Some assessors talk of mold growth as that which can be seen. In their reports they state that no mold growth is present because they couldn’t see any. The problem with that is mold growth isn’t restricted to what we can see. Mold growth begins with what we cannot see: the germination of the spore and the early vegetative growth from that germination. What we can see is colonization. Think of it like this:  You’re in an airplane, flying at 36,000 feet. You pass over a small, forested town of 1,000 people. Because of the small community, the lack of large buildings, and the vegetative growth around the occupants, you may not know they’re there. But, if you pass over Chicago or Miami, you’ll know they’re there, because you’ll see the large development (which has taken up enough real estate to make itself visible). Those microscopic spores that are germinating and forming vegetative structures cannot be seen. It’s only when the growth colonizes (i.e., takes up enough real estate) that we can see that growth has taken place.

“Fungi respond to their environment in both absolute and relative ways. For example, for every fungus, there are absolute minimum and maximum temperatures below and above which growth will not occur. Near these temperature extremes, growth rate is very slow, increasing gradually as conditions approach the optimum, that is, the temperature at which the growth rate is maximal. The same pattern holds for water availability, nutrient levels and types, light, and atmosphere. 

“Complicating this pattern is the fact that environmental factors affect fungi interactively. Thus, the effect of water availability on fungal growth must be considered relative to the influences of temperature, nutrient availability, lighting conditions, and so forth. . . Both the biological and physical interactions between water availability and temperature must be considered when discussing the effects of either of these parameters on fungal growth. This essentially means that for any fungus there is no single optimal set of environmental conditions.”