A short series of tests was conducted to determine whether ground level point sources at the upwind stagnation point of a large building yielded peak-to-mean concentration ratios that were significantly different than those observed for ground level point sources in unobstructed flow. Time-average concentrations over test periods of 6-15 min were measured to delineate the spatial extent of the plume for both types of flow conditions. Also, 5-sec averages of concentration at a point near the centerline of the plume were measured to indicate the time history of concentration. The results indicated that there was no detectable difference between peak-to-mean ratios measured in unobstructed flow and in the lee of a building with a point source near the upwind stagnation point. Because of the strong dependence of wake diffusion on source location, no conclusions were possible concerning peak-to-mean ratios from sources located at sites other than the upwind stagnation point. © 1969.
