Controlling Indoor Mold

The key to mold control is moisture control

A blue home flying the American flag in the front porch with wooden fence
Controlling moisture is key! Find the moisture source, repair it, and clean what you can.

Tiny mold spores are all around us, both indoors and outdoors. Mold spores travel easily through the air and begin to grow indoors when moisture is present. There is no practical way to eliminate all mold and mold spores from the indoors, so the best way to control mold growth is to control indoor moisture. When indoor conditions are just right, mold spores can grow and become a problem. By taking important steps, you can prevent and control mold growth inside your home.

Mold spores need three things to grow:

  • Moisture
  • A nutrient source (i.e., wood, paper, or other materials)
  • The right temperature

Of these three conditions, the most important to control is moisture. Indoor mold growth is really a sign that moisture is present. If indoor moisture is controlled, mold will not grow.

Fixing the moisture source

Since moisture is essential for mold growth, do all you can to quickly identify and fix any source causing too much indoor moisture. Common household problems that lead to indoor moisture issues include:

  • Roof leaks.
  • Leaking pipes or plumbing fixtures.
  • Condensation due to high indoor humidity.
  • Indoor flooding.

After all moisture and water problems have been fixed, clean the moldy area and keep the area dry.

If you cannot identify the moisture source, or if you are dealing with a large mold and water problem, consider a professional home inspection. Visit "Hiring a contractor", for tips on hiring a Mold Remediation Contractor. 

Testing for mold

The Wisconsin Department of Health Services does not recommend testing for mold because:

  • Federal standards or limits for airborne mold concentrations or mold spores do not exist.
  • Mold spores are everywhere around us, indoors and outdoors.
  • Mold testing can be expensive.

If you see or smell mold, it is present. In any situation, your approach should be to find the moisture source, fix it, and clean what you can.

Preventing mold growth

Important actions can be taken to prevent indoor mold from becoming a problem:

  • Keep indoor spaces well ventilated and dry. Air conditioners and dehumidifiers can help.
  • Keep indoor humidity levels below 50%.
  • Clean bathrooms often and keep surfaces dry. Run the bathroom ventilation fan during and after showers.
  • Promptly fix water leaks.
  • Clean up and dry your home fully and quickly (within 24-48 hours) after any flooding event.

Frequently asked questions

For more information, contact your local health department, or call the Wisconsin Department of Health Services at 608-266-1120.

Last revised January 14, 2025