Temporal and spatial variation of fungal concentrations in indoor air

The aim of this study was to determine temporal and spatial variation of airborne concentrations of viable fungi in 2 single-family houses during the period of the year that such levels are mostly determined by indoor sources. One of the subject residences had moisture problems (the index residence), the other did not have any moisture problems (the reference residence). The concentrations of viable fungi in indoor air were determined a total of 6 times during the winter with 2 six-stage impactors (Andersen 10-800) in 2 rooms in both of the houses. The total concentrations of viable fungi and concentrations of Penicillium, Aspergillus, and Aspergillus versicolor were significantly higher in the index residence than in the reference residence. Statistically significant differences in the total concentrations were observed in the size ranges of 2.1-3.3 mum and 1.1-2.1 mum. In both residences, there was a statistically significant difference between the rooms in the total concentrations of viable fungi, although in the reference residence that was not of practical value because the levels were low. In concentrations of fungal genera, a significant difference, that was also of practical importance, was seen in the concentrations of Penicillium in the index residence. Both within-day and within-season differences of concentrations were observed in the residences: a trend of higher values in the morning and at the beginning of winter was noted. In order to characterize fungal concentrations of a residence with unknown indoor conditions, a sampling campaign of I I different days is needed. A strategy for responding to an alert or alarm situation is presented.