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First responders should become familiar with the U.S. Department of Transportation (DOT) hazard classes for hazardous materials and the placards and labels used to identify those hazards. This information will assist them when they use the Emergency Response Guide (ERG).
The DOT identifies nine hazard classes. Each class has a particular color associated with its placard and label. Placards and labels are diamond shaped. The placard is the largest and is used on the exterior of transportation vehicles and certain large containers. Labels are much smaller and found on the individual packages and small containers of hazardous materials.
Photo by Robert Burke
The U.S. Department of Transportation (DOT) requires placarding of hazardous materials. The placards on these portable canisters indicate that they contain chlorine.
Also located on each placard and label is the hazard class number. This number is located on the bottom corner of the diamond. A symbol is found in the top corner of the diamond, and on most of the placards and labels a hazard class name is located in the center.
DOT regulations also permit the use of wordless placards, which are used throughout the rest of the world. Wordless placards do not have the hazard class name in the center of the placard, so responders should become familiar with the colors of placards and labels and the hazard class associated with each color.
Many times, the nature of hazmat incidents prevent emergency personnel from getting close enough to read what is written on the placards. However, the color of the placard can be identified from a safe distance or through binoculars. By associating the color of the placard or label with the hazard class, a responder can identify the hazard even if nothing is written on the placard.
Hazardous materials transported by rail, highways and waterways may be found with placards or labels. Usually, air shipments present a limited hazard, are in small packages and will be labeled. Pipelines are also a type of transportation system for shipping hazardous materials. Pipelines aren't placarded or labeled, but locations are marked with aboveground signs that identify the product and the pipeline company and provide emergency contact information.
Orange placards indicate explosives, DOT Class 1. The DOT identifies six subclasses of explosives. While these subclasses are identified by certain explosive characteristics, it is important that response personnel do not relate any of the classes with a lesser hazard than another. Responders may not know if the circumstances are present for an explosive to behave in a certain way. Therefore, all explosive classes should be treated as the worst case, that being detonation, until explosives experts arrive on scene.
Photo by Robert Burke
NFPA 704 placards at a compressed gas facility.
Red placards indicate flammables and may be found in Class 2 (compressed gases with a flammability hazard) and Class 3 (flammable liquids). Flammable gases include propane, hydrogen and butane. Flammable liquids include gasoline, acetone, alcohols and ketones.
When response personnel recognize that a flammable hazard exists, they should take every precaution to prevent ignition of the material. Ignition sources include open flames, smoking, welding and other hot operations, heat from friction, radiant heat, static electrical charges, electrical sources, mechanical sparks and spontaneous ignition. Fire apparatus can be a source of ignition and should be positioned properly.
Compressed gases are a hazard class because of the pressure in the containers, which presents a hazard in addition to the physical and chemical characteristics of the gases. A green placard also indicates a compressed gas that is considered by DOT to be non-flammable. This can be dangerously deceiving, because anhydrous ammonia is placarded as a non-flammable compressed gas when, in fact, it will burn under certain conditions, usually inside a building or in a confined space. This is because the DOT definition of a flammable gas does not fit the flammable range of anhydrous ammonia. Other non-flammable gases include carbon dioxide, nitrogen, and argon. There is also a white compressed gas placard for poisons. Poison gases include chlorine and phosgene.