Electret HVAC filter are widely used to remove airborne particles in residential or commercial indoor environments. Based on the International Commission on Radiological Protection (ICRP) deposition model, sub-500 nm particles have enhanced depositions in the tracheobronchial region and the alveolar region than particles larger than 500 nm. In this study, filtration efficiencies of five residential electret HVAC filters against monodisperse silver (Ag) and potassium chloride (KCl) particles with 3–500 nm diameters at face velocities ranging 0.05–1.5 m s−1 were investigated. For further understanding the effect of fiber charges on particle collections, electret media were discharged and the efficiencies acquired from pure mechanical mechanisms were compared with that of electret media. The figure of merit (FOM) of the five electret filter media was also investigated to further understand the effect of charge density on filtration performance. A theoretical model without parametric fittings used in literature was adopted and further modified by considering the polarization forces for charged particles. The modified model predicted the particle penetrations very well at low face velocities for all tested media and also well at high face velocities for the media with low charges. The discrepancy occurred for the media with high charges at higher face velocities was due to the nonuniform particle concentration distribution in the media layers. The validated model is able to be applied to improve the design for electret media for nanoparticle removal.
Bibliographical noteFunding Information:
This work was supported by the NSF Grant (Award ID: 1236107) on " GOALIE: Unipolar Diffusion Charging of Spherical and Agglomerated Nanoparticles and its Application toward Surface-Area Measurement." This work was also supported by the National Natural Science Foundation of China (Award ID: 51404064), the Fundamental Research Funds for the Central Universities (Award ID: N130401002), the National Science and Technology Major Project of the Ministry of Science and Technology of China (Award ID: 2016YFC0801704, 2016YFC0203701, 2016YFC0801605), the National Key Technology Research and Development Program of the Ministry of Science and Technology of China (Award ID: 2015BAK40B00), the Key Technology Research on Major Accident Prevention of the State Administration of Work Safety of China (Award ID: Beijing-0003-2015AQ) and the Reform and Development Project of Beijing Municipal Institute of Labor Protection on " Performance Optimization of Respirator for Fine Particle". The authors thank the support of members of the Center for Filtration Research: 3M Company, A.O. Smith, BASF Corporation, Boeing Company, China Yancheng Environmental Protection Science and Technology City, Cummins Filtration Inc., Donaldson Company, Inc., Entegris Inc., Guangxi Wat Yuan Filtration System Co., Ltd., MSP Corporation, Samsung Electronics Co., Ltd., Shigematsu Works Co., Ltd., TSI Inc., W.L. Gore & Associates, Inc., Xinxiang Shengda Filtration Technique Co., Ltd. and the affiliate member National Institute for Occupational Safety and Health (NIOSH).
- Electret media filtration
- Electrostatic effect
- Figure of merit (FOM)
- Most penetrating particle size (MPPS)