More than 60% air provides the perfect environment for mold and dust mites to thrive, which can cause nasal congestion, sneezing, coughing, and even wheezing. Too much moisture can also cause problems in your house, including cracked wood furniture and floors, promoting mold growth on carpets, and rusting your toilet tank and plumbing. A dehumidifier can help you reduce moisture in the air, but it's only effective when used correctly. Here are 5 mistakes not to make when using a dehumidifier.