Free Tool · CDL Hazmat

Hazmat Placard Lookup

Search supported common UN numbers to review the stored hazard class, shipping name, packing group, placard, and hazard description. This finite lookup is a supplemental study aid, not a shipping decision tool.

UN Number

Enter 4-digit UN number only (e.g. 1203 for Gasoline)

Common UN Numbers

How DOT Hazmat Placards Work

DOT hazmat placards are diamond-shaped warning signs required on vehicles transporting hazardous materials in quantities at or above specified thresholds. Federal regulations (49 CFR 172 Subpart F) require placards based on hazard class and quantity. For most hazard classes (Table 2), placards are required when the aggregate gross weight of hazardous materials on the vehicle is 1,001 lbs or more. Table 1 materials — Explosives 1.1, 1.2 and 1.3, Poison Gas 2.3, Dangerous When Wet 4.3, Organic Peroxide 5.2 (Type B, temperature controlled), Poison Inhalation Hazard 6.1 (Zone A/B), and Radioactive Yellow III — require placards in any quantity.

Each UN number uniquely identifies a hazardous material and maps to a hazard class, proper shipping name, and packing group. The packing group (I, II, or III) indicates the degree of hazard within a class: PG I is the greatest danger, PG III is the least. Not all materials have a packing group — gases are not packing group classified.

Use the lookup as supplemental practice with supported common UN numbers. For current transportation decisions, confirm the material classification, packaging, quantity, and placarding requirements in the applicable official rules and shipping documents.

Official references · checked October 1, 2026

eCFR — 49 CFR 172.504 placarding requirements ↗PHMSA — 2024 Emergency Response Guidebook ↗

Frequently Asked Questions

How many DOT hazmat hazard classes are there?

There are 9 DOT hazard classes: Class 1 (Explosives), Class 2 (Gases), Class 3 (Flammable Liquids), Class 4 (Flammable Solids), Class 5 (Oxidizers/Organic Peroxides), Class 6 (Poisons/Infectious Substances), Class 7 (Radioactive Materials), Class 8 (Corrosives), and Class 9 (Miscellaneous Dangerous Goods). Some classes have sub-divisions — explosives, for example, have divisions 1.1 through 1.6.

What is the difference between a UN number and an NA number?

UN numbers are international identifiers recognized by the United Nations. NA numbers are North America-only identifiers used for materials not assigned a UN number or for specific domestic use. Most common hazmat materials use UN numbers; NA numbers appear only in US and Canadian regulations.

When is a placard required vs. just a label?

Labels go on individual packages and are required regardless of quantity. Placards go on the vehicle. Table 1 materials must be placarded in any amount: Divisions 1.1, 1.2 and 1.3 explosives, Division 2.3 poison gas, Division 4.3 dangerous when wet, Division 5.2 organic peroxide (Type B, temperature controlled), Division 6.1 poison inhalation hazard (Zone A/B), and Class 7 Radioactive Yellow III. Table 2 materials (every other class) in non-bulk packages need placards only when their aggregate gross weight on the vehicle is 1,001 lbs (454 kg) or more. Bulk packages are placarded at any quantity.

When can you use the DANGEROUS placard?

The DANGEROUS placard may replace the separate Table 2 placards when a vehicle carries non-bulk packages of two or more Table 2 hazard categories. It cannot be used for Table 1 materials. And if 2,205 lbs (1,000 kg) or more of one Table 2 category is loaded at a single facility, that category's specific placard must be displayed; DANGEROUS may still cover the remaining Table 2 categories.

What is the ERG and why does it matter for the CDL Hazmat exam?

The Emergency Response Guidebook (ERG) is published by PHMSA and provides first-responder guidance for hazmat incidents. Drivers must carry shipping papers and know how to locate the ERG guide page for their load. The CDL Hazmat exam tests your ability to read shipping papers, identify the hazard class, and find the correct ERG response guide.