Influence of Human Activities and Occupancy on the Emission of Indoor Particles from Respiratory and Non-respiratory Sources
P. S. GANESH SUBRAMANIAN, Joseph V. Puthussery, Yuqing Mao, Sudheer Salana, Thanh H. Nguyen, Ty Newell, Vishal Verma, University of Illinois Urbana-Champaign
Abstract Number: 160
Working Group: Indoor Aerosols
Abstract
Airborne transmission is an important pathway leading to the spread of infectious diseases, particularly in indoor settings. In this study, we examined the relationship between human activities and emission characteristics of CO2 and particles (0.3 – 10 μm) in a clean-environmental chamber, a café, and a music club. We measured the CO2 and particle emission rates (CER and PER) across three human activities, in masked (N-95) vs. unmasked scenarios, as well as normal vs. cleanroom clothing (CRC) scenarios in a chamber to estimate the relative contribution of respiratory and non-respiratory aerosol emissions from humans. Particle number concentration (PNC) and CO2 were measured alongside human occupancy in two real-world environments (i.e., café and club) to quantify the dependence of CO2 and PNC on human occupancy. Results from the unmasked experiments revealed that both CER and PER were highest during exercise activity, but the difference in CER or PER between passive activities (sitting vs. reading aloud) was not statistically significant. Masking led to significant reduction (~ 10%, p<0.05) in CER across all activities, but led to a reduction in PER only during exercise (~ 11%, p<0.05), indicating that respiratory sources constitute a tiny fraction of the total particle emissions during passive activities. However, donning CRC reduced the PER by over 55% for all activities, demonstrating that clothing and skin-shedding constitute a dominant fraction of particle emissions from humans. Results from the real-world environments revealed that both CO2 and PNC were mostly driven by human occupancy (R > 0.60, p<0.05), albeit with effect modifiers such as filtration, cooking activities, etc. Collectively, these results demonstrate that non-respiratory emissions (e.g., clothing and skin-shedding) from humans outnumber respiratory emissions in indoor environments, emphasizing the need to better quantify the contribution and evaluate the potential role of non-respiratory emissions from humans in the airborne transmission of infectious diseases.