I don't think I was the only one, though. HD was doing a brisk trade in 20x20 filters, and I think I bought the last box fan at any Target in the entire bay area.
My "creation": https://i.imgur.com/jeJfqeW.jpg
Get some 120mm fans (or an array of 80mm, etc), and some engine air filters.
Don't change the filters too often:
"It is common, however, for servicing to occur when the filter appears dirty. Engine air filters are designed to actually increase their efficiency by using this initial layer of dust as an added filter layer. Initial filter efficiency is usually approximately 98% but increases to more than 99% by the end of the service life of the filter.
Therefore, changing an air filter before the useful service life is achieved can result in premature engine wear."
https://www.fueleconomy.gov/feg/pdfs/Air_Filter_Effects_02_2...
I've been begging for a good use of old computer fans...
Thank you for bringing this up ... in industrial settings, filters are "seasoned" for some period before they can be expected to perform at their published ratings.
Many air and water filters' performance continues to rise over their lifetime - the downside being decreased flow rate.
If you are filtering infectious agents with a water filter, I would be reluctant to run them past their lifetime because you could have things living in the filter and filter housing, etc., but if you're just dealing with particles, your filtration should continue rising over time.
Is that the spot of use as well? I’d imagine the vicinity of the wall would limit the airflow.
There's often an electrostatic component that ties into a filter's efficacy, as well.
I still have a sore throat, but I also have to go outside a lot, so maybe that's not surprising.