☣️ 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.
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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.
n-Butyl chloroformate is a flammable toxic chloroformate with corrosive vapor and liquid hazards. Keep water away from spilled product.
Hazard overview: It presents a combined flammable vapor, toxic inhalation and corrosive-contact hazard. Moisture can release acidic fumes and pressure.
Response guidance: Isolate the area, shut off ignition sources and prevent sewer entry. Use dry chemical, CO2 or alcohol-resistant foam; cool intact containers with water spray from a protected distance.
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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
- n-Butyl chloroformate is flammable, toxic and corrosive.
- Vapors may form explosive mixtures with air and flash back from low areas.
- Water or moisture can decompose the liquid, releasing HCl, carbon dioxide and heat.
- Liquid and vapor can burn eyes, skin and respiratory tissue.
- Closed or contaminated containers may pressurize and rupture.
- Fire can produce hydrogen chloride and carbonyl chloride-type toxic gases.
- Runoff may be acidic, toxic and flammable.
Chemical Identity & Physical Properties
Colorless to pale yellow liquid with a pungent, irritating odor. Liquid at room temperature
| 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
Use SCBA with acid-resistant chemical protective clothing, gloves and face protection; consider Level A for unknown vapor levels or large spills.
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 and the emergency response number shown on the shipping papers.
- Keep unauthorized personnel away and deny entry to the spill or fire area.
- Stay upwind, uphill and upstream; avoid low areas where vapors or runoff may collect.
- Avoid breathing dust, vapor, mist or smoke; prevent skin and eye contact.
- Do not touch damaged containers or spilled material without appropriate PPE.
- Ventilate confined spaces only if personnel are trained, equipped and monitored.
- Use the ERG, SDS, shipping papers and air monitoring to set isolation, PPE and tactical decisions.
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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 —
• n-Butyl chloroformate is flammable, toxic and corrosive.
• Vapors may form explosive mixtures with air and flash back from low areas.
• Water or moisture can decompose the liquid, releasing HCl, carbon dioxide and heat.
— First Actions —
• Call 911 and the emergency response number shown on the shipping papers.
• Keep unauthorized personnel away and deny entry to the spill or fire area.
• Stay upwind, uphill and upstream; avoid low areas where vapors or runoff may collect.
• Avoid breathing dust, vapor, mist or smoke; prevent skin and eye contact.
SOURCE: allfirefighter.com/hazmat/un/n-butyl-chloroformate-un-2743 | Always use current ERG + SOP/SOGIC BRIEFING
Use for: Incident command briefing, staging area whiteboard, or pre-entry team brief.
UN2743 n-Butyl chloroformate Cls6 ERG155 | allfirefighter.com/hazmat/un/n-butyl-chloroformate-un-2743SMS / 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/n-butyl-chloroformate-un-2743
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Frequently Asked Questions about UN 2743
UN 2743 is n-Butyl chloroformate, regulated as a hazardous material for transport and emergency response.
The main concern is a hazardous material behavior plus exposure risk from dust, vapor, liquid or fire products.
Approach from upwind, isolate the area, keep nonessential people out and verify the exact product with shipping papers or SDS.
Do not apply water directly to spilled liquid; moisture can produce HCl, heat and carbon dioxide pressure.
Use SCBA with acid-resistant chemical protective clothing, gloves and face protection; consider Level A for unknown vapor levels or large spills.
Fire may involve flashback and toxic HCl or carbonyl chloride-type decomposition gases.
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.