A whole-house humidifier, or a central humidifier, is connected to the home’s hot air ducts and cold air return. It can either work with or independent from the heating/cooling system. When the humidifier is switched on, water accumulates inside of a collection tray. The air passing through the heating/cooling ducts will then travel through the collection tray, pick up moisture, cycle through the furnace, and then finally returns to the duct system where the moisture-laden air is distributed into your home.