Specifies methods for the testing of optical instruments and instruments containing optical components, under equivalent conditions, for their ability to resist contamination, i.e. contact with corrosive chemical substances. 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 contamination. The tests described are designed for the selection of materials and components for the instruments. Complete instruments or assemblies are only tested in exceptional cases.