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  • Writer's pictureFTFO

Clean Indoor Air During Wildfire Smoke


photo Samantha Harrington January 16, 2023

It's easy to make your own filter which has a clean air delivery rate between 600 and 850 cubic feet per minute (depending on fan speed) according to a 2022 study.

Yale Climate Connections has specific instructions with clear photos on creating a homemade filter, known as a Corsi-Rosenthal box:

Start with a base — preferably a new 20-inch box fan — and be sure to save the cardboard box it comes in!

Get four cheap 20-by-20-inch filters to attach to the fan’s sides.

Tape the filters together to form a cube, making sure the corners are fully covered so air is forced through.

Cut out one side of the box that the fan came in and tape it to the bottom of your cube.

Place the box fan at the top of the cube so air is blowing upward. Again, seal those corners with tape! And there you have it — your own homemade air filter.

Science behind the box fan:

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