Quantitative filter forensics: Size distribution and particulate matter concentrations in residential buildings

Abstract

We applied filter forensics, the analysis of dust from the heating, ventilation, and airconditioning (HVAC) filters, to measure particle size distribution in 21 residences in Toronto, Canada over a year. Four filters with different nominal efficiencies (Minimum Efficiency Reporting Value (MERV) 8-14 from ASHRAE Standard 52.2) were deployed in each residence each for three months, while the effective filtration volumes (the product of flow rate, runtime, and in-situ filter efficiency) were characterized over each filter lifetime. Using extraction and laser diffraction, we found that approximately 90% of the volumetric distributions were >10 µm and the volume median diameter (VMD) ranged from 23.4 to 75.1 µm. Using quantitative filter forensics (QFF), total suspended particle (TSP) concentrations ranged from 2.9 to 823.7 µg/m 3 (median = 89.8 µg/m 3 ) with a moderate correlation with the content of TSP on the filters (in terms of g) and with the TSP effective filtration volume (m 3 ) indicating the importance of both filter forensics and HVAC metadata parameters to QFF concentration estimates. There was no strong correlation between PM 10 or PM 2.5 concentrations and hourly airborne particle number concentrations measured by low-cost sensors suggesting an evaluation of QFF is warranted, particularly for the exploration of smaller particles.

Particulate matter concentrations in social housing

“…The similar concentrations in the non-smoking apartments and Central Texas SFDs (p = 1) may be explained by higher runtimes and flow rates (see Givehchi et al [72]) and that these were newer homes which may have lower dust levels and be more airtight, all of which contribute to lower TSP measurements. In both comparator datasets, there is additional uncertainty from measuring the change in mass from each filter sample [61]. These results suggest that optical particle counters may be better suited for making direct comparisons between studies as they are less biased by methodology and factors (such as system runtime and flow rate) that cannot be easily controlled.…”

“…One study examined a group of 21 single family dwellings (SFDs) in Toronto measured for a period of one year. These homes were previously described in Zhang et al [60] and Mahdavi and Siegel [61], consisting primarily of detached and semi-detached houses with nonsmoking occupants (smoking evidence was observed in only one home at a very low selfreported frequency). These homes have continuous PM number concentrations measured by Dylos DC1700 as well as TSP measurements measured with differential weighing of filters in the central forced air HVAC systems.…”

“…The TSP concentrations from the Toronto SFDs are included because measurements from the same home are previously shown in Figure 3. However, there are important differences in how these measurements were collected, namely from central-system filters with very low runtimes (see Li et al [84]) and a tendency for the system to operate when occupants were at home and active (Zhang et al [60]), and that these older homes may contain more large dust particles and have higher leakage areas (Mahdavi and Siegel [61]). All of these factors likely contribute to higher TSP measurements in the Toronto SFDs.…”

“…This paper considers PM concentrations in the context of smoking, season, building, and retrofit status with the larger goals of evaluating potential exposure disparities in this study population and assessing the impacts of building retrofits. To examine potential disparities in PM exposure, results are compared with a contemporaneous investigation of PM concentrations in 21 single-family dwellings (SFDs) in Toronto by the same research team using similar methods (previously reported in Zhang et al [60] and Mahdavi and Siegel [61]). To our knowledge, there has not previously been a direct comparison between PM concentrations measured in homes with lower-and higher-SES.…”

Quantitative filter forensics for semivolatile organic compounds in social housing apartments

“…31 Quantitative filter forensics (QFF) has thus been explored to quantitatively characterize time-averaged indoor particle-bound contaminants using the filters collected from building HVAC systems or portable systems. 31,36 This technique has been used to estimate airborne concentrations of particle-bound contaminants, such as PM, 37 the airborne indoor microbiome, 38 and SVOCs 36,39 captured by HVAC filters in indoor environments. However, many post-war MURBs (often constructed between 1960 and 1970 in Canada) are not equipped with forced-air HVAC systems that would allow the use of QFF.…”