HUMIDIFIER

A humidifier for humidifying a dry cathode supply air via a humid cathode exhaust air in a fuel cell system, may include a housing, a membrane stack, and/or a sealing arrangement. The membrane stack may include a plurality of membranes, two first side surfaces, two second side surfaces, and/or two third side surfaces. The plurality of membranes may be stacked on one another transversely to a longitudinal direction of the membrane stack. The first side surfaces may be arranged opposite one another. The second side surfaces may be arranged opposite one another. The third side surfaces may be arranged opposite one another. The sealing arrangement may include two sealing frames, each of the sealing frames is assigned to one of the respective first side surfaces. Each of the sealing frames may have a frame-shaped contact area and a retaining edge protruding from the contact area.