The important considerations to be taken into account in the development of test methods and in the preparation of Test Procedures are described in this Guide. Suggestions are included concerning aging temperatures@ environmental conditioning@ and the reporting of test results. The objective of the Test Procedures is to provide methods for determining the relative thermal life of insulating materials. The data obtained should provide the basis for establishing temperature classifications for materials. The thermal life values of the materials tested should provide preliminary data which can be used in selecting insulating materials for electric equipment. Test Procedures should also provide methods for determining the rate at which the important properties of materials deteriorate with thermal aging. To perform satisfactorily@ insulating materials must have the required combination of physical@ chemical@ and dielectric properties. These properties should be evaluated separately by test methods not within the scope of these Test Procedures. These Test Procedures are intended to determine the changes in properties of materials caused by thermal aging. Purpose The purpose of this Guide is to establish principles for the development of Test Procedures for the thermal evaluation of electrical insulating materials and simple combinations of materials used in rotating electric machines@ transformers@ and other types of electric equipment. The results of accelerated thermal life tests conducted in accordance with Test Procedures should be used to assign new insulating materials to appropriate temperature classes. A Test Procedure should be developed for each important kind of insulating material such as wire enamel@ sheet insulation@ etc. The results of tests on familiar@ widely-used materials should be compiled for convenient reference so that comparisons between new and old materials can readily be made. For a detailed discussion of the principles on which this Guide is based see AIEE Standard No. 1.