10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
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Estimates of Fine and Ultrafine Particle Removal Efficiency for Residential HVAC Filters Using In-Situ Size-Resolved Efficiency Measurements
TORKAN FAZLI, Brent Stephens, Illinois Institute of Technology
Abstract Number: 604 Working Group: Indoor Aerosols
Abstract Central HVAC filters are commonly evaluated for their size-resolved particle removal efficiency by challenging them with a test aerosol in a laboratory setting. However, aerosol classifications that are most commonly used in regulatory monitoring and building measurements typically include integral measures of mass-based concentrations or total number concentrations. Because filter test standards have not traditionally considered these measures, building owners, occupants, and other key personnel cannot make informed decisions on HVAC filtration for these measures. Moreover, because the removal efficiency for integral measures of PM2.5 and UFP are also a function of particle size distributions that challenge the filter, one has to consider the varied sources of aerosols found indoors and their size distributions. This work has two objectives: (1) to measure the in-situ size-resolved particle removal efficiency of off-the-shelf residential HVAC filters, and (2) to use these size-resolved efficiency data to estimate integral measures of PM2.5 and total UFP removal efficiency for the same filters for typical residential indoor settings based on a survey of indoor particle size distributions. Particle concentration measurements were made upstream and downstream of a wide range of commercial available filters with various minimum efficiency rating values installed in a central air handling unit in an unoccupied residential apartment unit. Next, a literature review was conducted to gather a variety of indoor particle size distributions (PSDs) from across the world and tri-modal lognormal distributions were fit to each of them. Finally, the particle removal efficiency for each filter for integral measures of indoor UFPs and PM2.5 were calculated for each indoor PSD. In-situ size-resolved measurements indicate that filters with similar rating values but from different manufacturers can have very different removal efficiencies for PM2.5 and total UFPs, and that the assumption for indoor PSDs can greatly impact estimates of removal efficiency.