Didn’t the Apollo 13 crew make an air scrubber out of duct tape and hope? Surely a cardboard box, a box fan and a hepa filter covered in tape gets you 90% there
You are referring to a Corsi–Rosenthal Box. You are correct that they will get you 90% of the way there, but they also tend to be large, loud, and ugly. We can build better things now that we have time and resources.
This was done during COVID and made international news.