This International Standard provides standard composite test methods for determining the suitability of a specimen when subjected to environmental conditions consisting of a sequence of temperature, humidity and, where required, low air pressure environmental stresses. The order of application of the stresses and conditions for the change from one step to the next have been chosen to accelerate and amplify degradation mechanisms of the same type as those observed under natural climatic conditions. NOTE – Environmental conditions occurring in nature are classified in IEC 721-2 and IEC 721-3. This standard may be applied to other electrotechnical products when the degradation mechanisms are the same and the specified requirements for testing can be satisfied. In other cases, it may form a basis for the writing of a similar test. In this test, specimens are exposed to environmental tests in a standard order and categorized according to the basic code defined in Appendix A of IEC 68-1 except that the third group of digits is used as an indication of the number of cycles in Step 5 of the damp heat cyclic Test Db according to clause 6 in IEC 68-2-30. In the climatic categories -/-/56, 40/-/-, etc., in this standard the dashes may be replaced by any of the standard values appropriate to the space as in the following examples: 55/100/56, 25/085/56, 40/085/21. Where any modification is necessary, the relevant specification shall provide the necessary information for each step in the selected method (see clause 8). This test is frequently specified to follow other tests involving mechanical stress, for example tests for robustness of terminations, solderability, shock and vibration, as a means of determining whether the sealing of the specimen has been damaged.