The air in the Southern Hemisphere (left side; day 55 of 1999) was pristine, and filter papers are almost indistinguishable for unexposed filters. In the Northern Hemisphere (right side; day 65 of 1999) wind blown mineral dust produces relatively large particles as seen by the red-gray stripes, and combustion processes generate smaller particles of sulfate, organic compounds, and soot that stain the filters black. For this impactor, fine corresponds to particles of 0.24 to 0.48 um and coarse corresponds to particles of 0.74 to 1.5 um diameter.