Also known as a Corsi-Rosenthal box, this DIY method of building your own air filter with MERV13 furnace filters and a box fan are an easy and cost-effective way to help clear indoor air from airborne virus particles, wildfire smoke, pollen, dust, and more!
If you can seal a box, you can build one (or 100!) of these!
Table of Contents
Image / Video Gallery
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Video: How to effectively ventilate classrooms using fans, HEPA filters or Corsi-Rosenthal box fans and monitors
Cleaning indoor air properly greatly reduces infections by airborne viruses, like COVID-19. This video explains it all very well!
How to build a Corsi-Rosenthal box fan filter
A Variation on the “Box Fan with MERV 13 Filter” Air Cleaner Article by Jim Rosenthal
Read about it in WIRED: https://www.wired.com/story/could-a-janky-jury-rigged-air-purifier-help-fight-covid-19/
The Fan Shroud
An optional part of a box fan filter is the fan shroud, or covered fan corners. Covering corners of a square box fan closes gaps and improves efficiency of the fan. See Jim Rosenthal’s article about it here. Use cardboard or duct tape.
David Elfstrom advises “keep an eye out for local sales on the 20x20x1 or 20x25x1 Filtrete 1900 and box fans”
You can order a full set of high-quality MERV13 filters to make this air purifier here: https://www.texairfilters.com/filters-for-box-fan-and-merv-13-filters-air-cleaner
These 2 inch deep filters (compared to typical 1 inch) provide greater surface area for filtration, better air flow, quieter operation, and longer filter life.
(hint: Filterbuy MERV-13, prevalent on Amazon, have not tested well- two people have independently compared with particle counters and come to the same conclusion about sub standard performance)
The Corsi-Rosenthal box (single filter tested, full cube would be even better!) performs very well! It is the most cost effective air cleaner on Marwa Zaatari’s chart!
FAQ – Frequently Asked Questions
Video: Box Fan Filter build tutorial – Spanish
Video: A Fourth Grader Explains How to Build a DIY Corsi/Rosenthal Box Air Cleaner
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