Microbial contamination levels and influencing factors in filters for residential outdoor air systems

In this paper, four outdoor air systems of different residential buildings in cold zone are selected to detect the bacterial and fungal contamination levels in their primary, medium, and high and medium efficiency filters. The effects of temperature, humidity, and air quality index (AQI) on the bacterial and fungal concentration in the filters are analysed. A regression model is established between outdoor microbial concentrations and air pollution factors. The results show that the microbial concentration in the primary efficiency filter ranges from 104to 1010CFU/m3. The bacterial concentration in the medium and high and medium efficiency filters ranges from 102to 107CFU/m3, and the fungal concentration ranges from 10-1to 106CFU/m3. The microbial concentration in the filters is positively correlated with temperature, humidity, and air quality index. The outdoor microbial concentration is positively correlated with the concentrations of NO2, O3, and SO2, and the impact of O3concentration is the greatest. The main fungi existing in the tested filter includeAspergillus,Penicillium, etc.