Localized and Whole-Room Effects of Portable Air Filtration Units on Aerosol Particle Deposition and Concentration in a Classroom Environment

Meng Kong, Linhao Li, Stephanie M. Eilts, Li Li, Christopher J. Hogan, Zachary C. Pope

Research output: Contribution to journalArticlepeer-review

4 Scopus citations


In indoor environments with limited ventilation, recirculating portable air filtration (PAF) units may reduce COVID-19 infection risk via not only the direct aerosol route (i.e., inhalation) but also via an indirect aerosol route (i.e., contact with the surface where aerosol particles deposited). We systematically investigated the impact of PAF units in a mock classroom, as a supplement to background ventilation, on localized and whole-room surface deposition and particle concentration. Fluorescently tagged particles with a volumetric mean diameter near 2 μm were continuously introduced into the classroom environment via a breathing simulator with a prescribed inhalation-exhalation waveform. Deposition velocities were inferred on >50 horizontal and vertical surfaces throughout the classroom, while aerosol concentrations were spatially monitored via optical particle spectrometry. Results revealed a particle decay rate consistent with expectations based upon the reported clean air delivery rates of the PAF units. Additionally, the PAF units reduced peak concentrations by a factor of around 2.5 compared to the highest concentrations observed and led to a statistically significant reduction in deposition velocities for horizontal surfaces >2.5 m from the aerosol source. Our results not only confirm that PAF units can reduce particle concentrations but also demonstrate that they may lead to reduced particle deposition throughout an indoor environment when properly positioned with respect to the location of the particle source(s) within the room (e.g., where the largest group of students sit) and the predominant air distribution profile of the room.

Original languageEnglish (US)
Pages (from-to)653-669
Number of pages17
JournalACS ES and T Engineering
Issue number4
StatePublished - Apr 8 2022

Bibliographical note

Funding Information:
This study was funded by Delos Living, LLC. However, Delos Living, LLC, had no input on any part of the trial process.

Publisher Copyright:
© 2022 The Authors. Published by American Chemical Society.


  • airborne virus transmission
  • fomite
  • particle deposition
  • portable air filtration unit
  • ventilation

PubMed: MeSH publication types

  • Journal Article


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