This method is based on the natural principle of water evaporation in nature. Water adheres to the surface of the rotating discs or soaks into the filter paper and rises upwards. The fan is used to direct the flow of dry air through these filters. This makes the water evaporate into the air faster and easier. It is not possible to supersaturate the air with water vapor by cold evaporation. Unlike other principles (ultrasound, thermal evaporation), no escaping steam is visible in this method of humidifying the air.
Air washers are a special category for natural evaporation. These are a combination between a purifier and a humidifier operating on a similar principle as cold evaporation. Special evaporator disks adsorb (bind) water and the fan blows dry air through these humidified rotating disks. The humidified air is then dispersed into the surroundings. Humidifiers working on this principle are high-performance devices that have low operating costs and are almost noiseless. A significant advantage of these devices is the fact that they clean the air from dangerous particles in the air and if they are equipped with other technologies for air purification (eg PLASMA system or HEPA filter), they can be a full-fledged replacement for air purifiers.