The primary way of person-to-person corona virus transmission is via aerosols or small droplets created by breathing, sneezing or coughing.
The reach of exhaled air can be effectively reduced using a face mask as shown in the video.
A simple Schlieren imaging technique is applied to visualize the air flow caused by a person breathing and coughing. Using a face mask the exhaled air flow is blocked reducing effectively the risk of infection. Also nicely shown is the heat transfer from the body to the cooler ambient air.