I had Kevin (with The Lee Thompson Co) install three UV lights installed in my HVAC at the A-coil (one on inlet and two on outlet of A-coil) along with a ("REME HALO® Whole Home In-Duct Air Purifier" which greatly improved HVAC air filter dust collection)...installed December, 2019.
My home is now my haven for purified clean air. And I know this because when I go to other buildings, I immediately notice that my sinuses react to bad air. Wen I return home, my sinuses clear up. As far as allergy colds, they have basically gone away...where I used to have an allergy cold/infection several time per year and now one year after UV installation, not allergy colds/infections.
One note is that I have had to clean floors more because of the "REME HALO® Whole Home In-Duct Air Purifier" causes dust particles to clump together and get caught on HVAC air filter and fall to floor.....better on the air filter and floors than up my nose and in my lungs.
And with this COVID (flu) virus, the UV lights kill virus and bacteria.
I highly recommend UV lights and the REME HALO® Whole Home In-Duct Air Purifier and The Lee Thompson Company and Kevin the installer.