Oxygen concentrators using pressure swing adsorption (PSA) technology are used widely for oxygen provision in healthcare applications, especially where liquid or pressurized oxygen is too dangerous or inconvenient, such as in homes or in portable clinics. For other purposes there are also concentrators based on nitrogen separation membrane technology. An oxygen concentrator takes in air and removes nitrogen from it, leaving an oxygen enriched gas for use by people requiring medical oxygen due to low oxygen levels in their blood. Oxygen concentrators provide an economical source of oxygen in industrial processes where they are also known as oxygen gas generators or oxygen generation plants.