Expert: James Ball - 9/29/2008

Question
QUESTION: I have a fireplace that has a small smoke problem. After starting a fire (which drafts almost instantly) I will close the glass doors after it gets going. BUT, when I open the doors to stoke or add to the fire I get a small curl of smoke out the top of the doors. When they are closed you can see the smoke curling around under the lintel just waiting to come in. If the doors are left open for the whole time I have no issues with smoke. Everything heads right up the chimney. It's just when I have any type of fire going and close the doors that I start to see the smoke hanging around in the firebox. I've tried a smoke guard, but it still makes it's way under that when doors are opened. My father used the fireplace years ago and never had a problem, but If I recall correctly, he never burned with the doors closed. Here are some dimensions if you need to know...flue 12"x12"...fireplace opening 37"x22" (with doors open). Doors also have a small grate that can be open or shut on bottom. Any suggestions would be greatly appreciated.

ANSWER: Hello Walt, it sounds like a negative pressure issue that is where the house is a better chimney than your chimney. It can come from air rising in the house, exhaust fans, even the furnace turning on.if the some is coming back into the house then find out where the air is going? Up the stairs?an other option is to open a window/door to relieve the pressure before opening the glass doors.
hope this helped
James Ball

---------- FOLLOW-UP ----------

QUESTION: Thanks James. I guess I need you to know a little more of the details. We have windows right by the fireplace that we kept open to see if it was negative pressure problem and that doesn't seem to be it. Also the fireplace is in a single room addition(13x28) to the house which is closed off from the rest of the house by exterior entry door (sealed good). Can it have to do with the fact that when the doors are closed the flue acts as if it is to big causing a loss of draft? Remember that it drafts fine if the doors are left open even when the windows are shut.

Answer
Welcome back Walt, this makes more sence, when the glass doors are open it works fine, when closed and then opened you get smoke. it sounds like you need to open the damper on the bottom (and top if so equipped) to allow a flow of air into the firebox. it sounds like it is choking it self off until you open the doors then it has to restart its draft again. try starting a fire, then slowly closing the doors until they are fully closed then (making sure the glass door damper is open on the bottom "shine a light through from the back") then start opening the doors maybe 1 inch at a time every 20 seconds and see what happens.
It might be trail and error until you get it right.
hope this time it helps
James