My first questin is: do you run a welder, grinder, or a torch? Now with that asked, I have seen many more fires started by those three things than I have ever seen by a forge in my 8 years of blacksmithing. If your worried about sparks comming from the chimny... then put a spark arrestor on it. Second... will you insurance company accept a "Coal Furnace" or "Coal Firepalce" without canceling you? If they don't then to heck with them. Just use common sence while smithing... and keep watter or a fire extinguisher on hand.