The family on duty at any given moment is responsible for the cleanliness of the common spaces. This would normally mean that the members of that family sweep the hall, the entryway, and the kitchen every day or once every few days, and that they would have to mop those spaces with a wet rag at least once a week, and clean the washroom
and the lavatories by scouring the sink, the bathtub, and the toilet. Until the end of the 1980s, it was the responsibility of those on duty to take the apartment's garbage out to the trash-bin in the courtyard.
The length of time on duty depends on the size of the family. If there are three people living in your room, then you have to be on duty for three weeks in a row; if you live alone then you’re on duty for one week. Usually the duty roster hangs in the kitchen. It follows the order of the rooms in the apartment, but neighbors can in principle decide on any sequence that suits them. In the last few years (this is written in 2007) many residents, especially temporary ones, prefer to pay one of the other neighbors to cover for them.
The person on duty often gets involved in conflict. This may mean starting a fight with someone who has made a mess that has to be cleaned up, or having the neighbors demand the apartment be completely cleaned to their highest specifications.
Ilya tells about cleaning the apartment in the clip "Who Pays and Cleans" from Tour 2.