COLONIZATION OF FIBERGLASS INSULATION USED IN HEATING, VENTILATION AND AIR-CONDITIONING SYSTEMS

The number of fungal species colonizing thermal and acoustic fiberglas s insulations used in heating, ventilation, and air conditioning (HVAC ) systems was fewer than that obtained from initial direct culture of these insulations. The colonization, determined by the microscopic obs ervation of conidiophores with conidia, was primarily of acrylic-latex -facing material, but eventually the fungi permeated the fiberglass ma trix. Isolates of Aspergillus versicolor were most often obtained from non-challenged insulation, whereas Acremonium obclavatum appeared to be the primary colonizing fungus in high-humidity (>90%) challenge cha mbers. At a lower humidity (about 70%) Aspergillus flavus was one of t he more prominent fungi. Not all duct liner samples were equally susce ptible to colonization and duct board appeared relatively resistant to colonization.