The Effectiveness of a Mechanical Ventilation System for Indoor PM 2.5 in Residential Houses.

The mechanical ventilation systems used in houses are designed to reduce carbon dioxide emissions while minimizing the energy loss resulting from ventilation. However, the increase in indoor fine particulate (PM 2.5 ) concentration because of external PM 2.5 influx through the ventilation system poses a problem. Here, we analyzed the changes in indoor PM 2.5 concentration, distinguishing between cases of high and low outdoor PM 2.5 concentrations and considering the efficiency of the filters used in residential mechanical ventilation systems. When using filters with the minimum efficiency reporting value (MERV) of 10 in the ventilation system, the outdoor PM 2.5 concentration was 5 μg/m³; compared to the initial concentration, the indoor PM 2.5 concentration after 60 min decreased to 73%. When the outdoor PM 2.5 concentration was 30-40 μg/m³, the indoor PM 2.5 concentration reached 91%. However, when MERV 13 filters were used, the indoor PM 2.5 concentration consistently dropped to 73-76%, regardless of the outdoor PM 2.5 concentration. Furthermore, by comparing the established equation with the mass balance model, the error was confirmed to be within 5%, indicating a good fit. This allows for the prediction of indoor PM 2.5 under various conditions when using mechanical ventilation systems, enabling the formulation of strategies for maintaining indoor PM 2.5 , as recommended by the World Health Organization.