This document has been prepared as a guide for technical committees to use when standards are being prepared or revised, with the object of obtaining consistency, as far as practicable, among the standards for various kinds of electric equipment, which must often operate under the same service conditions. Service conditions are specified to give the limiting conditions of operation for which standard equipment is designed. For example, ambient temperature values should be selected which, in combination with standard temperature rises, limit total insulation temperatures to suitable values. By specifying a limiting ambient value in service conditions, a readily usable simple means of stating conditions for which standard ratings are suitable is provided. This document consists of two parts. As far as possible selections should be made from Part I for the statement of service conditions for particular equipment standards. For uniformity it is suggested that the exact wording be used where it applies. Part II covers application and testing. Selections from this part are recommended for inclusion as supplementary information to specific standards where applicable and desirable.