UN 2363 — Ethyl mercaptan
Placard: Flammable. ERG Guide 129. Training/quick-reference only — use current ERG + SOP/SOG for incident-specific actions.
UN 2363 is Ethyl mercaptan, a flammable sulfur-containing liquid assigned to ERG Guide 129. Strong odor does not replace air monitoring, and fire can produce sulfur oxides.
Hazard overview: FLAMMABLE sulfur-containing liquid; vapors may ignite and form explosive mixtures with air. Very strong odor may be detectable at low levels, but odor is not a safe exposure guide. Vapors are heavier than air and may travel to ignition sources and flash back.
Response guidance: For UN 2363, isolate the area, eliminate ignition sources, keep vapors out of drains and use SCBA in vapor or fire conditions. Cool containers from a protected distance and choose foam, dry chemical or CO2 based on SDS and ERG 129.
Firefighter training notes: Training for UN 2363 should emphasize vapor travel, odor limits, toxic fire products, sewer flashback, SCBA use, runoff control and foam selection. Use ERG 129, SDS and local SOP.
Regulatory context: Ethyl mercaptan 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: Ethyl mercaptan should be stored in approved flammable-liquid containers with ventilation, bonding/grounding where required, spill containment and separation from heat, ignition sources, oxidizers and incompatible materials.
UN 2363 Quick Details
Common Hazards of UN 2363
- FLAMMABLE sulfur-containing liquid; vapors may ignite and form explosive mixtures with air.
- Very strong odor may be detectable at low levels, but odor is not a safe exposure guide.
- Vapors are heavier than air and may travel to ignition sources and flash back.
- Liquid or vapor may irritate eyes, skin and respiratory tissue.
- Fire may produce sulfur oxides, carbon monoxide and irritating/toxic smoke.
- Runoff to sewers may create fire, explosion and odor/toxic contamination hazards.
- Containers may rupture or explode when heated.
Chemical Identity & Physical Properties
Colorless to pale yellow liquid with an extremely strong, penetrating garlic or skunk-like odor. Highly volatile at room temperature.
| Also known as | EthanethiolEthyl sulfhydrateEthyl thioalcoholThioethyl alcoholMercaptoethane |
| CAS Number | 75-08-1 |
| Appearance | Colorless to pale yellow liquid with an extremely strong, penetrating garlic or skunk-like odor. Highly volatile at room temperature. |
| Flash Point | -48C (-54F) |
| Boiling Point | 35C (95F) |
| Vapor Density | 2.1 (heavier than air) |
| Water Reactivity | No significant reaction; slightly soluble in water |
Fireground Response Guidance — UN 2363
Extinguishing Media
PPE Requirements
Use positive-pressure SCBA for vapor, fire or confined-space exposure. Wear chemical-resistant gloves, eye/face protection and flame-resistant protection as appropriate.
Isolation & Evacuation
First Actions for a UN 2363 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; keep responders out of low vapor areas.
- Eliminate ignition sources if this can be done safely.
- Avoid breathing vapor, mist or smoke and avoid skin or eye contact.
- 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 129, SDS, shipping papers and air monitoring to set isolation, evacuation and entry decisions.
📋 Copy & Share Field Card
UN 2363 — Ethyl 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.