Indirect attack on materials. Damage to fungus-resistant materials results from indirect attack when:(1)Fungal growth on surface deposits of dust, grease, perspiration, and other contaminants (that find their way onto materiel during manufacture or accumulate during service) causes damage to the underlying material, even though that material may be resistant to direct attack.(2)Metabolic waste products (i.e., organic acids) excreted by fungus cause corrosion of metals, etching of glass, or staining or degrading of plastics and other materials.(3)The products of fungus on adjacent materials that are susceptible to direct attack come in contact with the resistant materials.