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Volume 16, No. 7, July 2016, Pages 1722-1729 PDF(520 KB)  
doi: 10.4209/aaqr.2015.08.0494   

Removal Efficiency of Bimodal PM2.5 and PM10 by Electret Respirators and Mechanical Engine Intake Filters

Sheng-Chieh Chen1, De-Qiang Chang1,2, Chenxing Pei1, Chuen-Jinn Tsai3, David Y.H. Pui1,4

1 Particle Technology Laboratory, Mechanical Engineering, University of Minnesota, 111 Church St., S.E., Minneapolis 55455, USA
2 Filter Test Center, College of Resources and Civil Engineering, Northeastern University, NO. 3-11, Wenhua Road, Heping District, Shenyang, Liaoning 110819, China
3 Institute of Environmental Engineering, National Chiao Tung University, 1001 University Road, Hsinchu, 300, Taiwan
4Faculty of Science, The University of Hong Kong, Chong Yuet Ming Physics Building, Pokfulam Rd., Hong Kong


  • PM2.5 in China becomes a serious problem and impacts its neighboring counties.
  • A system generating PM2.5 and PM2.5–10 and evaluating respirator and engine filters.
  • Engine intake filters had low efficiency for PM2.5 with only 25–30%.
  • The current respirators can efficiently remove PM2.5 and PM10.
  • Lower PM2.5 efficiency was determined by the system than that by photometer.



As China is receiving an economic boom, PM (particulate matter) pollutions not only have become a serious regional problem but also frequently impacted its neighboring counties, e.g., Korea and Japan. In addition to its adverse effects on human health, the on- and off-road engines operated in ambient can also be affected. In this study, a simple system for generating simulated ambient bimodal PMs comprising fine (PM2.5), coarse (PM2.5–10) particles was developed for evaluating the initial efficiency of seven respirator and four engine intake filters. In addition to the size fractional efficiency curves for each filter media determined from the SMPS (scanning mobility particle sizer) and APS (aerodynamic particle sizer), both number and mass based efficiency of these filters for PM2.5, PM2.5–10 and PM10 were also obtained to evaluate their performances against ambient PM pollutions. Data showed that the engine intake filters had a low efficiency for both mass and number based PM2.5, which was only about 25–30%. However, there was a large difference between their number and mass based PM10 efficiency. The former was much lower than the latter because these filters are with high efficiency only for coarse particles. Besides, the most of particles in number is resided in the fine size range while the mass is in coarse size range. For the respirator filtration tests, results showed that most of them can effectively remove both PM2.5 and PM10, in which the mass efficiency was always higher than that of number. The PM2.5 number efficiency results showed there are three out of seven respirator filters are with N-95 rated level, in which the efficiency of their most penetrating particle size is higher than 95%. The current simple experimental system could be applied to examine different purpose filters which protect human health and outdoor engines against ambient PM2.5 and PM10.



Keywords: PM2.5 in China; PM2.5 health effect; PM10; Bimodal ambient PM; Electret respirator; Mechanical engine intake filter; Long range transport.



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