☣️ UN 2644 • CLASS 6
Methyl iodide
Placard: Toxic. 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 2644
Class: 6
Placard type: Toxic
ERG: Guide 151 (check current ERG)
Isolation: ERG 151: isolate spill area 50m all directions; if tank/rail car involved in fire, isolate 800m all directions
Chemical & Response Details
| 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 |
| 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 |
Chemical details are general reference only. Always verify with current SDS, ERG, and SOP/SOG.
Common hazards (high level)
- 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.
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.
- 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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UN 2644 — Methyl iodide HAZMAT 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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FAQ
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
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.