Abstract: The invention relates to a filtering device with a filter housing which can accept a filter mat, is covered with a lamella grid on the outlet side and is fitted in an aperture in a mounting wall. RF screening is attained without altering the structure of the filtering device in that the surface of the filter housing is electrically conductive and inserted in the aperture in the mounting plate via an electrically conductive contact frame. The contact frame is electrically connected to the filter housing and the aperture in the mounting plate and there is an electrically conductive screening grid inserted or mounted in the filter housing or between the latter and a fan which can be linked thereto.