At ArcBest, we are monitoring the evolving situation with the coronavirus (COVID-19) and its potential impact on our customers’ supply chains. Read More.

Understanding HAZMAT Placards

Posted by Sam Cates on June 7, 2017 - 8:03 AM
Info about HAZMAT placards

What HAZMAT placards can tell you about a shipment

Have you ever noticed diamond-shaped signs on the back or sides of a semi-truck trailer and wondered what they were or why they were there? These colorful labels are known as hazardous material placards, or HAZMAT placards, and they provide details about what kind of cargo the truck is carrying. The United States Department of Transportation (DOT) requires these HAZMAT signs when moving more than 1,000 pounds of hazardous cargo within the U.S. and on some hazardous commodities regardless of weight. If you’re curious about what each of these HAZMAT symbols mean, or if you’re a shipper and need help deciding which placard is right for your shipment, use this hazardous material guide to learn more.  

Types of DOT placards

Hazardous materials include, but aren’t limited to explosives, flammable and combustible liquids, and poisons. Due to the potential risks and consequences involved with these materials, they’re strictly monitored by carriers, the DOT and emergency personnel while in transit to ensure the safety of the public. HAZMAT placarding helps with these efforts because it allows substances to be quickly identified in case of emergency. Safety protocols are in place for each type of material.

Because hazardous freight is divided into nine classes, there are nine main types of placards. Here’s what each of those look like and what they mean:

  1. Hazard Class 1: Class 1 hazards are explosives or any devices or chemicals that are designed to explode or combust. Class 1 explosives are illustrated by an orange placard with their designated hazard class, division number or compatibility letter displayed at the bottom. Some also feature an explosion graphic. There are six different classifications in the explosive class, marked by a sub class number of 1.1 through 1.6, to indicate the type of hazard. Class 1 hazardous materials also have compatibility letters, marked A-S, to help signify what other products are safe to travel with them.
The six Class 1 sub classifications are:
  • Class 1.1: Products with a potential to create a mass explosion.
  • Class 1.2: Products with a potential to create a projectile hazard.
  • Class 1.3: Products with a potential to create a fire or minor blast.
  • Class 1.4: Products with no significant risk of creating a blast or hazard.
  • Class 1.5: Products considered very insensitive, that are used as blasting agents.
  • Class 1.6: Products considered extremely insensitive, with no risk to create a mass explosion.


  1. Hazard Class 2: Class 2 hazards are compressed gases, which are divided into four categories: flammable/combustible gases, non-flammable/non-poisonous gases, toxic/poisonous gases, and oxygen.
The four Class 2 placards are:
  • A red sign, with a flame graphic on the top portion and the hazard class No. 2 displayed at the bottom. “Flammable gas” is sometimes spelled out. Flammable gases include ethyl chloride and liquefied petroleum gases.
  • A green sign, with “non-flammable gas” displayed in the middle. The hazard class No. 2 is noted at the bottom and a graphic of a gas canister is at the top. Non-flammable/poisonous gases include carbon dioxide, compressed helium, nitrogen and helium.
  • A white sign, with a skull and crossbones graphic in place at the top, with the hazard class No. 2 at the bottom. Some of these will have the words “inhalation hazard” or “toxic gas” displayed in the middle. Toxic or poisonous gases include sulfur dioxide, bromine chloride, carbon monoxide and chlorine.
  • A yellow sign, with the hazard class No. 2 at the bottom. The word “oxygen” is written across the center of with an oxygen graphic displayed above it.


  1. Hazard Class 3: Class 3 hazards are flammable liquids. These liquids include paints, alcohols, gasoline, kerosene and ethanol, and are recognized by red “flammable liquids” placards with the hazard class No. 3 at the bottom, and a flammable liquid graphic at the top.


  1. Hazard Class 4: Class 4 hazards are flammable solids. There are three divisions in this class, including flammable solids, spontaneously combustible materials and substances that are dangerous when wet, or water-reactive.
Those divisions are illustrated as follows:
  • The flammable solid placard is a red-and-white diagonal-striped placard with a flammable graphic in the top portion and the hazard class No. 4 at the bottom.
  • Spontaneously combustible solids are recognized by signage that is half-white and half-red, with the colors divided horizontally. The hazard class No. 4 is designated at the bottom, with a flammable graphic in the top portion.
  • Water-reactive substances get a solid blue truck placard, with the hazard class No. 4 at the bottom and the flammable graphic adorned at the top.  


