DOT Hazmat Placards: Complete Visual Guide for the CDL Endorsement
Master DOT hazmat placards for the CDL H endorsement exam. All 9 hazard classes, placard thresholds, divisions, and the rules examiners test most. Updated 2026.
What Is the CDL Hazmat Endorsement and Why Do Placards Matter?
The CDL hazmat (H) endorsement allows commercial drivers to transport materials regulated under 49 CFR Parts 171–180, the federal hazardous materials regulations. To earn the endorsement, candidates must pass a written knowledge test administered by their state, covering hazard classes, shipping papers, emergency response, and — most heavily — placarding. Placards matter because they are the first line of communication in a roadside emergency. A firefighter arriving at a crash scene reads the placard before they do anything else. The placard tells them what's in the trailer, what class of hazard they're dealing with, and what emergency procedures apply. Getting placarding wrong in real life has life-or-death consequences, which is exactly why the DOT tests it so thoroughly. The CDL hazmat exam draws its questions directly from 49 CFR Part 172, Subpart F — the placarding regulations. Knowing those rules cold, particularly Table 1 and Table 2 from Section 172.504, is the foundation of passing.
The Two Placard Tables: Table 1 vs. Table 2
The single most important framework on the CDL hazmat exam is the distinction between Table 1 and Table 2 materials. Get this right and roughly a third of placard questions resolve themselves. Table 1 — Always placard, any quantity. These are the most dangerous materials. If you're transporting any amount of a Table 1 material — even a small package — you must placard the vehicle. There is no minimum quantity threshold. Table 1 includes: Explosives (1.1, 1.2, 1.3), Poison Gas (2.3), Dangerous When Wet (4.3), Poison Inhalation Hazard (PIH) materials in Classes 6.1 and 8, and Radioactive materials with a Yellow III label. Table 2 — Placard when you have 1,001 pounds or more (combined weight on shipping papers). These are serious but less acutely dangerous materials. You only need to placard for Table 2 materials once you have 1,001 lbs or more in a single load. Below that threshold, placarding is optional — though shipping papers are still required. Table 2 covers most of the remaining classes: Flammable Gas (2.1), Non-Flammable Gas (2.2), Flammable Liquids (3), Flammable Solids (4.1), Spontaneously Combustible (4.2), Oxidizers (5.1), Organic Peroxides (5.2), Poisons (6.1, non-PIH), Irritants (6.2), Corrosives (8), and Miscellaneous (9). The exam will test this distinction directly and often in tricky ways. A common question format: "A driver is transporting 800 lbs of a Class 8 corrosive material and 400 lbs of a Class 3 flammable liquid. Must the vehicle be placarded?" Both materials are Table 2. Neither individually reaches 1,001 lbs — but combined on a single set of shipping papers, they total 1,200 lbs, which does require placarding. Know how to add them up.
