Mold: Mold Growth in Homes

Molds are part of the natural environment. Outdoors, molds play a part in nature by breaking down dead organic matter such as fallen leaves and dead trees, but indoors, mold growth should be avoided. Molds reproduce by means of tiny spores; the spores are invisible to the naked eye and float through outdoor and indoor air. Mold may begin growing indoors when mold spores land on surfaces that are wet. There are many types of mold, and none of them will grow without water or moisture.

Molds are organisms that may be found indoors and outdoors. They are part of the natural environment and play an important role in the environment by breaking down and digesting organic material, such as dead leaves. Also called fungi or mildew, molds are neither plants nor animals; they are part of the kingdom Fungi.

Molds can multiply by producing microscopic spores (2 - 100 microns [µm] in diameter), similar to the seeds produced by plants. Many spores are so small they easily float through the air and can be carried for great distances by even the gentlest breezes. The number of mold spores suspended in indoor and outdoor air fluctuates from season to season, day to day, and even hour to hour.

Mold spores are ubiquitous; they are found both indoors and outdoors. Mold spores cannot be eliminated from indoor environments. Some mold spores will be found floating through the air and in settled dust; however, they will not grow if moisture is not present.

Mold is not usually a problem indoors -- unless mold spores land on a wet or damp spot and begin growing. As molds grow they digest whatever they are growing on. Unchecked mold growth can damage buildings and furnishings; molds can rot wood, damage drywall, and eventually cause structural damage to buildings. Mold can cause cosmetic damage, such as stains, to furnishings. The potential human health effects of mold are also a concern. It is important, therefore, to prevent mold from growing indoors.

Mold needs moisture and food. Moisture is the most important factor influencing mold growth indoors. Controlling indoor moisture helps limit mold growth.