um. well if your heating it correctly, then all your really doing is boiling the alcohol with the weed in it to get the extraction quicker. so really it should be a closed system, in which the boiled alcohol isnt changed, just condensates, and is reboiled. You have to use the correct alcohol. it can only be ethanol if drank. all the other alcohols can cause a horrible array of issues in your body. including rubbing alcohol which is really a mixture of ethanol and methanol so that it becomes a dangerous substance to drink normally.