I had a litterbox in my closet a while back. I took the cover off so it would fit. Well, that was a big mistake. Doogie, who is a BIG boy, over compensated and missed the box when he peed. When I rearranged my boxes again, I noticed the closet floor smelled of kitty pee. I scrubbed it with bleach and sprayed it with Nok-Out. The odor is now gone, but I've relocated the boxes back into the "kitty room", with the covers.

My towels and sheets were on the shelves above the box and none of them absorbed the odor.

Don't let my experience discourage you though. Every case is different.