Over the period July 1996–April 1998, airborne particle concentrations and chemical composition were measured both inside and outside the new J. Paul Getty Museum outside Los Angeles. The purpose of these experiments was to determine the relationship between the stages of construction and operation of the building and the soiling hazard to the collections. Particular attention was paid to tracking the concentrations of fine black soot particles and mineral dust particles. The time needed to “air out” the building following construction can be seen from the data collected, as well as the inherent particle removal efficiency of the filters within the building ventilation system, and the effect of entry of the general public into the building. During the period of observation when the building was under construction, weekday coarse dust particle concentrations on occasion reached very high levels ( 600–1,100 μg m−3 ; 24 h average), falling to relatively low values averaging 26 μg m−3 over weekend periods whe...