Abstract: An apparatus for airing grains stored in bulk on a floor of a depot, including a tunnel comprising a duct made of half cylindrical shaped corrugated sheets. The corrugations are approximately sine-wave shaped and provide adequate reinforcement for supporting the weight of grain stored on top. Aprons anchor the duct to the floor, and the duct is connected to a blower which supplies air to the duct. The duct has an inner surface, an outer surface, and two longitudinal edges, with each of the longitudinal edges extending substantially parallel to one another and bear on the respective aprons anchored to the floor. The duct is provided with air outlet openings for injecting air into the grain, wherein the openings are located adjacent or near the longitudinal edges of the duct. Each apron comprises a substantially horizontal wing for anchoring the apron to the floor, thereby forming an air channel between the floor and the inner surface of the duct.