The system comprises means for supplying into the inner space of the passenger compartment two series of air flows, and namely a first series of substantially pulsating air flows, each of which pulsating air flows is cyclically interrupted for a pre-established period of time, the said flows of the first series being supplied into the upper region of the said space, in which region normally the heads of the passengers in the said passenger compartment are situated, and a second series of substantially continuous air flows, the said flows of the second series being supplied into the low region of the said space.