Particle Concentration in Exhaled Breath

Submicron droplet formation in the human lung

“…For smooth breathing patterns, the first mechanism can be excluded due to absence of sufficient shear forces. The newest results of Johnson and Morawska (2009) and earlier investigations of Gebhart, Anselm, Heyder, and Stahlhofen (1988) confirm these conclusions suggesting the reopening of collapsed terminal airway structures as the mechanism of aerosol generation.…”

“…Several studies are found in the literature dealing with the characterization of number and size of exhaled particles (Fairchild & Stamper, 1987;Papineni & Rosenthal, 1997). Morawska et al (2009) provide a broad overview of possible particle sources resulting from normal breathing, speaking, and coughing.…”

Size distribution of exhaled particles in the range from 0.01 to 2.0μm

“…It has been known for a considerable time that aerosol particles are generated in the human airways and that they may leave the body by exhalation (Almstrand et al, 2009;Fairchild & Stampfer, 1987;Papineni & Rosenthal, 1996). This is true not only when coughing, laughing or speaking but also for tidal breathing and when performing various other breathing manoeuvres.…”

Why inhaling salt water changes what we exhale

“…Studies have shown that humans and animals tend to exhale small bioaerosol droplets formed of airway lining fluid, or ALF, owing to the passage of air over the ALF during normal breathing [1][2][3]. Recent work suggests that humans breath out highly varying numbers of such expired bioaerosol particles, with certain individuals breathing out far more particles than others [4].…”