This system is for ventilating a housing or a housing portion that has to
house a contents (39) and has ventilation grids (33, 35) for the contents,
the grids being formed from segments of material leaving a gap between
them, characterized in that these segments of material are arranged at at
least two levels (9a, 9b) offset depthwise in the general direction of
entry of a gaseous fluid into the housing or the housing portion through
the grid in question, in order to constitute, by grid, a multiple-grid
system, the grids being offset depthwise with respect to one another.
