Oxygen concentrators: Oxygen concentrators filter the oxygen from the surrounding air. Patients may however use the device at home. It is therefore appropriate, in the first place, for the people that do not leave home regularly. For the people that can’t stay home, they can use small cylinders of medical oxygen, which are exchanged when empty.

For further clarification on Oxygen Concentrator, attached you can find downloadable datasheet. 

Medical Oxygen Cylinders: People who need oxygen only sporadically receive compressed oxygen bottles. This system is very simple to use; however, it is not suitable for long-term therapies.