• Hazmat placards play a vital role in the transportation of hazardous materials.oxidizer class 5.1 placard image by k9dg from Fotolia.com
  
  The U.S. Department of Transportation regulates the use of hazardous materials placards--diamond-shaped labels attached to shipping containers, trucks and train cars--to identify the cargo. Placards provide information to workers about precautions required when handling the materials, and communicate the presence of potentially hazardous materials, also known as "hazmat," to first responders called to the scene of an accident.
  
  

Loads

• The use of placards depends on the type and quantity of material the company plans to ship. The USDOT maintains the Title 49 CFR 172.101 Table (List of Hazardous Materials), which notes the specific materials and the minimum quantity of each substance that will require placards. This code also describes the placards required on shipment of materials, ensuring that manufacturers and distributors use the correct type of labeling when shipping their goods.
  
  

Responsibility

• The Pipeline and Hazardous Material Safety Administration Office of Hazardous Materials Safety website notes that hazardous materials fall into one of nine categories, based on the type of danger they present. The legal responsibility for providing placards that properly identify hazardous materials lies with the producer or packager of the materials. The USDOT requires producers and packagers to provide at least four labels on each shipping container, to cover both ends and both sides of the container.
  
  

Duration

• The USDOT holds the shipper responsible for making certain that the placards remain in place during shipment. The four placards stay in place from the time the shipment leaves its point of origin until the crew unloads it at its destination. The regulations require immediate removal of placards from unloaded cargo, making it illegal to transport an empty container that displays placards.