Dangerous Goods Classes 1-9 for Shipping: UN Numbers, Packing Groups and the Rules by Mode

How dangerous goods are classified

Dangerous goods may be pure chemicals, mixtures, manufactured products or articles. The UN Recommendations on the Transport of Dangerous Goods (Model Regulations), prepared by a UN Economic and Social Council committee of experts, assign each of them to one of nine classes, some divided into divisions, and to an entry in the Dangerous Goods List with a four-digit UN number and a proper shipping name, such as UN1266 Perfumery products or UN3481 Lithium ion batteries contained in equipment.

Most entries also have a packing group showing the degree of danger: packing group I is the most dangerous, II medium and III the least. The packing group decides how strong the packaging must be and how much may go in one package. The classification is the shipper's job; for chemical products, Sections 2, 9 and 14 of the safety data sheet give the basis.

Which rules apply by transport mode

• Sea: the International Maritime Dangerous Goods (IMDG) Code, mandatory under SOLAS. Amendment 42-24 has been mandatory since 1 January 2026; it added 11 entries to the Dangerous Goods List, including sodium ion batteries and equipment containing them (UN3551 and UN3552), assigned battery-powered vehicles to class 9 and added a stowage code keeping flammable goods away from sources of ignition.
• Air: the ICAO Technical Instructions, applied by airlines through the IATA Dangerous Goods Regulations, which IATA updates every year and which shippers use to classify, mark, pack, label and document dangerous goods.
• Road and rail in Europe and beyond: ADR for road and RID for rail, and ADN for inland waterways.
• National rules, such as 49 CFR in the United States, also apply to domestic legs, and carriers may have stricter rules of their own (operator variations).

Documents, marks and labels

• A dangerous goods declaration from the shipper: for air, the Shipper's Declaration for Dangerous Goods; for sea, a dangerous goods declaration such as the multimodal dangerous goods form, with the UN number, proper shipping name, class, packing group, quantities and emergency information.
• UN specification packaging tested for the packing group, unless the goods are shipped under limited or excepted quantity provisions.
• Marks and labels on each package: the UN number and proper shipping name and the class hazard label, and for sea, placards and marks on the container.
• The safety data sheet, which carriers and forwarders ask for to check the classification.
• Training: people who prepare dangerous goods shipments must be trained under the rules of each mode.

Everyday products exporters often miss

• Perfumes and other alcohol-based cosmetics: often UN1266, class 3.
• Aerosol sprays: UN1950, class 2.
• Lithium batteries, alone or in or with equipment: UN3480, UN3481, UN3090 or UN3091, class 9; sodium ion batteries: UN3551 and UN3552.
• Paints and nail polish with flammable solvents: often class 3.
• Dry ice used to keep goods cold: UN1845, class 9.
• Magnetized material for air transport: UN2807, class 9.
• Small quantities may be shipped under limited or excepted quantity rules, but they are still dangerous goods and must be declared and marked as those rules require.