The moisture requirements of moulds isolated from domestic dwellings

Abstract Mould growth on the damp internal surfaces of buildings is estimated to occur in some 2·5 million dwellings in the UK. As moisture is regarded as the key factor in promoting mould growth in buildings, a study was carried out to determine the moisture requirements for growth of moulds isolated from domestic dwellings, with the intention of providing building operators and practitioners with information on critical internal humidity levels. Nineteen species of moulds which occurred in at least 10% of domestic air samples were assessed for their ability to grow at different levels of water activity (Aw:Aw = RH/100). Certain of these were selected for more detailed studies of their Aw requirements for growth on a range of building substrates including paint and woodchip wallpaper. The lowest Aw level recorded for growth on malt extract agar was 0·76 (76% RH) for Aspergillus repens, while for A. versicolor and several Penicillium species the minimum value was 0·79. On woodchip wallpaper painted with an emulsion paint the Aw minimum for A. versicolor and P.

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