Abstract: A spray application system is disclosed having an enclosure with a spray chamber, a spray applicator within the chamber, and a liquid barrier such as a sprayed water curtain, within the chamber, upstream or downstream of the spray applicator. The water is preferably sprayed downward to create a vacuum for drawing the treating substance downward into the liquid barrier. The liquid barrier preferably does not contact the workpieces that instead pass overhead. Independent pressure gauges and flow regulators may be used for the upstream liquid barrier, the downstream liquid barrier, and the spray applicator. The chamber may have a roof section that is secured to a beam or other process line support, and the walls may be suspended from the roof section. The roof section may have an opening running across its length to allow hangers from an overhead processing line to pass through the chamber.