The 9 DOT/UN hazard classes: official placard color for each and real material examples
The US hazmat placarding system is defined by 49 CFR Part 172, Subpart F (the Department of Transportation's regulation), and is harmonized with the UN Recommendations on the Transport of Dangerous Goods, the same base Brazil follows through ABNT NBR 7500. The nine hazard classes (1 through 9) use color, the diamond shape and, where applicable, a standardized pictogram to communicate the primary hazard at a distance, without relying on text or language. Colors and split designs are fixed by regulation and cannot be approximated from memory: Class 8 (Corrosive), for instance, is white on top and black on the bottom, the reverse of what many people remember,, Class 4.2 (liable to spontaneous combustion) is white on top and red on the bottom, and Class 5.2 (organic peroxide) is red on top and yellow on the bottom. Division 6.2 (infectious substance) does not even require a vehicle placard for domestic US transport (49 CFR 172.500(b)(1)); the diamond shown here for it is the UN/international label design, used on the package itself. This tool gathers all 9 classes and their key subdivisions with the official color, the regulatory category name and real examples of materials commonly shipped under each.
Every placard is a diamond (a square rotated 45°) at least 250 mm on each side, with a fixed background color per class, an inner border, a pictogram near the top and the class number at the bottom point. When two colors appear, the diamond is split exactly in half by the horizontal line through its left and right points, which is why the 49 CFR sections themselves describe each half as a 'triangle': that's simply the geometry of a diamond cut across the middle.
A few classes use vertical stripes instead of halves: Class 4.1 (flammable solid) has seven red stripes on a white background, with one red stripe exactly centered; Class 9 (miscellaneous) has seven black stripes only on the upper half, with the lower half plain white and the numeral '9' underlined at the bottom point, it's the only class whose numeral is underlined by regulation.
Three combinations are frequently remembered in reverse. Class 8 (Corrosive) is white on top and black on the bottom, not the other way around. Class 4.2 (spontaneous combustion) is white on top and red on the bottom. Class 5.2 (organic peroxide) flips that logic: red on top and yellow on the bottom. Class 7 (radioactive) follows the pattern most people already remember correctly: yellow on top, white on the bottom, with a black trefoil.
Worth noting too: Class 2.1 (flammable gas) and Class 2.2 (non-flammable gas) are solid-color placards, red and green respectively, with no color split at all, even though people who have never seen them side by side sometimes assume they're divided.
Paste the code into your HTML and the tool shows up on your page, without J-Kit's navigation and ads. It still runs in the browser of whoever visits your site.
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src="https://jkit.tools/embed/en-US/hazmat-placards"
width="100%"
height="600"
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loading="lazy"
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></iframe>These references help contextualize formulas, standards, APIs and limitations used on this page. They do not replace professional validation when a result has legal, financial, medical or operational impact.
Drivers and carriers of hazardous cargo, first responders (firefighters, EMS, highway patrol), dispatchers and roadside inspectors, plus students of logistics, safety engineering and dangerous-goods transport. Recognizing the color and class from a distance is the first step in deciding how to react safely near a placarded truck or railcar.
| Placard | Class | Category | Examples |
|---|---|---|---|
| 1.1 | Explosives with a mass explosion hazard | TNT · Dynamite | |
| 1.2 | Explosives with a projection hazard | Detonating fuzes · Some types of military ammunition | |
| 1.3 | Explosives with a fire hazard | Smokeless powder · Display fireworks | |
| 1.4 | Explosives with no significant blast hazard | Consumer fireworks · Small-arms ammunition | |
| 1.5 | Very insensitive substances with a mass explosion hazard | Blasting agents (ANFO) · Type B mining blasting agents | |
| 1.6 | Extremely insensitive articles with no mass explosion hazard | Certified extremely insensitive detonating articles (EIDS) · Certain modern military ordnance | |
| 2.1 | Flammable gas | Propane · Butane | |
| 2.2 | Non-flammable, non-toxic gas | Compressed nitrogen · Helium | |
| 2.3 | Toxic gas | Chlorine · Phosgene | |
| 3 | Flammable liquid | Gasoline · Ethanol | |
| 4.1 | Flammable solid | Sulfur · Nitrocellulose | |
| 4.2 | Substance liable to spontaneous combustion | White phosphorus · Activated carbon (self-heating) | |
| 4.3 | Substance dangerous when wet | Sodium metal · Calcium carbide | |
| 5.1 | Oxidizing substance | Ammonium nitrate · Concentrated hydrogen peroxide | |
| 5.2 | Organic peroxide | Methyl ethyl ketone peroxide (MEKP) · Benzoyl peroxide | |
| 6.1 | Toxic substance | Potassium cyanide · Certain organophosphate pesticides | |
| 6.2 | Infectious substance | Regulated medical waste · Diagnostic specimens | |
| 7 | Radioactive material | Cobalt-60 (medical/industrial use) · Uranium ore | |
| 8 | Corrosive substance | Sulfuric acid · Sodium hydroxide (lye) | |
| 9 | Miscellaneous dangerous substances and articles | Lithium-ion batteries · Dry ice (solid carbon dioxide) |
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