We have been using this cleaner for over 10 years. It is also called an air washer. It is certainly expensive, but health is more expensive. Dry air is not very good for the body. The principle of operation is simple: a fan blows air onto a set of disks, which rotate through a flexible drive in a container of water, in this way dust particles settle on wet disks and are then washed off with water. As with any device, care is needed: adding water to the tank and periodically cleaning the disks and the tank. You'd be surprised how quickly water gets dirty. The rate of evaporation of water depends on the humidity of the room. The eldest son bought a model with a large tank capacity for his family. I am glad that he also takes care of his children.