This fall, teachers and parents have been sharing photos on social media of do-it-yourself air purifiers that they’ve made for classrooms to help protect kids from COVID-19 transmission.

But do these low-cost purifiers actually work?

According to researchers, they do.

They’re called Corsi-Rosenthal Boxes, a DIY air purifier that was first conceived of in the summer of 2020 by two air filtration experts, Richard Corsi and Jim Rosenthal.