I’m so excited to share with you a super simple and inexpensive DIY air purifier. It only took 5 minutes to assemble this homemade air unit and I’m astonished at how well it has improved the air.
Here in the Pacific NW we currently have the worst air quality in the world from all the wildfires and living only a few miles from the Nakia Creek fire outside Camas Wa the air is been hazardous. I assembled this a few days ago as we were starting to feel ill from the choking smoke. I promise you… this homemade air purifier ROCKS!
This DIY air filter utilizes an ingenious cube design that increases the filtration media surface area so much that it’s MORE EFFECTIVE than a good HEPA system at a fraction of the price. You can have the satisfaction of creating it yourself. How awesome is that?
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Here’s what you’ll need to build your own DIY Box Fan Filter AKA (Corsi Rosenthal Box).
All you need:
4 furnace Filters MERV 13 or higher
Scissors or a box cutter
Optional: Cut a cardboard sheet the size of the cube. I cut mine from the box the fan came in. Perfect size! You can also go to any grocery store and find a box to cut up.
Note: It works fine without the cardboard cutout, so don’t let it stop you from building it. You can always add the cardboard later, or you could increase efficiency even more by using a 5th furnace filter in place of the cardboard. In that case you would need to place the cube on something to allow airflow from below and you would need to purchase an extra filter. The benefit of using the extra filter on bottom is to decrease the air resistance thus extending the lifespan of the fan and extra media surface area to filter. I built mine with just 4 filters and it works really well without the added expense.
5 Minute assembly:
Step 1. Arrange a 4-sided Cube with the filters. (Be sure the arrows on the filters are pointing INWARD, You’ll see it on the filter) Offset them to make a perfect cube. Use duct tape to hold together…making sure all seams are sealed.
Step 2. Cut cardboard to the size of the cube to make a bottom or optionally you can use a 5th filter (See optional note above) Either way the most important thing is making sure to seal all seams using duct tape.
Step 3. Place Box Fan on top of the square so that the air blows upward. Which sucks the air through the filters and blows clean air outward to you. Attach fan using duct tape, being sure to seal any air gaps.
Tips:
Be sure to seal all seams. You want airflow blowing out and up, or optionally you could place the fan on 1 side blowing sideways.
To make a perfect cube, offset/ stagger all 4 corners before taping them.
Don’t worry … duct tape makes anyone look like a pro and could seal all mistakes. Our 2nd cube was a bit wonky. Duct tape to the rescue.
Easy Peasy … Done! Turn on the fan and grab your family to admire your ingenuity!
How long will the filters last?
They are supposed to last 6 months under normal conditions without decreased filtration. As I mentioned, we have VERY DENSE wildfire smoke. Here are some pics.
The 1st one is when we built the unit. The 2nd one is 2 days later. Notice the filters are turning brown! I’m grateful the dangerous particles are in the filters rather than in our lungs!
Try out this easy, effective and inexpensive solution to help clear indoor air from virus particles, wildfire smoke, pollutants, pollen, dust and more. This Box Fan Filter design could be a wonderful solution for small businesses, classrooms, checkout stands, restaurants, storefronts and more. It provides an added layer of protection from viruses, Covid, RSV, the flu, smoke, odors and indoor air pollution.
This is so easy. Give it a whirl. You may have all the things you need. I always encourage buying local, but with the entire west coast dealing with wildfire smoke… so some things may not be available in your area. I’ve provided some links below that may help you.
Box fan 20″
Filter 20″ (need 4 20″x20″)
Duct tape (1 roll)