CDL: Hazardous Materials
Hazardous Materials Rules for All Commercial Drivers
You don't need a hazardous materials endorsement to need hazardous materials knowledge. Even drivers without the endorsement have to be able to recognize hazardous cargo and understand whether they're legally allowed to haul it. This article covers the basics every commercial driver should know — even before getting into the deeper material required for the endorsement itself.
What Counts as a Hazardous Material?
Hazardous materials are products that pose a risk to health, safety, or property while they're being transported. That risk is exactly why the rules around them exist in the first place.
Why These Rules Exist
The regulations surrounding hazardous materials transportation serve three main purposes: containing the product itself, communicating the risk it poses to others, and ensuring that both drivers and equipment are safe to handle it.
Containing the Product
Many hazardous materials can cause injury or death through direct contact. To reduce that risk, the rules spell out how shippers must package these products safely. Similar rules govern how drivers should load, haul, and unload bulk tanks. Together, these make up the containment side of the regulations.
Communicating the Risk
Shippers rely on two main tools to warn others about what they're handling: shipping papers and diamond-shaped hazard labels. Shipping papers — which might take the form of shipping orders, bills of lading, or manifests — describe the hazardous materials being transported. Diamond-shaped hazard warning labels are placed on most hazardous materials packages to alert dockworkers and drivers to the danger. When a package is too small or oddly shaped to fit a label, shippers use tags instead — compressed gas cylinders are a common example.
Because a crash or hazardous materials spill could leave you injured and unable to explain what you're carrying, it's essential that emergency responders can find this information themselves. Firefighters and police can limit the damage and injury at a scene far more effectively if they know what hazardous materials are involved. For that reason, you're required to either identify your hazardous materials shipping papers clearly or keep them on top of any other paperwork. These papers must also be kept in one of three places:
- In a pouch mounted on the driver's door, or
- In clear view within reach while you're driving, or
- On the driver's seat whenever you're out of the vehicle
Ensuring Safe Drivers and Equipment
The third purpose behind these rules is making sure both the person behind the wheel and the vehicle itself are up to the task of safely handling hazardous cargo.
Placards, Identification Numbers, and Endorsements
Placards are the signs placed on the outside of a vehicle to identify the hazard class of what it's carrying. A vehicle that needs placards must display at least four identical ones — mounted on the front, rear, and both sides — and each must be readable from all four directions. Placards must measure at least 10¾ inches square and be displayed as a diamond, turned upright on a point. Cargo tanks and other bulk packaging also show an identification number for their contents, either on the placards themselves or on separate orange panels.
Identification numbers are four-digit codes that first responders use to identify hazardous materials. The same number can sometimes apply to more than one chemical on a shipping paper. Each number is preceded by the letters "NA" or "UN," and the US DOT's Emergency Response Guidebook lists which chemicals correspond to which numbers.
| Class | Class Name | Example |
|---|---|---|
| 1 | Explosives | Ammunition, dynamite, fireworks |
| 2 | Gases | Propane, oxygen, helium |
| 3 | Flammable | Gasoline fuel, acetone |
| 4 | Flammable solids | Matches, fuses |
| 5 | Oxidizers | Ammonium nitrate, hydrogen peroxide |
| 6 | Poisons | Pesticides, arsenic |
| 7 | Radioactive | Uranium, plutonium |
| 8 | Corrosives | Hydrochloric acid, battery acid |
| 9 | Miscellaneous hazardous materials | Formaldehyde, asbestos |
| None | ORM-D (Other Regulated Material – Domestic) | Hair spray, charcoal |
| None | Combustible liquids | Fuel oils, lighter fluid |
Not every vehicle carrying hazardous materials is required to display placards — the specific rules for when placards are needed are covered in a different section of the manual. If your vehicle isn't required to display placards, you're allowed to drive it even without a hazardous materials endorsement. But if placards are required, you cannot legally drive that vehicle unless your CDL includes the hazardous materials endorsement.
To earn the hazardous materials endorsement, you'll need to pass a written test on the more detailed material covered elsewhere in the manual. A separate tank endorsement is also required in certain cases — specifically, if your vehicle needs a Class A or B CDL and has either a permanently mounted cargo tank of any size, or a portable tank with a capacity of 1,000 gallons or more. Notably, the tank endorsement applies based on the vehicle's equipment, not on whether the liquid or gas being hauled is itself hazardous.
Drivers who hold the hazardous materials endorsement are also responsible for knowing the rules about which products can and cannot be loaded together — information that's covered in more depth elsewhere in the manual. Before combining different types of product on one truck, you need to know whether that combination is safe. If you're ever unsure, check with your employer and consult the applicable regulations before loading.
Even for drivers who never plan to haul placarded loads, understanding these basics matters. Recognizing a hazard class label, knowing where hazardous shipping papers need to be kept, and understanding when an endorsement is legally required are all part of being a safe, informed commercial driver.