Abstract: To protect electronic components located within a housing structure, or casing, which contains ventilation openings, against corrosion due to intrusion of water, for example being sprayed thereon upon cleaning of the area on which the structure is mounted, the housing is formed with an attachment surface having ventilation ducts formed therein which are generally Y-shaped having two branch ducts terminating at the outside of the housing in spaced position, and forming an angle with respect to each other, for example terminating at essentially right angled housing edges, and a third trunk duct connected to the interior of the housing, and branching off from the two branch ducts, so that water sprayed against the housing may run through the branch ducts, without impingement on a back wall, and ventilation is provided by additional movement of air through the trunk of the Y-shaped duct; the ducts are preferably mounted with respect to the housing in such a manner that any liquid which might accumulate within the