Abstract: First reducing stage for a two-stage regulator, including a nozzle connected by a yoke and a clamping screw to an inlet, a pressure chamber, and a shutoff member that slides, guided by a piston or by a diaphragm, inside the pressure chamber. The adjacent compensating chamber contains a helical spring coaxial with the shutoff member and the end of the shutoff member is provided with a thermally insulating component. In the compensating chamber there is interposed, between the helical spring and the tubular part of the shutoff member, for the entire length of the spring, a thermally insulating component. That side of the diaphragm which communicates with said pressure chamber also has a covering of thermally insulating material. The helical spring is completely covered in thermally insulating material.