Apt. starting to smell like pee!

I had no clue where to post this... hopefully its ok to put it in this section. Anyways, I've been noticing that lately, my apt. has been smelling like cat pee! I only have my one cat, and Andie would never pee outside of her litter box. I clean it out and use the cat litter deodorizer. But its getting very smelly... Anyone have a good suggestion as to how to get rid of the smell???