A system for ventilating and venting containers containing a fluid volume, such as gearboxes containing an oil filling, has a line system connecting the container to the atmosphere. Upon changes in the volumes in the container due to temperature changes, pressure is equalized. The line system contains a separating housing (12) in which a separating medium (46) having oleophobic and hydrophobic properties separates a first space (42) connected to the container from a second space (44) connected to the atmosphere. Line connections (10, 14) on the separating housing (12) are provided such that liquid-phase substances on opposite sides of the separating medium (46) can flow out of the first space (42) to the container and can drain out of the second space (44) to the atmosphere.