The first Corsi-Rosenthal Box was built in August of 2020. It was presented as an “open source” concept so that as many people as possible could have low-cost cleaner, safer indoor air. It is based on sound engineering principles, but it is really very simple. Use 4 (or 5) MERV 13 filters in a “box” configuration with a box fan. The best thing is – it works! Consequently, many thousands have been made all over the world.
It has also been very enjoyable to see the continuous stream of ingenuity, creativity, and knowledge that has been expended to create a “better” Corsi-Rosenthal Box. Much of this was out of necessity since many countries in the world do not have the same filters and fans as we have in North America. Many really smart and creative people have developed designs of the CR Box concept that work with the fans and filters available in their countries.
We have also had many people in North America who have contributed to the development of a “better mousetrap” of a DIY air cleaner. For effectiveness and low cost, it is very hard to beat the original box fan and “box” of filters design. But there have been many interesting modifications that have been shown to provide some real benefits. The most interesting of these is the use of PC fans to replace the box fan. The PC fans have the advantages of low noise and low energy usage but are not as economical or as easy to construct.
Here is another alternative – modular PC fan systems. A company by the name of AC Infinity (www.acinfinity.com) makes them. Their primary uses are for audio-visual cabinets and indoor horticulture. However, they provide low noise, high air flow and low power usage. In other words, they should work for Corsi-Rosenthal boxes. My initial tests confirm this conclusion.
Here are more details on the “Modular PC Fan CR Box” build – with pictures.
The 16X20X2 MERV 13 filters and modular PC fan systems fit together nicely. No modifications are necessary. The fan systems are rated at 156 cfm each for a total of 312 cfm. This probably translates into 220 to 270 cfm for the completed Corsi-Rosenthal box – which means that two in the average classroom would provide 5-6 air changes per hour (ACH). The noise of the finished unit with two fan systems is about 40 dBa. (You can hardly hear it.) They take up a small footprint and use just 10 Watts of electricity. In short, it is pretty impressive air cleaner.