Covers ageing assessment methods which can be applied to components based on polymeric materials (for example, cable insulation and jackets, elastomeric seals, polymeric coatings, gaiters) which are used in environments where they are exposed to radiation. The object of this part of IEC 60544 is to provide guidelines on the assessment of ageing in service. The approaches discussed cover ageing assessment programmes based on condition monitoring (CM), the use of equipment deposits in severe environments and sampling of real-time aged components.