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CDL Study Guides · 2026
The HazMat endorsement opens up higher-paying loads — but it's also the only endorsement that requires a federal TSA background check on top of passing the knowledge test.
Last reviewed 2026-06-20 · Based on FMCSA standards (see sources)
Hazardous materials are organized into nine classes based on the type of danger they present. As a hazmat driver, you must understand these classes, their labels, and how to identify them on shipping papers and placards.
Class 1 is Explosives, divided into six divisions based on the type of explosive hazard (mass explosion, projection, fire, minor blast, very insensitive explosives, and extremely insensitive detonating articles). Class 2 is Gases: 2.1 is flammable gas, 2.2 is non-flammable compressed gas, and 2.3 is poisonous/toxic gas. Class 3 is Flammable Liquids — this includes gasoline, diesel fuel, and many solvents.
Class 4 covers Flammable Solids (4.1), Spontaneously Combustible materials (4.2), and Dangerous When Wet materials (4.3). Class 5 includes Oxidizers (5.1) and Organic Peroxides (5.2). Class 6 is Poisonous (Toxic) Materials: 6.1 is poison and 6.2 is infectious substances.
Class 7 is Radioactive Materials. Class 8 is Corrosives — acids and bases that can destroy living tissue or metal. Class 9 is Miscellaneous Hazardous Materials that do not fit other classes, including environmentally hazardous substances, elevated-temperature materials, and genetically modified organisms.
Placards are diamond-shaped signs placed on all four sides of a vehicle to warn others about the hazardous cargo. The shipper is responsible for providing placards when required, and the driver is responsible for placing them correctly. Generally, placards are required when you carry 1,001 pounds or more of a single hazmat class. However, some materials require placards regardless of quantity: any amount of poison gas, certain explosives, and radioactive materials.
The Dangerous placard can be used in place of individual placards when you are carrying mixed loads of two or more classes in table 2 of the hazmat regulations — but only when the total weight of all hazmat is 1,001 to 5,000 pounds. Above 5,000 pounds of any class, the specific placard for that class is required.
Key points to remember
Shipping papers are the critical link between the cargo, the driver, and emergency responders. Every hazmat shipment must be accompanied by shipping papers that describe exactly what is being transported and how dangerous it is.
Shipping papers must include four key pieces of information for each hazmat item: the proper shipping name (the official name from the hazmat table), the hazard class or division number, the UN/NA identification number (a four-digit number preceded by UN or NA), and the packing group (I for great danger, II for medium danger, III for minor danger). The total quantity must also be listed.
Hazmat items must be highlighted on the shipping paper so they stand out from non-hazmat items. This can be done by highlighting, listing them first, or placing an X in a designated column. The letters RQ indicate a reportable quantity — a spill of this amount must be reported to the National Response Center.
While driving, the shipping papers must be within immediate reach at all times. When the driver is at the controls, the papers must be in a pouch on the driver's door or in clear view within reach. When the driver is out of the vehicle, the papers must be on the driver's seat or in a holder mounted on the inside of the door.
The Emergency Response Guidebook (ERG) must be kept in the vehicle when transporting hazmat. It provides guidance for first responders on how to handle hazmat emergencies during the first 30 minutes. The ERG uses the four-digit UN/NA number to identify the material and guide the emergency response.
Shippers must also provide emergency contact information on the shipping papers — a phone number monitored 24 hours a day where emergency responders can get detailed information about the hazmat being transported.
Key points to remember
Loading and unloading hazardous materials requires strict adherence to rules designed to prevent spills, fires, and exposures. As the driver, you are responsible for ensuring these rules are followed even if someone else is handling the cargo.
Before loading, make sure the vehicle is properly placarded for the material being loaded. The cargo area must be clean and free of sharp objects that could puncture containers. Use the correct tie-downs and blocking to prevent movement. Never load damaged or leaking packages — refuse them.
