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Mold Types and Causes

Toxic mold is an increasingly common problem in homes and commercial buildings. While many people have heard of toxic "black mold," in fact harmful molds exist in a wide variety of forms. Depending on the individual who has been exposed, mold exposure may cause ill effects that range from very serious health problems to minor annoyances. This article provides an overview of the main types of mold, and common factors that cause mold in homes and commercial buildings.

Types of Mold

Mold performs the natural function of breaking down biological materials. Found almost everywhere in our environment, mold travels as tiny spores that are often light enough to float through the air. Mold spores may also stick to pets and humans. When mold spores come to rest on a damp area, they begin to grow and digest the material on which they have landed.

There are many types of mold -- some sources say that there are over 100,000 different species. Some mold species are considered harmless, while others can cause potentially serious health effects.

The most common mold types found in homes and commercial buildings are:

  • Cladosporium
  • Penicillium
  • Aspergillus
  • Alternaria, and
  • Stachybotrys atra

Molds may produce volatile organic compounds ("VOCs") or toxins as byproducts of their metabolism. VOCs generally evaporate at room temperature. In fact, when a person smells a "musty" odor, he or she is actually smelling the volatile organic compounds. Some VOCs produce adverse health effects, but generally they are not extremely dangerous. In contrast to VOCs, toxins do not evaporate easily, and some are considered very dangerous to humans. In the end, regardless of whether a particular type of mold produces VOCs or toxins, all molds should be considered potential health risks, and the presence of mold should lead to investigation, cleaning, and/or removal.

What Causes Mold in Homes?

Mold spores may enter a home through windows or open doors, and can be brought into the home after attaching to people and pets. In order for a mold spore to grow there must be (1) abundant moisture, (2) the correct temperature range, and (3) a food source.

Sources of Moisture. Moisture can come from a variety of sources. Many modern homes and buildings are constructed in a very air-tight manner. While this is great for insulation purposes, it reduces the building's ability to "breathe" -- lessening the potential drying effects of natural air circulation.

Moisture may enter a building as a result of flooding, through broken pipes, or as a result of excessive rain. Moisture in a home or building may soak carpeting and other materials, creating a moist food source on which mold may attach and grow.

Moisture may also enter a building through walls and living spaces by way of leaks in the roof, walls, or windows. Such leaks may be a result of poor construction, faulty design, or faulty building materials.

Regardless of the source of moisture, once water enters the a building, mold will be drawn to it -- feeding on ceiling tiles, carpet, insulation, paper backing materials, and drywall.

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