air filter recommendation

Can anyone recommend a good air cleaner/filter for removing litter box
smell?

Background: I have two cats and one of them refuses to cover her
"deposits" in the box. I clean the box twice a day and one of the
cats refuses to use a littermaid automatic box. Hence, I have litter
box smell between cleanings.

I've been told that the Ionic Breeze air cleaner is good for this type
of application. anyone have any experience with this? Any other
recommendations?

Thanks!
S