers.
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.