Since I have 7 cats, I bought 2 air purifiers (Holmes) that also have ionizers. This purifies the air. When you walk into my apartment you don't even know I have cats except that they greet you at the door. I would highly recommend getting one. They're fairly inexpensive (about $39.00 each) and the filters last a while.

My Sphynx MooShoo has this awful habit of not covering his poops and when he goes, you know it!