I don’t know how they do it. It has to be witchcraft. We haven’t changed litter in two weeks and can’t smell a thing. We moved into a new house and had a small area we could put the cat box so we put it in the basement laundry room next to our kids play room and we could smell it within a week. The traditional litter smell and cat waste smell filled the area. So switched over from an automatic cleaning traditional litter box to this trying to do anything to fix the problem. Well, problem solved! It has been two weeks and we haven’t even done anything with it because the directions said to let it go for a while. We can’t smell a thing. All of the waste just gets swept under the cover and you don’t see it, or smell it. We are very happy with it.