All 9 Hazard Classes: Placards, Colors, and What the Exam Tests
Every hazmat class has its own placard — a diamond-shaped sign displayed on all four sides of the vehicle. Here's what the CDL exam actually tests for each class. Class 1 — Explosives. Six divisions (1.1 through 1.6). The exam focuses on 1.1 (mass explosion), 1.2 (projection hazard), and 1.3 (fire hazard) — all Table 1. The EXPLOSIVES 1.1, 1.2, and 1.3 placards are orange. Key exam fact: if you have both 1.1 and 1.2 explosives in the same load, you must use the 1.1 placard — the more hazardous class governs. Class 2 — Gases. Three divisions: Flammable Gas (2.1) uses a red placard; Non-Flammable Gas (2.2) uses a green placard; Poison Gas (2.3) uses a white placard with a skull — it's Table 1, any quantity. The exam tests whether candidates know that oxygen is Class 2.2, not a flammable gas. Class 3 — Flammable Liquids. Red FLAMMABLE placard. Includes gasoline, acetone, and ethanol. Table 2, threshold 1,001 lbs. Key exam trap: combustible liquids (flash point between 100°F and 200°F) use a COMBUSTIBLE placard — different from FLAMMABLE. Class 4 — Flammable Solids. Three divisions with different hazard profiles: 4.1 Flammable Solid (red/white striped), 4.2 Spontaneously Combustible (red/white), and 4.3 Dangerous When Wet (blue — Table 1 any quantity). The Table 1 status of 4.3 materials is a consistent exam question. Class 5 — Oxidizers and Organic Peroxides. Yellow OXIDIZER placard for 5.1; yellow ORGANIC PEROXIDE for 5.2. Both Table 2. The exam may ask why oxidizers are dangerous — they accelerate burning of other materials, not because they are flammable themselves. Class 6 — Poisons and Infectious Substances. Class 6.1 poisons use a white POISON placard. When a 6.1 poison also meets Poison Inhalation Hazard criteria, it moves to Table 1. Class 6.2 (infectious substances) is rarely tested in depth but know the biohazard symbol association. Class 7 — Radioactive. Three label types: White I, Yellow II, Yellow III. Only Yellow III–labeled packages trigger the Table 1 placard requirement for the vehicle. The RADIOACTIVE placard is yellow and white. Class 8 — Corrosives. Black and white CORROSIVE placard. Includes sulfuric acid, hydrochloric acid, and sodium hydroxide. Table 2. Corrosive materials damage skin on contact and attack metal — a detail tested in emergency response questions. Class 9 — Miscellaneous. Black and white striped CLASS 9 placard. Table 2. Includes elevated temperature materials. Not tested heavily, but know the placard exists.
Common Exam Traps on Placarding Questions
The CDL hazmat exam is designed to reward careful reading, not just memorization. These are the traps that appear on the actual test. The DANGEROUS placard. When transporting a combined load of two or more Table 2 materials that reach the 1,001 lb threshold, you have the option to use a single DANGEROUS placard instead of individual class placards — unless you are loading 2,205 lbs or more of a single Table 2 material at one location, in which case that material's specific placard is required. Many candidates don't know the DANGEROUS placard exists. Placard placement. The exam tests that placards must be displayed on all four sides of the vehicle — front, rear, left, and right. They must be visible, readable, and not obscured. Placards on cargo tanks must be displayed even when empty, until the tank has been cleaned and purged. Subsidiary hazards. A material may have a primary hazard class and a subsidiary hazard requiring an additional placard. For example, a flammable liquid that also meets PIH criteria requires both a FLAMMABLE and a POISON INHALATION HAZARD placard. The exam will describe a material and ask how many placards are required. Interchangeable placards. FLAMMABLE may be used in place of COMBUSTIBLE when the transport vehicle carries both flammable and combustible liquids. The exam tests whether candidates know this substitution is permitted.
Study Strategy: How to Pass the CDL Hazmat Endorsement Exam
The CDL hazmat exam covers placarding, shipping papers, emergency response, driver responsibilities, and loading/unloading rules — but placards account for a disproportionate share of questions. Build your study plan around this priority order. First two weeks: master the Table 1 vs. Table 2 distinction and memorize all 9 hazard classes with their placard colors. Don't move on until you can name every Table 1 material without looking. Next two weeks: take practice questions daily, 30–50 questions per session. Focus on threshold and combination questions. Review every wrong answer and look up the relevant CFR section. Final week: take full-length timed mock exams. Most state CDL hazmat exams are 30–50 questions with an 80% passing threshold. Practice at pace — know where the tricky material is and don't second-guess your Table 1 / Table 2 recall. The VoltExam CDL Hazmat Prep app includes 1,000+ practice questions drawn directly from 49 CFR Parts 171–180, a complete DOT placard guide with all 9 hazard classes and visual references, and per-topic progress tracking so you can see exactly which placard rules still need drilling. It works fully offline — useful for studying at the terminal, in the truck cab, or anywhere without a reliable connection.
Free CDL Hazmat Tools