Abstract: An air introduction assembly for a vehicle engine located with respect to a roof mounted air deflecting member to perform an air cleaning or contaminant separating function. The air inlet is placed in a plane substantially parallel to the surface of the deflector over which air flows during vehicle movement and opens normally to the direction of the air flow. Air passing thereover which enters the inlet must be diverted in an arcuate path which causes contaminant particles to pass the inlet. The air inlet is partially defined by a forward peripheral edge portion offset outward from the surface of the air deflector so that a moving contaminant-laden layer of air immediately adjacent the deflector surface is excluded from entering into the inlet. Leading from the inlet is an air passage which tangentially introduces the air entering the inlet into a cylindrical separator chamber.