This analysis has some of the best illustrations I have seen, using a living room, a bar, and a classroom.
One time examples, such as the church choir in Seattle or infections in bars, are useful. But we are a visual species. Illustrations and animations can help understand what is happening.
Spanish paper El Pais ran various simulations using the Covid Airborne Transmission Estimator developed by scientists from the University of Colorado. Excellent Illustrations of Covid spreading indoors.
A few excerpts:
Irrespective of whether safe distances are maintained, if the six people spend four hours together talking loudly, without wearing a face mask in a room with no ventilation, five will become infected, according to the scientific model explained in the methodology.
The infection risk drops to below one when the group uses face masks, shortens the length of the gathering by half, and ventilates the space used.
If two hours are spent in the classroom with an infected teacher and 20 students, without taking any measures to counter the number of aerosols, there is the risk that up to 12 students could become infected.
To watch the Excellent Illustrations of Covid spreading indoors, translated into English, click here.