Molds alter, and essentially breakdown the organic structure of the substrate that supports its growth. This process is commonly referred to as rot. Wood rot is a well known condition resulting from fungal colonization. Molds also release dyes as metabolic byproducts that can stain some building materials (the non-scientific term “mildew” refers to the staining by molds on fabrics). Molds may also excrete hydroscopic products that alter the condition of a building material surface to facilitate the capture of water from the air. In this way, molds can actually alter their environment to expand the range of environmental conditions that will support their growth. Molds may also release toxins on the surface of building materials to gain a competitive edge over other microorganisms thus allowing greater exploitation of a favorable environmental niche. When environmental conditions become less favorable (e.g. dryer), mold colonies produce and release millions of spores that are resilient to harsh environmental; conditions and remain viable for long periods (years) until environmental conditions again become favorable. Thus, mold growth can alter a construction product by either, (1) changing the materials structural integrity or finish, (2) increasing the likelihood that mold will colonize the material in the future, or (3) creating a real or perceived health risk related to the material.