Vacuum pumps remove gas molecules from a sealed volume and leave behind a partial vacuum. Laboratory vacuum pumps are usually of diaphragm pump or rotary vane pump type. Diaphragm pumps are capable of handling solvent and corrosive vapors but are limited to medium vacuum. On the other hand, rotary vane pumps are capable of producing high vacuums but have to be protected from contamination which requires the use of additional equipment. Vacuum pump may be coupled with a vacuum controller to make a source of steady vacuum that can be tuned to a particular set-point.