We have a 1973 home that has two wood burning fireplaces. We sealed the lower fireplace at the top because the basement was not finished. We used the upper fireplace and it worked great. We now have a finished basement and I had a chimney sweep come out and open the lower fireplace. Both fireplaces have top dampers. Problem is we get smoke in lower room through lower fireplace. I originally thought it was a negative pressure situation but had an HVAC guy install 6 inch cold air intake. Doesnt seem to help. I have tried opening windows on both and either level. Doesnt seem to help. Advice would be great. I am new to posting.