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 contamination, i.e. contact with corrosive chemical substances (hereafter called test agents).1 However, complete instruments or assemblies are only tested as specified in this part of ISO 9022 in exceptional cases (see 5.3). Normally, representative samples such as material items or surface coatings on representative substrates are used for testing. The tests described in this part of ISO 9022 are designed for the selection of materials and components for instruments likely to suffer contamination during service life, rather than for regular production control. The purpose of testing is to investigate the resistance of an instrument and, in particular, of instrument surfaces, coatings, or synthetic materials, to a short exposure to the test agents.