Corsi Rosenthal boxes

I can’t believe that I didn’t find out about Corsi Rosenthal boxes and other homemade air purifiers until a few months ago.

A Corsi Rosenthal box is a cube consisting of a box fan on one side, a cardboard square on one side, and furnace air filters on the other four sides. The fan draws in air through the filters. Because the smoke, dust, and viruses are stopped by the filters, the fan blows out MUCH cleaner air. There’s a Wikipedia entry on the Corsi Rosenthal box at Corsi–Rosenthal Box - Wikipedia .

I built a mini Corsi Rosenthal box based on a smaller 9-inch box fan and smaller furnace filters. An example is at .

I also built an air purifier that consists of a bathroom fan with a shop vac filter attached to the exhaust. The fan sits on a wooden platform (for stability) and is housed inside a bucket with holes that I drilled into it. It’s loud, but that allows it to double as a white noise generator. I run this air purifier in my bedroom when I sleep. The white noise blocks out the sounds of firecrackers, sirens, and other noises.

There should be a Corsi Rosenthal box or other air purifier in every home, classroom, gym, church, office, etc. These homemade air purifiers offer so much more bang for the buck than commercial air purifiers and are also MUCH cheaper and less intrusive than the expensive renovations often required to improve the ventilation in buildings.


Used one for years in my workshop. Tip: make the box by taping the outside of the two opposing corners, and the inside of the other two opposing corners.

Now you can fold it flat, and put up against wall or under a desk with the fan it takes up less than 6” of room, and it takes two seconds to set up or break down. And you don’t really need to make the mask or go through a lot of other gyrations, it works just fine without.

When I’m going to paint or poly something in the workshop I run it for 24 hours prior to pull the pet hair and dust out of the air so I get a nice even coat.