The first sign that you may have mold in a basement is usually a musty odor.
Mold in a basement is a result of the excess moisture inside your basement. Mold spores are always in the air but will only grow on surfaces with a lot of moisture and a basement is a great environment for mold growth.
Water seepage from the groundwater, moisture from your washer, and leaky pipes can all contribute to humidity problems and subsequent mold growth inside your basement. Wood, cardboard, and clothes, which are prone to dampness, are also great growing environments for mold since they provide a constant source of moisture.
Get Rid of Mold in a Basement With a Whole-House Dehumidifier
Your nose knows if there's a mold problem.