UN 1111 — Amyl mercaptan
Placard: Flammable. ERG Guide 130. Training/quick-reference only — use current ERG + SOP/SOG for incident-specific actions.
Amyl mercaptan is a highly flammable liquid with a strong, offensive, skunk-like odor, and is commonly used as a solvent. It has a characteristic mercaptan smell and can easily ignite in the presence of heat or sparks.
Hazard overview: Amyl mercaptan is highly flammable and can form explosive mixtures with air, making it a significant hazard in the event of a spill or leak. Vapors can also ignite easily, causing a rapid spread of fire, and have a toxic and offensive odor.
Response guidance: In the event of an amyl mercaptan spill, evacuate the area immediately and isolate the spill to prevent further ignition. Firefighters should use alcohol-resistant foam, dry chemical, or CO2 to extinguish the fire, and wear Level B protective gear with SCBA due to toxic vapors.
UN 1111 Quick Details
Common Hazards of UN 1111
- HIGHLY FLAMMABLE: Will be easily ignited by heat, sparks or flames.
- Vapors may form explosive mixtures with air.
- Vapors may travel to source of ignition and flash back.
- Most vapors are heavier than air. They will spread along the ground and collect in low or confined areas
- Vapor explosion hazard indoors, outdoors or in sewers.
- Those substances designated with a (P) may polymerize explosively when heated or involved in a fire.
- Runoff to sewer may create fire or explosion hazard.
- Containers may explode when heated.
Chemical Identity & Physical Properties
Amyl mercaptan is a colorless to pale yellow liquid with a strong, offensive, skunk-like odor, and has a characteristic mercaptan smell at room temperature.
| Also known as | 1-PentanethiolPentyl mercaptann-Amyl mercaptanPentan-1-thiol |
| CAS Number | 110-66-7 |
| Appearance | Colorless to pale yellow liquid with a strong, offensive, skunk-like odor. Liquid at room temperature with characteristic mercaptan smell. |
| Flash Point | -18°C (0°F) |
| Boiling Point | 126°C (259°F) |
| Vapor Density | 3.6 (heavier than air) |
| Water Reactivity | No significant reaction; immiscible with water, floats on surface |
Fireground Response Guidance — UN 1111
Extinguishing Media
PPE Requirements
Responders should wear Level B minimum protective gear with SCBA due to toxic vapors, and chemical-resistant suits and gloves to prevent skin contact and inhalation of vapors.
Isolation & Evacuation
First Actions for a UN 1111 Incident
- 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 for at least 50 meters (150 feet) in all directions.
- Consider initial downwind evacuation for at least 300 meters (1000 feet).
📋 Copy & Share Field Card
UN 1111 — Amyl 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.