The purpose of this paper is to analyse the mould growth and yeast contamination in libraries building. The mould growth causes identified during an investigation and visual inspection of Library PTAR building. The mould contamination level had been measured using 3M Petrifilm Rapid Yeast and Mould Count Plate. The objective of the measurement is to detect environmental concentration for indoor library environment using swab contact monitoring procedures and air sampling procedures. The result recorded yeast and moulds colonies on the 3M Petrifilm with variably pigmented colonies with certain characters. The yeast colonies recorded are small, tan colonies with defined edges and no foci while the mould colonies are with diffuse edges and centre foci. They are large, crowd, sporulate and overlap each other on the plate. The result confirmed high contamination count using swab contact, and low contamination recorded using air sampling procedure. © 2016 Taylor & Francis Group, London.