UN/NA Number Reference
DOT Class 3 Flammable Liquid placard

UN 1229: Mesityl oxide

49 CFR 172.101 Hazardous Materials Table·ERG 2024

DOT Classification and Shipping

UN 1229 is assigned the proper shipping name Mesityl oxide in the U.S. DOT Hazardous Materials Table (49 CFR 172.101). It is classified as a Class 3 Flammable Liquid material, Packing Group III. Required label(s): 3.

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 129)

Hazards: Flammable. Irritating vapor. May cause dizziness. Toxic if inhaled or absorbed through skin.

Fire: Alcohol-resistant foam, dry chemical, CO2, water spray.

Spill: Eliminate ignition sources. Ventilate area. Absorb with earth or sand.

Chemical and Physical Properties

Mesityl oxide appears as a colorless, oily liquid with a pungent honey-like odor. Flash point 87 °F. Less dense than water and slightly soluble in water. Vapors heavier than air. Used in paint removers, as a solvent for plastics, and as an insect repellent.

CAS Number: 141-79-7
Molecular Formula: C6H10O
Molecular Weight: 98.14 g/mol
Color / Form: Oily, colorless to light-yellow liquid
Odor: ... spearmint ...
Boiling Point: 266 F
Melting Point: -51 °F (USCG, 1999)
Flash Point: 73 F
Autoignition: 652 °F (USCG, 1999)
Specific Gravity: 0.853 (floats on water)
Vapor Pressure: 9 mmHg
Vapor Density: 3.4 (heavier than air)
Water Solubility: 3 %
Log P: 1.7

Regulatory Data

OSHA PEL
25 100 15 ppm (ST) 25 ppm
NIOSH REL
TWA 10 ppm (40 mg/m 3 )
IDLH
1400 ppm [10%LEL]

Special Provisions

49 CFR 172.102 special provision codes for this entry: B1, IB3, T2, 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 1229 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.