Yes, the furnace filter taped to the box fan is fairly good. Low speed only, I would say. Also, like any filter, you’ll need one that is rated for smoke. generally, the smaller the particles that it filters, for this purpose, the better. But also the more expensive.
MRNA reacting to blood in real time.
https://truthsocial.com/users/garystephen4321/statuses/110962335217953132
“Yes, the furnace filter taped to the box fan is fairly good. Low speed only, I would say. Also, like any filter, you’ll need one that is rated for smoke.”
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Good points!
For reference, furnace and central air system return air filters are MERV rated, rather than HEPA rated. HEPA 13 is “hospital” grade filtration fineness. The equivalent in a MERV rated furnace or central air filter replacement cartridge would be a MERV 16 filter.
These types of furnace/return air filters typically do not remove volitile organic compounds due to their lack of a carbon filter material layer, but you can add a layer of carbon filtration to an ad-hoc box fan air filter with a sheet or sheets of carbon filter material (available for window mounted air conditioners), between the filter cartridge and the box fan.
While you’re at it, place a little something between the fan motor and the filter material to lift it a bit allowing airflow colling to the box fan motor.
~Easy