Abstract: A ventilation system for use, in example, on a spray booth or paint stripping enclosure, in which variable speed fans (or equivalent) are employed, and controlled by a sensor so that the flow rate exhausted from the booth (and directed either to an emission control device or vented to atmosphere) is continually adjusted to minimize the exhaust flow rate from the enclosure. The remainder of the ventilation air is recirculated back into the enclosure. An analyzer located in the recirculation duct continuously monitors the concentration of hazardous constituents present in the recirculation stream, and transmits this data to a central controller, which controls the ventilation fan systems. The central controller controls the recirculation duct and exhaust duct fan systems to achieve the highest recirculation rate possible, yet also maintain constituent concentrations in the recirculation duct at a safe level.

Abstract: A facility including a booth for solvent or paint application or drying process is provided with ventilation inlets and outlets to cause stratification of constituents such as VOCs or particulate in the booth. The ventilation air withdrawn from the booth is split into two air streams, one air stream contains a relatively low volatile organic compound (VOC) concentration, and the other a relatively high VOC concentration. The ventilation air from the low concentration stream is vented to the atmosphere (or alternatively back in the booth) and the ventilation air from the high concentration stream is conducted to a VOC emission control device. Thus, adequate VOC emission control is achieved, and the volume of air processed by the VOC emission control device is reduced, along with the corresponding VOC emission control costs.