Update: My old coal forge in the garage was smoking out the whole neighborhood.
Got desperate and tried a trick from a guy at the Portland forge-in. He said to soak a burlap sack in water and drape it over the back of the hood. Did it last Tuesday, and the smoke just vanished. Anyone know other cheap ways to control forge smoke without a huge exhaust fan?
Hold on, isn't that just hiding the problem? A wet sack is a fire hazard waiting to happen. You're better off fixing the real issue with proper airflow.