This document specifies methods for determining the deterioration of plastics due to the action of fungi and bacteria and soil microorganisms. The aim is not to determine the biodegradability of plastics or the deterioration of natural fibre composites. The type and extent of deterioration can be determined by a) visual examination and/or b) changes in mass and/or c) changes in other physical properties. The tests are applicable to all plastics that have an even surface and that can thus be easily cleaned. The exceptions are porous materials, such as plastic foams. This document uses the same test fungi as IEC 60068-2-10. The IEC method, which uses so-called "assembled specimens", calls for inoculation of the specimens with a spore suspension, incubation of the inoculated specimens and assessment of the fungal growth as well as any physical attack on the specimens. The volume of testing and the test strains used depend on the application envisaged for the plastic.