Abstract: In a building, a ventilating hood is disposed over a kitchen cooking unit. The hood has an exhaust duct and a return duct, both extending through the roof to the exterior of the building. An exhaust blower is connected to the exhaust duct, and an intake blower is connected to the intake duct outside the building. The hood includes an air filter which has a plurality of fresh air conduits extending therethrough. The ventilating system removes smoke, vapors and cooking odors from the work area disposed over the cooking unit and provides fresh air to the same work area. The smoke, vapors, cooking odors and the like pass through the air filter on their way to the exhaust duct, while air from the intake duct is directed through the filter air conduits such that the exhausted, heated air preheats the fresh air returned from the hood to the work area above the cooking unit.