A ventilation device for fluid-storing reservoirs includes a connecting part (1) attachable to the opening of the reservoir to form an air- and/or fluid-conducting connection between the inside of the reservoir and the surroundings. This connection is effectively sealed by a labyrinth-like seal of a system of seal passages (53, 59, 69, 73) from the penetration of media such as water and/or cleaning chemicals but is not sealed off from an exchange of air for ventilation. A filter element (61) is placed inside the connection. A portion of the seal passages (59, 69, 73) is formed on a ventilation chamber (41) releasably attachable to the connecting part (1) and having a seat (79) for the filter element provided as a filter leaf (61). The filter leaf (61) forms a partition between two successive seal passages (59 and 69) adjacently extending approximately parallel to one another.