Just be careful about purifiers with ionizers, and make sure its optional if it has one (most do). Some ionizers can cause ozone build up, google on it if you want. It MAY be harmful to both humans, critters and birds.
I am in the market for a purifier as well, came across this during my reseach. Honeywell seems to have ionizers on all their models (or close to all) but it's optional on a few of those models. Be sure to read up! On the smallest tower it isnt optional to give an example.
I am also looking into bionaire, which has a couple of models with permanent filters and optional ionizers. Personally, I am a long way from making a decision though...
Stitch (WFA) and Leroy (BWP)