The series of International standards covered by Parts 3-10, 3-21, 3-22, 3-23, 3-24 and 3-25 of IEC 60332 specifies methods of test for the assessment of vertical flame spread of verticallymounted bunched wires or cables, electrical or optical, under defined conditions. NOTE – For the purpose of this standard, the term "electric wire or cable" covers all insulated metallic conductor cables used for the conveyance of energy or signals. The test is intended for type approval testing. The requirements for the selection of cables for testing are given in annex A. The flame spread is measured as the extent of damage of the cable sample. This procedure may be used to demonstrate the cable’s ability to limit flame spread. This part of IEC 60332 covers category D and relates only to small cables of overall diameter 12 mm or smaller installed on the test ladder to achieve a nominal total volume of non-metallic material of 0,5 l/m of test sample. The flame application time is 20 min. The method of mounting uses the front of the standard ladder in touching formation only. The category is intended for use with small cables where very low volumes of non-metallic material are required to be evaluated. A recommended performance requirement is given in annex B.