There's quite a controversy going on about ozone/ion air purifiers. They generate ozone for odor control. From what I've read, it doesn't actually eliminate the odor, but deadens your sense of smell. The ozone generated can harm the linings of your lungs, and exacerbate asthma. I can't say for sure that this is the last word on them, but one of the articles I read was from the California EPA, so I'm a bit wary of them thus far. I didn't know any of this, but I was researching air purifiers because since it's been so hot, and I've had to close the windows and run the a/c, my kitten room has been smelling very...um..."kitteny".
I've found no good solution so far.