This part of ISO 9022 specifies methods for the testing of optical instruments and instruments containing optical components, under equivalent conditions, for their ability to resist sulfur dioxide (SO2) or hydrogen sulfide (H2S) in a humid atmosphere. The purpose of the test is to investigate to what extent optical, mechanical, chemical and electrical performance characteristics of the specimen are affected by sulfur dioxide or hydrogen sulfide. This part of ISO 9022 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.