A model with misleading values can easily reach misleading conclusions. If there were any places where the chance of infection reaches even 50% after an hour, t

A model with misleading values can easily reach misleading conclusions. If there were any places where the chance of infection reaches even 50% after an hour, there would be huge, obvious outbreaks associated with people going to those places. The actual observed spread of SARS-CoV-2 has been much slower than this; a basic reproduction number of 7 together with a duration of two weeks means that the average infected person behaving like an average American in 2020 will infect 0.5 persons per day (I'm being generous). This counts situations like e.g. someone becomes infected and goes home to their family and literally lives there. Even in those situations it moves slowly. Or, to put it more on the nose: the half-life for an American getting CoViD under ordinary conditions seems to be longer than a year. Using your linear model, a 50% mask would make it more than two years! So half-life exhaustion doesn't seem an appropriate counterpoint.