Based on the results of this investigation, there appears to be surprisingly little impact on urban air quality during wildfire events. This is in contrast to the recorded visibility impacts that the wildfires have had on the metropolitan area. The lack of high PM concentrations may be due to Tucson's topography, the location of the air quality monitors, or the rapid dispersion of PM. Spatial and temporal analyses have been employed to better delineate the factors involved, including in-depth, daily analyses over the period of the large Bullock and Aspen fires that occurred in 2002 and 2003. Although several days indicate overall elevated PM conditions, the data are not distributed in the expected spatial pattern and are not in synch with wind direction or synoptic conditions. The magnitude of the air quality impacts varies based on the temporal and spatial unit of analysis, however, emphasizing the importance of scale in study design.