Hazmat placards and labels both serve the purpose of communicating hazard information to people but, despite the similarities, there are some important differences between the two as well. The basic difference is this: labels provide identifying information and hazard information about a particular product whereas placards identify the class into which a hazardous material falls. Placards are primarily used in hazardous materials transportation. Labels are designed for the end user.
Placards are diamond shaped signs that are placed on each side of trucks that are hauling hazardous materials. Except in the case of small quantities, these placards are required to be displayed whenever the material in question is on board. Their main purpose is to aid those who may be responding in the event of an accident or spill. Fire department personnel, police and hazmat team members can take the information displayed on the placard and cross-reference it to the appropriate section in the Emergency Response Guidebook for guidance on appropriate spill control and safety measures. Materials that require placarding fall into one of nine classes.
Class 1, Explosives
Placards designating explosives are orange in color. Explosives are materials that are capable of producing gas at a temperature, speed and pressure that would cause damage or materials that are designed for pyrotechnic effects. There are six subcategories of explosives ranging from class 1.1, for mass explosion hazards, to 1.9 for insensitive products with no mass explosion hazard.
Class 2, Gases
These placards can be white, green, red or yellow, depending on the type of gas. The gas categories are: toxic, non-flammable, flammable and oxidizers.
Class 3, Flammable Liquids
Placards for flammable liquids are red in color and have a picture of a flame near the top corner. Combustible liquids are also in this class. Normally, a material is considered flammable if it has a flash point below 100 degrees Fahrenheit and combustible if it is below 200.
Class 4, Flammable Solids
This class also includes products that are subject to spontaneous combustion or that are water-reactive. Flammable solids placards are red and white striped. Spontaneously combustible ones are red on the bottom and white on top while blue is for water reactive substances.
Class 5, Oxidizers and Organic Peroxides
These placards are yellow with a flame on top of a circle in the upper corner of the placard.
Class 6, Toxic and Infectious Substances
White placards with black lettering are used for class 6 materials. They also have either a skull and crossbones, for toxics, or a biohazard symbol to indicate infectious materials
Class 7, Radioactive Materials
These placards are either yellow and white or all white and are used for materials affected by the Transport of Nuclear Substances regulations.
Class 8, Corrosives
A material is corrosive if it causes full thickness skin destruction or fails the ASTM corrosion test. The placards have a black bottom with a white top.
Class 9, Miscellaneous Products
Marine pollutants typically fall into this category as do materials that are shipped hot. These placards are also white with black lettering. Marine pollutants are indicated by a picture of a tree and fish. Other miscellaneous placards will have black stripes on the top half.