Specifies a numerical system of classifying materials and systems based on their thermal endurance, ranging from Class 90 to Class 250 (in nine steps) thereafter in steps of 25, the figure indicating the assigned Celsius temperature. Retains the AS C320 alphabetical classifications Y, A, E, B, F and H (but not C) as an alternative for the time being. Describes the evaluation of long-term thermal properties of materials and of more complex insulation systems, and the influence of service conditions. Also defines the responsibility for assigning thermal identification and classification. Is based on, but differs from IEC 85 (1984) which specifies a part-alphabetical part-numerical system of classification and which permits alternative systems of identification of materials used in certain products.