How do you know if mold is behind drywall?

Most mold is unmistakable, but sometimes small or largely hidden growths just make a surface look dirty. A quick test for mold can be done when you dip a swab in diluted bleach (1 part bleach, 16 parts water) and dab it on the wall. If the spot quickly lightens (or keeps coming back after cleaning), assume it’s mold. 4014 Fox Valley Dr, Rockville, MD 20853 (301) 717-1454 http://www.mdmoldtesting.com https://www.facebook.com/MDMoldTesting/