HEPA filters, such as the ones in air purifiers, are 99% efficient at removing virus particles from the air. However, such filters cannot simply replace the one-inch filters you may have in your furnaces or other fan-forced heating units. Reason? They are TOO good, have TOO much resistance to the flow of air, and will mess up your heating unit, possibly making it hazardous.
The safe and partly-effective thing to do is to replace your standard one- or two-inch filter with a "MERV-13” filter. Just slide out the old one, slide in the new MERV-13 filter, and you will get around 40% efficiency at virus removal - and only a little extra pressure drop, so that your unit will probably work just fine. They’re also great for wood smoke and air contaminants from pets and other sources. Just remember that you will need to replace a MERV-13 filter more often than you are used to, something like twice as often.
MERV-13 filters became instantly popular last year in the early months of the pandemic, and were completely sold out for quite a while. Now they are readily available, if not at your local hardware store, then from many online sources.
Not to promote Amazon, and we’re not getting any commission, but this is what we use at our office.
https://www.amazon.com/gp/product/B01CR9K33K/ref=ppx_yo_dt_b_asin_title_o01_s00?ie=UTF8&th=1
