☣️ UN 2281 • CLASS 6
UN 2281 — Hexamethylene diisocyanate
Placard: Toxic. ERG Guide 156. Training/quick-reference only — use current ERG + SOP/SOG for incident-specific actions.
🚒☣️
⚠️ 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 2281 Quick Details
UN 2281
Product name: Hexamethylene diisocyanate
DOT Class: 6
Placard type: Toxic
ERG Guide: 156 (check current ERG)
Initial isolation: ERG 156: isolate spill 25m all directions; if tank/rail car involved in fire, isolate 800m all directions and consider evacuation
Common Hazards of UN 2281
- Combustible material: may burn but does not ignite readily.
- Substance will react with water (some violently) releasing flammable, toxic or corrosive gases and runoff.
- When heated, vapors may form explosive mixtures with air: indoors, outdoors and sewers explosion
- Most vapors are heavier than air. They will spread along the ground and collect in low or confined areas
- Vapors may travel to source of ignition and flash back.
- Corrosives in contact with metals may evolve flammable hydrogen gas.
- Containers may explode when heated or if contaminated with water.
- TOXIC and/or CORROSIVE; inhalation, ingestion or contact (skin, eyes) with vapors, dusts or substance
Chemical Identity & Physical Properties
| Also known as | HDI1,6-Hexamethylene diisocyanateHexane-1,6-diisocyanate1,6-DiisocyanatohexaneDesmodur H |
| CAS Number | 822-06-0 |
| Appearance | Colorless to pale yellow liquid with a sharp, pungent odor. Viscous liquid at room temperature. |
| Flash Point | 140°C (284°F) |
| Boiling Point | 255°C (491°F) |
| Vapor Density | 6.9 (much heavier than air) |
| Water Reactivity | Reacts with water releasing carbon dioxide gas and heat, forming polyureas; reaction is exothermic but not violent |
Chemical details are general reference only. Always verify with current SDS, ERG, and SOP/SOG.
Fireground Response Guidance — UN 2281
Extinguishing Media
Dry chemical, CO2, alcohol-resistant foam; water spray for cooling only, not for extinguishment
PPE Requirements
⚠️ Level B minimum; SCBA required; full chemical-resistant suit; avoid all skin contact due to severe irritant/sensitizer properties
Isolation & Evacuation
ERG 156: isolate spill 25m all directions; if tank/rail car involved in fire, isolate 800m all directions and consider evacuation
Always confirm protective actions with the current edition of the Emergency Response Guidebook (ERG Guide 156).
First Actions for a UN 2281 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.
- Ventilate closed spaces before entering, but only if properly trained and equipped.
- 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 2281 — Hexamethylene diisocyanateHAZMAT RADIO NOTE — UN 2281
Product: Hexamethylene diisocyanate
Class 6 / Toxic / ERG 156
PPE: Level B minimum; SCBA required; full chemical-resistant suit; avoid all skin contact due to severe irritant/sensitizer properties
ISOLATION: ERG 156: isolate spill 25m all directions; if tank/rail car involved in fire, isolate 800m all directions and consider evacuation
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 2281 — Hexamethylene diisocyanate
Class: 6 | Placard: Toxic | ERG Guide: 156
Appearance: Colorless to pale yellow liquid with a sharp, pungent odor. Viscous liquid at room temperature.
Water Reactivity: Reacts with water releasing carbon dioxide gas and heat, forming polyureas; reaction is exothermic but not violent
Extinguishing: Dry chemical, CO2, alcohol-resistant foam; water spray for cooling only, not for extinguishment
PPE: Level B minimum; SCBA required; full chemical-resistant suit; avoid all skin contact due to severe irritant/sensitizer properties
Isolation: ERG 156: isolate spill 25m all directions; if tank/rail car involved in fire, isolate 800m all directions and consider evacuation
— Key Hazards —
• Combustible material: may burn but does not ignite readily.
• Substance will react with water (some violently) releasing flammable, toxic or corrosive gases and runoff.
• When heated, vapors may form explosive mixtures with air: indoors, outdoors and sewers explosion
— 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/2281 | Always use current ERG + SOP/SOGIC BRIEFING
Use for: Incident command briefing, staging area whiteboard, or pre-entry team brief. Full chemical + response details.
UN2281 Hexamethylene diisocyanate Cls6 ERG156 | allfirefighter.com/hazmat/un/2281SMS / 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/2281
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Frequently Asked Questions about UN 2281
Combustible material: may burn but does not ignite readily. Substance will react with water (some violently) releasing flammable, toxic or corrosive gases and runoff. When heated, vapors may form explosive mixtures with air: indoors, outdoors and sewers explosion Most vapors are heavier than air. They will spread along the ground and collect in low or confined areas Vapors may travel to source of ignition and flash back. Corrosives in contact with metals may evolve flammable hydrogen gas. Containers may explode when heated or if contaminated with water. TOXIC and/or CORROSIVE; inhalation, ingestion or contact (skin, eyes) with vapors, dusts or substance
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; SCBA required; full chemical-resistant suit; avoid all skin contact due to severe irritant/sensitizer properties
Water reactivity: Reacts with water releasing carbon dioxide gas and heat, forming polyureas; reaction is exothermic but not violent. Recommended extinguishing: Dry chemical, CO2, alcohol-resistant foam; water spray for cooling only, not for extinguishment.
ERG Guide 156 recommendation: ERG 156: isolate spill 25m all directions; if tank/rail car involved in fire, isolate 800m all directions and consider evacuation
No. This is a training/quick-reference aid only. Always consult the current ERG Guide 156 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.