The HazMat Table is the single most important reference document a hazardous materials hauler will touch in a career, and most drivers never really learn how it works until they sit for the CDL endorsement test. You will hear it called the 172.101 Table, the Hazardous Materials Table, or simply "the table." It lives inside Title 49 of the Code of Federal Regulations, Part 172, Section 101, and the Federal Motor Carrier Safety Administration uses it to control how shippers and drivers identify, classify, package, and placard regulated cargo before it ever rolls down an interstate.
This guide pulls the table apart column by column. You will see how to look up a proper shipping name, how to read a hazard class, what the packing group means in plain English, and where placarding and labeling rules live. The same logic appears on the DMV hazmat written exam, on the road, and inside any carrier compliance audit. Get the table right and most of the rest of the hazmat endorsement falls into place.
One quick note before going deep. The hazmat table is not a study list to memorize line by line. There are roughly four thousand entries. What you actually memorize is the structure of the table, the column headers, and a small set of letter and number codes. That is what this article focuses on. The detail-level entries you will look up when the time comes.
Those four numbers shape almost every question on the endorsement test. There are nine numbered hazard classes plus a handful of divisions inside class 1 (explosives) and class 2 (gases). Packing groups I, II, and III rank danger from greatest to least within most classes. The ten columns of the table tell you everything else: shipping name, identification number, label codes, special provisions, package authorizations, quantity limits by transport mode, and vessel stowage rules.
If you want a walking-around mental model, picture the table as a giant phone book of regulated cargo. Each row is one product. The first columns identify the product. The middle columns describe its risk profile. The last columns tell the driver, shipper, and carrier what physical steps are required before that product can move. You don't need every page in your head. You need to know how to open it, find the row, and read across.
49 CFR 172.101 is the official source. The same table appears in the Federal Motor Carrier Safety Regulations pocketbook, the Emergency Response Guidebook companion, and most state CDL manuals. Test questions cite the section number, the column number, or the letter codes — not the page number — so always reference content by column header.
PHMSA updates the table periodically. Drivers and dispatchers should check the published date on whatever printed copy they keep in the cab. A 2014 reprint is still useful for the column structure, but specific entries may have shifted. The free electronic edition on the eCFR site reflects the current rule.
Most state CDL manuals reprint a stripped-down version of the table with the most common shipping names. The full table appears in the Federal Register and on the Pipeline and Hazardous Materials Safety Administration (PHMSA) site. For test prep, the simplified reprint is enough. For real-world dispatch, the carrier compliance team uses the full version. Either way, the column structure is identical.
Column structure is the heart of the test. Many endorsement questions show you a partial row and ask what a symbol means or what column carries a given piece of information. Walk through each column once, slowly, and the rest of the endorsement gets dramatically easier.
This column flags how an entry must be used. A plus sign (+) fixes the proper shipping name, hazard class, and packing group no matter what. An A means the entry only applies when the material moves by aircraft. A W means the entry only applies on a vessel. A D means the entry is used for domestic shipments only, while an I means it's used for international ones. A G signals that a generic name needs a technical name added in parentheses on the shipping paper. New drivers miss the symbol column and lose easy points on the test.
This is the official name of the product. It is the name that must appear on shipping papers and, where required, on the package itself. Trade names like "WD-40" or "Liquid Lightning" never appear here. You will see entries like "Gasoline," "Sulfuric acid," or "Flammable liquid, n.o.s." The abbreviation n.o.s. means "not otherwise specified" and is used when no exact match exists for a chemical.
One number, sometimes followed by a decimal. Class 3 is flammable liquids. Class 8 is corrosive. Class 1.1 is mass-explosion explosives. The class drives the placard color and the label diamond on the package. Memorize the nine classes for the test — they show up in nearly every section.
Divisions 1.1 through 1.6, ranked by mass-explosion or fragmentation risk. Includes dynamite, fireworks, ammunition, detonating cord, and military munitions. The lower the second digit, the greater the explosion hazard.
Flammable gases (2.1), non-flammable compressed gases (2.2), and toxic gases (2.3). Propane, oxygen, anhydrous ammonia, and chlorine all ride here. No packing groups apply to class 2.
