☣️ UN 1064 • CLASS 2
Methyl mercaptan
Placard: Toxic Gas. 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 1064
Class: 2
Placard type: Toxic Gas
ERG: Guide 117 (check current ERG)
Isolation: ERG 117: isolate spill/leak area immediately 100m in all directions; evacuate initial 800m downwind for large spills; 1600m evacuation for fire scenarios
Chemical & Response Details
| Also known as | MethanethiolMethyl sulfhydrateThiomethyl alcoholMercaptomethaneMethyl thioalcohol |
| CAS Number | 74-93-1 |
| Appearance | Colorless gas with a strong, unpleasant odor resembling rotten cabbage or garlic at low concentrations. Highly volatile and flammable. Shipped as a liquefied compressed gas. |
| Flash Point | -47C (-53F) |
| Boiling Point | 6C (43F) |
| Vapor Density | 1.66 (heavier than air) |
| Water Reactivity | Soluble in water with no significant reaction; may hydrolyze slowly in aqueous solutions |
| Extinguishing | Water spray, fog, or regular foam; CO2 and dry chemical suitable for small fires |
| PPE | ⚠️ Level A for unknown concentrations or IDLH conditions; Level B minimum with SCBA and chemical-resistant suit; extreme skin absorption hazard |
| Isolation | ERG 117: isolate spill/leak area immediately 100m in all directions; evacuate initial 800m downwind for large spills; 1600m evacuation for fire scenarios |
Chemical details are general reference only. Always verify with current SDS, ERG, and SOP/SOG.
Common hazards (high level)
- TOXIC; Extremely Hazardous.
- May be fatal if inhaled or absorbed through skin.
- Initial odor may be irritating or foul and may deaden your sense of smell.
- Contact with gas or liquefied gas may cause burns, severe injury and/or frostbite.
- Fire will produce irritating, corrosive and/or toxic gases.
- Runoff from fire control or dilution water may cause environmental contamination.
- These materials are extremely flammable.
- May form explosive mixtures with air.
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.
- Many gases are heavier than air and will spread along the ground and collect in low or confined areas
- Ventilate closed spaces before entering, but only if properly trained and equipped.
- Isolate spill or leak area for at least 100 meters (330 feet) in all directions.
- See Table 1 - Initial Isolation and Protective Action Distances.
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UN 1064 — Methyl mercaptan HAZMAT RADIO NOTE — UN 1064
Product: Methyl mercaptan
Class 2 / Toxic Gas / ERG 117
PPE: Level A for unknown concentrations or IDLH conditions; Level B minimum with SCBA and chemical-resistant suit; extreme skin absorption hazard
ISOLATION: ERG 117: isolate spill/leak area immediately 100m in all directions; evacuate initial 800m downwind for large spills; 1600m evacuation for fire scenarios
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 1064 — Methyl mercaptan
Class: 2 | Placard: Toxic Gas | ERG Guide: 117
Appearance: Colorless gas with a strong, unpleasant odor resembling rotten cabbage or garlic at low concentrations. Highly volatile and flammable. Shipped as a liquefied compressed gas.
Water Reactivity: Soluble in water with no significant reaction; may hydrolyze slowly in aqueous solutions
Extinguishing: Water spray, fog, or regular foam; CO2 and dry chemical suitable for small fires
PPE: Level A for unknown concentrations or IDLH conditions; Level B minimum with SCBA and chemical-resistant suit; extreme skin absorption hazard
Isolation: ERG 117: isolate spill/leak area immediately 100m in all directions; evacuate initial 800m downwind for large spills; 1600m evacuation for fire scenarios
— Key Hazards —
• TOXIC; Extremely Hazardous.
• May be fatal if inhaled or absorbed through skin.
• Initial odor may be irritating or foul and may deaden your sense of smell.
— 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.
• Many gases are heavier than air and will spread along the ground and collect in low or confined areas
SOURCE: allfirefighter.com/hazmat/un/1064 | Always use current ERG + SOP/SOGIC BRIEFING
Use for: Incident command briefing, staging area whiteboard, or pre-entry team brief. Full chemical + response details.
UN1064 Methyl mercaptan Cls2 ERG117 | ERG 117: isolate spill/leak area immediately 100m in all directions; evacuate in | allfirefighter.com/hazmat/un/1064SMS / 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/1064
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FAQ
TOXIC; Extremely Hazardous. May be fatal if inhaled or absorbed through skin. Initial odor may be irritating or foul and may deaden your sense of smell. Contact with gas or liquefied gas may cause burns, severe injury and/or frostbite. Fire will produce irritating, corrosive and/or toxic gases. Runoff from fire control or dilution water may cause environmental contamination. These materials are extremely flammable. May form explosive mixtures with air.
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 A for unknown concentrations or IDLH conditions; Level B minimum with SCBA and chemical-resistant suit; extreme skin absorption hazard
No. This is a training/quick-reference aid only. Always consult the current ERG Guide 117 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.