When substances or articles not mentioned by name are assigned to one of the entries listed in 2.2.42.3 on the basis of the test procedures in accordance with the Manual of Tests and Criteria, Part III, section 33.3, the following criteria shall apply:
(a) Solids liable to spontaneous combustion (pyrophoric) shall be assigned to Class 4.2 when they ignite on falling from a height of 1 m or within five minutes;
(b) Liquids liable to spontaneous combustion (pyrophoric) shall be assigned to Class 4.2 when:
(i) on being poured on an inert carrier, they ignite within five minutes, or
(ii) in the event of a negative result of the test according to (i), when poured on a dry, indented filter paper (Whatman No. 3 filter), they ignite or carbonize it within five minutes;
(c) Substances in which, in a 10 cm sample cube, at 140 °C test temperature, spontaneous combustion or a rise in temperature to over 200 °C is observed within 24 hours shall be assigned to Class 4.2. This criterion is based on the temperature of the spontaneous combustion of charcoal, which is at 50 °C for a sample cube of 27 m3. Substances with a temperature of spontaneous combustion higher than 50 °C for a volume of 27 m3 are not to be assigned to Class 4.2.
NOTE 1: Substances carried in packages with a volume of not more than 3 m3 are exempted from Class 4.2 if, tested with a 10 cm sample cube at 120 °C, no spontaneous combustion nor a rise in temperature to over 180 °C is observed within 24 hours.
NOTE 2: Substances carried in packages with a volume of not more than 450 litres are exempted from Class 4.2 if, tested with a 10 cm sample cube at 100 °C, no spontaneous combustion nor a rise in temperature to over 160 °C is observed within 24 hours.
NOTE 3: Since organometallic substances can be classified in Class 4.2 or 4.3 with additional subsidiary hazards, depending on their properties, a specific classification flow chart for these substances is given in 2.3.5.
If substances of Class 4.2, as a result of admixtures, come into different categories of hazard 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 procedure in the Manual of Tests and Criteria, Part III, section 33.3 and the criteria set out in 2.2.42.1.5, 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 33.3, in accordance with the following criteria:
(a) Substances liable to spontaneous combustion (pyrophoric) shall be assigned to packing group I;
(b) Self-heating substances and articles in which, in a 2.5 cm sample cube, at 140 °C test temperature, spontaneous combustion or a rise in temperature to over 200 °C is observed within 24 hours, shall be assigned to packing group II; Substances with a temperature of spontaneous combustion higher than 50 °C for a volume of 450 litres are not to be assigned to packing group II;
(c) Slightly self-heating substances in which, in a 2.5 cm sample cube, the phenomena referred tounder (b) are not observed, in the given conditions, but in which in a 10 cm sample cubeat140°C test temperature spontaneous combustion or a rise in temperature to over 200°C isobserved within 24hours, shall be assigned to packing group III.
Substances not accepted for carriage
The following substances shall not be accepted for carriage:
-UN No. 3255 tert-BUTYL HYPOCHLORITE; and
-Self-heating solids, oxidizing, assigned to UN No. 3127 unless they meet the requirements forClass1 (see 2.1.3.7).
List of collective entries
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a Dust and powder of metals, non toxic in a non-spontaneous combustible form which nevertheless, in contact with water, emit flammable gases, are substances of Class 4.3.
Class 4.3 Substances which, in contact with water, emit flammable gases
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 hazard, 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 withwater, 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 mayendanger people and the environment. The test method referred to in2.2.43.1.4 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. Theassignment of substances and articles not mentioned by name in Table A of Chapter3.2 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, PartIII, 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, PartIII, Section33.4, 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 thesubstance to be tested per hour.
NOTE: Since organometallic substances can be classified in Class 4.2 or 4.3 with additional subsidiary hazards, 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 hazard 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.