Class 1: Explosives — Six subclasses.

1.1 — Explosives with a mass explosion hazard. (nitroglycerin/dynamite)

1.2 — Explosives with a blast/projection hazard.

1.3 — Explosives with a minor blast hazard. (rocket propellant, display fireworks)

1.4 — Explosives with a major fire hazard. (consumer fireworks, ammunition)

1.5 — Blasting agents.

1.6 — Extremely insensitive explosives.

Class 2: Compressed Gases — Three subclasses.

2.1 — Flammable gases. (propane, hydrogen)

2.2 — Non-flammable gases. (helium, nitrogen)

2.3 — Poison gases. (chlorine, phosgene)

Class 3: Flammable Liquids — Liquids with a flash point at or below 140 °F (gasoline, some alcoholic beverages)

Combustible Liquids — Liquids with a flash point between 140 and 200 °F

Class 4: Flammables — Three subclasses.

4.1 — Flammable solids. (magnesium powder, red phosphorus, etc.)

4.2 — Spontaneously combustible materials. (white phosphorus)

4.3 — Water reactive materials. (sodium, potassium)

Class 5: Oxidizing Materials — Two subclasses.

5.1 — Oxidizers. (ammonium nitrate, hydrogen peroxide)

5.2 — Organic peroxides. (benzoyl peroxide)

Class 6: Toxic Materials — Three subclasses.

6.1 — Poisonous liquids or solids. (potassium cyanide, mercuric chloride)

6.2 — Infectious/biohazardous substances. (anthrax, HIV)

6.3 — Liquids and solids with a lower toxicity than those in group 6.1.

Class 7: Radioactive Materials — Three subclasses.

7.1-7.3 — Radioactive I, II, III. (uranium, plutonium, radioactive waste)

Class 8: Corrosive Materials — acids and bases (sodium hydroxide, sulfuric acid)

Class 9: Miscellaneous Dangerous Goods — materials that are hazardous during transportation but do not meet the definition of any of the other hazard classes, for example dry ice in an airplane or hot asphalt.