If the deer are close enough to get a whiff of your heater..... you're already busted anyway! LOL! Don't worry about it. We use portable Mr. Heater propane buddy heaters in our blinds and they work great.
An "archer" tries to see how far away he can get from his target and still connect, a BOWHUNTER tries to see how CLOSE he can get to his!
Never used one in a ladder stand, but used to keep an open flame in my bigger shooting houses. Used a metal can with sand in it and rubbing alcohol for fuel. Just poured it in and lit it. It burns real clean and makes heat without much visible flame or odor. Just gotta be careful and remember there is a flame there, and cap it so it goes out when you leave. I had a larger can for a cap and then when you know its out you put the plastic cap on when it's cool enough, so your alcohol doesn't evaporate.