I researched some before we purchased our air purifier (which I wrote about in the other thread that's here). Anyway, we bought one that uses a hepa filter, and then we bought a "VOC replacement filter" that supposedly has a longer life than changing the regular filter... Anyway, it is a hepa filter and the machine is by Amaircare. You can find them on google. about the ozone, I was concerned about that which is why I decided to go with an air purifier as opposed to an ionizer. I read testimonies by some folks with asthma/allergies who got worse by using the ionic breeze ionizer. However, I know the amount of ozone put out by an ionizer varies with each company.
The salesman we purchased from said that ozone isn't good to mess with and that all electronic things put out a certain amount of ozone already, so why add to it by getting a machine that also did the same? However, I also know of a local health store that seem to have done their research also, and they sell ionizers that they rave about and have very little if any ozone giving off the machines.
So really, I think that said, the best is to contact different companies by phone or e-mail aobut their products and then see.
The reason we bought the amaircare is because I used to be friends with a gal who has had significant issues with allergies and she is a holistic nutritionist also, and she had tested the air purifiers by this company and highly recommends them.
all the best, manyembers