Oxygen supplies are accessories used along with an oxygen concentrator, oxygen regulators, tubing, and more. An oxygen concentrator, also called an O2 concentrator, is a machine that purifies the surrounding air. It removes nitrogen and produces a filtered stream of oxygen for the user to inhale. Unlike oxygen cylinders, oxygen concentrators provide an unlimited amount of oxygen because they are utilizing the air around you rather than the air contained in a tank. An oxygen regulator is used with an oxygen cylinder to control the flow of oxygen that the user receives. This product is sometimes referred to as an oxygen conserving device, or OCD.