High pressure media enters to regulator through the inlet into the high pressure chamber. When the control knob is turn clockwise, it compress the range spring and exerts a force on the diaphragm which pushes the value stem open. This release gas into the low-pressure chamber, exerting on opposing force on the diaphragm. An equilibrium is reached when the spring force on the diaphragm is equal to the opposing force at the gas in the low-pressure chamber.

In a single – stage regulator, delivery pressure increases as cylinder pressure decays, because, there is less gas pressure exerted on the value stem. Thus, frequent adjustment of the control knob is required to maintain constant delivery pressure. This does not pose a problem, however, with pipelines and liquefied gas products where inlet pressure is maintained relatively constant.