I currently have a wood/oil combination forced air furnace. Practical new furnace with house not a year old. When I am burning wood I get a smell of smoke through the entire house minus the furnace room which in the basement of a bungalow. There is no visible cracks in the heat exchanger. I am wondering does it have some thing to do with negative pressure. Chimney is all up to spec and the furnace has great draft with the door being open. Can to much draft or the return air cause negative pressure. Thanks for some input.