I use to live in a one bedroom apt and bred rats. I also kept some for pets. I cleaned everyone once or twice a week. My apt didn't smell, in fact I had people tell me that they wouldn't know I had any animals (by the smell) if they didn't see them. And I kept the rats in the living room, by the door. Can they smell? Sure. But it depends on how many you have and how often you clean them. Also what you feed them. I find they smell less eating rodent blocks then dog food.