This study investigated the types of fungi found on gypsum wallboard obtained directly from the manufacturing production line. Samples were cut into 4 — 4 cm pieces and incubated at 20 °C under three different moisture conditions; 95%RH (approximately 2.5% saturation moisture content), 0.1 Sat. MC (10% saturation moisture content), and 0.2 Sat. MC (20% saturation moisture content). The moisture levels used in this study were selected to span a wide range of moisture conditions and are not representative of what would be found in well maintained, properly ventilated buildings. In particular, the partially saturated moisture levels would be found under building conditions that would be associated with water leakage from damaged roofs or wall siding, faulty plumbing, or thermal conditions that result in condensation on cold surfaces. A portion of the samples was fumigated with ethylene oxide and subjected to the same test conditions to test the efficacy of this method for sterilizing gypsum-based materials. At five weeks, all six sides of the samples were examined microscopically and acetate tape slides were made of the different fungi observed for further identification. A total of eleven different fungal genera were identified. Penicillium spp. and Aspergillus spp. were the only types found at 95%RH. The number of types of fungi seen increased with increasing moisture content. At 95%RH growth occurred almost exclusively on the paper face surfaces, while at increasing moisture levels greater numbers of fungi were found on the gypsum core surfaces. These findings suggest that, although there is a wide variety of fungi present on "new" gypsum wallboard, there is very little growth of only a few types of fungi under non-wetting conditions even at prolonged conditions of high humidity, and at moisture levels that represent wetting conditions, some of the species present only grow on exposed gypsum core and not the paper faces.

Authors:Susan C. Doll, Harriet A. Burge, Ph.D.

Citation:Indoor Air Quality 2001 Moisture, Microbes, and Heath Effects: Indoor Air Quality and Moisture in Buildings Conference Papers

Keywords:November, California, 2001, IAQ