The effects of filters for an intelligent air pollutant control system considering natural ventilation and the occupants

Experimental analysis was conducted on the indoor air pollutant concentration using natural ventilation and filters. The study targeted two office rooms each of which was occupied by four people, and with the same outdoor environments. A non-woven fabric filter (room A) and an electrostatic filter (room B) were installed on the window frame, and the indoor air pollutant concentration and indoor climate factors were monitored based on the number of occupants and the occupants’ activities. The results are as follows: (i) when the number of occupants in each room increased from 0.03–0.06 to 1.53–1.63, room A showed a 60% average PM₁₀ concentration increase while room B showed an opposite result (10% average PM₁₀ concentration decrease), meaning the electrostatic filter's lower resistance to flow contributed to better ventilation and also decreased the influence of the occupants on the indoor air pollutant concentration. A low correlation (0.323–0.350) between the CO₂ concentration and the occupants in room B also proved these results; (ii) while the average PM₁₀ concentration in room A was 9 μg/m³ higher than that in room B, the average PM_2.5 concentration in room A was higher by only 0.2 μg/m³, which showing that much of the generated or resuspended indoor particulate matter was PM₁₀; and (iii) due to the more frequent heat transfer from outdoors to indoors, room B consumed 23% more heating energy. The results of this study are expected to be used as bases for the establishment of an appropriate management strategy that considers the indoor air pollutant concentration caused by the number of occupants and occupants’ activities by combining natural ventilation and filters.