Careful or not, my guess is that he smelled you and not the thermocell. The thermocell does give off the very slightest of a scent, but I believe it's gone before it gets close to the ground. May sound silly, but I think the scent from a human is "heavier" if you will...than that from a thermocell and more likely to make it to the ground.
Could be too that he got some scent from you when you walked in and mistakenly touched a tree or branch.
ORIGINAL: ffmike
Has anyone who uses a thermocell ever ben busted by an animal. I thought they were sent free. I was in Canada last week bear hunting and decided to use my thermocell (first time using it) because themesquiteos could have carried me away.After it warmed up I could smell it, but I decided to keep it runnining and give it more time. I wish I had'nt. I had a mature bear, around the 350-400lbs range walk within 10ft of my stand downwind. I watched him lift his head and smell the air and then turn around and walk back the way he came. It could have been me that he smelled but I doubt it, I am very careful about controlling my sent. I was just curious if anyone has hadsimilar experiences using the thermocell.