Hazmat placard classes explained

The placard chart

These are our own drawings, made from simple shapes in the ordinary colours each class uses. They are for practice. The guide shown under each one is the placard table's initial guide.

The nine classes

• Class 1, explosives. 1.1: explosives with a mass explosion hazard; 1.2: explosives with a projection hazard but no mass explosion hazard; 1.3: explosives with a fire hazard and a minor blast or projection hazard; 1.4: explosives that present no significant hazard; 1.5: very insensitive explosives with a mass explosion hazard; 1.6: extremely insensitive articles with no mass explosion hazard.
• Class 2, gases. 2.1: flammable gases; 2.2: non-flammable, non-toxic gases; 2.3: toxic gases.
• Class 3, flammable liquids. Flammable liquids (and combustible liquids in the United States).
• Class 4, flammable solids. 4.1: flammable solids, self-reactive substances and solid desensitized explosives; 4.2: substances liable to spontaneous combustion; 4.3: substances that give off flammable gases in contact with water.
• Class 5, oxidizers and organic peroxides. 5.1: oxidizing substances; 5.2: organic peroxides.
• Class 6, toxic and infectious substances. 6.1: toxic substances; 6.2: infectious substances.
• Class 7, radioactive materials. Radioactive materials.
• Class 8, corrosives. Corrosive substances.
• Class 9, miscellaneous. Miscellaneous dangerous goods and articles.

Reading a placard

Start at the bottom corner. A red placard with a flame could be class 2 (a flammable gas) or class 3 (a flammable liquid); the corner number settles it. Divisions share the class number: a green NON-FLAMMABLE GAS placard, a red FLAMMABLE GAS placard and a POISON GAS placard all show 2. Then read the word, where there is one, and the symbol. The POISON GAS and POISON INHALATION HAZARD placards have a black upper corner with the skull in white, which is the quickest way to spot a material that is toxic by inhalation.

Toxic by inhalation is not only a Division 6.1 matter. A material whose entry in the Hazardous Materials Table carries an inhalation hazard special provision, whatever its class, also takes the POISON INHALATION HAZARD placard beside its class placard (49 CFR 172.505), unless that placard is already POISON GAS or POISON INHALATION HAZARD. Anhydrous hydrogen fluoride, UN1052, is class 8: a bulk load shows CORROSIVE and POISON INHALATION HAZARD together, and the drill draws both. The class is still 8.

Two colours on one placard mean a specific division. White over red is 4.2, spontaneously combustible. Red over yellow is 5.2, organic peroxide. Yellow over white is 7, radioactive. White over black is 8, corrosive. Seven red stripes on white is 4.1, flammable solid.

Worked example: a placard and nothing else

A trailer shows an orange EXPLOSIVES placard marked 1.1. There is no shipping paper and no number, and there cannot be one: explosives are not listed by ID number in the guidebook, and the rules forbid an ID number on an EXPLOSIVES placard. The placard table sends divisions 1.1, 1.2, 1.3 and 1.5 to Guide 112, and its Evacuation section says to isolate at least 500 m (1/3 mile) in all directions as an immediate precaution. Divisions 1.4 and 1.6 go to Guide 114 instead.

Numbered placards and orange panels

On bulk loads the four digit ID number may be shown across the middle of the placard, in place of the word, or on an orange panel beside it. That number is worth more than the placard: it takes you to the yellow section and the exact guide for the material. The UN numbers guide explains what to do with it.

Common mistakes

• Reading the class from the colour alone. Red is class 2, 3 and part of 4 and 5.
• Treating a subsidiary placard as the main one. The primary class is the one the numbered placard or shipping paper names first.
• Expecting a placard on every load. Small shipments of many classes need no placard at all, so the absence of one proves nothing.
• Using the placard table's guide after an ID number has been found.

Practise one class at a time in practice by class, or try today's mixed set in the daily drill.

Sources

Checked on 27 September 2026. Everything here is said in our own words; the guidebook's text is paraphrased, never quoted at length. Where your instructor, your employer's plan or the current printed guidebook says something different, follow them.

• 2024 Emergency Response Guidebook, Hazard Classification System (printed page 6). The nine classes and their divisions; opened 27 September 2026.
• 2024 Emergency Response Guidebook, Table of Markings, Labels and Placards (printed pages 7 to 9). The placard table and its initial guides, for use only when the ID number and name are unknown; opened 27 September 2026.
• 49 CFR 172.504, general placarding requirements, tables 1 and 2, and 172.505, placarding for subsidiary hazards (eCFR text as of 1 September 2026). Which placard each class takes, the DANGEROUS placard for mixed loads, no placard for Division 6.2 (opened 27 September 2026), and the POISON INHALATION HAZARD placard added for any material toxic by inhalation (172.505(a), opened 28 September 2026).
• 49 CFR 172.334, identification numbers, prohibited display (eCFR text as of 1 September 2026). No ID number on RADIOACTIVE, EXPLOSIVES, DANGEROUS or subsidiary hazard placards; opened 27 September 2026.
• Placardset's grader. Every example on this page is computed by the drill's own data and grading at build time, and pinned by a test.