What is mold?
Mold is part of the diverse group of organisms called fungi, which include a wide range of species from tiny molds to large mushrooms. Fungi are part of nature’s recycling system and play a key role in breaking down organic materials such as plants, leaves, wood fiber and other natural materials. Fungi extract food from organic material, and they grow and reproduce by way of spores.
Conservatively, more than 100,000 species of mold exist in the world and at least 1,000 species are common in the U.S. and Canada. They are estimated to comprise a quarter of the entire biomass on earth. Spores are everywhere. The air we breathe is a virtual jungle of fungal spores and we regularly encounter them as part of everyday life. Foods spoil because of mold. Leaves decay and pieces of wood lying on the ground rot because of it. That fuzzy black growth on wet window sills is mold. Paper or fabrics stored in a damp place get a musty smell that is due to the action of these fungi. See this abstract from the American Journal of Botony for more on fungi species.
Molds are part of the natural environment. Outdoors, they 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.
There are a host of materials in and around a house that, under proper conditions, can become a breeding ground for mold. Molds require four things for growth: food, suitable temperature, oxygen and moisture. High humidity, plumbing leaks, excessive condensation, flooding and dampness should alert home owners to the potential for infestations. Crawl spaces, basements and attics are prone to these problems.
What to do if you have mold in your home
The most important step is to identify and fix the moisture sources causing the growth. For small infestations, use detergent and water to wash off hard surfaces, and dry completely. Replace moldy porous or absorbent materials (such as ceiling tiles, wallboard, and carpeting). If you do not see mold growth but notice a musty odor, it may be growing behind water-damaged materials, such as walls, carpeting, or wallpaper. Persons cleaning mold should wear gloves, eye protection, and a dust mask or respirator to protect against breathing airborne spores (an N95 dust mask or respirator may be purchased in hardware stores). If you have health concerns, you should consult your doctor before doing any mold cleanup.