Can air purifiers be made from just a fan, furnace filters, and duct tape? Introducing the Corsi-Rosenthal Box (CR Box) DIY air purifier. This is an effective, budget-friendly air purifier that you can put together with low cost.
At Smart Air, we’ve been creating, testing, and instructing people on DIY air purifiers for a long time. However, similar to the original Smart Air DIY purifier, the Corsi-Rosenthal box has its advantages and disadvantages. In this article, we’ll discuss four key points about the CR Box.
1. The Corsi Rosenthal Box is a Powerful Air Purifier, with High CADR and Low Upfront Costs
Tests show a $75 Corsi-Rosenthal box can achieve a clean air delivery rate (CADR) of around 165-239 CFM. In some cases, tests have even shown a DIY CR box reaching a CADR of 850 CFM. This makes the CR box air purifier one of the most economical options available in the market.
2. The Corsi Rosenthal Box is Less Efficient at Removing Virus Droplets from the Air
One drawback is that CR boxes use MERV 13 filters, which trap a smaller percentage of virus-sized particles in one go compared to HEPA filters. MERV 13 filters catch roughly 85% of COVID-19 droplets, whereas HEPA filters often capture over 99.95%. Nevertheless, because the CR box circulates so much air, it manages to trap a significant number of these particles on subsequent passes. This clarifies how it outperformed IQAir, which had filters with much higher ratings, in a direct comparison test.
3. Possible Higher Running Costs
One of the primary reasons people turn to the Corsi-Rosenthal Box is the low up-front cost. In almost all cases, they are cheaper than buying an off-the-shelf air purifier that is equally strong. In fact, Smart Air designed its own DIY air purifiers back in 2013 for the exact same reason.
However, the UC Davis estimate of the CR Box energy efficiency of 2.17-2.19 CADR/watt ranks last compared to 23 popular air purifiers. Results vary significantly between studies though, with one study showing significantly better efficiency. Using a more efficient box fan may help lower energy costs. Energy usage of an air purifier is an important factor that should be considered when calculating the cost of operating an air purifier.
Read More: The Hidden Cost of Air Purifiers
Open Data: Long-term cost analysis data for the Corsi-Rosenthal Box
4. The Corsi-Rosenthal Box may be too Noisy
Tests showed the Corsi-Rosenthal Box can be noisy–with some models reaching 67 decibels on the high setting. Any level of noise over 60 decibels is likely too noisy for most settings, such as schools and offices. Classrooms tend to be around 45-50 decibels, so 60 decibels would overpower a class. Running the CR Box at lower speeds will lower noise but also reduce the amount of air it cleans. Big fans and large HEPA filters are what can keep purifier noise down, like those in the Blast air purifiers Smart Air has designed.
Bottom Line: Pros and Cons of the Corsi-Rosenthal Box DIY Air Purifier
Pros:
* Lower upfront costs
* High cost-effectiveness ratio
* Fun, science-backed DIY project for school kids
Cons:
* Can be noisy on high
* Low small-particle filtration efficiency rates (when using MERV)
* Energy costs may be higher compared to some air purifiers on market
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