The classes of dangerous goods according to ADR are the following:
Class 1 Explosive substances and articles
Class 2 Gases
Class 3 Flammable liquids
Class 4.1 Flammable solids, self-reactive substances, polymerizing substances and solid
desensitized explosives
Class 4.2 Substances liable to spontaneous combustion
Class 4.3 Substances which, in contact with water, emit flammable gases
Class 5.1 Oxidizing substances
Class 5.2 Organic peroxides
Class 6.1 Toxic substances
Class 6.2 Infectious substances
Class 7 Radioactive material
Class 8 Corrosive substances
Class 9 Miscellaneous dangerous substances and articles

Each entry in the different classes has been assigned a UN number. The following types of entries are
A. Single entries for well defined substances or articles including entries for substances covering
several isomers, e.g.:
B. Generic entries for a well defined group of substances or articles, which are not n.o.s. entries,
C. Specific n.o.s. entries covering a group of substances or articles of a particular chemical or
technical nature, not otherwise specified, e.g.:
UN No. 1987 ALCOHOLS, N.O.S.
D. General n.o.s. entries covering a group of substances or articles having one or more dangerous
properties, not otherwise specified, e.g.:
The entries defined under B., C. and D. are defined as collective entries.

For packing purposes, substances other than those of Classes 1, 2, 5.2, 6.2 and 7, and other than selfreactive
substances of Class 4.1 are assigned to packing groups in accordance with the degree of
danger they present:
Packing group I: Substances presenting high danger;
Packing group II: Substances presenting medium danger;
Packing group III: Substances presenting low danger.
The packing group(s) to which a substance is assigned is (are) indicated in Table A of Chapter 3.2.
Articles are not assigned to packing groups. For packing purposes any requirement for a specific
packaging performance level is set out in the applicable packing instruction.


Principles of classification

The dangerous goods covered by the heading of a class are defined on the basis of their properties
according to sub-section 2.2.x.1 of the relevant class. Assignment of dangerous goods to a class and a
packing group is made according to the criteria mentioned in the same sub-section 2.2.x.1.
Assignment of one or several subsidiary risk(s) to a dangerous substance or article is made according
to the criteria of the class or classes corresponding to those risks, as mentioned in the appropriate subsection(
s) 2.2.x.1.

All dangerous goods entries are listed in Table A of Chapter 3.2 in the numerical order of their UN
Number. This table contains relevant information on the goods listed, such as name, class, packing
group(s), label(s) to be affixed, packing and carriage provisions1. The substances listed by name in
column (2) of Table A of Chapter 3.2 shall be carried according to their classification in Table A or
under the conditions specified in

A substance may contain technical impurities (for example those deriving from the production
process) or additives for stability or other purposes that do not affect their classification. However, a
substance mentioned by name, i.e. listed as a single entry in Table A of Chapter 3.2, containing
technical impurities or additives for stability or other purposes affecting its classification shall be
considered a solution or mixture (see

Dangerous goods which are listed or defined in sub-section 2.2.x.2 of each class are not to be accepted
for carriage.

Goods not mentioned by name, i.e. goods not listed as single entries in Table A of Chapter 3.2 and not
listed or defined in one of the above-mentioned sub-sections 2.2.x.2 shall be assigned to the relevant
class in accordance with the procedure of section 2.1.3. In addition, the subsidiary risk (if any) and the
packing group (if any) shall be determined. Once the class, subsidiary risk (if any) and packing group
(if any) have been established the relevant UN number shall be determined. The decision trees in subsections
2.2.x.3 (list of collective entries) at the end of each class indicate the relevant parameters for
selecting the relevant collective entry (UN number). In all cases the most specific collective entry
covering the properties of the substance or article shall be selected, according to the hierarchy
indicated in by the letters B, C and D respectively. If the substance or article cannot be
classified under entries of type B or C according to, then, and only then shall it be classified
under an entry of type D.

On the basis of the test procedures of Chapter 2.3 and the criteria set out in sub-sections 2.2.x.1 of
classes when it is so specified, it may be determined that a substance, solution or mixture of a certain
class, mentioned by name in Table A of Chapter 3.2, does not meet the criteria of that class. In such a
case, the substance, solution or mixture is deemed not to belong to that class.

For the purposes of classification, substances with a melting point or initial melting point of 20 °C or
lower at a pressure of 101.3 kPa shall be considered to be liquids. A viscous substance for which a
specific melting point cannot be determined shall be subjected to the ASTM D 4359-90 test or to the
test for determining fluidity (penetrometer test) prescribed in 2.3.4.

A consignor who has identified, on the basis of test data, that a substance listed by name in column 2
of Table A of Chapter 3.2 meets classification criteria for a class that is not identified in column 3a or
5 of Table A of Chapter 3.2, may, with the approval of the competent authority, consign the
– Under the most appropriate collective entry listed in sub-sections 2.2.x.3 reflecting all hazards;
– Under the same UN number and name but with additional hazard communication information
as appropriate to reflect the additional subsidiary risk(s) (documentation, label, placard)
provided that the class remains unchanged and that any other carriage conditions (e.g. limited
quantity, packaging and tank provisions) that would normally apply to substances possessing
such a combination of hazards are the same as those applicable to the substance listed.
NOTE 1: The competent authority granting the approval may be the competent authority of any
ADR Contracting Party who may also recognize an approval granted by the competent authority of a
country which is not an ADR Contracting Party provided that this approval has been granted in
accordance with the procedures applicable according to RID, ADR, ADN, the IMDG Code or the
ICAO Technical Instructions.
NOTE 2: When a competent authority grants such approvals, it should inform the United Nations
Sub-Committee of Experts on the Transport of Dangerous Goods accordingly and submit a relevant
proposal of amendment to the Dangerous Goods List of the UN Model Regulations. Should the
proposed amendment be rejected, the competent authority should withdraw its approval.
NOTE 3: For carriage in accordance with, see also


Classification of substances, including solutions and mixtures (such as preparations and wastes), not mentioned by name

Substances including solutions and mixtures not mentioned by name shall be classified according to
their degree of danger on the basis of the criteria mentioned in sub-section 2.2.x.1 of the various
classes. The danger(s) presented by a substance shall be determined on the basis of its physical and
chemical characteristics and physiological properties. Such characteristics and properties shall also be
taken into account when such experience leads to a more stringent assignment.
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