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2.21 (1) Class 4 has three divisions:
(a) Class 4.1, Flammable Solids, which consists of substances that are
(i) readily combustible, as determined in accordance with section 2.4.2.2 of Chapter 2.4 of the UN Recommendations,
(ii) under normal conditions of transport, liable to cause fire through friction,
(iii) solid desensitized explosives, which are solid explosives desensitized through wetting with water or alcohols or diluted with other substances to form a homogeneous solid mixture to suppress their explosive properties so that they are not included in Class 1, Explosives,
(iv) self-reactive substances that are liable to undergo a strongly exothermic decomposition even without the participation of oxygen (air), as determined in accordance with section 2.4.2.3 of Chapter 2.4 of the UN Recommendations, but Class 4.1 does not include substances that have
(A) a primary class of Class 1, Explosives, Class 5.1, Oxidizing Substances, or Class 5.2, Organic Peroxides,
(B) a heat of decomposition less than 300 J/g, or
(C) a self-accelerating decomposition temperature (SADT) that is greater than 75°C for a 50 kg means of containment, as determined in accordance with section 2.4.2.3.4 of Chapter 2.4 of the UN Recommendations,
(iv.1) polymerizing substances that, without stabilization, are liable to undergo a strongly exothermic reaction resulting in the formation of larger molecules or resulting in the formation of polymers under conditions normally encountered in transport,
(v) identified by one of the following UN numbers: UN2956, UN3241, UN3242 or UN3251, or
(vi) are in the list of currently assigned self-reactive substances in section 2.4.2.3.2.3 of Chapter 2.4 of the UN Recommendations;
(b) Class 4.2, Substances Liable to Spontaneous Combustion, which consists of
(i) pyrophoric substances that spontaneously ignite within 5 minutes after coming into contact with air, as determined in accordance with section 2.4.3.2 of Chapter 2.4 of the UN Recommendations, and
(ii) self-heating substances that, when in large amounts (kilograms), spontaneously ignite on contact with air after long periods (hours or days), as determined in accordance with section 2.4.3.2 of Chapter 2.4 of the UN Recommendations; and
(c) Class 4.3, Water-reactive Substances, which consists of substances that, in tests performed in accordance with section 2.4.4.2 of Chapter 2.4 of the UN Recommendations, emit a flammable gas at a rate greater than 1 L/kg of substance per hour or spontaneously ignite at any step in the test procedure.
(2) For the purposes of subparagraph (1)(a)(iv.1), a substance is considered to be a polymerizing substance of Class 4.1 if it
(a) has a self-accelerating polymerization temperature (SAPT) that is less than or equal to 75°C under the conditions in which the substance or mixture is to be transported, with or without chemical stabilization as offered for transport, and in the means of containment in which the substance or mixture is to be transported;
(b) exhibits a heat of reaction of more than 300 J/g; and
(c) does not meet any other criteria for inclusion in Classes 1 to 8.
SOR/2017-137, s. 20