Oxygen concentrators and oxygen cylinders are designed to deliver oxygen  therapy to patients who aren’t able to get the desired amount of oxygen on their own. Oxygen concentrators dispense oxygen in almost the same way that oxygen tanks do, delivering oxygen directly to the patient via a nasal cannula or an oxygen mask. The difference is that oxygen tanks contain a fixed amount of pressurized oxygen while concentrators collect oxygen from surrounding air, concentrate it, and then deliver it to the patient, removing the need for replacement or refilling.