For the most part, hazardous waste placards are incomprehensible. They might occasionally make sense to you – you’ll see a little flame and be able to recognize a flammability warning – but those moments of clarity seem to be few and far between. Everyone in North America could surely benefit from the ability to decipher these placards, but no party would benefit more than our nation’s firefighters.

The United States (DOT 49 CFR), Canadian (TDG), and international regulations require that some materials and substances be correctly identified during transport. These diamond-shaped placards serve an important purpose; they warn anyone (including emergency responders) that might handle or approach the hazardous materials of the associated dangers and indicates the necessity of caution. In other words, these bizarre hieroglyphics help keep people safe.

To do this, the placard presents the approaching person with a myriad of information. When you know how to read a placard, it makes sense. The first – and most obvious – piece of information is provided by color. For example:

  • Red placards indicate the material is flammable;
  • Green placards indicate the material is non-flammable;
  • Yellow placards indicate the material is an oxidizer;
  • Blue placards indicate the material is dangerous when wet;
  • White placards indicate the material is an inhalation hazard and/or poison;
  • Black and white placards indicate the material is corrosive;
  • Red and white placards indicate the material is a flammable solid or spontaneously combustible (it depends on the color pattern);
  • White and yellow placards indicate the material is radioactive;
  • Orange placards indicate the material is explosive;
  • White placards with black stripes indicate miscellaneous hazardous materials.

(There is also another red and white placard that simply states “Dangerous” on it.) The next piece of information you should look for is a number in the bottom corner of the diamond. This number refers to the hazard classes used by the United States Department of Transportation (DOT), as well as those used internationally. (For more information on placarding rules in the United States, check out Subpart F of Part 172, in Title 49 of the Code of Federal Regulations.) These hazard classes are:

  • Class 1 Explosives;
  • Class 2 Gases (flammable, nonflammable, oxygen, inhalation hazard, poison);
  • Class 3 Liquids (flammable and combustible liquids);
  • Class 4 Flammable Solids, Spontaneously Combustible, or Dangerous When Wet Materials;
  • Class 5 Oxidizers and Organic Peroxides;
  • Class 6 Poison/Toxic Solids and Liquids, or Infectious Materials;
  • Class 7 Radioactive Materials;
  • Class 8 Corrosives (acids and bases);
  • Class 9 Miscellaneous.

Next, look for a symbol in the upper corner. Placards can feature a variety of different symbols to warn of the possibility of an explosion, combustion, destruction of materials and skin by corrosives, radiation, oxidizers, compressed gas, or poison.

The last piece of information made readily available by these placards can come in two forms: a four-digit United Nations (UN) number used to describe the hazardous material (such as 1001 for acetylene) or, more simply, the name of the substance.

Hazardous material placards seem incomprehensible at first glance – nothing more than a jumbled mix of symbols, colors, patterns and numbers. But if you familiarize yourself with this guide and learn to see the information hidden within, you’ll be in a much better position to keep yourself and those that you work with protected at all times.

Remember – you don’t need to be a firefighter to know this information, but you certainly need to know this information if you’re a firefighter or emergency responder.

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