What can you build with duct tape, air filters, and a box fan?

This might sound like the set up for a dad joke, but according to new insights from 3M, the answer is less of a punchline and more a breath of fresh air: Corsi-Rosenthal boxes.

What is a Corsi-Rosenthal box?

The box is a do-it-yourself air filtration device that is an alternative to traditional air purifiers on the market. It was popularized by an indoor air quality researcher and an air filtration expert in the summer of 2020 and designed to help reduce the number of virus-laden aerosol particles in indoor settings.

The design is straightforward. You need one box fan, four high-quality air filters, duct tape and some cut-out cardboard. Most boxes can be constructed in less than 45 minutes with materials costing about $80 to $100.

But does it work?

The short answer is yes.

When 3M first noticed the DIY trend on Twitter, Filtrete™ Brand filtration experts started building and testing multiple versions of the box. DIYers were using 3M Filtrete™ Air Filters, so the lab experts did, too. They concluded the boxes were effective at capturing unwanted airborne particles, including viruses, (link to results) and serves as a good supplement to a more holistic ventilation strategy.

“Indoor air is shared air,” said Kelsey Hei, a 3M Filtrete Brand engineer. “Many viruses like COVID-19 are airborne and can become highly concentrated in poorly ventilated spaces. I’m heartened to see so many people advocating for the importance of clean air, especially in schools.”

Why does it matter?

Teachers, parents and everyday citizens have been building Corsi-Rosenthal boxes for schools, day care centers, senior living facilities and many other shared indoor spaces.

The movement has stretched across the globe and is gaining traction with public health officials in the U.S.

The California Department of Public Health recently listed the Corsi-Rosenthal box on their webpage about COVID-19 and Improving Indoor Air Quality in Schools.

Co-collaborators on the box, Jim Rosenthal, and Dr. Richard Corsi, encourage all to participate and to put their own artistic spin on the design.

Richard is the dean of Engineering at the University of California, Davis, and a longtime indoor air quality researcher.

“Designing the Corsi-Rosenthal box has been one of the most gratifying things that I have done in my career as an engineer,” he said. "I am thrilled to be part of something that is so accessible to people around the world, helping to protect children in school and families in their homes, all the while inspiring children about the power of STEM.”

Jim is pleased to see the concept take off as well. His Twitter feed is full of people sharing their unique designs.  

“My wife wonders why I’m spending so much time on Twitter,” he said. “I consider myself a cheerleader at this point. The movement has taken on a life of its own and that’s good news for the air we breathe.”

It appears indoor air quality is having a moment.

And that’s no joke.