Fungi, a specialized group of microorganisms are dangerous agents inside library which are not only responsible for paper deterioration and ageing of books in the library but also significantly affect health of the library staff. The deterioration of library material by microorganisms has attracted attention in recent years. Efforts have been made towards reduction of these losses by finding out the conditions, causes and weather conditions, which incidentally contribute to the deterioration of library books and other materials. The role of fungal agents in deterioration is due to their hydrolytic enzyme activity. The cellulytic activities cause maximum damage to paper. Investigations by the exposed culture plate method helped in determining the composition and percentage contribution of the various constituents of airspora inside library. Isolated fungi were identified and classified on the basis of their characters with the help of authentic literature. It was observed that the deteriorating activity of fungi changed with respect to the paper type. The fungi observed in the study includes Aspergillus niger, A. flavus, A. fumigatus, A. spp., Alternaria alternata, Alternaria spp., Curvularia spp., Fusarium spp., Rhizopus spp., Penicillium spp., Chaetomium spp., Helminthosporium spp., Geotrichum spp., Drechslera spp. Fungi like Aspergillus niger, Chaetomium, Penicillium, Rhizopus and Alternaria were also isolated from the books in the libraries.