The Corsi-Rosenthal Box with Single Filter is a build-it-yourself air purifier and effectively a simplified version of a standard Corsi-Rosenthal Box. As the name implies, it's effectively just a box fan taped to a single MERV 13 furnace filter. As with the full-size design, filtration performance and feature sets can vary depending on what components you use. However, your build will return broadly similar results using high-quality filters and a relatively potent box fan.
Our Verdict
Our single-filter Corsi-Rosenthal Box is middling for pet owners. It has a hard time with the smallest airborne particles, like cat dander, and lacks any odor-absorbing carbon filter layer. It's also very noisy, which isn't great if your pet is particularly sensitive to loud noises.
- Reasonably high clean air delivery rate.
- Noisy operation.
- No smart functionality.
- Poor particle filtration performance.
Our single-filter Corsi-Rosenthal Box is ill-suited to use in bedrooms. It's loud, noisy, and ugly, though it takes up much less room than the full-size four-filter Corsi-Rosenthal Box. Its particle filtration performance also lags far behind that of its larger stablemate.
- Reasonably high clean air delivery rate.
- Noisy operation.
- No smart functionality.
- Poor particle filtration performance.
- Reasonably high clean air delivery rate.
- Noisy operation.
- Poor particle filtration performance.
- Reasonably high clean air delivery rate.
- Noisy operation.
- Poor particle filtration performance.
Performance Usages
Changelog
- Updated Nov 04, 2025: Version 1.0.2 of our Air Purifier Test Bench rectifies calculation errors in our existing Particle Filtration Rate test to provide more representative results of some units. For a more detailed breakdown of the changes made, see our full changelog.
- Updated Oct 31, 2024: Converted to Test Bench 1.0.1.
- Updated May 13, 2024: Review published.
Check Price
Differences Between Sizes And Variants
This is a single-filter iteration of a standard four-filter Corsi-Rosenthal Box, which delivered drastically different overall performance.
Popular Air Purifier Comparisons
Compared to the full-size Corsi-Rosenthal Box, this single-filter alternative is a bit of a letdown. It has a much lower clean air delivery rate and does a far worse job when sealing in fine particles. While it is cheaper than many commercially available air purifiers, there are quite a few reasonably-priced options out there that boast not only superior performance but also a wide variety of smart features, like the Winix C545.
Test Results
The Lasko 20-inch box fan we used for our Corsi-Rosenthal Box has three levels of fan speed adjustment.
Our single-filter Corsi-Rosenthal Box's filter system consists of one 3M Filtrete 20x20x1 MPR 1900 Premium Allergen, Bacteria & Virus Smart Air Filter. This filter has an estimated lifespan of three months when used in a home furnace, air conditioning, or HVAC system; their lifespan in an air purifier will fall within a similar ballpark, depending on how often you run it. You can buy a set of four filters here.
Note that the air purification performance largely depends on where and how you place the unit in a room; we tested it with the filter side facing outwards, but its performance was significantly worse if its filter side was left facing a wall from the normal testing distance of 1".