Gasoline, ethanol, paint thinner, jet fuel, diesel exception. Liquids with a flashpoint at or below 60°C (140°F). Uses all three packing groups depending on flashpoint and boiling point.
Includes spontaneously combustible materials (4.2) and substances dangerous when wet (4.3) alongside flammable solids (4.1). Phosphorus, magnesium turnings, sodium metal.
Materials that intensify a fire by releasing oxygen (5.1) and unstable peroxides that decompose explosively (5.2). Ammonium nitrate fertilizer, hydrogen peroxide solutions, MEKP.
Toxic by inhalation, ingestion, or skin contact (6.1) and infectious biological agents (6.2). Pesticides, certain pharmaceuticals, medical waste, regulated biological samples.
Anything with an activity concentration above the regulatory threshold. Three transport categories (white-I, yellow-II, yellow-III) defined by surface dose rate and transport index.
Sulfuric acid, sodium hydroxide, battery fluid, hydrochloric acid. Causes visible destruction to skin or steel within set test thresholds. Often subsidiary risk for class 3 and class 6 entries.
Lithium batteries, dry ice, environmentally hazardous substances, elevated-temperature materials, polymeric beads. The catch-all class for hazards that don't fit 1 through 8.
Notice how some classes split into divisions. Class 1 has six divisions tied to explosion behavior. Class 2 has three divisions tied to whether the gas is flammable, inert, or poisonous. Class 4 has three divisions for solid, spontaneously combustible, and water-reactive. Class 5 splits oxidizers (5.1) from organic peroxides (5.2). Class 6 splits toxic (6.1) from infectious (6.2). Drivers who lump everything into the parent class miss subtle answer choices on the exam.
The four-digit UN or NA number. UN1203 is gasoline. UN1075 is liquefied petroleum gas. UN1830 is sulfuric acid. The ID number is also what gets posted on the orange panel beneath a placard or directly on the placard itself when required. Emergency responders look up that number first in the Emergency Response Guidebook.
Packing groups rank degree of danger within a class. PG I is the most dangerous (great danger), PG II is medium, PG III is the least (minor danger). Packing group I products usually need stronger containers, smaller quantity limits, and more conservative stowage. The hazmat test routinely shows a row with PG II and asks which container performance level applies.
The diamond-shaped labels that go on the package itself. Most rows show one or more class numbers separated by commas. These are the same diamond symbols you see on the placards but smaller. A subsidiary risk label is shown in parentheses, like "3, (8)" for a flammable liquid that is also corrosive.
Codes like A1, B5, N76, or T11 that point to extra rules in section 172.102. They cover things like aircraft-only restrictions, additional package design requirements, or exceptions to general rules. You don't memorize them for the test — you memorize that column 7 sends you to 172.102.
Sub-columns 8a, 8b, and 8c reference exception, non-bulk, and bulk packaging sections. Each cell shows a section number under part 173. The endorsement exam will sometimes ask which sub-column applies to a bulk tank — that's always 8c.
Sub-columns 9a (passenger aircraft and rail) and 9b (cargo aircraft) tell you the max net quantity per package by transport mode. A "Forbidden" entry means that mode is not allowed. This column shows up frequently on hazmat written tests because it ties hazard class to transport restrictions in one glance.
Letter codes (A, B, C, D, E) and stowage location codes for cargo vessels. Truck drivers don't act on this column, but the table requires it for products that may transfer to a vessel. Test writers occasionally use column 10 in a distractor answer — recognize it and move on.
Working through real entries beats reading a description. Notice the patterns. Gases (class 2) have no packing group. Forbidden in column 9a means no passenger transport. A plus sign in column 1 means even if the chemistry sometimes looks like a different class, this row is the one that controls. Each pattern is a question the DMV writers love to ask.
Two pieces of information that students confuse on test day. Hazard class describes the kind of risk. Packing group describes the degree of risk inside that kind. A class 3 PG I flammable liquid is more volatile than a class 3 PG III flammable liquid. The class is about chemistry. The packing group is about how aggressive the packaging has to be.
Some classes never get a packing group. Class 2 gases, class 7 radioactives, and certain class 1 explosives don't use packing groups because hazard is described entirely by division. When the test shows a class 2 product and offers "PG II" as an answer, that answer is wrong by structure alone.
