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Volume 16, No. 12, December 2016, Pages 3349-3357 PDF(380 KB)  
doi: 10.4209/aaqr.2016.10.0437   

Capture of Sub-500 nm Particles Using Residential Electret HVAC Filter Media-Experiments and Modeling

De-Qiang Chang1,2, Sheng-Chieh Chen2, David Y. H. Pui2

1 Filter Test Center, College of Resources and Civil Engineering, Northeastern University, Liaoning 110819, China
2 Particle Technology Laboratory, Mechanical Engineering, University of Minnesota, Minneapolis 55455, USA


  • Five residential electret HVAC filters against nanoparticles with 3–500 nm.
  • Effect of fiber charges on particle collections was studied by discharging media.
  • Model without parametric fittings used in literature were adopted and modified.
  • Modified model predicted the particle penetrations very well.
  • Validated model able to improve the design of electret media for particle removal.



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.



Keywords: Electret media filtration; Electrostatic effect; Nanoparticles; Figure of merit (FOM); Most penetrating particle size (MPPS).



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