A separator is a machine or device that separates something into its constituent or distinct elements. A simple separator may be a mechanical device that collects items and sorts them by characteristics such as size or shape. A vapor–liquid separator is a device used in several industrial applications to separate a vapor–liquid mixture. They are commonly used in refrigeration to separate moisture and oil vapor from coolants. A particulate separator collects small contaminants or byproducts where particles are suspended in some medium.