A safety device for a gas distribution system includes a valve body, an upper casing attached to the valve body, the upper casing housing at least one spring. Further, the at least one spring is attached to a movable diaphragm that is exposed to gas system pressure. The valve body also includes a release element mounted within the valve body. The release element releasing a relatch plug when the device is activated to move a safety disc into contact with a valve seat to stop fluid from flowing when an overpressure or an underpressure condition is sensed.