No they don’t, at least not dwarfs. I was worried about this as well but I have 2 tanks in my medium/small room with 1 window and there is no smell. I clean the tanks weekly but they could definitely go longer. Chicharrón grooms very often and smells clean and fresh always. Wood bedding is bad for hammies and smells like pet shop, I use paper bedding which I recomend, they also enjoy burrowing in it more.