The single filter version did very well vs commercial air cleaners.
Here’s what the final build can look like with judicious use of duct tape. Pretty, pretty sharp:
Here are the actual measurements:
Here’s the actual build from the above Twitter thread.
Here’s a more simple, slightly less effective single filter build by aerosol scientist, Dr. Huffman.
And here’s a single filter build, but with a 4″ filter. It should be very close to the 4 filter Corsi/Rosenthal Box in performance.
No matter which build you do – make sure you put a shroud on the front of the fan to enhance efficiency.
With the single filter build, if you have 3 of them – you are going to have great results – over 6 ACH in a classroom:
One last option shown below
Won’t be as good – but something is better than nothing!
You could make that something even better by replacing the MERV 10 filter it comes with, with a MERV 13-A filter.