This project documented, analyzed, and interpreted atmospheric pollution encrusted on the facades of Columbia’s Avery Hall, treating the existing building as a long-term passive environmental sensor that records past microclimates. Using LiDAR, XRF, CFD, and both terrestrial and aerial photogrammetry aligned with precise GPS control, we produced a unified 3D photo-textured surface model to map, isolate, and visualize dust layers on the facade. The research asks whether discernible patterns in how dust settles can be detected, what these patterns reveal about historical weather conditions and environmental pollution, and whether buildings across the city can be “read” as environmental archives. Ultimately, the project reflects on what is lost when these dust layers—and the environmental histories they encode—are erased through cleaning and maintenance.