ISO 9022-20:2014 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 sulfur dioxide (SO2) or hydrogen sulfide (H2S) in a humid atmosphere.The purpose of the testing is to investigate to what extent optical, climatic, mechanical, chemical, and electrical performance characteristics of the specimen are affected by sulfur dioxide or hydrogen sulfide.ISO 9022-20:2014 is not applicable to the testing of material and surface coatings for their corrosion resistance using high concentrations of sulfur dioxide, for which representative samples are generally used as specimens. The appropriate material standards apply to tests of this type.