The following paper will concentrate on the fundamentals and principles of natural gas pressure regulators. In the gas regulator’s conception it was mainly a device used to reduce high pressure to a more usable lower pressure. Today, more is expected from the performance of the pressure regulator. Pressure reduction is no longer the only function needed. The regulator is considered an integral measurement instrument that must adhere to the stringent codes put forth by the U.S. Federal Department of Transportation and many state Public Utility Commissions