Abstract: Device and method for diffusing a protective flux. In order to protect one area of a service station, a more or less parallel air flow is created in the direction of the area. Above a threshold F, the air flow has a gradually increasing speed V22 and, below the threshold, the air flow speed V21 is more or less uniform along the length of a flow section in a plane P which is transverse to the direction of flow D. One possible configuration for an air flow diffusion device, which allows a confinement barrier to be created, consists of a diffusing wall comprising a main wall and a lateral wall. The main planar wall is adapted to diffuse a main laminar flow in the sterile area to be protected. The lateral wall is adapted to diffuse a lateral flow divergent from the main flow. A skirt is disposed to create an obstacle to the lateral flow and to accelerate the flow by of deflection.