This is maybe the fourth or fifth time I've used this same gas tank to make heater for my workshop, it's been cut, welded and patched up numerous times. Hence it's very ugly.
Basically it's a simple rocket with an extra large horizontal fire box, a pipe running over the "Mouth of the Dragon" which connects to a blower. The rocket exhaust exits into a 200l oil barrel and from there it exits the shop via a very thin, aluminium (aloooominum) foil air duct.
Top of stove reaches about 400c, the barrel heat exchanger type thing reaches about 100c and the exhaust leaving the room is only about 30c. Nice!
The blower blows out air that's heated to about 70c and it's nice and cosy.