Certain materials cannot be loaded together. For example, Division 1.1 or 1.2 explosives must never be loaded with any other hazmat class. Oxidizers (Class 5.1) must not be loaded with flammable liquids (Class 3). Cyanide or cyanide mixtures must not be loaded with acids. The hazmat compatibility chart specifies which classes can and cannot be loaded together.
No smoking is allowed within 25 feet of a vehicle being loaded with hazmat, or within 25 feet of any vehicle containing explosives or flammable materials. The engine should be off during loading unless needed to operate a pump or other equipment.
While transporting hazmat, you must follow specific route and stopping rules. You cannot park within 5 feet of a traveled portion of the road. When stopped, someone must always be in attendance of the vehicle unless it is in a safe haven (a government-approved area for parking hazmat vehicles). Attended means someone is within 100 feet of the vehicle with a clear view of it.
Hazmat vehicles have additional rules about tunnels, bridges, and routing. Some tunnels restrict hazmat vehicles entirely. You must follow designated hazmat routes when they exist. When fueling, the engine must be off (except for diesel vehicles with a fuel-powered heater).
Key points to remember
In a hazmat emergency, your first priority is to protect yourself, other people, and the environment. Hazmat emergencies can involve fires, leaks, spills, or exposures to toxic materials. Your actions in the first minutes are critical.
If you discover a leak or spill, do not touch the material. Many hazardous materials can be absorbed through the skin, and some are immediately dangerous to life and health (IDLH). Move away from the spill and get upwind. Contact emergency services immediately and have your shipping papers ready — responders need to know exactly what material is involved.
For a fire involving a hazmat vehicle, call 911 first. If the fire is small and in the early stages, and you have the right type of fire extinguisher and can fight it safely, you may attempt to put it out. However, if the fire involves explosives, poisonous gases, or is near cargo that could produce toxic fumes, get away immediately. Explosives in a fire can detonate — do not fight the fire.
When reporting a hazmat incident, provide: your location, the nature of the incident (fire, spill, leak), the name and classification of the hazardous material (from shipping papers), the amount involved, and your name and callback number. Any spill or leak of a reportable quantity must be reported to the National Response Center at 1-800-424-8802.
The Emergency Response Guidebook provides initial response procedures based on the UN/NA identification number. It includes recommended evacuation distances, fire-fighting guidance, and first aid information. Study the ERG — you may be the first person at the scene and the only one who knows what the cargo is.
If you are involved in an accident with hazmat, do not move the vehicle unless it is necessary to prevent further damage or injury. Set up warning devices and keep people away. Do not allow smoking or open flames near the scene. If anyone has been exposed to the material, make note of it for emergency responders — some hazmat exposures have delayed symptoms.
Key points to remember
Run real practice questions on this section until you're comfortably past 80%.
Practice Hazardous Materials questionsBeyond passing the HazMat knowledge test, federal law requires a TSA security threat assessment — a fingerprint-based background check — before the H endorsement can be added to your CDL. Start that application early, because it can take several weeks to clear.
As a general rule, placards are required once you're carrying 1,001 pounds or more (combined) of hazardous materials. Some materials — any amount of poison gas, certain explosives, and radioactive materials — require placards at any quantity. Placards go on all four sides of the vehicle.
For each hazardous item the shipping paper must list the proper shipping name, the hazard class or division, the UN/NA identification number, the packing group, and the quantity. The hazmat entries have to be highlighted or listed first, and the papers must stay within your reach while driving.
The ERG must be carried in the vehicle when you haul hazmat. First responders — and you — use the four-digit UN/NA number to look up how to handle a spill or fire in the critical first 30 minutes. Reportable-quantity spills must be called in to the National Response Center at 1-800-424-8802.
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Based on the FMCSA CDL Manual, a U.S. federal government publication in the public domain. Independent study aid — not affiliated with or endorsed by FMCSA, AAMVA, or any state DMV. Always confirm current rules with your state DMV.