Even though they don't make any smoke or smell at all when up to speed and running, a gasifier (mine anyway) will smoke like an OWB during the 10 or 15-minute startup period. Even after you close the bypass damper and turn on the fan, it will smoke for awhile until the gasification chamber gets up to temp and the nozzles light off. I've been thinking, more out of idle curiosity than anything else, about how you could minimize the smoke on startup. So this morning I took 8 pieces of commercial charcoal and placed them on my two nozzles. Eight pieces--four to a nozzle, covers the nozzle openings in the firebox. I started a small paper fire with a couple of pinecones bark and let it burn for awhile. Then I stuck a few small pieces wood in there, closed the bypass damper and kicked on the fan. It smoked for a short while and then went clear. A lot faster than usual. I haven't used the boiler enough to have a bed of unburned coals accumulate on the nozzles, but I suspect you'd see a similar result with that. As somebody pointed out, successful gasification is all about having a good bed of coals. Lacking that, charcoal seems to work pretty well. Nice to have on hand.