Before revision: Due to the rate at which the COVID-19 pandemic is spreading, a model for indoors airborne transmission that is quick to implement is required. We create such a model assuming that  the concentration of airborne infectious particles is governed by an advection-diffusion-reaction equation .
After revision: Due to the rate at which the COVID-19 , that the concentration of airborne infectious particles is governed by an advection-diffusion-reaction equation .