Sarah: I also saw that a lot of these UV systems are coupled with mechanisms that release ozone into the air, although according to the article I linked, it is possible to find one that does NOT do that (if someone were to want one). And you are right, ozone releasing would be terrible for respiratory patients.
Sonia, you know when I was reading the article, I saw how UV is used to effectively kill bacteria, mold, etc., but I'm guessing that you came to the same conclusion that I did -- it didn't seem to make that much of a difference when it came to the air in a room.
I suppose a similar thing would be is that the company that supplies my tap water uses UV (in part)to disinfect the water. But if you use a meter which measures the bacterial count, it was "average". Which isn't great. I asked the water company about this. The answer?
When it leaves their plant, it's clean. But traveling through the pipes -- it picks up bacteria. The water guy told me he uses filters on his own tap.
I use a Hepa/Charcoal filter that my doctor recommended to me. She likes this company because it specifically addresses people with chemical sensitivities. There are no glues or chemicals used in its assembly.
You can get it online. It's a Canadian company called Aller Air. I got the 5000 model for about $500 plus pre-filters about six years ago. It is for a house about 1500 sq. feet. A friend of mine just got one which is a better model -- it has more charcoal, additional filters and is the model that is for multiply chemically sensitive people. If I were buying now, I would get that one.
My friend said he was able to find it a discount, around for what I paid. I can ask him what the website is. He has asthma/chemical sensitivities and has just started to make changes. He said with encasing his pillow/new HEPA vacuum and the air filter, he can breathe out of his nose for the first time in the morning when he wakes up. So for him, he was happy to see some improvement. Everything in combination helps.
So start by looking at the Aller Air website. Then search for a better price. I remember the HEPA filter are for 5 years. And the smaller filters are changed more often -- but not too expensive.