Damage layer formation on buildings is due to the deposition of atmospheric pollutants and their interaction with the underlying materials. The composition of black crusts is therefore closely related to the characteristics and levels of pollution in the surrounding environment. Thus, the study of its constituents is of fundamental importance in planning strategies for the protection and conservation of monuments and historic buildings. Damage layers have been shown to be primarily composed of carbonaceous particles embedded in gypsum, pointing to the overwhelming role of combustion-derived air pollution in their formation. The identification and evaluation of elemental carbon and other carbon species constituting the non-carbonate fraction of total carbon is required in investigating the damage on historic buildings in urban areas. The removal of organic carbon is a critical step in the analytical methodologies used for the measurement of elemental carbon. The paper describes a study performed on black crust samples from historic buildings of two Italian towns, on which the carbon compound discrimination was achieved by applying an analytical methodology based on thermal analysis. (C) 2003 Elsevier Science B.V. All rights reserved.