HVAC filtration of particles and trace metals: Airborne measurements and the evaluation of quantitative filter forensics

Alireza Mahdavi; Justin Dingle; Arthur W H Chan; Jeffrey A Siegel

doi:10.1016/j.envpol.2020.116388

HVAC filtration of particles and trace metals: Airborne measurements and the evaluation of quantitative filter forensics

Environ Pollut. 2021 Feb 15:271:116388. doi: 10.1016/j.envpol.2020.116388. Epub 2020 Dec 24.

Authors

Alireza Mahdavi¹, Justin Dingle², Arthur W H Chan², Jeffrey A Siegel³

Affiliations

¹ Department of Civil and Mineral Engineering, University of Toronto, Toronto, Canada.
² Department of Chemical Engineering and Applied Chemistry, University of Toronto, Toronto, Canada.
³ Department of Civil and Mineral Engineering, University of Toronto, Toronto, Canada; Dalla Lana School of Public Health, University of Toronto, Toronto, Canada. Electronic address: jeffrey.siegel@utoronto.ca.

PMID: 33388682
DOI: 10.1016/j.envpol.2020.116388

Abstract

Filters installed in the heating, ventilation, and air-conditioning (HVAC) systems can serve as air-cleaning and sampling devices for indoor particles. The purpose of this article is to evaluate these dual roles. An occupied home with a central HVAC system equipped with a Minimum Efficiency Reporting Value (MERV, from ASHRAE Standard 52.2) 11 filter was monitored for six weeks. Weekly airborne gravimetric and real-time sampling was performed to measure the particle size distribution and the concentration of total suspended particles (TSP), PM₁₀, PM_2.5, PM₁, and 12 trace metals. The weekly system runtimes were intentionally changed to provide a wide range of weekly filtration volumes. The quantitative filter forensics (QFF) concentrations of particulate matter (PM) and trace metals were calculated using the analysis of the dust collected on the HVAC filter, the filtration volume, and filter in-situ efficiency. The results indicated that filtration was not influential to remove PM and trace metals as the concentrations during the weeks with continuous HVAC operation were not consistently lower than those during the other weeks. This suggests the dominance of other particle and trace metal source and loss mechanisms weakens the influence of filtration in this home. The QFF evaluation results indicated that the concentration of TSP and over half of the tested trace metals (e.g., Pb, Cd, Ni, V, Sb, K, and Sr) could be estimated by QFF within a factor of two when compared to airborne sampling results. PM₁₀, PM_2.5, and PM₁ concentrations were significantly underestimated by QFF potentially due to the limitations of size distribution analysis by a laser diffraction particle sizer (LDPS) for the detection of <1 μm particles. Overall, while QFF was promising for TSP and some trace metals, improvement in size distribution analysis could extend the application of QFF for airborne sampling.

Keywords: Airborne sampling; Dust composition; Filter; Particulate matter; Size distribution.

MeSH terms

Air Conditioning
Air Pollutants* / analysis
Air Pollution, Indoor* / analysis
Environmental Monitoring
Filtration
Heating
Particle Size
Particulate Matter / analysis
Ventilation

Substances

Air Pollutants
Particulate Matter