Specifies the test apparatus to be used for testing cables required to maintain circuit integrity when subject to fire and mechanical shock where the test condition is based upon a flame with a controlled heat output corresponding to a temperature of a nominal 850 C. It is intended for use when testing cables of greater than 20 mm overall diameter. It also provides, in annex A, the method of verification of the burner and control system used for the test. Has the status of a group safety publication in accordance with IEC Guide 104. Mike Hagger, Secretary of IEC Technical Committee 20 (Electric cables) explains that "IEC 60331-12 and IEC 60331-31 (see below) introduce for the first time in IEC work a test method for checking the circuit integrity of electric cables under fire conditions when subject to fire and mechanical shock. They provide a method suitable for all sizes of cable and are particularly useful for testing cables greater than 20mm overall diameter for which the existing IEC 60331-11 and IEC 60331-21 have limitations." Hagger adds that "these publications address concerns expressed by users, manufacturers and fire specialists that the provision of mechanical shock and a larger, higher temperature flame source, compared with IEC 60331-11, is necessary to ensure the suitability of fire resistant cables for certain critical applications."