I don't know the exact set up of the brooder - but make sure rats cannot get at it. WE normally have our chicks in the spare bedroom until they start to smell, and then in the garden shed with the box sitting on an empty cable reel (not a massive one) and it is bigger so extends over the top of the reel. So far not had rats getting in, but we also have a wire mesh dome sitting on top, so no access really.