Comparison of effects of particle charging, media characteristics, humidity and aerosols on loading performance of electret media

Although electret filters are widely applied to mitigate suspended indoor particles, the filtration performance decreases significantly as operation time increases. The decline in filtration performance is affected by many factors, namely particle charging, media characteristics, relative humidity (RH) and particle composition. However, few studies have been conducted to evaluate the degrees of the influence of these factors in the loading performance of electret media. In this study, the medium efficiency electret media were firstly loaded with neutralized potassium chloride (KCl) at low RH to closely mirror common long-term filtration performances. Subsequently, the effects of the charge state of KCl, media characteristics, RH and particle composition on the loading behavior were investigated by changing the experimental conditions. The results showed that particle charging only mitigated the efficiency degradation, while other factors, i.e., media characteristics, RH and particle composition, could completely change the trend of the efficiency decline. The major conclusions were as follows: 1) Particle composition had the most remarkable effect on the loading performance; 2) RH produced a larger effect on the loading behavior than medium characteristics if it could affect the surface morphology of the particles. Otherwise, medium characteristics had a more significant impact; 3) Particle charging had a minimum influence when compared to other factors. The results obtained in this paper can be effectively utilized in the design and application of electret filters. © 2020 Elsevier Ltd