Deterioration of materials and objects of cultural heritage is a process which
occurs at a rate which is determined by meteorological parameters such as
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relative humidity, temperature and precipitation, and by air pollutants. Since the
time of wetness and temperature exhibit only small variations in the temperate
climatic zone, the concentration of atmospheric pollutants is often the dominant
variable affecting the rate of corrosion. Among the anthropogenic air pollutants,
SO2 can be considered as the most important in deterioration of several
materials. Many materials are affected; among them, e.g. stones used in historic
and cultural monuments, which have resisted atmospheric attacks for hundreds or
even thousands of years. But during recent decades, an accelerated degradation
of their surface has been observed in many parts of Europe