Neat idea however air filter changes would be extremely expensive as its about 5x the air filters of a conventional purifier - which already seem to cost around 50-100 dollars to replace.
The filters are MERV-14, not HEPA, so they're much cheaper ("materials for one fan are nine MERV-14 filters for $110"). See https://www.jefftk.com/p/merv-filters-for-covid for why MERV-14.