Question To determine which placard(s) you must use when carrying hazardous materials, you need to know: Answers The hazard classes of the materials. The types of containers being used. The destination. The shipper. Explanation Hazardous materials placards are placed on the outside of a vehicle to identify the hazard classes of materials being carried. This questions appears in the following tests: District Of Columbia HazMat Massachusetts HazMat Massachusetts HazMat Nebraska HazMat Oregon HazMat West Virginia HazMat West Virginia HazMat Wyoming HazMat