UN 1670 — Perchloromethyl mercaptan
Placard: Toxic. ERG Guide 157. Training/quick-reference only — use current ERG + SOP/SOG for incident-specific actions.
UN 1670 is Perchloromethyl mercaptan, a toxic corrosive material assigned to ERG Guide 157. Moisture or water contact can release corrosive and toxic fumes, making dry control and air monitoring important.
Hazard overview: UN 1670 presents toxic inhalation, corrosive fume and water-reactivity hazards. Vapors can collect in low areas, and runoff may spread corrosive toxic contamination.
Response guidance: For a UN 1670 incident, responders should verify the product with shipping papers, package markings, SDS and ERG Guide 157. Establish incident command, isolate the area, stay upwind, prevent dust or vapor exposure, control runoff and choose entry or cleanup actions based on monitoring, SDS and local SOP.
Firefighter training notes: Training for UN 1670 should emphasize water-reactive toxic/corrosive fumes, dry-agent selection, vapor control, decontamination and strict entry control. Use ERG 157, SDS and hazmat SOP.
Regulatory context: Perchloromethyl mercaptan is regulated as a hazardous material for transportation and emergency response purposes. Transportation, workplace exposure, spill reporting, waste handling, storage and environmental requirements may vary by formulation, concentration, quantity and jurisdiction. Verify current requirements through shipping papers, SDS, facility documents and applicable DOT, OSHA, EPA, NFPA, state or local authority guidance.
Storage & handling: Perchloromethyl mercaptan should be stored in tightly closed compatible containers in a cool, dry, well-ventilated secure area away from water, moisture, bases where incompatible, oxidizers, heat and unauthorized access. Protect containers from corrosion, leaks and impact.
UN 1670 Quick Details
Common Hazards of UN 1670
- TOXIC and CORROSIVE; inhalation, ingestion or skin/eye contact may cause severe injury.
- Water or moist air may release toxic and corrosive fumes.
- Reaction with water may generate heat and dense irritating vapor.
- Vapors are heavier than air and may collect in low or confined areas.
- Fire may produce irritating, corrosive and/or toxic gases.
- Runoff may spread toxic and corrosive contamination.
- Containers may rupture or fail when heated.
Chemical Identity & Physical Properties
Yellow to amber oily liquid with a pungent, extremely disagreeable odor. Corrosive and fuming in moist air.
| Also known as | Trichloromethylsulfenyl chlorideTrichloromethanesulfenyl chloridePerchloromethyl mercaptanTrichloromethyl sulfur chlorideCCl3SCl |
| CAS Number | 594-42-3 |
| Appearance | Yellow to amber oily liquid with a pungent, extremely disagreeable odor. Corrosive and fuming in moist air. |
| Flash Point | Not applicable (decomposes before flash point) |
| Boiling Point | 148C (298F) with decomposition |
| Vapor Density | 7.6 (much heavier than air) |
| Water Reactivity | Reacts with water producing toxic and corrosive hydrogen chloride and sulfur dioxide fumes; generates heat |
Fireground Response Guidance — UN 1670
Extinguishing Media
PPE Requirements
Use positive-pressure SCBA and chemical protective clothing selected by hazmat specialists for vapor, fume, liquid or unknown exposure. Level A may be needed for close entry because toxic and corrosive fumes are possible.
Isolation & Evacuation
First Actions for a UN 1670 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.
- Avoid breathing vapors, fumes, dust or mist and avoid all skin or eye contact.
- Keep water and moisture away from released product unless incident command confirms a compatible cooling or control use.
- Do not touch or walk through spilled material unless properly trained and wearing appropriate protective equipment.
- Avoid creating dust clouds or spreading contaminated liquid, powder, solution, runoff or debris.
- Ventilate closed spaces before entering, but only if properly trained, equipped, monitored and authorized by incident command.
- Isolate the spill or leak area and expand the perimeter if dust, vapor, fire involvement or unknown concentration is present.
- Use ERG Guide 157, shipping papers, SDS, air monitoring and incident command for protective actions.
📋 Copy & Share Field Card
UN 1670 — Perchloromethyl mercaptanUse 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.