Older adults are highly vulnerable to respiratory diseases. Effective engineering controls are critical to reduce transmission risk via airborne particles, particularly in spaces where older adults reside (e.g., skilled nursing facilities; SNF). We thus investigated how recirculating portable air filtration (PAF) units and natural ventilation influenced airborne particle travel via the direct aerosol (i.e., representing airborne transmission) and indirect aerosol (i.e., representing fomite transmission) routes. A breathing simulator atomized 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 involved two SNF resident rooms, the ‘infector’ and ‘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 versus the Baseline Condition. Further, PAF units increased the effective air exchange rate by ∼3.7–4.5x 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, cross contamination between rooms was identified when natural ventilation was the singular ventilation solution. Observations validated our previous studies in that particle deposition is non-negligible in smaller rooms with poor ventilation and that PAF units are recommended to supplement natural ventilation and best limit airborne particle concentration and deposition.
Bibliographical noteFunding Information:
The authors declare the following financial interests/personal relationships which may be considered as potential competing interests:Meng Kong reports financial support was provided by Delos Living LLC. Linhao Li reports financial support was provided by Delos Living LLC. Zachary C. Pope reports financial support was provided by Delos Living LLC. Youngjoo Son reports financial support was provided by Delos Living LLC. Meng Kong reports financial support was provided by Sabra Health Care REIT. Linhao Li reports financial support was provided by Sabra Health Care REIT. Zachary C. Pope reports financial support was provided by Sabra Health Care REIT. Youngjoo Son reports financial support was provided by Sabra Health Care REIT.We wish to thank William Clark from Mayo Clinic Respiratory Care for allowing use of the respiratory manikin as well as Eric Heins, Well Living Lab Director of Building Operations, Murray Finger, Rochester East Health Services Executive Director, and Steven Lyman, Rochester East Health Services Maintenance Director for assisting with continued operational support for these experiments. This specific study was funded by Delos Living LLC and Sabra Health Care REIT, as one of the Well Living Lab's Alliance members. Neither Delos Living LLC nor Sabra Health Care REIT had input on the study design, data collection, data analysis, or publication of this study.
© 2023 The Authors
- Airborne virus transmission
- Indoor air
- Particle deposition
- Portable air filtration