1.1 Current Exam Facts
Key Takeaways
- The CDL HazMat (H) endorsement knowledge test has 30 multiple-choice questions, a 40-minute time limit, and an 80% passing score — 24 of 30 correct.
- The H endorsement lets you haul placardable amounts of hazardous materials; the combined X endorsement covers both HazMat and tank vehicles in one test pairing.
- The HazMat endorsement must be renewed every 5 years, and a new TSA Security Threat Assessment is required at each renewal.
- The knowledge test is administered by your state DMV under federal FMCSA standards, so the questions are standardized nationwide.
- The official knowledge source is the federal Hazardous Materials Regulations in 49 CFR and your state CDL Manual's HazMat section.
About the CDL HazMat (H) Endorsement Exam
Quick Answer: The Commercial Driver's License (CDL) Hazardous Materials (HazMat) knowledge test has 30 multiple-choice questions, a 40-minute time limit, and an 80% passing score — you must answer 24 of 30 correctly. It is given at your state Department of Motor Vehicles (DMV) under federal Federal Motor Carrier Safety Administration (FMCSA) standards. Passing the test is only one of three steps: you also need Entry-Level Driver Training (ELDT) and a Transportation Security Administration (TSA) background check.
The HazMat endorsement, shown as the letter H on your CDL, gives you legal authority to drive a commercial motor vehicle carrying hazardous materials in quantities large enough to require placards. "HazMat" covers explosives, gases, flammable liquids, corrosives, radioactive material, and other regulated substances. Because a HazMat incident can endanger the public, the endorsement carries the strictest screening of any CDL endorsement.
Who Needs the H Endorsement
You must have the H endorsement to drive a vehicle that is required to be placarded for hazardous materials, or that carries any quantity of a material listed as a select agent or toxin. A CDL alone is not enough — the endorsement is checked separately during roadside inspections, and driving placardable HazMat without it is a serious violation.
Exam Format at a Glance
| Detail | Information |
|---|---|
| Number of Questions | 30 multiple-choice questions |
| Time Limit | 40 minutes |
| Passing Score | 80% (24 of 30 correct) |
| Test Format | Written/computer-based knowledge test — no skills (driving) test for H |
| Administered By | Your state DMV, under FMCSA federal standards |
| Knowledge Test Fee | Typically $10–$25, varies by state |
| Endorsement Validity | 5 years (or until your CDL renews, whichever is first) |
The H Endorsement vs. the Combined X Endorsement
Two CDL endorsements are closely related and often confused:
- H — Hazardous Materials. Authorizes hauling placardable HazMat in any cargo tank or freight vehicle. Earned by passing the HazMat knowledge test.
- N — Tank Vehicle. Authorizes driving a vehicle designed to carry liquids or gases in a permanently mounted or portable tank. Earned by passing the separate Tank Vehicles knowledge test.
- X — Combined HazMat and Tank. When a driver passes both the HazMat test and the Tank Vehicle test, the state issues a single combined X endorsement instead of listing H and N separately. The X endorsement does not have its own exam — it is simply the result of holding both.
Many HazMat loads travel in cargo tanks (fuel, chemicals), so drivers commonly pursue the X endorsement to keep their options open.
A Knowledge Test — Not a Driving Test
Unlike adding a school bus (S) endorsement, the HazMat endorsement requires no behind-the-wheel skills test. It is purely a knowledge test. That makes the written exam the main gatekeeper, so the content below — 49 CFR rules, placarding, loading, and emergency response — must be studied carefully.
Renewal: Every 5 Years
The HazMat endorsement is not permanent. It must be renewed at least every 5 years, and it expires no later than your CDL itself. At each renewal you must complete a new TSA Security Threat Assessment background check. Some states require renewal sooner, so always confirm the cycle with your own DMV.
The Official Knowledge Source
The exam is built from federal law, not from any single textbook:
- 49 CFR (Code of Federal Regulations), Parts 100–185 — the Hazardous Materials Regulations (HMR), the legal foundation for everything on the test.
- Your state CDL Manual — the HazMat section summarizes the HMR into test-ready form; the federal model is the AAMVA CDL Manual used by most states.
- The Emergency Response Guidebook (ERG) — the orange book carried in HazMat cabs and referenced in emergency-response questions.
Because the questions come from federal regulations, the HazMat test content is essentially the same in every state even though the DMV that gives it differs.
What score must you achieve to pass the CDL HazMat (H) endorsement knowledge test?
A driver passes both the HazMat knowledge test and the Tank Vehicle knowledge test. Which endorsement will the state issue?
How often must the HazMat endorsement be renewed?
Where is the CDL HazMat knowledge test administered, and what is its primary legal source?