Growth of fungi on fiberglass insulation materials

New and used thermal and acoustic fiberglass duct liners and duct boards were examined for their ability to support the growth of fungi. Used fiberglass duct liners and duct boards from buildings whose occupants complained of unacceptable or mouldy odors in the air were found to be heavily colonized by fungi, particularly by Aspergillus versicolor. The fiberglass duct liners from some of these sites appeared relatively clean and uncolonized, by visual examination, had been in place for less than five years, and yielded dense growth of essentially pure cultures of A. versicolor. Other samples of indeterminate age, yielded three to five species of fungi when cultured. Samples of duct board from one building had growth primarily in the glue layer between the vapour barrier and the fiberglass. Stachybotrys atra which may produce a potent mycotoxin, satratoxin H, was observed and cultured from this layer from several samples.;Seventy-one out of 116 sections of unused fiberglass yielded fungi on initial culture, including A. versicolor and Cladosporium herbarum. The unused fiberglass also was found to be susceptible to fungal colonization (growth with development of conidiophores and conidia) in environmental chambers dependent upon relative humidity. Although more than twenty fungal species were identified from initial cultures of the fiberglass, only five species were found to colonize the fiberglass in the chambers. The duct liners were more readily colonized than the more rigid duct boards. Whereas Acremonium obclavatum was the predominant colonizer at humidities above 95%, Aspergillus versicolor dominated from 65% to near 90% relative humidities. No colonization was observed at relative humidities below 50%.;Both Acremonium obclavatum and Aspergillus versicolor produced volatile organic compounds (VOC) in culture including benzene (classified by both the EPA and OSHA as a hazardous chemical), 2-ethyl hexanol and cyclohexane (known eye and skin irritants). Some of these compounds, in particular benzene and 2-ethyl hexanol were produced directly from duct liners colonized by a mixed population of fungi. There is a possible relationship of these volatiles with poor indoor air quality and the "sick building syndrome".