☣️ UN 3336 • CLASS 3
Mercaptan mixture, liquid, flammable, n.o.s.
Placard: Flammable. Training/quick-reference only — use current ERG + SOP/SOG for incident-specific actions.
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⚠️ This page is a quick-reference aid. For real incidents: stage upwind, isolate, deny entry, request Hazmat early, and consult the current ERG + SOP/SOG.
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Quick details
UN 3336
Class: 3
Placard type: Flammable
ERG: Guide 130 (check current ERG)
Isolation: ERG 130: Small spill isolate 30m all directions; large spill isolate 100m all directions; if tank/rail car involved in fire, isolate 800m all directions
Chemical & Response Details
| Also known as | Thiol mixtureMercaptan blendAlkyl mercaptan mixtureSulfhydryl compound mixture |
| Appearance | Clear to pale yellow liquid with strong, offensive, garlic-like or skunk-like odor. Highly volatile at room temperature. |
| Flash Point | Below 23C (73F) - varies by specific mercaptan composition |
| Boiling Point | Typically 35-200C (95-392F) depending on mixture composition |
| Vapor Density | 2-4 (heavier than air) - mercaptan vapors will settle in low areas |
| Water Reactivity | No significant reaction with water, but insoluble and will float; vapors still flammable above water surface |
| Extinguishing | Alcohol-resistant AFFF foam, dry chemical, CO2; regular foam may be ineffective |
| PPE | ⚠️ Level B minimum with SCBA required; extreme odor at very low concentrations may penetrate PPE; full face respiratory protection mandatory |
| Isolation | ERG 130: Small spill isolate 30m all directions; large spill isolate 100m all directions; if tank/rail car involved in fire, isolate 800m all directions |
Chemical details are general reference only. Always verify with current SDS, ERG, and SOP/SOG.
Common hazards (high level)
- 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.
First actions (field-minded)
- CALL 911. Then call emergency response telephone number on shipping paper. If shipping paper
- 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).
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UN 3336 — Mercaptan mixture, liquid, flammable, n. HAZMAT RADIO NOTE — UN 3336
Product: Mercaptan mixture, liquid, flammable, n.o.s.
Class 3 / Flammable / ERG 130
PPE: Level B minimum with SCBA required; extreme odor at very low concentrations may penetrate PPE; full face respiratory protection mandatory
ISOLATION: ERG 130: Small spill isolate 30m all directions; large spill isolate 100m all directions; if tank/rail car involved in fire, isolate 800m all directions
ACTION: Stage upwind · Isolate · Deny entry · Request HazmatRADIO
Use for: Quick radio or face-to-face size-up. Short, structured, field-ready.
=== IC HAZMAT BRIEFING ===
UN 3336 — Mercaptan mixture, liquid, flammable, n.o.s.
Class: 3 | Placard: Flammable | ERG Guide: 130
Appearance: Clear to pale yellow liquid with strong, offensive, garlic-like or skunk-like odor. Highly volatile at room temperature.
Water Reactivity: No significant reaction with water, but insoluble and will float; vapors still flammable above water surface
Extinguishing: Alcohol-resistant AFFF foam, dry chemical, CO2; regular foam may be ineffective
PPE: Level B minimum with SCBA required; extreme odor at very low concentrations may penetrate PPE; full face respiratory protection mandatory
Isolation: ERG 130: Small spill isolate 30m all directions; large spill isolate 100m all directions; if tank/rail car involved in fire, isolate 800m all directions
— Key Hazards —
• 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.
— First Actions —
• CALL 911. Then call emergency response telephone number on shipping paper. If shipping paper
• Keep unauthorized personnel away.
• Stay upwind, uphill and/or upstream.
• Ventilate closed spaces before entering, but only if properly trained and equipped.
SOURCE: allfirefighter.com/hazmat/un/3336 | Always use current ERG + SOP/SOGIC BRIEFING
Use for: Incident command briefing, staging area whiteboard, or pre-entry team brief. Full chemical + response details.
UN3336 Mercaptan mixture, liquid, flammable, n.o.s. Cls3 ERG130 | allfirefighter.com/hazmat/un/3336SMS / 160 CHAR
Use for: Quick text to command or incoming units. Fits in a single SMS. Includes link to full page.
⚠️ Quick-reference only. Always use current ERG + SOP/SOG for incident-specific actions. Page: https://allfirefighter.com/hazmat/un/3336
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FAQ
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.
CALL 911. Then call emergency response telephone number on shipping paper. If shipping paper Keep unauthorized personnel away. Stay upwind, uphill and/or upstream.
Level B minimum with SCBA required; extreme odor at very low concentrations may penetrate PPE; full face respiratory protection mandatory
No. This is a training/quick-reference aid only. Always consult the current ERG Guide 130 and your department SOP/SOG for incident-specific protective actions.
Sources (high level): DOT/PHMSA marking & class concepts + ERG usage principles. This page does not reproduce ERG guide text—always consult the current ERG for incident-specific protective actions.