What are placards? When and why HazMat drivers use them

Estimated reading time: 3 minutes 

In the world of hazardous materials (HazMat) transportation, safety is essential. One of the critical elements used to ensure safety is placards. These labels play a crucial role in protecting the driver and the motoring public nearby.   

But what are placards, and why are they so important for HazMat drivers? Let’s break it down. 

What are placards? 

HazMat placards are diamond-shaped signs displayed on vehicles transporting hazardous materials. These signs feature details that provide information about the type of hazard being transported.  

Why are placards used on semi-trucks? 

Placards are used to alert emergency responders, inspectors and the public to hazardous materials being transported. They also help in regulatory compliance, ensuring that dangerous goods are transported legally. 

When are placards used on semi-trucks? 

Not all vehicles carrying hazardous materials need to have placards. The DOT provides two placarding tables that determine when placards are required.  

While there are many exceptions, the general rule is that: 

• Table 1 materials must be placarded whenever any amount is transported.  

• Table 2 materials only need placards if the total amount transported is 1,001 pounds or more. That said, transporting hazardous materials in a bulk container always calls for placarding. 

If placards are needed, there are three main factors that determine which ones are used: 

• The hazard class of the materials. 

• The number of hazardous materials shipped.  

• The total weight of all classes of hazardous materials in the vehicle. 

What information is found on a placard? 

There are six main components that may be found on a placard to identify the material inside: 

Hazard class number:  

The bottom of the placard displays the class number, indicating the type of hazard. 

UN/NA number:  

A four-digit number that identifies the specific hazardous material being transported. This is only used when shipping in a bulk container or if the product weighs 8,820lbs or more. 

Compatibility letters:  

These letters help determine which materials can be safely transported together. They are mainly used for explosives. 

Color:  

Different colors signify various hazards, such as orange for ‘explosive.’ 

Words:  

The text on a placard usually includes the name or category of the hazardous material. They provide quick identification for those familiar with the classification. 

Graphics:  

Each placard features a symbol that represents the type of hazard. For example, a flame represents flammable materials. 

What are the nine HazMat classes? 

Hazardous materials are sorted into classes by the DOT. All materials have subsections to specify packaging and labelling requirements. There are nine classes of hazardous materials, each with its own unique placard: 

Explosives (Class 1):  

Indicates materials that can cause explosions, such as dynamite and fireworks. 

Gases (Class 2):  

Covers flammable, non-flammable and toxic gases like chlorine. 

Flammable liquids (Class 3):  

Includes gasoline, alcohol and other liquids that can easily ignite. 

Flammable solids (Class 4):  

Includes materials that can catch fire through friction or heat. Examples include matches and certain metals. 

Oxidizers (Class 5):  

Includes compounds that can release oxygen and cause the combustion of other materials. One common example is hydrogen peroxide. 

Toxic and infectious substances (Class 6):  

Covers materials that are poisonous or can cause disease. Examples include medical waste and certain chemicals. 

Radioactive materials (Class 7):  

Indicates materials that emit radiation, like uranium and certain medical isotopes. 

Corrosive substances (Class 8):  

Includes materials that can destroy living tissue or damage metals. Examples include acids and alkalis. 

Miscellaneous hazardous materials (Class 9):  

Includes materials that don't fit into the other categories but are still hazardous. Examples include dry ice and lithium batteries. 

HazMat placarding guide for truck drivers 

Only drivers with a HazMat endorsement can transport materials that need placarding. That's why understanding placards is essential for complying with regulations and maintaining safety.

While the placards are provided by the shipper, it is the driver’s responsibility to: 

• Make sure the shipper has identified, marked and labeled the hazardous materials properly.  

• Refuse leaking packages and shipments.  

• Placard the vehicle when loading, if required.  

• Transport the shipment safely and without delay.  

• Follow all special rules about transporting hazardous materials. 

Additionally, drivers must follow specific requirements when placarding. Placards must be: 

• Displayed on all four sides of the vehicle. 

• Visible from the direction they face. 

• Placed so that the words and numbers are level and read from left to right. 

• Kept at least 3 inches away from any other markings on the vehicle. 

• Kept clear of doors, ladders or any other attachments or devices.  

• Kept clean and undamaged, so they remain legible.  

• Placed on a background of contrasting color. 

HazMat drivers hauling a van trailer must remove the placards after unloading. 

HazMat drivers with tank trailers must keep the placards on after unloading. Only after a tank wash facility cleans the trailer can the placards be removed.