Ultrafine particle removal by residential heating, ventilating, and air-conditioning filters


  • B. Stephens,

    Corresponding author
    1. Department of Civil, Architectural and Environmental Engineering, Illinois Institute of Technology, Chicago, IL, USA
    • B. Stephens

      Department of Civil, Architectural and Environmental Engineering

      Illinois Institute of Technology

      Alumni Memorial Hall Room 212

      3201 South Dearborn Street

      Chicago, IL 60616


      Tel.: (312) 567-3356

      Fax: (312) 567-3519

      e-mail: brent@iit.edu

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  • J. A. Siegel

    1. Department of Civil, Architectural and Environmental Engineering, The University of Texas at Austin, Austin, TX, USA
    2. Department of Civil Engineering, The University of Toronto, Toronto, ON, Canada
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This work uses an in situ filter test method to measure the size-resolved removal efficiency of indoor-generated ultrafine particles (approximately 7–100 nm) for six new commercially available filters installed in a recirculating heating, ventilating, and air-conditioning (HVAC) system in an unoccupied test house. The fibrous HVAC filters were previously rated by the manufacturers according to ASHRAE Standard 52.2 and ranged from shallow (2.5 cm) fiberglass panel filters (MERV 4) to deep-bed (12.7 cm) electrostatically charged synthetic media filters (MERV 16). Measured removal efficiency ranged from 0 to 10% for most ultrafine particles (UFP) sizes with the lowest rated filters (MERV 4 and 6) to 60–80% for most UFP sizes with the highest rated filter (MERV 16). The deeper bed filters generally achieved higher removal efficiencies than the panel filters, while maintaining a low pressure drop and higher airflow rate in the operating HVAC system. Assuming constant efficiency, a modeling effort using these measured values for new filters and other inputs from real buildings shows that MERV 13–16 filters could reduce the indoor proportion of outdoor UFPs (in the absence of indoor sources) by as much as a factor of 2–3 in a typical single-family residence relative to the lowest efficiency filters, depending in part on particle size.