Abstract: A housing, particularly of a vehicle headlamp, has aeration of its interior housing space via at least one hole for admission and/or exiting of air flows, wherein a switch apparatus, that changes a cross section of flow as a function of humidity of the air, is positioned in the at least one hole to move automatically from a closed position into an open position and vice versa. A method for aerating the interior space of the housing involves air entering the interior housing space via at least one air admission hole and exiting the interior housing space via at least one air exit hole, with aeration occurring only if condensation is present in the interior housing space and if a humidity of the entering air is lower than a humidity of the air in the interior housing space.

Abstract: A headlight for a motor vehicle in which an interior space is enclosed by a housing and a cover lens. The interior space communicates with the surrounding outside atmospheric air through a duct that has an inlet opening and an outlet opening. The duct contains reversably-acting hygroscopic desiccating substance which provides less resistance to flow of air into and out of the interior space, than any other leakage points in the headlight. The duct has a portion projecting into the interior space, and has a substantially high permeability for water molecules in a mixture of water-vapor and air. This portion of the duct resists air flow in establishing pressure equilibrium between the inlet opening and the outlet opening of the duct, so that at least a larger part of air in the duct passes through the inlet and outlet openings. One of these openings is in the interior space, whereas the other opening is located in the atmosphere.

Abstract: The present invention relates to a headlight for vehicles with an interior space enclosed by the reflector and the front cover lens or by the housing and the front cover lens, containing air which is in communication with the atmospheric air surrounding the headlight through the inlet and outlet openings of a duct which is formed by a tube, fabricated from substantially air-impermeable material, projecting from the outside into the interior of the headlight. A reversibly-acting hygroscopic desiccating agent is filled into the duct which provides only a slight resistance to the flow of air into, or out of, the interior of the headlight. The desiccating agent contained in the duct has such an area of contact with the moist air within the headlight that it will absorb enough of the moisture from the air within the headlight, even during the periods of time when the motor vehicle is standing idle, so that condensation of water within the headlight, due to falling temperature, will be avoided.