Expert: James Ball - 10/29/2011

Question
Hi James,

I have a double-sided fireplace on ground floor level w/ fireplace directly below in the basement.  With damper closed in basement, every time I use fireplace upstairs, I get just enough smoke to set off a nearby fire alarm (20-ft away) after about 1-1.5-hr, watery eyes ensue shortly thereafter.  I am using wood several years old that exerts a bit of white]gray smoke by-product  Do you think I need a professional to check for leaks?

your advice is appreciated,

Jeff

Answer
Hello Jeff, if the smoke is coming down the un used fireplace flue in the same chimney then you have a "negative pressure issue, you can read and search about it on other net, basically if 10 gallons of air go up the chimney  then 10 gallons of air has to come from the house, if the house is air tight then it will pull that air from another chimney next to it.
top mount damper might help stop it from coming down. CSIA.org you can find a certified sweep that can help.
James