Fibrous glass duct insulation will not support the growth of mold when tested in accordance with applicable ASTM and UL specifications. Furthermore, fibrous glass duct insulation products designed for installation inside air ducts are tested for mold and bacteria resistance in accordance with ASTM test procedures. Fibrous glass insulation installed in clean, dry, well-maintained air duct systems will not contribute to mold, fungal, or bacterial amplification and consequent contamination of the indoor environment.