NCPTT operates a one-of-a-kind custom exposure chamber to study the interaction
between air pollution and cultural materials. The chamber was designed and built
in 1987 by the National Park Services (NPS) in partnership with the National Oceanic
and Atmosphere Administration (NOAA) and the U.S. Geological Survey (USGS.) It was
moved to NCPTT from Virginia in 1996.
The chamber is one of only three of similar
capabilities in the world. It is a re-circulating wind tunnel that allows precise
control of temperature, humidity, wind speed, pollution concentration, and turbulence.
Up to eight samples such as limestone and marble, can be exposed at a time. Samples
are typically exposed for 10 days under conditions comparable to Philadelphia in
the springtime.
Following exposure, the samples are then shaken in a hydrogen peroxide
solution to convert the absorbed sulfur dioxide to sulfates in solution. The resulting
washes are analyzed upstairs in the Wet Lab via Ion Chromatography.