The key to maintaining cleanliness and hygiene when keeping cats in an apartment is:
First, choose a disinfectant that is harmless to pets, such as a food-grade disinfectant, and regularly clean your cat's supplies and living environment.
Second, clean the litter box promptly: clean the litter box daily, change the litter weekly, and keep the room odor-free.

Third, regularly bathe and deworm your cat: keep your cat's fur clean and reduce parasites.
Fourth, maintain ventilation and cleanliness: open windows frequently for ventilation and clean regularly to reduce dust and bacteria growth.
By following the above points, you can ensure that keeping cats in an apartment building is clean and hygienic.