ISO 9022-11:2015 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 mould growth. However, complete instruments or assemblies are only tested as specified in ISO 9022-11:2015 in exceptional cases. Normally, representative specimens such as mounted optics, material samples, or surface coatings on representative samples are used for testing.

The tests described in ISO 9022-11:2015 are designed for the selection of materials and components for instruments likely to be used in an environment that is conducive to mould growth, rather than for regular production control. The purpose of testing is to investigate to what extent the optical, climatic, mechanical, chemical and electrical (including electrostatic) performance characteristics of the specimen are affected by mould growth.

In addition, the tests in ISO 9022-11:2015 are designed to assess to what extent metabolic waste products (such as enzymes or acids) excreted by fungi, cause etching, corrosion, or short-circuits on, for instance, printed circuit boards.