A pump configured to pump an air sample into a cooling chamber;

a cooling chamber configured to cool the exhaled air sample to a sub-zero temperature;

an inert gas source configured to provide inert gas at a pressure higher than atmospheric pressure;

an injector unit in fluid communication with the cooling chamber and the inert gas source, the injector unit configured to mix the cooled exhaled air and an inert gas provided from the inert gas source; and

a testing chamber configured to analyze the mixed inert gas and cooled exhaled air,

wherein the injector unit is configured to inject the mixed cooled exhaled air and inert gas mixture into the testing chamber at a high velocity to increase the aerodynamic length and the average droplet size in the cooled exhaled air and inert gas mixture.