Excess moisture in a building leads to the development of mold in air duct systems. Offices, warehouses and homes are all susceptible to the levels of humidity that lead to mold, whether from steam emanating from sinks or showers or through leaks in roofs or seepage in floors.
Controlling mold in one's air ducts begins with controlling the access that moisture has to one's home. Keeping dirt in crawlspaces covered with plastic keeps moisture from entering a building from the ground. Well-ventilated crawlspaces gather less moisture from the ground beneath, as the air scatters it. If water is seeping into a basement, the cause can range from a lack of gutters on the house to a ground level that sends water toward the house, rather than away from it.
In climates that are humid and hot, air conditioners can provide a drying influence. However, it is important to keep an eye on condensing units to make sure that mold does not begin to grow. Installing storm windows and insulation can regulate temperature swings inside a building. This keeps moisture from condensing on glass, which contributes to overall humidity. Keeping doors open between rooms evens the temperature throughout the entire space so that moisture does not condense, leading to the possible development of mold along windows as well as in air ducts.