Abstract: The apparatus is adapted to provide for the controlling of incoming replacement or make up air in a cooking equipment ventilation system. The apparatus is dependent upon an air plenum surrounding the hood or an enclosure which contains the incoming, unconditioned make up air. The air is discharged into the cooking primarily by adjustable air controllers. The controllers are located at the lower lateral edge of the hood. The direction of the incoming replacement or make up air can be directed as desired for the required thermal conditions. The apparatus can be an integral part of a new ventilation hood assembly or system, or can be retrofit to a ventilation hood assembly or system already in operation.