Oxygen Concentrators are medical devices that deliver almost pure oxygen through the nose via tubes. Air generally contains 21% oxygen; the rest is mostly nitrogen. Concentrators remove the nitrogen, leaving the remaining air 87-95% oxygen. Then the oxygen concentrators deliver the oxygen to the patient by means or tubes or masks. Oxygen concentrator output is generally measured in LPM (liters per minute). Oxygen therapy is typically recommended for people who have ailments, such as lung disease, cancer, or heart problems, which prevent the proper amount of oxygen from circulating in the blood. It must be prescribed by a physician. The amount of time spent doing oxygen therapy may vary; some will require it for a few hours, while some will require a constant therapy. The oxygen concentrator & therapy section has different types of oxygen therapy products.