UN/NA Number Reference
DOT Class 6.1 Toxic Substance placard

UN 1591: o-Dichlorobenzene

49 CFR 172.101 Hazardous Materials Table·ERG 2024

DOT Classification and Shipping

UN 1591 is assigned the proper shipping name o-Dichlorobenzene in the U.S. DOT Hazardous Materials Table (49 CFR 172.101). It is classified as a Class 6.1 Toxic Substance material, Packing Group III. Required label(s): 6.1.

Packing group indicates the degree of danger within a hazard class: PG I is high danger, PG II medium, PG III low. The proper shipping name, hazard class, UN number, and packing group together form the basic shipping description that must appear on shipping papers and, where required, on the package and placard.

Emergency Response (ERG Guide 152)

Hazards: TOXIC. Combustible. May be ignited by heat, sparks. Toxic fumes when burned.

Fire: Small: dry chemical, CO2, water spray. Large: water spray, fog.

Spill: Do not touch. Eliminate ignition sources. Ventilate area. Use water spray.

Chemical and Physical Properties

O-dichlorobenzene appears as a clear colorless liquid with a pleasant odor. Denser than water and insoluble in water. Flash point 150 °F. Toxic by inhalation and ingestion. Used to make other chemicals, solvents, fumigants and insecticides and for many other uses.

CAS Number: 95-50-1
Molecular Formula: C6H4Cl2
Molecular Weight: 147.00 g/mol
Color / Form: Colorless liquid
Odor: Pleasant odor
Boiling Point: 356.9 F
Melting Point: 1 °F (NTP, 1992)
Flash Point: 151 F
Autoignition: 1198 °F (USCG, 1999)
Specific Gravity: 1.306 (sinks in water)
Vapor Pressure: 1 mmHg at 68 F
Vapor Density: 5.05 (heavier than air)
Water Solubility: less than 1 mg/mL at 76.1 F
Log P: log Kow = 3.43

Regulatory Data

CERCLA RQ (40 CFR 302.4)
100 lb
OSHA PEL
(C) 50 (C) 300 25 ppm (C) 50 ppm
NIOSH REL
C 50 ppm (300 mg/m 3 )
IDLH
200 ppm
RCRA Waste Code(s)
[object Object]

A release of this material at or above its CERCLA reportable quantity (100 lb) requires immediate notification to the National Response Center at 800-424-8802.

Special Provisions

49 CFR 172.102 special provision codes for this entry: IB3, T4, TP1. These codes modify the general requirements (packaging, quantity limits, exceptions) for this specific material. Look up each code in 49 CFR 172.102 for the full text.

Need the full interactive record? Open UN 1591 in the SpillNerd lookup tool for the live database entry with placard graphics, GHS pictograms, full segregation tables, and synonym search. For another material, use the UN number and chemical lookup.

Reference data compiled from the DOT Hazardous Materials Table (49 CFR 172.101), the 2024 Emergency Response Guidebook, and public chemical databases (PubChem, NIOSH, EPA). Always verify the correct shipping description against the current regulation and the manufacturer's SDS Section 14 before shipping.