If you were to use two or more units connected together, you would increase the volume of air (Flow per Minute). You would not increase the pressure, the pressure is limited by the unit you select. Connecting two similar units together would not quite double the volume. Connect the units with a brass Y connector. Only connect similar units together, 8 PSI Machine with 8 PSI Machine's or 10 PSI Machine with 10 PSI Machine's. Do not connect say an 8 PSI Machine with and 10 PSI Machine. We carry all of the hose and fittings you would need. Remember you do not need an Oxygen Regulator when using these concentrators.