on the upstream part of the valve hold the diaphragm/poppet assembly in the closed position against the force of the diaphragm loading spring. If the supply pressure falls, the closing force due to supply pressure is reduced, and downstream pressure will rise slightly to compensate. Thus, if the supply pressure falls, the outlet pressure will increase, provided the outlet pressure remains below the falling supply pressure. This is the cause of end-of-tank dump where the supply is provided by a pressurized gas tank. The operator can compensate for this effect by adjusting the spring load by turning the knob to restore outlet pressure to the desired level. With a single stage regulator, when the supply pressure gets low, the lower inlet pressure causes the outlet pressure to climb. If the diaphragm loading spring compression is not adjusted to compensate, the poppet can remain open and allow the tank to rapidly dump its remaining contents. Double stage regulator Two stage regulators are two regulators in series in the same housing that operate to reduce the pressure progressively in two steps instead of one. The first stage, which is preset, reduces the pressure of the supply gas to an intermediate stage; gas at that pressure passes into the second stage. The gas emerges from the second stage at a pressure (working pressure) set by user by adjusting the pressure control knob at the diaphragm loading spring. Two stage regulators may have two safety valves, so that if there is any excess pressure between stages due to a leak at the first stage valve seat the rising pressure will not overload the structure and cause an explosion. An unbalanced single stage regulator may need frequent adjustment. As the supply pressure falls, the outlet pressure may change, necessitating adjustment. In the two stage regulator, there is improved compensation for any drop in the supply pressure. Applications Pressure reducing regulators Air compressors Air compressors are used in industrial, commercial, and home workshop environments to perform an assortment of jobs including blowing things clean; running air powered tools; and inflating things like tires, balls, etc. Regulators are often used to adjust the pressure coming out of an air receiver (tank) to match what is needed for the task. Often, when one large compressor is used to supply compressed air for multiple uses (often referred to as "shop air" if built as a permanent installation of pipes