This paper summarizes the results of the research study conducted for the ASHRAE Technical Committee (TC) 4.3 on stack ganging. The purpose of the research was to quantify the benefits of ganging (i.e.@ placing next to one another) exhaust stacks to increase the throw or rise of exhaust plumes@ thereby reducing adverse air quality impacts without directly manifolding the exhausts or using induced air systems. The research used wind tunnel modeling to develop a database of plume rise observations for various ganged stack configurations. The plume rise measurements were analyzed to determine a plume rise enhancement factor based on the relative positions of the ganged stacks. The results of this research can be used to optimize the layout of ganged stacks such that maximum plume rise can be achieved for all wind directions.