Fungal Emissions Rates and Their Impact on Indoor Air

Abstract

Data are needed that quantitatively relate fungal emissions from contaminated materials to airborne concentrations indoors, and subsequently to occupant exposure. However, the emission rates and mechanisms for fungal dissemination are poorly understood.
The preliminary experiments reported here have shown that fungal dissemintation in air ducts has complex interactions with humidity. To replicate levels of fungal growth to those documented in the literature, duct materials were allowed to develop microbial (Penicillium and Aspergillus) contamination in a constant temperature and high humidity environment. A known and constant air flow was maintained throughout. Almost no spore release was seen over 3 months of periodic sampling with constant exposure to 95% relative humidity (RH), while surface growth increased at least 2-3 orders of magnitude. After 3 months a series of experiments was initiated to investigate the impact of RH on fungal emissions. In these, the RH was varied and culturable fungal spore emissions were measured. The level to which the RH was decreased was inversely related to increasing emissions. To better understand the implications of the spore emissions rates measured in these experiments on indoor air quality (IAQ), an IAQ Model was used to estimate concentration and occupant exposure.