Years ago my father in law had a home made heater in his shed which consisted of a possibly 20to30 gallon drum opened at one end with a tube down the centre of it he then stuffed sawdust between the outer edge of the tube and the inside of the drum when it was stuffed firmly the tube was removed and a fire was lit at the bottom it seemed to burn slowly and safely what I dont know is how do construct it properly should there be a hatch in it at the bottom or air holes does anyone know it seemed more of a constant smoulder than an all out fire cheers