Chemical–physical and microbiological measurements for indoor air quality assessment at the Ca’ Granda historical archive, Milan, Italy

In a few cases, atmospheric particulate matter characterization was taken into account together with aerobiological monitoring but never in an archive. The aim of this study was to estimate the air quality, by means of both chemical–physical and microbiological studies, at the Ca’ Granda Historical Archive (Milan, Italy) that houses an important collection of documents from the 12th century. Temperature and relative humidity were measured in the rooms. Particulate matter (PM2.5) concentrations were quantified and the chemical composition, in terms of ionic components, elements, and carbonaceous fraction (total, organic, and elemental carbon) determined. The gaseous pollutants NO2, SO2, and O3 and indoor acidity were also measured. Aerobiological monitoring (aerobic heterotrophic bacteria and fungi) was performed as volumes stored in the Archive were composed of organic materials, a potential energy and carbon source. In this paper, we present our findings and propose some guidelines for a better preservation of the documents.