Influence of Human Activities and Occupancy on Emissions of Indoor Particles and Their Potential Contribution to Fomites
P. S. GANESH SUBRAMANIAN, Joseph V. Puthussery, Yuqing Mao, Thanh H. Nguyen, Ty Newell, Vishal Verma,
University of Illinois Urbana-Champaign Abstract Number: 288
Working Group: Aerosol Science of Infectious Diseases: What We Have Learned and Still Need to Know about Transmission, Prevention, and the One Health Concept
AbstractAirborne transmission is probably one of the dominant factors responsible for the widespread infections of SARS-CoV2. Crowded indoor spaces with inadequate ventilation or filtration are vulnerable and can potentially become an infection hotspot. Identifying the dominant factors that influence indoor particle emissions would help in improving our understanding of airborne transmission of pathogens.
In the current study, particle emission rates (PER) and CO
2 exhalation rates (CER) from different human activities for masked (N-95) and unmasked conditions were determined in a sealed chamber. To relate these results with the real-world human-occupied indoor environments, particle number concentration (PNC) and CO
2 were measured in two different environmental settings - a café and a music club, and the influence of human occupancy and other activities on the PER were assessed.
Results showed that both CER and PER were the highest during exercise. There was no statistically significant difference in CER or PER between reading and idle sitting. Interestingly, masking showed a relatively lower CER, indicating CO
2 retention in the mask dead volume, that could mix with inhaled air and thus could also lower O
2 inhalation efficiency. Only during exercise, PER reduction from masking was observed, indicating that the particle emissions from respiration constitute only a tiny fraction of the total particle emissions from humans. Both PNC and CO
2 showed strong-to-moderate correlation with human occupancy in both the club and café. Splitting the dining hours into breakfast and lunch hours significantly enhanced the correlation of PNC with occupancy, indicating that cooking is the dominant source of particle emissions. Collectively, our results from both clean chamber and crowded indoor environments show that humans and human-related activities (e.g. cooking, resuspension) are the dominant sources of particle emissions and that even in complex settings such as restaurants and clubs, PNC could be used as an indicator of human occupancy. Finally, we used this data to model the contribution of these particles towards the fomite generation. The preliminary results suggest significant contribution of the particles emitted from humans to become fomites at high indoor PNC, by escaping the respiratory deposition from infected individuals.