Evaporative humidifiers are devices that add moisture to the air by using a fan to blow air through a wet wick or filter. As the air passes over the damp surface, water evaporates, increasing humidity levels in the room. This type of humidifier is self-regulating, meaning it can adjust its output based on the humidity level in the environment. These humidifiers are popular for their energy efficiency and low maintenance needs. They do not require frequent refills like some other types, such as steam vaporizers or ultrasonic humidifiers. Regular cleaning is essential to prevent mold and bacteria growth in the water reservoir.