Think about it: The water that makes your humidifier run smoothly is also a breeding ground for mold and microbes. To clean a humidifier, pour two cups of undiluted white vinegar into the water tank and swish it around until wet. Place the vinegar-filled tank on the base and allow it to drain into the reservoir for 15 to 20 minutes. Empty it and use a small brush to scrub crevices, removing remaining buildup. Keep in mind, however, that it’s always best to follow the manufacturer’s cleaning directions, as humidifiers can differ.