The nine classes of dangerous goods
Every dangerous good is assigned to one of nine classes according to the hazard it presents, and several classes are split into divisions. The class is what drives the label, the packaging standard, the documentation, and (more often than shippers expect) whether a carrier will take the parcel at all. A material can also carry a subsidiary risk from a second class, which is why a bottle of methanol needs both a flammable liquid and a toxic label.
Class 1 — Explosives
2 entries encodedSubstances and articles that present a mass explosion, projection, fire or minor blast hazard.
Division 2.1 — Flammable gas
3 entries encodedGases ignitable at 20 °C and standard pressure, including aerosols with a flammable propellant.
Division 2.2 — Non-flammable, non-toxic gas
5 entries encodedCompressed, liquefied and refrigerated gases that are neither flammable nor toxic.
Division 2.3 — Toxic gas
0 entries encodedGases known to be toxic or corrosive to humans at low concentrations.
Class 3 — Flammable liquids
15 entries encodedLiquids with a flash point at or below 60 °C, the largest class in consumer shipping.
Division 4.1 — Flammable solids
3 entries encodedReadily combustible solids, self-reactive substances and desensitised explosives.
Division 4.2 — Spontaneously combustible
1 entry encodedSubstances liable to spontaneous heating or ignition in contact with air.
Division 4.3 — Dangerous when wet
0 entries encodedSubstances that emit flammable gases on contact with water.
Division 5.1 — Oxidizers
4 entries encodedSubstances that yield oxygen and so intensify the combustion of other material.
Division 5.2 — Organic peroxides
1 entry encodedThermally unstable substances typed A to G, many requiring temperature control.
Division 6.1 — Toxic substances
2 entries encodedSubstances liable to cause death or serious injury on ingestion, inhalation or skin contact.
Division 6.2 — Infectious substances
1 entry encodedSubstances known or reasonably expected to contain pathogens.
Class 7 — Radioactive material
0 entries encodedMaterial with a specific activity above the exempt values in 49 CFR 173.436.
Class 8 — Corrosives
10 entries encodedSubstances that destroy skin tissue or corrode steel or aluminium at a defined rate.
Class 9 — Miscellaneous
17 entries encodedDangerous goods that present a hazard not covered by the other classes, including lithium batteries and dry ice.