Each of those mistakes maps to a wrong answer on the endorsement test. The trade name trap especially. A bottle of Drano in a delivery van is not labeled with the trade name on the shipping paper — it is labeled "Sodium hydroxide, solution" or "Corrosive liquid, basic, inorganic, n.o.s." depending on the exact mixture. Test questions use trade names as distractors to see if you'll fall for the consumer label.
Placards live on the outside of a vehicle or bulk container. Labels live on packages. Both come from the same hazard class. The HazMat Table tells the shipper which label is required (column 6) and the placarding rules in 172.504 tell the carrier when placards are required on the trailer.
The general rule: Table 1 materials require placards in any quantity, even one package. Table 2 materials require placards when the aggregate gross weight equals or exceeds 1,001 pounds. Most class 3, 4, 5, 6.1 (PG II/III), 8, and 9 products fall under Table 2. Most class 1, 2.3, 4.3, 5.2 (some), 6.1 (PG I inhalation), and 7 fall under Table 1. The endorsement test loves the 1,001-pound threshold. Memorize it.
Some chemicals carry more than one risk. A flammable liquid that's also corrosive (a battery acid solvent, say) shows the primary label as a diamond and a subsidiary label as a smaller diamond without the class number printed. Column 6 of the table lists both. On the placard, the primary class is shown — the subsidiary appears on the package label only.
The eight-step routine sounds slow on paper. After a few weeks of dispatching real loads, drivers do it in under thirty seconds per shipping paper. The exam will not give you the table itself in most jurisdictions, so you are tested on whether you understand which column holds which fact. State CDL manuals reprint the column headers — if you remember the headers, you can answer almost any structural question.
Once the table is comfortable, the rest of the hazmat endorsement starts looking like extensions of it. The HazMat placards rules use column 3 to pick the placard. Shipping papers use columns 2, 3, 4, and 5 to fill in the description. Emergency response uses column 4 to find the right ERG page. HazMat training requirements from 172 Subpart H all reference the table by section number.
For test prep, pair this guide with a written hazmat test review and a few practice rounds of the CDL hazmat practice test. Repetition with realistic questions cements the column structure faster than any chart memorization. You're not trying to learn 4,000 entries. You're learning ten columns and nine classes well enough to look up any row.
Most endorsement exams pull about 20 to 30 hazmat-table-related questions per session, mixed with placarding, loading and unloading, emergency response, and driving rules. The table questions cluster around three themes: identifying the right column for a given piece of information, mapping a class to a placard color, and recognizing what a symbol or letter code means.
Treat each question as a column lookup. If the question asks where to find the packing group, the answer is column 5. If it asks what UN1203 means, the answer is gasoline. If it asks why a row has a plus sign in column 1, the answer is that the proper shipping name and class are fixed. Build that mental map before sitting for the exam and the table portion goes from intimidating to almost reflexive.
Short, repeated study beats marathon cramming. Fifteen minutes a day for two weeks with a structured practice tool will outperform a single seven-hour Saturday session by a wide margin. Spaced repetition reinforces the column-to-information mapping, and that mapping is the actual skill the test measures.
The HazMat Table looks intimidating the first time a new driver opens 49 CFR 172.101 and sees thousands of rows of chemistry. It stops looking that way the moment the column structure clicks. Ten columns, nine classes, three packing groups, a handful of symbols. That's the entire framework. Every endorsement question, every shipping paper, every placard decision, every emergency response lookup pulls from those same column headers. Spend a few hours learning the structure with realistic hazardous materials endorsement practice questions and the rest of the endorsement starts solving itself.
Print a one-page summary of the ten column headers and tape it inside your study binder. Drill yourself once a day on which column holds which fact. Mix in a handful of UN number look-ups — UN1203 (gasoline), UN1830 (sulfuric acid), UN1075 (LP gas), UN3480 (lithium-ion batteries). When you can identify each one in under five seconds, the structural questions on the written exam stop being a memory test and start being a recognition test.
Finally, treat the endorsement as the start of a longer career obligation. After passing the test, recurrent hazmat training every three years is federally required. The column structure you learn now is the same structure you will use during every recurrent training class for as long as you carry placarded loads. Build the mental model once, and refresh it on a schedule.