Application of pre-filter system for reducing indoor PM2.5 concentrations under different relative humidity levels

Abstract

In most urban environments, outdoor air pollutants affect indoor air quality. In 2019, Seoul, South Korea mandated filtered ventilation systems in newly constructed buildings to reduce PM2.5 levels. This study aimed to evaluate PM2.5 concentrations before and after the installation of a pre-filter and to analyze their behavior under different relative humidity conditions. The pre-filter system was installed in two selected houses (A and B) with the same ventilation system to evaluate indoor and outdoor PM2.5 concentrations. To reduce indoor PM2.5 concentrations through the ventilation system, a high-performance filtering system (G4 + F8 + H13) was installed. The ventilation system was better at maintaining indoor air quality than an air cleaner. Furthermore, the pre-filter was more effective in reducing PM2.5 that was introduced from the outside rather than that generated indoors. The results revealed that after installation of the pre-filter system, the percentage of PM2.5 concentration below 10 μg/m3 increased for house A and B, respectively. In addition, when the pre-filter was not installed, the average I/O ratio was 1.4 ± 0.09 and 2.3 ± 0.09 for house A and B, respectively. However, after the pre-filter was installed, the average I/O ratio for house A was 0.4 ± 0.58 and that for house B was 2.1 ± 0.05. After pre-filter installation, the percentage of I/O ratio (range of 0–1) increased with an increase in the relative humidity, that is from 72.1% to 95.1% for house A and from 8.5% to 24.7% for house B.