At least one side wall area of a casing, suitable for small electronic
devices such as hearing aid devices e.g. for the use in environment with
elevated humidity, is proposed to be porous or perforated. On the outside
surface of the casing a fleece is arranged on the said side wall area,
which fleece does have a higher porosity or pores with a smaller diameter
respectively than the pores or openings within the said side wall area of
the casing. The side wall area can be e.g. a cover or lid respectively,
which is covered on its outer surface with the said fleece. The fleece
preferably is a "non-woven" consisting of polymer fibers such as e.g.
polyester fibers. The casing cover or lid respectively can be e.g. a cover
of a receptacle for batteries.
