Each substance is assigned a Hazard number, indicating the major hazard associated with it.

2. Emission of gas due to pressure of to chemical reaction
20 Asphyxiant gas or gas with no subsidiary risk
22 Refrigerated liquefied gas, asphyxiant
223 Refrigerated liquefied gas, flammable
225 Refrigerated liquefied gas, oxidizing (fire-intensifying)
23 Flammable gas
238 Gas, flammable corrosive
239 Flammable gas, which can spontaneously lead to violent reaction
25 Oxidizing (fire-intensifying) gas
26 Toxic gas
263 Toxic gas, flammable
265 Toxic gas, oxidizing (fire-intensifying)
268 Toxic gas, corrosive
28 Gas, corrosive
3. Flammability of liquids (vapours) and gases of self-heating liquid
30 Flammable liquid (flash-point between 23 °C and 60 °C, inclusive) or flammable liquid or solid in the molten state with a flash-point above 60 °C, heated to a temperature equal to or above its flash-point, or self-heating liquid
323 Flammable liquid which reacts with water, emitting flammable gases
X323 Flammable liquid which reacts dangerously with water, emitting flammable gases
This substance will react dangerously with water
33 Highly flammable liquid (flash-point below 23 °C)
333 Pyrophoric liquid
X333 Pyrophoric liquid which reacts dangerously with water
This substance will react dangerously with water
336 Highly flammable liquid, toxic
338 Highly flammable liquid, corrosive
X338 Highly flammable liquid, corrosive, which reacts dangerously with water
This substance will react dangerously with water
339 Highly flammable liquid which can spontaneously lead to violent reaction
36 Flammable liquid (flash-point between 23 °C and 60 °C, inclusive), slightly toxic, or self-heating liquid, toxic
362 Flammable liquid, toxic, which reacts with water, emitting flammable gases
X362 Flammable liquid toxic, which reacts dangerously with water, emitting flammable gases
This substance will react dangerously with water
368 Flammable liquid, toxic, corrosive 38 flammable liquid (flash-point between 23 °C and 60 °C, inclusive), slightly corrosive or self-heating liquid, corrosive
382 Flammable liquid, corrosive, which reacts with water, emitting flammable gases
X382 Flammable liquid, corrosive, which reacts dangerously with water, emitting flammable gases1 39 flammable liquid, which can spontaneously lead to violent reaction
This substance will react dangerously with water
4. Flammability of solids or self-heating solid
40 Flammable solid, or self-reactive substance, or self-heating substance, or polymerizing substance
423 Solid which reacts with water, emitting flammable gases, or flammable solid which reacts with water, emitting flammable gases or self-heating solid which reacts with water, emitting flammable gases
X423 Solid which reacts dangerously with water, emitting flammable gases, or flammable solid which reacts dangerously with water, emitting flammable gases, or self-heating solid which reacts dangerously with water, emitting flammable gases
This substance will react dangerously with water
43 Spontaneously flammable (pyrophoric) solid
44 Flammable solid, in the molten state at an elevated temperature
446 Flammable solid, toxic, in the molten state, at an elevated temperature
46 Flammable or self-heating solid, toxic
462 Toxic solid which reacts with water, emitting flammable gases
X462 Solid which reacts dangerously with water, emitting toxic gases
This substance will react dangerously with water
48 Flammable or self-heating solid, corrosive
482 Corrosive solid which reacts with water, emitting flammable gases
X482 Solid which reacts dangerously with water, emitting corrosive gases
This substance will react dangerously with water
5. Oxisizing (fire-intensifying) effect
50 Oxidizing (fire-intensifying) substance
539 Flammable organic peroxide
55 Strongly oxidizing (fire-intensifying) substance
556 Strongly oxidizing (fire-intensifying) substance, toxic
558 Strongly oxidizing (fire-intensifying) substance, corrosive
559 Strongly oxidizing (fire-intensifying) substance, which can spontaneously lead to violent reaction
56 Oxidizing substance (fire-intensifying), toxic
568 Oxidizing substance (fire-intensifying), toxic, corrosive
58 Oxidizing substance (fire-intensifying), corrosive
59 Oxidizing substance (fire-intensifying) which can spontaneously lead to violent reaction
6. Toxicity or risk of infection
60 Toxic or slightly toxic substance
606 Infectious substance
623 Toxic liquid, which reacts with water, emitting flammable gases
63 Toxic substance, flammable (flash-point between 23 °C and 60 °C, inclusive)
638 Toxic substance, flammable (flash-point between 23 °C and 60 °C, inclusive), corrosive
639 Toxic substance, flammable (flash-point not above 60 °C) which can spontaneously lead to violent reaction
64 Toxic solid, flammable or self-heating
642 Toxic solid, which reacts with water, emitting flammable gases
65 Toxic substance, oxidizing (fire-intensifying)
66 Highly toxic substance
663 Highly toxic substance, flammable (flash-point not above 60 °C)
664 Highly toxic solid, flammable or self-heating
665 Highly toxic substance, oxidizing (fire-intensifying)
668 Highly toxic substance, corrosive
X668 Highly toxic substance, corrosive, which reacts dangerously with water
This substance will react dangerously with water
669 Highly toxic substance which can spontaneously lead to violent reaction
68 Toxic substance, corrosive
69 Toxic or slightly toxic substance, which can spontaneously lead to violent reaction
7. Radioactivity
70 Radioactive material
768 Radioactive material, toxic, corrosive
78 Radioactive material, corrosive
8. Corrosivity
80 Corrosive or slightly corrosive substance
80 Corrosive or slightly corrosive substance, which reacts dangerously with water
823 Corrosive liquid which reacts with water, emitting flammable gases
83 Corrosive or slightly corrosive substance, flammable (flash-point between 23 °C and 60 °C, inclusive)
X83 Corrosive or slightly corrosive substance, flammable, (flash-point between 23 °C and 60 °C, inclusive), which reacts dangerously with water
This substance will react dangerously with water
839 Corrosive or slightly corrosive substance, flammable (flash-point between 23 °C and 60 °C inclusive) which can spontaneously lead to violent reaction
X839 Corrosive or slightly corrosive substance, flammable (flash-point between 23 °C and 60 °C inclusive), which can spontaneously lead to violent reaction and which reacts dangerously with water
This substance will react dangerously with water
84 Corrosive solid, flammable or self-heating
842 Corrosive solid which reacts with water, emitting flammable gases
85 Corrosive or slightly corrosive substance, oxidizing (fire-intensifying)
856 Corrosive or slightly corrosive substance, oxidizing (fire-intensifying) and toxic
86 Corrosive or slightly corrosive substance, toxic
88 Highly corrosive substance
X88 Highly corrosive substance, which reacts dangerously with water
This substance will react dangerously with water
883 Highly corrosive substance, flammable (flash-point between 23 °C and 60 °C inclusive)
884 Highly corrosive solid, flammable or self-heating
885 Highly corrosive substance, oxidizing (fire-intensifying)
886 Highly corrosive substance, toxic
X886 Highly corrosive substance, toxic, which reacts dangerously with water
This substance will react dangerously with water
89 Corrosive or slightly corrosive substance, which can spontaneously lead to violent reaction
9. Risk of spontaneous violent reaction
90 Environmentally hazardous substance; miscellaneous dangerous substances
99 Miscellaneous dangerous substance carried at an elevated temperature.
ADR European Agreement Concerning the International Carriage of Dangerous Goods by Road, ECE/TRANS/257 (Vol. 1), Economic Commission for Europe Inland Transport Committee, UNECE 2017