How to Locate Mildew in Walls

• 1). Call a mold remediation expert to do an inspection. According to MyHomeImprovement.com, a professional will take humidity readings to determine the amount of moisture present in a room. He could also use a thermal imaging camera to measure temperature differences to detect moisture levels behind walls without creating a hole in the wall.
  
  
• 2). Ask a local lab to do an inspection of air quality. They can look for areas of moisture, take wall samples, and then test them to see if mold or mildew is growing.
  
  
• 3). Pierce a hole in the wall using a drill to do your own inspection.
  
  
• 4). Cut a big enough section of the drywall using a saw to see if mildew is present. You'll need a flashlight to see the mildew when looking through the hole, as mildew is dark in color.