Humidifier filters are also known as water panels, evaporators or water pads. Humidifier filters are used in a humidifier to help alleviate dry air mostly in the winter time. A humidifier works when warm, unfiltered air is blown across a humidifier filter, which is saturated with water. As the air passes over the filter, it picks up moisture and distributes the humid air into the room or through the HVAC system. Find out more about humidifier filters.