Q: Jason, I have 2 fireplaces, one below the other. There are 2 flues up the same chimney. The one in the basement has no damper and needs some work before it can be used, so we put a piece of concrete board over it and a bookcase to hold it in place to block the opening. Obviously, it wasn’t a perfect seal, but it was pretty covered.

We noticed though that when we used the upstairs fireplace smoke would come into the basement room. We want to use the upstairs fireplace this winter but aren’t ready to make a full decision on what to do with the basement fireplace. Would the Chimney Balloon be a good stop-gap solution until we decide whether to just block this fireplace off permanently or fix it? – MB

A: Dear MB, What you are referring to is called “smoke crossover” it happens when you have two chimneys close to each other and one is breathing out smoke while the other is breathing in outside air to equalize air pressure in the house. Here is a link to an article and a picture diagram of the issue. http://www.chimneyballoonusa.com/blog/2008/05/can-two-firepla.html

The Chimney Balloon is used regularly buy chimney sweeps and homeowners to correct smoke crossover issues. If you use a Chimney Balloon to seal the basement fireplace chimney it will force the house to find another path to draw air in from other than the basement chimney flue. This, therefore, eliminates the smoke being drawn back into the house.

You can use the Chimney Balloon as a temporary or permanent solution to this chimney smoke crossover issue. The Chimney Balloon will function as your damper once it is installed so there will be no need to do anything with the old metal damper. So you can save the rest of the chimney funds to hit the other projects on the old honey-do list. – Jason