Self-heating substances and mixtures

A self-heating substance or mixture is a solid or liquid substance or mixture, other than a pyrophoric liquid or solid, which, by reaction with air and without energy supply, is liable to self-heat this substance or mixture differs from a pyrophoric liquid or solid in that it will ignite only when in large amounts (kilograms) and after long periods of time (hours or days). 

NOTE Self-heating of substances or mixtures, leading to spontaneous combustion, is caused by 

1 A substance or mixture shall be classified as a self-heating substance of this class, if in tests performed in accordance with the test method given in the UN Recommendations on the Transport of Dangerous Goods, Manual of Tests and Criteria, Part III, sub-section 33.3.1.6  

1 A positive result is obtained in a test using a 25 mm sample cube at 140 °C 

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Table 2.11.1 Criteria for self-heating substances and mixtures... 

Self-heating substances and mixtures (See Chapter 2.11 for details)... 

C4.24 SELF-HEATING SUBSTANCES AND MIXTURES (Classified in Accordance with Appendix B.11)... 

Capable of igniting and burning in air without the presence of an ignition source. Pyrophoric materials are spontaneously combustible, although some pyrophorics require the presence of a minimum amount of moisture (humidity) to spontaneously ignite. Other spontaneously combustible substances and mixtures may require more time or an insulating environment to self-heat to the point of ignition. 

NOTE Flammable components do not cover pyrophoric, self-heating or water-reactive substances and mixtures because such components are never used as aerosol contents. 

Furthermore a radioactive source may heat up by self-absorption so that the ignition temperature of the surrounding explosible atmosphere is exceeded. By impact with ionizing radiation explosible substances and mixtures, especially if highly reactive radicals are formed, may be produced. The causes are radiolysis and chemical decomposition which thus create further explosion hazards. ... 

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