Specifies the general ageing conditions and procedures to be used for deriving thermal endurance characteristics and gives guidance in using the detailed instructions and guidelines in the other parts of the standard. Simplified procedures are also given, with the conditions under which these procedures may be used. Although originally developed for use with electrical insulating materials and simple combinations of such materials, the procedures are considered to be of more general applicability and are widely used in the assessment of materials not intended for use as electrical insulation. In the application of this standard, it is assumed that a practically linear relationship exists between the logarithm of the time required to cause the predeter-mined property change and the reciprocal of the corresponding absolute temperature (Arrhenius relationship). For the valid application of the standard, no transition, in particular no first-order transition, should occur in the temperature range under study.