What a steam cleaner does, in essence, it is heated water to near boiling or even considerably above boiling, resulting in steam that is low in moisture and under slight pressure. The low moisture, slightly pressurized steam is delivered directed via nozzles or brushes to the area that needs cleaning. On hard surfaces the heat and slight pressure can loosen and remove dirt.
Because the steam is at a high temperature, near or above boiling, steam cleaning is effective for sanitizing surfaces without the need for disinfectants. When used to spot clean carpet or drapery stains, the steam penetrates the surface lifting dirt and other materials, sometimes without adding any chemical cleaning product.
After the item being cleaned is exposed to the steam under slight pressure, the water and any other material such as dirt or grease is suspended in the water and usually vacuumed up and held in a tank to be disposed of later.
The water in a steam cleaner is not reused so the unit must be periodically refilled. Some other common uses for steam cleaners are bed bug and dust mite control, and deodorizing.