Performance and Practical Considerations of Deploying Do-It-Yourself (DIY) Air Purifiers in Occupied Classrooms

Abstract

Poor classroom ventilation allows airborne particles to build up, leading to suboptimal indoor air quality (IAQ) and increased risk of airborne viral transmission. While commercial portable air cleaners are effective, their high price and maintenance costs often limit widespread deployment. This study evaluates the real-world performance of Corsi-Rosenthal (C-R) Boxes, a low-cost, DIY air cleaner, within occupied university classrooms without central ventilation, while also considering practical aspects such as noise levels, fire safety, and air movement. We utilized a within-session pre-post design to control for variables such as occupancy and outdoor conditions. By establishing baseline PM1, PM2.5, and PM10 mass and particle number concentrations at the start of class before automatically activating the C-R Boxes, each session served as its own control. Across 59 class sessions, the C-R Boxes reduced PM2.5 mass concentrations by an average of 61% [IQR 48%–80.5%]. Multipoint sensor monitoring confirmed that the C-R Boxes provide air mixing. The C-R Boxes maintained an acceptable noise level (52 dBA at 2 m) and presented no elevated fire safety risks even in high-temperature conditions (30 °C/86 °F). These findings demonstrate that C-R Boxes are a safe, effective, and scalable solution for improving classroom IAQ without degrading the learning environment.