Molds are various types of fungi (singular = fungus) that grow in filaments and reproduce by forming spores that can travel through the air. The term mildew is sometimes used to refer to some kinds of mold, particularly mold in the home with white or grayish color or mold growing in shower stalls and bathrooms. Mold may grow indoors or outdoors and thrives in damp, warm, and humid environments. Mold can be found in essentially any environment or season.
The most common types of household mold that are found indoors include Cladosporium, Penicillium, Alternaria, and Aspergillus. Stachybotrys chartarum (also known as Stachybotrys atra and sometimes referred to as “black mold”) is a greenish-black mold that can also be found indoors, although it is less common than the other types of mold found in homes. Stachybotrys grows on household surfaces that have high cellulose content, such as wood, fiberboard, gypsum board, paper, dust, and lint. There are types of mold that can grow on substances as different as foods and carpet.
Molds reproduce by forming tiny spores that are not visible to the naked eye. Mold spores are very hardy and can survive under conditions in which mold cannot grow, such as in dry and harsh environments. These spores travel through outdoor and indoor air. When the mold spores in the air land on a surface where moisture is present, mold can then start to grow.
Outdoors, molds play a role in the decomposition of organic material such as dead trees, compost, and leaves. They are most common in damp, dark areas or areas of decomposing plant life. Indoors, mold is often found in basements or shower stalls. Indoor mold in residential areas has the potential to cause health problems and can destroy surfaces and objects where it grows.