Hey, is that easy to do, filling 16 oz propane canisters from a 20 pound tank ? I'll have to look into that, I didn't know you could do that ..
Check out some of these options for space heaters, they are catalytic heaters and can be used in tents, campers, even indoors probably with very little ventilation. You may doubt that, but it's absolutely true, they only can put out maybe 8,000 BTU however.
The only thing is they can gum up and you can't leave a canister plugged into them when turned off, or if they are connected to a tank, the tank pressure has to be turned off when the heater is off. If anyone knows an easy way to ungum these things, let me know as the one I've used for the past few years is gummed up.
http://www.mrheater.com/productdetails_extended.asp?catid=41&id=24This is a newer one that has a fan that runs on D batteries, the fan should distribute the heated air better, I've though of getting one of these which might be good for camping at campgrounds where this is no electrical plug in. They claim this one can put out 18,000 BTU:
http://www.mrheater.com/productdetails_extended.asp?catid=41&id=116This is a great little heater, but only puts out 3,000 BTU, you don't have to disconnect the cannister when it is shut off, and it doesn't seem to gum up after a few years of use like the other ones:
http://www.coleman.com/coleman/colemancom/detail.asp?product_id=5038A800&categoryid=3000I have an older one of these black cat heaters, I've used them in the winter when I go surfing. I park my pop up truck camper at the beach with the top up, then after I get out of the frigid water I go inside the camper, fire up the heater, make some hot tea on the stove, and by then it's plenty warm enough to take my wet suit off.
They are great for cold weather camping also, but as they are only 3,000 BTU, not really great for winter (up here in New England) except in a pinch.