Ventilated enclosure

A ventilated enclosure formed by an air duct, one end of which is closed off by a partition having ventilation apertures and the other end of which is closed off by a wall having openings adapted to provide for the passage of air, at least two fans supported to said wall and adapted to be energized to cause air to be drawn into the interior of the enclosure from its exterior, each said fan including a detection device for detecting inadequate ventilation within the enclosure, each said detecting device being positioned in the area which is swept by the stream of air produced by the associated fan when energized, each said detecting device including means for generating a signal when the output of air from this fan falls below a predetermined limiting value, said means consisting of a thermal detection element to emit a signal when its temperature becomes equal to a predetermined temperature threshold, and an air non-return casing, said thermal detection element being supported within said casing and said casing being so constructed and arranged so as to have pass through it only a fraction of the air output from the associated fan, said fraction of air being such that, when the output from the fan is equal to the said predetermined limiting value, the temperature which prevails within the casing is equal to the said predetermined threshold.