And this is how our well managed, clean burning fire should look. A respectable mound of coke at the center with green coal all around. The center of the fire should be hot and clean with very little smoke. The outside edges will generate wisps of sulfurous smoke as the coal is converted into coke, but it should not be belching huge amounts of thick smoke into the air. The heat of the fires core will be enough to convert the coal to coke, open flames are not necessary.