When I was a kid I used to sit with my Grandpa before I was 14 and old enough to legally hunt. We always sat in a natural ground blind, no roof, and in the U.P. it could be as cold as a mother-in-laws kiss. We used to sit dark to dark. One time I was freezing, I mean I thought I was gonna freeze to death before it was over. Around noon he built a small fire to warm me up, himself too I expect. At first I protested, I asked him if that would spook the deer? All he said was "don't worry about that, just keep your eyes open while I finish this." We shot a nice buck a half hour later. The wind was swirling bad that day, I could see the smoke changing direction every few minutes. That buck could have cared less. He told me later he used to start a small fire all the time when it was that cold, and it never bothered the deer one little bit, not even the bruisers. That was back in the days of red plaid wool, always a fire burning in camp, and those guys never changed before going out. They wore their red plaid hunting pants all day around the fire too. If I was gonna worry about cover scent, I would hang my clothes near a wood fire. No clue how much it might help, but I know it won't hurt.