  1. Hazard Class 5: Class 5 hazards are oxidizing chemicals that could be prone to combustion. There are two divisions to this class — oxidizers and organic peroxides — marked as 5.1 and 5.2, respectively. Oxidizers are designated with a yellow label, with the hazard class number 5.1 at the bottom and the oxygen logo at the top. Organic peroxides are noted with a half-red and half-yellow truck placard, with a flammable graphic at the top in the red portion. The hazard class No. 5.2 is located at the bottom.


  1. Hazard Class 6: Class 6 hazards are poisonous materials. These substances are divided into two classes: poisonous substances and biohazardous substances, and are designated by 6.1 and 6.2, respectively.
Here’s what those placards look like:
  • Poisonous substances are identified by a white, poison placard with a skull and crossbones graphic at the top and the hazard class No. 6 at the bottom. These include aerosols, ammonium fluoride, mercury-based pesticides and phenol.
  • Biohazardous substances have white signs with a biohazard logo at the top and the hazard class No. 6 at the bottom. The class includes biological substances, regulated medical waste or virus cultures.


  1. Hazard Class 7: Class 7 hazards are substances or materials that are radioactive. Radioactive substances are recognized by yellow and white HAZMAT signs, with a radioactive logo in the top, yellow portion and the hazard class No. 7 at the bottom, on the white portion.


  1. Hazard Class 8: Class 8 hazards are corrosive substances, including hydrochloric acid, potassium hydroxide and sodium hydroxide. These DOT placards are half-white and half-black, with a corrosive liquid graphic in the white upper portion, and the hazard class No. 8 on the black, lower portion.  


  1. Hazard Class 9: Class 9 hazards are classified as miscellaneous dangerous goods, which include lithium batteries, asbestos, dry ice and other consumer commodities. These products are identified by a half-white and half-black-and-white-striped sign, with the hazard class No. 9 located on the bottom, white portion.

Some vehicles will feature a red “dangerous” transportation placard, indicating that they are transporting freight from multiple hazard classes.


What do the HAZMAT UN/NA numbers mean?

Some of these DOT placards have four-digit numbers in the middle. These numbers, usually ranging from 0004-3534, are called United Nations (U.N.) numbers, and are assigned by the U.N. to help identify hazardous international cargo, or the specific class of hazardous international cargo that is traveling in the U.S.

Some hazardous chemicals have specific HAZMAT U.N. numbers, like chlorine, which is designated as U.N. 3520, while other hazardous materials have a more common designation. Flammable liquids, for example, are designated with a U.N. 1203 placard, while combustible liquids are assigned the U.N. 1993 placard.

Some materials that aren’t classified or regulated by the U.N. will receive North American (NA) numbers. These numbers are four-digit numbers that range from 8000-9279 and are assigned by the DOT. All UN/NA labels come with a hazard identifier that determines the cargo’s hazard class, sub class and compatibility group.

How many HAZMAT placards are needed?

Most carriers equip their vehicles with at least four placards, in accordance with DOT requirements. The DOT requires carriers that move hazardous materials to have at least four of these placards, so that there is visibility from the front, back and both sides of the vehicle. Some carriers require their drivers to use six placards, to include visibility on either side of the truck cab. Trucks moving HAZMAT cargo through California are required to have an additional card on the front of the trailer, per state guidelines.

According to DOT requirements, placards must be placed in locations where they won’t be in an obstructed view, or obscured by tarps or other coverings.

Things to know before you ship

If you’re a shipper moving HAZMAT cargo, you’re responsible for the proper labeling and packaging of your shipment and for providing all of the appropriate HAZMAT placards. Before you book a shipment, make sure to communicate the details of your cargo, including its hazard class, special requirements for packaging or transporting, if needed, and any assembly or disassembly specifications. Here are some other things to keep in mind:

  • Inspect the freight before transit to ensure it is secure, and that the shipment is properly packaged and labeled
  • Make sure the truck placards are in good condition and visible on all four sides of the vehicle
  • Ensure that the driver is informed of the proper safety and emergency response procedures

Following these best practices will ensure that your freight is safe and is traveling within the DOT guidelines.

Have other questions?

Do you have more questions about DOT placards or how to ship hazardous materials? Leave a comment below. For more information about HAZMAT requirements, contact 479-785-6486.

Posted in: