Those of you looking for a post-Holiday palate cleanser will appreciate this DIY Geek post – here’s how you can build your own Corsi–Rosenthal Box! Now that winter is upon us, we’re stuck inside for the next few months breathing all that built up dust and whatever viruses and bacteria your antivax uncle brought to the party. Who needs that, right?
This is a nice way for me to forget the cold and rain outside, while giving myself a better air purifier than one of those expensive HEPA filters. A Corsi–Rosenthal Box or Cube is a simple, inexpensive DIY air purifier. It was designed during the COVID-19 pandemic with the goal of reducing the levels of airborne viral particles in indoor settings.
This how-to comes from UC Davis (Link) but I’ve distilled the instructions down to something easier to read for you:
Step One – Get your materials.
- Four (4) MERV 13 filters ($20-40 each)
- One (4) box fan ($20-40 each – you can often pick these up for free on Craigslist)
- One (1) roll of duct tape
Step 2: Build the Basic Structure
Using your duct tape, build a box out of the four filters as shown in the picture above. All four come together, connected by the tape to form the basic structure and the box fan will go on top of that when you’re finished.
Now, it’s important to remember: air filters are designed to flow ONE WAY. They have arrows on the side to show you which direction the air is supposed to flow in:
So make sure you build the box with the arrows on the filter flowing into the center. Otherwise, the filters won’t work correctly. Once you’ve done that, go back over all the edges of your structure – make sure every seam is air-tight with duct-tape.
Step Three: Finalize your Corsi–Rosenthal Box
You can put the box on the floor directly, or use cardboard as shown in the picture above. Triple-check all your side edges to make sure that the structure is allowing no air through the seams between MERV filters. Don’t worry about taping anything on the bottom. You might get a little air flowing through the bottom, but that’s ok.
Step Four: Seal the Box Fan on Top
Now we put the box fan on top and make sure it’s air-tight with the rest of the structure. You can use cardboard, duct tape, or plastic wrap if you have some to seal off the edges between the box fan and the rest of the Corsi–Rosenthal Box. This is where you’ll channel your Inner MacGyver to really make sure all edges are sealed. Test the box fan by turning it on and seeing if air pulls in from any place it shouldn’t, and seal that spot with more duct tape.
Step Five: Profit
Once you’re done, step back and watch your Corsi–Rosenthal Box fly! It’s a simple, DIY geek project that you can build with kids if you need something to keep them busy. Plus, once it’s finished you’ve got a neat little science project you can show off to others. Best yet – your air will be cleaner and you’ll save money. You’re a technical, financial genius!
In many cases, a Corsi–Rosenthal Box operating on low for a portion of a day may last as long as 5 to 6 months. Don’t forget – this isn’t a substitute for masking up! ‘If operated on higher flows and longer durations in a dusty location, the system might only last a month or two. The Corsi-Rosenthal box is not a substitute for high-quality masks. Use of this, or any other air cleaner should be a supplement not a substitute for wearing a mask. Use of a high-quality masks, particularly N95 and KN95, is the most effective way to protect your respiratory system.’
Hope you enjoyed this DIY Geek article on how to build your own Corsi–Rosenthal Box air filter. Clean air is better for you – now you can breathe easier, knowing your Corsi–Rosenthal Box is on the job.