Compressed air regulator
A compressed air regulator is made for regulating air from compressors or similiar sources. The input pressure can range from anywhere from 0 to several thousand psi, and output pressure can be either predefined or adjusted within a certain range.
Air regulators commonly found at hardware stores are relatively cheap, but have a somewhat limited use because of the low input pressure. Compressed air regulators have been used successfully to regulate propane, though they are not made for this and could potentially be damaged. An air regulator may vent to the atmosphere when the pressure dial is being turned down, and vented propane may pose a fire hazard. Liquid propane entering the regulator may damage it as well. Nevertheless spudgun enthusiasts commonly use such regulators on propane fuel meters.