PROFESSOR: So having established the importance
of airborne transmission in the spreading of COVID-19
specifically, and more generally in the spreading
of respiratory pathogens, let's proceed
to analyze airborne transmission in a well-mixed room.
So we're thinking of a situation where
a certain number of people are sharing an indoor space.
And the air in that room is well-mixed enough
that as pathogen-containing droplets are released
from the breath of one person, it's quickly spread
throughout the whole room.
And by the time someone else breathes it,
they're essentially exposed to the average concentration of
pathogen in the air after accounting
for such effects as the settling, the evaporation,
the ventilation, filtration, and other effects,
but still at the level of a well-mixed space.