If I leave a few lit candles in my fermentation chamber (chest freezer,) would it eat up all the oxygen without any adverse effects? I've seen people do this on a smaller scale but it creates a vacuum. My suspicion is, if the beer is still producing gas, the amount of vacuum won't exceed the produced CO2
If you are fermenting in a chest freezer, I don't think oxygen will be a problem for you. Just after you pitch, you want as much oxygen you can get in solution. When fermentation begins in earnest, the produced CO2 will displace not only the oxygen in the carboy/bucket, but also in the chest freezer. In my freezer, I have to be very careful not to stick my head in there during fermentation because of the lack of oxygen, and certainly any candles in there will snuff out early.
I always used to like to smell the fermentation, which was easy to do when I didn't have the freezer. Part way through my first fermentation with the freezer, I stuck my head in to take a whiff and got a lungful of CO2 which burned my throat and knocked me back; that's when I had my forehead-slapping moment and realized what an idiot I had just been.