Complete Guide to Dangerous Goods Classes 1–9

Nine classes. Dozens of sub-divisions. Hundreds of UN numbers. The DG classification system can feel overwhelming at first, but once you understand the logic behind it, it becomes surprisingly navigable.

Here's a practical breakdown of all nine classes — focused on what Indian shippers and exporters actually encounter.

Class 1 — Explosives

Six divisions, from 1.1 (mass explosion hazard, like dynamite) to 1.6 (extremely insensitive articles). In commercial air freight from India, Class 1 is rare. Fireworks, pyrotechnic devices, safety fuses, and certain ammunition are the typical items. All require DGCA permits and are usually restricted to cargo aircraft only. Most airlines decline them entirely unless pre-arranged.

Class 2 — Gases

Three types: flammable (like LPG, butane), non-flammable non-toxic (nitrogen, argon, CO2), and toxic (chlorine, ammonia). Aerosols also fall under Class 2. The main practical issue for Indian exporters: fire extinguishers, gas cylinders, and camping stoves are Class 2, and they come up frequently in e-commerce exports. Each has specific quantity limits and PI requirements.

Class 3 — Flammable Liquids

This is one of the busiest DG classes in air freight. Paint, adhesives, perfumes, hand sanitiser (above 24% alcohol), solvents, and fuels are all here. The flash point determines packing group. Below 23°C = PG I or II. 23°C to 60°C = PG III. Above 60°C is generally not Class 3 at all. Perfume exporters from India need to pay close attention here — many luxury fragrance shipments trigger Class 3 requirements.

Class 4 — Flammable Solids, Self-Reactives, and Pyrophorics

Three divisions: 4.1 (flammable solids, including matches and desensitised explosives), 4.2 (spontaneously combustible — catches fire in air), and 4.3 (dangerous when wet — reacts with water to produce flammable gas). White phosphorus and certain metal powders are 4.2 and 4.3 respectively. These are relatively uncommon in general export but critical to recognise when present.

Class 5 — Oxidising Substances and Organic Peroxides

Oxidisers (5.1) accelerate combustion — hydrogen peroxide, ammonium nitrate, bleaching powder. Organic peroxides (5.2) are both oxidisers and potential fuels. Organic peroxides often need temperature control during transport, adding another layer of complexity. Hair bleaches, certain industrial chemicals, and textile treatment agents fall here.

Class 6 — Toxic and Infectious Substances

Division 6.1 is toxic substances — poisons, pesticides, heavy metal compounds. Division 6.2 is infectious substances: Category A (can cause permanent disability or fatal disease — Ebola, anthrax) and Category B (diagnostic samples, patient specimens). The distinction between Category A and B determines the packaging specification dramatically. Getting this wrong isn't just a regulatory problem — it's a public health risk.

Class 7 — Radioactive Material

The most heavily regulated class. Medical isotopes, industrial gauges, and research samples. Requires AERB and DGCA clearance in India. Type A and Type B packages, transport indices, radiation level labels — all specific to the isotope and activity level. We have a full dedicated article on this if you're shipping Class 7.

Class 8 — Corrosives

Battery acid (sulphuric acid), caustic soda, hydrochloric acid, and many industrial cleaning agents. Corrosives are defined by their ability to irreversibly damage skin or steel. Packing group is based on the degree of that damage. Wet cell batteries are Class 8. A common surprise for Indian exporters: certain eco-friendly cleaning products still qualify as Class 8 depending on pH.

Class 9 — Miscellaneous Dangerous Goods

Everything that doesn't fit neatly elsewhere. Lithium batteries are the biggest Class 9 category in air freight. Dry ice (UN1845, used for cold chain) is Class 9. Magnetised material, elevated temperature substances, and environmentally hazardous substances (marine pollutants) are also Class 9. Don't underestimate this class — it generates more cargo rejections than most others simply because shippers don't recognise it as DG at all.