Levels of indoor airborne microbes are associated with ventilation rates in naturally-ventilated residences

Homes with natural ventilation is a predominant type of residential buildings in taiwan . As high microbial concentrations have been reported.in those buildings, the authors have studied the effects of ventilation efficiency on indoor/outdoor levels of airborne microbes in 44 homes with natural ventilation.
Indoor and outdoor airborne bacteria and fungi were collected and the air change rate (ACH) was measured by tracer gas concentration decay method.
Results have suggested higher air change rate in residences with natural ventilation may increase indoor microbial levels of outdoor origin mainly with absence of proper filtration.