Dispersal of spores from fungal-contaminated duct material.

Fungal-contaminated air handling systems have been implicated as a source for the dispersal of spores into the indoor environment, potentially serving as a route of exposure to building occupants. Because quantitative data are lacking, this study was conducted to measure the dispersal of spores from fungal colonies growing on three types of duct material: galvanized metal, rigid fibrous glass ductboard, and fiberglass duct liner. Duct materials were soiled, contaminated with a known concentration of Penicillium chrysogenum spores, and incubated in humidity chambers to provide a matrix of growing, sporulating fungal colonies. The contamination level following amplification was 109 CPU/duct section, with no significant difference between duct materials. For each experiment, a contaminated duct section was inserted into the air handling system of a bioaerosol research experimental room, and the air handling system was operated for three 5-minute cycles with an air flow rate of 4.2 m3/min. The duct air velocity was approximately 2.8 m/sec. The airborne concentration of culturable P. ch1ysogenum spores (CFU/m3), total P. chrysogenum spores (spores!m\ and total P. chrysogenum-sized particles (particles/m3) were measured in the room using Andersen single stage impactor samplers, Burkard slide impactor samplers, and an aerodynamic particle sizer, respectively. The highest airborne concentrations were measured during the first operating cycle of the air handling system for all duct materials with decreasing airborne concentrations measured during the second and third cycles. There was no significant difference in spore dispersal from the three contaminated duct materials. These data demonstrate potential exposure for building occupants to fungal spores dispersed from contaminated duct material during normal air handling system operation.