☣️ UN 1064 • CLASS 2

UN 1064 — Methyl mercaptan

Placard: Toxic Gas. ERG Guide 117. 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.

Methyl mercaptan is a highly toxic and extremely hazardous substance that can be fatal if inhaled or absorbed through the skin. It is shipped as a liquefied compressed gas.

Hazard overview: Methyl mercaptan is highly toxic and can cause serious health effects, including respiratory problems and damage to the central nervous system. The gas is also highly volatile and flammable.

Response guidance: In the event of a spill or leak, isolate the area immediately and evacuate downwind. Responders should wear Level A protective gear, including a self-contained breathing apparatus and a chemical-resistant suit.

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UN 1064 Quick Details

UN 1064
Product name: Methyl mercaptan
DOT Class: 2
Placard type: Toxic Gas
ERG Guide: 117 (check current ERG)
Initial isolation: ERG 117: isolate spill/leak area immediately 100m in all directions; evacuate initial 800m downwind for large spills; 1600m evacuation for fire scenarios

Common Hazards of UN 1064

  • 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.

Chemical Identity & Physical Properties

Methyl mercaptan is a colorless gas with a strong, unpleasant odor resembling rotten cabbage or garlic at low concentrations.

Also known asMethanethiolMethyl sulfhydrateThiomethyl alcoholMercaptomethaneMethyl thioalcohol
CAS Number74-93-1
AppearanceColorless 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 Point6C (43F)
Vapor Density1.66 (heavier than air)
Water ReactivitySoluble in water with no significant reaction; may hydrolyze slowly in aqueous solutions
Chemical details are general reference only. Always verify with current SDS, ERG, and SOP/SOG.

Fireground Response Guidance — UN 1064

Extinguishing Media

Water spray, fog, or regular foam; CO2 and dry chemical suitable for small fires

PPE Requirements

⚠️ Level A for unknown concentrations or IDLH conditions; Level B minimum with SCBA and chemical-resistant suit; extreme skin absorption hazard

Level A protective gear is required for unknown concentrations or IDLH conditions, including a self-contained breathing apparatus and a chemical-resistant suit, due to the extreme skin absorption hazard.

Isolation & Evacuation

ERG 117: isolate spill/leak area immediately 100m in all directions; evacuate initial 800m downwind for large spills; 1600m evacuation for fire scenarios
Always confirm protective actions with the current edition of the Emergency Response Guidebook (ERG Guide 117).

First Actions for a UN 1064 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 100 meters (330 feet) in all directions.
  • See Table 1 - Initial Isolation and Protective Action Distances.
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📋 Copy & Share Field Card

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.

SMS WhatsApp
=== 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 — • 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 100 meters (330 feet) in all directions. 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.

SMS (short)
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.

⚠️ Quick-reference only. Always use current ERG + SOP/SOG for incident-specific actions. Page: https://allfirefighter.com/hazmat/un/methyl-mercaptan-un-1064

Related UN Numbers in Class 2

Discovery block for training / quick reference. Always consult the current ERG + your SOP/SOG for operations.
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Frequently Asked Questions about UN 1064

Yes, UN 1064 is a highly volatile and flammable gas.

Methyl mercaptan can cause serious health effects, including respiratory problems and damage to the central nervous system.

Isolate the area immediately, evacuate downwind, and wear Level A protective gear, including a self-contained breathing apparatus and a chemical-resistant suit.
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.