US DOT Hazardous Materials Regulations (49 CFR Parts 171 to 180) 172.500-560: Placarding: offeror provides and carrier affixes placards on bulk packagings, freight containers, transport vehicles and rail cars; Tables 1 and 2; the 1,001 pound threshold and DANGEROUS placard (172.500 to 172.560)

Whoever offers a hazardous material for transportation supplies the placards required by 172.504, and the carrier must affix and maintain them on each bulk packaging, freight container, unit load device, transport vehicle and rail car containing the material, on each side and each end, visible and in the 172.519 specifications, with the identification number displayed on placards for bulk packagings and certain quantities. Table 1 materials (explosives 1.1 to 1.3, poison gas, dangerous when wet, organic peroxide type B, poison inhalation hazard, radioactive Yellow-III) are placarded for any quantity; Table 2 materials are placarded when the aggregate gross weight is 1,001 pounds or more, with the DANGEROUS placard permitted for mixed loads subject to the 2,205 pound single-class limit. Special rules apply to rail (172.510), freight containers and aircraft unit load devices (172.512), portable tanks (172.514) and to prohibited and permissive placarding (172.502).