There is always a food source available in an indoor environment. Mold can feed on many building materials such as wallpaper, drywall, paint, carpet, adhesives, wood, fabrics, paper products and other organic materials. As mold feeds on their food source, they produce a byproduct of digestion that results in a moldy, musty smell. When you smell that odor, you know that there is (or recently has been) a wet-damp environment that has allowed mold to start growing. As a general rule, when someone tells you that they see mold in their home or office, the moisture problem needs to be resolved and the mold needs to be removed as soon as possible.