UN 1739 — Benzyl chloroformate
Placard: Corrosive. ERG Guide 137. Training/quick-reference only — use current ERG + SOP/SOG for incident-specific actions.
UN 1739 is Benzyl chloroformate, a corrosive chloroformate liquid assigned to ERG Guide 137. It fumes in moist air and can release heat, hydrochloric acid fumes and carbon dioxide when exposed to water.
Hazard overview: UN 1739 presents corrosive fume, water-reaction, toxic vapor and combustible liquid hazards. Avoid direct water contact and control runoff under incident command.
Response guidance: For a UN 1739 incident, responders should verify the product with shipping papers, package markings, SDS and ERG Guide 137. Establish incident command, isolate the area, stay upwind, prevent incompatible contact, control runoff and choose entry or fire-control actions based on monitoring, SDS and local SOP.
Firefighter training notes: Training for UN 1739 should emphasize toxic/corrosive exposure routes, water or oxidizer incompatibility where applicable, air monitoring, PPE selection, decontamination and runoff containment. Use ERG 137, SDS and local SOP.
Regulatory context: Benzyl chloroformate is regulated as a hazardous material for transportation and emergency response purposes. Transportation, workplace exposure, spill reporting, waste handling, storage and environmental requirements may vary by concentration, formulation, quantity and jurisdiction. Verify current requirements through shipping papers, SDS, facility documents and applicable DOT, OSHA, EPA, NFPA, state or local authority guidance.
Storage & handling: Benzyl chloroformate should be stored in tightly closed compatible containers in a cool, dry, well-ventilated area away from water, moisture, bases, oxidizers/reducing agents where incompatible, heat and unauthorized access. Protect containers from corrosion, leakage and contamination.
UN 1739 Quick Details
Common Hazards of UN 1739
- TOXIC and CORROSIVE chloroformate liquid; inhalation, ingestion or skin/eye contact may cause severe injury.
- Reacts with water or moisture, generating heat, hydrochloric acid fumes and carbon dioxide.
- Vapors are heavier than air and may collect in low or confined areas.
- Combustible liquid: may burn under fire conditions.
- Fire may produce irritating, corrosive and/or toxic gases.
- Runoff may spread corrosive and toxic contamination.
- Containers may rupture or fail when heated.
Chemical Identity & Physical Properties
Colorless to pale yellow liquid with a pungent, irritating odor. Fuming in moist air. Corrosive to metals and tissues.
| Also known as | Benzyl chlorocarbonateCarbobenzoxy chlorideChloroformic acid benzyl esterBenzyloxycarbonyl chloride |
| CAS Number | 501-53-1 |
| Appearance | Colorless to pale yellow liquid with a pungent, irritating odor. Fuming in moist air. Corrosive to metals and tissues. |
| Flash Point | 100°C (212°F) |
| Boiling Point | 103°C (217°F) |
| Vapor Density | 5.9 (heavier than air) |
| Water Reactivity | Reacts with water to produce hydrochloric acid and carbon dioxide with heat generation. Reaction increases corrosive vapor concentration. |
Fireground Response Guidance — UN 1739
Extinguishing Media
PPE Requirements
Use positive-pressure SCBA for vapor, fume, dust, fire or confined-space exposure. Chemical-resistant gloves, boots, eye/face protection and protective clothing should be selected from SDS; Level A may be needed for close entry or unknown concentrations.
Isolation & Evacuation
First Actions for a UN 1739 Incident
- CALL 911. Then call the emergency response telephone number on the shipping paper, if available.
- Keep unauthorized personnel away.
- Stay upwind, uphill and/or upstream.
- Avoid breathing vapors, fumes, dust, mist or gas and avoid skin or eye contact.
- Keep water and moisture away from released product unless incident command confirms a compatible cooling or control use.
- Do not touch or walk through spilled material unless properly trained and wearing appropriate protective equipment.
- Ventilate closed spaces before entering, but only if properly trained, equipped, monitored and authorized by incident command.
- Isolate the spill or leak area and expand the perimeter if vapor, gas, dust, fire involvement, water reaction or unknown concentration is present.
- Use ERG Guide 137, shipping papers, SDS, air monitoring and incident command for protective actions.
📋 Copy & Share Field Card
UN 1739 — Benzyl chloroformateUse for: Quick radio or face-to-face size-up. Short, structured, field-ready.
Use for: Incident command briefing, staging area whiteboard, or pre-entry team brief.
Use for: Quick text to command or incoming units. Fits in a single SMS.