Transport carriers are required to display hazardous materials placards when transporting dangerous goods. The U.S. Department of Transportation's hazardous materials placard guidelines are aligned with international, interstate and local standards. These placards provide critical information to transport workers, first responders and any subsequent emergency response teams.
The shipper is responsible for identifying the hazardous material. The carrier uses the shipper’s information to place the appropriate placard on the transport vehicle or container. If the cargo is hazardous, DOT requires the carrier to mount a placard on the container identifying the appropriate hazardous response class: 1 - explosives, 2 - gases, 3 - flammable and combustible liquids, 4 - flammable solids, such as spontaneously combustible materials and dangerous when wet materials, 5 - oxidizers and organic peroxides, 6 - toxic material and infectious substances, 7 - radioactive materials, 8 - corrosive materials and 9 - miscellaneous dangerous goods.
Divisions and Identification Numbers
Some hazard classes include subdivisions, which allow the grouping of hazardous materials within the same class. For instance, gases in general are class 2. The division identifier for a flammable gas is 2.1, and the division identifier for a poisonous gas is 2.3. The more precisely a shipper identifies a hazardous material, the more accurately the placard can communicate the nature of the hazard to first and subsequent responders. The identification number is displayed on the hazardous material placard or on an accompanying orange sign with black lettering.
Hazardous material placards are square signs that are printed and positioned to stand on-point. The detailed guidelines contain instructions on the proper placement, background color, text and coding, and contain two placarding tables that list the hazard classes according to general handling instructions. Table 1 hazards require a placard when transporting any amount of the listed materials. The materials that are listed in Table 2 require a placard if the amount exceeds 1,001 lbs.
The DOT allows some exceptions to the guidelines. For instance, a carrier may disregard placarding requirements for containers that may only contain the residue of a non-bulk Table 2 hazardous material. In addition, a modification that's more of a clarification allows a carrier transporting multiple divisions of an explosive material to display a placard showing only the lowest class 1 division number placard.