We have been using alcohol and toilet paper heaters in our box blinds for years, they work great. Just get you a old gallon coffee can with a lid on it. Put a double roll of toilet paper down inside it, then pour a bottle of rubbing alcohol over the roll of toilet paper and light it when ur in ur stand. This will give off more than enough heat for a enclosed box blind. Then when your done hunting for the morning, just snap the lid down on it to extingish the flame, until your ready to hunt again. All you have to do is relight it the next time you hunt. This is a very cheap way to stay warm on those cold and damp days.