I remember watching a Mythbusters episode on scent control using a dog (bloodhound iirc) that found them out every time easily if the trail was less than several hours old. Deer noses are supposedly better than dogs. I quit thinking much about scent control after that but MUCH more on how wind, temps, thermals etc effect my sent. I bet human breath is pretty easy to figure out as danger but not many (any?) scent killers are considered good mouth wash. If I can smell human breath I think a deer would have no problem. I think of my chosen stand as being a stink bomb and hunt accordingly.