Laboratory filters are used to remove particulates from samples in laboratory-scale applications. They consist of a filter medium and housing or holder that constrains and supports the filter media in the sample’s path. There are several basic types of laboratory filters. Membrane filters are thin, polymeric films that contain thousands of microscopic pores. The size of the pores determines the size rating of the membrane. Typically, membrane filters are used in the quantitative separation or filtration of suspended matter from liquids and gases. Pre-filters are often placed upstream from membrane filters to reduce particulate loading and allow the membrane to operate more efficiently. Centrifugal filters are suitable for small-scale laboratory separations such as protein or nucleic acid desalting and concentration. These devices use centrifugal force to drive liquid through the filter. Increasing the centrifuge speed (G force) increases the pressure across the filter. Fouling is minimized by design features that cause the G force to reach the filter at an angle, sweeping accumulated molecules from the surface. Syringe filters consist of a filter element and housing assembly and are used in applications where a sample must be filtered before entering a syringe. Specialized and proprietary filters that are made from a variety of porous papers are also available.