Question: We have a 6 year old wood-burning fireplace which has been well maintained by having the "chimney man" clean it annually for the past three years (Before that- there was a previous home owner). The brick design includes the main firebox- and two side "heatilator" opening with a pair of lower intake and upper outflow vents made of brick. We also use a glass door which is usually kept closed- although there are several small circular holes below which are kept open. After burning a mixture of hard and soft woods (dry) for about a hour- a smell builds up in the room and the upper levels of our home. The heatilator sections put out the smell. The main fire box which hardly smells at all. After 1-2 hours- it smells like MASKING TAPE GLUE ! 2. I temporarily sealed the heatilator vents with aluminum foil and that did reduce but not eliminate the smell. Of course- I don't want to have a bricklayer come in and seal up the vents permanently .This is so bad that we had to skip using it during our Christmas and new Year's holidays this year. Answer: 1. I can only guess that insulation has been put in the wall against the fireplace and it starts outgassing when a certain temperature is hit. 2. Sealing the vents is dangerous as this cools the fireplace.My advice would normally be to burn the fireplace very hot for a long period of time with the doors and windows open. This would burn off any odors- etc. However- this does not take into consideration that the fireplace may have been installed incorrectly- and the smell may be burning of building material too close to the fireplace. In this case- burning this hot could cause a house fire ! From afar- that's all I can say. <p>You should definitely have a pro look at this one!