This part of ISO 9022 specifies the methods relating to the environmental tests of optical instruments including additional assemblies from other fields (e.g. mechanical, chemical, and electronic devices), under equivalent conditions, for their ability to resist the influence of low air pressure combined with cold, including the potential condensation and freezing of water, ambient temperature, and dry or damp heat. This part of ISO 9022 is applicable to optical instruments including additional assemblies from other fields, designed for operation and/or transport in high mountainous areas or on board aircraft or missiles. The purpose of the testing is to investigate to what extent optical, climatic, mechanical, chemical, and electrical (including electrostatic) performance characteristics of the specimen are affected by combined low pressure and low, ambient, or high temperature. Furthermore, the additional effects of water condensing and freezing on the instrument or components can be determined. Examples are instruments which are installed or externally mounted on aircraft or missiles or transported inside aircraft or flying objects not providing any pressure equalization. Annex A explains the intent of the different types of tests.