Wood burning furnaces have been extensively used throughout the northern tier of the United States of America to heat buildings. Many of these outdoor wood burning furnaces include a heat conduit for conducting the heated air or heated radiated liquids to an externally disposed house from the wood burning furnace. An outdoor wood furnace is typically equipped with a wood burning fire box or furnace chamber within which the solid combustible fuels are burned, a fire box door for providing access to the furnace chamber, a chimney for exiting smoke laden gases from the furnace chamber, a heat conduit for conducting heat to the building to be heated, and a furnace fan which provides sufficient air to fan the combustible fuels within the fire box. In a normal operation, the fan is typically engaged during the combustion of the solid combustible fuel material. Most outdoor furnaces are also equipped with a furnace fan switching mechanism which stops the furnace fan upon opening the fire box door. Since the furnace fan typically blows the smoke laden gases out the chimney, the disengagement of the furnace fan tends to create a considerable amount of entrapped smoke within the fire box. Thus, when the furnace door is open, a large amount of smoke laden gases usually expels through the open furnace door rather than exiting through the furnace chimney. Consequently, the tender or operator of a wood furnace often reeks with smoke laden clothing and sometimes chokes due to the smoke laden fumes escaping from the furnace door. This typically happens on those occasions when it becomes necessary to refuel the furnace box with wood. It would be extremely desirable if there existed a smoke arresting system which would prevent the accumulation of smoke laden gases within the furnace box when the furnace fan has been disengaged for purposes of allowing access to the furnace box. This would permit the furnace tender to open the furnace box door without being bombarded with bottled-up smoke.