The paper discusses a project designed to evaluate the feasibility of using a membrane-supported extraction and biotreatment process to meet the National Emissions Standard for Hazardous Air Pollutants (NESHAP) for aircraft painting and depainting facilities. The proposed system will both minimize the treated volume and concentrate the volatile organic compounds (VOCs) within the treated volume to further reduce the size and cost of the control equipment. These advantages make this VOC treatment option viable over a broad range of spray booth sizes. This will be accomplished using the partitioned recirculation flow reduction technique and a novel VOC concentrating and biological treatment process, the Membrane BioTreatment (MBT) system. In the MBT system, VOCs are first separated from the air stream, concentrated, then metabolized by microorganisms, formign cell mass and carbon dioxide.