Publication 52, Hazardous, Restricted, and Perishable Mail > 3 Hazardous Materials > 32 General
The U.S. Department of Transportation (DOT) is the federal agency responsible for regulating the carriage of hazardous materials within the United States via any mode of transportation (e.g., highway, rail, air, water). The federal regulations of the DOT are codified in Title 49 Code of Federal Regulations (49 CFR), which contains the DOT’s detailed specifications for packaging, marking, and labeling hazardous materials. Title 49 CFR also exempts or establishes other requirements for limited quantities and small quantities of hazardous materials. USPS mailing standards for hazardous materials generally adhere to 49 CFR, but also include many additional limitations and prohibitions.