Various systems generating nitric oxide are disclosed herein. According to one embodiment, the system includes a first gas source providing nitrogen dioxide mixed in air or oxygen, and a second gas source supplying compressed air and/or compressed oxygen. The system also includes a ventilator coupled to the first and second gas sources, wherein the ventilator is resistant to nitrogen dioxide. The ventilator regulates gas flow and allows for the adjustment of nitrogen dioxide concentration in the gas flow. The system further includes one or more conversion devices operably coupled to the ventilator where the conversion devices convert nitrogen dioxide into nitric oxide. A patient interface delivers nitric oxide to the patient and is operably coupled to the conversion devices. The system allows oxygen and nitric oxide levels to be varied independently.