UN 1591 — o-Dichlorobenzene
Placard: Toxic. ERG Guide 152. Training/quick-reference only — use current ERG + SOP/SOG for incident-specific actions.
UN 1591 is o-Dichlorobenzene, a toxic hazardous material assigned to ERG Guide 152. Responders should verify the exact product with shipping papers, package markings and SDS before close action.
Hazard overview: UN 1591 presents toxic exposure hazards by inhalation, ingestion or skin contact. Fire, decomposition or runoff may produce toxic contamination and require air monitoring, isolation and decontamination.
Response guidance: For a UN 1591 incident, responders should verify the product with shipping papers, package markings, SDS and ERG Guide 152. Establish incident command, isolate the area, stay upwind, prevent dust or vapor exposure, control runoff and choose entry or cleanup actions based on monitoring, SDS and local SOP.
Firefighter training notes: Training for UN 1591 should emphasize toxic exposure routes, air monitoring, PPE selection, decontamination and preventing contaminated runoff. Use ERG 152, SDS and local SOP.
Regulatory context: o-Dichlorobenzene is regulated as a toxic hazardous material. Transportation, workplace exposure, spill reporting, waste handling, storage and environmental requirements may vary by formulation, concentration, 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: o-Dichlorobenzene should be stored in tightly closed compatible containers in a secure toxic-material area according to SDS and local hazardous materials procedures.
UN 1591 Quick Details
Common Hazards of UN 1591
- TOXIC material; may be harmful or fatal if inhaled, ingested or absorbed through skin.
- Avoid breathing vapors, dust or mist and avoid skin or eye contact.
- Fire may produce irritating, corrosive and/or toxic gases.
- Runoff may carry toxic contamination and may pollute waterways.
- Containers may rupture or fail when heated.
- Specific toxicity and absorption risk should be confirmed from shipping papers and SDS.
Chemical Identity & Physical Properties
Clear to pale yellow liquid with a pleasant, aromatic odor similar to mothballs. Denser than water and insoluble in water.
| Also known as | 1,2-Dichlorobenzeneortho-DichlorobenzeneODCBChlorobenDowtherm E |
| CAS Number | 95-50-1 |
| Appearance | Clear to pale yellow liquid with a pleasant, aromatic odor similar to mothballs. Denser than water and insoluble in water. |
| Flash Point | 66°C (151°F) |
| Boiling Point | 180°C (356°F) |
| Vapor Density | 5.05 (heavier than air) |
| Water Reactivity | No significant reaction with water; insoluble and will sink. |
Fireground Response Guidance — UN 1591
Extinguishing Media
PPE Requirements
Use positive-pressure SCBA for dust, vapor, fire or confined-space exposure. Chemical-resistant gloves, eye/face protection and protective clothing should be selected from SDS; avoid skin contact and contaminated runoff.
Isolation & Evacuation
First Actions for a UN 1591 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 or mist and avoid all skin or eye contact.
- 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, dust, fire involvement or unknown concentration is present.
- Use ERG Guide 152, shipping papers, SDS, air monitoring and incident command for protective actions.
📋 Copy & Share Field Card
UN 1591 — o-DichlorobenzeneUse 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.