I mean, HVAC systems are supposed to remain usable for 20+ years, it's not really something you can throw on a production line in a matter of days. Most likely, someone already is working on such a system.

They already exist, i saw a video on hvac systems used in a moroccan pop-up hospital, air coming in or leaving the building goes through filtration and then through a désinfection machine. They didn't explain the method used though.

I'd guess a strong UV-C light would kill the virus pretty reliably.

Normal HEPA filters can stop the virus: https://thewirecutter.com/blog/can-hepa-air-purifiers-captur...

Hospitals have had such systems for decades: Negative pressure rooms make sure that the bad air goes out through an exhaust that you can clean or at least keep well away from people. Some cars have HEPA filters, and airplanes often have more sophisticated systems than that.

There should be. There are a few options. UV-C in the air handlers seems like the easiest retrofit but I’m not sure how effective it is.