Abstract
When multiple sources release contaminants a short distance above the roof of a building, the gases are usually trapped in the eddy zone or cavity adjacent to the roof and side walls, and undesirably high concentrations may be produced at air intakes in the side walls. Since the side walls generally are regions of minimum concentration for exhausts located on the roof, the only recourse to effect a further reduction in concentration is to deposit some of the effluent outside of the cavity. This paper presents a method for calculating the stack height necessary to produce an arbitrary concentration at the side-wall intakes, by evaluating the partial entrapment of the plume in the cavity.