Oxygen concentrators are medical devices that are used to deliver oxygen to people who have trouble breathing. They work by removing nitrogen from the air and increasing the concentration of oxygen, which can be breathed in by the patient through a nasal cannula or mask. They are commonly used by people with chronic obstructive pulmonary disease (COPD), emphysema, and other lung conditions that make it difficult for them to get enough oxygen from the air around them. Oxygen concentrators are also used in hospitals, clinics, other medical settings and home for patients who need oxygen therapy.