I am so sorry for your loss. We use large barrels that fits at least 3-4 medium to large ferrets and have no trouble, but we do keep them in a room that never goes above 69 degrees. I know you feel guilty, but no one is omniscient and if your ferret was elderly and ailing, he may just have wanted a warm, dark place to cross the bridge. I would urge you to consider larger barrels, but even they get rather warm. I think that is one of the reasons ferrets like them. I feels like being in a pile with a bunch of other hot-blooded ferrets. Please do not beat yourself up over your ferret. Remember you gave him love, care and shelter. It may just have been his time to go. Best wishes, PJ Weber [Posted in FML 7517]