The Corsi-Rosenthal Box: DIY Box Fan Air Filter for COVID-19 and Wildfire Smoke
The Corsi-Rosenthal Box is a homemade air cleaning system that can reduce indoor exposure to airborne particles that contain the virus that causes COVID-19. It can also reduce the levels of other particles in the air, such as dust or wildfire smoke. These filters are being used in homes and schools, and can be an affordable temporary solution for a variety of agricultural settings, including office spaces and break rooms.* While they are not HEPA air cleaners, recent testing at UC Davis and elsewhere has shown that the box can be more effective than HEPA air cleaners.
The Corsi-Rosenthal Box is made of a simple box fan, which should be oriented upward so that it is blowing air toward the ceiling. The fan is connected to a “box,” which is made of four MERV-13 filters and a cardboard base attached with duct tape.
How long can the Corsi-Rosenthal Box be used?
The lifetime depends on how long it is used each day and how dusty the environment is where it is placed. A Corsi-Rosenthal Box used several hours per day will last longer than one running continuously.
In many cases, a system operating on low for a portion of a day may last as long as 5 to 6 months. If operated on higher flows and longer durations in a dusty location, the system might only last a month or two.
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- How to make a 4-filter DIY Air Purifier with a round fan (English)
- Corsi-Rosenthal Box User Guide (English and Spanish)
- UC Davis Engineering Students Compete to Build Corsi-Rosenthal Air Purifiers
- Construction Guide
- More information
* 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 mask, particularly N95 and KN95, is the most effective way to protect your respiratory system.