Evaluation of fungal growth on fiberglass duct materials for various moisture, soil, use, and temperature conditions

Fiberglass duct materials are commonly used in both residential and commercial heating, ventilation, and air-conditioning (HVAC) systems to provide the needed thermal insulation and noise control. Many building investigations have documented biocontamination of these materials, and the appropriateness of their use in high humidity locations has come into question. A series of experiments, each lasting 6 weeks, was conducted in static environmental chambers to assess some of the conditions that may impact the ability of a variety of fiberglass materials to support the growth of a fungus, Penicillium chrysogenum. Three different fiberglass duct liners (FDL), one fiberglass duct board, and fiberglass insulation, all newly purchased, were obtained as were samples of used (>5 years old) materials. Samples of these materials were tested to evaluate the effects of moisture, soil, use, and temperature on their ability to support the growth of P. chrysogenum. These studies demonstrated that P. chrysogenum could amplify under conditions of low (12 degrees C) and room (23 degrees C) temperature and high relative humidity on samples of one of the newly purchased materials, and that either wetting and/or soiling increased the materials' susceptibility. P. chrysogenum was able to grow on all the used material samples. While the results of this study apply directly only to fiberglass duct materials, they suggest that dust accumulation and/or high humidity should be properly controlled in any HVAC duct to prevent the growth of P. chrysogenum.