A safety and automatic stop device for interrupting the flow of gaseous fluid along a main duct by tripping a safety valve member including a closing actuator for closing the safety valve member and an opening actuator for opening the safety valve member. A closing control module cooperates with a pressure-measuring housing to deliver an on/off pneumatic signal to the closing actuator as a function of the value of the pressure of a gaseous fluid to be controlled relative to at least one reference pressure determined by the pressure-measuring housing. A manual control element is used to apply an on/off pneumatic signal of predetermined value to the opening actuator and for selectively resetting the safety valve member. The safety and automatic stop device of the present invention is particularly adapted for application to a buried gas expansion station.