Abstract View
In-Vitro Investigation of Exhaled Particle Deposition and Ventilation in Office Settings
STEPHANIE EILTS, Linhao Li, Zachary Pope, Christopher J. Hogan, University of Minnesota
Abstract Number: 19
Working Group: Infectious Aerosols in the Age of COVID-19
Abstract
Exhalation of infectious micrometer-sized particles has been strongly implicated in the spread of respiratory infections. An important fundamental question is then the fate of infectious exhaled particles in indoor environments, i.e., whether particles will deposit, and if so, on what surfaces, or whether they will remain suspended in an aerosol until ventilation leads to clearance. We investigated the interplay between particle deposition and ventilation using model experiments with a breathing simulator manikin in a model office environment. The breathing simulator utilized anatomically correct exhalation and inhalation breathing waveforms as well as an anatomically correct manikin to simulate human breathing. The breathing simulator output a fluorescein tagged particles with a mass distribution spanning the 1-3 um range. The test office module was a 19.2 m x 6.9m x 2.6 m room that consisted of three rows of desks with nine manikin occupants (including the simulator). Particle dispersion throughout the office space was tracked by measuring the deposition flux on passive substrates placed in several locations throughout the room, both on horizontal and vertical surfaces. Aerosol mass concentrations were determined using impingers, and surface-specific deposition velocity was then calculated for each passive substrate using deposition flux mass concentration measurements. Four different test conditions were created by changing the simulator location with respect to the return grilles and diffusers in the room as well as through the use of different air change rates and MERV ratings of filters. Deposition measurements under all test conditions revealed enhanced deposition onto horizontal upward faces surfaces, surfaces within 2 m of the breathing simulator, and on non-passive surfaces near return grilles. However, with the exception of surfaces close to the simulator and non-passive return grille exteriors, we found that particles are more likely to remain suspended in the air until removal by ventilation, as opposed to depositing within the office space.