UN 3054 — Cyclohexyl mercaptan
Placard: Flammable. ERG Guide 129. Training/quick-reference only — use current ERG + SOP/SOG for incident-specific actions.
Cyclohexyl mercaptan (UN 3054) is a flammable, toxic mercaptan liquid with a strong sulfur odor. Response priorities are ignition control, vapor control and exposure prevention.
Hazard overview: UN 3054 vapors can collect in low areas, flash back and produce toxic sulfur-containing smoke in fire. Odor can be detected at low levels but does not prove the area is safe.
Response guidance: Isolate the area, control ignition sources and keep responders upwind. Use alcohol-resistant foam, dry chemical or CO2 for fire control and water spray only for cooling containers. Prevent runoff and avoid liquid contact.
Firefighter training notes: Train crews to control ignition sources and manage odor complaints without relying on odor as an exposure limit.
Regulatory context: UN 3054 is a regulated flammable/toxic mercaptan entry; ERG 129 and SDS should guide initial response.
Storage & handling: Store away from oxidizers, ignition sources and heat in tightly closed containers with ventilation and spill containment.
UN 3054 Quick Details
Common Hazards of UN 3054
- Flammable liquid; vapors can ignite from heat, sparks or flames.
- Vapors are heavier than air and may travel to ignition sources and flash back.
- Toxic or irritating exposure can occur by inhalation, ingestion or skin contact.
- Strong mercaptan odor can cause complaints but is not a safe exposure indicator.
- Fire may release sulfur oxides and other toxic gases.
- Runoff may spread contamination and odor over a wide area.
- Containers may rupture when heated.
Chemical Identity & Physical Properties
Colorless to pale yellow liquid with a strong, unpleasant sulfur or skunk-like odor. Oily consistency at room temperature.
| Also known as | CyclohexanethiolCyclohexyl thiolMercaptocyclohexaneCyclohexyl hydrosulfide |
| CAS Number | 1569-69-3 |
| Appearance | Colorless to pale yellow liquid with a strong, unpleasant sulfur or skunk-like odor. Oily consistency at room temperature. |
| Flash Point | 43°C (109°F) |
| Boiling Point | 158-159°C (316-318°F) |
| Vapor Density | 4.0 (heavier than air) |
| Water Reactivity | No significant reaction with water; immiscible and floats on water surface |
Fireground Response Guidance — UN 3054
Extinguishing Media
PPE Requirements
Use positive-pressure SCBA and chemical-resistant clothing. Select glove and suit materials from the SDS for mercaptan liquid contact.
Isolation & Evacuation
First Actions for a UN 3054 Incident
- Call 911 and the emergency response number on the shipping paper, if available.
- Eliminate ignition sources; use non-sparking tools and control traffic around the spill.
- Keep unauthorized personnel away and stay upwind, uphill and upstream.
- Avoid breathing vapors and prevent liquid contact with skin, eyes and clothing.
- Do not enter low areas, drains or confined spaces unless trained and equipped.
- Use ERG 131, SDS, shipping papers and monitoring to set isolation and evacuation distances.
- Contain runoff only if it can be done safely with proper PPE.
📋 Copy & Share Field Card
UN 3054 — Cyclohexyl 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.