A Respiratory Simulator for the Study of Pathogen Transmission in Indoor Environments

Detailed investigation of pathogen transmission by respiratory droplets requires extensive experimental datasets with high spatial–temporal resolution in a wide range of ambient conditions. Respiratory simulators are attractive tools for those measurements, because they improve repeatability, endurance, and control of experimental conditions with respect to studies on human subjects. They also enable the use of powerful experimental techniques, which may raise health concerns if employed on humans. In this paper, we design and present a respiratory simulator, which is capable of accurately reproducing physiological flow rate profiles and allows the investigation of the spatial and temporal features of the exhaust flow by background-oriented schlieren (BOS) and particle image velocimetry (PIV). We use laser interferometry and high-magnification shadowgraphy to verify the size distributions of the emitted droplets, and we quantify the evolution of the droplet concentration during cough events by Mie scattering analysis. The experiments demonstrate the ability of the respiratory simulator to generate highly reproducible cough events with precise and controllable droplet size distributions over a wide range of flow rates.