An electrochemical device comprising one or multiple self-humidifying electrochemical fuel cells, wherein each electrochemical fuel cell comprises a main surface (9) which can be used for an electrochemical reaction and can consume the oxygen contained in the air. A single air flow enters into the fuel cell and is divided into at least two parts of air flow inside the fuel cell. At least one of these parts of air flow has mass transfer contact with the main surface (9). Otherwise, at least another part of air flow has no mass transfer contact with the main surface (9). The air flow is divided by a separation sheet (5).