☣️ UN 2743 • CLASS 6
UN 2743 — n-Butyl chloroformate
Placard: Toxic. ERG Guide 155. 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 2743 Quick Details
UN 2743
Product name: n-Butyl chloroformate
DOT Class: 6
Placard type: Toxic
ERG Guide: 155 (check current ERG)
Initial isolation: ERG 155: isolate spill or leak area immediately for at least 50 meters in all directions; if tank/rail car involved in fire, isolate 800 meters in all directions
Common Hazards of UN 2743
- HIGHLY FLAMMABLE: Will be easily ignited by heat, sparks or flames.
- Vapors form explosive mixtures with air: indoors, outdoors and sewers explosion hazards.
- 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.
- Those substances designated with a (P) may polymerize explosively when heated or involved in a fire.
- Substance will react with water (some violently) releasing flammable, toxic or corrosive gases and runoff.
- Corrosives in contact with metals may evolve flammable hydrogen gas.
- Containers may explode when heated or if contaminated with water.
Chemical Identity & Physical Properties
| Also known as | n-Butyl chlorocarbonateButyl chloroformateChloroformic acid butyl esterFormic acid chloro-, butyl ester |
| CAS Number | 592-34-7 |
| Appearance | Colorless to pale yellow liquid with a pungent, irritating odor. Liquid at room temperature. |
| Flash Point | 29°C (84°F) |
| Boiling Point | 142°C (288°F) |
| Vapor Density | 4.7 (heavier than air) |
| Water Reactivity | Reacts with water releasing toxic and corrosive hydrogen chloride gas; avoid water contact |
Chemical details are general reference only. Always verify with current SDS, ERG, and SOP/SOG.
Fireground Response Guidance — UN 2743
Extinguishing Media
Dry chemical, CO2, or alcohol-resistant foam; avoid direct water spray on liquid
PPE Requirements
⚠️ Level B minimum; SCBA required; full chemical-resistant suit; material is toxic and corrosive
Isolation & Evacuation
ERG 155: isolate spill or leak area immediately for at least 50 meters in all directions; if tank/rail car involved in fire, isolate 800 meters in all directions
Always confirm protective actions with the current edition of the Emergency Response Guidebook (ERG Guide 155).
First Actions for a UN 2743 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 2743 — n-Butyl chloroformateHAZMAT RADIO NOTE — UN 2743
Product: n-Butyl chloroformate
Class 6 / Toxic / ERG 155
PPE: Level B minimum; SCBA required; full chemical-resistant suit; material is toxic and corrosive
ISOLATION: ERG 155: isolate spill or leak area immediately for at least 50 meters in all directions; if tank/rail car involved in fire, isolate 800 meters in 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 2743 — n-Butyl chloroformate
Class: 6 | Placard: Toxic | ERG Guide: 155
Appearance: Colorless to pale yellow liquid with a pungent, irritating odor. Liquid at room temperature.
Water Reactivity: Reacts with water releasing toxic and corrosive hydrogen chloride gas; avoid water contact
Extinguishing: Dry chemical, CO2, or alcohol-resistant foam; avoid direct water spray on liquid
PPE: Level B minimum; SCBA required; full chemical-resistant suit; material is toxic and corrosive
Isolation: ERG 155: isolate spill or leak area immediately for at least 50 meters in all directions; if tank/rail car involved in fire, isolate 800 meters in all directions
— Key Hazards —
• HIGHLY FLAMMABLE: Will be easily ignited by heat, sparks or flames.
• Vapors form explosive mixtures with air: indoors, outdoors and sewers explosion hazards.
• Most vapors are heavier than air. They will spread along the ground and collect in low or confined areas
— 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/2743 | Always use current ERG + SOP/SOGIC BRIEFING
Use for: Incident command briefing, staging area whiteboard, or pre-entry team brief. Full chemical + response details.
UN2743 n-Butyl chloroformate Cls6 ERG155 | ERG 155: isolate spill or leak area immediately for at least 50 meters in all di | allfirefighter.com/hazmat/un/2743SMS / 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/2743
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Frequently Asked Questions about UN 2743
HIGHLY FLAMMABLE: Will be easily ignited by heat, sparks or flames. Vapors form explosive mixtures with air: indoors, outdoors and sewers explosion hazards. 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. Those substances designated with a (P) may polymerize explosively when heated or involved in a fire. Substance will react with water (some violently) releasing flammable, toxic or corrosive gases and runoff. Corrosives in contact with metals may evolve flammable hydrogen gas. Containers may explode when heated or if contaminated with water.
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; material is toxic and corrosive
Water reactivity: Reacts with water releasing toxic and corrosive hydrogen chloride gas; avoid water contact. Recommended extinguishing: Dry chemical, CO2, or alcohol-resistant foam; avoid direct water spray on liquid.
ERG Guide 155 recommendation: ERG 155: isolate spill or leak area immediately for at least 50 meters in all directions; if tank/rail car involved in fire, isolate 800 meters in all directions
No. This is a training/quick-reference aid only. Always consult the current ERG Guide 155 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.