Fig. 1

The Expiratory Droplet Investigation System setup used by Morawska et al. [21]. Test participants exhaled into a particle- free wind tunnel. A fan maintained at approximately 0.1 m/s controls the wind tunnel airflow. The airflow transports exhaled particles downstream to the aerodynamic particle sizer (APS) where the particles are measured. A relative humidity (RH) probe monitors the humidity. Reprinted from the original article by permission