Richard L. Corsi, dean of the UC Davis College of Engineering, explains how to build a Corsi-Rosenthal box. Dr. Corsi is an internationally recognized expert in the field of indoor air quality, with a specific interest in physical and chemical interactions between pollutants and indoor materials. His concept for a low-cost, accessible, and effective air cleaner, the Corsi-Rosenthal box, is now being used as an open-source do-it-yourself approach worldwide for reducing exposure to the SARS-CoV-2 virus, wildfire smoke and more.