Criteria

The heading of Class 4.3 covers substances which react with water to emit flammable gases liable to
form explosive mixtures with air, and articles containing such substances.

Substances and articles of Class 4.3 are subdivided as follows:
W Substances which, in contact with water, emit flammable gases, without subsidiary risk, and
articles containing such substances:
W1 Liquid;
W2 Solid;
W3 Articles;
WF1 Substances which, in contact with water, emit flammable gases, liquid, flammable;
WF2 Substances which, in contact with water, emit flammable gases, solid, flammable;
WS Substances which, in contact with water, emit flammable gases, solid, self-heating;
WO Substances which, in contact with water, emit flammable gases, oxidizing, solid;
WT Substances which, in contact with water, emit flammable gases, toxic:
WT1 Liquid;
WT2 Solid;
WC Substances which, in contact with water, emit flammable gases, corrosive:
WC1 Liquid;
WC2 Solid;
WFC Substances which, in contact with water, emit flammable gases, flammable, corrosive.

Properties

Certain substances in contact with water may emit flammable gases that can form explosive mixtures
with air. Such mixtures are easily ignited by all ordinary sources of ignition, for example naked lights,
sparking handtools or unprotected lamps. The resulting blast wave and flames may endanger people
and the environment. The test method referred to in 2.2.43.1.4 below is used to determine whether the
reaction of a substance with water leads to the development of a dangerous amount of gases which
may be flammable. This test method shall not be applied to pyrophoric substances.

Classification

Substances and articles classified in Class 4.3 are listed in Table A of Chapter 3.2. The assignment of
substances and articles not mentioned by name in Table A of Chapter 3.2 to the relevant entry of
2.2.43.3 in accordance with the provisions of Chapter 2.1 shall be based on the results of the test
procedure in accordance with the Manual of Tests and Criteria, Part III, Section 33.4; experience shall
also be taken into account when it leads to a more stringent assignment.

When substances not mentioned by name are assigned to one of the entries listed in 2.2.43.3 on the
basis of the test procedure in accordance with the Manual of Tests and Criteria, Part III, Section 33.4,
the following criteria shall apply:
A substance shall be assigned to Class 4.3 if:
(a) spontaneous ignition of the gas emitted takes place in any step of the test procedure; or
(b) there is an evolution of flammable gas at a rate greater than 1 litre per kilogram of the
substance to be tested per hour.
NOTE: Since organometallic substances can be classified in Class 4.2 or 4.3 with additional
subsidiary risks, depending on their properties, a specific classification flow chart for these
substances is given in 2.3.5.

 

If substances of Class 4.3, as a result of admixtures, come into different categories of risk from those
to which the substances mentioned by name in Table A of Chapter 3.2 belong, these mixtures shall be
assigned to the entries to which they belong on the basis of their actual degree of danger.
NOTE: For the classification of solutions and mixtures (such as preparations and wastes) see also
2.1.3.

On the basis of the test procedures in accordance with the Manual of Tests and Criteria, Part III,
Section 33.4, and the criteria set out in paragraph 2.2.43.1.5, it may also be determined whether the
nature of a substance mentioned by name is such that the substance is not subject to the provisions for
this Class.

Assignment of packing groups

Substances and articles classified under the various entries in Table A of Chapter 3.2 shall be assigned
to packing groups I, II or III on the basis of test procedures of the Manual of Tests and Criteria, Part
III, section 33.4, in accordance with the following criteria:
(a) Packing group I shall be assigned to any substance which reacts vigorously with water at
ambient temperature and generally demonstrates a tendency for the gas produced to ignite
spontaneously, or one which reacts readily with water at ambient temperatures such that the
rate of evolution of flammable gas is equal to or greater than 10 litres per kilogram of
substance over any one minute period;
(b) Packing group II shall be assigned to any substance which reacts readily with water at ambient
temperature such that the maximum rate of evolution of flammable gas is equal to or greater
than 20 litres per kilogram of substance per hour, and which does not meet the criteria of
packing group I;
(c) Packing group III shall be assigned to any substance which reacts slowly with water at ambient
temperature such that the maximum rate of evolution of flammable gas is greater than 1 litre
per kilogram of substance per hour, and which does not meet the criteria of
packing groups I or II.

Substances not accepted for carriage

Water-reactive solids, oxidizing, assigned to UN No. 3133 shall not be accepted for carriage unless
they meet the requirements for Class 1 (see also 2.1.3.7).

List of collective entries

a Metals and metal alloys which, in contact with water, do not emit flammable gases and are not pyrophoric or
self-heating, but which are readily flammable, are substances of Class 4.1. Alkaline-earth metals and alkaline-earth
metal alloys in pyrophoric form are substances of Class 4.2 Dust and powders of metals in pyrophoric form are
substances of Class 4.2. Metals and metal alloys in pyrophoric form are substances of Class 4.2. Compounds of
phosphorus with heavy metals such as iron, copper, etc. are not subject to the provisions of ADR.
b Metals and metal alloys in pyrophoric form are substances of Class 4.2.
c Chlorosilanes, having a flash-point of less than 23 °C and which, in contact with water, do not emit flammable
gases, are substances of Class 3. Chlorosilanes, having a flash-point equal to or greater than 23 °C and which, in
contact with water, do not emit flammable gases, are substances of Class 8.

 

Class 5.1 Oxidizing substances

Criteria

The heading of Class 5.1 covers substances which, while in themselves not necessarily combustible,
may, generally by yielding oxygen, cause or contribute to the combustion of other material, and
articles containing such substances.

The substances of Class 5.1 and articles containing such substances are subdivided as follows:
O Oxidizing substances without subsidiary risk or articles containing such substances:
O1 Liquid;
O2 Solid;
O3 Articles;
OF Oxidizing substances, solid, flammable;
OS Oxidizing substances, solid, self-heating;
OW Oxidizing substances, solid which, in contact with water, emit flammable gases;
OT Oxidizing substances, toxic:
OT1 Liquid;
OT2 Solid;
OC Oxidizing substances, corrosive:
OC1 Liquid;
OC2 Solid;
OTC Oxidizing substances, toxic, corrosive.
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