A dual air flow exchanger, allowing a heat transfer and humidity transfer between two air flows, and including a plurality of first and second air circulation networks separated by membranes permeable to water vapor and impermeable to air and to liquid water, each of the first and second networks including cells each defined by a wall including openings for passage of air, the cell wall including two opposing edges at which same is open in a direction of stacking. For at least one of the first networks, at least one of the two opposing edges of each cell wall defines a hollow open in a direction of the second directly consecutive air circulation network, the hollows receiving a part of the second network.