Lab filters are used in a wide array of chemical, biological, and medical applications to separate solid particles from fluids or gases. The filter is porous, allowing fluid or gas to flow through it while trapping particles in the membrane. Different types of fibrous media or membrane material are used for making filters that are suited to particular filtration applications. Some filters are made of borosilicate glass for resistance to temperature changes. Others are made of materials such as PES (polyethersulfone), MCE (mixed cellulose esters), nylon, polypropylene, PVC (polyvinyl chloride), or PTFE (polytetrafluoroethylene). Air sampling filters are used to trap atmospheric particles, aerosols, and pollutants for analysis. Inline filters are commonly used with medical devices or vacuum systems. Other filters include syringe filters, centrifugal filters, and bottle top filters. Manufacturers include Millipore and Whatman.