Now that we know COVID is spread via aerosol rather than fomites, having clean air is of more concern than clean hands. Automaker Ford, working together with fan manufacturer Lasko, is addressing this with their design of a simple air filtration system centered on a common box fan.
The design stemmed from research conducted "using supercomputer air flow analysis to determine if a low-cost box fan air cleaner can mitigate the risk of airborne transmission of COVID-19 in a classroom equipped with a single horizontal unit ventilator."
"The study found that box fan air cleaners like this can serve as an effective low-cost alternative for mitigating airborne transmission risks in poorly ventilated spaces."
Ford and Lasko's inexpensive fix is simply a cardboard cutout that supports an ordinary air filter (they're recommending MERV 13 or higher, so it looks like you don't have to go full HEPA) and attaches to a box fan.