Effects of Portable Air Filtration Units on Submicrometer- and Micrometer-Sized Aerosol Particle Deposition and Concentration in a Natural Ventilated Skilled Nursing Facility
LINHAO LI, Zachary Pope, Youngjoo Son, Stephanie Eilts, Christopher J. Hogan, Meng Kong,
Well Living Lab Abstract Number: 81
Working Group: Aerosol Science of Infectious Diseases: Lessons and Open Questions on Models, Transmission and Mitigation
AbstractOlder adults are the most vulnerable population to respiratory diseases (e.g., COVID-19, influenza). Identifying effective engineering controls is critical to reduce transmission risk via airborne particles, particularly in spaces where older adults reside (e.g., skilled nursing facilities; SNF). We therefore systematically investigated how recirculating portable air filtration (PAF) units, a common engineering control, and natural ventilation influenced airborne particle travel via the direct aerosol route (i.e., representing airborne transmission) and the indirect aerosol route (i.e., representing fomite transmission). A breathing simulator was built and used to atomize fluorescein-tagged submicrometer- (0.6-0.7 µm) and micrometer-sized (2 µm) particles simultaneously utilizing a physiologically correct inhalation-exhalation waveform, with the breathing simulator outlet connected to an anatomically correct respiratory manikin. Experiments were conducted in two SNF resident rooms, referred to as the ‘infector’ and the ‘susceptible’ rooms, with the former room containing the breathing simulator (i.e., proxy infected resident) and the latter room representing a susceptible resident’s room. Observations revealed that despite PAF units enhancing deposition velocities for submicrometer- and micrometer-sized particles, effective deposition fluxes of submicrometer-sized particles were significantly lower during PAF use compared with the Baseline Condition. Further, PAF units increased the effective air exchange rate by ~3.7 and 4.5 times for submicrometer- and micrometer-sized particles, respectively, resulting in significantly lower particle concentrations (>60%) for these particle sizes versus the Baseline Condition. While natural ventilation significantly reduced submicrometer- and micrometer-sized particle concentration and deposition, evidence of cross-contamination between rooms was identified when natural ventilation was used as the singular ventilation solution. Taken together, observations validated our previous studies in that particle deposition is not negligible in smaller rooms with poor ventilation and that PAF units are recommended as a supplement to natural ventilation to best limit airborne particle concentration, and later particle deposition, in such indoor spaces.