An apparatus and article is disclosed for separating intake air from exhaust air. The apparatus discloses an intake port, coupled to conduct intake air; an exhaust port, coupled to conduct exhaust air; and an air-curtain port, coupled to conduct air-curtain air to separate at least a portion of the intake air conducted by the intake port from the exhaust air conducted by the exhaust port. The article discloses a ductwork shell article, having an intake vent, an intake chamber, an exhaust vent, an exhaust chamber, an air-curtain vent, and an air-curtain chamber; wherein: the air-curtain vent is in part located between the exhaust vent and the intake vent.