Fungi are everywhere.
They are a normal important part of our natural environment. They are nature's garbage collectors, albeit opportunistic ones. Many of the building materials we use in our homes are a perfect food source for fungi. Thus, to keep them from proliferating, moisture must be kept at low levels (35-45% relative humidity (RH)). Fungi can proliferate in all of the following areas if they become wet or damp:

 

Latex paint	Office dividers	Drywall
Wood molding	Furnace filters	Carpet/Pad
Ceiling tiles	Material furnishings	Clothing/Shoes
Paper products	Resilient flooring backing	Insulation