Crawlspaces can be a breeding ground for mold, mildew and even pests, and it's important to keep these areas as dry as possible. If using a dehumidifier to reduce moisture levels in your crawlspace, give the device regular inspections. If your dehumidifier is malfunctioning, the crawlspace will become damp. This can cause a strong, musty odor to develop (YUCK!) and can lead to a number of more serious problems. If you find foundation problems while you're under your house, you'll need to find a pro to help.