Abstract: An installation includes a worktop, a first wall and a device for the close protection of products arranged on the worktop, whereby the products are sensitive to contamination from the ambient environment. The products are protected by diffusion of a sterile air stream in a direction substantially perpendicular or parallel to the worktop. The device extends along the worktop and has a least one end adjoining the first wall so that there is an air gap between the end and the first wall. The end is formed by a porous second wall made of perforated material, extending substantially perpendicular to a longitudinal axis of the device, in such a way as to create in the gap a sterile air leakage directed outward away from the worktop, whereby the sterile air leakage counters any ambient air induction into the gap toward the worktop.