Any cat owner can say that the cat box is perhaps the smelliest place in their home. The cat box is essentially a cat toilet, and even a human toilet does not smell pleasant if not cleaned regularly. It just so happens that a cat box tends to get dirtier faster, and the speed can vary depending on the number of cats within the household.
While some companies that sell cat litter are attempting to rectify the problem of cat odor by adding fragrance ingredients to the litter itself, these scents are not always strong enough to mask the odors. Along with fragrances used to scent the litter itself, there are also sprays that can be used in the air to help mask odors while the cat box is changed or after it has been changed.