HazMat Endorsement Guide: Placards, Segregation Tables, and the ERG

The HazMat endorsement (H) is the most regulated CDL add-on — and the one most candidates underestimate. It’s a combination of a TSA background check (separate from your driving test) and a 30-question knowledge exam drawn from CDL Manual Section 9 plus 49 CFR.

Here’s everything on the test, distilled.

The 9 hazard classes

Memorise these — they show up on placarding and segregation questions.

Tip: The test loves to ask which class a specific material falls into. “Gasoline” → Class 3 (flammable liquid). “Oxygen” → Class 2 (gas). “Battery acid” → Class 8 (corrosive). Lock these in.

Placarding rules

A vehicle needs placards when transporting:

• Any quantity of materials in Table 1 (most dangerous — most explosives, poison gases, dangerous-when-wet, organic peroxide Type B, etc.)
• 1,001 lbs or more total of materials in Table 2 (everything else placarded)

The 1,001 lb rule is the most-asked numerical question on the test. It’s the combined weight of all hazardous materials in Table 2 categories — not per category, but total.

Did you know? Placards must appear on all four sides of the vehicle, be readable from at least 50 feet, and stay attached even if part of the vehicle is removed. Damaged or unreadable placards must be replaced before driving.

The Segregation Table

Some HazMat classes can’t ride together. The test will throw a few of these at you.

In our HazMat Test app, the Placarding Tool runs the full segregation table for you — useful during the test prep, but more useful out in the field.

Shipping papers — the four required items

Every HazMat shipment must include shipping papers with:

1. Proper shipping name (from the Hazardous Materials Table in 49 CFR 172.101)
2. Hazard class (1–9)
3. Identification number (the 4-digit UN number, e.g., UN1203 for gasoline)
4. Quantity (with packing group and total weight)

Plus an emergency response telephone number that’s answered 24/7.

Remember: Shipping papers must be kept within the driver’s reach while driving, and clearly visible on the driver’s seat when out of the vehicle. Drivers caught with HazMat papers stowed in a sleeper-berth cabinet have failed roadside inspections.

The Emergency Response Guidebook (ERG)

The ERG is the orange book that lives in every HazMat truck. It links UN numbers to emergency action steps.

How to use it (and how the test asks about it):

1. Find the 4-digit UN number on the shipping papers
2. Look it up in the yellow section (numerical index)
3. Cross-reference to a 3-digit Guide number
4. Open to that Guide page (orange section) for action steps and isolation distances
5. Check the green section for poison-gas-in-water distances (Table 1) and TIH distances (Table 3)

Our HazMat Test app ships with the full ERG 2024 built in for offline reference.

Test-day strategy for HazMat

• The test usually has 30 questions, 80% passing (≤6 wrong)
• About 10 questions will be straight placarding/labelling
• About 8 questions on shipping papers + emergency response
• About 6 questions on driving HazMat (parking restrictions, route plans, no smoking within 25 ft)
• The rest are loading, unloading, and tank-specific

Tip: The state will administer the HazMat test only after TSA clears your background check. Apply for the TSA threat assessment first — it can take 30–60 days, sometimes longer.

Studying for HazMat

The H endorsement test is short, but the failure rate is the highest of any CDL endorsement — because most candidates rely on the CDL Manual alone. The Manual covers the what; our HazMat practice quizzes drill the how and which.

Try a free HazMat quiz → (10 questions, no signup)