There are many different filtration system varieties. Vacuum and pressure filters are popular types of filter media that may use filtering screens in addition to various other processing techniques. Membrane filtration is one of the most common types as it involves the use of a porous film or thin sheet. Depending upon the filtration product, pore sizes can vary to capture only large particles as in waste water treatment or everything down to microscopic bacteria in potable water treatment. In addition to fluid or water filtering systems, air filtration systems are used in a wide variety of industries, including food and beverage processing, chemical, pharmaceutical, mining, pulp and paper, automotive and agriculture.