☣️ UN 2644 • CLASS 6
UN 2644 — Methyl iodide
Placard: Toxic. ERG Guide 151. 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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UN 2644 Quick Details
UN 2644
Product name: Methyl iodide
DOT Class: 6
Placard type: Toxic
ERG Guide: 151 (check current ERG)
Initial isolation: ERG 151: isolate spill area 50m all directions; if tank/rail car involved in fire, isolate 800m all directions
Common Hazards of UN 2644
- Highly toxic, may be fatal if inhaled, ingested or absorbed through skin.
- Avoid any skin contact.
- Fire may produce irritating, corrosive and/or toxic gases.
- Runoff from fire control or dilution water may be corrosive and/or toxic and cause environmental
- Non-combustible, substance itself does not burn but may decompose upon heating to produce corrosive
- Containers may explode when heated.
- Runoff may pollute waterways.
Chemical Identity & Physical Properties
| Also known as | IodomethaneMonoiodomethaneHalon 10001MeI |
| CAS Number | 74-88-4 |
| Appearance | Colorless to pale yellow liquid with a characteristic sweet, ether-like odor. Density greater than water. Turns brown on exposure to light. |
| Flash Point | Not applicable (non-flammable liquid) |
| Boiling Point | 42.5C (108.5F) |
| Vapor Density | 4.9 (much heavier than air) |
| Water Reactivity | Slightly soluble in water; undergoes slow hydrolysis but no vigorous reaction |
Chemical details are general reference only. Always verify with current SDS, ERG, and SOP/SOG.
Fireground Response Guidance — UN 2644
Extinguishing Media
Alcohol-resistant foam, CO2, dry chemical; water spray for cooling
PPE Requirements
⚠️ Level A or B required; full encapsulation if vapor exposure likely; SCBA mandatory; neoprene or butyl rubber gloves
Isolation & Evacuation
ERG 151: isolate spill area 50m all directions; if tank/rail car involved in fire, isolate 800m all directions
Always confirm protective actions with the current edition of the Emergency Response Guidebook (ERG Guide 151).
First Actions for a UN 2644 Incident
- CALL 911. Then call emergency response telephone number on shipping paper. If shipping paper
- Keep unauthorized personnel away.
- Stay upwind, uphill and/or upstream.
- Isolate spill or leak area in all directions for at least 50 meters (150 feet) for liquids and at least 25 meters
- For highlighted materials: see Table 1 - Initial Isolation and Protective Action Distances.
- For non-highlighted materials: increase the immediate precautionary measure distance, in the downwind
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📋 Copy & Share Field Card
UN 2644 — Methyl iodideHAZMAT RADIO NOTE — UN 2644
Product: Methyl iodide
Class 6 / Toxic / ERG 151
PPE: Level A or B required; full encapsulation if vapor exposure likely; SCBA mandatory; neoprene or butyl rubber gloves
ISOLATION: ERG 151: isolate spill area 50m 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 2644 — Methyl iodide
Class: 6 | Placard: Toxic | ERG Guide: 151
Appearance: Colorless to pale yellow liquid with a characteristic sweet, ether-like odor. Density greater than water. Turns brown on exposure to light.
Water Reactivity: Slightly soluble in water; undergoes slow hydrolysis but no vigorous reaction
Extinguishing: Alcohol-resistant foam, CO2, dry chemical; water spray for cooling
PPE: Level A or B required; full encapsulation if vapor exposure likely; SCBA mandatory; neoprene or butyl rubber gloves
Isolation: ERG 151: isolate spill area 50m all directions; if tank/rail car involved in fire, isolate 800m all directions
— Key Hazards —
• Highly toxic, may be fatal if inhaled, ingested or absorbed through skin.
• Avoid any skin contact.
• Fire may produce irritating, corrosive and/or toxic gases.
— 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.
• Isolate spill or leak area in all directions for at least 50 meters (150 feet) for liquids and at least 25 meters
SOURCE: allfirefighter.com/hazmat/un/2644 | Always use current ERG + SOP/SOGIC BRIEFING
Use for: Incident command briefing, staging area whiteboard, or pre-entry team brief. Full chemical + response details.
UN2644 Methyl iodide Cls6 ERG151 | ERG 151: isolate spill area 50m all directions; if tank/rail car involved in fir | allfirefighter.com/hazmat/un/2644SMS / 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/2644
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Frequently Asked Questions about UN 2644
Highly toxic, may be fatal if inhaled, ingested or absorbed through skin. Avoid any skin contact. Fire may produce irritating, corrosive and/or toxic gases. Runoff from fire control or dilution water may be corrosive and/or toxic and cause environmental Non-combustible, substance itself does not burn but may decompose upon heating to produce corrosive Containers may explode when heated. Runoff may pollute waterways.
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 or B required; full encapsulation if vapor exposure likely; SCBA mandatory; neoprene or butyl rubber gloves
Water reactivity: Slightly soluble in water; undergoes slow hydrolysis but no vigorous reaction. Recommended extinguishing: Alcohol-resistant foam, CO2, dry chemical; water spray for cooling.
ERG Guide 151 recommendation: ERG 151: isolate spill area 50m all directions; if tank/rail car involved in fire, isolate 800m all directions
No. This is a training/quick-reference aid only. Always consult the current ERG Guide 151 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.