Spring loaded poppet valves are commonly used as a pressure reducing element. Poppet valves have elastomeric sealing in regular applications and a thermoplastic sealing in high pressure applications. This seals the valve seating against any gas or fluid leakage. The poppet valve is controlled by the spring force to open the valve and let the medium flow from inlet to outlet. As there is a rise in output pressure, the poppet valve closes due to the force generated by the sensing element, which overcomes the spring force. http://www.novors.com/gas-regulator/low-pressure-regulator/