LAUSR

Abstract Interaction between relative humidity (RH) and hygroscopic particles significantly affects the filtration performance of electret media. To investigate the interaction effect between RH and hygroscopic particles on the loading characteristics, electret media were loaded with potassium chloride (KCl) at ∼30% and ∼75% RH, respectively. Then, to study the effect of RH change on the filtration performance, media loaded at low RH were exposed to air with higher RH. Results showed that electret media loaded at 75% RH experienced a continuous efficiency degradation from 74 to 38%, and the pressure drop only increased by 1 Pa. Because the collected particles deposited on fibers as isolated particles, instead of the dendrites occurred at low RH. After exposing loaded samples to air with RH higher than the loading RH, the efficiency and pressure drop decreased significantly: the efficiency and pressure drop decreased from 74 to 44% and from 37 to 16 Pa within 3 min, respectively, when samples preloaded at ∼30% RH were treated with ∼75% RH. Due to the water adsorption at higher RH, the dendritic structures formed by the collected particles on fibers were damaged, affecting the filtration performance. This work will offer important guidance for practical applications of electret filters.