A method for generating a pneumatic barrier with a device that operates in a stratified atmosphere associated with the occurrence of radiation frost. This device takes cold and dense air found close to the ground by means of an axial fan with a vertical axle that propels the air upward to an elbow that forces the airflow to make a 90° turn. The airflow discharged from the device through the outlet section forms a jet with a horizontal axis. The jet's vertical cross-section, perpendicular to its axis, has a rectangular shape and sides that grow with the distance to the outlet. The momentum transported by the jet is able to create at a certain distance from the outlet a pneumatic barrier that fits the jet's section. This pneumatic barrier faces an air mass that is colder and denser than the air transported by the jet and prevents such colder and denser air from advancing toward the device.