BREATH MINT TRACER

Several studies suggest that far-field transmission (> 6 ft) explains the significant number of COVID-19 super-spreading outbreaks. Therefore, quantitative evaluation of near- and far-field exposure to emissions from a source is key to better understanding human-to-human airborne infectious disease transmission and associated risks.

In this study, we used an environmentally-controlled chamber to measure volatile organic compounds (VOCs) released from a healthy participant who consumed breath mints, which contained unique tracer compounds. Tracer measurements were made at 2.5 ft, 5 ft, 7.5 ft from the participant, as well as in the exhaust plenum of the chamber.

We observed that 2.5 ft trials had substantially (~36-44%) higher concentrations than other distances during the first 20 minutes of experiments, highlighting the importance of the near-field relative to the far-field before virus-laden respiratory aerosol plumes are continuously mixed into the far-field. However, for the conditions studied, the concentrations of human-sourced tracers after 20 minutes and approaching the end of the 60-minute trials at 2.5 ft, 5 ft, and 7.5 ft were only ~18%, ~11%, and ~7.5% higher than volume-averaged concentrations, respectively.

Our findings highlight the importance of far-field transmission of airborne pathogens including SARS-CoV-2, which need to be considered in public health decision making. 

Additionally, our research shows a novel methodology for studying airborne bioaerosols using VOCs, in this case in breath mints, as proxies for airborne pathogens. This method can be used in future to estimate the benefits of alternate environmental conditions and occupant behaviors.

Read the publication here.