Mold (and mildew) are common terms for fungi that can grow in damp locations in buildings, although molds are present everywhere, indoors and outdoors. Molds are important microorganisms because they help break down dead plant and animal material and recycle nutrients in the environment. There are many kinds of molds, and mold growth can have many forms and colors. To grow and reproduce, mold only needs food — any organic matter, such as leaves, wood, paper, or even dust — and moisture. Organic matter is almost always available, so whether mold grows depends mostly on whether there is moisture. By fixing moisture problems, you can keep mold from growing in your home.

The presence of visible mold, visible moisture, water-damaged materials, or mold odor in a building is clearly linked to increased risk of various respiratory health effects. These health effects include asthma development, asthma exacerbation, allergies, respiratory infections, and a variety of upper and lower respiratory symptoms. The more extensive or severe the dampness and mold, the greater the risk of health effects. The health effects also depend on the susceptibility of the occupants. Speak to your doctor if you have concerns about the health effects of mold.