Hello all, new to the forum. I occasionally have a problem with back puffing. I have a wood furnace with automatic draft that is controlled with a thermostat upstairs. The furnace is very tight, holds great all night long even on the coldest of nights. The problem seems to occur when the draft opens when the thermostat is calling for heat, it gets burning hot, blower kicks on, heats the house to the setpoint of the thermostat and then the automatic draft closes. Then I get this blow back of smoke that blows the draft door open and couple times and blows smoke out the pipe joints! What can I do to correct this?? Would putting some air across the top of the firebox help? I do have a slide gate I can open on the feed door. The draft is on the clean out door. Thank for any help!