Development of sampling system for particles in a human respiratory emission maximizing signal and minimizing background

Abstract

The recent COVID-19 (SARS-CoV-2) pandemic of and the devastation that it brought have led toa renewed interest in better understanding human respiratory emissions. The public health challenges that it brought exposed gaps in our understanding in this field that is so-ever consequential in mitigating the spread of infection diseases. This study tackles one of the main challenges we face in studying human respiratory emission particles: low signal to noise ratios. In other words, this study presents the development of a novel system to lower background particles while simultaneously enhancing the signal from respiratory emissions. The system consists of three main components: a modified ASHRAE 52.2 wind tunnel, a breathing cone and a 38-nozzle virtual impactor. Calibration of the system was initially carried out with just the equipment and a manikin and subsequently measurements of respiratory emission from human subjects were made. More specifically, the respiratory activities examined in this study were breathing, talking, and coughing. The impact of filtering face piece respirators (FFRs), an N95 mask in particular, on the respiratory emissions was a secondary goal of the study. Size distribution and concertation levels of the signal are reported and analyzed for each activity. Penetration levels as function of the outward leakage when the respirator is worn is also presented. Improved signal to noise ratios as well as elevated concentration of the respiratory emissions were accomplished. While the size distributions show good agreement with prior literature, concentration levels demonstrate significant improvement of the signal levels in comparison to some of the previous similar works. This study also reinforces the use respirators to control or mitigate the spread of infectious diseases. Overall, the result of this study represent new possibilities when it comes to the application of virtual impactors but also additional methods for characterizing human respiratory particles.