There are a few ways you can keep your cat’s litter box odor-free:  Place your cat’s litter box in a well-ventilated area so any stinky smells from the box can dissipate with the help of a breeze.  Scoop out urine and poop at least daily or every other day if you use a clumping litter. For non-clumping litter, you’ll have to throw out the litter containing absorbed urine and poop; scrub, wash, and dry the litter box; and place fresh litter in the dry box.  Have one litter box in use for each cat and one extra. So if you have three cats, then you need four litter boxes.  Use two litter boxes in rotation so you can use a spare as you thoroughly clean and dry the other one.  Baking soda helps absorb litter box smells. Either sprinkle some baking soda in the litter box before you add the litter or place an opened box of baking soda near the litter box.  Use an enzyme-based cleaner if your cat has a potty accident, i.e., doesn’t urinate or poop inside their litter box.  Replace the litter box yearly.